texts: How does soft start work in TI buck regulators?

texts:
I am planning to use "TPS54341" in my design.
I am curious about how the soft start circuit internally works in TI regulators.

The datasheet explains to how to use it, however, does not go in much details on what's the theory of operation.
http://www.ti.com/document-viewer/TPS54341/datasheet/detailed-description#slvsc612433

There is a block diagram in the section 7.2


texts:
I have been in two separate design reviews where the SEPIC topology was rejected for an isolated < 40W application. These meetings were at 2 different companies and with different principal engineers that both stated that the SEPIC design did not meet the isolation requirement.
In the end the size constraints, mainly height, pushed one of the designs away from a flyback and the principal engineer okayed the design so long as a common mode choke was added to the output of the SEPIC in question.
Most of the textbooks and articles that I have read categorize the SEPIC as an isolated topology, thus adding to my confusion.
What I do know:

"You won’t find a complete analysis of the Sepic converter anywhere in printed literature. What you will find are application notes with comments like, “the Sepic is not well-understood.” Despite the lack of documentation for the converter, engineers continue to use it when applicable" Analyzing the Sepic
Converter-BASSO
All of the reference designs on the TI website list the capacitor isolated topologies as non-isolated!. (PMP10070,PMP30373,PMP30373,)
Energy/isolation is handled by different means with a capacitor vs transformer. (High level only though, i.e. charge/discharge vs magnetic field transfer.)

My questions are as follows:

Is a SEPIC,CUK, or ZETA converter truly an isolated converter?
How does capacitive isolation compare to transformer isolation?
How could the common mode choke alleviate any isolation concerns?


texts: Usage of 555/556 Timer as a One shot timer

texts:
Im using two 555 timers / one 556 timer IC for a project. I've used it a couple of times before but never in monostable mode. Basically I need to activate a DC Motor in one direction for a set amount of time and in another for another amount of time with an H-Bridge. However the input for the 555 timer is not a button but a longer signal. Can the Signal of the 555 turn off while the trigger is still high? Should not be possible right, because the flip flop would have two high inputs ---> invalid... If this is true how could I easily shorten the long signal to a "button press" or might it be easier to use a JK flip flop?
Sadly, I can't really test this due to delivery dates, could someone validate my hunch or give me some additional advice?
Thanks and have a great day


texts: Realloc wasting lots of space in my MCU?

texts:
I am writing a simple task scheduler and using dynamic memory allocation on my cc430F5137. I agree that it is not a good practice but for the time being lets assume it is my application requirement to use dynamic memory allocation.

In my OS.c file

I have two structures,

typedef struct
{
    task_t task;
    uint8_t next;
    uint8_t prev;
    uint8_t priority;

} info_t;

typedef struct
{
    task_t task;
    uint8_t index;
} index_t;

size of info_t is 8 bytes and size of index_t is 6 bytes.

Also I do

index_t* m_index;
info_t* m_info;

Then I have initialize function in which I do

m_info = NULL;
m_index = NULL;

Now I have a function registerTask(& task) which takes address of the function to schedule. In this function I do

m_info = realloc(m_info,(num_registered_tasks + 1) * sizeof(*m_info));

and then set the values of .priority, next,task and prev.

Then I do

m_index = realloc(m_index,(num_registered_tasks + 1) * sizeof(*m_index));

and set the values of task and index.
 and do num_registered_tasks++;

My Question is that how is realloc() behaving in this regard.

Suppose my memory space,
First Task is registered, so It will have first 8 bytes for m_info[0] and next 6 bytes for m_index[0].
Now when my second task calls this function, what will happen? What I am guessing is that for m_info it will first look for 16 bytes of continuous data and will only find it after the first 14 bytes, it will change the address of m_info[0] and copy the contents and then add m_info[1]. And when m_index is called, it will only find 12 bytes after this (14 + 16) bytes and place m_index[0] and m_index[1] here.

If this is true then all my previous space is being wasted?

If I am wrong then how will this function work?

How can I utilize the previous space also?

I need index_t struct for implementing some sort of search algorithm so it is necessary also


texts: pcb bypassing and grounding for NC7WZ04P6X

texts:
Here is a part of PCB with 8 NC7WZ04P6X (UHS Dual Inverter, SC-70-6), and zoom on right...

Signal frequency should be up to 6 MHz. Near each (between) NC7WZ04P6X will be 0.1 uF 0402 cap, and 1 uF 0603 (maybe 0402, will see later). Ground line (blue) is going on bottom pcb side and VCC (red) on top. At the end (supply), there is 10 uF cap, between VCC and GND (and GND is connected to ground plane). Is this bypassing / grounding on pcb good enough?

Edit: Here is PCB with 2 local ground planes, VCC on top, and GND on bottom, with 0402 or 0603 1 uF cap.


texts:
I'm looking to add a Peltier element to one of my projects. However, I want to sometimes heat and sometimes cool, depending on the ambient temperatures on both sides of the element.

Image from Wikimedia commons.

My first thought was to use a H-Bridge and then reverse the power for reversing the flow of heat. However, looking at the diagram above, it looks like it may be polarized. (I have no idea, though.)
Conclusion one: since you'd be flipping the power, the P-type would act like a N-type and vice versa. This doesn't seem logical, but I've never taken an electronics class, so it may very well be true. P and N probably are treated differently (chemically).
Conclusion two: it is polarized because the P-type always has to be attached to the positive side (and vice versa) so you can't flip it.
Is either one right? Can I use an H-Bridge for this?


texts: Is it possible to extend the reach of a pn532 NFC/RFID shield?

texts:
I am working off an Arduino UNO with an AdaFruit pn532 NFC/RFID shield. The goal is to have a shoe box, with a false bottom. Under that false bottom would be my prototype, which hopes to be able to detect any mifare tag that is in the box, above the false bottom.

The range obviously for these devices is practically touching, but I was wondering if there is any way to extend the reach of the NFC/RFID shield, so that the entire false bottom of the box could act as that antenna?


texts: Calculating voltage at non-inverting input of the op-amp

texts:
I am asked to calculate the voltage at the non-inverting input of the op-amp if v1=4.78V and v2=0v.

I thought that the answer would be zero, as the voltage at the non-inverting input must be approximately equal to the voltage at the inverting input, and the inverting input is connected to ground. However, this is incorrect.

I would appreciate it if you could help me understand what is happening here. I have gone through some practice questions relating to op-amps with circuits constructed similar to this using the assumption that the voltage at the input equals that at the output, however, i am getting this question wrong.

Thank you very much for your time,


texts: Bi-Directional RS-232 / RS-485 translator using MAX3162 IC

texts:
I'm trying to communicate with an I2C bus using the Serial Card in my PC (NI PCI485/8).  I've created a circuit using the MAX3162 to translate from RS485 to RS232.  Then I use the MAX3232 as a level shifter to drop the RS232 to 3.3V.  Then it's sent to a NXP SC18IM700 to talk to the I2C bus. I've gotten the I2C working by using a USB FTDI cable for UART communication to the SC18M700 and have verified everything on the I2C bus and the SC18IM700 itself are communicating correctly.  I've verified that the message I'm sending from the PC (RS485) is being converted on the output of the MAX3162, on the input of the MAX3232, and on the output of the MAX3232.  However, nothing is being received from the SC18IM700.  I've removed the SC18IM700 from the circuit and attached the FTDI cable to the output of both the MAX3232 and MAX3162 to view the messages received from the computer.  When I try to send a message back from the FTDI port I'm not receiving anything back on the PC (RS485) side.  The MAX3232 is configured as it is so that the inverted RS232 is double inverted and will be the correct message to the SC18IM700.  I've tried using both the inverted and non-inverted messages and neither method is giving me a RS485 message back to my RS485 port.
So the root of my problem here is seeming to be in the MAX3162.  It's converting from RS485 TO RS232, but it is not converting the messages from RS232 back to RS485.  I can't find much help in the data sheets, but I've configured my MAX3162 just as they've suggested on one of the web pages I found (https://www.maximintegrated.com/en/app_notes/index.mvp/id/723)
I wish I could just use the USB FTDI cable for my final product, but I am unable to use USB communication for my finished design, so I need to figure this out.  It seems like I'm very close, but something is just slightly off...


texts: How do I interpret the setup/hold time on this RMII interface?

texts:
I'm coding the FPGA (MAC) side of an RMII interface between an Altera FPGA and LAN8720 device. Page 72 of the datsheet (pdf) shows the relevant timing diagram for this interface.

The input setup/hold values (tsu and tihold on the TX interface) are clear, but the output (which will be an input for the FPGA) setup time is not explicit. Instead there are two hold values. (tohold and toval on the RX interface).

How do I interpret these values and derive the setup time constraint for them?


texts:
Can a LED change colour over time?

I've had a blue LED set up for some time and it use to be a much brighter (ultramarine blue) now it's heading to a more greenish dull colour.  How is this happening?


texts: Fine points about the nature of bias current in oamps and experiments

texts:
In order to build a sensitive application, I am struggling to understand the behavior of the bias (and offset) current in oamps.
I always thought unconsciously that the input terminals of the oamp act more or less like a current source, and that the bias+offset current is the current sunk.
In fact, this may well be what LTspice thinks because the results of simulating the schematic below is a constant current through the cap (until Vcc+ is reached and then the current falls to 0).

The schematic below is a method proposed in the Art of Electronics to measure the bias current of very low bias current oamps. They says that this "worked well" for them. According to the book, the bias current is simply proportional to the voltage increasing rate by unit of time at the output terminal, which is easy to understand and seems also to enforce the idea that the oamp sinks a constant current.

Now, is this true? (question 1)

I've built the previous schematic and tested many different oamps. It appears that the truth is seemingly far from being that simple:

First, the voltage increasing rate at the output terminal is never linear, but seems to follow an exponential decreasing rate (like charging a cap at a constant voltage).

In one oamp (seemingly an imitation of the TLC662), the output voltage stabilizes about 1 V below Vcc+.
In the other oamps (OPA627,  TLC2272 and other), the output voltage stabilizes somewhere between 0 and Vcc+, and this threshold depends upon Vcc+; for example, for the OPA627, at 8V, the threshold is about 1.5V. At 20V, it is about 3V.

So, I looked at the schematic of the OPA6627 in the datasheet, I found that the input terminals are the gates of Jfets. This appeals the following 2d question: How is the gate of a jfet supposed to sink any current, except, perhaps, a few femtoamps due to leakage through the dielectric insulators, and disregarding the terminal capacitance loading ?

I would be happy to get thorough explanations of the oamp behavior described here.


texts: Why do we use a gray encoded signal by 2 stage flip-flop in asynchronous FIFO to avoid race-condition issue?

texts:
In the FIFO design, to compare the rptr and wptr, we are feeding one signal into another clock domain.
The rptr which is coming from the slow clock domain to faster one can be synchronized with sync Flip-flop logic explained in the beginning.
However, the wptr which is coming from fast clock domain to slower clock domain and it cannot be synchronized.
For example, If Write clock faster 10 times than Read Clock, then sync_w2r doesn't sample the wptr which is based on wclk.

AS you can see the above waveform, din[10:0] on the write(fast) clock is sampled by read clk clock(slow). and the din is a write pointer which is encoded by Gray.
and dout[10:0] is a signal synchronized signal by read clock(slow)
Actually Gray Encoded pointer signal(dout[10:0]) looks not having a continuously sampled by read clock. you can see the dout[10:0]. It causes a race condition problem. Even Gray encoded signal is synchronized by 2 stage flip-flops. but gray encoded signal does not work to avoid race condition issue at the each of edge sample clock. 1(sampled)-3-2-6(sampled)..go on.. it's actually 2 bits signals were changed from 2'b001 to 2'b110.
how can we explain the Gray encoded signal can be used to avoid a race-condition problem?
How is the problem solved?


texts: Why i get invert signal when pass through the mosfet

texts: I'm about using LT3092 circuit as my dc current controller. Firstly, i set the pulse from Arduino about 1kHz and directly connected to the mosfet VN2222L. I want the pulse as i set that should be rising but unfortunately when i measure signal of pulse at the drain leg of mosfet, the pulse is inverted. Please give any suggestion and your help are greatly appreciated. Thank you


texts:
Can I use pins muxed to different modes on the same header using a device tree overlay?

E.g., could I take my Beaglebone Black's P9 header and mux pins 28-31 to mode 3 for SPI, and pins 11-16 to mode 7 for GPIO? Or is it the case that must the entire P9 header be used in a single mode?


texts:
I know there are tons of these questions here, and I looked at them, but I still feel unsure about some things.

I've never designed anything using a MCU - for this one I mostly followed the recommended circuits from datasheets. My main question is about the power distribution - sometimes people use many caps, sometimes none, why? Why is the ground supposed to be on VSS pins decoupled with a cap to VDD(+3V3)?

It costs 100$ to buy and ship some of the parts to my country, and I can't risk it... so if you catch anything else wrong please tell me.


texts:
Below the SOA for the IXFP6N120P:

And the SOA for the IRFBG30:

The first one shows a DC line beyond 100 ms, but the second one does not. Does this mean the second one is unreliable beyond 10 ms, or the manufacturer decided not to put a DC line assuming the area beyond 10 ms is safe?


texts: How does ground affect a circuit with a diode, connected to the power source which is connected to a ground and an LED for it to act like a NOT gate?

texts:
I was searching for a way to use diodes to make a NOT gate.
I found a circuit online and simulated it in an application.
The configuration has a battery (1),where the negative terminal is connected to the cathode of a diode and the positive was connected near the ground (1) of the circuit. The ground (1) was also connected to the cathode of the diode.
The cathode of the diode was connected to the anode of an LED and the cathode of that LED was connected to the positive of the second power source and goes to the second ground (2). The negative terminal of that second power source was connected to the anode of the diode I mentioned earlier which goes down to the ground (1).
I tried to analyze what was going on.
I turned on the switch on the left, and the LED turned off. I turned the switch off, the LED turned on. I removed the ground and the outcome changed. The circuit does not act like a NOT gate anymore. What is happening?


texts: What USB-2 cabling hardware do I need to connect two Windows 10 computers together?

texts:
I want to run a .NET app in each of the two computers, so that they send and receive data through USB-2.

What kind of cable adapter will do this?

BACKGROUND:
I need to build a GUI on Windows that communicates through USB-2 with an embedded EFM32 ARM on our embedded board, which is not available yet.  so, I want to simulate the embedded with a .NET app running on my Windows 10 laptop and communicating through USB-2 to my .NET app GUI running on my Windows 10 desktop.


texts:
I have found this awesome Raspberry PI FM transmitter project. It uses RPi GPIO pin to simulate FM signal. After some filtering to smoothen it, this could act like a real transmitter.

But at this moment, I've problems with signal quality. I'm in a big city where lot of wandering signals are present. As well, the range seems not to be as large as anticipated.

I was wondering if I could, right now, create a simple amplifier using just a transistor. I have several random transistors of unknown brand at home - most of them residing in old PCB boards.

Could I use normal transistor (well, a fast one) to amplify such high-frequency signal? Wouldn't the signal penetrate through transistor (or the supply into my Raspberry)?


texts: Calculating how many times TIMER1 will overflow

texts:
I'm trying to understand how to set up an overflow interrupt on ATmega328 TIMER1 to measure a frequency.

I'm feeding pin PD4, which is where TIMER1 is externally clocked, with a 503kHz square wave (4.8Vpp).

Given that TIMER1 is 16 bit, I would assume that it would overflow 7 times every second. My reasoning is the following:

$$ number\;of\;overflows = \frac{f}{TIMER1\;max\;count} = \frac{503,000Hz}{65,536} = 7.67$$

However, my program counts 988 overflows instead. That's 128 times more than I expected. Why??

I'm using the following code:

volatile unsigned long int running;

ISR(TIMER1_OVF_vect) {
  running++;
}

void setup()
{
  Serial.begin(9600);

  // set up the 16 bit timer as an external frequency counter:
  TCCR1B |= (1 << CS10)|(1 << CS11)|(1 << CS12); // External clock, rising edge
  TIMSK1 |= (1 << TOIE1); // Enable overflow interrupt

  sei();  // enable global interrupts
}

void loop() {
  running = 0;
  delay(1000); // wait 1000ms
  Serial.println(running);
}

Below is the external clock signal on the scope:

The schematic I'm using is this one below. The inductor is 220uH instead of 68uH.


texts:
I have finished my PCB Design, but I have some doubts about polygons. The stack layer is: Top, GND, PWR and Bottom. On PWR layer I have created 4 polygons for 4 different voltages (5, 3.3, 3.3VDDA and 1.1 V). The brown layer is GND (the down black box is for Raspberry Antenna) and blue layer is PWR. The GND layer is one polygon. Is that the way to that?
I had to connect one component by trace because I couldn't expand the polygon through all the pcb for one component).

EDIT: The PCB is a Raspberry Compute Module 4 Carrier with an USB 3.0 Controller, with SuperSpeed Signals.


texts:
I was salvaging a motor / gearbox from a breast pump and noticed something I didn't understand at all. The control panel consists of a 6 position switch (5 speeds and off) and then a series of diodes. No resistors, no capacitors, and no 555 timer. It doesn't seem to be a PWM situation, so what am I not understanding about diodes that let them act as a speed controller? I thought their only function was to limit power flow in a single direction.

I also got a couple 1/2 horsepower DC permanent magnet motors for a go kart project and wondering if this information could be useful at all on a larger motor.


texts: Should I be worried about a surge protector near my pillow

texts: I have just realized how close my surge protector appears to be to my pillow. It is about 20-30cm away. Should I be worried about any EMF/radiation/something else? The surge protector itself is new and wiring is fine.


texts: Latching Priority Encoder, circuit works but I don't trust it

texts:
I added a schematic even though the question is actually too simple for it.  The datasheets for the devices are likely to be more revealing.
The circuit is super simple.  I have a 74HC148 priority encoder.  I attach its encoded outputs (A0..A2) to the parallel load inputs (P0..P2) of a 74HC193 counter, and strobe that word into the 74HC193 by connecting the GS output from the 74HC148 to the /PL input of the 74HC193.  (I am not actually using the counter as a counter, just as a quad latch, though this probably doesn't matter.)
When one of the inputs to the priority encoder is activated, GS goes low then snaps back high when the input is released, which is why the latching works.  It does this just barely a few nanoseconds before the A0..A2 outputs resume their previous state.  It's a race condition being won.
I have experimented with this a lot and have 3 handmade circuits in operation based on it, all working. I have tried changing the 74HC193 to different manufacturers versions (but not the 148 because I don't have other types handy). I have even tried the same circuit with all LS TTL ICs.  All have worked wonderfully.  I even tried a variation where I used a 74HC75 quad latch being strobed by the E0 output of the priority encoder, and as I recall, it worked too.
So here is my problem, and big question.  I want to go to some expense now and include this circuit in a manufactured product.  I read the datasheets and realise that under some interpretations my circuit shouldn't even be working at all!  Even though I am winning the race condition every time now, it doesn't mean I will always be that lucky in the future.
Maybe I just am not skilled enough at reading the datasheets, and it is in fact safe for me to assume that this trick will keep working.  Or maybe the opposite is true and I should add some persistence to the A0..A2 outputs in any mass-produced circuit, just for safety.
The big question is, "is it likely to be the case that this race condition will always be won, or should I do something more to tilt the odds in my favour?"


texts: Incorrect voltage and VAS biasing in audio amplifier

texts:
I've a problem in the VAS stage of an audio amplifier.

NOTE: "{V}" is 47ohm.

I've done several simulations, all voltages in real model are ok except one:

Marker "B" and "V-" is 0.7V (OK)
Marker "C" and "D" is 0.6V (OK)
Marker "A" and "V-" is 0.1V (not OK, should be 0.3V)

I don't know why the voltage is not ok, the current flow in the VAS stage is only 2mA, should be 6mA.

What is wrong in this configuration?


texts: seeking a high-current, common-anode LED display driver

texts:
I am seeking to drive a seven-segment common anode LED display in which each segment (setting aside the decimal point) should be regulated to 78mA or thereabouts. (The digit is 12" tall, hence the high current.) I'd like to send the data to the driver in some serial format, though I am not particular about which. I'm driving Betlux model BL-SE1200B-11UHR (datasheet); the manufacturer didn't reply to an emailed query.

I have not found any common-anode driver capable of anywhere near the required current. A candidate would've been Maxim ICM7212 (datasheet), but it only drives up to 8mA per segment. Or, the Maxim 7221 (datasheet), which can sink a maximum of –45mA per segment, so is getting closer to ,y current carrying needs—but is configured for common cathode use.

Are there any commercially available chips to do this job? (I'm driving six of these digits, so preferably the chip is available in DIP package for easy hand soldering.) Or must I build a driver, combining a demultiplexer with a series of transistors each switching a current limiter for the segments? Or is there another, simpler approach I'm overlooking?

Thanks!


texts: Determining \$I_{peak}\$ and \$f_{min}\$ and \$f_{max}\$ for MP4569 buck IC

texts:
Trying to figure out what inductance value is needed for my application of MP4569.
They give the minimum inductance value in terms of \$I_{peak}\$ (page 12):
\$L_{MIN}={{V_{IN(MAX)}{\times}t_{ON(MIN)}}\over{I_{peak}}}\$
and the datasheet says "the Ipeak is fixed, for given input voltage and output voltage"
I understand that \$I_{OUT}\$ cannot be more than half \$I_{peak}\$ with this converter because it always waits for the \$I_{L}\$ to drop to zero before each new cycle, but I don't understand how to determine this fixed \$I_{peak}\$ value based on \$V_{IN}-V_{OUT}\$.
The datasheet also doesn't give the switching frequency range, just one clue in the "Steady State, \$I_{OUT}=0.3A\$" figure on page 7 where the switching frequency is 100 KHz.
How do I determine the fixed \$I_{peak}\$ value based on my \$V_{IN}-V_{OUT}\$ value for this IC?
(I've selected the part based on the high input voltage range and availability from LCSC)


texts: I have a servo motor with a torque of 10kgcm. My question is how much weight can it carry? I really don't understand "kgcm." Is there a way to calculate how much weight can a motor carry?


texts:
This question is further to my previous question: Alternatives to SPI because of EMI. I am toying with the idea of designing my own communication bus. I would be grateful if someone could cast their eye over my preliminary design, and tell me where I'm crazy...

I am currently using 2MHz SPI carried over 10cm long wires to seven ADCs on separate PCBs (shared CS, but each ADC has its own MISO line. It's bit-banged), but would like to replace it with something differential to reduce EMI. Problem is that there aren't many ADCs with a differential bus, so I am wondering if it's possible to design my own bus. At least the physical layer, and possibly the protocol too.

Design goals of the new bus:

use physically small components
low EMI
no more than 4 data wires (two pairs)
bandwidth of > 300kbps from each ADC. (>2.1mbps total)

Before you write me off as crazy for thinking about this, consider that it may not be so hard to do on a PSoC5. On that chip I can certainly design my own protocol in Verilog and have it implemented in hardware. And to some extent, I may be able to include the physical layer components too. What's more, I may be able to have seven of these things at the same time, all running in parallel in the master, one to each slave so that I can get good overall bandwidth.

And here is my preliminary idea:

It would be based on I2C, slightly modified to help it connect to the physical layer components. The SDA and SCL lines are now differential pairs. The SDA pair has the OR-ing property. This is achieved using one pin which can only drive high, and one which can only drive low. The SCL pair is driven exclusively by the master. The data rate would be turned up to at least 1mbps.

The master would be a PSoC5 with 7 master modules. The slaves would also be PSoC5s, with one slave module, and would use the integral ADC.

Thoughts:

Not too sure what's the best way to implement the pull up resistors and slew rate limiting components.
I assume I don't need any termination. If I limit the slew rate to about 80ns, it should be good for a 10cm long cable.
That is obviously not a proper differential transceiver. Am I wasting my time trying to make one out of gates?
Those Not gates cause some skew. It this likely to be a problem?


texts: Which way of winding the toroid ferrite ring is correct?

texts:
Following my previous question I'm trying to prepare a test to see the effect of a torodial ferrite ring. The setup will be simply as below:

simulate this circuit – Schematic created using CircuitLab

But I'm not sure which way the wires should be wound around the toroid.

Which one below is correct:

Photo 1(wires wound together):

Photo 2(separately wound):

I want to vary the sine wave of the function generator from 1MHz upto 10MegHz and observe the attenuation on scope. If the setup is fine, which way of winding if correct? Photo 1 or Photo 2?


texts: Do metals with different electrical conductivities have different succeptibilities to induction?

texts:
If you have an inductive levitation coil and you gradually increase the strength of the AC current to the coils, could you fraction off metal powders by levitating each of them separately due to their differing electrical conductivities and thus different susceptibilities to electromagnetic induction?

I.e. will certain elements levitate before the others at differing induction levitation coil strengths due to their differing electrical conductivities and thus succeptibilities to induction?


texts: Is there a formula for electric serial connection with different voltage/current?

texts:
I installed a Solar pad(24V/9A/220W) and connected to my grid-tie inverter. and I'm planning to install another, but due to space problem, I may not be able to add another panel the same size...

so I drew a diagram(sorry for the sloppy drawing - dont know electric circuit symbols) on how I'm planning to connect the new one. If I get to install 24-volt solar panel then I'll just connect it parallel, but dont know...

So anyway, this is the question:
If I connect the lines like that, how does the electric output comes out? 36volts? and the current?
Is there something like a formula I could use to calculate?

I think the inverter itself could handle extra volts, since it said it could take up to 60 volts....


texts: GPRS modem gets stuck/hangs up when "AT" is entered

texts: I started working on a U-blox LEON-G100 gprs modem connected to the PC terminal through UART. Whatever character I enter into the terminal gets echoed back except "AT". When I enter "AT", the modem  hangs up. Then I have to reset the modem to make it respond. So, I cant even execute a single AT command. As it echoes back every character I enter until "AT" sequence, I think there is no the electric connections and the UART port settings must be correct too. What would be wrong here? I had experience with other GPRS modems, but this is the first time I am encountering this bizarre trouble.


texts: LOW and HIGH definition for Enable pin of 4051?

texts: Suppose we have connected an X volt (X=10) as the supply of a 4051 MUX (which is active LOW), can we disable the device by applying a B volte (assume B is 5 volt). In other words, how high is HIGH relative to the supply voltage?


texts: Building a simple line out from a mcu DAC

texts:
I'd like to get audio (specifically a line out) from a Cortex-M4 10 bit DAC (LPC-4337). The dev board I'm using already has a 470 Ohm resistor in series with the DAC. Since I've never worked with sound I'll appreciate any advice on the following:

1) How should I bias the 0-3.3v DAC output to an AC wave centered at 0v?

2) Should I block DC with a polarized series capacitor at the output?

3) How could I electrically protect the mcu DAC pin?

I only have 5v, 3v3 and ground available, no negative voltage.

I suspect a single supply, unity gain op-amp with bias will do, but I've never used an op-amp for this application. An example will be very appreciated.

Thanks in advance!


texts: How to display unroutable tracks early in eagle autorouting process

texts:
I felt like I spent a week trying to route the same circuit. I then look in the manual for hints, and it talks about how the status of the autorouter includes the number of tracks that it believes are unroutable. The value in the status bar is "conn: aa/bb/cc" where cc is the number of unroutable tracks.

Rather than me wait several minutes until the router has exhausted all possible connections, is there a way that the moment I see it can't route a track I could just stop it and have it display only the airwires showing what can't be routed?

selecting the ratsnest tool after stopping the autorouter will not work because that will make all unfinished tracks as airwires, not just the unroutable ones.

and idea?


texts:
We are planning to purchase a stencil for our LED boards. This will be my first stencil purchase so I don't have much idea about a good or bad one.

The inquiries I received typically suggest two materials: Phosphor Bronze or Steel. Steel ones are charged at 100$+VAT, while Phosphor bronze are about 65$+VAT.

The product is a high volume one, so the stencil will be used a lot. Also, per the info given to me, the holes on phosphor bronze are acid etched, while steel is laser cut, so there may be some roughness on phosphor one. We are not making a space shuttle PCB though, just some 2835 LEDs, so I guess this should be OK (again, just a guess)

Question is: what are the advantages of steel over phosphor bronze? Is the price worth the cons: durability and quality-wise, or is it just a trap?
Should I have any concerns about end product quality if I buy the cheaper option?


texts: Solution for broken pin repair (SMD(SMT) components)

texts:
While I was working with a IS62WV51216BLL-55TLI, I broke off by chance a pin at the base near the component body. that's perfect! LoL!

It makes me to think about this question:

Can we fix such problems? I mean Can we make a connection between the board and the broken pin of the component?

A good news, fortunately there is just one broken pin. well I was thinking that by an thin L-shaped wire we can make a connection. how about this idea? something like this:

Do you have a better idea? I'm completely quiet and focused to hear your ideas!


texts: How can I determine the signal level needed into a given antenna to produce a given magnetic field at a given distance?

texts:
I have an ETS Lindgren 6511 loop antenna that lists a magnetic antenna factor of -2.5 (best I can read the graph) at our frequency of interest.

I've found lots of information on establishing a given electric field, but nothing that speaks specifically to magnetic fields.


texts: cannot figure what is the gate for this CMOS realization

texts:
i tried the to figure the what is this gate but i coud not it seems to pass one or high impedance on positive clock depending on the input and zero or high impedance on negative clock

put i can't figure it's type nor pass transistor realization

original image


texts: Easy way to close 4 contacts at the same time

texts:
I'm building a smartphone rig to check the smartphone camera quality, focus and shutter speed.

This is my RIG, I have 4 bluetooth remote paired and I solder to the buttons some wires. If I take a single couple of wires and I put them in contact the smartphone shoot a picture, but If I group the wires together they doesn't work.

I need to close the 4 couple of wires at the same times keeping them isolated one from each other. I cannot find a 4 way button.

Any solution?


texts: Can I interchange TIP3055 emitter & collector to avoid needing to insulate the heatsinks?

texts:
Using three TIP3055 transistors for RGB LED switching. Collectors are tied to cases.  They need to be heat sunk and everything's already mounted and assembled and I don't have time to get rubber isolators.

Surprisingly it seems to work if I tie the collectors to ground and put the LED loads between the emitters and +12v. Running just a few LEDs right now to test the Arduino circuit, but I'll have around 4-5 amps of current through each transistor when finished. Is this safe or am I going to have a meltdown when I ramp up the current load?


texts: Voltage regulator 'hiccups' when gate pin of MOSFET is touched

texts:
I've been struggling with the following circuit which includes a Raspberry Pi:

That's a 5V voltage regulator (with protective capacitors), and a DC motor over on the right, and an IRF510 N-channel MOSFET toward the bottom.

The 9V supply is actually a plugged in 9V supply, so battery death isn't an issue.

The problem in some way is stemming from the presence of the Raspberry Pi.

A voltmeter is clamped and measuring voltage between A (output of the voltage regulator) and B (ground of the circuit)

This voltage normally sits at about 4.94 ~ 5 volts.

Now, I touch the two wires in the dashed box. This should simply kick the MOSFET over, allowing the motor to run. And it does that. Except there's a small hiccup. The voltage reading (A to B) drops momentarily to about 1.0V, the Raspberry Pi turns off, but then the voltage (A to B) comes back up, the Pi reboots, and the motor is running. I disconnect the wire and the motor stops. Everything is fine.

Replace the raspberry Pi in the picture with a regular resistor and the hiccup doesn't happen.

Now I would say that the most likely cause is some sudden spike in current is happening, overloading the voltage regulator's 1.5A rating. But I can't see what would be causing it. Measuring the current out the regulator when the Pi is idling gives only about 0.35 A. I can't see how touching the other parallel wire there would cause some surge in current.

Furthermore, everything works fine after the hiccup!

So I'd be extremely grateful for any clue as to what might be happening! Thanks for any advice!

EDIT:

Measuring the voltage across the power supply (where it comes INTO my breadboard)'s positive and negative terminal during the touching of the wires ALSO shows a drop from 8.98 V all the way to around 2V and then goes back up. Now I'm even less sure of what's going on!

And just to clarify - this is a AC to 9VDC converter plugged into a wall outlet; the wires go directly into the + and - rails of my breadboard.


texts: What is the minimum size of multiplexer needed to implement any boolean function of n variables if we are given a multiplexer and an inverter to use?

texts:
The following is the solution given.

  We can use n-1 selection lines , and using 0,1 and nth variable and its compliment to realize the function So ans is 2^(n-1):1

I'm unable to understand how it exactly works. If we have a function of say 3 variables. We can have 8 input lines for the multiplexer. If we take 2 select lines as per the solution, we can choose only 4 of the inputs.

I assume that using the inverter, we are somehow connecting the third select line which will double the possibilities to 8. But I'm unable to get a clear idea of how the connection is made.

Any help is highly appreciated.


texts: Are there safe ways to run an induction motor rated for 50/60 Hz at a lower frequency?

texts:
I have an induction motor that is rated for 50/60 Hz, with full-load amperages of 1.85A / 2A respectively.
It is not rated for any other operating frequency.

If I connect it to a VFD, will it be safe to run at say 40 Hz,
assuming a linear relationship between the frequency and full-load amperages?

i.e.: for full-load amperages (assuming average RMS value between three phases),
if 60 Hz = 2A, and if 50 Hz = 1.85A, so perhaps 40 Hz = 1.70A?


texts: Is ceramic capacitor suitable for snubber?

texts: Is there any Problem to put a ceramic capacitor (0.1nf/2kv) in a snubber circuit.


texts: The best way to trim a wheatstone bridge digitally?

texts:
I am building a Wheatstone bridge for strain gauge measurement. Due to component deviations a wheatstone bridge will often show an offset which needs to be trimmed:

If we assume that we're using 5% resistors, the worst case would be that R1=950ohm and R2=1050ohm, making the reference equal to 1.575V (when Vcc=3V), which will through the measurement way off - expecially when amplified 1000 times. So my question is, what do you think is the best way to trim such an offset digitally?

I want to be able to trim and calibrate the bridge with a microcontroller.


texts: Where do the oscillations on the output voltage of my buck converter come from?

texts:
I am currently building a buck converter. Its main parameters are the following:

24V input
5V/3A output
Able to sustain large load transient currents caused by the switching of power LEDs (~2A)

I selected a synchronous buck converter from TI which fits my needs in terms of electrical characteristics, package and cost: the TPS54302. The first prototype was designed following the datasheet recommendations and formulas. The routing of the PCB was done imitating the converter's evaluation board.

Here are the schematics and CAD:

(4 layer board, layers 2 and 3 are hidden. They respectively contain GND plane and supply plane)

There are additional capacitor footprints on this design to be able to test different component configurations.

When I actually tested the board, I was satisfied with the main characteristics: efficiency, output current and voltage, input and output ripple.

However, I wanted to test the stability of the power supply and this is where I started observing unexpected behaviors. I don't have any network analyzer or signal generator available, preventing me from measuring the phase margin. Instead, google researches suggested I measure output voltage variations while applying a transient load current (~1A transient with a rise/fall time <1µs). Fortunately, I have a MOSFET driving a power LED on my board. I just had to short-circuit the LED to generate a transient current.

The schematics below show my test setup where MCU_GPIO_1 generates a PWM signal, and MCU_GPIO_2 is continuously set to a high level.

As you can see, there are significant oscillations on the output voltage when the current load is released. In order to understand the origin of these oscillations, I conducted the following tests:

playing with the value of the feed-forward capacitor C10
changing the input capacitor configuration (more MLCCs)
adding a ferrite bead in series with the 24V input (in place of the D2 protection diode)
changing the output capacitor configuration (multiple MLCCs or 1 big polymer capacitor)

So far, these "blind" tests led me nowhere. I am looking for new leads to understand what's going on here, before starting the second run of prototypes. So, here are my questions:

How can I have oscillations only on the current release and not on the current draw?
What could be the deficient element here: routing? Input filter? Other?

Thanks for your help :)

PS: this is my first question on StackExchange. Any advice on improving the form of my question is welcome :)

EDIT : Andy Aka gave the answers in the comments: it's an issue related to the bad earthing of the probe. This picture sums it up:

Image source

You won't catch me making that careless mistake again!


texts:
This little cramp on connector is something similar to butt connector, but has extra leg, i.e. like 3 way butt connector.

I want to take existing wire and attach to it, or connect to it in paralel without tools. I imaginee it would be something I would take with pliers and crimp on it and it would give me extra wire out of it without soldering.

Is there any specific name for this kind of connector?


texts: A NAND flash sector suddenly goes bad. What happens to the file using that sector?

texts:
I can read a lot about how NAND flash can be checked for bad sectors, which are flagged and won't be read/written to in the future, but happens at the moment a sector goes bad? Any file that was using that sector would have to be lost wouldn't it?

What happens to that file? Does it just disappear from the filesystem entirely or does it remain in the inode table but is now corrupt and unreadable?

Assume the file system is UBIFS if that's important.

EDIT: Here's some background for why I ask the question: I have some devices with UBIFS and I've seen two instances of a file disappearing (different file and different device each time). The file in both cases was just not there on the filesystem anymore. But I don't have a good explanation for how it happened.

I wanted to know if it was within the realm of possibility that a block on the NAND flash just went 'bad' (I was thinking in the sense that it was no longer capable of being written to/read to) and took the whole file with it.


texts: What's the point of buffering a peripheral

texts: I have seen in most modern microcontrollers that the peripherals are queued using a hardware FIFO. What's the point of getting a hardware FIFO? Most old microcontrollers like PIC and AVR doesn't have a hardware FIFO. Are there strong points that the designers design an FIFO queue at every peripheral like SPI or DMA or USART?


texts: Why do the motors for my Arduino RC car not respond to any command after the first command is received sometimes?

texts:
I'm making a mini RC car with an Arduino nano and wireless communication with RF433, with 2 motors with 2 motor drivers (L293D). I use 4 1.5V batteries to power the arduino nano and another 6V battery pack to power the motors, and use a joystick with an Arduino Mega to send commands.
I've written a program that sends specific digits when the joystick is in a certain position, i.e. when the joystick is "bent" to the front it sends a "1", a "2" is sent when the joystick is bent towards the back, and so on.

My problem is this: When I bend the joystick towards a certain direction, the RC car moves accordingly without problem; However, when I bend the joystick towards another direction (in other words send a different command), the RC car doesn't respond.
I took a look at what the RC car was receiving, and I've noticed that after the first command was sent (when I bend the joystick towards a certain direction), no more commands get to the RC car (in other words the Arduino Nano). This occurs occasionally, and I can't afford to have defects like this. I think this means the Arduino Nano "froze" after the first command.
Is this because of not enough voltage or current? Are there any alternatives to 4 1.5V batteries that are not pricey (I need to build 8 of these RC cars)?

UPDATE: These are the pictures of my breadboard and whole thing. Though I doubt it'll help.


texts: Let high frequencies pass through Transistor

texts:
I would like to know if there can be any problems when high frequencies(500MHz) pass from the emitter to the collector in a transistor. Example: 2N3904 (NPN).

I know there are a few limits with the frequency on the base, which switch the transistor, but just wanted to know if there is anything you have to keep in mind when letting high frequencies passing from the emitter to the collector.


texts: Transformers headroom and "mandatory" components

texts:
I have calculated the maximum (Worst Case) current consumption of my circuit to be 88mA. Looking at transformers I found one at an specified max output current of 90mA for parallel winding which is my case. The next available component has a max current output of 200mA.

Q1: am I cutting it too short if I select the 90mA transformer? is there any derating that I should take into account such as temperature or saturation current as for inductors?

Q2: On the primary winding connected to AC mains. Are elements such as a fuse and a Y2 capacitor mandatory to pass electrical certifications?

Thank you


texts: Voltage on VOUT of voltage divider not meeting calculation

texts:
I am building a circuit to measure voltages on a 4cell lithium battery. All cells are connected in series and have a nominal voltage of 3.8v per cell.

I'm using a voltage divider to drop the voltage down to 3.8 volts, so they can be read using the analog pins on an arduino.

simulate this circuit – Schematic created using CircuitLab

I'm a self taught hobbbiest and I don't understand why in the simulator and my calculations, I get an output voltage of 3.8 volts. But on a real breadboard The output voltages are closer to 3.5 volts.

From my research, possible causes could be:

Batteries will have a voltage drop when under load.

My batteries are outputting less than 400 microamps in both the simulator and on the breadboard. Seems unlikely to account for the large difference.

Account for internal resistance

I do not know the internal resistance, but the battery is brand new and high quality lithium polymer batteries typically have less than 5 milliohms per cell.

Please educate me. Why are the voltages off by almost half a volt? This circuit is the best I can come up with. If there are better ways to design the circuit, I would appreciate that feedback too.

Arduino read 24v signal
Lipo internal resistance
Lipo voltage circuit

Update

As suggested in the comments, I disconnected the output of the voltage dividers from the arduino. The output of the voltage dividers is now reporting the correct 3.8 volts. I still don't understand why that was the problem, or what the solution would be.


texts: Does bolting to aluminum for electrical contact have any oxidation concerns?

texts: If I bolt a transistor to aluminum for an electrical and thermal connection, are there any oxidation concerns for the electrical contact?


texts: Understanding resistors on inputs/outputs of op amps

texts:
I was looking at the schematic for Dave Jones' uCurrent, and I can't seem to make sense of why there are 270 ohm resistors on the inputs and outputs of the op amps in his circuit. The resistance is low enough that it wouldn't affect the filter in the feedback loop, and is negligible compared to the input resistance of an op amp.

Any ideas why these resistors are put in series with the input/output of these op amps?

Here's a snippet of the main section I was looking at, with resistors R12 and R8. The full schematic can be found here: Full uCurrent Schematic. Here's a link to full description of the project: Full uCurrent Design Article. The schematic is on page 16, and a short sentence on the resistor in question can be found on page 8 (search for "R10").

Dave mentions that he uses the resistors to provide "output stability". How exactly does this small resistor provide stability, and why?


texts: Followup question about "Using a variable resistor to dim an LED"

texts:
In the thread "Using a variable resistor to dim an LED", Phil Frost provides almost the answer I need, and even provides a great diagram, but he's working from a 5V supply.

My question concerns what the resistor values would be for a similar circuit running a red LED from a 3V power supply.  I'm pretty sure the fixed resistance would be less, and I know how to calculate the 'drop' resistance for a fixed-brightness LED, but I'm not an EE, and I'm not sure I understand the relationship between the fixed and variable resistance values in the circuit.

My project is a simple dimmer for a "unit-power finder" to be mounted on a astronomical telescope.  The LED does not need to reach its full brightness as it's being used to back-illuminate a film reticle which is being projected against the night sky.  Fine control at the dim end of the range would be a plus.

I'd use an Arduino based dimmer/pulser circuit, except all the good toys are still packed from a recent move, and I need something quicker and dirtier for the time being now that we're approaching prime observing weather.


texts:
I have on my circuit an integrated circuit (IC) that has been destroyed by some event. After the event, the component's Vcc pin was shorted to GND inside the IC.

After measurement, it appears that there is a surge spike on the Vcc (5V) net. Here is a screenshot of the measure I made on Vcc:

It shows that the spike can rise up to ~15V, but I have seen it over 20V. The half-wave last for approximately 1 µs to 1.5 µs.

The datasheet of the destroyed IC gives an absolute maximum value for VCC of max 6V. This is largely exceeded here.

To protect the ICs, I have thought to use a TVS diode such as SMAJ5.0A/CA (5V stand-off voltage). But such a diode have a minimum breakdown voltage of 6.4V, typical 6.7V, which is sill over the absolute maximum ranking for VCC of my ICs.

Will this protect the ICs, despite that the fact that we are still a bit higher that the spec ?

Do you know know an other mean of protection for the ICs ?


texts: Connect a vibration motor to a headphone jack

texts:
I would like to solve the following problem:

I have a a variometer-device for an RC plane. Its receiver has a standard 3.5 mm headphone jack that provides a beeping sounds to my headphones. I would like to replace the headphones by a "device" with a little vibration motor (just like those built into modern phones) so that I can feel if my plane climbs or sinks instead of hear it.

Now I assume that the receiver delivers an A/C signal to the headphones at a relatively low current, but I couldn't find any data about that on the internet. The vibration motor needs D/C and takes a current of about 200 mA.

Can anyone provide data what maximum voltage such a "standard" audio jack provides? What would I need to connect the vibration motor to it? Will I most likely need an extra battery for the motor and thus amplify and rectify the signal? What would be my best bet?


texts:
I have a device whose shape is a cube and I need to identify in real time which face is up.

My current solution is (not yet implemented) is to use a gyro to get angular variation, but I can see 2 problems:

Which face is up when the cube is "powered up"?
We can't assume that every 90° variation will change the face standing up. If is a variation in the "world" Z axis, the face remains the same. But the "world" Z axis is not equals to the gypo Z axis.

There is any way to accomplish this?


texts: How to represent socketed components in schematic

texts:
What method do people generally use to represent socketed components in a schematic, notably in this case I am referring to resistors & capacitors mounted into machined socket pins (multiple into the same strip).
There are three immediately obvious approaches but neither seem to well capture the intent, or lend themselves very poorly to reuse.

Draw the parts as usual, select a footprint certain footprint (0.4" Spacing in my case) that matches the socket. Then when laying out a PCB ensure all of these separate parts are correctly located.
This feels like a pretty poor solution in that the sockets will not show up in your bom and there is a lot of points for potential error

Insert a component into your schematic for the socket, and comment in the schematic what goes into it.
This seems poor as it greatly reduces the readability of the schematic.

Create a custom multi part component with each part having their own symbol (resistor in a dotted box or something), and link this to your footprint.
This method seems relatively foolproof but means a large number of one off components will be generated with minimal chance or re-use.

Presumably this isn't that uncommon a task, as it is seen fairly regularly in industrial electronics, how is this usually presented.


texts:
How to make 10mH inductor on my own?

It is not available in the market, can it be replaced with something else? I have to make a metal detecting circuit using a 555 timer IC.


texts: Does the value of the voltmeter change after closing the circuit?

texts:
At the start the voltmeter reads a specific value (I guess it is the value of the voltage of R2, right?)
Question:
If circuit closes, what value does the voltmeter read?
My answer is: It does not change!
Is my argumentation correct?


texts: Designing an over discharge lithium ion protection circuit

texts:
I am trying to build a portable RGB LED display that runs off a Lithium Ion battery. After a few days of research, I understand the importance of using a dedicated IC to handle charging the battery, but I am having trouble with the over discharge aspect.

If I want to monitor the voltage of the battery, I can use the ADC on the micro-controller, or better yet, find a charging IC that incorporates an over discharge feature like the DW01-P.

But if I disconnect the main load (the RGB LED) when the battery voltage gets too low, won't the IC or micro-controller still need power from the battery to run (i.e to keep the LED disconnected)? And wouldn't that cause the battery to further discharge and damage it?


texts: noise suppression methods for common mode 50Hz (power line) noise

texts:
In this document
it's explained how to reduce the common mode noise.
In my case I have common mode noise at 50Hz (from power supply) on the 12V CC line that I'd like to reduce.
Are both solution still applicable? I think the choke coils are useless at low frequencies and maybe also the Y-Capacitor.
Looking at method 2, I understand that the metallic casing must not be connected to the circuit GND, right?
Which kind of Capacitors are suitable for this application?
Can you please suggest me other solutions or place where to find this kind of information: I found a lot on internet but in order to reduce noise from circuit to power line and not vice-versa.
Part II:
The situation it's a little bit more complicated. Actually, since my device is connected to the network, the 12 volt power is delivered through PoE in the following way: network cable -> power injector -> network + power -> splitter -> network and 12VDC. So near the device, where the 12V is provided, I have no earth ground.  The power injector is actually connected to the earth but, I don't know why, the power over the network cable is really floating following the mains AC. I could change the PoE injector (and actually I tried with good results) but, since the client has a lot of these devices already in production, he can move my device in his network easily using this poor PoE splitter that works good for other devices and already in place.


texts: Am I insane to question that only with a closed path can electrons move?

texts:
First of all let me just state that I do not feel confident enough to tell anyone anything about how electric circuits work or anything about the physics behind them because I simply do not know or understand it all.

But I have many times read that there has to be a closed path for current to flow in a circuit, leading to a fact that if there isn't a closed conductive loop nothing can happen.

And I have taken that to be a definitive truth, but I wonder about something(and I might just as well be terribly far of the path of reason here).

If I was to design a circuit board which contains traces through which very high frequency signals(currents) will flow then I have to consider things like signal reflections, I don't know what reflections consists of in purely physical terms(but I have to imagine that a reflected signal is a certain amount of the current(s) that was originally sent through the trace) but apparently if I send a high-frequency signal down a trace(or wire) then under certain conditions the signal can travel down the trace(wire) only to bounce off of something and then travel all the way back to where it first came from. Where it might bounce off of something again and so it can bounce back and forth travelling the length of the trace over and over again getting smaller and smaller until it dies out.

This is just stuff from the top of my head, stuff that I have never acquired a fair understanding of in the first place. But if we restrict the scenario to this very high frequency situation, if a signal or current can be reflected back towards where it came then why would it even have to be relevant whether there are a closed loop or not.

Couldn't a broken loop present paths for such currents to bounce around in?

I know that I am at a relatively very low level of insight into these complex matters but I don't now why that wouldn't be possible.
I would be very happy if anyone could enlighten me.

I have one single hypothesis without anything what so ever to support it, but perhaps the very high frequency scenario alters the way that a traces copper is utilized so that it in some respect is a closed loop in it self?


texts:
I'm trying to understand turning a pwm signal to a analog signal.
From what I saw online I found that using a lowpass filter, the capacitor voltage is Vin*DutyCycle.
This was given as a fact and I was wondering where does this rule come from? From what equation?.
Thanks


texts: How can I "Ladder" Mosfets to disconnect balancing lines from a series of battery cells?

texts:
I have a battery which will remain connected in series, and I want to have an option to connect / disconnect the balancing leads electrically - something like this:

which will connect the batteries when the "active" line is driven high from an external power source (not the battery stack, only connection between the two as what's shown here, i.e. "common" ground when the connection is made, and high resistance when off, but then disconnect them when it's driven low (the resistor bridges are going to an ADC to then calculate each cell voltage)

The problem with this circuit is that when the active line is low, the gate voltages on the P-channel mosfets ends up being the same due to the resistor dividers that I want to remain there, and thus I need mosfets that can handle a large gate-source voltage difference. I am looking for a way to "chain" them or stack them in a ladder-like fashion where the voltage that the mosfets needs to handle is not related to the # of cells in the stack - what would be the best way of doing this?

P.S. - not shown here but I want to be able to actively balance the cells as well, so once I figure out their voltages I can selectively charge/drain the cells via these same balancing lines, thus I want low RDSon mosfets, which tend to have lower voltage tolerances


texts: What do the green and yellow wires in a BLDC fan do?

texts:
I rescued a box of brand new 'Nidec UltraFlo V60E12BS1A7-09A032 12VDC 2.45A' fans from being thrown away and of course I haven't got the datasheet for them. The closest matching datasheet is here: http://www.nidecamerica.com/fanpdfs/c2008_1314.pdf but I suspect mine are custom made for HP.

It has four wires:

black => GND
red => +12VDC
yellow => I thought this is tacho open collector to GND, but I can't measure any frequency on it both with and without a 10k pull up to +12V, it is near 0V all the time. On top of that the wire is as thick as both black and red, whereas the green wire is clearly thinner.
green => Seems enable (0V) / disable (12V or anywhere in between)

Does anyone know the proper specs for the yellow and green wires on these fans?


texts: Hello if unregulated power supply (transformer, bridge and main caps) is 30 cm away from the circuit to feed, is it better to put the voltage regulator close to the circuit (long input and short output) or close to the power supply (short input and long output)?


texts: LVDS Interface - Output Max Swing is Higher than Max Input Swing

texts:
I am connecting together two "LVDS" devices. The specs are as follows:
Output: VoDiff = 247-600 mV, Vcm = 1-1.485 (1.25 typ)
Input: VinDiff = 100-500 mV, Vcm = 1-1.6 (1.25 typ)
So for the most part they look compatible. However I am wondering if I should be concerned that the output can swing up to 600 mV and the input is rated up to 500 mV. Is this a concern?
The input has two 50 ohms to GND with a mid voltage of 1.25. So I am guessing I do not need any termination, but just concerned about the voltage swing.
LVDS receiver - Teledyne e2v EV12DS480A 12-bit, 8 GSps DAC
LVDS driver - Xilinx  Kintex UltraScale XQRKU060 FPGA. Please see p.27


texts: Using FFT for spectral analysis: How to convert from power to dBm?

texts:
I have the output of my FFT, an array of complex numbers, and each one has been computed to the magnitude squared. To my understanding, the magnitude squared is equivalent to the power, so in order to map to dBm, I would take 10 * log(x) of each of these numbers. This does not seem to give accurate dBm levels according to another spectral analyzer.

Converting to magnitude voltage, by taking the square root of the magnitude squared and dividing by the size of the FFT, and then taking the 20 * log(x) of this number seems to give closer dBm level when compared to other equipment. Why is this?


texts:
I purchased a "24v" solar panel thinking it would output only at 24v, or less if there wasn't enough light. Immediately tested it, in indirect light it's producing 38V. Checked the label on the back and it says:

Open Circuit Voltage (Voc): 43.5V

Voltage at Pmp 36V

On the box it says Nominal Output Voltage 24V.

I want to use this solar panel to power 24V fans, I'm worried providing that much extra voltage to the fans may shorten their lifespan. Is there something I can use to limit the voltage to no more than 24v? Is my concern about too much voltage to the fans legitimate?

Thanks!

Edit:
Would a product like this work for me?
http://www.amazon.com/DROK-Switching-Regulator-Adjustable-Stabilizers/dp/B00BYTEHQO/ref=sr_1_1?s=electronics&ie=UTF8&qid=1426729713&sr=1-1&keywords=24v+voltage+regulator
It says an input voltage of up to 40V. Is this too little because of the VOC? Or is it OK because the Voltage At pump is only 36V?


texts: Collector current and Vcc in saturated BJT

texts:
In the circuit below, the transistor is saturated. I know transistors don't
follow Ohm's law. But as it is fully on, I would like to know if I reduced Rc or Increased +Vcc, would Ic increase in line with Ohm's law, assuming the transistor
could handle the increased current?


texts:
Please assist me with this design problem

Design and construct a single stage common-emitter amplifier with the following characteristics:
 The voltage gain should be at least 100V/V;
 The input resistance should be at least 5 kΩ;
 The output resistance should not exceed 2,2 kΩ;
 The circuit must be operated from a +10V /0/-10V (split supply).
(Hint: consider the split-emitter also called the partially bypassed configuration)

Does the voltage divider biasing formulas apply to this configuration?
Where do I actually begin?


texts: What's the usage of storing recorded measurements of multimeter and soldering iron station in computer?

texts: Assume you want to purchase a multimeter for your job. some multimeters have a USB interface to store the recorded measurements in the computer and for this feature, you have to pay more money. but the question is What's the usage of storing recorded measurements in computer? sometimes I think that's a worthless feature, maybe bucause I never need to such feature. but I guss there is a reason for this feature. another device that I think have this feature and that's a worthless feature for it again is soldering iron station. for example: Weller WX soldering iron station indeed I'm curious!


texts: Microchip XC8: How to Overlap Specific Variables without Union?

texts:
I have effectively three sets of variables to put in two locations.  Sets 1 and 2 are never used together, so they can occupy the same space.  Set 3 needs to be unique.

I know I can use a union of structs to get what I want, but that's a lot of data to force into the same area, and it makes the names unnecessarily complex in my opinion:

union
{
    struct
    {
        ...
    } set_1;
    struct
    {
        ...
    } set_2;
} shared_variables;

I can also assign a specific address to each variable, but that doesn't allow any freedom for the linker to optimize them:

unsigned char foo_1 @ 0x1A0;
unsigned int  bar_1 @ 0x1A1;

unsigned long foo_2 @ 0x1A0;    //same address as foo_1

I can assign a section name to each variable and tell the linker what to do with the sections, but I still think it's too restrictive:

unsigned char __section("set_1") foo_1;    //set_1 is 1 byte
unsigned int  __section("set_1") bar_1;    //set_1 is now 3 bytes

unsigned long __section("set_2") foo_2;    //set_2 is 4 bytes

//linker: -L-Ashared_class=<address_range> -L-Pset_1=shared_class -L-Pset_2=shared_class
//actually concatenates them somewhere in the specified range (total 7 bytes), not sure how to overlay them (total 4 bytes)

Is there a way to tell it, "I don't care if this set of variables overlaps that set of variables, but this other set of variables must be unique," and just leave it at that?

Edit in response to comments:

Set 1 + Set 2 + Set 3 represent all the variables that are used in the entire project.
The code that uses them is currently spread across 4 source modules.
Like most if not all chips in this range made by Microchip, the memory is fragmented in hardware into 80-byte chunks separated by hardware configuration registers.  There is another addressing mode that requires a pointer to access all the fragments as if they were contiguous, but that would thrash the pointer registers a lot.  (and there seems to be a bug in the debugger that corrupts data that's used that way in certain cases; normal running is okay though)


texts: An COTS solution for delaying a 120kHz analog signal?

texts: Looking for some cheap method of adding a 350uS delay to a pulsed sine wave. It would be useful to emulate a pitch-catch ultrasonic distance measurement setup


texts:
How can I check the value of array input in Verilog? I tried this code but, I got an error "op_code is not a constant"

module mutlti_proccessor(data_out, flags, data_1, data_2, op_code);
    input [7:0]data_1;
    input [7:0]data_2;
    input [3:0]op_code;

    output [7:0]data_out;
    output [4:0]flags;
    /* flags[0]:ZF "Zero Flag", flags[1]:SF "Sign Flag", flags[2]:CF "Carry Flag",
       flags[3]:OF "Overflow Flag", flags[4]:COF "Compare Flag" */

    wire carry;

    /* Set falgs to zero */
    assign {flags[0], flags[1], flags[2], flags[3], flags[4]} = {1'b0, 1'b0, 1'b0, 1'b0, 1'b0 };

    if(op_code==00000)
        Ripple_Adder RA1(data_out, carry, data_1, data_2, 0);

endmodule

Where Ripple_ADD is another module that sums up two 8-bit numbers.Note: there is no clock.

Thanks ....


texts:
I just ordered some serial ram to use with my microcontroller. My micro is actually AT89C2051-24PU and runs on 4-6VDC.

The ram 23K256-I/P (according to the datasheet) runs on 2.7 to 3.6VDC.

From my schematic, I'm trying to control the RAM with GPIO pins P1.5 through P1.7 and read the status with P1.4.

I use a diode for the return data to prevent excessive voltage from the P1.4 pin from entering the RAM (or am I being too paranoid here?)

R1 and R2 is meant to be a voltage divider so that VCC for the ram is within limits.

I believe the 8051 GPIO pins only have the values high-impedance and ground, so I added pull-up resistors to the lower voltage to give a default value of 1 to the RAM input pins (unless I set any of the values to zero in the 8051 code).

Is the schematic satisfactory, and is there a better way to do this than to rely on resistors and the diode? I don't want to overheat and possibly burn the RAM chip. The simpler the circuit, the better.


texts: How big should my pads and holes be based on this datasheet?

texts:
I've been trying to decipher the many numbers on the top picture, and it just doesn't make sense to me.

Why would you need a hole of size 1.19 mm when the pins are only 0.45x0.58 mm? This leads me to believe that 1.19 mm is the size of the pad, but then how big should my hole be?

I made the pin holes 0.762 mm. That should work right? What about the mounts on either side? Because, if I'm following the logic I used to discern that the first number next to a hole is the size of the pad, then I'm still left without a size for the hole. Nowhere else on the datasheet do they say how large the mounting pins are.


texts:
I have a set of speakers which has been standing in a humid place for a few months. One of them still works perfectly fine, the other not so. The other speaker creates a very static noise, barely rendering it's audio source.
Following link is a recording of what it sounds like:
Good speaker vs bad speaker
The speaker consists of a sub and a tweeter, connected together by a bipolar capacitor. The circuit gets fed by a copper cable from my amplifier.
I've checked the copper cable ends, but I don't see any oxidization.
When I tap the cone, there's a lot of friction, whereas the cone of the other (good) speaker feels very smooth and reacts to my tap. I notice a very big difference between the two.
Does anyone have an idea what I should be looking for and what the cause might be?


texts: Designing an High Amperage, Low Voltage AC Voltage “Breaker” for Model Train

texts:
I’m trying to build a simple circuit that acts as a "voltage breaker" – meaning that if a voltage exceeds a certain threshold, analogous to a (current) circuit breaker it will open a circuit.  There are a couple of things that seem to make this a bit challenging because of its application – which is to serve as a speed limiter on a Lionel model train for my young son.  Little boys have a habit of turning the voltage up too high and running a train off the rails.

This implies a few constraints:

The supply to be constrained is AC, operating in the 8 – 16V range.
I’d like to limit the voltage (i.e., train speed) to about 13-14V in
a way that can be adjusted to account for different engines’
operating characteristics.
The current draw can be up to 5A on a regular basis.  Lionel used
universal motors until very recently and they can draw quite a bit of
current when pulling a consist of cars.  Other accessories also add
to the load as they draw power from the track.
The circuit needs to be able to withstand occasional (but not rare)
full shorts that last a few seconds, as it is not uncommon to cause a
short for a variety of reasons (such as derailments that connect the
rails).  The variable output transformers used (I have a 1940’s Type
V and a 1950’s Type ZW, for those who know of such things…) can
output tens of amps when shorted and take a few seconds before
triggering their internal thermal breakers which are usual in the
5-15A range.

Balancing all of these constraints, what I’ve been able to come up with is the below circuit which:

Creates an AC reference voltage that I don’t want my son to exceed.
This is my LimitAC voltage source at the bottom portion of the
circuit.  The do-not-exceed voltage would be set at the transformer
using one of the multiple controls.
Rectifies the AC in both the reference and track (this is my
TrackLevelAC2 voltage source at the top – more on the “2” in a
second) voltages, which I then…
…feed into a suitable op-amp comparator (likely a power amp, to
provide the necessary current to actuate the relay’s coil).  My
thought is that rectifying both sources will make the comparison
straight-forward.
When the track voltage exceeds the reference voltage, have the op-amp
feed a separate 12V DC supply that triggers a NC relay to open the
track circuit (ActualTrackAC1 and ActualTrackAC2).  I’m simulating
the relay with just a voltage controlled switch at this point.

A few questions/suppositions:

I’ve had to set up two identical voltage sources for the track to get
the full AC waveform instead of the rectified AC waveform. In the
real world, if ActualTrackAC1 and ActualTrackAC2 were one and the
same, wouldn’t the track and the rectifier-to-op-amp portions both be
able to operate independently?  Related to this…  EDIT: simple reference question.
…LTSpice doesn’t power ActualLoad (which I’ve set at 4 ohms, a
reasonable approximation for an engine) as I’d expect.  In the real
world I would be drawing a couple of amps from the transformer, not a
few microamps.  What am I missing here?  Isn’t an LTSpice voltage
component an “ideal” voltage source and thus capable of feeding
whatever current is required into the track circuit?  EDIT: simple .model error now corrected.
Do I really need to rectify the sources to get the opamp to function
correctly?  If I don’t, it would seem that the comparison will work
as intended on the positive half-wave but fail in the negative
half-wave (since the reference will be higher, i.e., less-negative,
than the track).

This all seems overly complicated given the conceptual simplicity of the goal, but given that I’m working with higher amperage AC and need to be able to withstand short circuits I seem unable to use solutions that are DC based, for low amperage, or are not very happy with full shorts (e.g., a simple Zener clipper – N.B. I’d settle for a clipper-type circuit instead of a breaker...)  This cannot be an uncommon need, but since I’m just a casual hobbyist – am I missing something?  Is there any way to improve this circuit?


texts: Need more current than 4 mA in 4/20mA loop current

texts:
We know that in a 4/20 mA loop current, 4 mA represent 0% and 20 mA represent 100%.
For loop current we use an IC like XTR115, and my circuit is fed from this IC.

If my circuit needs higher current than 4 mA to run, how can I obtain it?


texts: Why does an LED light up when I touch it?

texts: I have some super-bright LED components that I'm using in a breadboard project. To my surprise, I found that if I ground one leg of the LED and touch the other (unconnected) leg with my finger, it lights up very dimly.  Polarity doesn't matter.  Why does that happen?  There's no source of electrical power that I know of in this "circuit".


texts:
I would like some advice on a particular circuit design for a variable DC power supply.

Here is some information about what I want to do:

I want to do open and short circuit tests on an alternator to find it's internal impedance (Note this is a pure alternator with no regulator/rectifier. Similar to an alternator used on a 3 phase generator and NOT a vehicle). This involves me increasing the output voltage from a DC power supply across the rotor (which is just a copper coil with fixed dc resistance, so increasing DC voltage increases current and increases magnetic field strength) and then measuring the AC generator emf/currents (Also note I don't have access to the alternator yet so don't know what rotor field voltage/current is required).

I plan on using the 240v mains which will be rectified to give my DC power supply. I will start with being able to supply 2 amps at the DC output to start with for my tests and I intend to use the full AC peak voltage of 320V, so around 300vdc. I have used a 1:1 isolating transformer in case I need to probe my oscilloscope in the circuit. My questions are based on this and are listed below:

If I use a 240vac variac to supply my full bridge rectifier, I can simply vary the AC peak voltage and hence vary the DC output voltage. This will supply a constant voltage to the load regardless of the current drawn, as the AC current can increase and should work very well?

Is it better to remove the variac from the circuit and rectify the full AC peak voltage and use a variable resistor (hand potentiometer) on the DC side to vary the voltage? There will be a big power dissipation through the pot is the obvious disadvantage.

Or can I replace the series potentiometer in the circuit with a voltage regulator IC and use a potentiometer to adjust the output voltage? I doubt I will get IC to work from 0 - 300Vdc say for example?


texts: How to select the model selector for TI IBIS model of DRA725?

texts:
Following is the IBIS model selector section for the DRA725 SoC in IBIS file.

Currently, I do SI analysis of DRA725 with Mentor HyperLynx SI, Intention is to select the right model selector. What to be selected and what should be the selection criteria?

This is the datasheet link. I have checked against the info in the IBIS file and there is not much I could found.


texts: Simple LM317 variable voltage supply, does it limit current too?

texts:
I had wanted to build a power supply for so long, and had never really understood the calculations involving the LM317. I had found a kit (pcb+parts) online and it had renewed my interests in using it for a simple power supply that is adjustable: (LM317T) datasheet here:

Schematic the PCB is using here:

I understand that R2 acts as a voltage divider of sorts, And R1 is to send a specific current to the ADJ pin (1.25V ref / 240 on R1 = 0.0052A)

The issue is that using the stated formula the output is this:

$$ V_{OUT} = 1.25 \cdot \Big(1 + \frac{R2}{R1} \Big) + I_{ADJ} \cdot R2$$
$$ 1.25 \cdot \Big(1 + \frac{1k}{240}\Big) + 0.0052 \cdot 1k = 12V? $$
$$ 1.25 \cdot \Big(1 + \frac{5k}{240}\Big) + 0.0052 \cdot 5k = 55V? $$

Why does the formula fail, just using 1K (near minimum on the voltage adjustment pot) and 5k which is recommended maximum R2 value?

Now assuming I can get 5V in example after adjusting the pot in real use, will the 240 ohm resistor limit the current, or do I have to add something else on top of that afterwards? If it does (I can have var. voltage + current limit) I assume I will need to up the resistor power specifications as the current will flow through them (or my after-regulator limiter)

Specifically, I do not want a constant current source, because testing a home-made solenoid or a random LED I assume the upper current limit I set will let them work and not be destroyed. I want this because I wish to set a limit rather than force 500mA to go through something it does not want to by raising the voltage well above 5V for example.


texts:
I'm trying to understand why this arc lighter circuit is designed this way.

This is my understanding of this circuit: the PWM signal is 50% duty at around 18kHz. That generates a square wave at the primary of the transformer, which is stepped up into the kV range at the secondary.

Is it necessary to have a BJT and MOSFET together in this circuit? Could you achieve the same results if you remove the BJT and just place a current-limiting resistor at the MOSFET's drain?


texts: Configuring UART pins on Beaglebone Black for CAN Interface

texts:
I have been using a CAN/RS485 Cape for prototyping CAN control of a motor. I am now in the process of bringing up some custom hardware. I have a CAN Transceiver SN65HVD230D on this custom cape that is connected to pins 31 and 32 on P8 - UART5 TX/RX.
I tried simply configuring the pinmux using config-pin however I got two errors:
user@beaglebone:/lib/firmware$ sudo config-pin P8.31 can
P8_31 pinmux file not found!
Invalid mode: can

Is it necessary to create a device tree overlay as this question suggests?
Is it even possible to use these pins for CAN or is CAN only available through DCAN0/1_RX/TX pins?


texts:
I wanted to implement below formula into excel sheet. can someone suggest me with example.

cable equation
example : system voltage =12v, sys current=8A, length in feet=50.

Resistance = resistivity* length/ area

length = 50 feet

if we consider 26 gauge wire

diameter  of wire =0.0159 inch =0.001325 feet

radius =0.01325/2 =0.006625

a = pi* radius^2= 0.000137090

resistivity =1.68*10^-8

therefore wire resistance= 0.0060

but data i got is not matching with value in table mention. can you some one suggest what mistake i am doing

voltage drop

wire gauge calculation

I am not saying my answer is correct . If you check the online calculator i posted it gives right choise of wire gauge.

i am trying to impliment same thing in excel sheet.

Help i need is example to explain the choose correct value & get answer similar to the online

length of cable= 50 feet

load current=6A

source voltage =12v

my intension to calculate  re

resistance per length in ohm
voltage drop
% voltage drop
% loss
select area which is good for the application

 wire resistance calculator


texts: Solder Fumes - Activated Charcoal vs Outside Venting

texts:
Like probably everyone else here I do a ton of soldering. When I setup my current workshop I built a fume extractor that actually goes in a window near my bench. Basically just a length of dryer duct with a high flow fan that vents directly outside. This is all an well, but kind of annoying to setup every time. I did this because, at the time, I felt that venting directly outside was clearly going to be better than an activated charcoal filter.

So, was I wrong? Can a simple filter be just as good as exterior venting? Or at least close enough? Has anyone ever found any hard data on how much lead and other toxins a charcoal filter will remove?
Would adding a HEPA filter in the mix help?


texts: Automated testing - disabling a GPS antenna

texts:
I am doing automated testing on a module.

This module has a SMA connection to a GPS antenna.

I need to automatically (programmatically) disable the connection to this antenna somehow.

What would be the best way to achieve disable the connection to a GPS antenna?


texts: How to deal with "Brown on" slowly increasing voltage/current from solar panel to power mcu

texts:
With a solar panel powering an Atsamd21, I have the problem that the mcu will not boot correctly and gets stuck at some point.

How can I deal with this? I thought of adding a large enough capacitor and some kind of voltage detection to enable power only when the cap reaches a certain voltage. This will restart the mcu until power is large enough, but at least it won't get stuck from slowly increasing voltage.


texts:
I have an issue here concerning Infrared and arduino, i have been disassembling various receivers and took out the IR sensor from them, but i have hard time to read any data from them.

this is my third attempt to take out a receiver from an older satellite receiver, basically what happens is nothing when i try to point any remote controll to the IR sensor, have tried various schemes but none of them is working.

would love to have some input if i do something wrong, do i need resistors or anything between the out signal and the digital input on the arduino boards or anything else?

Digital 38KHz IR Receiver, the entire IR sensor is black and seems to be encapsulated with a black molded box.

i have tried atleast 3 different arduino boards, all share the same issue on all 3 different IR sensors i tried


texts: How to represent off board parts /wiring looms in Kicad?

texts:
I'm trying to design a Kicad schematic that has some off board LEDs.  The LEDs are connected to the PCB with a set of physical flexy wires and a connector.  This is my intention:-

I also have some wiring looms to design with associated connectors to circuit boards.  The thing is, when I search for schematic images of this kinda thing, I can't find any.  I also can't see how this is the same as a hierarchical circuit as there are breaks in the wires at the connectors.  Is this not the correct way?


texts: VHDL Functions c.f. Components & synthesis

texts: In our VHDL digital designs we use multiple components and build hieracle designs. Is there any benefits in using functions \ procedures in a design that are to be synthesised over component instantiations ?


texts: Connecting KY-009 to GPIO of Raspberry Pi

texts:
We would like to connect the 3-color LED module (KY-009) to the GPIO pins of Raspberry Pi 3. We are going to use the {green, blue} LEDs only (5050 SMD LED) of the module. Because

the LEDs require high forward voltage V_f > 2.75 V ([ref1]), which is at the limits of the GPIO pins' output V_OH > 2.90 V ([ref2]);
the LEDs draw large forward current I_f reaching up to 100 mA ([ref1]), while GPIO pins can't source more than 16 mA per pin & 50 mA combined ([ref2]),

we think of using this circuit ([ref3]):

Problem is, a voltage drop of (5−V_C) V across the LED load could exceed the maximum rating of the load V_f_max = 3.40 V ([ref1]).

Could adding resistance R_x before the load help? If so, how can we calculate its value?

More generally, is this circuit appropriate to use? — we're afraid of damaging the Raspberry Pi GPIO pins & are beginners in Electronics.


texts:
Here is an object push button that needs to be hacked:

simulate this circuit – Schematic created using CircuitLab

Hacked object circuit is not accessible.

From multimeter :

button is pulled up with a 10k resistor (measured resistance between 5V power and button input)

I want to hack it with an external 3.3V MCU, tolerant to 5V on its inputs. My goal is to keep actual behavior and :

read current button status
control button from external CPU

simulate this circuit

Max sink/source current on D0 is 12mA.

on D0 - GPIO as input - button state is read
on D0 - button control done by configuring it as output with a low logic level.

Here are sink/source current :

----------------------------------------------------------------
|                         |        PB1 state
----------------------------------------------------------------
|DO Configuration  |Level |   OPEN           |   CLOSED
----------------------------------------------------------------
|     OUTPUT -     |HIGH  |   170µA          |   short circuit!
|     OUTPUT -     |LOW   |   500µA          |   0
|INPUT PULLUP-     |HIGH  | 1,7/(10k+RPullUp)|   NA
|INPUT PULLUP-     |LOW   |   NA             |   3.3/RPullUp
----------------------------------------------------------------

To prevent shortcircuit adding a resistor before D0 would be safe, but with such a resistor, on hacked object circuit input there is now a voltage divider when D0 driven low (and PB1 open).
Adding a 680ohm resistor keeps D0 far from current limitation and now when D0 driven low and PB1 is opened, hacked object circuit has a 0.31 level. When D0 is configured as input I must be sure D0 pullup resisor >> 680ohm

So is it safe to connect this circuit with only a resistor?Above, I supposed hacked object circuit impedance was fixed (high impedance input with 10k resistor pullup)...
Can you provide and detail some examples of dangerous cases?

regards


texts: How to sense wind direction - low cost, low power

texts:
I need low cost wind direction sensor.

Requirements (edited)

low power
low cost ($5 or less)
wide temperature and humidity range (it will be part of weather station)
at least 5 degrees acurracy and resolution
response time - it may be few seconds, but faster is better

Optional:

low complexity
small size

It's for solar powered weather station based on Raspberry Pi. I have 1 ADC input there and i2c exposed. I can use microcontroller between Raspberry and sensor (and more ADC channels if necessary).

I was thinking about synchro, but I'm worried about power consumption.

My best idea so far is sensor with magnet or few magnets and hall sensor.

Is this good idea? I expect wide temperature and humidity changes.
If not - anyone got better idea?


texts:
I've noticed that many circuits use 22pF capacitors. For instance, the Arduino uses them to ground the oscillator pins of its AtMega328. Many tutorials call for exactly this value for simple circuits.

Why is specifically 22 pF so common? Why not 20 or 25, which are arguably "rounder" numbers?


texts: Some Problems in a power amplifier circuit with THS3091

texts:
Recently, I designed a power amplifier circuit with THS3091.
The schematic diagram and PCB of the circuit are just the same as the layout example of the datasheet of THS3091 in page 39. But some values of the resistance are not available in my lab. So the modified circuit is this:
THS3091 schematic diagram

When I tested the circuit, there are some problems:

The frequency of the input signal is 100 kHz. I tested the output signal with the spectrum analyzer. But there are some strange frequencies, such as 0 and -100 kHz. And the value of power at -100 kHz is the same as the value at 100 kHz. What are the strange frequencies mean?
The circuit is designed with dual power supply. And the current value of the source is 14 mA, 17 mA with no input signal. If the input signal connected to the circuit, when I increase the peak voltage of the signal slowly, the current value of the source will increase within a certain range, then decrease gradually. However, at last, the current value is smaller than 14 mA, 17 mA, which is strange. I wonder why the current value changes like this.
THS3091 is a current feedback amplifier.How to calculate the gain of this kind of circuit?
When I increase the peak voltage of the signal slowly, the output signal will distort. And the harmonic will also change, for example, the second harmonic is larger than the third harmonic firstly, then the third harmonic is larger than the second harmonic. Is there any rule?


texts: Proper assignations of current directions

texts:
What is the best way to know the proper direction of current?  Lets say we have this circuit below:

The correct directions are given below:

What are your techniques to know which is the proper way?  I'm afraid that if I choose the wrong direction, then the results will be wrong.


texts: Protecting the op-amp against output short circuit current with a resistor

texts:
There is an operational amplifier LM258WYDT.

The output of the operational amplifier will produce a voltage in the range from + 12V to -12V and generate a PWM signal.

Datasheet:

  Short-circuits from the output to VCC can cause excessive heating if VCC > 15 V. The maximum output current is
  approximately 40 mA independent of the magnitude of VCC. Destructive dissipation can result from simultaneous shortcircuits on all amplifiers.

At the input of the operational amplifier is a TMR1222 isolated DC / DC converter with short circuit protection and a maximum output current of 85 mA.

The output of the operational amplifier may be accidentally shorted to ground.

It is necessary to protect the operational amplifier from short circuit so that it returns to normal mode after the short circuit is removed.

I was looking for protection options, one of them was a resistor connected in series to the output of the operational amplifier.

I have the opportunity to put a 680 ohm resistor.

Tell me, is this solution right?

Instead of a resistor, you can install a resettable fuse, but it will most likely distort the output signal.


texts:
I'm talking about laser diode for engraving/cutting cnc.
As far as I know led or laser diodes are often driven by pulse signals to enhance their performances.

Please note I'm not talking about the PWM modulation used to create a smooth range of intensity. I'm referring about the low-level driver of the diode itself.

Well, also this is a sort of PWM but with a very short pulse (typically a dozen of ns) followed by a recovery time (much longer) to allow the junction to cool down, ready for the next pulse.

What I'm asking here is the advantage in a practical application like engraving or cutting. Let's consider a real case, two different products:

Product A: 6W laser diode driven by a constant current
Product B: 15W laser diode, pulsed-driven but with a mean power of 6W

Why should I prefer the B?

Here my thoughts: if I want to cut something I need to burn long enough the surface of the material to create a hole. Then I can advance a bit and burn another hole, and so on until I have a trench. If my cutting depth is less than the stock height I need to make multiple passes.

Well, let's say the Product A create a trench of 0,3 mm depth at a given feed rate. Product B would create a deeper trench (due to the more power applied) but due to the recovery time I need to lower the feed rate. Because the mean power are identical the cutting time would be the same (i.e. half passes at half speed).

I'm pretty sure my opinion is incorrect.
Would you please help me to understand the advantages in such an application of pulse-driven laser diodes?


texts: Why/when is AC-DC-AC conversion superior to direct AC-AC conversion?

texts:
I am currently studying wind power and the power electronics used for it. In wind power a generator is driven by wind, thus the resulting power is of widely varying frequency and amplitude. The power grid, in turn, has strict requirements for the input power in terms of frequency, phaseshift and sinusoidal form. For this reason, power converters are today used routinely in wind power.

The predominant way to get the power into the grid is to use an AC-DC converter followed by a DC-DC converter and a DC-AC converter. This seems rather complicated instead of using a single direct AC-AC converter. Why is the indirect conversion via the DC "in-between" route preferable?

(This is actually a repost from Engineering, since I only found out later that there is a more active, thematically fitting, non-beta Electrical Engineering.)


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How long that cable:
https://www.aliexpress.com/item/32885352799.html
can be extended without losing image quality if I cut it in the middle and add wire?
Which wire will fit and what kind is the shielding ?
Thanks in advance


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I have been facing following problem. I have implemented a datalogger i.e.
software running on a MCU which creates periodic snapshots of a system state
(values of some quantities of the system). These snapshots are stored in a circular buffer in external flash memory. This circular buffer causes that the oldest snapshots are overwritten by the newest ones which is desired behavior. Another requirement is that the datalogger has to work correctly also in case the MCU is restarted. Due to this fact there needs to be a mechanism how to recognize where in the external flash memory the last snapshot has been stored.

I have decided to fullfill this requirement in following way. The external
flash memory is divided into sectors which consist of 512 bytes. So I collect
several snapshots into one block and I append so called header at the beginning
of this block. At beginning I have decided to use only 8 sectors of the external
flash so the header contains block number which goes through values \$1,2,\ldots 9\$. This algoritm works pretty well but only for small sizes of circular buffer. In case I have extended size of the circular buffer into several thousands of blocks (the external flash memory contains \$2^{23}\$ sectors) I have found that the time needed for founding sector for continuing in storing of the snapshots after MCU reset is unacceptably long. So I have been looking for another solution how to find sector for continuing in snapshot storage after MCU reset in quicker manner.

Does anybody have any idea? Thanks for any suggestions.


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Is it possible to use fluorescent tubes wired in series, provided that the ballast can supply a high enough voltage and power?

Problem description

F28T5 are too long (4ft) for me, so instead I plan to use pairs of F14T5 side by side, which are 2ft long. The problem is this would require more ballasts. Typically, one ballast can power one or two lamps, like so

But I would like to use the ballast like this

My theory is that 2 x F14T5 would be electrically equivalent to one F28T5, if wired in series. The ballast will provide the appropriate current, which would be almost the same. Is this correct? or would the plasma have very different characteristics with an intermediate electrode?

Starting issues?

Another potential problem is starting the lamp. My understanding is that the plasma in the tube must first be ionized, typically by heating a filament at both ends. But with lamps in series, the middle two filaments would be cold since they are not connected to the ballast.

Would this prevent the lamp from starting? or does it only need to be heated from one end? (Note that with two lamps in series, each lamp has one heated filament. But with three or more, the middle lamps will be cold. Would it also work with three or more lamps?) Would using a different type of ballast (instant start) that uses a high voltage to induce breakdown avoid this problem?