texts: PCB Assembly: Specifying Jumper Configuration For Assembly House

texts:
I want to send a board off for fab + assembly soon which will include various jumpers in 2 or 3 pin configurations. For example, see this picture below (sorry about quality). I'd like to specify the 2P header to have a jumper installed, and for the 3P header, the jumper is installed on pins 1-2.

Is there any standard way of specifying this in either the BOM, Gerbers, or elsewhere? At prototype levels I can install them myself but at production this is infeasible. I'm sure worst case I can include a readme file with assembly notes.


texts: Source Transformation of dependent sources

texts:
Would it be correct to use use source transformation on a dependent source. For example, would it be legal to turn a voltage dependent voltage source in series with a resistor, into a voltage dependent current source, in parallel with the resistor? Does the regular application of Ohm's law apply.

I've looked around the internet and can't seem to find any definite answers.


texts: unclean signal at the output of an optocoupler

texts:
I use a FOD260L optocoupler and here is its datasheet and diagram below

pin 2 is connected to an atmega168a (supplied by 3.3V ) via 270 ohm resistor. pin 3 is connected to ground of the MCU. On the right side, Vcc is connected to a PSU that supplies 5V (max 1.5A), Ve is left opened, pin 5 is connected to GND of the PSU. Referring the figure 11 on the datasheet, I connected 330 ohm between Vcc and Vo (as a pull up resistor) then I expect monitor Vo output. I tried to draw the schematic below ( I hope it is correct).

simulate this circuit – Schematic created using CircuitLab

Here is the oscilloscope output

The blue one is the input signal which is clean, and the red one is the output (Vo) signal which I could not understand why it is not clean. Of course I connect blue's probe ground to MCU's ground and the red one's probe to the PSU's ground. PSU and MCU have different power sources.

I see that the red signal is inverted which I expected to see. But could anyone explain why it is not as clean as the blue one?


texts: Trace width specification in PCB land pattern detail

texts:
I came across this figure in the datasheet for an accelerometer. It gives a very specific trace width (0.15mm) to escape from the pad, as well as a minimum length (0.5mm) at that width. So far, the only explanation I can come up with is thermal considerations during soldering - the thin trace will conduct less heat away from the pad.

Is that it or is there another reason for this very specific trace dimension recommendation?


texts: LTSpice error with the V() function in a subcircuit

texts:
I'm trying to do a simulation with a subcircuit, and I've narrowed down the issue to the V() function.

The simulation fails with the message 'can't find definition of model "V" '

Here is the spice library with the subckt (RXD_33_2_TYP)
(The library was from an IBIS model converted to SPICE using microcap)

test.lib to troubleshoot issue

Original iso7421.lib


texts: BJT input connected to another BJT's output and loading effects

texts:
Sedra & Smith Microelectronics, example 6.10, page 390. They ask us to analyze a BJT circuit. Here it is:

simulate this circuit – Schematic created using CircuitLab

In the next example, there is another circuit, which consists of the previous circuit connected to another BJT and resistors:

simulate this circuit

In the solution it says that assuming the first resistor is still in active mode (like it was in the previous example), then VB, IB, IE, and IC are the same.

I don't understand why would they be the same. Won't the second BJT load the first, draw current and thus change the 1st's unloaded currents and voltages?

Thank you very much.


texts:
How does the G pot (or Graphic pot) graph look like?  Does anyone have a graph?

Is it more of a linear type or audio pot?

Tried searching on Google but couldn't find the graph.

G Pot = W pot

how to make a W potentiometer from a log or linear pot?


texts:
I have a homework problem on logic gates, in the picture below:

Now, I have already made NOT and AND gates. On these OR gates, (I used a simulator by the way) I could not find any solution.

I have looked up and found the following picture:

Though this uses 3 NAND gates, I can only use 2. Remember I can set a fixed value as an input aside from A and B. How would I condense 3 NAND gates into 2?


texts: Power 12v Pump with two PSUs that may or may not both be on

texts: Not an electrical engineer at all, however i will be in need of something like this. I have two systems that will share a liquid cooling system. They both run off of their own respective PSU's. I want the pump to run while they are both on or while only one of them is powered on. As far as I can tell all I would need to do is run the PSU's in parallel with diodes to prevent feedback. Would this work for this?


texts: What's the function of the three input resistors in the below circuit?

texts: I want to know the function of the three 1Mohm resistor between the HVDC+ and HDVC-, they are R4 R14 and R17 in the below circuit, thanks for your attention and time!


texts: How to charge and use a salvaged laptop battery with BMS?

texts:
I have salvaged a laptop battery but I have no idea how I can use it like a normal battery. It does have a 10 pins connector but I have no idea what they are doing and how I can use them.

Should I just cut the metal stripes (separate the 3 cells) and use another BMS, or is there a way to use the same BMS without the computer mainboard ?


texts: What is the difference between 16-pin and 24-pin for USB type-C?

texts:
I'm pretty new to PCB design.

I am trying to make a circuit that will take 5V/3A input, charge 3.7V Li-Po battery, give 5V/2A output, and also has a charging protection IC.

For 5V/3A, it seems to me that I need to use USB type-C, even though it has many features that I do not actually need in my design. However, later on I found out that it has 2 different pin sets: 16 and 24.

The question is which one I should choose, or which one is better suited for which application?


texts: Transistors - Small signal and Large signal analysis

texts:
In analyzing transistor circuits, I know that you typically separate it into DC and AC analysis.  In doing AC analysis, we often do small signal analysis, and from what I understand, it is the region where the transistor's V-I characteristic curve is linear.  So, in AC small signal analysis, we assume that capacitors are shorted.  My questions are:

What point would the capacitor value be if we assume that capacitors are shorted?
What is small signal analysis used for?
What is the difference between small signal and large signal analysis?
When do we use one or the other? Is there some sort of advantage?
In designing, which one is used?

From my questions, you can infer that I do not know much of the implications of doing so and so analysis.


texts: Transmission lines - justification of "wavelength / 10" (or similar) rule

texts:
I have very little background in electronics, but suddenly I need some transmission line theory for a project I am working on. I have heard of various rules of thumb for how long a wire can be before you have to start worrying about its properties as a transmission line. I know these are pretty arbitrary, but the most common I have heard is that you have to start worrying about transmission line properties once the length of your wires are greater than about wavelength / 10, so I'll just go with that for this post.

My question is: what quantity or quantities are minimized by using wires that are short relative to the wavelength that makes it so that you can ignore transmission line theory? I.e., when our wire length is less than wavelength / 10, presumably there's some set of physical quantities that makes our transmission line look very wire-like in models. What are these?

As an example of the type of thing I'm looking for, here's what my first guess was: At short lengths, the phase difference for a wave would be small enough that the wave's amplitude at the two ends of the wire would be roughly the same. But this doesn't hold: sin(2 pi / 10) - sin(0) = 0.59, so if we use the wavelength / 10 rule of thumb, the amplitude change in the wave between the two ends of the wire could be more than half of the total amplitude.

As of now, I'm guessing that the actual answer is that the characteristic impedance of a wire is very near 0 (or whatever tiny resistance the wire has) at short wire lengths - i.e., you can ignore its capacitive and inductive properties. Is this correct? If so, are there some formulas relating Z_transmission_line to wire length which show that Z ~ R at lengths of about wavelength / 10? What I'm looking for is something where I can literally plug in length = wavelength / 10 and get some number close to what I would get if I plugged in length = 0, that sort of acts as a heuristic for how good a certain length is.

Thanks for any help!


texts: Can I have 2-layer design with PCIe connector?

texts:
I was wondering whether I can have a 2-layer instead of 4-layer pcb design with PCIe golden finger and PCIe connector. Should it always be 4-layer, which I found from the PCI-SIG presentation in 2004?

I have tried a 2-layer design before. But had difficulty when routing the gnd signals around the PCIe golden pins as shown below, gnd_a signals(ground signal) interleaves with Tx and Rx signals.

Thanks!


texts: Does use of cermet pots lead to scratching in a DC audio circuit?

texts: I am putting together an audio EQ module that is DC coupled.  I have read in many places that carbon pots will scratch due to DC present in the circuit.  Do cermet pots exhibit the same behavior?  I ask because I am able to find cermet pots that fit the PCB footprint, but not conductive plastic.


texts: Code error: platform.txt from core 'DFRobot Boards' contains deprecated recipe.ar.pattern

texts:
I've been trying to program a DFRobot Bluno board with Arduino software recently. It worked fine before but now I keep getting the following error:
Arduino: 1.8.13 (Windows 10), Board: "Bluno M0 MainBoard"
Warning: platform.txt from core 'DFRobot Boards' contains deprecated recipe.ar.pattern="{compiler.path}{compiler.ar.cmd}" {compiler.ar.flags} "{build.path}/{archive_file}" "{object_file}", automatically converted to recipe.ar.pattern="{compiler.path}{compiler.ar.cmd}" {compiler.ar.flags} "{archive_file_path}" "{object_file}". Consider upgrading this core.
Sketch uses 11956 bytes (19%) of program storage space. Maximum is 60416 bytes.
I get the same error no matter what code I am running and no matter what computer I am running it on. The libraries, cores, and software is all up to date.
This is the board manager url I used: https://raw.githubusercontent.com/DFRobot/DFRobotDuinoBoard/master/package_dfrobot_index.json
Could it be something DFRobot has changed in their libraries? Do I have a faulty board?
Thanks.


texts: Level shifter for multiple voltage levels

texts:
I found basic level shifters for two different voltages but I have 3 different voltages on my I2C bus.

I just wanted to verify if the schematic below will work correctly. I think it will but I am not sure if the different levels will influence the working.

Would appreciate a confirmation. (or if it does not work a tip how to solve this)


texts:
I know how voltage triangle is formed for RL circuit. But I am not understanding how impedance triangle is formed. Is it derived from voltage triangle ? If so, how it is derived from voltage triangle ?
Please don't tell that divide each side of voltage triangle with current 'I' to form impedance triangle . I want more generalised explanation


texts: Circuit with V AC and V DC after rectification

texts:
I rectified about 14V AC to about 12V DC but 6 V AC simultaneously with 12V DC at the end! It was verified by two different tests, 2W10 is apparently just an unit jammed with 4 diodes. Rs means large resistors.

Test 1: 2W10 rectifier, Rs  ---> OUT: 12.7 V DC and 6.0 V AC

Test 2: 4 pieces of "IN4004 pec616", Rs --> OUT: 12.0 V DC and 6.0 V AC

Questions

Why do I get both V AC and V DC? I expected only V DC.
How can I filter V AC out?
Can V AC be a problem in circuits that only needs the 12 V DC?


texts: What is the best way to switch between different ranges when designing a multimeter using microcontroller?

texts: We are developing a multimeter using a PIC18 microcontroller and we are searching for the best method to switch between different ranges in multimeter with the smallest possible amount of switching delay.


texts: Potentiometer with No Minimum Resistance

texts:
I'm looking to create a variable current regulator with the LM317 using 1-turn pots.
I know that I am going to need to have a resistance of 1.25 Ohms to have a current of 1A, which I want to be my max; however, all of the pots that I have (barring trimpots) have a resistance of around 1.8 ohms when at their minimum setting, and I want to use 2 in series (for fine and coarse adjustment) which would bring total resistance to 3.6 ohms. Is there any way to get around this?

Thanks,
Michael


texts: What is the mean number of mating cycles of a FMC connector?

texts:
I can't find any relevant information regarding mating cycles of FMC connectors.
I have found out that for Molex it's maximum 100 times http://polymicro.com/molex/products/datasheet.jsp?part=active/0459704105_PCB_HEADERS.xml

But a recent brochure from Samtec suggests that they have FMC connectors with mating cycles of maximum 2500(!). http://suddendocs.samtec.com/literature/samtec_silicon_development_guide.pdf

Do anyone knows what is the maximum number of mating cycles of an FMC connector? Any help would be appreciated in this matter.

Thanks


texts:
I've been getting into sampling recently, and seem to have a problem with how to actually "plot" an alias frequency, and was hoping some of you might be able to help.
I have a sin-wave with an amplitude of 1 and a frequency of 3Hz. This means that when the "wave" have repeated itself 3 times you reach 1 second in time.
But now I got a sampling rate of 5Hz (for practicing aliasing), and in theory this would simply be sampleF - F => 5 - 3 = 2Hz. However, I'm not sure how I plot this 2Hz on my 3Hz signal? How should I "think" when plotting?
My plotting of 2Hz(Fsample - F = 2Hz) on a 3Hz signal:


texts: How to use an 2-axis accelerometer as a potentiometer?

texts:
I've got a couple of Memsic 2125 accelerometers around and wanted to try to use one of them to replace a pair of potentiometers in a circuit (x axis replaces pot A, y axis replaces pot B).

How would I go about converting the output signal of the accelerometer into resistance? Along with that, how would I limit the resistance to a particular range?

(Apologies if this is a rather basic question - I'm a tinkerer and am pretty early on in my EE journey!)

EDIT: Added from comments per gbulmer's suggestion:

So the application will be a guitar pedal or something like it, so let's try with something simple. Say using just the x axis to control the fuzz pot in a simple NPN fuzz face.


texts: Capacitor to provide power to a circuit during a very small interruption

texts:
I need some help in figuring out what size capacitor I need, and if my idea will even work.

I have a small remotely-controlled helicopter, and a very small camera.  I am trying to record video while flying the helicopter around.  So far, cutting down the body of the helicopter and taking the PCB out of the camera and mounting it to the helicopter has worked well.  However, the usable flight time is reduced from 10 minutes or so to 1 minute.  I noticed that the battery on the camera and the battery on the helicopter are the same type and voltage.  What I would like to do is power the helicopter and the camera from the same battery to save on weight.

My original plan was to simply cut the camera battery out of the picture and tie the camera directly do the helicopter.  However, I thought this would cause problems, as the voltage while charging would likely fry the camera.

Then, I noticed the decorative LED on the front of the helicopter.  The voltage (3.7V or so, depending on battery charge) is exactly what is needed to power the camera.  The LED is also off while the helicopter is turned off and/or charging.  Now, this helicopter alternates the polarity going to the LED twice a second, as it is a bi-color LED.  My current plan is to cut out the LED, rectify the voltage with 4 diodes so I have straight DC, and use this to power the camera.  (Barring any current issues of course.  I plan to measure the current load of the LED vs. the camera before doing this, but I expect they will be similar, given the amount of time the camera can run off of its own battery [1 hour+] of similar capacity to that of the helicopter.)

I am going to experiment with this plan tonight, but I just realized that there is probably a very short time where the LED driver outputs 0V in between its polarity switch.  I'm thinking that sticking a capacitor in there will help with the problem, but I have no idea how to calculate what size I need.

Can you tell me what I need to do to calculate the size cap that would likely keep things running smoothly?  Again, the voltage output of the LED driver and the voltage requirement of the camera is 3.7V, but I'm guessing will be anywhere from 4.2 to 3.6 during operation.  I don't yet know the current requirements, but plan to figure those out tonight.

Thank you for your time.


texts:
I've got a task in which I need to connect 5 or more ucontrollers to one PC for the purpose of sending data which will be stored in the PC. The conditions are as follows:

The ucs in question are PIC 16F877As; each one of them is part of a system that keeps track of the number of screws used(as of now), powered by constant DCV from plugs so power is not an issue.
the data being sent are just numbers; the current number of screws used
the environment is that of a factory assembly line; the screw counters are used in the line and the env is generally noisy
the data received by the PC is to be stored in a table; I figured i can take care of this part later
the distance between each PIC is about 2-3 meters; the PC is at the end of the line, about 10 meters, the link between the PIC and PC can either be physical or wireless, although I prefer wireless as it is more hassle free(I think...), although robustness of data sent is priority
as usual, the system must be made to be as cheap as possible without sacrificing reliability

I've successfully connected a PIC to PC using RS-232 so I know enough that you can't easily connect all 5 of the PICs directly to one PC using RS; too troublesome and distance issues. What I'm thinking is something like a hub; the 5 PICs connect to a master PIC which in return gets whatever data from the 5 PICs and sends them to the PC. I've read some stuff about I2C and I think that's doable enough. I've also looked up on wireless solutions like XBee; I got SKKCA from Cytron but I dunno how to make it handle many-to-one data communications.

Anyone got better ideas on how am I can pull this off in the least painful, cheap way possible? This entire project is a one-man show so I'd rather keep things simple and inexpensive.


texts: Does the rt2832u chip have enough bandwidth for ATSC?

texts:
I'd like to upgrade the audio/infotainment module in my 2009 Camry. I see several off the shelf solutions, but they don't have a builtin digital TV tuner and the processor isn't as fast as I'd like. So, I'm considering building my own.

However, there seems to be 2 missing ingredients for a DIY solution: an integrated AM & FM radio and TV tuner? Then, I heard about the rt2832u dongle that can do software defined radio at very low cost:
http://sdr.osmocom.org/trac/wiki/rtl-sdr

It would be amazing if you can build an AM, FM, and ATSC tuner with it. I gotta scratch this technical fetish if that's possible :)

My question is, does the RT2832u have enough bandwidth to recover the compressed video bitstream sent by ATSC?

The answer seems no because ATSC needs 6MhZ while the hardware only has 3.2MhZ bandwidth? But then how is the hardware capable of handling it's original purpose of DVB-T, which is 7 or 8 MhZ?


texts: Share battery between different voltage devices

texts:
I have a keychain-sized China-made camera that has an internal LiPo 3.7v dc battery, and a TI MSP430 microcontroller that operates between 1.5v and 3.6v dc. I want to use the microcontroller on the same battery as the camera, and use the controller with transistors to digitally "press" the on/off and start/stop buttons on the camera. The end goal is to take periodic photos for time lapse usage.

My question is: How can I drop the voltage from a 3.7v battery to about 3v so I can use the same battery for both?

A CS professor I talked to suggested in passing that I can use a resistor. Will that work, and if so where would I need to insert it? How do I determine what resistance the resistor would need to be?


texts: Is bare-metal programming still a thing?

texts:
I am in the learning phase of embedded systems programming. I am curious about the industry practices. Nowadays the microcontrollers are getting powerful and comes with a lot of memory, networking connectivity and own libraries and sdks.
So I would like to know that is bare-metal programming(without OS, libraries, sdks, frameworks) still a thing in industry? If yes, then till what extent abstraction is used?


texts: What steps (electrical and otherwise) are involved in commissioning a machine?

texts:
The way I understand it, commissioning a machine refers to installing all of its systems and subsystems, making sure everything is running properly, testing it with an initial batch, documenting the processes and then, finally, handing over the machine over to the customer.

Is this everything? Is there more?

The reason I'm asking is that I'm trying to find a translation for German Inbetriebnahme, which is being used as a chapter header in several user's manuals for the parts that help make up the machine, e.g. drives/motors, HMI panels, etc. Literally, the German means "Putting into operation", but doesn't really distinguish so much between "first commissioning" and "just getting the thing running at any point". It therefore includes things like installation, first switch-on, etc. but also replacing modules, changing settings, etc., i.e. things that happen after "first commissioning".

So I guess my questions are:

Commissioning in English only has to do with the very first time that a machine is put into operation, correct?

The individual components themselves are not commissioned per sé; they are installed and then included as part of the overall "commissioning" of the machine, correct?

Am I missing anything? Thanks for any info!!


texts:
I'm trying to connect the NVIC interrupt to handle a keyboard, nonetheless I'm having troubles becuase two keys are connected to the line0, which use the EXTI0_IRQHandler, I saw in the stm official pages that there is not possible the read two pins separately from the same interrupt line. I would like to know if there is a way to configure this feature. Below Im attaching the code used to initialize the pins is:

GPIOC_KEY_Struct.Pin = GPIO_PIN_0;
GPIOC_KEY_Struct.Mode = GPIO_MODE_IT_RISING;
GPIOC_KEY_Struct.Pull = GPIO_PULLUP;
GPIOC_KEY_Struct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOI, &GPIOC_KEY_Struct);

GPIO_InitTypeDef GPIOI_KEY_Struct;
GPIOC_KEY_Struct.Pin = GPIO_PIN_0;
GPIOC_KEY_Struct.Mode = GPIO_MODE_IT_RISING;
GPIOC_KEY_Struct.Pull = GPIO_PULLUP;
GPIOC_KEY_Struct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOA, &GPIOI_KEY_Struct);
HAL_NVIC_SetPriority(EXTI0_IRQn, 2, 0);
HAL_NVIC_EnableIRQ(EXTI0_IRQn);

After the configuration I'm using the IRQ handler function, shown below:

void EXTI0_IRQHandler(void)
  {
    char test[]="0x9B";
    char test1[] = "0x3D";
    int i,a = 0,b = 0;
    //Rutina a seguir en la interrupcion
    a = HAL_GPIO_ReadPin(GPIOA,BOTON_3);
    b = HAL_GPIO_ReadPin(GPIOI,BOTON_3);
    if(a==1)
      {
        HAL_UART_Init(&s_UARTHandle);
        HAL_UART_Transmit(&s_UARTHandle,test1, sizeof(test1), HAL_KEY_DELAY);
        HAL_UART_DeInit(&s_UARTHandle);
        HAL_GPIO_EXTI_IRQHandler(BOTON_3);
      }
    if (b==1)
      {
        HAL_UART_Init(&s_UARTHandle);
        HAL_UART_Transmit(&s_UARTHandle,test, sizeof(test), HAL_KEY_DELAY);
        HAL_UART_DeInit(&s_UARTHandle);
        HAL_GPIO_EXTI_IRQHandler(BOTON_3);
      }
    else
      {
        HAL_GPIO_EXTI_IRQHandler(BOTON_3);
      }
  }

Nonetheless I'm having troubles in the interrupt because when I touch one button it send the two strings, and also only one button is working (the first button that is been configured in the code). Is there a problem in the set up of the pins?

PS.- The same code is used without interrupts and it works perfectly.


texts: How much clearance do I need between floating ground and earth referenced ground?

texts:
I have two circuits where one side is earth reference and another floating. The floating circuit is isolated by a transformer and talk to the earth reference circuit via opto-coupler.

During final phase of development, i noticed my floating ground shield got too close of the chassis ground with only less than 0.1mm of gap. I immediately tagged it as issue and as usual people will ask me how much gap I needed. (I don't really have an answer, I am only a mfg engineer). I go through some safety standard but I still don't have an clear answer.

Here is my question:

Do I need to have clearance between two grounds to avoid hazard or arc?
Since both points are concealed within a metal cover which are grounded, do I need to follow the clearance requirement as required by the safety standard?
if that is not required, then how much of gap do I need to prevent a arc over? Should I follow the safety standard clearance guideline or should i follow the 30kV/cm rules?


texts: Sizing a fuse for a different voltage rating

texts: I'm wondering if it's possible to fit a 24VDC thermal protection fuse for a 48VDC battery system. I have a 60A solar charge controller connected to a 48V battery bank, and want to connect an inline fuse between them. By what factor should the amp rating of the 24V fuse be multiplied by in order to compensate for a doubling in voltage (24V to 48V)? Or is it not as simple as I imagine?


texts: Calculate the resistances of all the possible connections inside a N-terminals black box based on measurements between terminals

texts:
Although it would seem that this is not the right SE for this thread since it is about creating an algorithm, the problem is actually about finding a systematic approach to the simplification of arbitrarily large resistive circuits of a particular pattern.

At work, we have several shorts within a piece of equipment, but we don't know where. The equipment is a black box that cannot be open. I have taken my multimeter and populated a matrix of the resistances across each combination of the terminals available. Something like:

As you know, these measurements are meaningless because of the cross coupling with other terminals. I want to know how the nets connect between each other - in other words I want to calculate the values of the resistances shown on the following equivalent circuit (example for N=4).

simulate this circuit – Schematic created using CircuitLab

There are:
$$\sum_{i=1}^{N-1}(i-1)$$
Measurements made and:
$$\sum_{i=1}^{N-1}(i-1)$$
unknown resistances, therefore it is possible to solve the entire circuit based on the table shown above with the following algorithm:

For each measurement made Rij, where i and j are 0...N.

Calculate the formula of the equivalent resistance of the circuit between terminals i and j in function of the "X" resistances. Simplify.

Rearrange to build the matrix [X] in:
$$\left(
\begin{array}{c}
R_{1,2}\\
R_{1,3}\\
...\\
R_{N-1,N}\\
\end{array}
\right)= \mathbf{[X]}\left(
\begin{array}{c}
X_{1,2}\\
X_{1,3}\\
...\\
X_{N-1,N}\\
\end{array}
\right)$$
Solve using:
$$\left(
\begin{array}{c}
X_{1,2}\\
X_{1,3}\\
...\\
X_{N-1,N}\\
\end{array}
\right)=\mathbf{[X]}^{-1}\left(
\begin{array}{c}
R_{1,2}\\
R_{1,3}\\
...\\
R_{N-1,N}\\
\end{array}
\right)$$

Steps 2 and 3 are easy, but I am having difficulty finding an algorithm to deal with the calculation of the equivalent resistance automatically. I can do up to 4 terminals easily (there is a Star/Delta transform to do for 4), but my system has 7 terminals and the manual method just is not good enough anymore, and I have tried it.

Kirchoff laws feel more suited to the automatic generation of the equations, but even though I think I can generate the node equations, I don't have a systematic way of generating the loop equations.

It is a very interesting and exciting problem to which the solution will be useful to many people in my opinion. Could someone help me to automate the calculation of the equivalent resistance (or solve it for N=7, after all it would also work for N<=7)?


texts: Monitoring SD/TF Card status while interfacing with separate host

texts:
I'm working on project that requires taking several terabytes worth of RAW photos on DSLR controlled by a microcontroller. Initially the plan was to use a small Linux SBC running some kind of control software (gPhoto2 likely) that would trigger image capture and store the photos in a bank of drives. I'd really like to simplify and miniaturize this solution if possible.

The thought now is a bank of SD Cards (maybe eMMC) selectable through some kind of mux tree like this FSSD06. Essentially a scaled up version of this. The big uncertainty though comes from knowing when an SD card is full and the controller should switch to the next empty one. I'm looking for some kind of middleman type host controller that sit between the camera's SD interface and the SD card itself that can provide information about the state of the SD while forwarding communication through it. Am I dreaming of something that doesn't exist or does someone have another solution to this problem? I'd really appreciate any input - thanks


texts:
Some say UART is hardware, some say UART is one of the serial communication protocol.

UART is a protocol

UART is a protocol

UART is Hardware

UART is Hardware


texts: SDC (Synopsys Design Constraints) Timing Exception for Latch Before Launch - FPGA

texts:
I am acquiring data from an ADC whose serial output makes the first bit available immediately after completion of a conversion.  Then, the FPGA sends clock-pulses to the ADC to shift-out the remaining bits.
This arrangement causes a setup violation (negative slack) in the data-path.  The first rising edge is the latch edge (because the first bit is already available).  The second rising edge launches the second bit.  The launch clock lags the latch clock by 130 degrees.  The period of the clock is 10ns.  The path report indicates that Timing Analyzer thinks that the latch edge is 3.5ns after the launch edge. However, in reality, the latch edge is 6.5ns after the launch edge.  So I just need to tell Timing Analyzer that it is mistaking the latch edge for the launch edge (and vice versa).  This is the problem.
Is there a good timing exception for this scenario?  I don't want to use "set_false_path" because I need the path analyzed.
The following is the ADC's timing diagram:

The following is the path violation report:


texts: PCb creation: how far to keep 240v ac from low voltage?

texts: as the title describes, I have a question about the distance that should be kept between low voltage and high voltage PCB traces. Does anyone know the standarts for Europe?


texts: What is an AC voltage rating for a capacitor?

texts:
I thought the only thing that mattered was absolute voltage across a capacitor puncturing the dielectric, but there are some that have an AC rating, too.  What does this mean?  Why does the value change at different frequencies?

I see Vrms vs frequency graphs, this equation

\$V_{rating} \geq {1 \over k} \cdot V_{PP} + |V_{min}|\$

etc. but I'm not sure I understand it.

How do you rate a capacitor if it will have both DC and AC superimposed?  If, for instance, I'm putting 200 VDC average across a 33 nF capacitor, with a superimposed 70 kHz AC waveform that occasionally reaches 1200 Vpp (so 424 Vrms, 200 + 600 = 800 Vmax, and 200 - 600 = -400 Vmin), then what does it need for DC and AC ratings?


texts: Turn an LED off and on with the same push button

texts:
How can I have an LED turn on when a push button is pressed, turn off when the button is pressed again, and keep its state unchanged when the button is not pressed?

I don't want the LED to oscillate if the button is held down for a while, and I want immediate action (not having to hold the button down while waiting for a capacitor to charge).


texts: Using pot as variable resistor: should wiper be connected to spare end terminal?

texts:
I've heard somewhere that a rheostat uses two pins while a potentiometer uses three. But still, the thing i would like to know is if there's anything different with the adjustment if I wire the pots like this:

Or will it not matter how I wire it? Thanks!


texts:
I have replicated the li-po battery charger with the famous TP4056 , the protector DW01A and the mosfets FS8205A... exactly like the comertial board.

I design a board that contains this circuit (and MCU, sensors linear regulators etc... all conected to "OUT+/OUT-"), so when the user charges the battery, he can still use the product.

In the comertial board they solder the thermal pad of the TP4056 to the VIN+ ( ??????? not like the datasheet recommends) What happens to me is that i have solder it to GND (like the datasheet recomends)...I don't know if is for this or not but my battery charger circuit is salowing 1.6mA from the batteries all the time (not in charging periods)...what is super high...

Also if i disconect the R5 resistor, the current consumption decreases .... so i supose that the DW01A is consuming a lot ...and i dont know why

Anyone of you experiment so much current consumption on this devices???

THANKS A LOT


texts:
I'm not native English speaker, so forgive me my bads.

Ok. Here's the deal.

In my Arduino UNO I need more outputs and inputs. I bought 3 MCP23017s. One of them for receive states from 8 microswitches and other to control 32 LEDs.
LED states depends on which microswitch is actually pushed(only one of them could be pushed in time). For example:
When I push button on B block(0x20 mcp23017s) in 0 pin, all I want to do is send 10101010 to 0x21s block A. And it's working for only one button.
When I connect second button I want to send 10101010 to 0x21s block B.
And there's problem.
It doesn't work. For one button everything is ok, but for more than one it's not.
No matter if I push first or second button it always send 10101010 to 0x21s A block. It send 10101010 to 0x21s B block only, when I push 2 buttons at the same time, but it send bytes to A block too...

Hardware is ok, because I checked it for one button and everything was working well, so problem must be hidden in software.

I know that you could don't get what I mean, so here is code:

http://pastebin.com/YiJUmqba

#include "Wire.h"

byte buttons = B00000000;

void setup()
{
  Wire.begin();

  Wire.beginTransmission(0x21);
  Wire.write(0x00);
  Wire.write(0x00);
  Wire.endTransmission();

  Wire.beginTransmission(0x21);
  Wire.write(0x01);
  Wire.write(0x00);
  Wire.endTransmission();
// To set all of 0x21 pins as outputs

  Wire.beginTransmission(0x20);
  Wire.write(0x00);
  Wire.write(0xFF);
  Wire.endTransmission();

  Wire.beginTransmission(0x20);
  Wire.write(0x01);
  Wire.write(0x00);
  Wire.endTransmission();

// To set all of 0x20 pins as button inputs
}

void loop()
{
  buttons = B00000000;
  Wire.beginTransmission(0x20);
  Wire.write(0x13);
  Wire.endTransmission();
  Wire.requestFrom(0x20, 1);
  buttons = Wire.read();

  switch(buttons)
  {
    case B00000001:
    // A block
      Wire.beginTransmission(0x21);
      Wire.write(0x12);
      Wire.write(B01010101);
      Wire.endTransmission();
      break;
    case B00000010:
    // B block
      Wire.beginTransmission(0x21);
      Wire.write(0x13);
      Wire.write(B01010101);
      Wire.endTransmission();
      break;
    default:
      // A block
      Wire.beginTransmission(0x21);
      Wire.write(0x12);
      Wire.write(B10101010);
      Wire.endTransmission();

      // B block
      Wire.beginTransmission(0x21);
      Wire.write(0x13);
      Wire.write(B10101010);
      Wire.endTransmission();
      break;
  }
  delay(20);
}

I need this in my project which is very important for me, so please help me.
Thank you!


texts:
I have a circuit  that is fed into a ADC chip (adc128s022), that I am trying to understand. The sensors are inferred gas sensors. Could you please criticise my analysis.

The way I am reading it:

Diodes between gnd and signal are for clamping the voltage and protection.
Inductor , two caps and 200 ohm resister are a low pass filter.
10k resister is for further protection.
Op amp is acting to clamp the voltage 0-5V and for impedance matching?
The resister and cap after the buffer are another low pass filter. Is this because the buffer could amplify some small amplitude signal noise?

I am not sure what the point is of the first capacitor, may be to protect the sensor?

I am guessing the different low pass filters before the buffer are for different frequency?


texts: Harmonic compensation due to a non-linear load

texts:
I am doing a project on harmonic compensation due to non linear loads. My current at the source is non-sinusoidal due to non linear load. The current contains harmonics and i am using ACS712 current sensor for harmonic current measurement but i know ACS712 doesn't show harmonics and its output only shows main current.

What should I do to sense harmonic current for accurate display of non sinusoidal current waveform in my oscilloscope and to use this sensed current harmonics for microcontrollers?


texts: How to receive the digital data from an ASK/FSK Receiver (E.g. TDA 5210)

texts:
While reading the specs on a FSK/ASK Receiver (E.g. TDA 5210 ) I am asking myself how actually the (non Manchester encoded) digital data look like and how to I receive it when sending from another device on the correct frequency

Can the DATA pin 25 "easily" be attached to a Raspberry Pi / Arduino?

Will this be a UART communication?


texts: Detecting ultrasonic by microphone and MCU

texts:
I design data-over-audio transmission to MCU. To do it i need ultrasonic detector with specific frequency, for example 50kHz.

Seems, that electret microphone+low-pass filter+envelope detector will solve problem

Microphone

Low-pass filter

Envelope detector

How to calculate resistors and capacitors for this scheme?

Also i have idea to use ready-made solution HC-SR04, but don't know, is it ok


texts: What is the jitter of an asynchronous FIFO?

texts:
I have an asynchronous FIFO (in a Stratix V FPGA) with two asynchronous read and write clocks of the same frequency of 100 MHz. As I understand, asynchronous FIFOs have a two-register resynchronisation stage.

Because the relative phases of the two clocks can wander up to 10ns, the jitter of the FIFO is at least 10ns. Am I correct? Is the jitter of an asynchronous FIFO at least one clock cycle? Is it more than one clock cycle?


texts:
I am creating a 16 by 16 LED Matrix using 74hc595 Shift Registers to address the columns and using 4017 Decade Counters to control the row. I am using the 4017's in connection with a transistor to sink the current from the LED's. I understand how to use one 4017 to sink the current but I am trying to cascade another 4017 so I can count until 20 using outputs. I have an arduino providing the clock signal and have tied ENABLE output to ground, and can control CLOCK and RESET

An explanation of why a supposed solution works would also be great, as I would love to understand how my matrix works from the inside out.


texts: Optical linear encoder for motion tracking?

texts:
I need to find a cheap optical solution to measure the position of an object in relation to a surface.

The object glides in a linear motion along an axis, around 30mm away from the surface.
The maximum distance the object can travel along the surface is about 3m.
The accuracy of the system can be +/- 5mm.

What I'm really looking for is a hobbyist-level solution, such as printing a 3m long tape with reference markings to cover the surface, and attaching a laser scanner to the object that can interpret the markings and relay the coordinate to a computer.

I'm happy to create the reference tape myself and program the encoder, though I don't know where to begin looking for the hardware. Any ideas / alternatives?


texts: PIC16: Why are the configuration words 14 bit, but all other registers 8 bit?

texts:
A PIC16 (e.g. this one) have a bunch of registers, which are 8 bit wide, and two "Configuration words" (see pages 43, 44) which are 14 bit wide.

Why do the configuration words make exception for the PIC16?


texts: How can I determine the alloy in a Peltier module?

texts:
Simple question, I know I have the following Peltier module : 12711-5L31-03CL. I have it's datasheet.

I'd be interested in knowing its alloy so I can know it's Seebeck coefficient and thermal coefficient. I cannot find what its alloy is. Is there somewhere else than the datasheet where I could find it? On the site of the company, I can't find it either.


texts: Is it possible to run a photodiode plus op amp on a 3V battery?

texts: Naive question here. I've been toying around with the idea of making a simple light meter. From what I've read, photodiodes generally offer the best sensitivity and accuracy (as compared to photoresistors etc.) The simplest op amp circuits for photodiodes seem to require at least 12-15V. However, there are commercial lightmeters which use photodiodes and run on a single 3V battery (e.g. http://www.sekonic.com/products/l-758dr/specifications.aspx) Is it possible to achieve this using a "rail to rail" op amp, or is it more likely that these devices obtain a reading from the photodiode without using an op amp at all? (The latter is certainly possible but I wonder if the cost in sensitivity/accuracy would be too great.)


texts: Is volume controlled through a potentiometer?

texts:
Eletronics newbie here.
I am building my first prototype (using an Arduino) that includes a volume knob. I want to know if volume is controlled by a potentiometer because I saw this video and it got me curious how a device like that can handle audio so easily.

So the question is: the majority of equipment today that have a volume knob, control the volume through a potentiometer? i.e the greater the resistance, less volume I will have in a speaker?

If so, why? Does that means the speaker will vibrate with less intensity?


texts: How do current ratings on barrel connectors work?

texts:
I'm trying to power a pcb using a psu that is rated at 12V 10A and has a barrel connector with a jack that is 2.5mm x 5.5mm. I've tested my board with screw terminals and it draws about 8A. I want to make the design easier to connect and disconnect the power but I'm having a hard time finding barrel connectors that will work. I can't seem to find any barrel connectors that are rated at or above 10A for 12v dc.

On digikey they suggest http://www.digikey.com/product-detail/en/PD-40V/CP-7440V-ND/2712203 as the connector for psus that supply up to 17A but it is only rated at 7.5A.

Am I misunderstanding how the current rates are listed or is there a special way to connect one of these high current dc psus to the board?

Thanks


texts: How to amplify little signal of a photodiode using an OP amp?

texts:
I was trying to work with a photodiode that is supposed to detect very tiny amount of light.  Using different kind of lenses I succeeded amplifying the light amount that will fall on the photodiode.  Now I have to work on the photodiode’s ability to convert the light into electrons / increase the pd's sensibility.
Hence I had experienced only little success getting the photodiode to receive the small amount of light and convert it into electrons.

Now I learned that an Op amp will significantly help to amplify the signal provided by the photodiode. Moreover I learned that a lock-in amplifier might be a solution in my case.  Being a rookie in electronics I first want to work with an op amp (lm358n) and then try my luck with the more complicated lock in amplifier.
Working on a circuit with an op amp I came up with this circuit (see figure) considering the suggestion given in this post as well How to Use SFH235 IR Photodiode Correctly?.

However the photodiode does not really react to the provided light. I guess there is something wrong with my circuit.

Can anyone give me a hint what I am doing wrong or what I have to do to get it right?

Datasheet OP Amp http://www.ti.com/lit/ds/symlink/lm158-n.pdf

Datasheet Photodiode http://www.farnell.com/datasheets/57158.pdf

As Ignacio Vazquez-Abrams mentionied I have just test the circuits provided in the http://www.ti.com/ww/en/bobpease/assets/AN-31.pdf document.

Indeed the sensitivity of the photodiode has increased. One question left:  The circuit on the right side makes use of an LM 108 and a capacitor on pin 8 ( due to the datasheet pin 8 of the op amp stands for Comp). Not having this pin on L358 what can I do for that?

Morever the arduino analog pin normally indicates a value btw 0-1023.
Now using the op amp I get a maximum value of 767 ( this means approx. 3/4 of 1023).
Is there any particular reason for that or am I doing any mistake?


texts: Powering On/Off Quectel BG95 LTE & GNSS module

texts:
I have a Quectel module of the BG_95 series, for LTE and GNSS.  Haven't gotten to use it but am trying to integrate it with a PCB.  In the hardware design guide they list a circuit for powering off and on the module, datasheet1.2 and V1.3datasheet1.3 which is slightly updated but requires making an account to download.  I am confused by what some of the terms are like V_IL and V_nom?  Am I correct in saying that the pulse high has to be greater than 1.5V and pulse low has to be lower than 0.45V?
For the PSM wake-up (second circuit diagram) the description says it is rising edge triggered, pulled down by default, and 1.8V power domain.  What does this mean?
The description for powering off is as follows:

The description for powering on is as follows:


texts: Ltspice - Simulation problem of cross regulation in a multiple output flyback

texts:
I am trying to show the effect of the leakage inductance on a multiple output flyback. According to those documents from Unitrode and texas instrument (this one : https://www.ti.com/lit/ml/slup081/slup081.pdf and from this one : https://www.ti.com/seclit/ml/slup261/slup261.pdf). The current on each output is function of the leakage inductance between the different secondary outputs :

If we consider the following transformer :

The equivalent circuit of this transformer is the following. The circuit has beeen normalized for better understanding.

In the formula above, L1 is equal to Lw1 (the wiring inductance) and L2 is equal to the leakage inductance between the first secondary output and the second secondary output plus Lw2 the wiring inductance on the output of this secondary output. Lw1 and Lw2 refers to the "normalized circuit" figure below
So I have try to see this relation on LTspice, but it actually do not suceed. My PC do its maximum for simulate the circuit but it do not exceed 68 % of the simulation (I m bad in LTspice...) Here is my simulation :

Is there a better way for simulating the effect of leakage inductance on a multiple output flyback ?
Thank you very much and have a nice day !


texts: Slew Rate related EMI: How relevant is it for motor control circuits ?

texts:
I am designing a 3-phase inverter board for BLDC Motor control. The H-bridges i use are IFX007 from Infineon. The mentioned IC has the possibility to adjust the slew rate.

From what i have read, i've understood that higher slew rates result in a more "perfect square wave" shape which in return gives rise to more high frequency components (Fourier Analysis).

Those extra high frequency components lead to EMI ( Electromagnetic Interference).

I plan to control the H-bridges with 20 KHz PWM (suitable range for Field Oriented Control). The problem is, if i limit the slew rate and make it as small as possible, the valid duty cycle with 20kHz drops to between 20 % and 80 % due to the rise time. (the rise time consumes nearly % 30 of a whole duty cycle).

On the other hand, i can just increase the slew rate and make the rise time way faster, having a larger range of duty cycle(which i would love to have) as a result but higher EMI.

My question/dilemma is: Would increasing the slew rate with the flowing specifications be ok:

14 V Power supply feeding the motor
The motor wont draw more than 5 amps in any case
the H-bridges switching at 20kHz
no wireless component or delicate analog circuitry that would be 'victimized' by the EMI. (only the MCU will be stacked on the far side of my pcb.)


texts:
I have a question about Trusted Platform Module header on PC motherboards. I want to install ESP8266 (standalone) inside of my PC, I know of 5VSB the the PSU supplies, but after looking at my mobo manual I saw TPM header with 3VSB pin, I could avoid using voltage regulator in that case. I'm only unsure how does that pin get 3V from the 5V, if it's capable of driving 200mA. I looked at some TPM datasheets and TPM consumes about 30mA to 50mA.
Is there any legitimate way of acquiring motherboard "modern" schematics? I could study some of them and draw conclusions from there.


texts:
I’m working on a personal project at the moment and needed a small amount of electronics help. What I am building is a RaspberryPi/Arduino connected to wall plugs (which is not being fitted to the wall but rather attached to a Pattress box and will be used like a bulky power strip).

The RPi is connected (5v) to a relay (rated 250v 10a) and runs a dumb node server (this end is my specialty) that controls the relay. I am going to use twillio so that you can SMS the plug a command such as -

“Brew coffee for 10 minutes”

This will then turn the relay on for just 10 min. The issue I have is with the confidence of my electronics. If you feel you could help please could you take a look at the schematic below -


texts: What specifications must I consider for a DC motor?

texts:
I'm working on a project where I need a DC motor that is capable of tightening a bolt with a motor. The applications will typically be automotive, therefore, the bolts will need to be tightened to torques between 20 and 250 ft-lbs. Most DC motors that I have found have a stall torque of less than 1 ft-lbs.

What specifications of a motor to I need to consider to find a motor and gearbox that would be capable of achieve these torque values?


texts: Speed problems in homemade RS232-to-TTL converter board

texts:
I'm still trying to debug this RS232-to-TTL converter board that I've made, shown below.

Now I think I've narrowed down the problem to speed:

it works fine at 57,600 baud;
but it inserts some errors during comm at 115,200 baud.

This time I tested the board with a simple echo firmware below, which basically echos back whatever comes into the serial port.

void setup() {
  Serial.begin(57600);
}
void loop() {
  if (Serial.available() > 0) {
    Serial.write(Serial.read());
  }
}

At 57,600 baud, it returns a series of B chars without errors, as below.

BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB
BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB

At 115,200 baud, a few errors make into the output.

BBÂBBBBBBBBBBBBBBBBBBBBBBBBBBBBBÂBBBBBBBBBBBBBBBBÂBBBBBBBBBBBBBBBBBBBBBBBBBBBB
BBBBBBBÂBBBBBBBBBBBBBBBBÂBBBBBBBBBBBBBBBBÂBBBBBBBBBBBBÂBBBBBBBBBBBBBBBBBBBBBBB
BBBBBBBBBBBBBBBBÂBBBBBBBBBBBBBBBBÂBBBBBBBBBBBBÂBBBBBBBBBBBBBBBBÂBBBBBBBBBBBBBB
BBBBBBBBÂBBBBBBBBBBBBBBBBBBBBBBBBBBBBBÂBBBBBBBBBBBBBBBBÂBBBBBBBBBBBBBBBBBBBBBB

The error rate seems to be fairly constant and it's always the same. Note that the difference between B and Â ASCII char codes is just one bit negated and another one shifted one position left.

B - 01000001
Â - 11000010
    ^     ^

The MAX232 datasheet says it works up to 120 kbps, so I think my board is causing the problem.

So, that's the new evidence I've got so far. My question is: What would be the likely reason for the problems with my converter?

Here's a picture of my board design, if that helps. Disregard the TX and RX LEDs, I've disconnected them.


texts:
I'm trying to find replacement batteries for my UPS, I checked my local store and they dont' have this particular model I need so I'm looking for other brand that does exactly the same.
What I usually see on the battery label is something like 12V 7Ah or 12V 9Ah. However, this one is 12V 21W. Does anyone know how can I convert the 21W to the equivalent Ah? Also, what is the reason of specifying the spec in Watt rather than Ampere-hour?

Below is the spec sheet of the battery in my UPS:

http://www.csb-battery.com/upfiles/dow01320199011.pdf


texts: The equivalent circuit for \$V_{in} > 0\$ with the amplitude of \$V_{out}\$

texts:
I have a strong mathematical background and I am trying to improve my (poor) physics.
If this is not the right stackexchange forum for this subject, I would be grateful if you could refer me to the right one.

I have created the following electrical circuit:

I am trying to calculate and draw the following things:

The equivalent circuit for \$V_{in} > 0\$, giving the amplitude of \$V_{out}\$.
The equivalent circuit for \$V_{in} < 0\$, giving the amplitude of \$V_{out}\$.
The signal \$V_{out}\$ as a function of time, for a full cycle of the input signal.


texts:
I have checked a reference design because I use the same microcontroller for my thesis.
The PLL power input is filtered by a ferrite bead and a capacitor. I have simulated the circuit and I found that there is a strong resonance at 300kHz.
I assume the reference board is functional so I don't understand how this can't be a problem. Do you know why this is not a problem?


texts: Convert IEEE Double to Integer - Verilog

texts:
I want to convert the IEEE Double value computed in my code to Integer.

E.g. I have computed:
X = 64'hxxxxxxxxxxxxxxxx;
Now i want to use it as index of an array as:
some_array[X];

How can I do it? Is there any IP-Core or any other third-party Core for this conversion? Or some synthesis-able method/algorithm?

EDIT:- My number X between is 0~2601 which is valid range for my array, BUT it includes fractions and I only have to

a) convert the number from IEEE double into integer format, and

b) remove the fraction part (round it off).


texts: how to safely increase the distance between ws2811 chips

texts:
I'm designing a pick to light system based on ws2811 chips + leds and an mcu like arduino uno or mega.

The average distance between the independent light modules will be about 2m which is in the 10m range specified on the datasheet.

Any two point the distance more than 10m transmission signal without any increase circuit.
https://www.adafruit.com/datasheets/WS2811.pdf page 1.

The point is that between the mcu and the first light module will be a distance of about 25m.
This may also happen between the independent light modules.

I have 3 ideas about how to solve this problem.

put dummy ws2811 chips every 10m.
use opamps as buffers or increasing the voltage to the maximum input voltage.
use diferential amplifiers like those used on the dmx512 protocol.

Could somone point me to the right direction?
What's the right way to increase the distance between the ws2811 chips?

Notes:

I don't care about refresh rate as it could be as low as 2fps.
There will be extra power suplies on every say 5 modules more or less.
There will be about 12 output lines from the mcu.
There will be about 100 light modules.

Sorry for my english.


texts:
I have a small 12v system for my cottage with a solar panel, charge regulator and a battery. Mostly used to charge phones and to drive a few lights.

Now I'm planning to connect a inductive load (12v water pump) to this system and I'm worried that this motor can cause voltage spikes that can damage other electronics connected.

How should I connect this motor to be sure it doesn't damage other stuff connected to the system?


texts: Old NiCads behaving suspiciously: is this safe?

texts:
I am the proud owner of a new very old laptop, which comes with two very old NiCad 9.6V 2400mAh battery packs. Toshiba PA8708U, if you care.

The power supply appears to be failing (it won't turn on), but it is charging the batteries --- so I let it do that for an hour or so. One of the batteries, from stone dead, has charged to about 12V. The other is at about 10V. The voltage being produced by the charging terminals is 15V.

I know that NiCads tend to charge at fairly high voltage and are current-limited, but I wouldn't expect the battery voltage itself (while disconnected from the charger!) to go above the rated 9.6V.

So I am deeply suspicious. Is this normal behaviour? Does it indicate that the PSU is overvolting the batteries? Will they catch fire?

(The batteries are now safely disconnected, BTW.)


texts:
Basically, I want to build the following circuit on my breadboard to compare my analytical and my experimental results. The power source is going to be a signal generator. How can I set this up? I am new to building circuits and have no idea how to translate my schematics into a breadboard.

This is what I mean by breadboard


texts: Are termination resistors needed for UART, I2C and SPI?

texts: I see that termination resistors might be needed for some communication lines. What about UART, I2C and SPI, are they needed ? If yes, how do we choose their values?


texts: In Verilog Synthesis, Creating several Instantiation of a Module is the same than instantiate several modules with same content?

texts:
I wonder if there is a difference between creating several instantiation of a single module and to instantiate different modules (with identical hardware code) only one time.

For example, I want to make an operation --binary division--, I need to do 2 divisions consecutive, example B = 1 / A and C = A / 28, which I need to happen at the same time, so I create the module in another file named Bin_Div. In the top module I type

 Module top_mod_oper (A,B,C);
 input [31:0] A;
 output [31:0] B, C;

 Bin_Div inst1 (

 .dataa (A),
 .output (B));

 Bin_Div inst2 (

 .dataa (A),
 .output (C));

 endmodule

that will create 2 independient hardware, correct? would it be the same that just create a second Bin_Div, for example

   .
   .
   .
 First_Bin_Div inst1 (

 .dataa (A),
 .output (B));

 Second_Bin_Div inst1 (

 .dataa (A),
 .output (C));

 endmodule

And Another question, what should I do if I want them to happen consecutively, it means one after the other using the same hardware Bin_DiV.


texts: Is there any way to use industrial sized IC's package in home project?

texts:
All actuals DSP or MCUs comes in BGA-like  packages with numerous pins and very small size that make them hard to integrate in home project. Does anyone has knowledge of revolutionary breadboards, cheaps sockets or just expansible developement boards that would make this task easier ?
Just for notice, I take my interest in audio systems. This far I never put feet on hardware ground (just sofware) despite old theoretical knowledge bundled with my university graduation.


texts: Why Emitter current increases with increase in collector to base voltage in common base configuration of a BJT?

texts:
It is said from early effect that with increase in collector to base voltage there is decrease in base width due to which \$\alpha\$ (the current gain) increases due to lesser recombination of holes and electron, so with increase in \$\alpha\$ emitter current should decrease according to equation

$$I_E=\frac{I_C}{\alpha} \, .$$

Also, concentration gradient of minority charge carriers in base region increases and due to which more majority charge carriers (of emitter region) come from emitter to base region and hence increasing emitter current.

Both of these effects are in contradiction to each other, so does it happen like latter effect is more than the former?


texts: Understanding pull-up resistors and the 7489 memory chip

texts:
I have been learning about the 7489 memory chip. I had two of these that turned out to be broken (see here for previous question on this). I got more and I have finally gotten everything to work.

From this answer, I learned the basic idea of how to set up the circuit. So now I have the following (schematics more or less copied from here). The following works well!

simulate this circuit – Schematic created using CircuitLab

I am still new to digital electronics and I am just trying to learn. My question is: How can one determine an appropriate pull-up resistor?

For example, in the answer to the earlier question, the resistors R1, R2, R3, and R4, were suggested to be 2.2 kOhms. I chose 1kOhm. Does it matter? Is all that matters what the LEDs need or is there something relating to the 7489 that helps determine the size of the pull-up resistors? If it is only the LEDs (forward voltage 2V and current 0.20 mA) I would guess that I could actually use 220 Ohm. Is that right?
Also, for the inputs (address and data input) I did choose 4.7 kOhm. What here determines the size? There are no LEDs so I assume it has to do with the IC, is that correct? What should I be looking for in the datasheet?


texts: How to power two LEDs with a 1 Farad charged Super Capacitor as efficiently as possible?

texts:
I have came across a awesome super capacitor Flash LED Driver chip for cameras.

On page 10 of the LED driver datasheet, it says:

  How long the LED current is regulated depends on the initial  CAP
  voltage,  capacitor  value,  the  charge  current, LED forward voltage
  and the LED torch current setting

My questions are:

How long can two SVL 5630 , 2.8v, 200mA, LEDs  remain on when driven with an On Semiconductor, 4 Amp Super Capacitor, flash LED Driver powered by a 1 Farad super capacitor charged to 3V?

Is there a more efficient way to drive these LEDs?


texts: Common emitter amplifier biasing and resistor selection

texts:
I'm designing a standard common emitter amplifier. My textbook states that it's standard to make \$V_C = 2/3 V_{CC}\$ and \$V_E = 1/3V_{cc}\$. I understand that it has to with maximizing the voltage swing, but it's affect isn't clear to me. Why is doing this a standard practice?

Say \$ V_{CC}=12V\$, then \$V_C=8V\$ and \$V_E=4V\$. Since the output of the amplifier is taken at the collector, the output is at \$ 8V \$ with no input signal. I'm told that the swing is +/- \$ 4V\$, so the range of the amplifier is \$ 4V \$ to \$ 12V\$. I guess I don't understand what is meant by swing and how one arrives at these numbers. I sort of get that it can go up to \$12V\$ until it clips the signal since the transistor can't go higher than \$ 12V \$, but why can't it pull down lower than \$4V\$?

Another thing; I've read that if \$ \beta \$ is large, say 200, then \$ I_E \approx I_C\$. That makes sense to me, since the collector current will contribute to most of the emitter current for large beta. However, my prof said for this reason we are allowed to make the collector and emitter resistors the same value. Why?


texts: I2C level translation mosfets obtainable to hobbyists

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Based on this AN for level translation and overvoltage protection for I2C buses, I am looking for a recommendation for a suitable mosfet that is obtainable for hobbyists.

The recommended BSN20 and its replacement part BSN20BK are impossible to get hold of for me. Are there any common-place alternatives for a 3.3V I2C bus? (I am looking for at least 30V drain-source voltage for overvoltage protection.)

I realise that I am skirting quite close to a "sourcing question" with this but hope somebody will take it in the spirit it is intended and can recommend an equivalent product for what is surely a fairly common problem.


texts:
I'm building one of those DIY reflow ovens from a toaster oven, a K-type thermocouple, a MAX6675 breakout board, a SSR and an Arduino.

I'm having a lot of trouble getting a reliable temperature measurement from the MAX6675.  With the Arduino powered (through a USB connection) but the mains part of the circuit disconnected, I get a good temperature measurement.  But as soon as I plug the mains in, it goes haywire.  It's not even particularly predictable; most often, it just reads zero, but sometimes it reads about 750 degrees, other times it wanders up and down between zero and a hundred degrees or so.

It's a bit hard to tell, but it seems that just plugging the earth pin of the mains circuit in is enough to cause this.  I guess I have a noise problem, and since it seems to be the earth connection that does it, I guess it's a ground loop.

The thermocouple is a screw-in probe type, which I've insulated from the body of the oven using kapton tape.  I've connected the braided shield to the Arduino's earth; on the scope, this improves the noise situation considerably, though it doesn't seem to make much difference to the measurement.  Initially I had the MAX6675 mounted fairly close to the SSR, but have since moved this, again without it making much difference.

What else should I try?  Would connecting the arduino's earth to mains earth be a good move?  (The Arduino is being powered from a laptop that probably doesn't have a very good earth).

Thanks for any suggestions!

Update

FWIW, here's what the 'scope shows between T+ and T-:

The peaks every 40ms look fairly nasty, but it's not immediately obvious to me what would cause them.  There is a solid state relay nearby, but it's just off at this stage, so wouldn't expect switching noise from it.


texts: PIC32: "16-bit code" doesn't work (many errors "unknown opcode")

texts:
I have very little test project for PIC32MX440F512H, which builds (with XC32 v1.21) and works correctly.

Then I tried to generate 16-bit code, set checkbox "Generate 16-bit code", additional option appeared: -mips16

But now I get a lot of errors, here's a part of output:

 make -f nbproject/Makefile-Orion.mk SUBPROJECTS= .build-conf
make[1]: Entering directory `D:/projects/trcomp_bundle/project_common/fw_test_pic32/appl/fw_test_pic32.X'
make  -f nbproject/Makefile-Orion.mk dist/Orion/debug/fw_test_pic32.X.debug.elf
make[2]: Entering directory `D:/projects/trcomp_bundle/project_common/fw_test_pic32/appl/fw_test_pic32.X'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s: Assembler messages:
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:223: Error: unrecognized opcode `rdpgpr'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:226: Error: unknown opcode `mfc0 $k0,$13'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:229: Error: unknown opcode `mfc0 $k1,$14'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:232: Error: illegal operands `srl'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:238: Error: illegal operands `sw'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:241: Error: unknown opcode `mfc0 $k1,$12'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:244: Error: illegal operands `sw'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:247: Error: unrecognized opcode `ins'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:250: Error: unrecognized opcode `ins'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:253: Error: unknown opcode `mtc0 $k1,$12'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:256: Error: illegal operands `sw'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:277: Error: illegal operands `sw'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:280: Error: illegal operands `sw'
d:\home\progr\LOCALS~1\Temp\ccnv5akn.s:283: Error: illegal operands `sw'
 .................

I tried to clean project and rebuild, result is the same.
If I remove that option, project is built successfully again.

What could be wrong?


texts: Abracon AB1805 RTC IC - additional resistance on VBAT pin?

texts:
I intend to use Abracon AB1805 RTC in designed device, powered by a CR2032 battery. IC datasheet contains a note: * Total battery series impedance = 1.5k ohms, which may require an external resistor

The CR2032 battery has an impedance of about 20 ohms, so the note indicates that I should add a 1.5K resistor between the + battery and the VBAT IC pin ??
It is a bit strange for me because virtually no power source for RTC (coin battery, supercapacitor) has impedance even close to 1.5K.
Even on the Abracon evaluation board schematic, I do not see any additional resistor on the VBAT pin.


texts:
I'm using a raspberry pi to program an atmega328p. During my tests I was using 3.3V to power the avr and it was pretty straightforward, whenever a program is about to be written I pulled low pin 1 (reset) as per the specification and went to town.
Now the real deal is running on 5V and thus it's pin 1 is also kept high with 5V.

simulate this circuit – Schematic created using CircuitLab
Pretty much anywhere you look you will find that feeding 5V into a GPIO is not a good idea, however with a 10k resistor that's about 0.5mA which should not be a problem?
Alternatively if I had to use a transistor, I'm guessing I'd have to go with a PNP type which would also sink the 5V so I don't really know how that would work out.
I'm still just a noob here, please don't be harsh, and thank you for your time!


texts: Safe dead time limit on 19Khz PWM sine wave inverter

texts:
I'm buiding a 60Hz sine wave inverter based on 19Khz PWM generated by a PIC16F883 (lookup table) using a half bridge with 4 x IRF2807 - switching a pair of low-side/high-side. I'm using my own designed MOSFET driver with discrete transistors. I'm feeding the bridge with 12V and using a 700VA transformer to step up the voltage from 12V to 127VAC.
I still have some small wave distortion specially with inductive loads such as a fan motor (in the picture, an example with a 60W/127VAC fan).

Question: Looking at the oscilloscope screen capture, do you guys think I should go further in reducing the deadtime to enhace the wave quality and still be safe to avoid shoot thru current? Or should I keep it and go for the final PCB, since the circuit is still on protoboard, so parasitc inductances may be present.
Each vertical division means 10us in the PWM wave. I fixed the duty cyle just to capture the image.

Thank you!


texts:
I am trying to make my own ti link/parallel, with a female stereo port, and parallel port on the other side. I don't know what I am to do with the jack. I have three wires: gold, white and red, which I have to connect to the jack, according to:

This schema (no colors)

And this one with wire colors (fr ; rouge = red, or = gold, blanc = white) :

The problem is : my jack has 3 connections: one is longer (B) the second at its right is round (A) and the third rectangular-shaped at its left (C).

Please speak simply because I am a noob in electronics and my English is not very good, thanks.


texts: Moving mass storage design from SD/MMC to NAND flash

texts:
We have a prototype design in the works, that is currently running on a reference board done my Olimex (Olinuxino maxi), but eventually we would like to move the storage from microsd to nand flash (or eeprom).
It seems that i.mx233 supports both of these, as they have a reference design of their own (imx 233 EVK), which has support for this.
However, their design was 8 times more expensive than from Olimex, thus we decided to start from here.

This is our first project in this scope ("real" linux system), and thus we are still learning as we go.
Basically our problem is that neither of us is experienced yet in this level of design.. We don't really understand what we should consider when moving our boot target from sdcard to flash..
Like starting even from how do we connect the flash chip to the imx ? It seems that there are "SPI headers" for that, but what does that mean ?
Boot target can be changed with some slight soldering, so that should take care of the loader, I presume.

I have studied the workings of linux boot process, and it seems that if we can get our flash chip seen by the loader, we should be able to get the kernel loading after that, or is there something more to look out for ?

I would appreciate any tips for studying, book recommendations etc..
Thanks!


texts:
!CPC1230N
Single-Pole, Normally Open
4-Pin

Link for Datasheet:

http://www.ixysic.com/home/pdfs.nsf/www/CPC1230N.pdf/$file/CPC1230N.pdf

This is the relay I am using in my circuit, but I am not getting how it connects/disconnects and flow of i/p. ( It has two control i/p's and two load pins )

Please explain its operation.


texts: How can infer instability from the frequency response of control system?

texts:
When can we judge a control system to be unstable from its frequency response?.For example, thermostat computes the error signal (desired room temperature - actual room temperature) and then actuates accordingly. If the error is positive, the thermostat increases the room temperature to value of the error signal and if the error is negative, the thermostat decreases to the error value. I am aware that there is a time delay for the actuator to reach the error and may also oscillate before reaching the error value.

If hypothetical room temperature fluctuates, our error signal would also fluctuate and so would our actuation. We therefore check the system's response for sinusoidal error signal for a range of frequencies. Now, how and when do we reach the conclusion of instability from frequency response? My understanding is that quality of response of the control system depends on rise time. Large rise time and high frequency error signal is not desirable. Could someone elaborate on this or correct my understanding?


texts: Are external diodes needed to protect these MOSFETs from back emf?

texts:
(note: this post has been updated as suggested by members)
The schematic below shows a single coil to be pulsed by n & p FETs. Each FET has 100V ds breakdown and < 10 mOhm Rds. Vgs threshold is +/- 2V for each. Vgs max = +/- 20V. There is no possibility for both FETs to have low Rds at the same time.

The objective of the circuit is to pulse a single coil in either direction. Each pulse should be considered independent of those prior - there is no timing relationship between pulses other than a minimum time interval between them. This is not a motor driver. Pulses aren't alternating. The coil is being used to repel a magnet. There will be significant concerns due to the magnet - I have a good understanding of those concerns and am only interested in the circuit provided (i.e. without magnet).
Once I know how to protect the FETs I will push the circuit right to the point where Vds is almost exceeded. I could get FETs of Vds max = 120V but  question would be the same with rails at +/- 60V instead of 50V. I could keep going until Rds is too large or FETs get too expensive, so these specific values aren't the point of my post. The idea is to push the limits while protecting the FETs.
The coil shown is ~ 40mH with internal resistance 140 ohms, but I am interested in general principles that work for variable coil parameters. Assume between 5mH and 100mH. Vdd may be as low as 12V and as high as 50V as I experiment with pulse widths, duty cycles and field strengths. I realize back EMF may be significant, and I'm not sure how to protect the FETs other than to just lower Vdd. Current demand per pulse will be way below FET capability.
Consider gate signals to be wired correctly. Assume the circuit is perfect on that side of the schematic - it will not be a challenge. (unfortunately I didn't state this well upon first posting and there was a lot of confusion on that point. many apologies to those that wasted time because of it).
Last point which I'm sure some will ask me regards pulse widths and duty cycle. The hope is to create pulses at widths between 0.1ms and 2ms. Duty cycle flexible depending on noise, heat, ringing and of effects from back EMF. The ideal case which I don't expect to achieve: 0.5ms pulses that aren't a terrible mess (some ringing/noise will be acceptable). Current between 0.15A and 0.5A. Duty cycle 0.3 max. The final result can be a bit off from this and I'll be happy.
Many thanks for everyone's help already, specifically DKNguyen and Bruce Abbott!


texts: What are the electronics components that have characteristics like Neon Lamp?

texts:
Neon lamps have higher breakdown voltage than its operating voltage.
When brokendown, it acts like a zener at its operating voltage.


texts: Measuring very small changes in a low resistance circuit

texts:
I have a circuit where I am trying to detect when a systems resistance drops from ~5-20 mOhms to half or lower (~<1-10 mOhms) with a micro controller.
my microcontroller can read between 0-3.3v with 10 bit precision, or about 3.3 mV changes. I was hoping to get much larger changes out to give me confidence that I'm actually measuring the drop in resistance. My MC can also source 15-20mA of current at a pin.

My plan is to make a voltage divider with R1 much higher than R2, since making them even sort of equal will draw too much current from my pin. With V=IR being 3.3/.015= 220 ohms for the lowest resistor I can use for R1. At best this gives me ~ .3 mV of max voltage drop if my test circuit starts with 20 mOhms of resistance. I would like to build a voltage amplifier circuit to boost the voltage signal from the divider. I've drawn up a preliminary circuit ( you can replace "mosfet" with any transistor in your mind), but looking at diagrams of BJT and MOSFET transistor circuits that are used to amplify voltage, I am guessing I am missing something. I need around 1000x amplification.

I'm not sure the voltage that would be at the Gate of a MOSFET would be sufficient to turn it on at all, or that the voltage would be amplified. Maybe a darlington pair of BJTs? I'm worried that the power through the base of a BJT would interfere with my measurements.


texts:
I have a mystery that needs solving. I have what looks like a transistor. It has three pins which should be emitter, base, and collector. The package is labeled A129. I have tested it with a multimeter using the diode function and there is voltage through no matter how I place the meter leads. I assume it's broken. But the mystery is that it alone makes at least a single LED blink at a constant rate.

I have it hooked up to a breadboard with DC power (was trying to use a capacitor and transistor to make a blinking LED and couldn't understand why it wouldn't work, lol..) at 3.3V. If I put it to 5V it does not blink anymore. Is it not a BJT?

Update - Photos added as requested:


texts: What does this schematic symbol mean? (triangle with a line crossing it out)

texts:
I found the following circuit symbol in an MSP430 User's Guide in the section describing the ADC:

(I made a red circle around it)

What does it represent?


texts: Help With My Motor Controller Circuit Diagram

texts:
I'm a novice when it comes to electrical engineering, primary since I'm a programmer. However, I am trying to make a drone for fun and I made a really(REALLY) basic motor controller with some NPN transistors and a raspberry pi v2. But I want to make sure that I'm doing everything nicely, but more importantly right.

Please, any feedback on my motor controller and circuit in general will be a great help!


texts: STM32F303 Microcontroller open drain GPIO, Can it reach / be pulled up to 5 Volts?

texts:
I hope you are all doing well... :).

I'm working on a project with pulse width modulation however I need my logical high output to be 5V. However, as my Vdd is 3.3V, the output high level is approximately 2.9V however this isn't sufficient for my needed purpose..

Somebody suggested that I configure the IO pins to open drain mode which I did actually through CubeMX, and I connected the pin to a resistor and that resistor to 5V.. However, the output of the logical High level is still around 2.8V..

I have looked through the user manual of the microcontroller which is namely a stm32f303vct6 but I couldn't find anything literally anything related to whether the pins can be pulled up to 5V or not, and if so then which pins exactly are 5V tolerant..

Could you please shed some light I may follow. I really appreciate it... I've been searching for a couple of hours online but to no avail..

Thank you!


texts:
As a PCB designer, is there a known list of advantages and disadvantages to using BGA vs. QFN packages?
Here is the list I have discovered (please correct me if they are incorrect):
BGA
Pros:

Smaller footprint

Cons:

X-ray needed for inspection
Microvias may be needed
Multiple layers may be needed for breakout

QFN
Pros:

Pins accessible by probe
1 layer needed for breakout

Cons:

Larger footprint

When a component is available in both BGA and QFN packages, what factors govern which package should be used?
Thanks in advance!


texts: Algoritham to caluculate State of Charge(SOC) & State of Health (SOH) of the LI-Ion Battery?

texts:
I am trying to understand the battery management system, but I didn't find any algorithm for columb counting (or) voltage method or any thing else. can you please share this algorithm's if they are with you (or) please share that information to get that algorithms.

My idea to calculate the State of Charge & State of Health of the battery for CAR(preferably electric), please help me to understand this.


texts: I have a question asking to draw a circuit for a NAND gate with one nMOS and one pMOS. The way the question is it sounds like it means only one of each. I know you can do that gate type with two nMOS each to an input betwen ground and vdd so if both inputs are "1" the bothe gates are open and the path is open, and Ive seen a version with two pMOS between vdd and the output, but I dont see any way to di it with just one of each. Is this posible, are am i taking the meaning of the question wrong?


texts: What is the "Home" feature of the Stepper Motor Driver IC (DRV8811)?

texts:
While doing research on efficient methods for driving stepper motors I came across the Texas Instrument IC DRV8811. This particular device has a Home feature that is explained very little. The datasheet has a Step Table that gives information regarding output phase, etc. This table has a Home state defined as the fifth step when operating in 1/8 step mode.

Is this Home state simply the fifth step offset from whatever arbitrary position the stepper motor happens to be at when powered on?

The device also has a Home pin that appears to pulse whenever the driver IC has reached this state. The only information given in the datasheet is:

  Logic low when at home state of step table, logic high at other states

I have never before seen such a feature, so I wanted to verify exactly what this feature was prior to committing to a purchase and design.


texts: How does the comparator in the NE555 compare its two inputs?

texts:
This is a circuit diagram from the very detailed and helpful NE555 Wiki page. The yellow and red coloured segments are comparators, comparing Thresh and Trig to fractions of Vcc. If I know how a comparator works, I understand the circuit and I'm happy. I have stared at the yellow part for too long! I can't seem to understand why it works.
The red and yellow parts are not symmetric in their inputs, which tells me there is something to be seen there. I don't see it! From what I understand, most of these are depletion mode. By the way, the bold line under the third BJT starting from top left going right is Gnd. The output of the comparator is the line from the Thres side of the circuit into the purple flip flop part.
When 2V_cc/3 < Thres, the comparator goes LOW. What is the causal chain of clearly connected events which drives the output to low after this (given that the initial state was HIGH, i.e. Thres > 2V_cc/3)?


texts: Looking for design advice for custom electronic lock

texts:
I'm building a door lock that will be controlled by a Raspberry Pi Zero W.

Here's a link to the lock I'm using: Electronic Cabinet Lock With Status Reporting (MA1208S-T)

From what I understand, this lock will basically have three states:

Always unlocked, which requires a constant 6 V to keep the log disengaged.
Locked, which requires no power.
And a quick unlock, which requires 12 V to pop the lock (it gets very hot if I'm always pumping 12 V into it to keep it unlocked).

Here's a picture of what I have working:

I'm using a 12 V adapter to power everything.
The pi uses a 12 V to 5 V converter cable.
I'm using two relays and two step-downs in order to control the voltages

My question is, is there a single component I can use that would replace the relays and step downs? Like something I can control with the Pi? I feel like I over complicated this and I'm hoping someone can give me better direction.


texts: High temperature high voltage electrical insulation under water

texts:
I am mechanical engineer, and it is my hobby to make some thing new from broken and expired machines.

I found a broken electrical kettle, and I want to make a water heater from it by using its coil. The coil is already insulated, according to design it is to hang it in water.
Now I need to insulate the connection of wires for the coil.

Please I need help to find insulation material, which can withstand High temperature of the coil, also give it electrical insulation under water. And also from where I can get it easily.

Thanks


texts: Can a common mode choke be used at the output of an SMPS?

texts: If there is CM EMI on DC power supply lines, can a CM choke be used at the output of SMPS supply? Im asking because all CM examples I saw are for AC power lines.


texts:
I have a string of WS2801 LEDs (the type most often used with an Arduino or Raspberry Pi over SPI), as well as an evaluation kit/breakout board for USB-to-SPI-master (MCP2210).

However, I am more of a software guy and don't normally deal with hardware and electronics, so I'm having some issues actually getting the LEDs to work at all.

My setup is as follows-

LED strand connected to a 5v 2A wall power supply
Data wire connected to MOSI on MCP2210
Clock wire connected to CLK on MCP2210
MCP2210 connected to a Windows PC running the driver software

The issue is, with the above setup, the first LED on the strand seems to cycle through all of the colors continuously, without me sending any data. With the ground wire (spliced off the strand) connected to GND on the MCP2210, there is no cycling but the first LED remains lit a solid color (I'm assuming this indicates that no data is being sent to the strand, since it's capable of staying lit without further input).

So, my first question is-- should the ground be connected to both the strand and the MCP2210 module?

If not, what could be the cause of the cycling colors and how can it be prevented? I'm assuming it may also be some sort of issue with the data rate or clock, since it's cycling at a fairly constant rate...


texts: What voltage is put across the Tx+, Tx-, Rx+, and Rx- lines over ethernet?

texts:
I'm trying to figure out how to wire up an LED, probably controlled by a FET, for an activity indicator for ethernet. I'm not trying to make one that supports official error codes or anything, but just something that blinks on and off as the line goes high or low.

So what is the voltage differential applied to the lines, and would they be high enough to power an LED or control a FET spliced into the line?

EDIT:The point of this indicator is actually not to verify transmission or proper TCP/IP activity, but instead just to make sure that there is anything happening on the line.


texts: charge batteries in parallel at 3.7 V and discharge in series at 11.1 V

texts: I have 3 of 18650 lithium battery cells and one heat element and one TP4056 charging module. I want to connect the cells in parallel to the charging module to charge them and at the same time I want to connect them in series to power the heat element with 11.1 V. how can I do that? and what are the alternatives if that's not possible?


texts:
I'm currently designing a logic circuit to compare two 4-bit numbers using an XOR gate IC (TI CD4070B).

I'll then need to combine the output of these four XOR gates to into a single line using OR gates. If this combined feed returns a 1, then I'll know the numbers aren't equal.

My question is: do I need to use a dedicated OR gate IC, or can I simply wire together the outputs of the four XOR gates? My main concern is if one of the XOR gates returns a 1, then voltage will be back-fed into the outputs of the other three XOR gates (potentially damaging the chip or spreading back to the inputs of the XOR gate?).


texts: Make One Full Power XBox One Adapter from Two Underpowered Adapters

texts:
Unfortunately, as of this time, Microsoft does not sell XBox One AC adapters. XBox One adapters are almost always single voltage. I'm an expat who has bought a US XBox One and would like to use it in Europe. Since no one can source an XBox One EU adapter from Microsoft, the only other source are Chinese knockoffs that are underpowered.

Microsoft US Voltage AC Adapter Specifications:
Input: AC 100~127V 4.91A 50/60Hz
Output: DC 12V 17.9A (215W), 5Vsb 1.0A

Chinese Dual Voltage AC Adapter Specifications:
Input: AC 100~240V 2A, 47~63Hz
Output: DC 12V 10.83A (130W), 5Vsb 1.0A

Can I combine two underpowered adapters, wired up in parallel, to create one full powered source? For both 12V and 5V? What are the risks? Any other options?

There's some hope a knockoff will work as is. AnandTech has tested the draw from an XBox One and found that it only draws 119W max, and as low as 69W otherwise.

http://www.anandtech.com/show/7528/the-xbox-one-mini-review-hardware-analysis/5

Edit - 16-Dec-2013
Thanks for the suggestions about using a stock power supply. Looks like any PC ATX power supply will provide the proper volts at more amps than the knockoffs. They are often dual voltage too. For example:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817152019

This ATX power supply has +12V@18A on pins 10 and 11 (yellow wires) and +5VSB@2.0A on pins 9 (purple wire).

How do I hook up the ATX power supply to the XBox One's two prong connector?

http://www.tinydeal.com/eu-plug-ac-adapter-power-supply-for-xbox-one-p-106421.html

(1) Should I bundle multiple ATX +12V wires together or can I use just a single wire?

(2) I assume that ATX +5VSB amps, being double the XBox One adapter, is ok to use?

(3) I'm making an assumption that the XBox's dual prong plug needs +5V and ground on one prong, and +12V and ground on the other.

(4) I can probably wire the XBox One plug to an ATX female to mate with the ATX power supply.

(5) What are the caveats and am I missing anything?


texts: At what load is the leakage current quantified for a power supply?

texts:
In this document it says "According to IEC 60601-1, the leakage current limits are provided in Table 1."

If the leakage current is due to Y capacitor, the load R and the the parasitic capacitance of the PSU transformer will form an RC divider.

But then the leakage current depends on the load. If the load is big the stray voltage will be big and the leakage current will be small. If the load is small(low impedance setting), then the voltage will  be small but the current will be higher comparing to high load impedance.

For which load the leakage current is measured and presented in datasheets?


texts: Guidance & Info about Quadcopter Project

texts:
I'm new in forum and since I made some research the past days I'd like to get some guidance about constructing & programming a Quadcopter from scratch since I'm completely new on a project like that.

Quadcopter Frame: Thinking about to construct an aluminum 70cm diameter frame which will weight around 500g. What kind of motors should I get in order the frame with the board,motors etc. will be able to lift?

Board: I'm thinking to use Arduino Uno or Raspberry Pi 2.0 ( With a little bit of research I made I conclude that Raspberry could make my life a little bit easier since you can add wifi on it. The quadcopter will be controlled via a pc/laptop through wifi). What can you suggest and why?

ESC: As far as I've seen in most of similar projects people using ESCs in order to control the motors throttle. Can you avoid that, with programming PIDs that make the same job in order not to use more hardware?

About PIDs and Code in General: Thinking about to simulate the whole project in Simulik, Matlab and somehow (if it's possible) to convert the Matlab Code into C++ and download it on the chip. What do you think about that?

About the whole project: I'm trying to minmize the hardware as much as it's possible (use only 4x motors, the board with the chip on it, cables and probably some sensors) in order to minimize the total weight of construction and ofc the price.

That's all for a start. I'm gladly waiting for your answers and ideas.

Cheers  :)


texts:
I recently bought arduino uno r3 and started with simple program which blinks embedded led:

#define LED_PIN 13

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

void loop()
{
    digitalWrite(LED_PIN, HIGH);
    delay(500);
    digitalWrite(LED_PIN, LOW);
    delay(500);
}

A problem is that this program isn't working. After uploading it seems got stuck in some state (led is constantly on or constantly off).

But in case program is using serial module -- arduino works as expected.

#define LED_PIN 13

void setup()
{
    pinMode(LED_PIN, OUTPUT);
    Serial.begin(9600);
}

void loop()
{
    digitalWrite(LED_PIN, HIGH);
    delay(500);
    digitalWrite(LED_PIN, LOW);
    delay(500);
}

Where is the problem? Or it is by design and should work this way?

About toolchain:

avr-g++-4.4.6-r1 p1.0, pie-0.4.5
arduino-1.0.5
avrdude-6.0.1
avr-libc-1.8.0


texts: Can I apply gorrila glue on to a AAA battery to attach a wire to it?

texts: I am repairing a old CB radio I got at a yard sale and I'm powering it with 2 AAAs and a 9 volt. I have to attach a wire to all of the ports, and tape isn't very effective. I'm wondering if it it safe to use superglue on the metal surface of the battery (and keep in mind it's only 9 and 1.5 volts), and I know superglue is not a conductor.


texts: Question about the MOSFET saturation condition

texts:
I'm solving a problem in my textbook and I got stuck, and I have the solution manual of the textbook, so I went to see through the solution and I found a thing that I suspect to be wrong, due to my understanding, but It obviously could be wrong, so I wanted to get help, as I'm self-studying electronics.

At first, the book says that it will use this model for the MOSFET:

To my knowledge, and due to calculations that is previously in the book using the (switch-current source) model the boundaries of the saturation region are:
$$ V_T\le v_{in} \le V_T + \frac{-1 + \sqrt{1 + 2V_sRK}}{RK}$$

in  this problem, it's about two cascaded MOSFETs:

now comes what I don't understand. I will quote the solution manual.

this condition on the saturation region is what I don't get. It's essentially the same as the upper bound of the condition that I provided above, but it has the boundaries on \$ V_{s} \$
How are both of them related as I can't see what I'm having wrong?

Also, I think that the details I provided are sufficient for my question, I can provide the whole question and answer from the textbook if needed.


texts: Electric stove heating element and switches

texts:
I am having difficulty in understanding how heating elements and switches work to control how much heat is dissipated in the element of electric stoves or other similar settings.
From one perspective I have learned the more resistance in say a conductor the hotter the conductor itself gets.  The smaller wires get hotter as thicker wire with respect to the same voltage applied to both.
I am certain that the heating element hardly has any resistance in that sense.  Or if the lower resistance heating element won't get as hot as the higher resistance element.
With respect to the control switches, if they control voltage by means of having their own some sort of metallic variable resistors which in turn must get hot and get old.  And if this varying voltage determines the amount of current to the heating element and not the heating element itself.
I am also wondering if a heating element with more resistance will get hotter than the one with less and what happens to resistance as the heating element gets old?
It is the type of stuff that bugs me.


texts: How come no voltage is meassured across my electrolysis tank?

texts:
I've built myself a electrolysis tank, using a plastic barrel as the container, rebar as the sacrificial cathode, a 12v 15A car charger (DC), and a Sodium Carbonate solutions as the eletrolyte. The anode is a rusty piece of metal that I need cleaned.

This works wonders, but I noticed that when I charge a 12v battery with the charger, the analog voltmeter jumps to around 12v as soon as I connect the terminals, but it doesn't when I connect it to the electrolysis tank?

I've seen it jump once, in the electrolysis tank - All the other times it's been near zero (Maybe slightly over?)

How come this happens? Shouldn't I measure 12v since that is what I output, or am I missing something? I am thinking that could be a huge voltage drop in the electrolytic solution, and that I'm actually only seeing a few volts, could be hard to read and display on the analog voltmeter (However, I'm not sure this is how it works...)

The charger/powersupply's negative wire is connected to the anode and the charger/powersupply's positive wire is connected to the cathode. The voltmeter is build into the charger/powersupply.


texts:
I have uploaded a feed imprint from Mouser electronics site. the symbol and the Footprint are good.

but when I look at the component in 3d on the software (pads logic and pads layout) I see the power supply as its:  (image)


texts:
I have watched several videos on the Hall Effect, but when I try to create the effect in my garage I get zero results. As you can see in the attached photo I have a volt meter connected across a metal plate and a battery voltage connected on the other sides. Any ideas on why I am not seeing any Hall Effect voltage? The magnets are two Harbor Freight ceramic magnets. I have tried them in different configurations. I have even tried an strong neodymium, no success.
I am not an electrical engineer so please keep that in mind when answering.
Thank you