texts: How can I find temperature of microcontroller?

texts: In some boards which environment temperature goes up could cause high temperature in micro controller. This will effect on micro and bad situation maybe occurs. For example I have designed a device which used in a box. This box was near a motor and after some load to motor I encountered a high temperature near micro. So, anyone could help me if there is any solution for finding temperature of micro? This micro could be AVR or PIC. If micro could find it's temperature, it could terminate working before any bad damage.


texts: Simple CAN bus design, communication issues

texts:
I am trying to get some simple communication between two boards that I've designed with an ATmega328P microcontroller and MCP2515/MCP2551 combination.

The design is as follows:

I have both ends terminated with the 120 Ω resistor and jumper soldered. My multimeter reads 60 Ω between CANH and CANL on both sides. Both boards share the same power supply (common 5 V rail, common GND).

Software side, I am using an Optiboot bootloader and the Arduino environment for faster prototyping. (I set both my controllers on NormalMode with default filters a.k.a receive all for testing). I've tried a lot of libraries for the MCP2515, and software don't seem to be the problem.

Two of the best libraries I've found:

https://github.com/autowp/arduino-mcp2515
https://github.com/Seeed-Studio/CAN_BUS_Shield

My problem is that I can't get the communication to work.

The boards won't receive messages from each other, while they can receive messages from a third-party board, but still can't send to said board.

As you can see I have RX_CAN and TX_CAN probe points between the transceiver and controller. Scoping TX_CAN on the transmitting board and RX_CAN on the receiving I get this weird behavior when I zoom in a single low portion of the message (yellow is the RX_CAN).

I've already tried replacing the controller and transceiver chip. Could this be a bad decoupling capacitor?

Update:

After removing the LEDs, which was the problem for the weird noise, I still can't get the signal on the receiving side to follow the rest,
Shouldn't the CANH/CANL signals be opposite?

The first two are CANH/CANL. Pink is TX on the transmitter side and blue is RX on the receiver side.

mcp2551 pcb layout


texts:
The electro-chemical reaction is more favorable at higher temperatures. Consequently, when it is warmer, the batteries will perform better. This is also evident from practice: old batteries do not start the car when it's cold.

Now, about storing batteries. I heard some people store their batteries in the refrigerator. How, if at all, is it beneficial, as opposed to storing at room temperature? If it is not beneficial, what are the souses of such misconception?


texts:
I want to start building a tube headphone amp from the details on DIY Audio Projects, but I'd like to understand what I'm doing there too.

Source: DIY audio projects.

While I get most of it, I can't understand why the LM317 is placed after the output MOSFET and not before it. Can anyone shed some light on this choice?


texts: What is this called, PCB bevelled fingers?

texts:
I found this non-plated fingers PCB connector, with blackish color, in a Logitech MK240 wireless keyboard. This fingers connect between the PCB and plastic sheets wiring (for the keys).

It is a bit beveled, or I'd say furrowed (black has more bevel than grey in the pic), as to enable the center of an individual finger to give more pressure to the sheets I thought.

What are these fingers specifically called, especially when requesting fabrication? Are these fingers replaceable with usual PCB traces beveled with solder?


texts: Ebers–Moll model aF? Where does it come from?

texts:
I am just getting back into electronics after a long while. For the life of me I can't figure where the \$\alpha_F\$ variable in the Ebers–Moll model comes from when you are calculating \$I_C\$ or \$I_B\$ using the formulas given under the Ebers–Moll section on the BJT Wiki Page. My first instinct is that it is \$h_{fe}\$ , if I am to take the meaning of 'common base forward short-circuit current gain' literally, since \$h_{fe}\$ was the closest rating I could find in any datasheet.

So what I am asking is: Where do you get \$\alpha_F\$ when you are using the Ebers–Moll model of a BJT?


texts: Analogic pin 0 (pin 14) problem UNO board

texts:
I have an Arduino Project developped for an UNO Arduino Board; the sketch have a size of 30000 bytes aprox.

The whole set of features requeried works perfectly, but I have a problem with the A0 pin

In input mode
Early, on the project developement, I tried to use the A0 pin to read three buttons linked with resistors; after many issues, a change to the pin A1 solved the problem.

In output mode
On a later phase of the project, when I have occupied the rest of pins, I need to sent digital signal by the A0 pin... really the signal is sent by a function that send to digital 2, A2 and A3 pins also; but as in the referred pins the signal it's constant, on the A0 pin seems flickering

I tried to change many questions of the software, but isn't effective. So, this occurs on three UNO original boards and three selfmade boards with the chip and the bootloader uploaded -the A0 pin incorrect on the board it's statistically discarded ;) -

Any idea to resolve this?


texts: Control a C program on a PC with external digital/analog inputs

texts:
I developed a code in DEV C++ which simulates graphically a the actions of a train driver. Basically I control the speed and some other functions of a train from my keyboard.

Now, instead of the keyboard, I want to use a "home made mouse" i.e. digital/analog inputs to control the program.

Read some articles and seem quite difficult.

Can anyone help me with some advice, or point me in a few directions?


texts: Is there any way to simulate (show on oscilloscope ) the sum of more than two periodic signals on PROTEUS?


texts:
I have this motor driver design set up on a breadboard for a bipolar stepper motor. I was able to drive the motor forwards and backwards for about 5 minutes. I realized that two of the P mosfets were getting hot until they became untouchable. Then I turned off the power supply which was limited to 6V, 0.8A. Then I turned off the power supply until the mosfets were cold. I turned the supply on again but I didn't send any commands to the motor driver and I realized that the same mosfets were getting hot again. I tried to move the motor forwards or backwards but it would only stall. I would appreciate if someone could help me troubleshoot the design of the motor driver. The mosfets I am using are 2N7000, IRZ44N and 4P03L04

The motor I am using is this one https://www.amazon.com/gp/product/B00PNEQKC0/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
Nema 17 Rated current 2.0A & resistance 1.4ohm

The GPIO logic level from my mcu is 3.3V. I am not suppose to use motor driver ics since it's for a school project, but I'll appreciate any other suggestions, thanks.


texts:
I have an STM32 driving two very similar SPI Flashes, an N25Q and an M25P.

Strangely, while my driver copes with the N25Q perfectly well, the M25P is only "half" working. What happens is that when I write a page of bytes, and read that page back, the four MSB bits of each byte is 0, and the four LSB bits of each byte is correct.

What could be causing half the bits to be 0?


texts: Use of Audio Tranformers in Amplification

texts: I came across this ckt to make a wireless ear phones using Infrared Signals from IR LEDs. I am unable to understand the use of Audio Transformer here to amplify the audio signal, instead OpAmps would sufffice the necessity. There would be a change in input and output impedances in both cases(OpAmps, Transformers), but why would that bother the signal.....


texts:
I am using a stm32f407vgtx to control full bridge drivers which drive a H bridge of 4 N-channel Mosfet. I don't have any idea about grounding.
I am thinking of using two separate ground AGND (ground of 5V ) and PGND (power ground 24V) then I will connect them together with a Net Tie.

_ am i on the right path.
_ Any advice or reference can help me (grounding consideration).

Thank You.

Best Regards


texts: What is current modulated laser driver? What does it do to the laser?

texts:
The title is actually one of the many questions I have. I've started to work on a project that includes lasers. I've worked with lasers and fiber optics before and I even constructed a simple constant current driver and used it in a fiber ring laser system. So I am not that unfamiliar with the concepts. However, all these were quite basic. Okay now let me ask my questions.

1) I've been told that I need a current modulated laser driver to use one of my 1550nm laser diodes. (LUCENT D2570)

https://www.koheron.com/photonics/drv200-laser-diode-driver

Here's the link of the product. What is this current modulation? What does it do? What does that 5MHz mean? What is its effect? Does it make the CW laser pulsed? Because my advisor said it had to be 5MHz to obtain 200ns pulses. If it does make the laser pulsed, how does that happen?

2) I also have a 1310nm pulsed laser diode.(NEC NDL7503P1) It is a coaxial laser with 4 pins. When I first started working on this project it was activated with a DC source which was simply connected to laser anode and cathode with alligators. I was also told that I need the same driver given in the link above. The question is, how does this diode work with that simple connection? Does the DC source act as a constant current supplly? Since it says the laser is pulsed, does it generate pulses with this connection or does it mean that it can generate pulses when with a suitable driver? If so, what kind of driver is that? Is it the one in the link? How do you make it pulsed? Is it CW now without the driver?

I know some of these questions are silly or requires very basic knowledge but the guy working on electronics left. Therefore, I now have to work on both optical part and electronic part. I know don't know much about this topic but before coming here believe me I tried everything to learn these.

Thank you for your precious answers.

Rigby.


texts: solar power ESP8266 microprocessor circuit to turn off when low voltage

texts:
I intend to run an esp8266 microprocessor on only solar panels so it is on during the day and off/disabled during low light conditions that do not supply sufficient power.

Is there a circuit that will hold the esp8266 reset low until voltage is sufficient (>3v) to power the esp8266? Hysteresis would be beneficial.


texts: Anti-aliasing filter closer to amp or ADC?

texts:
I'm designing a board with several amplified analog signals being fed into the internal ADC of a PIC DSP (dsPIC33FJ256GP710). Because of the board size/shape restraints, the analog buffers can't sit as close to the PIC as I would like, but my simple RC anti-aliasing filters can.

My question is this: is it better to have my RC anti-aliasing filter close to the output of my amplifier, or close to the input of my ADC?

Related information: I will be sampling 8 signals at 1kHz, 0-3.3V signals


texts: Are those calculations for primary coil of a transformer correct?

texts:
The calculations in this question are based on my previous quesion:
How many turns do I need for the primary coil of a transformer?

Marko Buršič said : "B_max shall be between 1.3T and 1.6T, but not more than 1.6T."

I calculate the minimum number of turns so that the core is not saturated:

B=1.6 and f=50Hz

Area = 0.009 * 0.015 = 1.35 * 10^-4 sq m

N = 220 / (4.44 * 50 * 1.6 * 1.35 * 10^-4)

N = 4587 turns.

I think the number of turns is too much, Am I missing something ?

According to Andy aka equations:

L = N^2 * AL = 210 H

XL = 2 * PI * f * L = 66 K ohm

I = 3.33 mA. (primary coil)

If I need 12 volts on the secondary coil:

I = 60 mA (This is too little for the secondary coil, I'm missing something here too)

Here's my core dimensions (cm):

Thank you for all your assistance, Andy aka and  Marko Buršič, I really appreciate your help. And special thanks to Andy aka who answered a lot of my question and taught me much useful information :)


texts: Switch on a LED: why doesn't this code work?

texts:
I am using DEMO9S08AW60E and using Codewarrior(Version: 5.9) with Processor Expert.

PTFDD = 0x00;  // to activate/intialize the port F and D
PTDDD = 0x00;

if ((PTDD_PTDD2 |= 0x02))
{
    PTFD_PTFD0 |=0x01;
}
else
{
    PTFD_PTFD0 &=0x01;
}

Link for DEMO9S08AW60E.

According to the schematic of the board, Switch 4 is connected to PortD/Pin2. And the set of LED are connected to the PortF/Pin(0-7). The idea is to switch the LED on when the button is pressed: I have used a pull up resistor with the help of PROCESSOR EXPERT.  Logically, I feel my code is fine but there doesn't seem to be any effect.

I would like to know where I am going wrong and hope you will able to help.


texts: What is the point / name of this circuit? Reverse voltage protection + current mirror?

texts:
I stumbled across this circuit on page 8 of the Nano Pi Duo 2.
What purpose does it serve?
I recognize the MOSFET arrangement to be a reverse voltage protection circuit and the PNP transistors form a current mirror I believe.
From my Spice simulation, it seems to do reverse voltage protection and suppress some short transients (<30 ns.)
Can anyone else provide more insight into this?


texts: How to design the value of capacitor for Capacitive DAC based on noise and mismatch analysis?

texts: In order to design the correct value for the capacitor in a capacitive DAC, we need to look at two possible causes of errors. Noise and Mismatch Analysis. sqrt(kT/C) should be less than 1/2 LSB. But, the value of C seems to be very high based on this equation. (For a 14bit DAC its about 1nF) Also how do we bring in mismatch analysis for the DAC to conclude about the capacitor value?


texts: Why does 3-to-5 volt with transistor not work the way it should?

texts:
A quick google for "3v to 5v transistor" gives me dozens of circuit diagrams that look like option A below with a NPN transistor and a pull-up resistor. If I build the diagram in iCircult, it works as expected. However, when I wire it up on a breadboard, it doesn't work quite the way it should. Without any power to the base, I get Vout = 4.95v.  With power to the base I get Vout = 0v so it is inverting my wave.

A few experiments later, I solve my problem using a PNP transistor and a pull-down resistor (option B). In both cases I am taking Vout from the Collector side of the transistor.

It's a pretty simple circuit, you'd think it would just work. I double and triple checked the connections. I have also posted a photo of the breadboard below. I always seem to have weird problems like this when working with transistors, so now I am sort of on a quest to understand why option A doesn't work like it should for me?


texts: What will be the current flows through the following circuit?

texts: I`m confusing to see a textbook there is no current flows through the 7 ohm resistor. But why? And what will be the total current flowing through the circuit?


texts: DAC: What waveform should I expect when ramping up?

texts:
I have a 14-bit DAC. Ramping the data pins linearly from the minimum of 0x0 to the maximum of 0x3FFF I see (using a scope) the analogue output voltage behaving as follows:

In the first half (from 0x0 to 0x2000), the voltage ramps from 1V to 1.8V.
In the second half (from 0x2000 to 0x3FFF), the voltage ramps from 0V to 1V.

Is this the expected behaviour? What output voltage range should I be expecting for the analogue output? Why is there a "break" at 0x2000?


texts: Using two separate USB connectors, one for power and one for data: do I tie their grounds?

texts:
for a project I'm working on I am required to have two USB connectors:

the first is used to provide data and power to only one IC of the board
the second is used to provide power only to everything else on the
board

Since the two USB connectors could be plugged to different sources (one to a PC for data transfer, one to a USB wallwart charger), what do I do with the grounds?

Should I tie them together or keep them separate?

My guts say to do the latter (keep the "data" ground away from the "power" ground, no touchy).


texts: How to power a portable project with multiple components?

texts:
I am working on a senior project and I have been tasked with the battery and power supply, and I am a newbie to power.

This will be an "iPad" sort of device, so ideally, we want a built-in battery that will power multiple components and have the ability to charge via wall outlet, or USB.

We have three main components to power: a touchscreen monitor (+12 VDC for backlight, +5 VDC for monitor), an FPGA (+7 - 15 VDC), and a microcontroller (+3.3 - 5 VDC). What is the best approach to this?


texts: Input resistance of a circuit containing op amps

texts:
For my first problem, I am trying to find the input resistance of the circuit itself, is it just simply the input voltage V1 minus the calculated voltage at the negative terminal of the upper left op-amp divided by 1k?

For my second problem, I'm trying to construct an op-amp circuit that produces an output corresponding to this formula with one summing amplifier and one differentiating amplifier, but the input impedance seen by both V1 and V2 must be 5k:

Any tips on how to proceed? I am a bit stuck on how to force the input impedance seen by the two voltages to be 5k.

Here is what I have come up with so far for the two separate op-amps. How can I combine them while forcing both input impedances seen by V1 and V2 to be 5k?


texts:
If I send 160bit message to an FPGA using TCP/IP
Do I need to store the message in BRAM first ?
Not sure how the FPGA receives data and gets to work on it yet.


texts: What use do these round pads have on PCB?

texts:
I always find these pads on boards:

What use do they have? Is there a specific connector for them or do you need to solder a wire on them?


texts: Are resistor networks appropriate for voltage divider?

texts:
I need to make 9 voltage dividers in order to connect 9 resistive sensors to the analog inputs of an Arduino board. I was tempted to use a 10K resistor network to individually ground the inputs but then I wondered whether this would in any way affect the sensitivity of the measurements or generate interferences between channels...
Any advice ?
Many thanks


texts:
I'm trying to make a project with keil uVision 5, for DA14580 (Dialog Semiconductor).
http://www.keil.com/dd/chip/6853.htm
But in Select Device dialog there's no device from Dialog Semiconductor.
The Question is: How can i start a Project with some selected mcu?
All examples that i can found is for TI microcontrollers or Atmel.

Also, Device missing from Pack Installer too:

The only information about the device that I'm looking at is in device database in File Menu:

I tried to "Add" the device but, when I'm creating new project for a specific Device, (Photo No1) I cann't find the device in the list.


texts:
I am asked this for homework:

I am trying to do nodal analysis for part A of the question but am running into problems with number of unknowns versus number equations. Assuming I chose my nodes correctly I get:

$$V_a = V_1 + \frac{V_a}{R_2} + \frac{V_a-V_b}{R_F} + \frac{V_a-V_x}{R_1} $$
$$V_b = V_2 + \frac{V_b-V_x}{R_3} + \frac{V_b-V_a}{R_F} + \frac{V_b}{R_4} $$

I don't believe my node equations are correct but I believe that there is 3 unknowns (Va, Vb, and Vx | V1, V2, all resistors are known(?) ) and only two equations. I tried super position as well treating each stage as an inverting and noninverting with sources on and off.

Any help or guidance on how to approach this problem so that I can reduce it down into the given form would be appreciated .

Note: Vref does not equal ground.


texts: Estimate RAM usage information of an embedded device

texts:
I'm monitoring the performance of an ARM-based embedded device which runs poky linux distro (from Yocto project) which contains OpenEmbedded build system. I need to get the MHz (CPU cycles) consumption and the RAM used for any process that runs on the system. Though top utility allows me to see the CPU % used (which allows me to estimate CPU MHz in turn), it just gives the virtual memory size (VSZ) used by the process but no physical memory used.

Is there a way I can get this information I need?


texts: What's the difference between small signal bipolar junction transistors (BJTs) marketed as switches vs. amplifiers?

texts:
For instance, the MMBT3904 and MMBT3906 BJTs are listed as NPN/PNP Switching Transistors, and the datasheets mention the switching times, while the BC846 and BC856 BJTs are listed as NPN/PNP general purpose transistors (and the switching speed would have to be deduced by looking at the transition frequency ft?)

Besides the obvious (higher ft for switching transistors): Is there a difference in the way these are designed and manufactured? Can one type generally be used in the other application, but not vice versa?

What about things like miller capacitance, linearity and noise?

Are there certain tricks in the geometry on the silicon, or concentration of dopants?

Related, for FETs: What's the difference between field-effect transistors (FETs) marketed as switches vs. amplifiers?


texts:
I am currently working on a project with a central controller which is always powered and a secondary which will be turned off if not needed to save power.

Now I wonder how to make sure, that there is never power on the signal lines which could power the secondary IC via the clamps.

I remember seeing some component, which allowed bidirectional transfer of data but would "break" the connection if the "ENABLE" input was low. Do you know what the name of this component is?

Thanks in advance.


texts: What resistor values should I use for a voltage divider that has to operate at low temperatures?

texts:
I'm designing a flight computer for a lightweight pico balloon - it will (hopefully) operate in the upper atmosphere down to around -40C. To keep the weight down, the whole thing is going to be operated off 1 AA battery with a charge pump. However, when reading the datasheet for the chosen charge pump (MCP16251), I spotted something I hadn't taken into consideration:

  When an application runs below -20C, smaller values for feedback resistors should be used to avoid any alteration of VOUT, because of the leakage path on PCBs. (Page 12, section 4.2.3.)

Choosing smaller resistor values is trivial, but I'm unsure of exactly what's happening here (why it's affected by temperature), and just how much smaller values I should choose than the examples they give in the datasheet (in the order of 1MOhm.)


texts:
I trying to find a solution for a problem that I have with a system I am responsible for. The system runs on radio control, the problem we had is one of the radios got stuck on transmit and blocked up the whole system. The solution I came up with that I believe will solve the problem involves a time delayed overcurrent protection system. The closed I could find to what I was looking for is a definite time overcurrent relay, the only problem with these is that I can find one that will operate in the voltage and current range I am looking for.

The radio operates from a 12Vdc source and draws about 25W when transmitting. What I want to do is detect when the current goes over 1A and then wait about 1 minute and then cut power to radio. It most also reset if the current draw goes bellow 1A inside the 1 minute window.

I have come up with a very basic design so far:

simulate this circuit – Schematic created using CircuitLab

If any one can think of a better solution please feel free. I am also looking for some through on what I can use to do the current detection.

Thanks in advance.


texts: Is JTAG the standard way to program ARM processors?

texts:
Some electrical engineer once told me, that each ARM M3 processor can be flashed the same way, no matter which manufacturer it came from.

I suppose he meant using JTAG, or is there another way?

Btw, I'm meaning to flash an empty ARM processor without a bootloader.


texts:
As the title suggests, I'd like to power a Dropcam without laying new wire in our community garden (code enforcement makes wiring a headache). When I wired my Raspberry Pi to work off solar power it was easy because I was only going to be using it in sunlight and if it turned off I would simply turn it back on. With the Dropcam, though, the intent to is to keep an eye on everything at night and weekends with as minimal interruption as possible.

After using my Pi setup as a base and reading this post, I'd like to confirm with you guys that something like the following is sufficient for my needs. Is it too much? Too little? I'm in Santa Monica, Ca so there's typically plenty of sun. According to the diagrams I've seen, this area gets about 6-6.5 sun hours daily, which seems more than enough to me to power a small USB device.

Specs on the Dropcam:

Input: 50/60Hz 0.5A
Output: 5V-2A
Wifi:  802.11b/g/n 2.4GHz (not sure if this has any influence)

Proposed setup:

12V/12aH deep cycle battery (e.g., this)
50 watt panel (e.g., this)
Charge controller (e.g., this)
Inverter (e.g., this)

Forgive me if this question has been answered. I've browsed the questions here and attempted the calculations, but it can be overwhelming for someone whose only experience with electrical products resulted in a zap or two ;)

Edit: I'm also open to any other suggestions! I'm not married to solar, so if there is a simpler, cheaper, or more viable solution feel free to share.

Cheers


texts: What does this AC power connector symbol mean?

texts:
I've seen this on the wall-facing side of many (North American) AC power connectors.

What is it called?
What does it mean?


texts: Effect on coil of two magnets moving in opposite direction

texts:
There is a coil of wire making up a closed circuit and two magnets. What would the effect be on the circuit if we simultaneously moved one magnet towards the coil and the other magnet away from the coil.

both magnets have their poles in the same direction.
the magnets have their poles in opposite directions.


texts: What is the use of NOT CONNECTED pin in 741 opamp?

texts:
When I attended a viva about the IC Applications, I was asked What is the use of NC pin in 741 opamp? so I answered as it just indicates no need of any connection to that pin in return I was asked then why this pin is placed? Unfortunately I didn't answer.

I researched about it and found that it is filler space from this article.

Is there anything else I didn't reached in this case?
and What is Filler space?


texts: What is the "RT" meaning in this circuit?

texts:
I am studying this circuit and found these Yellow components with labels with RT on the board. What is the component? I couldn't find the datasheet as well. The words on the components are ("U800",HLUB). Are they thermistor? But what is the purpose?

They connect between relay and positive terminal of battery.


texts:
Did you noticed that when holding a LED with bare fingers and connect it to a soldering iron(ac type) it gets a little bright.

I did it for other components to reduce their heat during the soldering. I need to know is it ok to hold IC (ex 74hc595, mcu's, ...) Pins with fingers or metal tools when their other pins are in touch with iron tip?

Is there any reverse current ? May it damage the chip ?


texts: Deep Discharged Primary Battery Pack Voltages

texts:
I deep discharged two 4 cell (2S2P) 7.2 V Lithium Thionyl Chloride battery packs each connected to a GPS tracker. I ran the two packs until each GPS tracker stopped communicating. (can't be certain what the cut-off voltage was).

After retrieving the packs I noticed three batteries in each pack had about 15 mV and one connected to the positive cable had the normal 3.6 V (circled in the picture). All fuses were intact.

Are these normal voltages for a deep discharged lithium battery pack? I expected all cells to still be 3.6 as they usually recover after normal discharge conditions with a cut off of about 2.5 V. And why has one cell in each pack recovered to its full voltage?

I'm trying to understand the principles of how a pack like this discharges.


texts:
I want to develop a general PID not for any specific appilications. What algoritham can be used to to so? ie If I dont have a specific plant model what algorithams can be used to tune a PID so that it will fit for different systems (temperature, pressure, flow, level etc..
)


texts: Calculating inductance of inductor that has ferrite core and a large air gap

texts:
I'm working on a coil on a PCB that will have a small ferrite core place in the center, with a large gap.

I'm trying to come up with a decent equation to estimate the inductance of this inductor.  I've found good equations for solenoids and other shapes of inductors, but all of them assume a single "ideal" core with one permeability.

How should I represent this type of core so I can use existing equations to calculate my inductance?  Should I look to a different method to estimate inductance?

E.g. one thought I had was to calculate an "average" core permeability based on how much area is ferrite and how much is air, and then use this average to represent a single ideal core.  But I'm not sure if that would be correct.


texts:
I want to measure output of a charger (MODEL: GB28-25126) with below picture:

When I connect my HIOKI multi-meter (3280-10F) to output of my charger in order to measure the resistance, it shows OF (OverFlow) at first and then starts decreasing until 5 mega Ohm. At 4 mega ohm it suddenly shows 4.5 kilo Ohm and starts increasing until 9.67 kilo ohm and then will remain constant. I have some questions:

What causes that behavior?
At last what is the output resistance of charger?
Above all, if I connect a 12V battery to the charger, the battery will be depleted by the charger when it is not connected to home electricity?


texts: Is it possible to use an accelerometer as a route finder?

texts:
I have an ESP8266 and an accelerometer (MPU6050.)

When I place the accelerometer with ESP8266 in my gadget, is it capable sensor to  draw the path of gadget travel (means to get the co-ordinates) when the gadget travels in a small area(some meters or kilometers )?

and also there any other sensors that place with in my gadget, for measuring the co ordinate in x,y,and z when device moves with distance?

The final graph drawn from these coordinate gives the path that device traveled.

Is it capable of doing with Accelerometer (eg:MPU6050)?

datasheet mpu6050


texts: What tools, equipment, and techniques do you use to solder fine-pitch SMT parts?

texts:
Possibly many questions have been asked on soldering smd parts, but I haven't found specific answers, Like:

Do you use a watchmakers lens or some other type of magnifying glass while soldering these miniature components? What would be most optimum to see a larger picture?
How do you solder components where pads lie beneath the package, I don't own a reflow oven and have tried to ignore these packages but can't do that anymore.
Are there any techniques to manually solder BGA, iLCC, CSP amongst others.
What tools do you use, apart from tweezers, soldering iron, solder wire, and a bright/ illuminated workplace. Any suitable "third hand" that you have found that makes a monster of a difference?
Is there a specific tip thickness to use for the soldering iron, what about the solder wire guage?
For prototyping if would not always be feasible to make a pcb, do you solder these components on a veroboard or do you buy a breakout board?

You could add more to these based on your experience and wisdom...

Your turn.


texts: What course of study is important for someone wanting to make analog audio equipment?

texts:
I do not have a background in electrical engineering. I do have experience building audio equipment from kits and I can build circuits from schematics diagrams.

What I would like to do is to be able to build more creatively. I don't think I will be able to do this without a more rigorous, abstract understanding of how audio signals are generated and manipulated in hardware though.

I would like to study some essential theory but I don't want to get an entire electrical engineering degree. What would be the most direct way to gain this knowledge? (a certain course, book recommendations, etc)


texts: Help on creating a USB Hub Switch that enables multiple computers to share USB device?

texts:
In the past year of working from home I grew tired of a ritual that I have to do every morning and every afternoon, the usb peripheral change.
I have tried different solutions multiple keyboards/mices/webcams but its a waste, keyboards and mouses that connect to different devices but this normally are good for work however not so good for my hobbies.
So I decided to look out for a usb switch that would meet my necessities, however I didn't found it or maybe I'm just searching for the wrong thing.
I grew to the conclusion then to search if it would be possible to make my own device with my requirements and who knows maybe help others out there that want to get rid of the extra peripherals and extra cables laying on top of their desks.
So I want to create a USB switch that enables 3 computers to share USB devices, such as keyboard, mouse, camera and other peripherals.

The switch will have 3 USB "output" ports that will be used to connect to 3 computers.
The switch will have 4 USB ports that will be shared by the 3 computers connected to the switch.
The switch will share by the 3 computers the information that the device X is connected, however only I push the button to switch the usb source to that output is when the computer will receive instructions from that device. The idea here is if I connect a mouse to the switch all 3 computers will know that a mouse is connect and ready to use however only the chosen computer will actually receive the data send by the mouse, avoiding this way extra awaiting time when switching a device between computers. This could be also done in another way where all usb are shared by the computers and I choose if some computer should not receive info from usb source port X.
The higher the usb specification the better, 3.1 would be ideal.
Dedicated power source.
Low latency, < 1ms.

The best scenario would be to create something that anyone at home with little knowledge could assemble in their homes, by using certain parts from user friendly providers such as arduino/adafruit.
Would be possible to put together something like this?
Edit:
Regarding the usb3.1 is not something that I'm looking forward to, just wanted to see if possible then other users that might be in need could use the knowledge I have gathered.
Kvm's seems like a possibility however they seem to introduce latency, it could work between computers where latency is not a problem, however I want to have the less delays possible between my personal computer.
Emulation is a field to discover, the reason I want all connected computers to have the a "ghost" from the connected device is because sometimes work computers have software where when you plug in any usb/hid device you have to go and accept it as a trusted device for the session, so every time I switched a device I would have to still do a lot of actions to make the device working on that pc. I assume that if the computer thought the device was always connected this will be a lot less hassle.
Thanks for your time reading this.
Best,


texts: I'm trying to find the the voltage across the capacitor before and after closing the switch and graph the response

texts:
This is the initial circuit

After some simplification the circuit changed into this

Then for solving the for the switch open I simplified even further

So For t=-0 -> ic(0)=0

Using mesh current analysis

                 72-15i-30i=0
                 30i-Vc(0)=0   Therefore, Vc(0)=48V

Now for the switch closed the circuit looks like this

I have tried using mesh current analysis but I always seem to have too many unknowns.

Can you help me with this?


texts:
When using a 2222 or 3904 NPN-type transistor to switch a simple LED, is it better to place it inline with the negative or positive rail of the load (LED)?

Also, which rail is best when working with darlington transistors or MOSFETs for high powered loads?


texts: RaspberryPi driven LED strip is flickering

texts:
Supplies:

LED Strip Please note I'm trying to power 28 of them. ~1400 mA
Power Supply for LEDs 5v/2A
Raspberry Pi
Breadboard
Microcontroller

I am following the adafruit for driving LEDs from the pi.

They suggest wiring it like this (this works great for me btw, no flickering):

This is how mine is wired:

I'm sure some eyesores jump out at you:

wiring color
melted squares from when my ground and power were touching D:
hot glue around the peripheral wires
crossing wires at the power supply adapter

I drew a sharpie line on the wires that are ground.
When I wired it according to the guide, that is, with a breadboard that has vertical running lines for power and ground, it works great!

But moving it over to this mini breadboard it starts flickering.
I tried  powering the led wires (circled in blue) with a wire that goes straight to the power supply adapter output (yellow wire), and it was a bit better, but not much.

So does the voltage really degrade that much with traveling across the board to my led strip connectors? Is the breadboard crap? Does having dedicated lines for power/ground make that big of a difference? Do I need a bigger power supply?

update

New bread board helped a lot with wiring the power in parallel. I grounded the unused inputs to the level shifter. I added a 1000uf 16v capacitor although a smaller one would have been fine. Also added a resistor as recommended by Neopixel guide. I bought a multimeter and can see that voltage drop is much lower and there is almost no flicker.

The little led just shows when my external supply is plugged in.


texts: Thermal reliefs for via-in-pad under BGA?

texts:
I'm doing the layout of a high-speed (Multi gigabit) system based on an FPGA with more than a thousand BGA pads and 0.8mm pitch on a 10-layer board. I'm using via in pads that will be copper-filled and capped.

My question is:

For such specs, is it required to add thermal reliefs to GND/PWR vias under the BGAs?

I've never added thermal reliefs for normal vias before and didn't face any manufacturing issues. Not sure if this applies to the current system or not.


texts: Verilog structural CORDIC implementation for sin/cos calculation

texts: Does anybody have a reference to an in depth explanation of hardware implementation of CORDIC algorithm for sine/cosine calculation? I'm looking for a way to model it in Verilog on structural level. I was able to do it on behavioral level, but when code got synthesized, I got way to many gates, so now I want to optimize the design by describing it structurally. I would appreciate any help.


texts: Dimensional Tolerance for US Standard NEMA 1-15 Plugs

texts:
I am trying to find the dimensional tolerance on US electrical plugs. I have tried looking online, but I have only been able to find that they are called NEMA 1-15, and have found the picture below showing length and height for the male connector (but not width of the male prong), and I haven't been able to find dimensional tolerances anywhere.

I ask here because I'm assuming there's a US code that governs electrical plugs, but I can't seem to find the standard anywhere.


texts: designing image debayer block, how should the testbench be written

texts: A debayer block inputs image from a CCD Bayer filter and then estimates the missing color information for each pixel. The data comes from a camera. How should one go about writing a testbench for something like this?


texts: Why doesn't current flow in the other loop?

texts:
I am just now learning about how transistors work, so please let me know if I have a misunderstanding.

I ran a simulation of the circuit drawn below, and the results were that current flowed only in the bottom loop (with the resistor and switch). When the switch is open, the current flows to the base, thus turning the transistor on (and allowing current to flow through the upper loop with the transistor).

However, my question is: when the switch is closed, why doesn't current flow to the base of the resistor? Can't it pass through the base and through the right side emitter (in NPN transistor), thus creating a sort of a "parallel" circuit?
Again, please forgive me if I have a misconception, and share your knowledge! :)


texts: By-Pass Capacitors for my SIM7600 Module

texts:
I am designing a PCB for SIM7600 module. I am stuck at choosing right capacitors for it. The datasheet (Page 21 & 22) specifies the load transient of the module. You can found load transient below:

According to my calculations (considering the power supply is unable to supply transient), the capacitor should supply 1.154 X 10^(-3) Coulomb charge in 577 us (I X dt = 2A X 577us).

To calculate the capacitor value, I have divided charge required by max. ripple voltage (=300mV). The capacitor value (dQ/dV) came out to be 3.84 X 10^(-3) Farad. But the datasheet requires 1000uF capacitor if power supply is unable to supply the load transient. Am I doing it right?

I think I should consider the ripple current of the capacitor and ESR of the capacitor. Should I be selecting capacitor having ripple current more than 2A?

I have calculated max ESR by considering voltage shouldn't drop by 300mV while supplying 2A current. The max ESR obtained from my calculations is 0.15 ohm (dV/dI = 300mV/2A).

Am I calculating it the right way?

EDIT:
I am using DC-DC regulator (AP6503). The load transient response of the regulator is:

It looks like my supply will be able to respond in a way that voltage deviation will be less than 300mV after 50 us of load transient. Do I need to use 50us time instead of 577us?


texts: What is this component and where can I find more details?

texts:
I would say it is some kind of transformer but it has the same wire girth on both primary and secondary windings and the same loops count.

It had the following label:

CLTE 250V, 0.5 A, 45 U, 2 × 500 uH
VDE

I need to know what it does. It is located between a capacitor and contacts that close the circuit

Additional info

It is part of a Pfaff 92 sewing machine pedal. Right between what looks like a capacitor / a group of them and contacts that gradually touch themselves and (with the help of some resistors, I guess) send current of different values to the motor (or maybe they do something else).

This little thing (the size of an AAA battery) had a short and I would like to replace or wrap new wire. That is what I need to know what it is before


texts: How much current does a capacitor draw when charging?

texts:
I'm using a large capacitor to buffer the load requirement of a solenoid (solar/battery operated setup, with solenoid kicking in a few times a day). Someone mentioned that if I use a large-enough capacitor, I need to put a resistor in series with it to moderate the "capacitive load" (a term I found out later has little to do with this situation).

So - how much current (theoretically) does a 3300uF electrolytic cap draw in a 12V circuit when it's first energized? (I realize the value drops off over time as the cap charges.)


texts: I have just started work with radars. I read that incoming signal in case of Doppler radar is frequency shifted. On adding it to original signal we get Doppler shift. But we don't do it directly. First we make I component (by mixing incoming signal with LO signal) then Q signal by mixing original signal with phase shifted LO then do I + jQ. This I understand is to determine the direction of motion either towards or away from Radar. I am attaching excerpt from book. Can anyone please explain how this one signal in each waveform becomes zero?


texts: Replacing a PC-mounted SMD microcontroller with headers

texts:
I purchased a PC board with lots of interesting  I/O that's being controlled by a single microcontroller in a 44-pin QFP package.  I'd like to access the I/O lines directly so I could hack in my own microcontroller,  but the footprint of the QFP package is too small (less than .05" lead spacing) for me to connect wires directly to the pads.  There are no larger pads anywhere on the PC board I can connect to.  Ideally, I'd mount some sort of  socket or header in place of the existing microcontroller, that I could then connect wires to.  The speeds aren't so fast that I need to worry about lead length.

There are obviously lots of prototyping boards for mounting an SMD that allow you to connect headers. What I ideally need is different... something that be soldered into an existing PCB footprint and gives access to the pads.  But I haven't been able to find resembling this!

Would love to hear any solutions-- I'd love to repurpose this board and give it some new life!


texts: Xilinx Virtex 6 Board - ISE gives error [Design Contains no instances]

texts:
I'm receiving a "design contains no instances" error  but I'm unable to find out the cause of the error despite Googling a lot and trying out the solutions suggested on forums. Below is a report summary for the design, any ideas?

WARNING:NgdBuild:578 - Design contains no instances.
=========================================================================
*                           Partition Report                            *
=========================================================================

Partition Implementation Status
-------------------------------

  No Partitions were found in this design.

-------------------------------

=========================================================================
*                            Design Summary                             *
=========================================================================

Clock Information:
------------------
No clock signals found in this design

Asynchronous Control Signals Information:
----------------------------------------
No asynchronous control signals found in this design

Timing Summary:
---------------
Speed Grade: -3

   Minimum period: No path found
   Minimum input arrival time before clock: No path found
   Maximum output required time after clock: No path found
   Maximum combinational path delay: No path found

=========================================================================

Process "Synthesize - XST" completed successfully

Started : "Translate".
Running ngdbuild...
Command Line: ngdbuild -intstyle ise -dd _ngo -nt timestamp -i -p xc6vlx240t-ff1156-3 "HCORDIC_Main.ngc" HCORDIC_Main.ngd

Command Line: /opt/Xilinx/14.7/ISE_DS/ISE/bin/lin64/unwrapped/ngdbuild -intstyle
ise -dd _ngo -nt timestamp -i -p xc6vlx240t-ff1156-3 HCORDIC_Main.ngc
HCORDIC_Main.ngd

Reading NGO file "/home/a/Downloads/Untitled
Folder/Multiplexer/HCORDIC_Main.ngc" ...
Loading design module "/home/a/Downloads/Untitled
Folder/Multiplexer/HCORDIC_Main.ngc"...
WARNING:NgdBuild:578 - Design contains no instances.
Gathering constraint information from source properties...
Done.

Resolving constraint associations...
Checking Constraint Associations...
Done...

Checking expanded design ...

Partition Implementation Status
-------------------------------

  No Partitions were found in this design.

-------------------------------

NGDBUILD Design Results Summary:
  Number of errors:     0
  Number of warnings:   1

Writing NGD file "HCORDIC_Main.ngd" ...
Total REAL time to NGDBUILD completion:  5 sec
Total CPU time to NGDBUILD completion:   4 sec

Writing NGDBUILD log file "HCORDIC_Main.bld"...

NGDBUILD done.

Process "Translate" completed successfully

Started : "Map".
Running map...
Command Line: map -intstyle ise -p xc6vlx240t-ff1156-3 -w -logic_opt off -ol high -t 1 -xt 0 -register_duplication off -r 4 -global_opt off -mt off -ir off -pr off -lc off -power off -o HCORDIC_Main_map.ncd HCORDIC_Main.ngd HCORDIC_Main.pcf
Using target part "6vlx240tff1156-3".
**ERROR:Map:116 - The design is empty.  No processing will be done.
ERROR:Map:52 - Problem encountered processing RPMs.**


texts: Correct way to choose resistors for load

texts:
I've come across two ways to determine which resistor value is needed for a load. The first one, which is always titled 'How to determine resistor value for an LED' says that you can use the formula:

$$V_{in} = input\ voltage$$
$$V_{l} = LED\ voltage$$
$$I_{l} = LED\ current$$
$$R = \frac{V_{in} - V_{l}}{I_{l}}$$

And I've also come across one that says to use resistors in series to add a voltage drop like this:

simulate this circuit – Schematic created using CircuitLab

And then use the formula:

$$V_{out} = V_{in} \cdot \frac{R2}{R1 + R1}$$

My final goal is an attempt to power the Raspberry Pi (5v 2.1A) with a 12v battery pack. So, could I just use a 3.3R resistor:

$$R = \frac{12 - 5}{2.1}$$
$$R = 3.333$$

Or do I need to use the second equation to drop the voltage? I'm just confused as to which method to use


texts: Does a car battery (or any power supply) push amperes or does a load pull it?

texts:
I know that a car battery can provide 1000amperes for starting while other components only need a few amperes to work. I thought that loads "ask" the battery for some electricity and the battery obliges.
I just recently bought USB ports that slot perfectly into one of the empty dashboard slots. They came with a glass fuse that was already blown.
I went and took out the blown fuse and closed the circuit to energize it (parallel connection to cigarette lighter | 15amp fuse.)
I thought I had a basic understanding of electricity in cars and that the USB port would never draw more power than what it needed. I just wanted to see those LEDs light up! and then it got fried instantly - it didn't even light up. I just smelled burned electronics.
I guess it didn't pull more than 15amperes because the cigarette lighter circuit was still working. But why did it fry itself after being energized? I know that the cigarette lighter circuit pretty much works as if it is directly connected to the battery(right??) - there's no electronics that regulates current on it right?
Am I wrong that in a car, the loads pull the amperes and that it is not the battery pushing it?
Did the USB port circuit pull too many amperes and fried itself, or did the battery push the amperes that the USB port circuit couldn't handle it?
I'm very confused because my 220V AC plug in water heater is just a hunk of metal and it doesn't pull 1000ampere from the wall.
So again, do loads pull the amperes, or do power supplies push it?


texts: I'm trying to design a capacitor discharge circuit for a hobby rocket launching system. In some cases we have long wire runs with multiple rockets so a CD circuit seemed the way to go. I'm trying to use an IGBT and the Avago ACPL-312U driver. What I didn't realize is that an IGBT can't be used as a high side switch. Is this correct? Can I get some suggestions on how I can configure the circuit to use the IGBT for switching 100 volts?


texts: Should we remove unconnected copper island among connected traces?

texts:
Currently designing a PCB I find out there are some copper island. I was wondering if we should better keep them or remove them and why ?

Is there any manufacturing risk of having those  ?


texts:
Can I 'write' on an existing E-Ink screen using an external electric field? I tried simply applying 12 V DC with two probes to a shard of a broken kindle display, which did not influence its shade in any way. Could moar power help?

About this E-Paper technology: https://en.wikipedia.org/wiki/E_Ink

On a semi-related note: How do E-Ink pigment particles retain their electrostatic charge?


texts: How much is the noise of a multiplexer for analog inputs?

texts:
I have 4 sensors, each have with two differential output (S- and S+) that I need to use in a differential amplifier (with a gain equals to 1000 in my case).

The difference between S- and S+ is between 0V and 5mV and I would like to have a 0.005mV precision.

As I want to used just one amplifier, I thought about using a multiplexer (like this CD4052BM96) before amplifying the signal, but I was wondering if the multiplexer's noise would allow or not a 0.005mV precision.

How can I calculate how much noise the multiplexer (CD4052BM96 for example) will add to my signal?

Thanks a lot.


texts: Collector current for common-emitter audio amplifier

texts:
Looking at building an audio amplifier; many good example circuits and example tutorials based on the below simple common emitter circuit.  All of them I have found so far help to size the biasing resistors and the collector and emitter resistor, along with the capacitors.  Using the rule of thumb for designing this style of amplifier of 1/2VCC at the output to the speaker, I would want a 12V drop across Rc.  However, all of the tutorials I have read assume the collector current and then size Rc based on the two known parameters.  I am struggling with what the collector current should be though.  If my speaker output is a known 8 ohm, 3 watt, can I size the collector current based on that load?  But some of the collector current will also flow through the transistor (KCL), so how do I control my load current?  Or does it not work that way and I can only control voltage gain across the amplifier?  Since power is dependent on both voltage and current, and taking the voltage at the collector to be 12V, I would have a current at the speaker of 1.5A, which equates to a power draw of 18 watts.  Obviously, I am not thinking about this correct.  So if I size everything around a max current below 3 watts (which would be 0.6A at 8 ohms), would that dictate my collector current?  But again, 0.6A would go to the speaker, but how much flows through the transistor?
I am okay with following the design "rules-of-thumb" for a CE amplifier for biasing, voltage gain, frequency response, etc.. but I am really struggling grasping this one part.  I could just make an assumption of 100 mA through the collector, but I would have to think that the collector current can be engineered, not assumed.

simulate this circuit – Schematic created using CircuitLab

Edit:  Let me try again, looking at this example question:
Common Emitter Audio Amplifier
1) How did the OP determine a collector current of 1.26 mA (24V/8k = 3mA, 12V/8k = 1.5 mA, 24V/11k = 2.2mA, 12V/11k = 1.1mA....)?
2) How much of that collector current would flow to the load?
Ultimately, I understand that a push-pull or class AB amplifier would work significantly better.  I am just trying to understand this first piece so I can analyze more complicated circuits better.


texts: Trace width & vias for PCB carrying 15vdc/1a

texts:
I am designing a PCB which includes a 3.3v circuit w/ a microcontroller than controls (via a relay) a higher voltage (max 15vdc, 1a) circuit. Is it OK to run that amount of current and amps on PCB traces/vias? Will I need to increase the width of the traces or something?

As a sidenote, I am new to PCB design and using Eagle. My trace with is listed as "0.016" without units - I assume this means 16mil?


texts: How many segments are permitted in CAT 6A cable run?

texts:
How many segments are permitted in an F/UTP CAT 6A cable run? Segment endpoints require peeling back the foil and untwisting the pairs, which I fear will affect data speeds. I heard that a cable run with a mixture of different cable CATegories will reduce to the speed of the slowest one. Will having so many segments, even if all are CAT 6A, keep compound-reducing the speed? Is the following run allowed and will it work at 10 Gbps, assuming cable, plugs, keystones, and couplers are all CAT 6A and shielded? (In each segment, besides the first, last, and the one with the coupler, I give the names of the endpoints.)

router
modular plug to modular plug (6 ft.)
female-female coupler
plug to plug (6 ft.)
keystone to keystone (12 ft., wall, plenum jacket)
Plug to plug (50 ft., attic, plenum jacket)
keystone to keystone (12 ft., wall, plenum jacket)
plug to plug (10 ft.)
computer

If this is unreliable, should segments 5 through 7 be consolidated into one keystone-to-keystone segment, even though that makes replacement much harder?

What is the maximum segment and length limit? Does length limit depend on number of segments and vice versa?

Will this work with PoE or PoE+ at those speeds or any speed (replace computer with PoE/PoE+ device and replace router with PoE/PoE+ injecting router)?


texts: Is it possible to induce few volts IMPULS over 10 m distance?

texts:
I'm currently learning about electromagnetism at college, so this question is on mine mind for a few weeks.

If we have on one side: 9 V battery, DC-DC converter to few kilovolts, capacitor, button, and small dimensions inductor L1 (no more than 5 cm diameter).

And on the other side at distance of 10 meters secondary inductor L2, simillar dimensions as primary, but thinner wire and more turns.

In schematic DC-DC converter is missing.

MAIN QUESTION: Is it possible to induce for example 3 V short impuls on the secondary inductor when we press button?

I tried to calculate it with Lenz law, but i didn't succeed, :/

Sub-Questions:

Does induced signal duration depends on resistance in series with capacitor?
If we have instead of inductor, resonat circuit, is it practically possible    that signal last for a few seconds?

Thank you for your answers.


texts: Is it possible to use my (3d printers 12V 20A power supply) in series with 12V unknown amperage pc power supply to gain at least 24V 20A for my printers new hotend?


texts: Nextion Display not updating data from Arduino

texts:
I am using an Arduino Mega to display the readings of 4 pots on a Nextion Display as well as store it in an SD Card with the time stamp. I keep getting

recvRetCommandFinished err

on the serial monitor and the display does not update with time.
I have attached my code below:
#include "Nextion.h"
#include <SPI.h>
#include <SD.h>
#include <Wire.h>
#include "RTClib.h"

RTC_DS1307 rtc;
char daysOfTheWeek[7][12] = {"Sunday","Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};

// Declare your Nextion objects - Example (page id = 0, component id = 1, component name = "b0")
NexText tDate = NexText(0, 1, "tDate");
NexText tPot1 = NexText(0, 6, "tPot1");
NexText tPot2 = NexText(0,7, "tPot2");
NexText tPot3 = NexText(0, 8, "tPot3");
NexText tPot4 = NexText(0, 9, "tPot4");

File myFile;

void setup(void) {
  Serial1.begin(9600);
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  if (! rtc.begin()) {
    Serial.println("Couldn't find RTC");
    while (1);
  }
  if (! rtc.isrunning()) {
    Serial.println("RTC is NOT running!");
    // following line sets the RTC to the date & time this sketch was compiled
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
    // This line sets the RTC with an explicit date & time, for example to set
    // January 21, 2014 at 3am you would call:
    //rtc.adjust(DateTime(2016, 11, 19, 19, 45, 0));   // <----------------------SET TIME AND DATE: YYYY,MM,DD,HH,MM,SS
  }
  delay(100);

  // You might need to change NexConfig.h file in your ITEADLIB_Arduino_Nextion folder
  // Set the baudrate which is for debug and communicate with Nextion screen
  nexInit();
  SPI.begin();
  int pot1 = 0;
  int pot2 = 0;
  int pot3 = 0;
  int pot4 = 0;

  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  Serial.print("Initializing SD card...");
  if (!SD.begin(53)) {
    Serial.println("initialization failed!");
    while (1);
  }
  Serial.println("initialization done.");

  // open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.
}

void loop(void) {
  myFile = SD.open("testpot1.csv", FILE_WRITE);
  // if the file opened okay, write to it:
  if (myFile) {
    Serial.print("Writing to testpot1.txt...");
    while(1) {
      DateTime now = rtc.now();
      myFile = SD.open("testpot1.csv ", FILE_WRITE);
      int pot1 = analogRead(A0);
      int pot2 = analogRead(A1);
      int pot3 = analogRead(A2);
      int pot4 = analogRead(A3);

      myFile.print(now.hour());
      myFile.print(":");
      myFile.print(now.minute());
      myFile.print(",");

      myFile.println(pot1);
      myFile.println(",");
      tPot1.setText(pot1);

      myFile.println(pot2);
      myFile.println(",");
      tPot2.setText(pot2);

      myFile.println(pot3);
      myFile.println(",");
      tPot3.setText(pot3);

      myFile.println(pot4);
      myFile.println(",");
      tPot4.setText(pot4);

      Serial.print(pot1);
      Serial.print(",");
      Serial.print(pot2);
      Serial.print(",");
      Serial.print(pot3);
      Serial.print(",");
      Serial.print(pot4);
      Serial.print(",");

      delay(2000);
      myFile.close();
    }
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }
}

How do I get the pot values on my display? Any help or tips would be helpful!


texts: Powering off USB - question about grounding

texts:
I have a female USB connector that I want to use to power a little piece of electronics I'm working on.

I have a USB cable plugged into a computer with the socket on the other end and I'm using my multimeter to test the voltage down the cable. When I place the multimeter prongs onto pin 1 (5vDC), and pin 4 (ground), I get a reading of ~5.04v, but as soon as I take the prong off the ground pin, the voltage stops. Does this mean when I solder the socket to my PCB, I need to ground pin4 somewhere to close the circuit?


texts:
I have a 12VDC load (up to 10A) that functions correctly down to 8VDC. Sometimes (frequency: many seconds max, many minutes typical) the power source has a very brief (few milliseconds) drop to 7V. Automotive environment, the drop is due to cranking.

I would like to avoid the device power-cycling and possibly crashing. The device is a RX/TX radio.

The first approach was to use a mosfet "ideal diode" in series with the power supply and a big capacitor across the input. However I failed to find a capacitor big enough that is also rated for automotive use (at least 16-18V).
I do not like the idea to put several super-caps in series, for all the complications that are needed to keep them balanced, charged, and the loss of capacitance due to series arrangement.

Another approach was to use the diode and some sort of battery. However I have concerns about the size of the resulting circuit and the lifespan of this solution.

The final idea I had was based on the fact I only need a voltage supplement to what is still given by the main power source. I came up with the following hypothetical circuit; please note that I am aware the mosfets won't work "floating" that way, at least not without some special components, but for now just see them as "isolated" DC switches.

The control circuit is not represented but, in the nominal state PowerIN>8V they would open switches 'A' Q3 and Q4 and close switches 'B' Q1 and Q2. This will allow to charge the cap (note: I know more work is needed there) while powering the load directly.

When input voltage goes below 8V switches 'A' Q3 and Q4 would close and switches 'B' Q1 and Q2 open, effectively placing the cap "above" the power input. A 10F, 2.7V supercap is quite cheap and should have enough charge to provide for the transient (again, I know the voltage regulator will have to be disabled or isolated).

Ideas and suggestions?

Circuit in the nominal, PowerIn > 8V state:

Circuit when PowerIn < 8V:


texts:
I'm building a TV Ambilight using a Raspberry Pi and 2812B LED strip. First draft schematic below.
Few questions:

I intend to keep the strip connected and bend them around the TV and solder power injection into all four sides. Should I cut the 5V trace (highlighted in yellow on the schematic zoom) where I'm adding power injection or leave them connected? What's the impact of this choice?
Is it safe to daisy chain a few 5 lead Wago connectors for the power distribution?
Similar to #2, is it safe to connect the resistor, capacitor, and inline fuses via Wago connectors?
I'm planning on using 4 amp slow blow fuses on the 3 amp sections and 6 amp slow blow fuses on the 5 amp sections - is this appropriately sized?
Is 18 AWG sufficient? I calculated the voltage drop and it's on the order of a few percent for the length of wire I'm running. I've read these LEDs exhibit the same brightness from ~4.2-5V
Any concerns with powering the Pi, HDMI-to-AV, and HDMI Splitter from the same power source as the LEDs?
Is the capacitor sizing and location sufficient/correct, or would you recommend adding a capacitor at each injection point?

Thank you!

Schematic Zoom on LEDs:


texts: Is there an alternative to Original Molex Crimp hand Tools?

texts:
I have used molex products before and i have been happy with them . Recently they introduced a new series called molex Nano-Fit , very interesting product until i saw there crimping tool marketing strategy :

2 separate tools for different wire diameter and it cost around 400$ each.

for 24 to 26 AWG
for 20 to 22 AWG

so i have to invest 800$ before even buying or using or testing a single connector which is a lot for me ( i donot have a mass production line and i sell in 10s to 100s of pieces)

Question : is there a way to get the crimping tools at much lower prices than digikey or mouser ?? is there a walk-around to crimping like soldering or using a universal crimper or piler ? is there Chinese copies for these tools for cheaper prices ?

any solution or idea is appreciated thanks in advance.


texts:
In layman terms, what does it mean that correlation function is being high between received signal and the code?

Does this mean that the received signal is compared against spreading codes and the one with most bits being equal to bits of received signal is used for despreading?


texts:
I'm looking into designing a custom board based on a Microchip / ATMEL SAM S70 or STM32F7 / STM32H7. The SAMS S70 appears to be the cheapest option and offers roughly the same as the ST competitors.

I'm now trying to figure out how much SDRAM I can attach to these MCUs.

The datasheet of the S70 does not specify what type of SDRAM (DDR2, DDR3) etc. it can handle. How do I know what memory chips are compatible?
Browsing through digitec, I noticed that almost all (?) 1G memory chips have 8 banks, which is more than the SAM S70 can handle (4 banks max). And all the chips that I found that offer 1G on 4 banks are DDR1 only. Is the amount of data per bank somehow limited?
Also I am unsure how much data the memory controller on the SAMS S70 can adress per bank (row / column adresses) and in total. If I read the datasheet correctly, the biggest address is 13 bits of row address, 11 bits of column address + 1 bit byte offset + 2 bit bank address, i.e. 27 address bits in total.. that would be 1/8 of 1G, i.e. 128M?
Where does Page size play into this?

I know that these are many questions but I am quite overwhelmed by the amount of memory configurations and the limited information in the datasheets doesn't help.


texts: Is it possible to measure a 433MHz RF Transceiver signal using a 100MHz Oscilloscope? At least to see if it is transmitting or not

texts: I'm generating a serial signal and feeding it to a 433MHz RF Transceiver and I want to know if the signal is at least being transported before I starting working on the receiving end.


texts: Lux sensors with max. operating temperature of 90-100 deg C?

texts:
For my project, I need to observe the lux inside a double-pane window. Last time, I used 'Adafruit TSL2561 Digital Luminosity/Lux/Light Sensor Breakout'* but its recommended maximum operating temperature is 70 deg C.

Since I will be placing this window under a solar simulation for about 30-45 minutes under Standard Test Conditions (1000 w/m2 at 25 deg C constantly) and, I need a sensor that can withstand and operate under 90 degrees happily (without degrading or causing weird results like negative lux vaules).

Are there such lux sensors?

Link to the previously used sensor: https://www.adafruit.com/product/439


texts: MOSFET H-Bridge Design - Capacitor/Diode/Resistor Selection

texts:
welcome to my first post!

I am designing a small 3-phase Brushless DC Electronic Speed Controller (ESC). The design utilizes 3 half bridges and a FAN7388 driver IC. The FAN7388 datasheet has a typical application circuit, but I am unsure of how to select the external passive components. I have highlighted those components in red and blue boxes. My explicit questions are:

1) How do I calculate the values required for the capacitors, resistors, and diodes that are highlighted?

2) What jargon is used to describe these components in this circuit? (ex, shunt resistor, flyback diodes, etc)

                            3-Phase Inverter stats:

BUK7K18-40E MOSFETS

Motor(MAX): 1.8A / 6.8W / 3.7V LiPo


texts: I'll soon be working with RF Power Supplies used to provide power to plasma generators and other systems. A 50 ohm resistive load is used. If I'm correct, in most cases matching impedance between RF supply and load will result in maximum power transfer. It is also a goal to reduce ghosting and reflective foldback (power reflected back into supply). Can someone with more knowledge on the subject explain the theory of how and why ghosting occurs in such a system and how reflective foldback is best minimized?


texts:
How can I sense the touch of a hand through a thick surface? I'm working on a device that has to be completely enclosed in a 1-2" thick wooden casing (or 1-3mm thick metal) due to design requirements, so no chance of pushbuttons.

I thought we could use capacitance touch sensing, but I don't know what will work.

Any ideas?


texts: 8~16 PDM digital microphone + what processing? = beamformer!

texts:
I am researching on a project about sound source beam-forming.

I'd like to build: 8~16 digital microphones into one 2D(circle)/3D(sphere) PCB to form an array with an equal separation of each mic 3cm ~ 5cm apart. After some processing and being able accurately locate the direction of a sound source.

My calculation on minimal sampling rate according to speed of sound. Simultaneous sampling mics at above > 96 kHz and > 8 bit at a precise timing manner should be mandate.

Due to I am a more Linux software guy to EE person, I have less knowledge + experience of choosing a right design among MPU / DSP / FPGA.

I can gather all data back via ethernet and processing on a PC or process on the unit. BUT:

I have some sampling concerns:

Existing auido codecs won't be able to 8-16 channels digital PDM mics on a single chip.
Bring in more than one audio codecs with multiple I2S bus can introduce non-uniform audio time delays which results huge error on final calculation.
I don't know how other device can accurately measure PDM other than an audio codec.

Anyone can discuss some design ideas and I will look into it and implements it ASAP.

The PDM microphones I will be using: Analog Device ADMP521 65dB SNR


texts: How to make a state space model of en electrical RLC-circuit?

texts:
I want to learn how to build a state space model of an electrical RLC-cicuit. I don't know how to do that. So I will try here and check if I have done it right.

Focusing on L1:

$$ L_1 \dot{I_1} = U - R_1 I_1 - U_{C1}$$

Kirchoffs first law:

$$ I_1 = C_1 \dot{U_{C1}} + \frac{U_{C1}}{R_2} + \frac{U_{C1}}{R_3}$$

Focusing on C1:
 $$ C_1 \dot{U_{C1}} = $$

And now I'm stuck! Is there a better way to solve this?


texts:
I am trying to build a simple RC rover (car with only two wheels).
On certain commands, I want it to rotate a specific number of degrees into a direction or another (don't want military precision). In other words, to change it's orientation by controlling the two wheels.

I wanted to use a cheap compass like this: https://www.pololu.com/product/2127 (LSM303D)
But I heard that it won't work inside buildings; my rover will be used inside.

But in my case, I don't want to know the current orientation of my car, I just want to rotate an exact number of degrees into a direction relative to current orientation (even if current orientation is wrong).

Will it work in my case?

Do I have any other options to play around?

PS: Another possibility would be to use stepper motors. But this method is not pretty accurate as the contact surface of wheels may be smooth.

What about a gyroscope?


texts: Can someone explain how this switched circuit charges and discharges the capacitor?

texts:
The switched circuit is above. I am trying to understand how the switch causes the capacitor to charge and discharge. Most of the examples I can find involve using a switch to connect a capacitor to a voltage source, charging it up until the voltage across the capacitor equals the source. Then a switch is used to isolate the capacitor from the source, discharging the capacitor.

This circuit is much more complicated than that. Does closing the switch cause the current to bypass the capacitor, discharging it?


texts:
I have a couple of Yuasa NPW36-12 12V 7.2Ah batteries from a phased out UPS unit. The batteries are barely one year old and have less than 100 charge cycles on them. I don't have a lead acid battery charger and thought I could whip something quick on perfboard using the LM317s I do have lying around. This is what I came up with:

Basically a constant current/voltage charger which works for other battery types. Input is 19V from a laptop brick charger (3.5A) and R1 is made up of 2 resistors in series, each with a rating of 10W. I aimed for something close to 14.7V on the output so that I can compensate for the drop on U2 and D1.

Now to my question:

Is this a viable solution for an overnight charge since I'm charging at about 0.1C?
Will it harm the batteries if left attached for longer periods of time?
Should I worry about gassing at V>14.2V?
Lastly, I saw one where only one LM317 is used in conjunction with a TL431 at the adjust pin. Would that be a better option? I can attach the image if relevant.


texts:
I'm designing a monitoring system for plants based on a lithium-ion battery and an ESP8266 (Adafruit Huzzah board). Due to the application, water may come in contact with the battery and/or electronics.

I'm considering a potting of the whole system except the usb connector for recharge purpose. The curing is producing heat than cannot create problems with the electronics/battery.

I found polyurethane based product : Electrolube UR5634RP250G (Farnell : 2476085).
Do you advice this kind of solution ?

If you have cheaper solution, that could be nice too ;)

What about the thermal dissipation ? Are those kind of product corrosive for electronics ?


texts: Is this possible to make a module with both castellations and LGA?

texts:
I am trying to decide on a pinout methodology for a module that will be assembled board to board on a bigger PCB.

considering the pros and cons of LGA vs. castellations(cut half vias), i was thinking of combining the two - using a small amount of castellation pins and a bigger amount of LGA's, so the user could choose if to use only some features (with easier assembly line) with only the castellations or to use the full features by connecting both castellations / LGA's.

is this mechanically possible? does the assembly process of one negates the other in some way? (height, heat, etc..)

I would very much like some opinions/suggestions on this matter.


texts:
I have been studying the following schematic.

Those NMOSes are depletion type. I am not sure why they are needed in this. Why not just connect SCL and SDA busses together without a MOSFET? What purpose do the mosfets serve here?


texts: Hole size and Diameter for vías between layer

texts:
I have a simple question I think...
In my Design of PCB for standard parameters I need to have a trace of 1.5mm for power supply 4.7V 2A but I don’t know HOW to use vias here. What hole size and diameter I need to keep 1.5mm trace between top and bottom layer?

This is my actual trace and vias


texts: Control power to load by turning on/off regulator or by using a transistor

texts:
I am working on a project that involves a load that draws a little over 16A at 3.6VDC and it needs to turn on and off at 10Hz ~ 15Hz for 5~10 seconds at a time. I plan on using an arduino to control the circuit.

I have decided on a regulator to provide the steady voltage that can handle 20A, a TPS53353.

My question is, would it work to turn the regulator on and off using the arduino to provide the intermittent power to the load or would it be better to leave the regulator on and use a separate transistor to turn the load on and off using the arduino.


texts:
I have this homework that I need to justify power fluctuations on electronic devices. I had this idea (though don't know if it is right) that such fluctuations/spikes affect the operation/stability of an IC/sensor.

Am I thinking right that if i have a single power source coming from a +3.3v voltage regulator (amperage output is close enough on the total needs of what are connected to it) and this supplies some 4 pcs of sensors, 6 different IC drivers (differential, encoders, dmx, etc), 1 ESP8266 module.

3v3 300mA voltage regulator
50mA - 4 sensors consumes
50mA - 6 different ic drivers consumes
220mA - wifi module consumes

I have the following questions:

Do the 4 sensors or some of it would not work properly (output value not accurate) if all of this run at the same time/one at a time at microspeed by a microcontroller?
Would it be better to isolate the voltage supplies of sensors like putting them on a different voltage regulator?
Would the voltage regulator just for the sensors be switching
regulator or normal linear regulators?
I read that switching regulators are efficient but produces high noises, does that affect the output of the sensors and how?


texts: How to connect one pin to ground when an another analog pin is triggered

texts:
I'm trying to combine two working electronics projects into one. I have a standalone piezo sensor that I can read values from when it vibrates via an arduino, and I have a standalone audio board (no arduino needed) that will play a sound file when you connect one of its pins to ground (currently via a push button).

This is the basic setup for the audio board

and this is the basic setup for the piezo / button

What I want to do is remove the need for the button to trigger sound files, and instead use the vibration from the piezo to trigger a song to play.

The sound board is set up to play a track when you connect one of its pins to ground. It has a built in pullup resistor. With the piezo, I have code executing so that, if the vibration is over a certain value, it will trigger a function to play the sound:

if (piezoV > 0.1){ //play sound }

What do I need to from a wiring & code perspective to make the piezo play the sound? What I tried was setting up one of the arduino pins to do a digital write:

const int SOUND_PIN = 2; //Trigger Sound Board
void setup() {
  pinMode(LED_PIN, OUTPUT);
  pinMode(SOUND_PIN, OUTPUT);
}

void loop() {
  int piezoADC = analogRead(PIEZO_PIN);
  float piezoV = piezoADC / 1023.0;
  if (piezoV > 0.1){
    playSound();
    delay(5000);
    stopSound();
  }
}

void playSound(){
  digitalWrite(SOUND_PIN, HIGH);
}

void stopSound(){
  digitalWrite(SOUND_PIN, LOW);
}

Then I figured I could connect a wire from the arduino's pin 2 to the sound board's ground, and a wire from the sound board's ground to its own pin 1 (to play track 1) - but it seems like, whether there's vibration or not, when I do that the sound plays unconditionally.

WIRING:

Wiring setup to play audio with a button:

If anyone can point me in the right direction I'd appreciate it!


texts: Schematic for a lipo battery bleeder overcharge protector

texts:
OK, so I am building a 12v (really 11.1v) 10000mah lipo battery. I am going to use it on campouts to run things like 12v fans and car chargers and run other high-current devices that couldn't be run off of USB. Here is the problem I now have, how do I charge the battery?

My goal is I want to integrate the charger directly into the device and I want to be able to charge the lipo battery at 4-5 amps from a simple 12v DC power supply. This automatically rules out using using a simple 3S lipo charger from ebay because those can only charge up to ~1A. This also eliminates using something like an imax B6 because I want to be able to integrate the charger into the device, and an imax b6 is too big. Therefore I have decided I am going to design a DIY lipo charger.

The basic idea is this. I feed the entire lipo battery pack a CC/CV DC source (I will probably use a pre-built boost converter from amazon or ebay to do this) to charge up the battery to 12.6v. Then I use three discrete balancer circuits attached to each series lipo cell to simply "bleed" the battery down until it reaches back to 4.2v. Here is a terribly drawn block diagram:

As far as the balance circuit goes, I plan to use the TL431 shunt regulator from texas instruments to act as the IC for bleeding the cells down.
Here is a scematic I have designed based on the high current shunt regulator noted in the devices datasheet ( if you google the datasheet go to page 26).

Here is the circuit I have designed:

Here is how the circuit is supposed to work. The TL431 has an internal reference voltage of 2.5v. So if I feed at least 4.2v into the TL431 circuit the restive divider will drop it down to 2.5v, the TL431 will then turn on and power a PNP power transistor (the TL431 has a max current of 100ma) that will then short a 22 ohm 5 watt power resistor that will draw around 200ma from the battery. I also included an LED in the circuit so I can know when an individual cell is being balanced (on another note, this is yet another reason why I didn't want to go out and buy a pre-made BMS or charger, because rarely do they come with indicator LEDs of any sort). If the cell goes below 4.2v, the TL431 will see less than 2.5v on the resistor divider, and therefore the TL431 will turn the power transistor in the circuit off, stopping the balance charging.

In my circuit the 3.3K, 1.5K and 1K trim pot are there to form a 2.5v resistor divider (the pot is there so I can fine-tune the trigger voltage). The 680 ohm resistor is only there because the datasheet said it had to be there. I have no idea what this resistor does so I chose a 680 ohm resistor for it and by the way I would love to know). The 220 ohm resistor is for the LED and the 22 ohm power resistor is there to be the dummy load to drain the battery.

Here are my questions I have:

Will this circuit work at all?
Can I substitute the PNP power transistor for a MOSFET and if so, which kind?
Are my resistor values correct?

If you read all this all I have to say is you are the real MVP. Anyway any help would be appreciated.

EDIT: as many of you have mentioned the resistor divider will draw under 1ma even when the battery is not being balanced. To solve this issue I have decided to use 4pdt switch to simultaneously cut off the balance circuits from the battery and cut off the battery from being charged. Unfortunently after checking the data sheet the reference current for the tl431 needs to be between 0.05ma and 10ma (so the resistors in the divider can only be so high) so that is why I chose those resistor values


texts: Difference between half stepping and full stepping

texts:
I am currently making a stepper motor controller based on this schematic

however I was wondering about the difference between half and full stepping and what would be the best method for a stepper motor in a CNC machine.


texts:
When reading about 74HC161 synchronous counter, I understood almost everything except how the carry look ahead logic works. As far as I can see, when the counter reaches 1111, the TC pin is set to 1 for a certain amount of time. How does that help in n-bit cascading and what is the purpose of the carry look ahead in general? Thanks!

http://pdf1.alldatasheet.com/datasheet-pdf/view/15545/PHILIPS/74HC161.html


texts: Can I use a power supply with the same voltage but a different amperage?

texts:
I have an old router with a 12v 1.5a rating, and its power supply died so I'm using a 12v 1.2a power supply.

I have a MIDI keyboard with a 9V 500mA rating and I have a 9V 200mA power supply and one with a 9V 1A rating.

If I don't have the exact amperage, should I use higher or lower?


texts: Comparing and adding numbers using multiplexers and comparators

texts: Supposing I have been given three two bit numbers, a1a0,b1b0,c1c0 then what is the best way to design a circuit that gets the largest two of the three and adds them?


texts: collapsing solenoid magnetic field limiter

texts:
solenoid= 4 ohms , control power= 12-15VDC , NO switch is limited to 3-4 amps or what i call as limit ability . this miniature switch is my concern of welding contacts on release .

Thank you for your advise advise


texts: factors influencing capacitance of a cable

texts:
I am out of my depth here so I am looking for a simple explanation. If you have twisted pair cables of differing makeup, varying in conductive material, diameter of the conductor, number of twists per meter and number of pairs in the cable. What if any effect the pairs capacitance.

This is in the sphere of telecoms.

EDIT:

C = (EoErA)/d

capacitance seems to be based on “Permittivity” which is a function of conductivity which would imply that it will differ by from copper to aluminium.

also the area of the conductor, so that conductors with a larger surface area have more capacitance.

and lastly the insulator and distance between the conductors will play a role.

Are there any effects that I am missing? does the number of pairs around the one tested make any difference?

EDIT:
I seem to have misunderstood Permittivity it seems to be only to do with the insulator not the conductor.


texts: How to detect RF / Wifi radio device nearby

texts:
I wonder if there is a way to detect if there is any RF/WiFi radio ON nearby?

I'm configuring an ESP8266 12E module in STATION MODE (not Access Point) to connect to a Wifi network (any Wifi network). So, no problem. However, there is a situation which I'll have to turn off the ESP8266 module's radio (turn it off the radio only ... I'm not talking about disconnecting from the Wi-Fi network).

I already have the code that supposedly turns off the Wifi module ESP8266, which is the one that follows below and seems to work fine:

WiFi.mode (WIFI_OFF);
delay (1);

I just need to know if the radio really turned off, because I have a system in which there are 40 ESP8266 modules operating side by side, connected to the WiFi network and all these radios together are generating so strong interference to each other. When executing the Wifi shutdown code of the module(s), I just want to know whether there was none left without executing the shutdown.

Does anyone know how to detect a simple RF device?


texts:
I found these at the entrance of an analog input, so I think these are ferrite beads with a metal ground case but I need the part number. I searched several component websites but I couldn't figure it out (Mouser, Digikey, Farnell). I checked the manual and it doesn't have a schematic or BOM.

I have found that the case is connected to ground with a series resistance of 0.4 ohm. The inductance is 6uH and the IC on the right is an AD7190.


texts: How do I see if an op-amp is rail to rail using only datasheet?

texts:
If I have a data sheet or part of it, how can I see if an op-amp is rail-to-rail using only the numbers?

For example, only using the image below, how can I see if input and/or output is rail-to-rail?


texts: How to simulate two 12W lightbulb in series to 220VAC?

texts:
How can I simulate two lightbulb of 12Watts in SPICE?

In proteus simulation, there is only a lamp of adjustable nominal voltage and resistance. The default is 12V nominal and 24ohms resistance. If I want to simulate two light bulbs(12W) in series to 220VAC, am I correct to not change the nominal of 12V and adjust the resistance to:

$$R= \frac{(220V/\sqrt2)^2}{12W}=2k\Omega$$
And since there are two bulbs, the total resistance is 4kohms ?

OR

Since, two light bulbs of 12 Watts each will draw 24 Watts in total, the resistance is:

$$R=\frac{(220V/\sqrt2)^2}{24W}=1k\Omega$$

Which of the two resistance will be correct in simulating two 12Watts lightbulb in series?


texts: Specifying BOM substitutions / alternatives with Contract Manufacturer (CM)

texts:
I fear this question may be opinion based but I think it has some value to the general community - because this falls into the end of the design phase.

When working with a CM, they may have better pricing due their volume and as a design method, should you allow the CM to make changes to the BOM (provided you specify which components may be substituted) or is it industry practice to allow specify the components and alternatives and that's it ?


texts:
I recently purchased some of these: Digi-Key Banana Jack. Unfortunately, I'm new and there isn't the supporting documentation I need to be able to determine how they're to be used.

Unlike other banana jacks, there is not a hole to feed the wire through and screw down on. I understand the large nut is for holding it against the enclosure, but I don't know what the intention is with the threaded bottom section and the two nuts. I'm guessing that the wire is simply looped around and a nut is tightened down against it, but this doesn't seem very durable. Why the double nuts, what is supposed to be done with them?

Edit
To clarify, I understand that they are the female piece of a banana connector. I have male banana connectors that I am using these with. My lack of understanding comes from how to wire this female piece to the... for lack of a better word "connection wire". I.e. how to wire this female portion into a circuit so that the circuit is accessible through it.


texts: Cadsoft Eagle Library: How to create device variant?

texts:
I'm creating a custom device in Eagle Library.
Generally I need two device, let's say they're CONN2.54_1 and CONN2.54_2.
These two devices are connectors, they both have 4 pins, thus they have the same symbol. The difference is the package, one is vertical mount and one is horizontal.

Now I can create 2 separate device successfully. However I want to know how to group them under one "sub-category" in the Library?

For example: when I use the add button in the Schematic Editor, my custom Library should appear like:

MY_LIBRARY\           (This is the main library)

  CONN2.54\       (There's a sub-folder name CONN2.54)

      CONN2.54_1  (The first device is inside the sub-category)
      CONN2.54_2  (The second device is also inside the sub-category)

Thank you!


texts: Why does voltage change with load in buck/boost converters?

texts:
I recently learned about buck and boost converters. Both are switched-mode power supplies. Until recently, I had the impression that the duty cycle and input voltage determine the output voltage for both types of converters. For example, wikipedia states that Vout / Vin = 1 / (1 - D), where D is the duty cycle. This formula assumes that all components are ideal (in particular, the resistance of the inductor is neglected). I assume that this is an oversimplification that causes a discrepancy with reality. Likewise, in a buck converter I would expect the output voltage to equal the duty cycle times the input voltage.

In practice, most converters use a voltage divider and feedback mechanism to ensure that the voltage stays constant when the load changes. Why is this necessary? What mechanism causes the voltage to change when the load changes?


texts: Problem with powering a high and lower power circuit

texts:
I have a problem with the following circuit.

simulate this circuit – Schematic created using CircuitLab
I try to turn on a normal 120V light bulb controlled by a relay activated by a low power circuit which I energize with a cell phone charger of 5V connected to the same power supply of the light bulb. The low power circuit is an infrared sensor of movement and a transistor that allows current pass trough the relay when a movement is detected. This circuit works when I use a battery instead of the cellphone charger, but when I use the charger it doesn't. I do not know what is happening. Any idea?


texts: What sets the source voltage in this simple CMOS circuit if the current source is 0A?

texts:
In the circuit below, what sets the voltage at the source of the NMOS if the current source is set to 0A?

simulate this circuit – Schematic created using CircuitLab

If I run the circuit through ngspice and do a DC sweep of the current source value, I get a defined voltage at X for 0 current.

This is as far as my reasoning gets:

The current source is drawing no current.
The backgate is grounded so there's enough of a voltage to form a channel, even though the source is floating.
There's no current drawn through the channel as there's nowhere for it to go, so it can't cause a voltage drop.

Misc notes:

The current source looks like an infinite resistance in the small-signal model, effectively floating the source connection.
NMOS is diode-connected, so should be in the active region if \$V_{gs}\$ exceeds the threshold voltage.
I don't have a discrete NMOS with a backgate connection to try it on the bench.

I suspect the backgate or maybe some other leakage current.

Is this voltage real, or is it some artifact of the modelling?

[* Razavi, 1st edition(?), example 2.8]

Update

I ran a transient analysis as suggested below, but \$V_{X}\$ still
remains below \$V_{DD}\$ near time zero. I'm strongly suspecting
leakage currents now...

I've also plotted the backgate current: ~9pA around time zero (not shown). This seems like a puny current to produce that voltage drop.


texts: pros and cons of replacing a passive inductor by a gyrator

texts:
I am studying the construction of some touch sensors, and I need inductances of 10mH, I know I can easily do it, and also purchase them without much difficulty, however I know that it is possible to simulate such inductances using a circuit called Gyrator.

What would be the pros and cons of replacing a passive inductor by a simulated inductor with Gyrator.


texts: How to get a variable voltage from a variable resistor

texts:
Up front, I need to declare my ignorance of electronics. I'm first and foremost a scientist/programmer, but I'm constructing a device that will allow me to control voltage to an I/O board using hand movements. I may well use the incorrect terms in this post!

I'm constructing a device that will allow me to control voltage to an I/O board using hand movements. I'm trying to get (what I think is) a variable resistor to deliver between 0 and 5 volts (or thereabouts), which will be fed into the analog channel of an I/O board (specifically, a Velleman VM110N).

I can generate a voltage using a Thurlby PL320.

The variable resistor looks like this:

And this is the Velleman I/O board that I ultimately will be sending the voltage into:

I haven't yet gotten as far as delivering the voltage to the I/O board, as I want to make sure I've got the right voltage coming out of the resistor. As a complete novice, what I can't work out is what I need to do to get the position of the slider on the resistor to affect the output voltage. There are four terminals on the resistor: on one side, I have a black and a red, and on the other side, I have a black and a green-yellow (I am at least savvy enough to recognise that this is the earth terminal).

I've put a multimeter into the circuit, and turned the dial to 'DCV 20', which displays 5.00 volts (which is close to what I've set to be generated by the Thurlby PL320 unit - I'm assuming it's a little old and doesn't deliver quite what it says it will, but it seems to be consistently a little higher than it should be). However, adjusting the slider on the resistor doesn't seem to affect the voltage at all. From my very limited knowledge, I'm sure that adjusting resistance ought to affect the voltage (volts = amps * resistance). So, I suspect I'm either delivering the wrong voltage in the first place, or I've got the wires in the wrong terminals. Here's what I'm delivering from the Thurlby unit:

And, I've pretty much tried every combination of plugging the wires into the resistor, which either results in nothing or 5 volts, which doesn't change when I shift the slider.

Edit: @SomeHardwareGuy has helped me to understand that what I have is a linear potentiometer; not a variable resistor. Of the four ports on the device, I can plug one end of a multimeter into the (only) red port, and I can plug the other end into either of the black ports - there is a black one on each side of the device. Using the instructions given by @WhatRoughBeast below, I have found a way to wire the system up and produce a different behaviour... Now, when I adjust the slider, the voltage displayed on the Thurlby goes from zero to 1.15, but this behaviour is abolished if I flick the switch at the bottom right of the Thurlby to 'on'. I'm guessing this is switching to AC. However, even though I seem to be able to change the value on the input device, I still can't get the voltage reading in the multimeter to change...


texts: Adding 2 cooling fans to an amplifier circuit board

texts:
simulate this circuit – Schematic created using CircuitLab

I'd like to add (2) 5v .41A cooling fans to this Vox bass amp.  What Resistor/capacitor combo (R3/C4) would be best?


texts: Please explain FFT Frequency Spectrum and different filters

texts:
It seems that I am not able to find the right key-words in order to get the answers from google but how can I recognize different filters based on their FFT Frequency Spectrum and how do different filter look like in their FFT Frequency Spectrum?

I understand that the FFT represents a signal as a spectrum of its frequencies but I don't really know how to interpret a Frequency Spectrum plot of a FFT. I don't know how different filters would look like such as high-pass, low-pass and band-pass filters.

Could somebody explain and/or link me to some resources that could explain that to me? Please understand that I don't need a deep mathematical explanation I just need to be able to interpret and distinguish different FFT FS plots.

Thank you!

For example:


texts:
In my project with IMXRT1062 CPU, I have 512mbit SDRAM (IS42SM16320E-75BLI 32Mx16 structure). But I need to have more SDRAM memory (1024mbit), so I need to add another SDRAM chip. CPU has 16bit data bus and up to 512Mb per Chip Select.
My question is: to achieve 1024mbit from two 512mbit ram chips, I need to share (connect) every signal (adress/data/BA/RAS/CAS/WE/LDQM/UDQM/CLK/CKE) between two RAM chips? And connect CS signals independently to CPU from each ram?