texts: SCR circuit falsely triggered during capacitor charging

texts:
I am building a coil gun. Above is the complete schematic of the voltage boost circuit plus the trigger circuit.

Not shown in the schematic, there is a push button switch between the regulated +9V and the Vcc of the 555. When the switch is pressed, the capacitor bank begins charging.

On the other side, I have a microcontroller supplying a 5V pulse to a 4N25 optocoupler. The microcontroller ground is isolated from the ground of the coil gun circuit. When triggered, Q3's base is pulled towards ground which supplies current to the gate of the SCR, turning it on. D1 is used as a flyback diode to prevent reverse charging of the capacitor bank when the SCR turns off.

An important point: before firing, I disconnect the charging circuit from the capacitor bank to prevent the battery from discharging through the SCR.

My Problem

I run into trouble when I charge the capacitor bank with the coil and trigger circuit connected. The gate of the SCR is triggered immediately, causing everything to heat up quite fast.

I have the boost converter circuit soldered onto a piece of protoboard, but the triggering side of the circuit is breadboarded. The wire running to the gate of the SCR is about 6" long. I know there is a lot of EMI generated by the boost converter, but I'm not sure if that's the issue or something stupid I'm doing.

What I Have Tried

I've tried adding a shunt capacitor between the gate and cathode of the SCR. Did not work.
I've tried reducing the SCR gate-cathode resistance. Did not work.
Even with the SCR gate grounded, the circuit still triggers. Does this mean that I am forward-voltage or dv/dt triggering the SCR?

Update

Doesn't look like I'm getting many responses on this, but I'd like to update that I solved the issue by removing the triggering mechanisms from the breadboard and soldering them onto the PCB. I also shortened all the wires significantly and added a 10uF capacitor across the gate and cathode of the SCR. This seems to have solved the issue for now...


texts: I use iron to transfer toner to the copper board, and have been using laser printer. I saw some discussion on the net that it is also possible to use use ink printer if the ink is a good quality. I have a HP inkjet printer and use original cartridges. Could someone explain if (how) it is possible to use the ink on the toner transfer?


texts: Communication between AVR and CORUS PTZ device

texts:
12 NULL bytes are being sent to CORUS device (to power on it) with this codevision code like

putchar('\0');

Sending is ok , but regarding to page 9 of the CORUS protocol doc, the device should respond with only 3 Null bytes but it also sends different values afterwards, e.g one time 114 064, another time 255 251, and so on.

12 volts is used for the RS232 power supply, as specified on page 15 of the user guide.  We've tried connecting directly both from a PC serial port and FT232R/MAX232, with the same results.  Normally this would be used with an ISB to electrically isolate the signal.

Why doesn't the device respond with only three NULL bytes?

Alternative links: protocol guide


texts:
I am working on a project in which I am powering several 20 ma LEDs off of a 12 volt supply. I therefore need a 470 ohm resistor. The only problem is I don't know how many LEDs I will need. I know that powering say, 4 leds in parallel off of one resistor is a bad idea because of potential current differences, but if all the LEDs come in the same package from an online order, does that mean it would be safer at least?

http://www.amazon.com/gp/product/B007SJ8XP0?psc=1&redirect=true&ref_=ox_sc_act_title_2&smid=A3AGVPZHIH41EE


texts: FITS in reliablity. How to convert number of failures in actual hardware testing to MTBF

texts:
In the following post

What are FIT's and how they used in reliability calculations?

Barry stated "There are standard formulas that convert the number of failures in a given test time to MTBF for a selected confidence level".  Can you guide me to these specific formulas references etc.?  In other words I want to test actual hardware and derive reliability (MTBF etc.) from actual tests.  I already understand what Barry wrote in his 1.67 million hours mtbf example.


texts: PIC16F57 - problem implementing wake up signal on key stroke

texts:
I have designed a simple RC5 remote control using a PIC16F57 and the classic rows-columns scan over a 4x4 matrix keypad.

The previous version of my firmware continuously scanned the keypad to find a keystroke but the batteries consumption was to high (obviously).

Now I'm trying to implement a wake up system in which the micro sleeps all the time and wakes up only when the user press a key on the matrix. The problem is that the 16F57 can only wake up on 1) low logic level on MCLR or 2) watch-dog timeout. The latter could be feasible but it would imply polling the keypad every, let's say, 100msec. The first solution is the best but I couldn't make it work.

The solution was addressed here: http://www.t-es-t.hu/download/microchip/an528d.pdf
It's an official Microchip document so it should work. However I implemented the circuit and it doesn't work. The micro goes sleep but doesn't wake up (all the scanning lines are at logic level low before going sleep so they should discharge the capacitor).

The proposed solution uses a 47K resistor to pull-up the MCLR pin but in the official datasheet of the 16F57 they recommend a <40K resistor for correct usage. I tried to use a 47K and the pic didn't start so, thinking of a typo, I used a 4.7K which resulted ok to start the pic (although it didn't solve the wake-up problem).

The voltage across the capacitor should drop to a near zero to trigger the MCLR pin and cause a wake up but it seems that the scanning line, even at a logic zero, can't discharge the capacitor.

Do u have any clues how to solve the issue?
thank you!

P.S. the capacitor in the schematic doesn't have the "+" sign so I assume they want a non-electrolytic capacitor.


texts: Now I am sure that most people have read discussions on the possible hazards of handling solder and how your supposed to wash your hands after handling it. My question is, after soldering something, does the composition of the solder change at all? Does the rapid heating/melting and then re-cooling of the solder change it's chemical composition, possibly making it less "toxic"? Otherwise, shouldn't handling PCBs with solder on them carry the same hazards as handling solder wire?


texts: Can DE2-115 handle more than 3.3V on its GPIO

texts: In my current project I want to connect some logic to Altera DE2-115 using 40-pin exapnsion header (JP5). Unfortunately, I can't ensure that I won't exceed 3.3V on input port (i.e. I'll have ~4V). Is DE2-115 somehow protected against such situation? Are RN21 and RN23 such protection? Or do I need to put in some extra effort to provide stable 3.3V?


texts: IR Emitter/Detector with 555 timer alarm

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I have this circuit that detects when a tube is empty and pulses a piezo buzzer in .5 second intervals.  I have it working with 5v on a breadboard, but I need to move it to 12v from a wall wart.

Firstly, is there anything particularly wrong with the circuit?

Secondly, with 12v R1 should be 220 1W, but I want to stick with 1/4W resistors, maybe 510.  Is that possible?  I realize that will bring down the 50ma current to QEE113 to 22mA, but my distance is only 1" so I think it will be enough power.

Edit: I changed R1 to 150 which should confirm that it will work with about 22mA

Thridly, I'm not sure how to calculate the size of resistors needed to go to the transistors.  The values I have are from various samples I found on the net for 5v.  Is there a formula that tells me what they need to be for 12v.  I'm not able figure that out from the datasheets.

Q2 should actually be a 2N2907.

simulate this circuit – Schematic created using CircuitLab


texts: Will a14mm DC barrel fit in a socket prepared for 9mm?

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I've got a device that has a DC socket, but I think it might be for 9mm long barrels and I've already ordered 14mm jacks. Will it fit? If yes, then do I need to somehow secure the part of barrel which will stick out?
EDIT: Barrel size 2.5/5.5 mm


texts: Could a larger capacitor, at the output of the SMPS, destroy components with larger current draw when its being charged?

texts:
I am designing a SEPIC converter using a LT8364 for "power aplications" and a buck converter using a TPS62125 for powering a MCU.

Since I have a bunch (>100pcs) of 100uF, 16V, electrolitic caps laying around, I would like to use them to store a of bit current at the exit of thesse two switching converters.

I understand that using a big capacitor is better if you have an instant and huge current need, but I do not know what happends when you start everything up.

Question 1: Would a 100uF electrolitic capacitor draw an extremly high current at startup, as all capacitors do when they are being charged up and therefore would it destroy the IC or the inductor or would it be just fine because it's only high current for a fraction of a second?

Question 2: Would it be more effective to use a smaller value ceramic capacitor?

P.S. For the SEPIC, output would never go over 14V.


texts: Placing multiple inductors (buck) close to each other on PCB

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I have three buck converters on my PCB.

12V to 0.82V @ 25A -FP1308-R21-R, Fsw = 650 kHz, TPS548D21
12V to 1V @ 8A - IHLP2525CZERR47M01, Fsw = 1 MHz, TPS548A20
12V to 5V @ 3A - Inductor is XAL5030-332ME, 400 kHz (can be increased), TPS568215

Due to thermal issues and heatsink optimization, we need place all three of these inductors very close (3-5 mm) to each other.

All the inductors are shielded.

What will the inductor shielding effectiveness be?   There is no specification on distance vs field.

Can we place all three inductors close to each other? If we can place them close together, what considerations do I need to take care of?

Added a PIC of this.


texts:
For a class B amplifier which has a LC filter at the output, gives Pure sinusoidal Voltage and current waveforms. But if we check back the waveform at Drain, waveform for drain current remains clipped but voltage is pure sinusoidal.

Can anyone explain why voltage waveform gets copied from output to drain but not current?


texts: Panelization (& Depaneling) a Metal Core PCB

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What is preferred way to panelise a Metal Core PCB (MCPCB) - V-scoring or Tab-routing?

The engineering challenge I am facing is that the boards are meant for production (1,000 qty in the initial stage) and unfortunately the most economical SMT Assembly house that I am in touch with cannot depanelise the boards for us.

So the option is either to move onto a more equipped assembler (they are twice as expensive(!)) or depanelise the PCBs on my own.

Some notes on the board design:

It only has LEDs. No resistors or capacitors.
The LEDs are 2.3 mm away from the board edge.
Overall PCB thickness is 1.6 mm.
Boards are rectangular, mostly.
PCB is 25.5 mm x 21.25 mm.
Panel is 5 x 8.

Considering the above, is it a better option to V-Score or Tab-route? What method will allow me to minimize board stresses?

And furthermore, what is the recommend way to depanelise a MCPCB (goal being cost-effectiveness & minimized stress on the components?)

Note: I understand that at a higher volume, I will need a better and more automated way to handle this. However, for now, I am mostly concerned about the 1,000 quantity. I am also open to the idea of redesigning the board.

An idea that I had after typing this question: I should design the panel to be tab-routed. After assembly, I could use a manual milling machine to break apart the PCBs. Will a milling machine cause stress on the components/PCB?

I have access to several milling machines and cheap labour. This is not a big issue.


texts: Which pins belong in a "I/O region" on a MAX II CPLD?

texts:
I want to use an Altera/Intel MAX II device (EPM570) to drive 20 LEDs. They all have 20mA forward voltage, for a worst-case current draw of 400mA.
The application note AN 286 explains how an Altera/Intel CPLD can be used to drive LEDs.
Regarding the maximum sink current, the application note says this in page 3:

the EPM240 device has six GNDIO pads, which provide six I/O regions that can sink up to 130 mΑ. If you need to sink 15 mA for the outputs, you can have eight outputs per region. With the six regions of I/O between GNDIO pads, there are 48 possible outputs, each sinking 15 mA.

130mA is lower than 400mA, so I should distribute the LED pins across at least four I/O regions to avoid trouble.
But what is a I/O region? I can't find docs for it. The MAX II devices do have I/O banks but it's a different feature, enabling connection to logic devices at different voltages. And the numbers don't match: the EPM240/570 has two I/O banks according to the datasheet, and six I/O regions according to the application note.
What is the relationship between I/O pins and I/O regions (or VCCIO/GNDIO pins)? I see in the pinout that GNDIO pins are placed among I/O pins, and each I/O bank has three GNDIO pins. But how to know which pin belongs to which region?


texts: Why is the MCP23S17 device getting too much hot suddenly and randomly Raspb 4A?

texts:
Circuit is a Raspberry Pi 4A SPI master node talking with one MCP23S17 device: datasheet. I'm testing the singlest circuit version in a protoboard.
We are using A bank GPIOs for reading, and B bank GPIOs for writting. From them, two GPIOs will be used with wires, one belongs to the input bank and the other one belongs to the output pins group. So Out_1 and In_1 both will have one wire connected at each pin, as can be seen at the picture.
At the end of the wire it could be contact between out_1 wire and in_1 wire or not. So in_1 wire could be reading from out_1 pin or being not connected to anything ('Z' state/open circuit).
Input pin is configured with internal R pull up in order to read VDD when not connected.
Normally out_1 will ever be writing '0', so everytime in_1 is connected to out_1 --> in_1 will ever read a '0' value.
The circuit can be seen at the following pictures, when reads '1':

When reads GND:

This circuit is working at 1Mhz, as you can see MCP is fed with Raspberry supply pins. They don't need extra capacitors because Raspberry provides 100nF at their 3.3V and 5V pins.
At pictures it can be seen that Reset and Address signals has no R pull up, because they will be by the moment to VDD or GND constantly, with any value change. Resistors will be added to the final design where Rst will come from another digital source, instead of VDD.
Application works making thousands of writing/reading in a loop.
It can be working fine during most of the time, during hours.
The problem:
But suddenly the device is reaching too much temperature, I think it's closer to get burn. Here, reading fails. Even the two contiguous GPIO pins starts changing its input values when they are not connected to anything.
When it ocurres I can see how the multimeter reads 2.8v instead 3.3V from VDD Raspberry pins. So, it seems to be an extra current consumption but I don't know from which pin and why.
This situation stops if the device is reset. After making a reset, the temperature falls to normal and it works fine.
What can be happened? Why is the device getting this consumption? Would does it need to put resistors at address or reset pins?

simulate this circuit – Schematic created using CircuitLab
Added after posting and some new tests:
I have realized when overcurrent starts. By the moment during a week under test I can say when it happens: when I handle wires and push one of them into the GPIO input pin hole. My python control sw gives me feedback about when an input toggle its input value. I can see by screen how when overheating has started, a long toggle-switching is produced before get the stable. As long as toggle time is, then so closer to start the undesired behavior.
I have done a hw debouncig to an input with a 1uF capacitor and toggle has minimized until almost being completely avoided.
Thanks in advance.


texts: does a higher amperage source help prevent voltage sag?

texts: I'm currently troubleshooting my car's ongoing electrical issues and during the troubleshooting process so far I have gone through multiple OEM alternators and multiple OEM & non-OEM batteries. One of my theories is that out of the box these OEM alternators have faulty components or are simply under powered and can't handle the load of powering both the car's electronics and charging/topping off the battery (even when the alternator AND battery are new and installed at the same time). I'm experiencing system voltage sag - anywhere from 0.5 to 2.4 volts below normal at times. The OEM alternators are rated at 155 amps max. If I get a non-OEM direct fit high output alternator, 240 or 320 amps max, will it help prevent voltage sag?


texts: Using transistors to replace push buttons

texts:
I'm looking for a little help designing a transistor circuit. I have a small LCD (I took from an after-market car backup cam system), and I’m trying to control its built-in menu using the buttons of an old handheld game system. The LCD has 3 buttons to navigate its menus which are on a separate PCB with a single 3.3V signal line. The way it works is each button shorts the line to ground through a different resistor.

My idea was to just rebuild that circuit and replace the buttons with NPN transistors, then connect the base of each transistor to the output of a logic gate, which would detect when two of the game system’s buttons were pressed simultaneously.

The problem I seem to be having is the transistors aren't being triggered, and I don't really know enough about them to know if I've designed this wrong (the logic gate seems to be outputting correctly, so I must have done something wrong with the transistors).

The parts I’m using:
Transistors:
https://www.digikey.com/product-detail/en/on-semiconductor/2N3904BU/2N3904FS-ND/1413
Logic Gate:
https://www.digikey.com/product-detail/en/texas-instruments/SN74AHC02N/296-4514-5-ND/375964

Thank you very much for the help!

simulate this circuit – Schematic created using CircuitLab


texts: How to select the correct material for wire-wound resistors?

texts:
There are many resistors wires like nickel chrome wires, ferros chrome wire, nickel copper wires, etc.

All the wires gives us the desired resistance in resistors.

How can we select the best wires for resistors?

What are the parameters for selection of wires for wire wound resistors?


texts: I found it relatively easy to understand TDMA and FDMA but I just can't figure out CDMA and W-CDMA. For CDMA I think it is something like TDMA without time slots. At transmission side you can use whole bandwidth to send any signal from 0 to time "t". The one thing that secures you that signals wont interfere with each other is by "applying" to each signal different code (modulating that signal into that code). Receiver side only needs to know which code you used for which signal in order to "demodulate" it. I don't think I got it right, so any intuitive explanation would be helpful!


texts:
I have a SIM900 shield that I want to control with a Raspberry Pi. I want to use GPIO pins on the pi and UART pins on the SIM900 shield. If I understand correctly the numerous tutorials available, people usually power the pi and the shield with separate power supply (USB for the pi, 2.5 jack for SIM900).
Isn't it a way to power the shield from the pi with one of the power pins?

There is the documentation of the shield I use.


texts: What is the technical part name of conical indent LEDs?

texts:
I'm struggling to find manufactures, part numbers or datasheets for the wide angle LEDs that have the conical indentation on the top of the lens. I found one other question on here that referred to them as dimple tip LEDs.

I have a prject that requires to use of wide angle LEDs that radiates light in all directions, perpendicular to the semi conductor. The conical indent in the lens of an LED would be perfect. These LEDs are extremley popular in modern festival/holiday LED light sets. In fact, I have not seen an LED set that does not use these LEDs. The problem is, I'm not able to find them anywhere. A search of the internet does not produce any usable results for this type of LED.

There are other wide angle LEDs out there, including "straw hat" and "flat top", but these types disperse the light in an arc. Round, or dome shaped LEDs project light almost perpendicular to the semi conductor.

If there was some type of part name, number or manufacturer of the conical LEDs, it mightn't be so hard to source them.

Apologies if this is off topic, but I'm out of options at this point.

Examples:


texts: I²C, SPI, CAN protocols and the OSI model

texts:
Is there a reference or what is the explanation for I²C and SPI being just physical layer protocols in the OSI model (I know that this model is for communication and maybe not exactly for on-board buses) or is the data link layer protocol defined inside them?

How about the CAN protocol?


texts:
I'm a begginer in electronics so I have some very basic questions.
I would like to protect an OpAmp power supply rails from overcurrent. But I don't know at what value I should set this protection.
The OpAmp is the OPA445. I found this in the datasheet :

Should I make the protection for 4.2 mA because I'm working in a room where the temperature is regulated at 20°C?
edit: The reason why i need to know the current of the load is that I want to make a protection for the Opamp. I have four of them supplied by two dc/dc controllers in parallel. One for the positive rail and one for the negative rail. (LTC3863 and LTC3864). In order to size the components I need to determine how much current is drawn by the four opamps.


texts:
From the technical details of a multimeter:

  AC Voltage: - Range and Accuracy: 200mV ± (1.0%+2); 2V ± (0.7%+3); 20 ± (1.0%+3); 200/600V ± (1.2%+3)

What does the notation "± (0.7%+3)" mean?  Specifically, what does "+3" mean?


texts:
I have made this simple timing diagram that presents the triggering way of D flip flop. The flip flop is triggered by clock's rising edges. I am convinced that the diagram is correct signal-wise.

What I am worried about is the looks of it.

Do you think that it's correct timing diagram esthetics/appearence/looks-rules wise? Did I miss something?

Particularly: maybe the background net should appear only when clock/D/Q signal switches? Or not really and my diagram is fine anyway?


texts: Converting 3.3v logic level to 5v using octal bus transceiver

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I'm using the Raspberry PI to communicate with various sensors and other circuits that input and output 5V logic level. The Raspberry Pi itself has 3.3V GPIOs, so i need to convert the logic levels.

I found the following chip, with this capability:
http://www.farnell.com/datasheets/1635559.pdf

I'm quite new to hardware development and would like to know if I have to purchase any other components to use this chip. The datasheet mentions pull-up resistors for instance.

I also found this ready to go chip that I think uses the same component.  I can see various other components on it, but I would like to use the breadboard version :

http://ee.farnell.com/adafruit-industries/395/logic-level-converter-8ch-arm-development/dp/2301650?dimVals=110514096

Can anyone provide me with a circuit to hook up the SN74LVC245AN safely and effectively on a breadboard.


texts: ATmega8 LED blinking project not working properly

texts:
I am making a simple project using ATmega8 microchip. I uploaded this code to the AVR:

#include avr/io.h
#include util/delay.h

int main(void) {
    DDRD = 0b10000000;
    DDRD = 0b01000000;

    while(1) {
        PORTD = 0b10000000;
        _delay_ms(100);
        PORTD = 0b00000000;
        PORTD = 0b01000000;
        _delay_ms(100);
        PORTD = 0b00000000;
    }
    return 1;
}

It basically turns on and off two different LED's which are connected to pin (AIN0) PD6 and (AIN1) PD7.

When the system is working, the AVR can deliver power to just one of the LED's properly. Other LED has a significantly low brightness. When I measure the voltage delivered to the bright LED which is connected to PD6, it takes approximately 2.3 volts, and the dimmer one which is connected to PD7 takes approximately 1.2 volts.

Why I am having this issue? Is it about the code that I wrote or is it about the chip itself? On the other hand when I light just one of the LED's on either PD6 or PD7 with a simple code it works just fine. So there is no problem with pins, connections or LED's I use. (I also could not copy and paste the package names here correctly! So it is correct too.)


texts:
ETS can be used to sample repetitive signals with a high virtual resolution.
Lets say we have repititive 1MHz signal we want to sample. This signal can be sampled with ETS.
For example a comparator inside a delta modulator structure can be latched with a frequency that is minimal smaller than 1MHz to reconstruct the signal on a slower timescale and improve the temporal resolution. The problem is that a delta modulator has a limited amplitude resolution.
Can ETS also be used with a "normal" 16 Bit ADC? If yes how is the latching done?


texts: What symbol to use for a electronic circuit breaker in a schematic?

texts: What symbol should I use to electronic circuit breaker in a schematic?


texts: Why should I use digital filters rather than simply manipulate signals in the frequency domain and then recover them into the time domain?

texts:
I'm quite a novice in signal processing and I know this question may be too broad. But I would still like to hear hints from experts.

I was taught to use butter (to design Butterworth filter aka the maximally flat magnitude filter) and filtfilt (Zero-phase digital filtering) functions for bandpass filtering of EEG (electroencephalogram) signals in MATLAB offline (i.e. after the completion of recording). This way you can avoid inevitable "delay"   caused by the digital filter (i.e. zero phase filtering).

Then, someone asked me why we cannot use fft (Fast Fourier transform) to get the frequency-domain representation of the signal, and then set the power of unwanted frequencies to zero, followed by ifft (Inverse fast Fourier transform) to recover the filtered data in the time domain for the same purpose. This manipulation in frequency domain sounded simpler and reasonable to me, and I couldn't really answer why.

What are the advantages and disadvantages of using the simple fft/ifft method for bandpass filtering? Why do people prefer to use FIR or IIR digital filters?

For example, is the fft/ifft method more prone to spectral leakage or ripples compared to the established digital filters? Does the method also suffer from phase delay? Is there a way to visualize the impulse response for this filtering method for comparison?


texts: how can we solve a circuit with two opposing voltage sources using thevenin theorem

texts:
i have been asked to solve a circuit using thevenin theorem but when i try to solve it to find Vth by loop analysis, i realized that both voltages are in opposing directions and i can't understand that how can i write the loop equation for it.

  [1]: https://i.stack.imgur.com/OK0QK.jpg
This is where I'm stuck. I want to find Vth.


texts: segger j-link not connect to STM32F030F4P6

texts:
I use segger j-link v8, I believe programmer is true,because I could programmer stm32vldiscovery board with stm32f100rb cpu (by this help)
but when I try to connct STM32F030F4P6(TSSOP20) ,it fails..   I guess there is problem on VTref pin(pin 1 on jlink), where this pin must connect to? Which pin of stm32?

update:

  You see in the log that the J-Link sees 2,5V as your board power supply. Is that correct?

yes, it is. but I am confused, may I ask you what is that pin that VTref must connect(in the image)??


texts:
I've done a good bit of experimentation and learned quite a bit from other members of the site here. I've built several circuits that drive an N-channel MOSFET on the "low side". But to build an H-bridge inverter I need to drive MOSFETs on both the "high side" and the "low side".

Although I have the components to assemble the necessary driver circuit, I am tending to agree with other contributors here that I should just buy a "driver" chip. From what I understand most of these are just a charge pump internally with some required external components.

I think I understand the usage of such circuits, but have a few questions. Most of my knowledge comes from reading the datasheet of the IR2125 at this point.

I found it here: http://www.irf.com/product-info/datasheets/data/ir2125.pdf

All driver chips list a value like V-offset. Is this the maximum voltage they can produce above ground in the circuit? For example, if I have a 170 VDC current source, the gate of the high side for most MOSFETS needs to be around 180 VDC with respect to ground. This would give me a Gate-Source voltage of approximately 10 volts.
Most drivers have a IN or SIGNAL pin. This is what controls whether the driver is charging the gate or discharging the gate. I'm assuming my signal will always be 5 volts coming from a microcontroller. If I connect the V-B (High Side Floating Output Voltage) of the driver to the source of the high side MOSFET, do I need an optocoupler to drive the driver circuit?
Drivers list a T-on and a T-off. When I consider the maximum switching frequency of a circuit, do I just need to sum those values with switching speed of the MOSFET I am using?
I do not understand how the "current limiting feature" of the IR2125 is meant to work. It shows an additional connection to the MOSFET I do not fully understand. Is this driver meant to work with MOSFETs like the IRCZ44? Can I just ignore the current sense pins on the driver, or is there a cheaper driver I can select?
The companion to the IR2125 is the IR2121 for the "low side". Are these chips just meant to be a cheap way to get gate drive voltages from a +5 VDC power supply?


texts: BJT based mutivibrator pspice simulation in CADENCE ORCAD

texts:
I am trying to simulate a basic BJT based multivibrator circuit in cadence orcad pspice. However, I am not getting the desired output.

If I simulate the same circuit in NI multisim, I am getting the desired output.

Do we need any specific simulation settings in ORCAD in order to view the output?

update:

I have tried the recommendation. However, unfortunately, there is no oscillation at the output. Please find below the schematic and output results.


texts: Prevent full startup when only battery backup applied

texts:
I have an ATMega328 running firmware that goes to sleep when main 5V power is removed and runs on a 3V backup battery instead. While in sleep, the watchdog timer wakes it up occasionally to keep a running time count.  The 5V main power and 3V battery are OR'ed together with a couple of shottky diodes. This works great for the most part, I can kill the 5V and it keeps ticking along, mostly sleeping, on the backup battery.

Problem, however, is when the backup battery is applied first. It freezes the whole thing up. Even after I apply 5V, the whole chip is unresponsive. I've tried telling it to go to sleep immediately, if there is no 5V applied, but that seems not to work either.

Is there any official way of doing something like this?


texts: LM394 is obsolete. What is the new standard log amp circuit?

texts:
The traditional logarithmic amplifier circuit is described in National Appnote 311:

This circuit uses the difference of two transistor currents to generate the log of the input over a pretty wide range.

The well-matched transistor pair Q1a and Q1b are halves of the LM394 "supermatch" transistor pair.  But National discontinued this part last year with no clear replacement.

I can use LM3406 array, but the specs are far worse.  There are plenty of arrays of '2222 or
'3904 available, but there is no mention of matching in the datasheet.  The transistors might be on separate dies for all I know.

TI still sells some Burr Brown log amps but they are expensive.  LOG101 is $18.37 in onesies.  Analog makes the AD606 for $43.88 each or the AD830x parts for $12 - $20.

How can I (cheaply) make a logarithm?


texts: Gounding for EMI and signal integrity - LED Matrix multiboard design

texts:
I would like to implement a LED Matrix circuit like this one, where the LED matrix enclosed within the blue dots will be on a seperate PCB than the rest of the circuit.

Since this will be a multiboard design, I am confused whether ground lines should be passed between the matrix board and the main board to protect against EMI and signal integrity as suggested very well by the answers here and here.

If the boards don't share ground at all, then the return paths will flow directly between the shift registers and the mcu in the ground plane of the main board (not the matrix board). Which of course, will not stop the system from operating but will create huge current loops.

Questions:

1) Is a very high speed multiplexing of the leds in the array considered "high frequency" in terms of its currents so that the return currents choose the path of least impedance underneath the rows and columns?

2) Should a ground trace per signal (in this case per row, or per column) be added in the connectors bewteen matrix board and main board?

Thanks

EDIT: The design will be adjusted so that instead of a shift register, two multiplexer's will be used to switch between rows and columns and select a certain LED. Probably the ADG704 because of low Ton=20ns. This hopefully clarifies what range of frequencies I expect the system to operate at.


texts: Does bluetooth implement the 802.11 wireless standard?

texts:
I've read that the Bluetooth standard is IEEE 802.15, but it is implemented with IEEE 802.11. Is this true? Do they interfere with each other?
What standard is Bluetooth considered to use?


texts:
I am trying to replace the power cable on a Yamaha RX-385 receiver; it connects to the board via this connector, which I am failing to find on Mouser/Digikey. It seems almost like a 3-pin connector with one pin removed...
(A larger version of an image will be displayed, if you "click" that image below.)

Text on the female side: "HJST d E".

Text on the male (board) side: "H JST", a raised "1" and a separate "3".


texts:
I'm trying to solder two noise filtering / decoupling capacitors to my small motors. One from each of the tags / motor terminals to the motors outside case. However it is just not working at all, the solder just is not soldering to the case. I don't want to heat the case up too long in case the heat damages the coils inside.

Is there any specific technique to solder to something like this large metal case?


texts: What is current forward (if) of an IR LED

texts:
I see a lot current forward on datasheet, but I don´t know the difference from the "normal" current.

EDIT

On this datasheet, I saw a If (current forward) of 100mA and then on page 3 it states about current of 20mA. So, my question was about the difference of this two current.


texts: Do we have a SSR relay technology that can stand 100 switching per second for a long time?

texts:
Are SSR relays capable of switching on/off 100 times per second for a long time? For example 1 hour?

Does this affect the longevity!?

I want to use relays for 5vdc control and 12vdc output with very low current. But I don't know if it is safe to use it or not.

I have a electromagnetic relay that is capable of doing this, but the datasheet says it shouldn't be used more than 300 times per minute. That's why I want to switch to a better solution.

Update: second in title and body is correct!


texts:
I recently started a project that utilizes a piezo sensor to sense vibrations. The piezo signal is fed to a uC in order to detect vibrations above a certain threshold. However, the piezo's high voltage spikes may damage the pin so I added a schottky diode for reverse voltage protection and a zener diode for spike suppression.

The initial circuit looked like this:

simulate this circuit – Schematic created using CircuitLab

(The buffer is not necesarry, but it protects the uC)

Now here's the problem: When the uC is turned off, the piezo may still exhibit voltage when hit. Since Vcc is at 0V, the buffer or uC's internal protection diodes will be killed and damage the IC. Therefore, I need a circuit that isolates the piezo from the uC when there's no supply voltage.

Is there a simple solution to deal with voltages when Vcc=0V? It cannot draw more than 50uA when turned on because everything is powered by a coin cell.


texts: Wireless Power Coil - Is this shielding? Field shaping?

texts:
I'm taking apart a Qi wireless power transfer receiver. The coil is etched into the pcb. The entire coil area (approximately 3.75 x 4.5 cm) is covered by a rectangular piece of hard, brittle material.

The material:

has a flat, matte grey finish.
is about 10 mil (0.254 mm) thick
is very brittle, and snaps easily
Appears similar to graphite "pencil lead" although it doesn't mark paper
Is somewhat electrically conductive: a 1cm x 1cm square is about 70 kOhm corner-to-corner.

I didn't think to measure the coil inductance before I removed the material, so I don't have a before/after comparison.

It was affixed to the PCB using a contact adhesive, and was on the "non-receiving" side of the PCB. In other words, when this PCB was positioned next to its matching power supply coil, the material was on the far side (not sandwiched in between).

What is this material? What might be its purpose?

(I was going to attach a picture, but it only shows a uniform grey piece of broken material...)


texts: Checking amps with manual-ranging meter: Jack/dial consistency required?

texts:
Multimeter:  UNI-T 89XD manual ranging

I received a comment or two that said I will not get an accurate amp reading if I use the 20 amp jack and set the dial to anything other than the 20 amp setting, such as 60 or 600mA.

I have used the 20 amp jack and set the dial to 60mA and did not get an OL on the screen.  I got mA readings.  What is dumber, me or the meter? (Don't answer that!!!)

How true is the admonition that I will not get accurate readings if the 20 amp jack is used with other amp dial settings?


texts: Connector type on Atwood Truck Camper Jack Control Board

texts:
I wanted to hard wire controls to level my truck camper because the jack system only comes with a wireless remote from the factory.  But the jack system also controls the porch lights.  So I have to find the remote in the dark to turn the lights on outside.

The board has what I think is a molex connector on it.  When I momentarily ground a pin it turns on a light or operates a jack.  I want to wire switches up to the pins, but I would really like to buy the correct connector plug instead of just sticking individual jumper wires into the sockets.

I have searched for molex connectors and some look close, but I can't find the pin layout that the connector has.  Any help locating this connector would be greatly appreciated.


texts: Is it possible to use just a capacitor to debounce a button?

texts:
I have been wondering: why cannot you just hook up a capacitor to a button to debounce it? I have been figuring out how to reduce the work my microprocessor has to do, but I have very limited space on a PCB I am designing, so I don't want to do a full-blown debounce circuit which would complicate the design.

simulate this circuit – Schematic created using CircuitLab

That's a example circuit; sorry for any errors (I am not good at designing circuits with capacitors). Would this even work? For the tack switch, I couldn't find one that matches what it is in real life, but it works for this situation. The button is like the one found here. D10 stands for Digital Pin 10, but it doesn't matter; it just means the Arduino input. I also don't know how big of capacitor I would need, so if this circuit works, what size do I need?

Again, I am just trying to simplify this to make it easier to build while not having to do software debouncing. From looking at how capacitors work, this seems like it would work, but also it might make the button press longer/delay it if the capacitance is too big. They are commonly used for "smoothing" out noise in power supplies, so isn't this a similar thing where it "smooths" out the bouncing? Any circuit modifications to make it work (if needed) would also be appreciated.


texts: Are "rusty" capacitors enough to cause a computer monitor to malfunction?

texts:
I have a computer monitor with an interesting issue: when I plug it into my laptop, it comes out of low-power mode and my work appears onscreen, but about a second later the screen goes black as it re-enters low power mode. Moveover, this only happens intermittently. The monitor will have periods where it works just fine, and stays on after turning on, and it will have periods where it encounters this malfunction every time it is plugged in.

I have another monitor of the same model that works just fine, and it doesn't seem to be the laptop, the wire or even the connection to the computer, as the other monitor shows the company logo for a few seconds upon being turned on, while the malfunctioning monitor doesn't make it that far.

Seeing as the warranty was exhausted, I opened it up to see if there were any clear indications of something looking out of place, and the only thing I noticed is that there are two 150µF electrolytic caps that appear rusty on top. Not quite exploded, but rusty-looking:

It's possible that this "rust" is a leak, I'm not experienced enough to know.

Are these caps the likely cause of the issue?


texts: Why do linear voltage regulators have minimum output voltage > 0 V

texts:
I am trying to pick linear voltage regulator for my project (lab. power supply).

I am stunned, that only very few regulators claim to have output adjustable to 0 V. It seems to be due to the fact, that they generally use some sort of voltage reference connected in series with the ADJ pin. Simplified schematics, found in numerous data-sheets is in diagram bellow.

simulate this circuit – Schematic created using CircuitLab

Now to the question...
What is the reason for having this voltage reference? (1.25 V in diagram above)

Does it have anything to do with the stability of the control/feedback loop? HOW?
Is this a valid way to circumvent the minimum output voltage problem? Or will I encounter instability/any other issue?
If not #2, what is the kosher way of creating (high current) lab. power supply adjustable to zero volts? Do I need to put the load in between two regulators?

PS: This is my first question on this forum, please don't stone me right away :] I tried to search/google A LOT, but I am unsure what exactly am I looking for... many thanks for any helpful reply.

PPS: I am aware, that some regulators, such as LT3080 use current source instead of voltage reference, but this IC is supposedly adjustable to 0 V only for very small loads.


texts: How to design a PCB for sourcing 200A to MOSFETs

texts:
There are many examples of MOSFETs that, if cooled properly, can handle sustained currents upwards of 200A. Many of there come in surface mount packages.
How is it possible to design a PCB that is capable of handling the 200A drain current?
It seems like you would need to solder theses directly to a copper plate.
Example datasheet: IRLB3813PBF


texts: STM8S - Why does my Timer4 Overflow Interrupt not work?

texts:
This is my timer 4 init:

void initTimer(){
  CLK_PCKENR1 |= (1<<4); //Enable Clock for Timer 4
  TIM4_EGR |= 1;
  TIM4_PSCR = (0x03);    //Prescaler, Divide Clock by 7
  TIM4_IER = 1;          //Enable Update Interrupt
  TIM4_CR1 |= 1;         //Enable Timer
}

This is my service routine:

#pragma vector = TIM4_OVR_UIF_vector
__interrupt void TIM4_OVF(void){
  if(!didInit){
    initMAX7219();
    didInit = true;
  }
  applyBuffer();
  shuffleRight();
  TIM4_SR &=~(1<<0);    //Clear Update interrupt flag
}

But nothing works, the timer counter register gets incremented properly but the interrupt function is never reached, why?

Happy new year!


texts: ESD strike breaks the LAN8742A ethernet phy

texts:
My circuit uses LAN8742A ethernet phy. The system has a metal case and gets 220V AC to power supply board. After converting 5V DC it goes to my board that has Ethernet and mcu. I screwed case and power supply pcbs earth point to mains earth. The problem is this: When i strike 2kV with ESD machine to metal case power supply generates spike appx 48V on output :/ And it goes to my circuit. I have standart linear regulator circuit for 5V to 3.3V. Spike value decrases a bit little but neverthless it locks/breaks ethernet phy. Ethernet leds goes crazy or hangs at wrong position. After i power off AC and power on again everthing starts to work normally. I need an advice for solving this.
My circuit scheamatics are:


texts: Can Inductor force abrupt current change through another inductor?

texts:
Say the 3H branch of the circuit was connected to the 1V source for a long time such that 500mA current is flowing through the 3H inductor.

Then after long time the switch was connected to 1H inductor branch

Now, the currents can't change abruptly in an inductors. Therefore 500 mA can't flow through 1H branch just after switch transition, neither the current can drop to zero because 3H inductor will prevent it from happening.

My question is what will be the current in the circuit just after switch transitioning happen?


texts: What is the part number of this FET with top marking "NSC1"

texts:
LCD switch circuit part in laptop.

The marking is marked "NSC1".

"a" is the gate and 5 volts is applied
"b" is the drain
"c" is the source

3.3 volts is applied to b, and if a gate has 5 volts, 3.3 volts are crossed by c.

The fact that the gate voltage is higher than the drain is an N-channel FET.

Then "a" is the gate, "b" is the drain, and "c" is the source N-channel FET.

However, for most SOT-23 type FETs, "c" is the drain.

I need the product name of the FET where "c" is the source (as in the picture).

Maybe it is a P-channel FET. But if it is a p-channel fet, The gate voltage must be lower than the source voltage. Isn't it?


texts: KiCAD's eeschema: How to move a reference / value in a schematic?

texts:
I would like to arrange a component's reference or value label in a eeschema schematic but I cannot seem to select or move it.

If I try to edit the respective field's X and Y position via the "Symbol Properties" dialog, it does not have any effect and resets the values automatically.


texts: Tapping into a 5.1V transformer for a zero-crossing detection circuit

texts:
I want to make myself a reflow oven following more or less this guide: http://andybrown.me.uk/2015/07/12/awreflow2/

Here is the zero-crossing detection circuit diagram:

Thing is I would like to cut costs on BOM and workload. As I have a few spare 5V wall socket chargers lying around I went ahead and popped one of them open. It looks quite nicely built. I want to use this one for the power supply, but I now have this issue: where do I tap into it for connecting Q2 transistor base?

The main issue here is that the rectifier bridge (the magenta encircled IC) operates at 220V/ I.e. it comes in front of the transformer, not downstream as I need it. I figured that then perhaps I could take my signal from one of the secondary circuit pins of the transformer. I am not sure.

DMM readings (DC):

between any of the pins from the brown square and any of the pins from the
blue square: 230 - 235 V
between pins 6 and 7 in the yellow square: 0 V

DMM readings (AC):

between any of the pins from the brown square and any of the pins
from the blue square: <100V, rapidly stabilizing at 0V in a second or
so
between the pins 6 and 7 in the yellow square: 1-2 V, rapidly stabilizing at 0V in a second or so

Any tips?


texts: What Design is this Voltage Regulator (Is it a buck boost type)?

texts:
This voltage regular was designed by a new electronics graduate locally 20 years ago and it was not commercially produced (only privately sold) and discontinued. I need to know what kind of design it used and whether it's a buck and boost type.

This is the front and back of the voltage regulator (he used the acronym UPS for Universal Power Stabilizer.. he made it up. It's not an Uninterruptible Power Supply).

[
[
In the following image. The transformer 220V primary wires are connected directly to the output leads (or black outlet). Note the black wire is the neutral, the white at middle is connected to the 110V output outlet at back (I read that in buck and boost type, it is the secondary that is connected to both source and load, but in this case it is the primary that is connected to the load)

[
Here you can see the all secondary leads of the transformer connected to the circuit board.

[
The following is the circuit board. The 833H-1C-C is a general purpose relay. The circuit doesn't have any DSP controller. Here
http://www.stabilizer-regulator.com/voltage-stabilizer/static-voltage-regulator-dubai  it says a buck/boost type voltage regular has DSP.

Anyone has encountered or familiar what kind of voltage regulation this uses?

[


texts: Strange behavior of high gain amplifier using AD8000, high speed op amp

texts:
I'm designing a PCB circuit for an amplifier to amplify a pulse with a rising time of 1 ns about 100 times.
I decided to use the Analog Device AD8000 as op-amps.
This is the schematic of one amplifier.  The single board consists of six amplifiers placed row by row accepting six input signals.

In the above figure, I have cascaded one amp in non-inverting configuration (x10) and two in inverting
configuration (x10, x3). The impedance values for one input and two outputs are set to 50 ohms to match with LEMO coaxial cable.
The values of feedback resistors are referred from the manual.
When I soldered only one amplifier circuit and tested it (because I had failed and failed with my prototypes wasting a lot of expensive op-amps,) it worked well as I expected.
However, after soldering one more amp (consisting of three AD8000), all output signals oscillate.
I tried cutting out the ground plane below the input and output pads of the op-amps and adding a feedback capacitor to the non-inverting and the inverting configuration to reduce the stray capacitance but it didn't help to prevent oscillation.
I think it is not a problem of parasitic capacitance in that it works with a single amplifier circuit. It seems to that some kind of interaction between the sensitive nodes of op-amps through R1 or R13 (in the figure) connected to the ground plane makes it oscillate.
Can anyone explain why this oscillation happens and how to deal with it?
---------------------------------------------------------------------------------------------------Let me provide layers of 4-layers PCB. Please note that the it is actually connected in the red box.


texts: Interface PID temperature control module using Arduino

texts:
I need to interface a modular type temperature controller using Arduino.
This is the datasheet of temperature controller

The datasheet mentioned like this,

My questions are,
How can I interface( Reading/Writing parameters) to the controller using Arduino?
Is there any library for achieve this communication?


texts:
Can someone help me with getting the AC form of this MOSFET circuit? I am having trouble understanding why in class they took Q1 and Q2 out of the AC form:

The AC form they showed us in class (the FET you see here is Q3):


texts:
I am trying to understand how to choose a coaxial cable (for my current application, I need a 50Ohm coaxial cable that works reasonably well in the DC-10GHZ range).
According to the table in section "standards" of Wikipedia, I would choose the cable with the fewer possible "max attenuation", eventually taking into account the size and rigidity of the cable (I don't care about velocity factor). But I don't known if this attenuation measure at 750MHZ does mean something about 10GHZ.

More practical related question:

Does the LMR200 perform reasonably well at 10GHZ?

What about RG402? (I've read somewhere this is the preferred option for 10GHZ radio ham, but I don't understand why).


texts:
I'm looking for a replacement for a FET switch that switches at 40 kHz. When the FET is on it is connecting an RFID antenna to ground.  When off, the antenna is open.  It does this in order to backscatter 915 MHz RF back to a reader. The FET is not DC biased. Very little RF current is going through the FET. The part # is SD 403 (Calmos)

The problem is the factory is blowing up too many FETs with ESD.  So I'm looking at BJTs or a less sensitive FET to ESD.  Would a BJT require biasing whereas the FET doesn't?

Any suggestions?  Thanks very much.

Update

First, thank you all for the replies. Those of you who asked how I know it's ESD, I don't yet know for sure. We do our own SMT in house
I don't yet know how to post schematics. Is there a common way you all do it?
I like the switch idea but hope to do a drop in or not have to bias it. Our current design connects the antenna directly to the FET Drain which also connects to the ASIC Antenna pin. The low-frequency Mod pin connects directly to the FET Gate. Source is grounded. No caps, no bias resistors. Battery RFID tag. Will a BJT work like that?


texts: Why does the I2C interface use the open-collector/open-drain?

texts: The open-collector adds inconveniences like requiring an external pull-up resistor and slows down the throughput. Why did the I2C designers choose to use open-collector/open-drain?


texts: STM32 Logic level high and low thresholds

texts:
I am scratching my head to find what are the minimum voltage for registering a low digital signal and maximum voltage for registering a high digital signal when I configure GPIO pins of STM32 (I am using STM32L476) as Input Capture mode (I want to measure some frequencies).

No where in the datasheet and the Reference Manual I can see this details.

I have a signal that suppose to be around 0.3V when low and 1.8V when high...So I want to know these thresholds to either use a schmitt trigger in my circuit or use some divider resitors to up or down convert the levels to match inputs of STM32.


texts: What does this power supply label mean? What can I replace it with?

texts:
I bought some dangerously cheap AC LED floodlights. Cheap flex, shoddy sealing, no screw terminal block, no earth continuity, etc... But the LEDs actually kick out a good light so I'd like to persist.

I have already rewired —and earthed— two of these and have mounted them on the house using their glued-in transformers. Now I want to run a string of these down a long stretch of fence panel. At least three lights, spread over a 40m (130ft) run from the house.

I could do that with AC but that requires armoured cable in the UK which is expensive. I'd like to see if I could power these from an external AC→DC power supply at the house end and running a little low voltage line out to the units in parallel.

My problem is I don't understand the output rating on this driver:

24-46V seems like a huge variance. My understanding was that most LEDs fub out with 20-30% undervolting. This is almost 50% and that seems mad.

And it also has serious implications on the voltage drop I'm going to get from the distance I'm running. 46V could go a fair way with a small percentage drop-off. 24, not so much.

But assuming you can make sense of this,

What would you replace this with to power 3 of these over a long distance? 48V 5A?
Is there any benefit to something more exotic like stepping down to unreferenced 48VAC and adding a bridge rectifier in each unit?
What wire thickness would are you basing that on?
These are going to be on fence posts. Should I earth these still?
Any chance they'd be dimmable?


texts: Does a current source override the v=ir rule?

texts:
Consider:

Here I have two almost identical circuits. The only difference is that the first one has a current source with the voltage source. Shouldn't the current in the upper circuit be v/r, or 10 V/1000 Ω = 0.01 A? Why is it 5 A here?


texts:
Im working ADC in PIC24FJ64GA002 microcontroller using proteus simulation. I've a doubt regards AD port configuration register. I've connected a potentiometer in AN12 pin and channel was selected. The problem is even i comment the below analog/digital mode selection config bit code, its working. I can able to get ADC value.

AD1PCFGbits.PCFG12 = 0;

Is not necessary to mention the analog or digital mode for the corresponding pins?

Code:

 void InitADC(void)
{
// *******************************
// 1. Configure the A/D module
// *******************************
// a) Select port pins as analog inputs(AD1PCFG<15:0>)
AD1PCFGbits.PCFG0  = 1; //PCFG(12-0) 1:Digital mode, 0:Analog mode
AD1PCFGbits.PCFG1  = 1;
AD1PCFGbits.PCFG2  = 1;
AD1PCFGbits.PCFG3  = 1;
AD1PCFGbits.PCFG4  = 1;
AD1PCFGbits.PCFG5  = 1;
AD1PCFGbits.PCFG9  = 1;
AD1PCFGbits.PCFG10 = 1;
AD1PCFGbits.PCFG11 = 1;
AD1PCFGbits.PCFG12 = 1; <== **here i set 1**.
AD1PCFGbits.PCFG15 = 1;

Thanks.


texts: Will relays work to switch between two circuits which power same LED string?

texts:
I have two power supplies that share the same load, an LED string. The one power supply (Circuit A) comes from the AC Mains which is rectified and with the help of a switching mode driver IC, it supplies a constant current to an LED string.

Should there be a power failure in the AC mains, I would like the second power supply (Circuit B) to AUTOMATICALLY kick in to power that same string of LEDs. The second circuit is powered from a 12V lead acid battery which with the help of another switch mode IC it provides a constant current to the LED string. Should the power in AC return, then it must switch back to the AC mains circuit.

My question is: Will I be able to perform this automatic switching using a relay or relays? If so, could you please guide me as to how I can go about this? If this is not a good idea, may I please ask for a better suggestion. In the third diagram I drew my thought pattern on how I was thinking to switch between the two circuits.

I apologise in advance for anything that might be unclear or vague, I will gladly explain more if need be.

Your help would be greatly appreciated! Thank you!

PS. The circuits I drew are not the full circuits, I just drew them roughly so that you can get the idea behind them.


texts:
in the circuit below what is the maximum reverse voltage around the diodes?

I know the formula

but I dont know how to apply it ,

more over I dont know what does the question mean by vr1=vr2=150?

so the voltage around diodes will be 150 :| .


texts: How to setup and use oled SSD1306 I2C screen(UG-2864HSWEG01) in proteus 8.8

texts:
i am trying to simulate an 128 x 64 I2C oled screen with arduino but cannot get to work.
I am using the arduino compiler and the libraries adafruit gfx 1.1.5 and adafruit ssd1306 1.1.2 ( light size instead modern ones )
I have tried some codes and the companion examples in hex format but it does not work.
Also I have tried finding the oled the I2C address and no I2C devices found.
UPDATED and solved.
My references
OLED Datasheet
Youtube example
The current schema
My example code
#include <Wire.h>
#include<SPI.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define OLED_RESET 4

Adafruit_SSD1306 display(OLED_RESET);

void setup()
{

Serial.begin(9600);
display.begin(SSD1306_SWITCHCAPVCC, 0x3D);
display.display();
delay(2000);
display.clearDisplay();

display.drawPixel(40, 10, WHITE);
display.drawPixel(50, 10, WHITE);
display.drawPixel(60, 10, WHITE);
display.display();
delay(2000);

}

void loop()
{
delay(100);
}


texts: What does the "L" in inductance stand for?

texts:
"R" is resistor/resistance, and "C" is capacitor/capacitance, that makes sense. But where comes the "L" for inductor/inductance come from?

edit: Wikipedia says it's possibly in honor of Heinrich Lenz, but I'd like to hear something more affirmative.


texts: Power factor requirement for SMPS just above 75W

texts:
What is the power factor (PF) requirement for an SMPS or even just a standalone power factor correction (PFC) stage with a power level above 75W?
I know that in some cases the customer will specify the requirements at say 10% total rated load to be 0.9. For instance, assume that the PFC is rated for 1600W, thus 10% load will be 160W and the required PF is 0.9.
What about PF in between 75W - 160W? Does it have to comply with any requirements?
NOTE: Active power factor correction is considered in this example.


texts: Using complex number in solving linear circuits

texts:
I am reviewing about using complex number in solving electrical linear circuits.

I see that the input sinusoidal signal \$ V_m \cdot \cos(\omega t) \$ is replaced \$ V_m \cdot e^{jwt}\$.

Then solve for the complex output voltage with the complex input voltage above.

Finally, output voltage is the real part of "complex output voltage" that is determined above.

What I am confused is that why is it possible to do that?

The real input voltage is replaced by a complex input voltage and the output voltage is also the real part?

Why the imaginary part added to the input doesn't affect the real part of the output voltage?


texts: Amplifier circuit - NMOS mode of operation? Gain?

texts:
Ok I have the following circuit, with values of variables:

\$\displaystyle R_{1} = 1 M\Omega, R_{2}=10k\Omega,~~ k_{n}C_{ox}\frac{W}{L}=1mA/V^2\$ , and \$V_{T}=1V\$.

1) When \$v_{IN}=0\$, calculate minimal \$V_{R}\$ so that the transistor is turned on (\$v_{GS} \geq V_{T}\$)

2) If it's given that \$i_{D} >> i_{1}\$, evaluate the mode of operation of transistor \$M_1\$ and calculate the voltage gain \$\displaystyle a = \frac{\hbox{d}v_{OUT}}{\hbox{d}v_{IN}}\$

The first part is easy, \$\displaystyle v_{IN}=0 \implies v_{GS}=\frac{V_R}{2} \implies V_R \geq 2V_T=2V \implies \boxed{V_{Rmin}=2V}\$

The second part, however, is bothering me. We have that \$\displaystyle v_{DS} = v_{IN}\$ and \$\displaystyle v_{GS}=\frac{V_R+v_{IN}}{2}\$, because the two resistors are both \$R_1\$ so voltage is equally divided. Now, substituting them into the NMOS requirement for saturation: \$\displaystyle v_{DS} > v_{GS}-V_T \Longleftrightarrow \frac{v_{IN}}{2} > \frac{V_R}{2}- V_T > V_T - V_T = 0 \$ so in the end it follows that the transistor is in saturation if \$ v_{IN} > 0\$, and in ohm regime conversely.

My teacher, however, just said that the transistor is always in the triode (ohm) regime, and then proceeded to do the problem, using the current equation for ohm regime, etc.

Please tell me whether he was right and why. Thanks!


texts: Programming nRF24LE1 with an Amontec JTAG key

texts: I'm a bit lost on how to program my nRF24LE1 with the Amontec JTAG key that I have. It seems as if it's possible, but I cant find any information on how to. On their website, on the contrary, there is too much information, and I cant figure out what is relevant. If anyone knows, any help would be very much appreciated!


texts:
I am trying to layout my own pcb for a guitar amp similar to

but I am confused how the IN symbol that corresponds to the audio jack is supposed to be connected.

Switchcraft Inc. RN112BPC

I am neither sure which connection configuration shown is appropriate or which pin corresponds to which. If you know of a 1/4 inch jack with better datasheets that explain how to connect it, that would also help


texts: Switch (dis)connects an LDO regulator from VBATT. Where should the filter cap go?

texts:
In my system, there are several DC-DC regulators all attached to a VBATT unregulated rail.

One of the regulators is the LDO shown in the picture below. The user can connect it and disconnect it from VBATT to switch the LOAD1 (disconnecting the whole LDO prevents quiescent power draw when SW1 is off).

My question is, which of the following two locations should C1 be in, in order to prevent a "pop" (sharp voltage change) on the VBATT line when SW1 is switched from on -> off?

My hunch is to put C1 on the right side, where it is located in the picture, because otherwise if C1 were on the left side of SW1, then when SW1 goes off, C1 would abruptly dump its (nonzero) stored charge onto VBATT.


texts: I am building an H-bridge motor control for DC motor . I am using  "SQD40N06-14L_GE3 " N_channel MOSFET. Did i have to add a rectifier in parallel with the mosfet (the mosfet already have one integrated).Thanks


texts: How to calculate 18650 battery use time?

texts:
I am currently powering my mini fan using a normal power bank (the one used for smartphone) which is 5V, 2A output and can last for around 6-7 hours.

If I power my fan using two 18650 3.7V 2300mAh (7.4V output) batteries, how long could these two batteries power my fan? (The fan allows up to 9-10V input)

Thank you


texts: BJT schmitt trigger threshold voltage calculation

texts:
Here is the classic Schmitt trigger:

simulate this circuit – Schematic created using CircuitLab

And I would like to find the equation for the threshold voltage (\$V_L, V_H\$).

First I examined the case when \$Q_1\$ is starting to come out from the saturation region and \$Q_2\$ starts to turn on (input voltage ramps down from Vcc towards the lower threshold voltage VL).

This situation looks like this:

simulate this circuit

And this current \$I_{B1}\$ is equal to:

$$I_{B1} = \frac{V_{CC} - V_{CE1}}{(\beta+1)R_E + \beta R_{C1}}$$

And the threshold voltage is:

$$V_L = I_{B1} \cdot R_{B1} + (\beta+1)R_E I_{B1} + V_{BE1}  $$

$$V_L = \frac{(R_B1 + (\beta+1)R_E)\cdot (V_{CC}-V_{CE1})}{R_E+ \beta (R_E + R_{C1})} + V_{BE1}$$

And if we assume \$\beta \rightarrow \infty \$ and \$V_{BE1} = V_{CE1}\$ then the threshold voltage is:

$$V_L = \frac{R_{C1} V_{BE1} + R_E V_{CC}}{R_E+R_{C1}}$$

And now comes the hard part. \$Q_2\$ starts to come out from the saturation region because \$Q_1\$ is in the active region.

The voltage at the input rises towards upper threshold voltage VH.

And to find this point I use these two equations:

$$\frac{V_{CC} - V_B}{R_{C1}-\beta \cdot I_{B1}}=\frac{ \frac{V_{CC} - V_B}{R_{C2}}}{\beta}  $$

$$\frac{V_B-V_{BE1}}{R_E}=(\beta + 1)I_{B1} +\frac{V_{CC} - V_B}{R_{C2}} $$

And

$$V_H = I_{B1} R_{B1} + V_B$$

What do you think about this?


texts: Push Button with Voltage Rating (AC) : 125V, Only having power supply of 3.5 or 5V

texts:
I have 3 buttons (R13-81 PUSH SWITCH) for a school project. In the specifications, it is written that they take Voltage Rating (AC) : 125V (Source)

Problem is I only have 3.3V or 5V as power supplies. Will it still work ? I don't understand if it takes between 0 and 125V or if it has to take 125V every time. Also, the output needs to be 3.3V maximum... What should I do ?


texts: NeoPixel led WS2812B doesn't shine when given equal RGB levels

texts:
I was trying to light up WS2812B and it works fine when given RGB code something like this (255, 145, 67). But when I send code like (255, 67, 67) to this diode it doesn't turn on. Similarly if I want to get pure white color I cant send code (255,255,255) but instead I have to send (255,254,253) so they all would be different.

This doesn't seem to be a software problem for me but here is the program code. I'm using Atmel's ATmega328p mcu at 8MHz and code is compiled with avr-gcc compiler.
Would appreciate any suggestions how to fix this!

#include <avr/io.h>
#include <util/delay.h>

#define DATA_PORT PORTD
#define DATA_PIN PD0
#define DATA_DDR DDRD

void fill_array(int* arr, int color)
{
    for(int i = 0; i < 8; ++i)
    arr[i] = color & (1 << (7 - i));
}

void set_color(int* arr, int red, int green, int blue)
{
    fill_array(arr, green);
    fill_array(&arr[8], red);
    fill_array(&arr[16], blue);
}

int main(void)
{

    int rgb_array[24];
    set_color(rgb_array, 0,255,0);

    DATA_DDR = (1 << DATA_PIN);
    DATA_PORT &= ~(1 << DATA_PIN);
    _delay_us(100);

    for(int i = 0; i < 24; ++i)
        if(rgb_array[i]){    //send one
                           //1 clock cycle is 0.125us
            DATA_PORT = 1; __builtin_avr_delay_cycles(6); DATA_PORT = 0;
        }
        else{  //send zero
            DATA_PORT = 1; __builtin_avr_delay_cycles(3); DATA_PORT = 0;
        }

    DATA_PORT &= ~(1 << DATA_PIN); //reset signal
}


texts: Number of implicants in case of don't cares

texts:
How many implicants are present in the given k-map?

I know that there are 6 prime implicant and 0 essential prime implicants.

My attempt:-
by taking each 1 and X individually(as a product term) we get 6 implicants-

by pairing we get 6 more implicants-

so finally we have 12 implicants

Is it correct?


texts: Optimizing HF (13.56 MHz) RFID reader antenna for the smallest RFID tag

texts:
I want to use currently the smallest (3.2x3.2 mm2) HF RFID tag from Murata LXMS33HCNK-171 together with RFID reader based on MFRC522 RFID frontend from NXP. In my application, the maximal distance between the tag and the reader antenna is max. 6mm and they are always in parallel planes, where tag can always be "inside" the reader's coil. For designing this I follow application notes from NXP mostly for antenna tuning guidelines, but I also follow AN710 from Microchip, where the theory is very well described.

The equation 7 derives the mutual inductance between the reader's and tag's antennas as:

where a and b are reader's and tag's coil diameters respectively. r is the distance between the coils. Later they show that the optimal reader's coil diameter is \$a=\sqrt{2}r\$. From this, it can be assumed that the bigger the radius of the tag's coil the higher M.  So, for the fixed distance between the coils and the Ampere-turns, the only way to increase the mutual inductance would be to increase the size of the tag's coil.

What I am trying to understand is how the ratio of both coil's sizes influence for example near-field coupling and signal backscattering. For example, if the reader's antenna is much bigger than the antenna of the tag, is it true that the tag's antenna will not have so much influence on the reader's antenna? In other words, should reader's and tag's antennas be of nearly the same sizes?


texts: 3rd harmonic component of flux and current in Star -Star connected 3phase transformer

texts:
I wanted to understand what will be  3rd harmonic component of flux and current in following connection .
Connection -
Star- Star connection (with neutral on primary side only)
Further description-
Balanced 3 phase sinusoidal Supply(also in star) is connected to primary winding(in star) of transformer with neutral also included while secondary winding (connected in star ) of transformer is connected to 3phase balanced  linear load without neutral.
First I thought that since primary side has neutral connected to supply and hence 3rd harmonic component of current can flow through it and hence flux will be almost sinusoidal .Now on secondary side since flux is sinusoidal in primary so it should be sinusoidal also  in secondary but problem is -
Load is connected in star without neutral so there is no possibility of 3rd harmonic current in secondary side and hence flux should have 3rd harmonic component but it is opposite to what I have concluded earlier .
Where did I make mistake in my analysis?  what should be 3rd harmonic component of current and flux on both sides?
any help would be much appreciated!


texts:
I am trying to do stimulated Raman scattering microscopy. In this experiment two pulsed laser beams are used . The wavelength of these two laser beams is tuned to match a specific Raman frequency of the system under investigation. When this condition is fulfilled one of the laser beams loses a slight amount of energy and one of the laser beams gain a slight amount of energy. There is no other wavelength involved. The change in the intensity is the signal itself.  This is known as stimulated Raman gain or stimulated Raman loss. Now The laser light  itself is very strong and compared to that these fluctuations in the intensity are very very small and no detector can sense that. To overcome these problem , one of the laser beams is modulated at a particular frequency (using a Acousto optical or electro optical modulator). This means that the relative raman loss or Raman gain will also be modulated and you can use a lock in amplifier to detect those fluctuations.

Since, you are detecting the laser light directly , PMT and APD are automatically out of the contention. Usual standard protocol and state of the art right now is that people take a  large area Si photodiode  (peak wavelength somehwere in the range of near IR) and drive that to a large reverse bias (60-70V) and feed that output to a lock in amplifier. Currently the photodiode that people around the world use is thorlabs FDS 1010. The vendor rating is 25 V but research group using this use home made circuits apply 70V of reverse bias.  So far I have not been able to find a commercial solution and am looking for building one myself.

Lastly, sensitive enough means under those above mentioned conditions the change in intensity / laser intensity < 10^-6 should be detectable when lock in amplifier is used.

Our wavelength of interest  : 1031 nm , lock in amp is SR 865a, BNC or SMA connections.

I have a bare photodiode FDS1010, THORLABS. I need to convert this into a full fledged detection system equipped with variable reverse bias, BNC output for signal etc. What will be the best place to start with  (in terms of literature, lessons etc). For instance, one confusion I have is that whether a reverse bias of 50 V means that the point marked as the reverse bias in the circuit diagram has to be connected to a external Dc source at 50 Volts?


texts:
Roboteq motor controllers (e.g. SDC2160) have several open drain digital outputs. We use them to switch a single segment of 24V LED strip, drawing about 17mA. At first everything seemed to work just fine, then we noticed that when switched off the LEDs have a faint glow. They had ~13V on them.
After long back-and-forth with manufacturer we reached their engineering team. They tested with 120 Ohm resistor and said that everything works fine and our problem is that the load is too small, not enough for MOSFET to close. We did more tests:

Increased the length of LED strip to draw about 500 mA. Still faint glow in OFF state and same 13V across;
Tested with 100 Ohm resistor. The voltage on resistor dropped to 30mV, confirming their test;
Added 10k resistor in parallel to LED strip. The voltage now about 400mV and NO GLOW;

There are only few details in the datasheet: 1A maximum current, 1.5Ohm open resistance.
Now, I always thought that with FET gate shorted to ground it should be fully closed no matter what load is connected to it. My guess is that the firmware sets MCU control pin to + to open DOUT and sets it floating (instead of GND) to put DOUT into high impedance state. Floating gate might explain why FET does not close completely. If that is so, than firmware fix should be trivial.
Does this make any sense, or should we add that 10k resistor and live with absolutely unnecessary extra drain on the battery?


texts: STM32F4: SD-Card using FatFs and USB fails

texts:
I also asked this on SE: Stack Overflow

In my application, I've set up a STM32F4, SD-Card and USB-CDC (all with CubeMX).
Using a PC, I send commands to the STM32, which then does things on the SD-Card.

The commands are handled using a "communicationBuffer" (implemented by me) which waits for commands over USB, UART, ... and sets a flag, when a \n character was received. The main loop polls for this flag and if it is set, a parser handles the command. So far, so good.

When I send commands via UART, it works fine, and I can get a list of the files on the SD-Card or perform other access via FatFs without a problem.

The problem occurs, when I receive a command via USB-CDC. The parser works as expected, but FatFs claims FR_NO_FILESYSTEM (13) in f_opendir.
Also other FatFs commands fail with this error-code.

After one failed USB-command, commands via UART will also fail. It seems, as if the USB somehow crashes the initialized SD-Card-driver.

Any idea how I can resolve this behaviour?

My USB-Implementation:

I'm using CubeMX, and therefore use the prescribed way to initialize the USB-CDC interface:

main() calls MX_USB_DEVICE_Init(void).

In usbd_conf.c I've got:

void HAL_PCD_MspInit(PCD_HandleTypeDef* pcdHandle)
{
  GPIO_InitTypeDef GPIO_InitStruct;
  if(pcdHandle->Instance==USB_OTG_FS)
  {
  /* USER CODE BEGIN USB_OTG_FS_MspInit 0 */

  /* USER CODE END USB_OTG_FS_MspInit 0 */

    /**USB_OTG_FS GPIO Configuration
    PA11     ------> USB_OTG_FS_DM
    PA12     ------> USB_OTG_FS_DP
    */
    GPIO_InitStruct.Pin = OTG_FS_DM_Pin|OTG_FS_DP_Pin;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
    GPIO_InitStruct.Alternate = GPIO_AF10_OTG_FS;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

    /* Peripheral clock enable */
    __HAL_RCC_USB_OTG_FS_CLK_ENABLE();

    /* Peripheral interrupt init */
    HAL_NVIC_SetPriority(OTG_FS_IRQn, 7, 1);
    HAL_NVIC_EnableIRQ(OTG_FS_IRQn);
  /* USER CODE BEGIN USB_OTG_FS_MspInit 1 */

  /* USER CODE END USB_OTG_FS_MspInit 1 */
  }
}

and the receive-process is implemented in usbd_cdc_if.c as follows:

static int8_t CDC_Receive_FS (uint8_t* Buf, uint32_t *Len)
{
  /* USER CODE BEGIN 6 */

    mRootObject->mUsbBuffer->fillBuffer(Buf, *Len);

    USBD_CDC_ReceivePacket(&hUsbDeviceFS);

    return (USBD_OK);

  /* USER CODE END 6 */
}

fillBuffer is implemented as follows (I use the same implementation for UART and USB transfer - with separate instances for the respective interfaces. mBuf is an instance-variable of type std::vector<char>):

void commBuf::fillBuffer(uint8_t *buf, size_t len)
{
    // Check if last fill has timed out
    if(SystemTime::getMS() - lastActionTime > timeout) {
        mBuf.clear();
    }
    lastActionTime = SystemTime::getMS();

    // Fill new content
    mBuf.insert(mBuf.end(), buf, buf + len);

    uint32_t done = 0;
    while(!done) {
        for(auto i = mBuf.end() - len, ee = mBuf.end(); i != ee; ++i) {
            if(*i == '\n') {
                newCommand = true;
                myCommand = std::string((char*) &mBuf[0],i - mBuf.begin() + 1);

                mBuf.erase(mBuf.begin(), mBuf.begin() + (i - mBuf.begin() + 1));
                break;
            }

        }
        done = 1;
    }
}


texts: Alternative to opto-isolators on equally powered circuits

texts:
I'm a hobby electrical noob. I'm playing with my Arduino to trigger shutter on my DSLR. I have read many tutorials to do so. Many of them recommends using Opto-isolators to separate Arduino from DSLR circuit to avoid shorts & damaging either of the circuit.

On my hardware part,
I just have to connect shutter pin to ground pin on the camera to trigger shutter.
current flow from my camera shutter pin is about 3.6v. I'm drawing a current from my camera pin at 5v & regulating down to 3.3v to power my Arduino as it runs on 3.3v. Hence, here I have a single power source to run both circuits.

So, Is there any alternative to design electrically safe circuit without using opto-isolators in afore mentioned scenario ? How Intervalometers available in the market works ? Do they use opto-isolators too ?


texts: Where is this noise coming from? 200 kohm Wheatstone bridge

texts:
I have a Wheatstone bridge I want to use to measure a resistive sensor. At the moment, all four arms are fixed resistors, while I get the circuit set up. The noise in the circuit is much larger than I expected, and I can't work out why.

simulate this circuit – Schematic created using CircuitLab

The AFG is configured to source two sine waves in antiphase on the two outputs. The Stanford is making a DC-coupled differential measurement with an effective noise bandwidth of 0.5 seconds. The two instruments are phase locked using the TTL ref. I'm then looking at the variation of the measurements to work out the noise. I find a noise component which scales with excitation voltage, which I can't identify.

The unidentified noise is white from 10 Hz to 1 kHz
The amplitude of the noise is about 1 µV/√Hz per volt applied across the bridge
When the excitation voltage is zero, I measure a noise consistent with Johnson noise in the bridge.

I have lots of experience of measuring R less than 1 Ω, but 200 kΩ is new to me, so I might be missing the obvious.


texts:
Given a SMPS PWM inverter (for example an UPS) supplying voltage/current at 50/60Hz, how do you design an output inductor?

I don't mean how you compute its value in uH/mH nor its current rating in A.
I'm talking about how you could (and if) wind your own inductor like you do for DC/DC converters (buck, boost, ...) high frequency applications. In DC/DC converters applications you have a mostly DC component plus some 10kHz-500kHz current ripple. The high frequency allows for smaller magnetic cores and for these applications there is a huge amount of application notes.

I've been struggling for a very long time to find a reference book or paper to explain how to design a PWM inverter output inductor but couldn't find any.
I tried looking into:

Ferrite cores -> AFAIK not feasible
Powder cores -> Still trying to understand them. Sometimes in the application notes they say "line filter" but I'm not sure that means they support a very high current before going into saturation. Probably just used for common mode chokes or the likes.
Tape wound cores -> May work (NiFe cores) but still cannot find any application notes on how to design/wind your inductor at 50Hz
Laminated steel -> Works but its very bulky, pricey and heavy

Therefore which materials could be used for the output inductor of a PWM inverter (50Hz fundamental-wave current plus some high frequency ripple) and how to use them?
I know laminated steel works because I used it for a project but I was just wondering if there are alternatives to it.

I mean, in nowadays with solar inverters for instance, I don't think they are using laminated steel for the output inductor because the whole inverter seems to be quite small.

If you need some reference values: RMS output voltage is 230V at 50Hz and RMS output current can be in the order of 10A-20A.

Feel free to ask for clarifications if needed.


texts: Current at different points in a DC boost-converter

texts:
simulate this circuit – Schematic created using CircuitLab

I have a voltage source(V1) connected to a boost-converter, the components aren't rated(more focused into the theory than actual build). What is confusing me, is the current. The input current will be set to whatever the power-supply(V1) is inputting into the circuit, I know that input-current  \$I_o\$ < \$I_i\$, I'm not sure how to rate the currents like so:

At point(A) : \$\ I_i\$

At all other points, is current simply \$\ I_o\$ = \$\ \frac{V}{R}\$ at B,C,D?
What's troubling me is point A and the rest, how are they different values in series... like A and D


texts: Increasing output current from ZVS driver

texts:
I bought the ZVS driver as shown in the picture below:

After connecting a flyback transformer, I tried measuring the voltage and current at the output. The open circuit voltage is about 12KV. To measure the current I used around 560Ohm resistor at the output in series and used ammeter to measure. But the ammeter showed a very low current of about 40mA only. Any idea or suggestions to increase the current to 200mA. I tried to play around by increasing the number pf primary turns of flyback transformer but I couldn't increase beyond about 15-16 turns and I didn't see much increase in output current. I am using adapter of 12V 2A rating as input to driver.

How can I increase the output current from the flyback?


texts:
I am currently making a shopping list for an LED light strip (link) and I am getting 3m of it. Now, my main problem is powering that beast.

By my calculations, (42W * 3m) / 5V = 25.2A, if that is correct, that seems like an insane amount of power for such a strip, and any power supply I could find that was > 15A is just a barebones transformer.

They have listed that 42W/m is the maximum power draw, which I am not extremely likely to do, so I am currently looking at this power supply. Would it be sufficient?


texts: Finding a material transparent to 26GHz radio waves for radome protecting a radar rangefinder probe

texts:
I want to use a 26GHz radar probe to measure water levels for some outdoors applications. These are pretty common devices, one manufacturer among many others is for example:
https://en.supmea.com/cpdetail_28_297_307.html
My use is a bit specific as the sensor may be subject to very harsh conditions, so I want to harden it quite a bit. We will build a robust box around the whole head of the sensors including the divergent.
The only problem is to know which material to use to close the protection box "from below", i.e. where the radar signal propagates, i.e. which material to use at the exit of the divergent (our "radome"). This protection is necessary as there may be saltwater coming with quite high velocity / pressure from below the sensor, and while the sensor is IP67, this may not be enough to ensure durability in my use case.
So what I am looking for really is a material that is reasonably strong mechanically, that I can get my hands on, and that will be reasonably transparent to 26GHz radar waves. Any suggestions? Any kind of plastics or other that could fit the needs?
PS: If this is the wrong place to ask this question, sorry in advance and let me know, I can move the question.


texts: Charging and using 3 separate Li+ batteries in parallel (using 1 or 2 or 3 together)

texts:
The idea is to make a battery setup in such a way that the user can use 1 or 2 or 3 18650 Lithium cells. The circuit would draw power via USB to charge the setup as well as run the application circuit after the boost section. The load is around 500mAh.

An p-Channel mosfet is used to act as a switch for the final output. USB-5v is connected to the gate of the mosfet, the output of the UV protection circuit is connected in parallel to the drain of the mosfet. So as soon as USB is shut off, the circuit would draw power from the battery pack that is connected. Circuit reference from ESE answer.

The main reason to use the setup was to allow the user to use 1S by default. If the lifetime of the application circuit was to be extended, the user attached another 1S to the setup. So the boost section ( 3.7v-4.2v  to 5v) remains the same.

Questions

Is it safe to use 3 separate charging ICs and 3 separate 1S battery protection ICs to charge 3 separate Li+ batteries?
Is is safe to draw power by connecting the output of the protection circuits in parallel?

I came across TP4056 modules on Amazon. So looking at the reference design, I was wondering if the above setup would be possible and safe to execute?

Update:
Added diodes to the output of the main block.


texts: Replacing analog scope BNC input connectors

texts:
I am wondering if it's safe to replace the BNC input connectors on my old Hitachi v-422 scope.

As long as I'm careful and stay away from the CRT etc? Or is there anything else I'm not aware of?


texts: How to wire Mean Well RT-65D power supply?

texts:
I'm not very familiar with electronics. Especially I have never wired a 230 V power supply manually.
There is a Mean Well RT-65D power supply.

I have a rubber connector with open wires blue, brown and yellow-green.
And I have a consumer which needs 24 V.

My suggestion is (edited):

brown => Pin 1 (AC/L)
blue => Pin 2 (AC/N)
yellow-green => Pin 3 (FG)
consumer +24V => Pin 6 (DC OUTPUT +V2)
consumer GND => Pin 7 (DC OUTPUT COM)

Is that correct?


texts: Confusion about Thevenin's theorem for linear circuits with non-linear elements

texts:
My question is about **linear circuits** which has non-linear elements.

When I read about Thevenin's theorem, all explanations say that it is basically about representing a linear circuit as a voltage source and an output impedance. And right after they give many examples about how to thevenize a circuit and obtain a Thevenin voltage and Thevenin resistance(output impedance).

In all of their examples the circuits are composed of the combinations of resistors, capacitors, inductors, current and voltage sources. I haven't seen a single example where they use a non-linear element like a transistor or diode in those examples.

"Linear Power Supply are called linear because semiconductor devices are operated in the linear mode unlike switch mode power supply where semiconductor devices are operated in the switch mode i.e. either on or off."

So imagine a power supply SMPS or linear supply. Is the output impedance of a power supply thevenin resistance? If so does that mean that a power supply is a linear circuit/system? And even if it is linear as whole system/circuit, it includes many non-linear elements. Does thevenizing techniques apply to a h-parameter model of non-linear elements for example?

Imagine we have the circuit diagram of an SMPS or linear power supply. Can we thevenize this circuit such that we can employ Thevenin's tricks and find the Thevenin voltage and resistance(output impedance)?


texts: Get an anemometer to activate a solenoid bolt and as low-tech as possible

texts:
To all you bright  minds out there
I have a project where I would like to stop a large outdoor wooden turntable from moving in moderate to high wind. The idea is to buy an anemometer off eBay that has an output of 0 to 5 volts
Or 4 to 20 mA And has an input voltage requirement of 12 to 24 V.
I would like the output voltage/current to control a circuit with a relay switch that when the wind speed gets up to for example 3 V or 10ma the relay will Kick in and switch on a solenoid Bolt which would stop the turntable from turning. And then when the wind drops, the bolt releases and the turntable is free again. This is for a project I’m doing in the garden. A high wind could destroy, the sculpture if it overpowers the turntable mechanism.
Is it possible to have a variable resistor in the circuit? so I can adjust the sensitivity of the relay kicking in the solenoid bolt. I wanted all this to be very low voltage so it could work off a Solar cell and rechargeable battery.
I went to art school and then did design and I’m learning electronics. So I am a rookie.
Any advice would be most helpful to stop the turntable moving in moderate to high wind


texts: Where do overtones in a 555 generated square wave come from?

texts:
I have built a 555 oscillator and connected it to a speaker.

Using an oscilloscope I adjusted the 555 to generate a 2.5kHz square wave.

I then held a microphone up to the speaker and fed the input into a spectrum analyser.

What I expected to see was a single peak at 2.5kHz. However, what I actually got was this:

My question is, where have these harmonics come from if the 555 is only generating a 2.5kHz signal?

I know that a square can be constructed from sine waves:

However, the 555 does not generate sine waves or multiple frequencies, it generates a single square pulse. So where have these harmonic frequencies come from?


texts: Isolating Power in Communicating 5V Sub-systems

texts:
I have been plagued by a sensor sub-system which, when connected to my base micro-controller platform, intermittently causes issues that I would categorically associate with power sequencing issues at start-up. Some examples of things I have sometimes observed to apparently happen with this sensor subsystem attached:

processing board won't come out of reset / start its program
processing board experiences program (flash) corruption
processing board experiences data (eeprom) corruption
processing board fails to accurately read values stored in eeprom
processing board fails to initialize external SPI / I2C device

The sensor sub-system interface is a UART (RX and TX), and power is delivered to it through the processing board, which also has a FET-based high-side switching circuit gating the 5V to the unit, which gives the processor board the ability to shutdown / power-on the sensor sub-system. For your reference, here is a schematic excerpt of the high-side switching circuit.

That circuit has never really worked as I had intended. My firmware can, sure enough, shut the sensor sub-system down. But it can't power it back up without taking a reset itself. What a nightmare! But at least it can shut it down in the case of a communication failure mode, so I've lived with various firmware workarounds / behavioral patterns for a while. Settling for workarounds has been a curse though, and I really want to get to the bottom of it.

I've been over it in my head a lot, and I haven't been able to narrow down a root cause with certainty, so I think it's time to seriously reconsider my integration strategy in order to better decouple the power distribution between the processing board and the sensor sub-system somehow.

My system is powered by a 5V/2A AC/DC power supply that has plenty of headroom (at least 50%) for the whole system to operate. The processor sub-system is of my own design, the sensor sub-system is commercial off-the-shelf, I can't change it.

So here are some questions:

What kinds of design changes would you consider in my situation?
What coherent explanations are there for why my processor sub-system can't power down and then power up the sensor sub-system without taking a reset itself?
What steps can I take to make my design more robust / reliable without breaking the bank (after all, it's not a safety critical system or anything like that)?

Cross-referencing tangentially related quesiton / consideration here.


texts: When using multiple constant current drivers for High Power RGB LEDs, connect Vo- together?

texts:
I'm using a set of three Mean Well HLG-60A-C350AB in order to drive a string of 48 no-name high power RGB LEDs.
I chose these drivers because they provide an easy way to regulate the constant between 200mA and 350mA, in order to compensate for brightness deviations between the three colours. I chose to use three of them in order to individually control the RGB channels.
The drivers are fed from the same AC voltage source. The LED brightness is controlled by PWM from an Arduino Mega stepped up to 10V.
Should the Vo- of the drivers be connected together?


texts: Square wave from high voltage power supply (5kV)

texts: I working on a project involving dielectric elastomer actuators and need to generate a square wave from a 5kV power supply (SRS PS350). The operating frequency will be 0-50Hz. What's one circuit I could use to achieve this?


texts: mbed Alternative to FreeRTOS's vTaskDelayUntil()

texts:
FreeRTOS's vTaskDelayUntil() function causes a thread/task to unblock at an absolute time, therefore ensuring that threads are "awakened" in consistent time intervals.

Does the mbed platform offer something like this? As far as I know, the Thread::Wait function causes the thread to unblock relative to the time it was called.


texts: Exposed contacts for power and data in an underwater project

texts:
I have a dive flashlight that charges via a proprietary USB connector and exposed pads on the exterior. My dive computer also has similar pads that don't charge but allow for data download and programming. I have seen similar things on other marine electronics that are potted in epoxy and just have some wire loops sticking out to hook onto for a data interface.

My question is what kind of circuit do you need to prevent a short, battery drain, or other bad things I can't imagine from happening?


texts:
I have a 4 layer design, Top, layer2, layer3, bottom.
Now I want to place GND vias on a ground polygon. Layers Top and Bottom both are a complete ground plane (Polygon)

I was wondering; What is the most effective way to place this GND via and what are the differences?

I realise that on the first picture, the GND via is connected to the top layer polygon. And on the second picture it is both connected to the Bottom and Top layer polygon.

FYI, looking at the Eagle design the GND vias are not ''repoured'' as they are on Altium.

Again, I am nog experienced with Altium. Maybe there is a setting which lets me place these GND vias as they are on Eagle. (If that is a correct method)


texts: Help identifying this variation of a Molex or Amp connector please!

texts:
My very first post!  I've researched to the point of despair (digikey, mouser, amp, molex, others...) trying to identify this variation of your everyday 4-pin, 2-row molex pin plug.

An easily findable version has your expected square plastic molex "pins" that house the actual crimped pins, with what one might call the "upper left" and "lower right" being tombstone shaped rather than square to enforce polarization.

I'm working with an old discontinued piece of LED stage lighting equipment with a variation of that that is polarized differently, and I can't find the connector anywhere.

I might have found the connector here or there, but the information that explains HOW a version of your typical molex connector is polarized is pretty well ignored in specs and descriptions it seems, and as for photos so many of the online resources only show stock photos rather than a specific photo of the exact connector.

Attachments and images to clarify my need.  Any help would be greatly appreciated!


texts: How to have an edged triggered reset signal in a sequential verilog circuit?

texts:
I am wondering how it is possible to build a sequential verilog circuit with a reset trigger.  The problem I am having is that I need an always block specifically for when the reset is triggered.  I have created this example of a counter to demonstrate what I mean:

`timescale 1ns / 1ps

module Counter(input CLK, reset, output reg[2:0] val);
    always@(posedge CLK)
        val = val+1;

    always@(negedge reset)
        val = 0;

endmodule

The bug I get when synthesizing this is

"ERROR:Xst:528 - Multi-source in Unit <Counter> on signal <Mcount_val_cy<0>>; this signal is connected to multiple drivers.
Drivers are:
   Output signal of FD instance <val_0>
   Signal <val<0>> in Unit <Counter> is assigned to GND"

This is because val is updated in 2 always statements.

How can I work around this and have a sequential circuit with a reset trigger?