texts: I2C / TWI freezing with SDA stuck at LOW

texts:
In my project I have connected multiple sensor breakout boards to an Arduino-Pro-Mini running at 3.3V and 8Mhz as follows on a fabricated pcb

This is how the proto-pcb looks:

You will see that all the components are on one PCB, except the accelerometer which is a breakout board connected to the main pcb via a 1-feet cable

I am using GPIOs to power the individual breakout boards and pullup the SDA SCL lines, because before I'd designed the PCBs I'd thought that this would help me conserve power by allowing me to turn off the individual sensors when they were not in use by toggling the GPIO pins. After learning that toggling the GPIO pins could damage my i2c lines from a discussion here I decided to keep all the GPIOs permanently high and use the internal power down modes of all the individual breakouts for power conservation. I could've modified my designs and powered all the boards with Vcc, but as everything was working fine and because more importantly 30 of my pcbs had already arrived from the fab-house and the client was after my life for the pilot project, I decided to go ahead with it.

But after a week of installing 15 of these pcbs in an IP65 enclosure in a highly humid environment, 10 of the 15 pcbs stopped transmitting data. Upon inspection I found that there signs of moisture deposits inside all the boxes and in 4 of the pcbs, the i2c lines were blocked.

Upon analyzing the signal on an Oscilloscope it looked like the SDA and SCL line were fine at first, but as soon as the master tries to write on the line:
1) SDA goes from HIGH to LOW and freezes subsequently
2) SCL starts and then keeps going

This is how the SDA (red, channel 1) and SCL (yellow, channel 2) look at a timebase of 1us:

the actual DSO capture for this can be seen here

Where as, this is how they should look normally:

the actual DSO capture for this is no. 1 in the comments below ..

Zooming out a little bit to a timebase of 10us,
(sda-scl at 10us in a damaged pcb)

the actual DSO capture for this is no. 2 in the comments below ..

where as, (sda-scl at 10us expected in a working pcb)

the actual DSO capture for this is no. 3 in the comments below ..

6 of the 10 pcbs which had moisture deposits inside and had stopped transmitting data had no issues and seemed to be working fine when I tried to debug them. I guess that they were in a low signal area and hence were not able to register on the network because the antenna isn't very effective anyhow.

Out of the other 4 pcbs that had their i2c lines blocked, 2 of the pcbs started working normally as soon as I de-soldered the RTC breakout board and connected all the remaining breakout boards and the sda/scl pullups directly to the Vcc line instead of the GPIOs. There was no issue with RTC breakouts or the voltage on the GPIO pins.

In one of the PCBs, the SCL pin of the accelerometer seemed to be fried, as it was pulling the entire line to low. It wasn't shorted or anything but there were some white deposits on the pins of the main IC.

Would be grateful if someone could throw some light on what could be blocking the i2c - SDA line and why did the desoldering the RTC and migrating from GPIOs to Vcc solve this issue? Has the issue been solved, or is it just temporary?

Is it possible that because of the way the GPIOs have been used to power the breakout boards, the SDA/SCL pins of one of the breakout boards could have been damaged?


texts: How to translate high voltage 500 Vdc to 501 Vdc differential to low voltage 0 Vdc to 1 Vdc?

texts:
I have two high voltage nodes which I need to measure the differential voltage between. What I am thinking at the moment is the following...

1 - Use voltage dividers to probe the voltage at 1/1000, thus having a differential voltage of 0.500Vdc and 0.501Vdc.

2 - Use an operational amplifier with a gain of 1000 to obtain the original differential signal.

3 - Use the 1Vdc differential voltage with my analog to digital converter (this part is extra, the first two are where my roadblock lies.)

The problem I have with this approach however is the slight error in the resistors and other small components will affect the accuracy of the final reading. Even using resistors with 0.5% tolerance and coupled resistors (is this the proper name for them?) may not be enough.

Is there a more traditional way of obtaining the differential voltage between high voltage lines?


texts:
I have one of these devices:

To control 4 rgb leds on a pool. I googled some sites that show this exact device and it seems to work with the 433Mhz frequency (I bought a box that included the power supply, leds, etc, everything connected so I assume this is the frequency it uses since the device and remote looks exactly the same as the one I have).

My problem is that the receiver box is located inside a room made of bricks where the pool pump and filter are, next to one of the pool walls (which is made of concrete and iron rods). So the remote will only work if I get REALLY close, and that is if the batteries are new.

The antenna on this device seems to be just a small wire. I did some googling and found that there are some 433Mhz antennas that look a little better, like similar to wifi antennas, I think I even have one from an old cctv system.

My question is, if I wanted to use a better antenna (maybe extend it since I saw some 433Mhz antennas that comes with like a 3mts cable, so its placed outside the pump/filter room, or just leave it inside if the antenna is good enough to work), can I just connect it to the existing wire that is currently acting as antenna? Or should I open the device and solder the new antenna to the pcb?


texts:
I have a very good op amp (AD8551) that I use to dynamically amplify a very small signal (2x, 10x, 100x, 1000x gain).

The problem is that there is a noticeable noise level at 100x and 1000x gain, and it has a weird constant shape.

If I power the circuit with a poorly stabilized power supply and connect the input of the amplifier at GND, I get a large noise level at 1000x as seen in the picture bellow.

If I power the circuit with a better stabilized power supply, the noise is still present at 1000x with the same waveform, but lower amplitude. And no matter what power supply I use the weirdly shaped noise doesn't disappear.

Since my AD8551 has a PSSR of 130 dB, I thought that TL431 used for biasing the input may be at fault. So I left the poorly stabilized power supply for the op amp and used the better one for the TL431, but the output is the same. Stabilizing the voltage on the resistor in the cathode of TL431, doesn't change anything.

The image below is an output sampled by a microcontroller with it's internal ADC. As you can see at 1000x the output swings almost full range. The reason 100x is missing in this test is because I replaced the 1MΩ R21 with a 100KΩ resistor and 1KΩ R66 with a 100Ω one, resulting in 1.1X, 2X 10X and 1000X amplification.
I did this because I was fearing that the feedback resistor R21 might be too big to bias the op amp negative input, even though AD8551's input bias current is rated max 2nA. The change did slightly diminish the amplitude of the noise.

Does the Vcc have to be dead quiet even though the op amp's PSRR is 130 dB? Is it the input bias causing this problems?

I can't figure it out, especially since I don't have access to an oscilloscope. All I have are the readings from the microcontroller saved on a SD card.


texts:
I've read about loops that a PCB designer should avoid them "mostly about ground loops" but i think I've read also about power.

so in this case, is this wrong: ???


texts:
I am having trouble figuring out how to add voltage regulators to my circuit for SPICE simulation. The regulator is a 78L10AC voltage regulator, 10V, 5% output tolerance, LP package. I have most of my circuit figured out (I think), but am unsure as to how to write the statement for the voltage regulator.

If anyone could help me out a bit that would be great. Also looking for any recommended reference for SPICE software. (I have never used this before). We have a bunch listed that we can use, just want to see if anyone has a highly recommended, preferred document that they use as reference.

I will most likely be using LT Spice or PSpice. (any recommendations there?)


texts:
Let's say i have two 6S Lithium BMS modules (basically protection and balancing) and i want to create a 12S battery pack. Is it possible to chain the power lines of said modules?
Just curious


texts: Timed Selection Between AC Power Sources

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I would like to be able to run a freezer from AC power line A in the daytime and AC power line B at night. Right now, I am manually unplugging the freezer from power line A and plugging it into power line B (and back in the eve). I would like to have this happen via a timer.

Seems like such a simple thing, but I don't see a simple way to do it.

Do you have any advice?


texts: Is there any characteristics difference indicated by this two symbols ?

texts:
During study , I am encountered with this two Inverter symbols .
Sometimes this two symbols are usedn in same logic circuit. Though they are working as inverter, I'm guessing there must be some charecteristic differences indicated by this two symbols.Or there is no logic to use two different symbols in same circuit.

Is this symbols indicated different kind of inverters or some different physical properties  ?


texts:
Is it possible to calculate the turn-on and turn-off energy of SiC-MOSFETs with datasheet parameters? The method with ½ * U * I * tr (or tf) cannot be used here. Let us take the C2M0080120D from Cree as an example. In its datasheet, it is stated that the turn-on energy at Vds = 800 V and Id = 20 is 265µJ. With a Si-MOSFET it is relatively easy to determine the switching energy for an inductive load:

E(on) = 0.5 * tr * Vds_max * Id_max

That would be 160µJ for the C2M0080120D. Therefore, I cannot use this equation to calculate the turn-on energy.


texts: There is a missing component in this circuit and couldn't figure out why?

texts:
I'm designing a BA1404 Stereo FM transmitter and I found the following source: Source Link

You can find the component list, circuit scheme and the other stuff on this page. But when I look at the scheme, I couldn't find the 10uH Inductor on it. There are some images of the assembled circuit board and you can see the 10uH Inductor on the board.

I'm totally new at electrical circuits. Am I missing something at the scheme? By the way, are there some other sources on the internet where I saw the same circuit and similar assembled boards?


texts:
Let us take a capacitor charged by a source voltage of 12 V d.c. supply. Having fully charged, the capacitor is now connected with a source voltage of 5 V d.c. supply.
What will happen to the potential differences(if any other thing happens can mention) of both the capacitor and d.c. supply?
Note:- No other resistor is their in the circuit, the resistance of connecting wires is negligible. There are only two components capacitor(charged to 12 V) and the other d.c. source power supply(5 V) connected in series.


texts: Power supply buzzing, LED strip insulation has almost turned black

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I was changing some light bulbs at my mom's house and I noticed that a (water resistant) LED strip she has had turned stiff and almost black. As expected, it hardly gave out any light. The LEDs seem to be working so I think the reason it's hardly giving out any light is the decoloration of the insulation which was once transparent.

I also noticed its power supply (230V -> 12V, 5A) was buzzing and was quite hot to the touch. The strip is about 2m with LEDs every 5cm, so approximately 40 LEDs. Although I don't have a datasheet (since it was installed many years ago by someone else), if we assume each LED to be drawing 50mA, it adds up to 2A - way bellow the 5A of the power supply. Even if they use up 100mA, which does seem a bit much, it would still add up to 4A which should still be fine for the power supply but might explain the heat.

Could the LED strip turn black because of normal use/heat or should I have a better look at the power supply? I didn't notice any obviously busted electrolytic caps with a quick inspection (the top is full of venting holes so I could look inside) but there could be ones where I couldn't look without disassembling it.

I did notice a trimmer on it but I didn't have a multimeter with me to test the output voltage so I have a suspicion the output is somewhat larger than 12V but not enough to blow the strip instantly.

Last bit of information that I found odd but it could be nothing, the electrician had used a 5 core piece of cable, using 3 of them (blue, brown, green/yellow) to connect the power supply to mains and the remaining 2 (blue and brown) to go back and connect to the LED strip. So you have 230V and 12V running through the same cable. Could this have anything to do with it?

I will go back with my multimeter so I can find out myself if the power supply is not set correctly or acting up.


texts: Is it possible to use a single ADC single S&H MCU for active power measurement?

texts:
I have a MCU equipped with a single ADC and a single S&H (Sample and Hold) circuit. The board where the MCU is placed has several inputs (let's say 3 x currents, 3 x voltages). The MCU is programmed to sample each input at 1 kS/s. Since it has a single ADC, the ADC sampling frequency is at least 6 kS/s (due to the fact we have 6 inputs), and the ADC input is multiplexed on the various input signals sequentially.

I wish to calculate active power (single-phase and/or three-phases), but unfortunately the ADC has a single S/H, and hence the sample of the voltage and the sample of the current are not taken at the same time.
The best solution would be to use an MCU with several ADCs sampling simultaneously, or an MCU with one ADC but several S&H circuits.
Nevertheless is there some way to calculate active power accurately (multiplying the instantaneous voltage and current samples) with single ADC and single S&H, for instance through linear interpolation (to align the current and voltage samples to the same instant)?


texts: High voltage distribution line fault current

texts:
On a conventional 7,200 volt distribution line, what would be the average fault current in a scenario like the one shown in the video below?

Video

Specifically, I'm wondering what the power dissipation is at the fault and why it does not trip an inline fuse farther up the line. Is the line resistance itself limiting the fault current? (What would the resistance of this fault be anyway? Approaching zero ohms? 1 ohm? Thousands?) Does this fault current have any significant effect on the overall load for the area or is it "negligible"? The only reason I ask is that it does not seem to heat the rest of the line significantly or trip the circuit protection upstream.


texts:
Lets say for example, that I had a box full of transistors, resistors, capacitors, diodes, leds, this and that, and left it in a cool, average environment for lets say... 50 years.

Do these components have a lifespan while been unused? Do the insides end up degrading and become unusable like cars? Or do they just... Sit there?

I'm asking this, because I just got a thought that struck me, being that if you kept today's components, (and kept them for 50 years) will you be able to use them in the future?


texts: Where to put main code in Mplab Harmony Framework?

texts:
When i'm doing code using MCC for example i will put my code the following way:

#include "stdio.h"
#include <xc.h>
#include "mcc_generated_files/mcc.h"

void main(void)
{
    SYSTEM_Initialize();
    printf("Booting loop debugger\r\n");
    LED_GREEN_Toggle();
    loop_debug_initialize();// start debug variables
    loop_initialize();
    while (1)
    {
        loop_debug_manage();
    }
}

My question now is using the Harmony framework i have something like this:

int main ( void )
{
    __XC_UART = 1;  // Code is configured to use UART1
    /* Initialize all MPLAB Harmony modules, including application(s). */
    SYS_Initialize ( NULL );

    while ( true )
    {
        /* Maintain state machines of all polled MPLAB Harmony modules. */
        SYS_Tasks ( );
    }

    /* Execution should not come here during normal operation */

    return ( EXIT_FAILURE );
}

Where shall i put the same code? can i put everything on main? like this:

int main ( void )
{
    __XC_UART = 1;  // Code is configured to use UART1
    /* Initialize all MPLAB Harmony modules, including application(s). */
    SYS_Initialize ( NULL );
    loop_debug_initialize();// start debug variables
    loop_initialize();

    while ( true )
    {
        /* Maintain state machines of all polled MPLAB Harmony modules. */
        SYS_Tasks ( );
        loop_debug_manage();
    }

    /* Execution should not come here during normal operation */

    return ( EXIT_FAILURE );
}

Or this is not ok?
Does it need to go inside void SYS_Tasks ( void )?

It's my first time working with Harmony, so any help is appreciated.


texts:
I am designing a PCB for reading analog signal by the AD7732. I searched a lot to find tips which increase the precision and effective bit resolution. One of these tips is to segregate analog power supply and the Digital one due to switching noise of digital components. I want to Know:

How to design a suitable powering circuits for an ADC. In AD7732 datasheet I did't see any new and different point exclusive for an ADC. It is worth collecting some tips around.
Should I connect analog ground to digital ground? In some datasheets I read they should be connected. If this is true why do we segregate analog and digital power supplies? Doesn't this connection pass noise from one side to other side?
Is two switching power supplies proper to use as analog and digital power supplies?


texts: What is name of this oscillator and how does it work?

texts: I could not find any information on how it works. I created it on bread board and it outputs a pretty nice sine wave. Could you please tell me how it works or at least name of the circuit, for example, like the Hartley Oscillator?


texts: LM565/NE565 Spice modeling in Orcad PsPice/Proteus/Multisim

texts:
"Q: Display the outputs specified in the following figures in the simulation software and the results. That's it."
I have trouble getting the answer from this circuit.
When I realized that this chip was not in the software, I guessed to myself that this chip may have been modeled by someone and it is on the Internet. None of these three programs has this part, but I was able to find a PDF that the PSpice simulation model has this piece for Orcad software but I do not know how to give it to the software.
So far I have only edited the models, but I do not know how to make a new model.

These are the questions that the college teacher asked us, and he only wants the answer to this circuit.I know that a chip like 4046 is better for that, and maybe if it were not for the coronavirus, I could have built this circuit in the lab and saved myself from this.


texts:
I have the following circuit:

where Vin is waveform with the frequency of 1kHz and amplitude 10V. The diodes are ideal. I need to find the average value of Vout.

I found that when Vin > 0 then D1 is off, and D2 is on, so Vout = I1R1 = 1V.
And when Vin < 0 then D1 is on and D2 is off, so Vout = 1 + Vin. Is this correct?

Now I think I need to use

I tried taking b = 1/f and a = 0 and writing the integral in two parts, one going from 0 to 1/(2f) and second from 1/(2f) to 1/f with. I used the Vout functions I got above in them, respectively, but I get a bad result. How do I do this correctly?


texts: Proper supply wiring for CNC router 4.1 kW 3Φ motor and 120 V accessories?

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I'm building a CNC router table that has a three-phase 220 V spindle motor, and 120 V computer (and accessories). The spindle's nameplate:

As you can see it tops out at 20.3 A @ 220 V.

The VFD’s (Delta Electronics VFD25AM23ANSHA) nameplate says it’s rated for 5.5 kW, 25 A output, 30.0 A @ 200 - 240 V input.

I have three-phase 208 V power. I would like to have a single plug and power cord for the spindle motor and related 120 V accessories (PC, monitor, drive electronics, solenoid valves, etc). The total of these accessory loads is probably less than 500 W.

Can I use 10/5 SJOOW power cord (not sure I can get that, but I know I can get SOOW 10/5 cord), and a 5-conductor locking plug to provide the three phases, neutral, and ground?

The NFPA 2017 NEC Handbook tables 400.5(A)(1) and 400.5(A)(3) seem so suggest I'm limited to 20 A with 10/5 cable.

400.4 also says:

  A neutral conductor that carries only the unbalanced current from other conductors of the same circuit shall not be required to meet the requirements of a current-carrying conductor.

That could allow me to consider my cord as having three conductors, and thus not needing derating to 20 A. But it also refers me to b.310.15(b)(2)(11) for derating for load diversity.

What's my best bet here?


texts: Measurement of power dissipation in a resistance

texts:
In the above figure (step up transformer), We can calculate \$V_s\$ using \$\frac{V_s}{V_p}=\frac{N_s}{N_p}\$ and \$V_s=50 V\$

So, power dissipated in the resistance, \$P=\frac{V_s^2}{R}=2500 W\$ (which is clearly impossible as I delivered only \$P=V_pI_p=5W\$ from principal coil.)

Again,if I calculate power dissipated in \$R\$ using \$I_s(=0.1 A\$ using \$\frac{I_s}{I_p}=\frac{N_p}{N_s}\$) , \$P=I_s^2R=0.01W.\$

Powers calculated in both ways are supposed to be same, aren't they??

I think, my main problem is I can't find out the current passing through \$R\$ as \$\frac{I_s}{I_p}=\frac{N_p}{N_s}\$ gives \$0.1 A\$ whereas \$i=\frac{V_s}{R}\$(Ohm's law) gives \$50A\$.

What am I missing here?Any help would be highly appreciated.


texts: Altium 17 somehow lost shortcuts, I cannot rotate a part with the spacebar

texts:
In both the schematic and PCB I can no longer rotate a part 90 degrees by hitting the space bar.  I have tried lots of things, but getting to the context-sensitive help with ctrl-F1 also does not work.

I tried assigning 'space' the primary shortcut in edit command-> rotate selection,
but then it always prompts me for an angle.

I also know I should be able to select a part (which works) and then hit F1 or Control-F1 to bring up a context sensitive menu so I can change things like the shortcuts, but that key is also not assigned correctly so I cant get to the menu to change the shortcuts.

Help!?


texts:
My fridge stopped cooling and kept hearing a click noise every 2-4 minutes. Researching led me to understand the start relay is nothing more than a PTC resistor that cuts the start winding once compressor kicks on.

Seemed simple enough so I open mine and it's more complex with a circuit board AND a PTC overload separate.

Now the circuit board has a triac but what's puzzling is only Line and Neutral 115v are fed into the whole assembly. There isn't a control line going from mainboard of the fridge to the gate of the triac.

So I'm puzzled to its operation. Does anyone know what the circuit board is for?


texts: Using MCP73213 for charging two Lithium ion batteries connected in series

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My device has some loads which use 5V. I can't use a single Li-ion Battery as it'll give only 3.7V. So I've decided to connect the batteries in series to get 7.4V power supply. Since my wall adapter gives 12V output, I'm planning to use MCP73213 to charge the batteries. The batteries I've bought are actually cell phone batteries.

Now I've the following questions:

Is it a good idea to use this cellphone batteries in series? Is there any possibility that this series connection will affect the battery life?
Is MCP73213 a good choice, as it doesn't have any balance charging mechanism?


texts:
This is my first attempt in designing a pcb layout for a gps chip antenna. PCB is two layered. All the components (including the antenna) are on the bottom layer. I have assumed it to be a "co-planar wave" transmission line (NetANT_2). The width of the feed line is calculated using the "Saturn PCB design toolkit".

My concern is, can this transmission line be considered as "co-planar wave"? as  I think there is no sufficient ground plane to left of the feed line. Really appreciate the help. Thanks.

EDIT: The length of the feed line (NetANT_2) =138mils (3.505mm), width= 33.325mils (0.84mm). The ground plane gap is 8mils(0.203mm). substrate height 0.66mm. U10 is a LNA(MAX2659).


texts:
I'm doing some electrode recordings and a large noise waveform keeps appearing on the oscilloscope (see pic attached). Interestingly the recording set-up functions just fine with a clearly distinguishable signal for about 3.5 minutes after powering on before a large amount of high frequency and high amplitude noise kicks in which quickly giving way to the waveform in question that persists until the power is cut off. If the system is powered back on less than 3.5 minutes after the waveform occurred, it comes back in less than 3.5 minutes; if the system is off for longer than 3.5 minutes it takes about 3.5 minutes to show up again. The power supply rails are +-15V and I'm in the US so wall power is 120V 60Hz. There is an amplification stage and a multiplexer before the oscilloscope input. The electrodes have an on board pre-amp stage and there is 10 feet of unshielded power (5V) and data cables bundled together going to the electrodes.

Has anyone ever seen something like this? The frequency of the waveform makes me think it has something to do with the wall power or that it could be a ground loop but the large time constant is a bit confusing.


texts: Flame sensing using Flame Rod and Short circuit identifying

texts:
I am sensing a flame using a flame rod. I am using 12V AC at the input and at the output flame sensing circuit which is made of opamp, some resistors and capacitors, I get 1.6-2.4V when there is a flame, and 3.8-4V when there is a short circuit, and 5V when there is no flame. My flame sensing circuit seems to work fine but when there is a flame and short circuit happens at the same time my circuit only detects short and gives output of 3.8-4V. But I want my circuit to give output of 1.6-2.4V and see a flame instead of a short when both occur together. Is there any way I can achieve this?
I would really appreciate your opinions on this.

Thank you

I am using this circuit below.


texts:
I'm designing a simple remote-controlled sensor.
It's going to be connected with others and a master device using RS485.
All it's going to be doing is transmitting the status of a few digital lines and controlling a few relays and LEDs.

I've used MSP430's for some other projects, so decided to use the cheapest MSP430 with a hardware UART I could find.
This turned out to be the MSP430G2203.

After reading the MSP430x2xx user guide I realized that for clocking the UART I have 2 options: the DCO and the low frequency oscillator.
From the datasheet of the MSP430G2203 I got that even the calibrated DCO frequency is -6% ... +6% in the entire temperature range. To me this doesn't seem to be a good-enough clock source for a UART.
From the datasheet I also got that the low frequency oscillator is designed to work with 32768Hz crystals.

So, I have the following questions:

1) Has anyone tried clocking the MSP430 UART from the DCO? Were there any problems? Or should I use autobaud to compensate the clock frequency drift?

2) Has anyone tried clocking the UART from the low frequency oscillator?
What crystal frequencies does the low-frequency oscillator actually support, maybe there are more UART-friendly frequencies available?


texts: Pole placement to create a full-state feedback controller?

texts:
I am learning about control theory by going through Oagata's Modern Control Engineering.

As part of a practice exercise I am trying to design a full-state feedback controller that satisfies my design requirements using the pole placement technique.

MathWorks provides high quality documentation about pole placement.

Design Requirements:

Less than 5% overshoot
Less than 2s settling time
Steady State Error Minimised

My 4th order system:

                 - 0.00198 s + 2
  ----------------------------------------------
   s^4 + 0.1201 s^3 + 12.22 s^2 + 0.4201 s + 2

Step Response:

What I have done so far:

I first started by understanding the pole placement technique. Since closed-loop pole locations have a direct impact on overshoot, settling time and steady state error, these can be adjusted accordingly to get the desired response. Pole placement may be done using state-space techniques, and thus require a state space model of the system. Therefore:

NUM4 = [-0.00198 2];
DEN4 = [1 0.1201 12.22 0.4201 2];
sys = tf(NUM4,DEN4)
[A, B, C, D] = tf2ss(NUM4,DEN4)

A = -0.1201  -12.2200   -0.4201   -2.0000
     1.0000        0         0         0
         0    1.0000         0         0
         0         0    1.0000         0

B = [1; 0; 0; 0]

C = [0 0 -0.0020 2.0000]

D = 0

Next, the closed-loop poles are the eigenvalues of A-BK, where K can be computed using the place function.

K = place(A,B,p); where p contains the desired locations of the closed loop poles. I proceeded with:

p = [-0.424+1i*1.263, -0.424-1i*1.263, -0.626+1i*0.4141,
-0.626-1i*0.4141];
K = place(A,B,p)

And the result I got was:

K =

1.9799   -8.8200    2.2799   -1.0001

This means that I have to poles on the right hand side of the plane, resulting in an unstable system. Since I need to design a full-state feedback controller that satisfies the design requirements, this is clearly wrong.


texts: Eagle software: Different grounds in the same circuit

texts:
I'm designing an Arduino shield to manage the control signal that reaches 4 CCFL inverters.

As part of the circuit design, I've decided to use optocouplers to isolate the Arduino's microcontroller from the rest of the circuit. If I'm right, in order to get the proper galvanic isolation I need to separate on one hand the Arduino's GND and on the other hand the power supply's AGND which feeds the part of the circuit (through 7806) aimed to generate that specific control signal.

Am using Eagle CAD software and I've used different GND symbols to separate the different grounds coexisting in my circuit, but when switching to PCB design all of them seem to be together joined in the same net.

These situation makes me wonder several questions:

• Am I right when I'm trying to separate grounds in order to get galvanic isolation?.

• I've found this post that seems to talk about a similar question: How do I facilitate keeping multiple grounds, (i.e. AGND, DGND, etc...) separated in the layout when using Eagle? but I'm not sure if the solution proposed really fixes my problem, because if I understood correctly they end up joining GNDs in one point to have a global ground reference.

• If I am right, which is the best way to manage different GNDs in the same circuit in Eagle schematic design?

Here it is the schematic I'm working on:

Thanks for your help!


texts: How to mass-produce a electronic system assembled by me?

texts:
"Practically speaking", given I developed a electronic system (in my case with the Arduino board), what are next steps to make in order to produce and market that system (in my case, regardless of licenses since those seems to be OK for my Arduino project)? For example, who should I contact to mass-produce a electronic system? What type of relationships should I start? What look for and what to care?

Note: I ask that since my previous question.


texts:
simulation in a multisem  and steps truth table and k-map and circuit diagram of 044
design a logic circuit odd/even driver to check if a number 044 is odd or even


texts:
Does a fault in ground of three-phase do more damage to home appliance than a fault in ground of single phase? and why?

In a home with three phase input and single phase loads, fault in the ground damages all connected appliances (circuit breaker didn't move!). While in home with single phase input and single phase loads, a fault in ground was protected by the home circuit breaker.


texts: Toggle 555 timer IC both with switch and arduino

texts:
I want to use 555 timer IC (NE55P) as a latching toggle switch. I successfully did it using a switch as described in this toggle 555
schematics

except, I am using 5V power with led as output indicator.
more or less is like this:

my goal is to make the 555 timer accepts both an arduino (5v) out signal and a momentary switch to be able to toggle the 555 output independently. it's like having two momentary switch, one came from arduino, and one came from a push-button.

I've tried using 2N2222A transistor as switch replacement or directly use 10k resistor from the arduino output to pin 2 of the 555 timer but it wont toggle properly, it's just flashing and turned off again.

How to do it?

Update:

The main reason I want to control ne555p trigger pin using both an arduino and a button is because:

I am building an iot control and monitoring. I will need the button to send information if it is pressed (or toggled).
In that case, Ineed to place the arduino microcontroller near a gateway(internet) which also covering many control spots, one of them is a button and the 555circuit near a convenient location for let say, switching lights.
Also I need to make both independent. In case the arduino is down, 555 still can be functional for turning off a light with a relay.
I choose 555 over directly using arduino's gpio is because it's compact, small and independent, so it can be inserted to a small button box. Moreover, 555 can do toggle, which is important for 2 parallel input to be independent. Just need around 100ms high pulse to toggle the state.
3 cables from arduino is enough. Common ground and 5v out pin. And 1 for monitoring status.
NE555P is cheap and just do the job.

Several discussion are not giving answers, tend to go towards personal opinion. It's best if you give the answer first then you can add the opinion afterwards. That way is much more appreciated.

extra question:
also how to make it accept 3.3v trigger?


texts:
In datasheet for MOSFET driver ZXGD3003E6TA is following typical application circuit:

What should be the value of circled resistor? I did not find any reference in documentation.

Datasheet link: http://www.mouser.com/ds/2/115/ZXGD3003E6-77316.pdf


texts: Eagle insists on marking up spaces which are larger than the minimum specified in the DRC rule

texts:
This is what my clearance rule looks like:

My grid distance looks like this:

And the final result, after DRC, looks like this:

As you can see, although not by a very large margin, the distance is clearly larger than 0.15, specified in my DRC rule set. This is not the best example, as I just clicked the error list randomly and this showed up.

What did I do wrong? How do I tackle this?

Thank you for your help!
Edit: this might be the problem:

These are all "stock" packages from the lbr came with eagle, anything I can do or I just have to click through everything?


texts: Why is my multimeter stopping device from booting when measuring current?

texts:
I am using a BK Precision 2709B multimeter and attempting to measure the current of a device that runs off of a ~3.7V battery. The device boots up, initializes and then goes into its lower power state.
If I use the 10A setting, my device boots up just fine but I need to measure uA or mA.
When I attempt to use the mA setting, the device attempts to boot and then continuously reboots. Its not able to finish its initialization process before it cuts off. The current reading on the meter is ~30mA before the device cuts off and attempts to boot up again. The meter says 400mA max, so it doesn't seem like it is over the maximum allowed current for the mA setting.
Is there anything I can do to get past the initialization so I can measure the lower power state?


texts: Connecting the Beaglebone Black to the KK Mini flight controller

texts:
The flight controller needs to be sent 4 PWM signals at greater than or equal to 5 volts. Since the Beaglebone Black(BBB) GPIOs can supply only 3.3V I needed to change the signal from a 3.3 volt one to a 5 volt one. In order to do this I looked up online and mostly everywhere I have found this circuit for logic converter from 3.3V to 5V.

But when I connected the low side to my Beaglebone GPIO's and the other side to the flight controller and then switch on the BBB it doesn't boot up. I have already fried one BBB. When i measure the low side without connecting to the BBB I find that the voltage is around 2 volts. I think this is the problem because in multiple places in the BBB System Reference Manual it is given that no voltage should be applied to any of the input pins before the BBB properly boots up. Could this be the problem?

If so then how can i go about rectifying it? For the time being I am using optocouplers to isolate the BBB from the high side.

So, to sum it all I want to know :

How do you make sure that no voltage comes back into the BBB when its an output pin?
And since no voltage can be applied to the BBB before the system boots how can i disable devices that are connected to the BBB and going to send in data to the BBB not send any signals till the BBB boots up?

This will be really helpful for my project as I cannot manually disconnect/connect wires every single time the BBB is starting up.

Thanks,
Roy


texts: What happens if we use non-blocking assignment <= inside of always @* block?

texts:
In verilog, we are supposed to use blocking assignment = in conjunction with always@( * ) to build combinational logic, but what happens if we use non-blocking assignment <= inside of always @* block? For example,
always @ ( * ) begin
   x <= a & b;
   y <= x | c;
end

What is the behavior of this code and what kind of circuit we will end up getting?
According to the example in this slide, we will have y = 1 instead of 0 in the end, because the non blocking assignment uses the old value of x, which is 1, to update y.
But according to my experiment, I still get the desired result of y, which is 0. My guess is that, the difference of blocking and non blocking is very subtle when they are used inside of always @* block. The always @* will be triggered again at the line of x<= a & b, so that the next line sees the updated x value.


texts:
I want to put 3 leds as night light to some power outlets around the house. I also want to keep them discrete so the power adapter (110v to 5v) has to be small.

I don't want to use a simple resistor voltage divider (don't not think it is safe). But even smallest transformer is not small enough to put into space around outlet.

How can I get 5v dc from 110v safely with smallest possible way?


texts: How to amplify a 25khz square wave that goes from -3.3v to +3.3v so that the amplitude is doubled

texts:
I have a 3.3v power supply (lithium ion battery) and am using a TI MPS430G2553 chip to generate a 25khz square wave using 2 PWM pins and a push-pull setup.  This square wave goes from -3.3v to +3.3v.  I need it to produce at least double that voltage (-6.6v to +6.6v) without messing up the 25khz square wave.  I will be programatically changing the frequency of this wave from time to time, but will keep it within 1khz of 25khz.

The above circuit is driving a 25khz Piezo Transducer which has a capacitance of 2500pf.  The current setup is producing about 80dB.  I need 115dB.  The datasheet on the Piezo says that at 10v (I'm assuming peak to peak), it will produce 115dB.  So if I could double the voltage of the above circuit while maintaining the square wave, I believe I could accomplish my goal.

I have no additional power supply and would like to accomplish this with as few components as possible, for as low cost as possible.

Any recommendations with a circuit example would be GREATLY appreciated.


texts: Time Domain and Frequency Domain Amplitudes

texts:
I was wondering about these two graphs, the first is taken from an Oscilloscope and the second is taken from a Spectrum Analyzer.

Why is the amplitude in the frequency domain close to 1/3 of that in the time domain? The Fourier transform of a sine wave is: . Shouldn't the amplitude in the frequency domain be 1/2 of that in the time domain?


texts: would using the reference voltage of an ADC as a VOLTAGE SOURCE affect my ADC or the stability of the circuit?

texts:
I am using an Arduino to capture an AC signal. However, the application is sensitive and needs a high resolution, I decided to use the internal 1.1 Volt as a voltage reference for the ADC.

In the case of using 5 volt as a voltage reference for the ADC :

The AC signal contains negative voltages which the Arduino can't capture ( the Arduino is capable of measuring 0-5 volts) so I used two resistors connected to the 5 volt from Arduino and then the ground of my signal is to be connected to the 2.5 volt.

(the upper left part of the picture).

And that worked fine

my question is, if I want to use the 1.1 Volt as a voltage source which is to be connected to the two resistors to provide .55V (1.1V /2) as a middle point for my AC instead of 2.5 volt, would connecting the VRef pin to the Resistors affect the ADC? will it make it unstable ?


texts: I need help regarding voltage induced in load (cables). Say we have a 10 V/m radio field at 250MHz carrier. It induces 1V to an impedance of 50 Ohm (x length). If the cable impedance is increased to 5KOhm then how to calculate the induced voltage (please omit losses, coupling-factor etc). Is the relation logarithmic? Can someone provide me the formula or some thumb rule?


texts: Wheatstone Bridge imbalance voltage calculation

texts:
So I have this simple force measure circuit which consists of a strain gauge SG1 and the amplifier with the Wheatstone bridge, the variable resistor RV1 is set to 200Ohms.  If the strain gauge is fully deflected the circuit gives an output of 50mV. How would I go about to calculate the imbalance voltage at the bridge.
What I did so far is I found the voltage that goes into the op-amp's pin3: $$R_{FSR}=\dfrac{1}{\dfrac{1}{1320}+\dfrac{1}{1320}}=660Ohms$$ $$V=\dfrac{680}{680+660}*9=4.57V$$ Any help will be appreciated.


texts:
I wanted to run two devices off a USB battery pack: one fan that runs at 5 V 0.35 A and one device that has the ability to take in 5 volt 6 A (just a general example, basically the other device can take in a large current amounts).

This USB battery pack has one output, and I wanted to attach a Y splitter cable to run both of these devices off of this one USB battery pack, and was wondering how will the power be shared between these two devices?

Will 0.35 A 5 V go to the fan, and the rest of the ~2 A go to the "other high current device? Or will the USB battery pack just not output 2.4 A and split the power in some different arrangement?


texts: stm32f1xx how to use DMA to write to TIMx CCR

texts:
I am trying to control WS2812b digital LEDs with stm32f103. I have a buffer of color values for the LED strip and to transfer them I need to write the next value to the timer's CCR every time the timer updates. As the result I should see this buffer as a PWM signal on the pin of the MC. The guy, who helped me with the PCB wired LED's data pin to PB5 of the MC. PB5 is connected to TIM3_CH2. According to the manual there is no DMA request for TIM3_CH2.

Does this mean it is impossible to use DMA to change TIM3 CCR2 every time the timer updates? I know about the DMA burst mode which can write to any CCR of a timer, but looks like it is impossible to send a big buffer to one CCR. What am I missing?


texts: How would I create this kind of circuit?

texts:
I'm just starting out with electronics, this should explain why my "schematic" is so readable.
I'll attach it and explain further.

I know how to create a simple circuit with the main slide switch and either of the LEDs, but I honestly have no idea on how would I create 3 parts that are powered by one source but aren't connected "in one line" (Is that called a linear circuit?).

My second problem, that I have not illustrated in my schematic, is - how, if it's possible at all, could I create the potentiometer control the 7 segment displays so they display random numbers (or just light up random parts of the screen, really).
The display should change only when potentiometer is turned.

I hope that I make some sense and you can give me some tips on where to start.
Thanks!


texts:
I would like to use some high-level libraries written in C++ for my EFM32 microcontroller. Unfortunately the Simplicity Studio IDE for the EFM32 does not seem to support C++.

I am a bit confused about whether it is still possible to develop in C++ for this microcontroller family. I am thinking that I could use the GNU ARM Embedded Toolchain to do this with a custom Makefile but I am not sure it could work and what are the arguments that should be given to the different GNU tools to compile and link for a given microcontroller (gcc, ld, g++, ...)

So first is it possible?
If yes, what are the high-level steps that must be done? I really would like to understand what is happening at compilation and linking time so do you have any resources on learning how to tweak a Makefile using the GNU Toolchain to compile for a given microcontroller?


texts: Replace thermostat with rasberry pi and Solid state relay

texts:
I want to replace my thermostat with raspberry pi board. I have already connected solid state relay to rasberry pi and it works just fine. The only part left to do is to connect solid state relay to the thermostat. I have an idea how to do that but before actually connecting anything I want to ask your advice if I am doing it right.
My solid state relay looks like this

(source: asia.ru)

And the diagram on the thermostat looks like this

I have 4 cables
Blue - N
Red - L
Call - yellow
and ground yellow/red

So I think I should connect Red(L - Red) to SSR contact 1(ac in) and CALL (yellow) to the SSR contact 2 (Load). Is that the right way to do ?

P.S. Its in UK so voltage is 220V therefore I want to be extremely careful


texts: How to feed custom RGB Led keyboard backlight

texts:
I have found a lot of topics but none of them describe what I want to use it for. Basically I want to put 104 RGB Leds under my laptop's keyboard and be able to control them individually. The following list is my shopping list:

104 RGB Leds with common cathode @ 20mA each = ~2.1A total
7 LED drivers (TLC5940)
3 voltage regulators (IRF9520)
3 resistors @ 4.7K

Now I want to control each LED individually and I will create a proof of concept with an Arduino but my questions are as follows:

Is the laptop's keyboard cable capable of delivering ~2.1A?
How can I supply a clock to the LED drivers (straight from laptop motherboard)?
Would it be possible to control the LED drivers with a Windows driver or would I need a separate controller like an Arduino?


texts: Parallel power traces with PWM and unwanted EMI

texts:
I'm in the process of designing a PCB for an RGB LED light source that will allow me to dim each color channel separately using PWM. To help manage the thermal output of the LEDs I'm trying to use an aluminum PCB substrate, and to try to keep costs in line I want to design a 1 layer board for the LEDs. The power, drivers and PWM generator will be on a separate board.

My concern is that the routing necessary to get everything on one layer involves a lot of parallel traces carrying PWM signals, and I'm worried I might end up generating some unwanted EMI. Each string of LEDs is going to be driven at a constant 200mA at a voltage which will vary from about 16V to 24V depending on the color. I'm shooting for a PWM frequency of 30-50khz.

The attached image is a schematic of my proposed routing. Will this cause EMI problems?


texts: Downconvert high voltage to match dry contact rating

texts:
I have a few dry contacts on a device where the ratings are MAX 30V, 300mA.
I want to connect LED indicators (24V, 20mA) to these dry contacts and was thinking to setup an external 24V power supply to feed the LED indicators when dry contacts close.

However, there seem to be a reason for me to use 230V power supply, so I was wondering if it works using same LED indicators (24V, 20mA) and a resistor of 10kOhm in series?

$$U = U_1 + U_2 => U_2 = 230 - 24 = 206V $$
$$I = 20mA => R = U_2/I = 206V / 20mA = 10kOhm$$

I just get confused given the rating of dry contacts are given in volts... How should I know what voltage there is across the dry contact?
(Consider all components and supplies being AC.)


texts: Calculation for the distance between maximum swings in the drift distance of electrons

texts:
I am currently studying the textbook Practical Electronics for Inventors, Fourth Edition, by Scherz and Monk. In section 2.4.1 Applying a Voltage, the authors have written the following:

In the case of alternating current, the field reverses directions in a sinusoidal fashion, causing the drift velocity component of electrons to swish back and forth. If the alternating current has a frequency of 60 Hz, the velocity component would be vibrating back and forth 60 times a second. If our maximum drift velocity during an ac cycle is 0.002 mm/s, we could roughly determine that the distance between maximum swings in the drift distance would be about 0.00045 mm. Of course, this doesn’t mean that electrons are fixed in an oscillatory position. It means only that the drift displacement component of electrons is — if there is such a notion. Recall that an electron’s overall motion is quite random and its actual displacement quite large, due to the thermal effects.

I'm wondering how the authors concluded that the distance between maximum swings in the drift distance would be about 0.00045 mm? What is the calculation that was done here?
I would appreciate it if someone would please take the time to clarify this.


texts: How to get fundamental frequency of a signal using autocorrelation?

texts:
I am trying to get the fundamental frequency of a signal that only has a single pitch. I coded out the autocorrelation function using FFT and already got the autocorrelation result. Unfortunately, I don't know how to get the fundamental frequency from the autocorrelation result. Can someone help me? My code is below:

public double getPitch(double[] buffer, int firstSample, int lastSample, double sampleRate)
{
    int lengthOfFFTWindow=lastSample-firstSample;
    double[] input_buffer=new double[lengthOfFFTWindow];
    DoubleFFT_1D fft = new DoubleFFT_1D(lengthOfFFTWindow);
    double[] autocorrelation_values=new double[lengthOfFFTWindow];
    double[] fftData = new double[lengthOfFFTWindow * 2];
    double max=-1;
    double max_i=-1;
    //FFT on each sample in each window
    for (int i = 0; i < lengthOfFFTWindow; i++) {
        // copying audio data to the fft data buffer, imaginary part is 0
        fftData[2 * i] = buffer[i+firstSample];
        fftData[2 * i + 1] = 0;
    }
    fft.complexForward(fftData);
    for (int i = 0,j=0; i < fftData.length; i += 2,j++) {
        // complex numbers -> vectors, so we compute the length of the vector, which is sqrt(realpart^2+imaginarypart^2)
        autocorrelation_values[j] = Math.sqrt((fftData[i] * fftData[i]) + (fftData[i + 1] * fftData[i + 1]));
    }
    fft.complexInverse(fftData, false);
    for(int i=0;i<fftData.length;i++)
    {
        if(max<fftData[i])
        {
            max=fftData[i];
            max_i=i;
        }
    }
    return (max_i * 44100 )/ lengthOfFFTWindow;
}

Is it correct to return the maximum autocorrelation value divide by 2 as the fundamental frequency? I keep getting wrong answers when I do that.

EDIT:
An example of the single pitch test file: http://dl.dropbox.com/u/24274475/testfile_A4.wav


texts: Design of a boost converter with large variation in output current and low output ripple

texts:
I'm working on the design of a 24V to 30V boost converter that needs to have an output ripple of less than 100 mV with an output current between 0 and 2 A.
The output is used to power a controller for a voice coil actuator. Unfortunately the controller only has a single power input and cannot be changed or modified. This means that the actuator drive current and analog sensor electronics are powered from the same supply. The boost converter needs to have a low output ripple to ensure the position sensors have low noise, and support a large variation in output current depending if the actuator is accelerating (2 A max.) or when it's just holding position (10-20 of mA).
I have preliminary selected the TPS55340 boost converter with integrated switch to use in my design. Using TI's WEBENCH and back-of-the-envelope calculations I selected a L = 12 uH inductor and using a switching frequency of 750 kHz. Pulse-skipping starts below 17 mA. It should be possible to avoid pulse-skipping by adding a minimal load.
The DCM-CCM boundary occurs at Iout_crit = 224 mA. I don't see an easy way to lower the DCM-CCM boundary, so I think I need to make it such that it operates well in both modes.
I am unsure on how to approach such a design making sure it will meet the max. ripple specification in all operating conditions. It would help me if someone could point me to a relevant application note or other source.
Thanks
EDITS:

Change typo in part no.
Added more design details


texts:
I am looking at the following PCB (single layer).

The checked red/blue is GND.

Can this polygon give EMI problems in the sense that it acts as an antenna because it does not form a closed loop ?
Should polygons be closed loop ?
On a signal layer board, is there any reason to have ground/vcc pours on unused copper areas ?


texts: High voltage DC current measurement by inductance?

texts:
I'd like to incorporate a few permanent ammeters in a 600V DC circuit.  I've found all sorts of nifty panel ammeters, both analog and digital, but most are rated to less than a tenth that voltage.

I have a clamp multimeter, so I know that it's possible to use the Hall effect to get decent current readings without dealing with the high voltage.

But for a permanent fixture: Are there any components that I can wire the high DC in (or through) to measure the current at a much lower voltage?  I'm imagining something like this, with some convenient component taking the place of the "Clever Component":

simulate this circuit – Schematic created using CircuitLab

NB: Just because I'm thinking of inductance doesn't mean that has to be the mechanism by which this is achieved.  All solutions welcome!


texts: How to place an exposed pad (pad should not be covered by stop-mask) on a PCB in Eagle?

texts:
I am stuck on a problem while working with eagle. I have to design a pcb which has large exposed pads on the top and bottom of the PCB. I had assumed that placing a tstop layer on the pad while designing it from scratch would have done the job.

However, when the PCBs were made, pads on the bottom side of the PCB were covered with solder-mask and are now useless. I have to now remove the solder-mask from them somehow.

Can anyone explain what I did wrong here please?

The image shows the bottom side of the PCB and I had placed tstop and bstop layers on the pads while making them. But they still ended up coated with solder mask. What went wrong?


texts: Variation of voltage gain with frequency

texts:
For a transistor amplifier, the voltage gain

  (a) remains constant for all frequencies.

  (b) is high at high and low frequencies and constant in the middle
  frequency range.

  (c) is low at high and low frequencies and constant at mid
  frequencies.

  (d) None of the above.

My attempt: probably naive, since there is more change in voltage at higher frequency it should be  option (b) but this is wrong and the correct one is ____. ( I know the answer but not reason)

Any explanation at the level of high school(12th class) would be helpful.

Edit: after comments , the only amplifier circuit diagram discussed is given below


texts: Can someone explain this schematic and how to modify it to add PWM LED dimming?

texts:
I bought a LED bulb (AC175-265V, 7W, 59mA) to made some experiments with it and inside there's this circuit:

Can someone explain me how this circuit works? The small transformer package with a single coil may be treated like an inductor?

In addiction to this I would like to modify it adding an ESP8266 and a PWM controller to allow WiFi LED dimming feature to it. Is it possible?


texts: Can a PTFE coated wire heat up enough to be used as a heating element

texts:
I saw a comment on another post about using PTFE coated copper wire as a heating element for a thermos. Would this setup really work under low power(the comment said the source was a usb port) as I assume the PTFE will insulate some of the heat.
Will this be a suitable material for my project. I am trying to keep a mug warm using a wireless charging pad (~7.5W).


texts:
I want to find Z parameters in hspice. I used following commands.
.AC DEC 25 100 2G
.probe ac V(shortI)
.probe AC Z11(R) Z22(R) Z21(R) Z22(R)
.print AC Z11(R) Z22(R) Z21(R) Z22(R)

However I'm not able to get output.
Can I know how exactly should I proceed?


texts:
Seems like a simple question but I've searched and not found good answers.
It comes down to signal to noise ratio equation. What are the differences between the generations in terms of:

Frequencies ranges used
Modulation types
Signal strength (amount of towers)
Spectrum re-use (smart antenna/comm systems)

I can't think of anything else that makes a fundamental difference to the data rate, so it must be mainly these parameters that change between 3G,4G, 5G and 6G...
Please help


texts:
For my bench power supply, I am willing to make a voltage divider with two potentiometers (for coarse and fine tuning). I think I got the schematic right but what I am not sure about is the influence of resistors scaling.

Here is my schematic sample:

I think my schematic is working in theory, but it would also work with R1 and R2 at 500k. Or R3 at 100k and R4 at 1M, and so on... In theory, the resistors scaling always give the same result (at my knowledge level -> beginner).

From my search results, it only seems to influence the output impedance of my PSU but I don't understand what it means practically?


texts:
Which would be the startup sequence of a Microcontroller.

Clock - Power - Reset

Power - Clock - Reset

I think it would be the second one because clock is always running, right?
The noises in the environment, would make the crystal oscillation. But without the power to the Micro, the noise signal would not get amplified and we would not get the crystal frequency.

So, Power - Clock - Reset.

Is my understanding right


texts:
I noticed this LED setup in a datasheet for the Kingbright SA40-19EWA. Instead of the leds being in a simple series or parallel setup, each segment of the display has four sets of two leds in parallel, but each set is in series.

I know the lights work, but don't have one of the displays to cut up to confirm that they are actually connected like this. I'm not asking for how this specific part works, but generally, can this wiring setup, as presented, actually work? How does the current flow, how would the voltage drop be calculated? I know some of the users here have simulation software, maybe they can confirm if a simulation of this would work?


texts: Most efficient way to power a 5 V circuit from a 14.8 V battery

texts:
I am making a DIY Raspberry Pi laptop. So far I have found a suitable board that will drive my display (M.NT68676.2A). From research I have found out that it will run off of anything from 12 V to 5 V, and that it uses around 3 A (I am not sure if that's at 12 V or at 5 V). I've also found a 14.8 V 6600 mAH Li-ion battery from Tenergy that I'm thinking of using (5 A output max).

What's the best way of converting the 14.8 V output from the battery to a suitable 5 V for both the board (5 V 3 A?) and the Raspberry Pi (5 V 2 A) without wasting too much energy or spending too much?


texts: Simplest circuit to light an LED in parallel or series to a Li-ion battery being charged

texts:
I have a very small TP4056 based li-ion battery charging circuit board. It has integral LED charging status lights, but I would like to add a remote LED to indicate when a battery is inserted and actively being charged.
The TP4050 has an input of +-5VDC and output two connectionsfor the battery under charge.
How could I hook up a simple LED using only the +5V input connections and/or the output connections to the battery so that when the battery is connected and charging is active, the external LED lights ups? I thought about just piggy backing on the internal LEDs, but they are very tiny surface mount devices and I cannot solder to them without most likely damaging the board.
Any ideas?


texts: I2C Device Address Changing and Retention - VL53L0X

texts: I am currently working with VL53L0X Time of Flight sensor and wanted to ask that whether the device retains the new address after it has been changed upon powering it off. Till now I have not been able to find proof in the data sheets or maybe I am skipping something.


texts: Can I use both I2C and SPI at same time with PIC16F1503

texts:
Im new to Microchip microcontrollers and I'm looking for very low cost device with I2C and SPI. I want to connect one I2C (ADC) and one SPI device (LCD).

I found this very low cost device:

However it looks like I2C and SPI share same hardware.

Question: Can I use hardware I2C and SPI in one circuit?


texts:
I can't understand how to apply common mode and differential mode concepts.

1) I know that if I have two signals v1 and v2, I can always write them as:

v1 = vcm + vd/2

v2 = vcm - vd/2

Example: v1=7  v2=5

then:

v1 = 6+1

v2 = 6-1

In general, if v1 and v2 are functions of time, I will have a common mode which is a function of time as well (because it's the average of v1 and v2)

2) If I consider the differential stage (two mosfets with sources in common and a current generator under them), I replace v1 and v2 in terms of vcm and vd/2

For small signal analysis the circuit is linear, then I can apply superposition principle and analyse the circuit.

This is what I understood, but now there are my doubts.

1st doubt: the Sedra-Smith book analyses the effect of the common mode, and it says that the common mode can be the result of some noise which is common to both terminals of the differential stage. It seems that, if I idealy would be able to remove noise, the common mode would not exist (but in the previous example, the common mode was 6). Here's the doubt: is common mode something which is added by the external environment or does it exist every time I apply two signals (and in this case it is their avarage)?
If common mode is a common noise, I then would have:

new v1 = old v1 + noise

new v2 = old v2 + noise

and then I would always be able to compute a new common mode (average of new v1 and new v2) and a differential mode (new v1 - new v2).

Then, why should I care of noise? It is sufficient to know how the circuit reacts when a common mode is applied (hopefully it should rejects common mode as much as possible)

2nd doubt: When dealing with differential stage, Sedra-Smith always considers a constant common mode voltage, but in general it is the average of two signals which are functions of time, so the common mode voltage in general should be a function of time as well.

3rd doubt: All the books I read consider as v1 and v2 two sinusoidal signals with same amplitude but with 180° shift. Then of course common mode voltage is 0 and differential signal is the sinusoidal itself. The question is: why consider only this particular case? v1 and v2 are, in general, generic functions of time

4th doubt: Is common mode related, in some way, to the feedback which is usually used with op-amps?

Thank you


texts:
I have an motion sensor circuit. The circuit calls for a voltage of 2-15 dc volts. On the PIR data sheet the source pins calls for a pull down resistor of 47K at 5 volts. My question is if I use 8 volts on the circuit do I need to recalculate the source pin resistor? I have searched this forum and others for the usage of higher or lower voltage, but cannot seem to find any examples. All examples are made around 5 volt.

Sorry . I do not have a data sheet on the circuit. I am using PIR325 on the circuit I have now and it calls for a 100R resistor and it seems to be rather slow. I am using 8 volts on it and I have the circuit tied into a PICAXE 08m2. I also have a regulator and a diode for the voltage on the picaxe. I am posting a picture of the schematic for the circuit without the picaxe. The picaxe is tied into the circuit a the large dot next to the led. I want to change PIR to a PIR LHI878. Here is the data on the PIR. excelitas.com/downloads/dts_lhi778_lhi878_pyd1388.pdf –


texts: Get transfer function from electrical scheme

texts:
Is there any software/SPICE tool in which I can draw electrical circuit and after that, software prints the transfer function in Laplace domain?

I will find this kind of tool very helpful and purposeful. I know how to derive it on paper an how to get bode/nyquist plot in software, but sometimes circuits are complex and could take me an hour or so just to get the transfer function.

Thanks :)


texts: pir motion sensor sensor - working principle

texts:
I read about how PIR sensor works. It is written that it has two slots that convert IR energy to electrical voltage pulses.
The working principle is to diff between the two slots and when the differentiation is not zero it is means that new object(human) has just entered the field of view (FOV).

If I am sitting and NOT moving in right edge of the FOV I assumed the diff will always gives non-zero at after the diff-amp and thus the sensor's output will be HIGH even if I am not moving.
I try it but the sensor didn't signal HIGH. It doesn't matter if I am not-moving in the right edge nor the left edge.

My question is why?
Why if I am constantly giving high energy to one part(slot) of the sensor it is not constantly trigger the alert?

Data sheet can be found here

Thanks,
Daniel


texts: Eagle component has mixed tPlace and tDocu drawings

texts:
I'm designing a board with Eagle and I have placed some LEDs from the led library that comes with Eagle.

With the default layers activated, the LED looks correct in the Board (the anode and cathode can be distinguished by the flat part of the LED)
However when Exporting the board for manufacturing, the LED looks different and it's not possible to distinguish the anode from the cathode (which may lead to solder it incorrectly).

After investigating a bit I realized that what I see in the design is actually a combination of the tPlace and tDocu layers (I'm guessing they where added later in a revision but in the incorrect layer).
When exporting the board to be manufactured, only the tPlace layer gets printed in the board and the tDocu gets discarded in the physical product.

Since it's not a library that I made but a library provided by Eagle I'm wondering if:

Can I modify and correct the libraries provided by Eagle?
Can I force the tDocu layer to be printed in the actual board (to both tPlace and tDocu get printed)

I can of course create my own components, but if I can use the standard components it will save me a lot of time.


texts: Do I understand the off state (0/0) of an SR latch correctly?

texts:
Can someone please confirm if I understand this correctly: When neither R nor S are on (both are 0) it seems to me that at first both outputs are 1, then it feeds back through, and both go to 0, and then back to 1, infinitely?

But this assumes that all the signals travel precisely exactly as fast. As I understand it, in the real world there are teensy variations in the response times of the electronic components, which will lead to one of the outputs being stably on and the other being stably off. However, the collapse of the oscillating circuit is NOT due to the logic of the circuit, but the imperfections of the real world.

Again, as I understand it, if we had perfect components with no variations that could perfectly replicate the circuit in the image, then both outputs would oscillate between being on together and off together forever - or at least until R or S is set.

Now for the big question: is this 100% correct, or have I made a significant mistake? Because trying to understand the off-state of this circuit has been breaking my brain. (Just a regular fellow with no electronics experience here and a bit of understanding of logic.)


texts: Error 4109 No device detected in Atmel Studio

texts:
I'm working on a project involving an ATSAMC21. I soldered it onto the board and tested all pins to ensure that; a) they weren't shorted to the adjacent pins, b) they were connected to the nodes that they should be connected to, and c) they weren't connected to any node they shouldn't be connected to. This solder went pretty smoothly, there were only a couple pins that weren't connected, which I touched up.

When I plug it in to my programmer (Atmel-ICE) and try to program it, I get Error 4109 No device detected. I begin checking the power pins, and all are at 5 V, except VDDCORE, which is at 0 V. As I understand it, VDDCORE is a 1.2 V output. I am pretty sure that this is related to whatever is causing the error.

All power pins have bypass capacitors, most are 0.1 uF capacitors, however VDDANA has two 10 uF capcitors separated by a ferrite bead.

I was very, very careful when soldering it, so I don't think I damaged the chip. I have reasonably good equipment, and was using an ESD mat/strap the whole time.

Does anyone know why VDDCORE could be 0 V?

VIN, VDDANA and VDDIO are all 5 V.

Thanks!

Here's the schematic:

According to the datasheet, VDDCORE is a 1.2 V output.


texts: Which of these Stripline Impedance Calculations is correct?

texts:
Different sources are giving me drastically different characteristic impedance values, and am hoping someone will verify them for me.

Generally, with microstrip, I start with an online calculator to get close, then use the free TNT Field Solver to actually calculate the values.  The values differ, but are at least in the same ballpark.

However, with a stripline, the values are so different that I think something must be wrong.

I'm targeting 50 Ohm.  TNT says to use 9.4 mil traces.  The calculator at EEWEB says the traces should be 25.7mil (!)

Which of these is correct?

Stackup:
Upper ground plane: 1.35 mil copper
Dielectric: 6.7 mil FR408 (3.67 dielectric constant)
Stripline layer: 0.7 mil copper
Dielectric: 47.0 mil FR408
Lower ground plane: 0.7 mil copper

EEWeb:


texts: Why are multimeters much more sensitive than oscilloscopes?

texts:
I have a circuit where I have to measure tens of uA of currents.

When measuring it with a 50Eur multimeter, the multimeter shows the currents with acceptable accuracy and so far no significant influence the was observed doe to the resistance of the multimeter.

When trying to achieve the same with a 12bit oscilloscope, I have to use 500Ohm shunts to get a measurable voltage. This resistance has to much of an influence on the whole measurement.

How is it that a 6 times cheaper device (the multimeter) is so much better in measuring low values than the oscilloscope?


texts: Recently I did the experiment of input and output characteristics of BJT and I saw that "2N363PNP" was written on it.I want to know what does it mean? Is it only a name ?I can guess that it is a PNP transistor but what does 2N363 mean?


texts: How do I translate product requirements into components, schematics, and programming?

texts:
I graduated with a degree in electrical engineering, but a) I've been doing mostly project management since, b) I didn't get my ADHD diagnosed until after I graduated, and c) I feel like inappropriate emphases were placed on basically every subject during my schooling (treating subjects that are not nearly equal in importance as though they are).

I have a project that I want to realize that will require assembling electric and electronic componentry and a fair amount of programming. I have some general ideas of how I want to proceed, but as for turning those ideas into a reality...I'm at a loss. How do I power my components? How do I detect when they're plugged in? What microcontroller should I be using? Should I be using a dev board? Should I be using an FPGA? How much power am I going to need. I recognize that these are all questions that need to be answered, and I have some idea of how I'm going to answer some of them, but I'm somewhat at a loss as to determining the "best" approaches to doing things.

I'm certainly not asking anyone to answer those questions for me; they're all dependent on what I'm trying to do, etc. What I'm asking is how does one figure out the answers to those questions? How do I know what "things" already exist as components, and what are some ways to evaluate those components in terms of suitability? How do I know the best way to develop the software needed for my project?


texts:
In my digital design module involving HDL (Verilog) and a ton of RTL diagrams, our lecturer always said never to use demultiplexers because they do not exist.

Why is that?


texts: LTSpice: One component value dependent on another's value

texts:
I've asked this on the LTSpice group and am getting conflicting answers.

I have a tank circuit in a sim I'm working with, and I need to look at the effect of changing the L value across a range (using .step statement) and of course the companion capacitor value needs to be adjusted to match.

.param F 500000
.step param L 1uH 10uH 200nH
.param C (1/(2*Pi*F))**2/L

The capacitor value is set to {C} and the inductor set to {L}

I've been told that this "should work" and that it "will not work".

I suppose it comes down to when the capacitor value param statement is evaluated. When I run it, I'm told that it can't resolve the parameter C.

I'm not married to this approach, it simply seemed the most obvious way to proceed, but I do need to be able to adjust the C value to match the L in each run.

If this can't work, is there a way to get to what I need, having the C automatically adjusted to resonate with the L?

Sphero:   I'm not sure exactly what you mean, and what I'm doing isn't working.

I have .param A = (2*pi*{F}) and .param B = {A}**2 and .param C = (1/{B})/{L}
"Missing expression in **2" is the result.

The Photon:

This version: {(1/2*pi*F))**2/L} gives me Error: undefined symbol in: "(1/2*pi*[f]))**2/l"

So I tried this version, setting the value in the component to:

{(1/2*pi*{F}))**2/{L}}}    Error: undefined symbol in: "(1/2*pi*([f])))**2/(l)"


texts: How do you decide the shape and limit of polygon on power plane?

texts:
Consider: you have a power plane on a 4-layer PCB with different power rails of different values on this power plane.

How do you decide shape and sizing (border / limit) of polygon on the surface of the plane and why?

Do you cover whole PCB plane with power polygon by splitting area with only power polygon or do you keep some space empty of power? Do you cover some space with ground area on this power plane? Why?

What shape and position should be avoided and why (such as edges)?


texts:
I have a diode.  It has a forward current rating of 40 mA.  It has a surge current rating of 100 mA for t <= 10 usec.  There is no mention of a duty cycle in the datasheet.

Is there a rule of thumb for determining what kind of off period I need in order to not kill the diode?  The naive assumption is that if I do 100 mA for 10 usec, and I need 40 mA forward current as an average, then I would need to use 10 usec on, 15 usec off.

If that is the case, then my intuition would then suggest pushing 80 mA for 9 usec, and then double the off period to 30 usec minimum.  This would allow for overhead like temperature, lifespan, etc.


texts: Arrangement of discharge resistors for capacitors in series

texts:
These 2 circuits consist of voltage source, 2 capacitors in series and their discharging resistors.

Capacitors C1 and C2 are put in series because voltage V1 is higher than rated voltage of each capacitor. Nominal values of capacitors and resistors are the same (C1 = C2, R1 = R2). Only difference between both circuits is the link between points A and B.

simulate this circuit – Schematic created using CircuitLab

In case that the real values of R and C match their expected nominal values, both circuits should behave in the same manner, since there is no voltage difference between points A and B.

However, if, for example, capacitance of C2 drops due to wear and voltage in point A increases, there will be (initially) a voltage difference between points A and B. That higher voltage could possibly further damage the capacitor. In case of Circuit 2, current will flow through the link A-B and the circuit will eventually reach an equilibrium, where the voltage on the A-B link will be V/2 (if R1 = R2). This could (possibly) prevent the capacitor C2 from total failure due to overvoltage. Therefore, from this point of view, I would say it is better to add the A-B link, as shown in the Circuit 2.

My question is, could there be any negative effects of adding the A-B link?


texts: Relation of case temperature to junction temperature

texts:
I'm comparing the thermal characteristics of two ethernet switch ICs.  They both come in the same package and their thermal resistances are:

IC1
θja 51.42 C/W
θjc 20.66 C/W

IC2
θja 41.54 C/W
θjc 19.78 C/W

Test data for IC1 shows that the case temperature was 58.8 C and it dissipates about 1.2W.
I ran a test for IC2 and the case temperature was 65 C and it disspates 0.7W.  The ambient temperature for both tests was 23C.

I was expecting for the case temp of IC2 to be lower since it dissipates lower power.  How does the case temperature relate to the junction temperature.  The Tjmax for both ICs is 125C.  Is it safe to assume that the Tj in IC2 is higher than in IC1?


texts: Are tantalum capacitors safe for use in new designs?

texts:
I've heard it suggested that "solid tantalum" capacitors are dangerous and may cause fire, may fail short circuit and are fatally sensitive to even very short over voltage spikes.

Are tantalum capacitors reliable?

Are they safe for use in general circuits and new designs?


texts: Reset Interrupt - Beginning or End of ISR?

texts:
Im working on a uC that has interrupts configured for various FIFO's present in the uC. Each FIFO is connected to a common bus and can receive data independently(at any point of time). Now, everytime a FIFO receives 8 bytes of data a single ISR is called and in the ISR I have to identify which FIFO caused the interrupt.

What I would like to know is whether the Interrupt must be reset at the beginning of the ISR function or the end.

Problem1 that may occur: Suppose I reset the interrupt at the beginning of the ISR,if another FIFO gets filled while I'm in the ISR, since I have reset the interrupt, what will happen? Will it automatically re-enter the ISR after I execute the last line of the ISR or will some other problem occur?

Problem2 that may occur: Suppose I reset the interrupt at the end of the ISR,if another FIFO gets filled while I'm in the ISR, since I have not yet reset the interrupt, will I re-enter the ISR I have executed the last line of the ISR?

Where is the best place to reset the interrupt?
Please do excuse if my understanding of interrupts is wrong


texts: Why download and upload speed is different in 56k modems?

texts: I have read that this is due to the absence of an A/D or D/A conversion (only) in the down stream which would normally introduce some quantization error. This conversion is present in the upload, so the speed is then 33k. I can understand that some analog to digital conversion is needed only for voice transmission. Does this mean that this speed is only for voice transmission?


texts: How to make a clean amplified microphone analog to digital conversion?

texts:
I've asked a couple of questions relating to this project the past couple of days, but I cant seem to put it all together.

I hooked up an electret mic into an opamp and gave output to my arduino microcontroller.
The ADC on the microcontroller converts a range of 0 to 5 vV to a 10-bit number (0 to 1023).

I tried 3 different amp chips:

LM386 - I got feedback this chip was no good for this purpose, since
its not opamp, and it didn't work correctly as expected.
LM358 - works
UA741 - works, amplifies more than LM358

I followed this schematic exactly (except for I messed around with resistor values to get good gain): I used 50k ohm for R5 and 10 ohm for R2.

The problem is that the output from the latter two chips is not "clean". The analogRead() on the Arduino is always reading a non-zero value even when I make no noise in the mic. The reading reacts properly when I make noise, but the "zero" value is non-zero. Sometimes the "zero" value even flickers throwing off the reading all the time. Hopefully that made sense.

Can you help me sort this out?

Just as unimportant, extra information: I'm trying to make something like this, eventually.


texts:
i want to make this part of circuit .

It uses 24AA32A IC. Can i use AT24C32 instead . im worry about A0, A1 and A2.

my question : if i want to use 24C32 , to work exactly like 24AA32 i should not connect pin A0,A1 and A2 to ground and left them NC ?

AT24C32 Datasheet :

24AA32A Datasheet :


texts: 2.4GHz antenna feed routed through pcb via?

texts:
I'm working on designing a BLE device, and have settled on using a chip antenna. It seems, however, that my BLE SoC is going to have to be on the underside of the board, which might be significantly more shielded?

If that is the case, is it possible to route the antenna feed through a via in the PCB in order to have the chip antenna in a less shielded position, without adversely affecting the RF characteristics?

The PCB itself is going to be sat 4mm down in what is effectively a 15mm deep aluminium tin with no top.


texts: Use to switches to provide necessary voltage

texts:
I am wondering how to work this out and have been busting my head over it over night.

In fact, I was working on this till 03:00.

In all, my shed is solar powered. I am only powering some LED 1W lights (8 of them).

I have a dusk/dawn switch (SW1) that will activate the light circuit on.

I have another switch (SW2) in series in the door. This will switch the lights on upon opening the door.

Now the tricky part. I have a bypass switch (SW3) to switch the lights on during the day time, should there's the need to.

This switch is in series with the door switch (release to make connection).

Now the problem here is, I might want the lights on if I am to close the door but this won't happen with the current wiring as when the door switch (SW2) is pushed in, it breaks the circuit.

What I then did was to add another switch (SW4) in series with SW3.

But what if I leave the shed and forget the lights on?

I thought, why not connect a small 12V buzzer that will power on when I open the door (SW2)?

But I need only to provide it half the voltage as the other half will be provided by SW4.

Why this setup? Because if I am to supply the whole 12V to the buzer, SW2 would provide it, so I need to cut it in half so that the initial half is provided by the SW4 and the remaining voltage provided when the door is opened therefore reminding you that the lights are on.

Makes sense?

Can this be achieved as I am thinking by adding a resistor to the end of SW2 and SW4?

I'll work on a circuit drawing to help better.

Many thanks in advance.

Regards,
Albert


texts: Can I run matlab on a microcontroller?? and if yes which one?

texts:
I am working on a complicated robotics project which involves MATLAB image processing algorithm and LEGO MINDSTORMS interface as well as an Arduino.  The system works dependently in a sequence according to each reading either from the Arduino or to give a command to the LEGO bricks.

The question here is can I replace the processing from PC to another external microcontroller like  Raspberry Pi for example but without converting the matlab code as installing MATLAB itself on the microcontroller to compile the code?
If so, what microcontroller would be convenient for this and if no what is the best solution to control the system without the need of a PC.


texts: Two windings transformer to autotransformer

texts:
Let's say that we have a transformer with two windings

(source: circuitstoday.com)
with nominal power \$S\$, nominal voltages \$V_1\$ and \$V_2\$ and windings \$N_1\$ and \$N_2\$ respectively.
The equivalent impedance is \$R+jX\$ referred to the primary winding.
Now we rewire this transformer to become an autotransformer.

(source: vias.org)
and the secondary has nominal load with lagging factor \$\cos \phi\$.
I am a little confused so my questions are: Does that mean that the voltage \$V_x\$ is equal to \$V_2\$? What about \$I_x\$ or \$I_H\$? How can we find the voltage \$V_H\$?


texts: Circuit design to vary voltage and switch outputs

texts:
I'm new to the scene and I don't know where to start or terminology, so any advice or links are appreciated :)

What I need to build is a Magic Box™ that turns 120v AC into variable DC (0-15v) at 1 amp.  The trick is that it needs to have 5 outputs, each with their own pots to vary voltage but only one output can be on at a time

So, kinda like a radio button I'd like each of the 5 outputs to have a momentary switch that, when pressed, switches the corresponding output to 0-15vdc at 1 amp and cuts power to the previous output.  Like I said above, I'd need each output to have it's own voltage pot.

Finally, I'd need to have one LCD that shows how much voltage is going to whatever output is currently selected (± 0.05v).  I'd prefer having 1 screen that switches with the output instead of 5 separate screens.

I'm not asking anyone to sketch this out for me!  But if there are links to similar projects, I'd like to see them!

Unfortunately I'm not familiar enough with the terminology to know where to start, so if you could let me know what general parts I would need, it'd be very much appreciated!

Thanks


texts: how do I design a fan fail circuit (open circuit or fan not moving etc) for a 115VAC two wire fan and illuminate a 115V Panel indicator?


texts: KMAP Sum of Products - How to get the Simplified Function from the KMAP Table

texts:
I am answering a KMAP Sum of Products with don't care table but I don't know how to get the simplified function. Here's my progress:

Problem:
Q(C, O, D, E) = Σ(0,1,2,3,7,8,10) + d(5,6,11,15)

The only remaining to solve is the simplified function which derives by encircling number 1's (sometimes with don't cares). How to get the simplified function from on this problem?

P.S. Not 100% sure if that is the right answer of encircling number 1s


texts: Can I put multiple resistors in series to get higher resistance?

texts: If I put 3 1MΩ resistors in series, is that the equivalent of one 3MΩ resistor?


texts: Documentation generator for embedded C projects

texts: I'm looking for the equivalent of what Javadoc is to Java and from that, a way to standardize code documentation.  Is doxygen more common in this context.  Are there built-in, IDE-dependent options? I'm interesting in documenting a project in MPLABX.


texts:
I am trying to get a pushbutton working with the Arduino Button tutorial (and the example sketch). Unfortunately, I was not able to find a button like the one in the example and, instead, have a button with two pins from the bottom. (I don't know if this makes a difference - just trying to provide the information).

Below are pictures of my wiring of my breadboard and Arduino board. Am I doing something wrong here?


texts: Why does the seven segment display have decimal point at the right?

texts:
All the seven segment displays I’ve seen so far have their decimal point to the right of the main digit. Why is this so? A decimal point to the left will be able to represent more possible combinations of numbers.

A single digit display with a decimal point on the left can represent nine more possible numbers (\$ .1,\ \ldots ,\  .9 \$) than the common display with decimal point at the right.

Edit: Why also do the digits lean towards right?


texts: Two weaker peltiers vs one stronger peltier for cooling?

texts:
I'm planning on making a small water cooler for a project. I need to cool approximately 1.5L of water and have two TEC1-12706 (12v 6amp) peltier modules, and hoping to cool to as low as 6 degrees Celsius.
Would it be more efficient/effective to instead use a single Pelt such as the 12715 (12v 15 amp) or run the two separate lower rated ones? Or even two 12715s at half power for example?
Also any advice on calculating the ideal heat sink size/fan speed would also be very useful


texts: Equivalent time sampling on microcontrolers

texts:
I must admit, I don't know too much about analog electronics but I am keen to know if it possible to construct an equivalent time sampler (ETS) using the A/D's on a micro.

I hope this question isn't too vague. Basically my understanding is that ETS is used to sample very high freqeuncy signals and is a trick that is used for digital oscilliscopes.

Wondering if anyone has tried this before or knows of a good reference.

Regards,

Nathan


texts: What polyfuses protect USB ports in a typical modern PC?

texts:
I would like to know what is the typical rating of a polyfuse used on modern PCs (desktop or laptop) with USB 2.0 and 3.0. TE Connectivity apparently recommended in 2011 that a single USB 2.0 port (non-ganged) be protected by a polyfuse with hold current 750 mA and trip current 1.5 A, and double that for USB 3.0 that is not charging-enabled, and higher still for a charging-enabled port.
However, I have been unable to find the actual specification of the USB polyfuse ratings for desktop PCs and personal laptops. Many technical manuals I could find for various PC models mention that they do have over-current protection, but for whatever reason invariably neglect to give any further detail. (I recall some of them explicitly stated "polyfuse" but do not have them at hand right now.)
I can find Littelfuse specifications for the above-recommended polyfuses, and the Littelfuse 2016 selection guide recommends using one of its 0805L, 1206L, 1210L, 1812L or USBR polyfuses for USB, and all of these have hold current at most 2.6 A, but I have no idea what PC manufacturers actually use.
If "modern PC" is too broad, I am happy to know the answer just for the Dell Optiplex 780/790, the HP Pavilion p7-1030/1154 and the Lenovo Thinkpad X220/X230, which is around the time that integrated USB 3.0 ports seemed to start appearing (2011). I understand that later PCs can have BC (Battery Charging) 1.2 ports or PD (Power Delivery) ports, which are rated to provide up to 5 A, and so would have much higher overcurrent protection limits, which I am less interested in. My main motivation for asking this question is to know whether plugging a faulty device into an older USB port can ever result in that device drawing a much larger current (but not short-circuit) than the USB specifications provide for, and how much more (before the polyfuse trips). I chose these relatively popular PC models, but if you can only find information on other Dell/HP/Lenovo models, that would also be helpful.


texts:
I have a Raspberry PI and an 12V LCD board for a laptop salvaged LCD. I'd like to have a battery backup system when there is no electricity. I've designed such diagram. Please let me know if you see any problems & improvements. I've added also component pictures which I'm going to use.
When there is electricity coming from DC adapter, relay will be open and disconnect the battery from the circuit. Otherwise Arduino Nano will close the relay and current from battery will reach to Raspberry PI. Why I'm doing with Arduino, I'm already using it for volume control and safe shutdown etc.
I'm not sure about upper side of the design, should I use 7805 and 10k resistor to send signal to Arduino that adapter is on, or any voltage divider etc.
Please check it and tell the thoughts.


texts: Running bldc motor without hall effect sensor or back emf

texts:
I'm new to working with motors. Recently I was working on 3 phase BLDC motor. I needed to build a gate driver + 6 MOSFET circuitry but instead, I have BDC motor drivers from Hindustan Dynamics called Hercules Driver. Now, I need three BDC drivers to drive one 3Phase BLDC motor. I did all the connections and using Arduino mega 2560 I got everything working but without using feedback from either hall sensor or back EMF. I'm applying following sequence to the motor phases

 A      B      C
 1     -1      0
 1      0     -1
 0      1     -1
-1      1      0
-1      0      1
 0     -1      1

where 1 is VCC and -1 is GND and 0 is OFF(open circuit).
Surprisingly motor starts spinning without any problem. Then I moved rotor manually to a random position and again tested with code even then motor starts spinning in right direction and at the right speed. I tried moving motor rotor to a random position different from where it stopped and each time motor rotates perfectly. As I understand from the literature that it takes some kind of feedback to drive BLDC motor but I don't observe that here.
My motor has the following configuration:

Number of poles: 16
Number of winding slots: 18
Motor voltage: 24V
Current cap: 3 Amp

What is the role of feedback and how to use it?
Thanks in advance.


texts: Protect Beaglebone Black from Power Outage

texts:
I am using a BBB (Rev C) as a web server, powered by a 5V power supply connected to the 5V jack. I read in several locations that disconnecting the power supply to turn off the board can damage the board.

Is this an issue if the BBB is running and there is a power outage? The web server is used as a web front-end to a MySQL database and is used fairly infrequent. Most of the time, the BBB is idle.


texts: I have seen videos of people actually being able to power on a Marx generator with no problems whatsoever but however they never show the complete setup and diagram of their circuit and real physical layout. So more specifically, how is the power supply wiring done and what are the prerequisites prior to setting up and powering on a Marx generator?


texts: How to implement `analogRead` (Arduino) on AVR?

texts:
I'm trying to implement Pin class in C++ with digitalRead, digitalWrite, analogRead and analogWrite methods like in Arduino SDK.
I know how to read analog signals using the ADC input number (not port&pin number).
But in my class, I know only about port and pin and I want to check if this pin is supported ADC and if it is, I want to get the ADC channel number. How can I do it?

For example, I have only PORT C and pin 5, and I need to get 5 ADC channel number.
Thanks in advance!


texts: Is there a simple Geiger counter component?

texts:
I'm looking for a simple electronic Geiger counter element. In my design I need to detect radiation and did not know what my options were for components to detect radiation.

What components exist for my need and what kind of complexity is associated with them?


texts: High side P-channel mosfet switch for BLDC driver (42V ~13A at peak)

texts:
I'm trying to design high-side switch for BLDC motor controller(42V ~13A). I understand that low-side switch is more efficient in this case, but controller schematics(bought as is) has an issue. It applies 42V to signal pins in case if ground is not connected. So here is schematics that I supposed to have:

simulate this circuit – Schematic created using CircuitLab
So few questions:

What transistor do I need to have in this case?(Q1)
Do I need pullup resistor R5 at all?
Overall how this scheme might be improved?

Thank you!


texts: Why are thyristors used in xenon trigger coil circuits?

texts:
Looking at the datasheet for the ZS1031-11(H) trigger coil, the test setup activates the trigger coil with a thyristor:

In the datasheets for other trigger coils, and in other circuit diagrams online, pretty much all of the circuit diagrams I can find also use a thyristor.
Why is a thyristor used here, as opposed to a MOSFET or an IGBT? What are the important considerations for this part?
Thank you!


texts:
Can someone explain what impedance and load really are?

I have a textbook in front of me and I have taken and passed the EE class on it, but aside from a textbook definition I can't seem to get a really clear grasp on it. I can read the textbook all I want but I wish there was some simple way to think of this.


texts: Add second sensing circuit to already wired reed switch

texts:
In my house I have a mechanical water meter with a 2 wire reed switch that sends a pulse every 10 liters to (I suppose) an electronic meter to witch I don't have access. I'd like to connect a circuit to the same switch to read the pulses to track my water usage, without interfering with the electronic meter, but I don't know what circuit is already wired to the switch.
The only specs I've got on the sensor are " 24 Vca/Vcc, 0,1 A " and a simple diagram of a switch.

I suppose, being a switch, that whatever circuit is currently connected, it must push a current through it when the switch closes to sense the switch closing. Maybe I could measure when current is flowing to sense the pulses? How could I do that without interfering with the electronic meter? Hall sensor? would that work? There's probably a simpler solution I'm not seeing.


texts: How to I go from generalized Transfer Function to generalized State Space, and back?

texts:
Question: How can I transform a generalized Transfer Function a generalized state space form (preferable with the First Companion Form), and back?

For the sake of presenting an example, let us say that we have the following generalized transfer function:
$$
\begin{pmatrix}z\\y\end{pmatrix} = \begin{pmatrix}G(s) &-1\\ H(s)&0\end{pmatrix} \begin{pmatrix}w\\u\end{pmatrix}
$$
with
$$G(s)=\frac{2}{s+3}$$
and
$$H(s)=\frac{s-1}{s+2}$$

I have not been able to find any information on the Internet related to this. I know how to do this when having one transfer function but don't know when having the generalized form.


texts: Conversion an output of UUT in test bench?

texts:
UUT
component uut_test IS
    port (
            clk : in std_logic;
            rst : in std_logic;
            data_in1 : in integer;
            data_out : out integer
        );
    end component main_integer;

I would like to get data_out as std_logic_vector.  In the test bench it was implemented as :
signal data_out: std_logic_vector( 3 downto 0);

begin
UUT : main_integer
PORT MAP
    (
     clk => clk,
     rst => rst,
      data_in1 => conv_integer(data_in1),
      conv_std_logic_vector(data_out) => data_out
     );

I got the following error:

ERROR: [XSIM 43-3294] Signal EXCEPTION_ACCESS_VIOLATION received.

This error appeared if I convert to std_logic_vector.
conv_std_logic_vector(data_out) => data_out

PS I know I can convert it in Behavioral file ( design).