texts:
So we have a product that has the below connectivity in relation to USB and power supplies. The device is a K66 MCU from Kinetis. Its datahseet is here:

https://www.mouser.com/datasheet/2/813/K66P144M180SF5RMV2-1074869.pdf

While we have 2000+ of these devices in use, there is a weird case which we cannot replicate where some users have the device fails when connecting the USB to their laptop. The MCU physically overheats and dies. This only happens on USB connection.

It is very rare, but there must be something in the design allowing this to happen. No I/O etc burden is placed because of USB, so it is purely USB related only. Stated though, incredibly rare - normally it works perfectly without issue.

Anyone any ideas as to perhaps misues of connectivity? We need the diode in place such that the MCUs USB works (apparently according to SW engineer it requires this "wake up" 5V from the USB port - but we do not want the device to become alive when just the USB is connected. Perhaps this is where the issue lies?

Over DSs
https://mikrokontroler.pl/wp-content/uploads/pliki/KQRUG.pdf
https://www.nxp.com/downloads/en/schematics/FRDM-K66F-SCH.pdf


texts: Charging a battery with more mA than its genuine charger

texts:
I recently bought a compact digital camera and it came with a charger of 5V,  1A output. This is a wall charger and the cable is USB type as in android smartphones. I have another wall charger which is 5V, 2.1A output and this is from my Tablet.

My question is what can happen if I charge my compact camera with the tablet's charger?

Well I have already done it :)  and it obviously charges faster than its genuine but can this harm the battery or even worse the camera?


texts: Generic question about interfacing a microcontroller with a device: when is the current limit a problem?

texts:
I have an Arduino Board, to be precise many models, but let say I want to interface a ATmega328p with another integrated circuit (all is running at 3.3 V). In this case I want to connect Arduino with a A4988 microstepping Driver.
As everybody knows each output pin of the Arduino Board can source or sink  max. 40 mA of current. Looking in the datasheet of the driver I find such electrical characteristics:

which clearly state that the max current 20 uA is.

Now, I don't know whether under those circustances possible is, to connect each Arduino Output Pin with the control logic of the driver directly or not. So here a few questions:

If is it possible to connect both devices directly, how can I make sure that the arduino board doesn't source 40 mA into the driver destroying it? Comparing max current of input and output is the right way to be sure, that nothing is going to fry??
If the current must be sinked to max. 20 uA (because the motor driver is the weakest component in this simple circuit), then I would insert a resistor. But how to dimension it? All what I know is that the output of the arduino board can output 3.3 V as Voltage and max 40 mA. At the input's side I know that a logic O is any voltage between 0 and 0.99 V (3.3 x 0.3 as per datasheet). So I would write:

\begin{equation}
R = \frac{(V_{output} - V_{input})}{I_{max_{driver}}} = \frac{(3.3 - 0.99)}{(20 * 10^-6)} \approx 120 k\Omega
\end{equation}

Is this consideration right or I'm missing something very important or doing a mistake somewhere??

I'm not really sure about the 2nd idea because in the datasheet there is a clear example on how it should be connected with a microcontroller:

But is the depicted example real or is a really simplification which cannot be used but just reconsidered for each different possible microcontroller?


texts:
I have the following problem.

"An amplifier stage with \$A_{voc}=100\frac{V}{V}\$, \$R_i=100k\Omega\$, \$R_o=10k\Omega\$ is connected to another amplifier with \$A_{voc}=10\frac{V}{V}\$, \$R_i=10k\Omega\$, \$R_o=100\Omega\$. They are in cascade, so to speak.

What is the open-circuit voltage gain for this cascade?"

My initial thought was that you just multiplied the two \$A_{voc}\$'s together and there you had it.

That would make the total oc-voltage-gain 1000.

But it turns out the answer to this question is \$500 \frac{V}{V}\$. Can anyone explain why this is?

There were no schematic included for this problem, but I would assume it looks something like this.


texts: Contacting InvenSense MPU9150 auxiliary magnetometer

texts:
I am trying to reach InvenSense MPU9150 magnetometer using master mode disabled and bypass mode enabled. These values are written to and then confirmed from the MPU9150 :

0x6B = 0x01, // Clock from gyro X
0x6A = 0x00, // I2C Master mode disabled
0x37 = 0x02. // Bypass mode enabled

I have then tried to reach the magnetometer through 0x0C->0x0F slave addresses but never received a correct answer from the 0x00 WHOAMI register. Have I missed a register ? The AUX pins on the PCB are floating. I can talk to the MPU9150 correctly and read the accelerometer and gyro data. Could the magnetometer in the MPU9150 be dead on arrival ?


texts:
I am using a TL081 IC, just the +, - and out pins (plus power supplies). I would like to hide the unused pins (offset and disconnected). Which is the right way to do this?

EDIT: and what should I do with the unused terminals? Just leave them floating?


texts: How to use USB to communicate PC with a USB device?

texts:
As I stated above I need to learn to create a healthy communication pathway between a PC and a USB device.

I need to achieve 120MBytes/s(at least)  baud-rate and I don't even have any idea about what kind of board should I use to achieve that.

I've been told that with Cypress FX3 Ez USB board I can arrange the device sided installations easily, but what about the PC side?

Do I have to write some protocol programs to use USB port as a COM port in a desired format? If yes, how to achieve that? Some say that I can do it via libusb on some linux. But I have no experience in such things so these don't mean much to me in practical-sense.

I need a beacon light, a guide, a something to dig further. I couldn't find anything on the net much.

What IDE should I use? What kind of hardware do I need? Any additional software should I use? Any advices so far? A book? Some project examples & application notes; example codes?

Thanks in advance.


texts: Do you need to enable all of the IC's chip select lines to select an IC?

texts:
If there is an IC with multiple CS (chip select) lines, like the (old) MOS 6540 (for example):

Source: cbmhardware.de

Warning: This pinout may not be 100% correct, please take a look at this website: dasarodesigns.com

Is it correct that you need to enable all of the available CS lines to enable the chip (with enable I mean high for high-active CS and low for low-active _CS inputs)?

Not meant to be a 6540-specific question!


texts: Push-on coaxial connector with RF leakage performance comparable to threaded-coax connector?

texts:
In examining the performance characteristics of the push-on SMP connector I've noticed that the RF leakage is at best -80dB  @ 3 GHz and then continues to degrade as the frequency increases to -65 dB @ 26.5 GHz, see: SMP Connector Performance Specifications.

This is quite a contrast from a threaded coax-connector such as SMA which has >-100 dB RF leakage across the operating band: SMA Connector Performance Specifications.

Most of the push-on connectors I've seen use a slotted plug design which I suspect is the reason for the increased RF leakage. Does there exist a push-on connector design that is able to achieve comparable levels of RF leakage as a similar threaded connector?


texts: I designed and made this circuit but it produces only 360V when it should be producing at least +1000V

texts: The circuit consists of a 9V battery (the input source) connected to a 555 astable multivibrator operating at 1.34 kHz frequency connected to a transformer and a long voltage multiplier chain. According to my calculations, the output should be at least +1000V but it's 360V. What's going on?


texts: Where do voltage level limitations of logic level translators come from?

texts:
When browsing through available bidirectional level translator ICs, I always see the condition that reference voltage on one side of the translator must be strictly less than voltage on the other side.

For example, ADG3300:

  For proper operation, Vcca must always be less than Vccy.

Where does this limitation come from? Aren't bidirectional level translators symmetrical in their internal structure?

Also, are there any level shifters without this limitation? (or is it possible to create such?)


texts: where and how to connect battery for RTC of DSPIC33EP512MU814

texts: am working on 144 pin DS PIC am not able to understand how should i connect a battery to RTC of the said pic and which pin of the pic.I need to use internal RTC of the pic


texts:
Well I am trying to make UPS, uninterruptible power supply, for Arduino Leonardo. This is my circuit

I am using for lipo chargher this ICs, it use TC4056A and DW01 . I think main problem is DW01 overdischarging protection

I have read documents TC4056A and changed the R3 resistor to 2.4k Ohm to decrease charging current to approximately 500 mA to prevent much more heating. Charging and mean time Arduino working properly there is no problem. if I plug out the my UPS. Battery start supplying Arduino. But the problem is if battery was totally finished (all lamp's of battery level switch off and Arduino stopped). Battery can not start charging when I plug in the system. I'm measuring the current from type-c side it shows 40mA but I know while normally working it should be 500mA or more. If I plug out the Arduino from UPS battery starts to charging and measuring current goes 500mA. After waiting a moment, If I plug in the Arduino charging goes normally and arduino start to work.
Well I know, I can not good tell my problem. I take refuge in your understanding.
Well I have try to add circuit.

NEW ADDED
after watching this video I understood the problem! the problem is if the battery voltage lower than 3 volts, lipo charger IC will consume only 50mA. I need to remove load until lipo battery voltage level up to 3 volts.
So question was changed! How can remove the load ( at this project "Arduino Leonardo") until lipo battery level over then 3 volts?


texts: I am stuck at a question (about bias current and offset voltage)

texts:
So I was doing the following question from sedra smith microelectronics:

I have managed to do all parts in the question except part d. I am stuck at part d.

The way I have tried is the following: On the non-inverting lead of the op amp, there is a Voltage offset sources attached along with a resister to compensate for the bias current. I used superposition. First I replace the bias current source inside the op amp with an open circuit and so the voltage seen by positive terminal of the op amp is Vos. And then I replace the Vos with a short circuit and also find output voltage. But my answer is not correct. The correct answer for part d is 22mV. Can someone tell me how to solve for part d?


texts: The polarity of the contacts when wiring an EMR

texts:
When reading Omron's datasheet of G6E, I find the words as below:

I can't understand well the words

  "The difference in polarity applied to the contacts will affect the
  endurance of the Relay due to the amount of contact movement".

So, why? And I only see this in G6E's data sheet, not ever in others, then is this only applied to G6E, or common to others?


texts: When should I fire the TRIAC's gate when controlling an inductive load (AC motor)?

texts:
I'm using a combination of opto-triac + TRIAC to control a 230V AC motor with a microcontroller. For detecting the zero-crossing of the voltage I'm using another optocoupler.

I know that the AC motor is an inductive load so the zero-crossing of the voltage comes before the zero-crossing of the current. My circuit senses the zero-crossing of the voltage, but the TRIAC turns off when the current is zero. When should I fire the TRIAC's gate to obtain an arbitrary motor speed (let's say half the normal speed)? How can I know when the TRIAC turns off?


texts: How does a conventional generator produce only reactive power?

texts:
For a class that's rather far outside of my background, I am reading a paper about supply-demand balance in an islanded microgrid. The active power demand of the whole system can be met with renewables, but the authors' control scheme can't balance reactive power, so they say that the conventional generators have to take care of it:

  Thus, the active power reference of the SG is set to zero, and the SG
  [synchronous generator] only produces reactive power for voltage regulation.

Is that a thing? From dispatch and power flow exercises I'm used to having a minimum active power constraint on the generators.

How do you make, say, a diesel generator produce P=0 Q≠0?


texts:
I working on a home pet project for which I bought a rather powerful moter. It is a 24V 90W motor, which says the "Load current" is 5.7A.

I now want to power it with my wall power, so I thought of buying a car battery charger to make the motor run. Something like this for example:

In the description it says it has the following properties:

Rated Power: 50-60Hz
Power: 140W
Actual Output Current: 12V-10A   24V-7.5A

As far as I understand it simply gives 7.5A at 24V, so that should do it. But since I'm an enormous beginner I don't actually know if this would work at all.

Does anybody know if I can buy this to power my motor? All tips are welcome!


texts:
I am studying about limiter...

(pic from Skyworks 200480C.pdf)
In a limiter design, how should I design the RF choke inductor?
If I need to design a limiter at 1-4 GHz and have a spiral inductor as RF choke, I would need a big spiral inductor so that it works better at low frequency but it can't be too big so that its self-resonance frequency won't overlap with the in-band frequency, right?
Any thoughts or suggestions?


texts: What happens at the end of a transmission line?

texts:
Let's say I wanted to make a widget containing a relay to switch between two antennas. There is a coax transmission line coming in from the transmitter, and two going out, each to a separate antenna. Inside is a relay which switches the center conductor, and the shields terminate into a metal enclosure around the relay:

simulate this circuit – Schematic created using CircuitLab

Let's further say that this is operating at HF, so the enclosure is very small relative to the minimum wavelength this device will encounter in operation.

At point A, there is an impedance discontinuity. The coax was \$50\Omega\$, but inside, it will be something else. At point B there's another discontinuity, as we transition back to \$50\Omega\$. So, there must be some wave reflection happening here.

What effect would this have on the transmitter? Would it result in a horrible SWR, or no? Why?


texts: Is it possible to restart XBee with command when power on?

texts:
I am using XBee S2 ZigBee to do wireless communication, but sometimes I met cases that XBee failed to get some data frame and after several rounds it stopped. I found out that after I power off both XBees and then power on again, it will work again. So I guess if I can restart it with command when power on, I might able to make it work continuously.

I am using the python-xbee library to send out and receive data.

The xbee connected to computer side was set to API mode as coordinator; the xbee connected to sensor board was set to AT mode as router.

Is it possible to restart both of them with command when power on? How?


texts:
I'm trying to read the temperature of a Si7050 using a TI CC3220SF. I'm not sure if clock stretching is handled correctly from the TI's driver as well as the NACK option (alternative to clock streching, according to the datasheet).

Is there a way to read that temperature avoiding those specific features? I mean, for me it's ok to send the "measure" command and come back to reading out the converted value after a conversion-time.

I don't understand if it's possible and (if it is) how.


texts:
I'm getting conflicted information about this so why not ask here.

To clarify beforehand: Under DC motor I understand a motor with 2 terminals where you apply DC voltage to get current flowing in 1 direction(some people use DC to describe 3-phase brushless motors)
With AC motors I understand n-phase brushless motors with n amount of terminals where you apply a AC voltage in different phases on the different pairs of terminals.

I also know for a fact that mechanical resistance is proportional to electrical resistance so it's gets even more confusing knowing this.

Now for the actual question: I know that a type of motor can get damaged if stalled. I've also read that current is minimal when a certain other type of motor is stalled. Can I get a explanation which one is which and why?


texts: Why won't my USB powered LED remain on until after the 3rd attempt to turn it on?

texts:
I have a USB powered LED that I use for late night desk work.  It's 8" long overall, housed in a bendy kind of stem with the last 1.5" being the light. It looks like a Popsicle stick that doubles in width for the last 1 1/2 inches. It is turned on by a touch sensor that is situated on the surface opposite the light.

Here's what happens every time I want to use it:
- I touch the sensor and the light comes on for a bit under 30 seconds and then goes out.
- I can immediately touch the sensor and turn it back on and again it goes out in about the same amount of time.
- I am unable to turn it on again until about 45 seconds have passed. But when I am able to turn it on again it will stay on as long as I want.

This has been its behavior ever since I got it about 2 years ago. I've moved it around to different sockets - powered by AC chargers, PC ports and monitor ports and it's always the same. I have several other lights all working with no problem. And I do mean that it's always the same, not just sometimes or often.  Always.

Is anyone able to deduce what is whack about this light?  It's just weird.


texts: Using a CT to measure the current in home electronic devices

texts:
I am developing a project that consists of measuring the consumption of a power strip (not sure how it is in english/figure below). I'm already able to measure the instantaneous voltage using a voltage transformer. My next goal is to measure the current.

For this task, I found that I could use a current transformer with a high power burden resistor to reduce the current in proportion and generate a measurable voltage to be sampled in simple ADC [0V, 5V].

I got the transformer (figure below), but did not get any datasheet or information on how to use it. The only information I could decipher surfing the internet was that the "class" label indicates the error, which is, 1%.

Where I live, the power grid works in 220V-RMS/60Hz. This current transformer serves for this purpose? What is the maximum current it can handle (assuming 220V-RMS)? What does it means the other informations? And above all, what does it means 1.5 VA? It is the maximum apparent power that it can handle?

The circuit I designed to interface between the ADC and CT is in the figure below. Consider that the current source is the CT, because the simulator that I used has no such component.

This schematic is correct?

Last question, should I put both wires (phase and neutral) in the current transformer, or only one of them?


texts: Noise spikes caused by external AC switching

texts:
I have built a circuit that measures time between two 5V pulses. It works good but I'm having problems with voltage spikes that comes from the AC mains. And it triggers the interrupt pin on the PIC.

When turning on/off another power supply on my test bench I get a voltage spike around 5V on the DC side of my AC/DC. I'm using a TracoPower TMP 7105 switch mode supply and there is a built in filter in the device socket.

How should I avoid false readings on the interrupt pin? Filter the signal? Or try fixing the noise somewhere else?

EDIT #1: I understand that I may have explained some things to badly.
I have tried to run the circuit with a battery and the noise disappears, sadly is that not a possible solution.

Here is some captured waveforms with only a 100 Ohms 6W resistor as a circuit.


texts:
I have a DC voltmeter ammeter display that I want to use for reading voltages (up to 30V) on different channels in a power supply.

That display is to be integrated in the supply so I can't do it manually.

Is there any possible way I can achieve this using a de-multiplexer/decoder?

Preferably 74LS138 but I don't want to use relays, I could use N-channel MOS-FETS for switching

The display is the same as shown above:

What I am trying to achieve is also attached:

The MOS-FETs are connected to all the outputs similarly.


texts: What all do I need for a simple speaker circuit?

texts:
I'm trying to use a 555 timer in astable mode to play a square wave sound out of a small speaker, but I'm having trouble understanding all the components I should use.

I think I need something like this:

simulate this circuit – Schematic created using CircuitLab

So the output of the 555 timer switches Q1 on and off, playing a sound out of the speaker. R1 is to limit the current going to the speaker. D1 is a "flyback diode" (?). My speaker is supposedly 0.2 W with 8 Ω impedance.

So here are my questions:

Given those numbers for my speaker (0.2 W and 8 Ω), how do I calculate what value of resistor I need for R1, assuming I'm giving it 5 V? (The actual math is preferred over just telling me the value.) I want the speaker to be loud but not damage it.
What the heck is a "flyback diode", and why do I need it? I tried reading the Wikipedia page, but I think I don't really understand how inductance works. So maybe someone can explain like I'm five. Also, what type of diode should I use for this, and why?
I read something somewhere about putting a capacitor in there somewhere, I think in series with the speaker to protect it somehow. Why would I need that?
Is there anything else I'm missing, and why?


texts: SPI transaction timeout linux device driver

texts:
I am stuck for last 3 days at a point.

I am working on eink device driver with msm8960 qualcomm chipset.

Scenario:
In file: kernel/arch/arm/mach-msm/devices-8960.c

I cannot verify the use of spidm_channels" and "spidm_crci" and the corresponding entries.(msm8960 pro)(copied from some reference code)
How to verify if the values of corresponding start and end are correct??
I have datasheet for msm but cannot find any reference.

I have added the following code in order to create a new gsbi resource in file as:

static struct resource resources_qup_spi_gsbi9[] = {
    {
            .name   = "spi_base",
            .start  = MSM_GSBI9_QUP_PHYS,
            .end    = MSM_GSBI9_QUP_PHYS + SZ_4K - 1,
            .flags  = IORESOURCE_MEM,
    },
    {
            .name   = "gsbi_base",
            .start  = MSM_GSBI9_PHYS,
            .end    = MSM_GSBI9_PHYS + 4 - 1,
            .flags  = IORESOURCE_MEM,
    },
    {
            .name   = "spi_irq_in",
            .start  = GSBI9_QUP_IRQ,
            .end    = GSBI9_QUP_IRQ,
            .flags  = IORESOURCE_IRQ,
    },
    {
             .name   = "spidm_channels",
            .start  = 3,
            .end    = 4,
            .flags  = IORESOURCE_DMA,
    },
    {
            .name   = "spidm_crci",
            .start  = 12,
            .end    = 13,
            .flags  = IORESOURCE_DMA,
    },
};

The reason for having this doubt is that our DMA operation is failing with the error :
from logs:

<6>[    0.764932] wait_for_ready: I/F Ready.^M
<7>[    0.765176] s1d13522_ spi9.0: setup mode 0, 16 bits/w, 51200000 Hz max --> 0^M
<3>[    1.756630] spi_qsd spi_qsd.9: msm_spi_process_transfer: SPI transaction timeout^M

and then if we try to perform another DMA operation it gives the following error:

<3>[    6.773355] s1d13522if_cmd: wait_for_ready: I/F busy bit stuck^M
<7>[    6.775400] s1d13522_ spi9.0: setup mode 0, 16 bits/w, 51200000 Hz max --> 0^M
<4>[    6.775583] ------------[ cut here ]------------^M
<4>[    6.775614] WARNING: at /home/anshul_10605816/hip_mirror_2330_code/kernel        /lib/list_debug.c:32 __list_add+0x58/0x78()^M
<4>[    6.775644] list_add corruption. prev->next should be next (c0d5124c), but was 00100100. (prev=edf643b8).^M
<4>[    6.775675] Modules linked in:^M
<4>[    6.775766] [<c00149b8>] (unwind_backtrace+0x0/0x11c) from [<c007c818>] (warn_slowpath_common+0x4c/0x64)^M
<4>[    6.775827] [<c007c818>] (warn_slowpath_common+0x4c/0x64) from [<c007c8b0>] (warn_slowpath_fmt+0x2c/0x3c)^M
<4>[    6.775888] [<c007c8b0>] (warn_slowpath_fmt+0x2c/0x3c) from [<c02a9538>] (__list_add+0x58/0x78)^M
<4>[    6.775919] [<c02a9538>] (__list_add+0x58/0x78) from [<c001e3d4>] (start_ready_cmd+0x84/0x13c)^M
<4>[    6.775980] [<c001e3d4>] (start_ready_cmd+0x84/0x13c) from [<c001e704>] (msm_dmov_enqueue_cmd_ext_work+0x148/0x284)^M
<4>[    6.776041] [<c001e704>] (msm_dmov_enqueue_cmd_ext_work+0x148/0x284) from [<c0094e0c>] (process_one_work+0x27c/0x484)^M
<4>[    6.776072] [<c0094e0c>] (process_one_work+0x27c/0x484) from [<c0095224>] (worker_thread+0x210/0x3b0)^M
<4>[    6.776133] [<c0095224>] (worker_thread+0x210/0x3b0) from [<c00990c0>] (kthread+0x80/0x8c)^M
<4>[    6.776194] [<c00990c0>] (kthread+0x80/0x8c) from [<c000f108>] (kernel_thread_exit+0x0/0x8)^M
<4>[    6.776224] ---[ end trace da227214a82491b8 ]---^M
<3>[   11.766732] spi_qsd spi_qsd.9: msm_spi_process_transfer: SPI transaction timeout^M

Any help would be highly appreciated.

If any more code information is required please let me know.


texts: How to choose a spacer/stand-off to maintain electrical contact?

texts:
I have a situation where I want a stand-off to maintain electrical contact between the PCB and the chassis it's attached to.

My question is, what's the best material and finish for this application?

I see RAF has options of aluminum (unfinished), aluminum (clear iridite), stainless steel (unfinished), and stainless steel (chrome/nickel finish), which I would expect all are conductive surfaces.

Which one will have the best reliability?

Are there any material compatibility issues with any of these choices (like causing corrosion when in contact with the PCB)?

Are there better options I haven't mentioned?

Edit
Additional information: This system will have to pass rigorous environmental qualification including (IIRC) a few hundred hours in 85 C / 85% RH. It won't have to pass salt spray or any other corrosive chemical stresses.


texts: How can I work out if a cable can take a momentary current spike?

texts:
In this video here, almost 1000A is being run through a 10mm steel bar, and after a minute or so, it melts.

https://www.youtube.com/watch?v=YzZ3aJqmT-M

So in terms of charge, 60,000C applied for 1 minute destroys the conductor.

However, it would take a lot more current for shorter times. A good example being that if lightning struck such a bar, it would survive since lightning carries only 15C per flash on average.

Lightning averages 30,000A for a brief moment. So its carrying 30C per millisecond and discharges 15C then the flash lasts 0.5ms.

So what would be the smallest gauge cable that could sustain 30kA for 0.5ms? Is it possible to work this out mathematically, from Ω⋅m and the melting point? Do engineers do this or do they just buy a product that has been rated/tested?

Thanks.

Actually, it suddenly occurred to me that fuses must have been computed which led me to find the Preece equation and Onderdonk equation and this calculator.

http://www.cirris.com/learning-center/calculators/48-model-of-a-wire-fusing-in-free-air

I'll post the question anyway since it clearly has an answer.


texts: Why are most sensors designed to operate on a low voltage?

texts:
I took a look at sensor boards from Adafruit and Embeddio SNAP Boards and I've noticed that most of those boards use sensors that operate on a fairly low voltage of 3V3.

Is there a specific reason why most sensors are designed to operate on a low voltage?
If there is a specific advantage of operating it on 3V3 instead of 5V, then why not go even lower?


texts: How is the voltage regulator functioning in this vintage charging circuit?

texts:
Attached is a simplified diagram of my motorcycle's charging circuit. It has a standard 3-phase bridge rectifier circuit--simple enough.
I'm confused about two things:

How is the voltage regulator regulating the voltage here? Only one phase is connected to the regulator which appears only to have a ground.
How does this regulator function? All the example regulator circuits on the internet are either linear regulators or Zener diode reglators. This one seems to involve a thyristor and a diode.

1977 Suzuki GS400X charging circuit:


texts: Does adding a line impedance stabilisation network reduce the output of buck converter in simulation in LTSPICE?

texts: I have modelled a 48v to 12v buck converter in Ltspice.When I added a LISN the output reduced from 11v to 6.3v but EMI remains the same.Is it okay if output voltage is reduced?


texts: What are these coil components with three legs?

texts:
A couple of weeks ago I dissassembled a Panasonic DVD-recorder and salvage some components including these little guys. I tried to figure out what these are but cannot find a datasheet by searching for the numbers on these components.

I decide to crack on of them open (sse picture above) to see what's inside. There is a coil, looks like a decoupling coil. At the first place I thought this could be useful to seperate audio channels (ground-isolator) but the ground seems to be shared between coils. There are three legs, input, output and ground (I guess).

So what it is used for or what can it used for? Is there a datasheet of these things somewhere? The partnumbers are (numbers on the case of the component):

CO 82
CO 83
B1 06
B1 09
0 29


texts:
The dupe speaker I have here 8 \$\Omega\$  0.5W had it's magnet split from the coil/cone. So I did something thoughtless - attached the speaker magnet to the back of the other speaker (same specs).

I don't notice any difference except (this may be my imagination) it seems to sound a little louder.

Should attaching another magnet to the back of the speaker magnet make a difference?
What should attaching another magnet to the back of the speaker magnet do?


texts: what does this bulb need to work properly in this circuit?

texts:
This is the circuit, before it was working, but not anymore. I have an identical circuit and its ulb still working. I don't know where is the problem.

(https://i.stack.imgur.com/fPpZW.jpg)


texts: AT Commands to transmit data through TCP/IP stack with LTE network

texts:
I need to design an embedded sotfware that will drive a LTE cellular device (like u-Blox TOBY L2 Series) and its TCP/IP stack to transmit some data toward a distant server.

I'm waiting for the device to be delivered at work. For now, I use a GPRS device (u-Blox LEON series). Basically I perfom the following commands :

Configure PSD profile with AT+UPSD
Activate PSD profile with AT+UPSDA=0,3
Open socket with AT+USOCR=6
Connect to server IP with AT+USOCO=0,"xx.xxx.xx.xxx","pp" where xx is the IP address and pp is the port number
Write data with AT+USOWR

This is a very basic flowchart, I don't need very specific settings, just the default one. I do not configure a PDP context with AT+CGDCONT or anything else. Maybe the configuration of the PSD with AT+UPSD is enough with both GPRS and LTE network.

The problem is the following : Apparently there are some differences between GPRS/UMTS devices and LTE devices when it comes to set up the network configuration (PDP context for GPRS/UMTS devices and EPS for LTE). I have read quite everything about these data session setups but I don't manage to fully understand the differences.

So when I will switch from GPRS device (LEON) to LTE device (TOBY), what differences will occur in terms of setups and/or AT commands?


texts: Difference between a rectifier diode and signal diode

texts: Can somebody please explain to me the differences between a signal diode and rectifier diode in terms of their electrical characteristics and their Lissajous patterns? I know that Shockley's equation is used as the mathematical model for the general diode, but I can't seem to find any literature that sufficiently explains the characteristics of each type of diode. Any help would be welcomed.


texts: Reading from multiple channels using ADC10 and DTC

texts:
I am trying to read voltage values on two channels on eZ430-RF2500T, and transfer the result to the AP connected to a PC. Although I can successfully read from single channel, I am unable to do so using two channels.

Here is my code:

int * readPtr = (int *)0x200;
ADC10CTL1 = INCH_2 + CONSEQ_1;
ADC10CTL0 = REF2_5V + SREF_1 + ADC10SHT_2 + REFON + ADC10ON + ADC10IE;
for (countDown = 240; countDown > 0; countDown--); //delay to allow references to settle

ADC10AE0 |= 0x06; //110

ADC10DTC1 = 0x02;                         // 2 conversions
ADC10SA = 0x200;                        // Data buffer start, same as readPtr above

ADC10CTL0 |= ENC + ADC10SC; //Sampling and conversion start
while(!(ADC10CTL0 & ADC10IFG)); // wait till the block conversion is complete
ADC10CTL0 &= ~ADC10IFG; //reset ADC10IFG
//code for reading from readPtr

Please note that no interrupts are being used; results are read after the ADC10IFG bit is set.

I am not getting ANY results with this code. The 'reading from readPtr' part is never reached.

However, if I set ADC10DTC1 to 0x01, I can read from the highest ordered pin. I.e. given that ADC10DTC1 is 0x01, I can read from A2 if INCH_2 is selected, and from A1 if INCH_1 is selected.

I am unable to get conversions for both A2 and A1, though.

Any help will be greatly appreciated.

Thanks!

EDIT: I am now trying to make this interrupt based. Not sure how to code it, though.


texts: I am trying to learn link utilization factor in data communication but can't find the actual definition of it.Can anyone give me an accurate definition of link utilization factor with the formula??


texts:
How can I get very high speed from a FTDI chip?

I have tried with FT232RL with UART in 230.4kbps but I want much more than this. Will I need some other different speed?


texts:
What does #high(434)  actually mean I know it is some value but how do you compute the value
when I debug the command mov r7,#high(434) I get 1 in register 7
why ?


texts: Why do electrons cross the collector-base junction and does current flow between collector and emitter?

texts:
If the base-emitter junction of an NPN transistor is forward biased, electrons flow from emitter to base. If the collector-base junction is reverse biased, how can they cross it?
If I connect the emitter to negative and collector to positive terminal of a battery and don't connect any battery to base-emitter junction, what would happen? Will electrons cross the emitter-base junction? What will stop them?


texts: How do I tell if my device qualifies for FCC exemption

texts:
According to the FCC:

  The following devices are subject only to the general conditions of operation in §§15.5 and 15.29 and are exempt from the specific technical standards and other requirements contained in this part. The operator of the exempted device shall be required to stop operating the device upon a finding by the Commission or its representative that the device is causing harmful interference. Operation shall not resume until the condition causing the harmful interference has been corrected. Although not mandatory, it is strongly recommended that the manufacturer of an exempted device endeavor to have the device meet the specific technical standards in this part.

And one of the following items is:

  (h) Digital devices in which both the highest frequency generated and the highest frequency used are less than 1.705 MHz and which do not operate from the AC power lines or contain provisions for operation while connected to the AC power lines. Digital devices that include, or make provision for the use of, battery eliminators, AC adaptors or battery chargers which permit operation while charging or that connect to the AC power lines indirectly, obtaining their power through another device which is connected to the AC power lines, do not fall under this exemption.

Obviously the hairy part is the "highest frequency generated" issue.

Is there any way to tell if a device can qualify for this exemption in light of this?  Is there any tests I can/should preform?  Should I just forget it and get a full blown FCC test?

Example:

I have a 32 kHz 5v square wave (at the worst case scenario).


texts: How to change speed of dc motor using potentiometer?

texts:
I want to change the speed of a DC motor(12V,2000RPM) using a pot and operate a table fan(where I've replaced its AC motor with DC).Now the problem is I get a regulated output at o/p of 7812 but not after connecting the pot(10k)!
Need ua help guys!
Thanks!


texts:
Should I be asking this on Hardware Recommendations? That is – do I need some sort of test device? Or, hopefully, I can just my laptop …

I am developing a vending machine controller, as a hobby project.

I want to brush up my Ada skills and will use an Onion Omega2. Some details of the GPIO can be found at https://docs.onion.io/omega2-docs/using-gpios.html

My Ada is rusty, I am new to the processor and I won’t have the hardware for a while yet – what could possibly go wrong? :-)

Eventually, I will be using he GPIO to read from a numerical keyboard and to drive motors.

Questions: what’s the simplest, cheapest easiest way to test my code, to make sure that I read/write GPIO? I am fine with software, which is my day job, but lousy with hardware, so please don’t ask me to do any soldering.

Right now I want to make some very quick checks as to whether I can interact with GPIO, UART & WiFI from Ada, or whether just to fall back on C, for which more example code is available.


texts:
Any suggestion on how to build home-brew rain sensor for car? I've found one which shows this particular sensor is just pcb plate (or maybe there something on it I can't see).

What is the difference between built in sensors and home-brew ones like above? I would like to make something which is very close to built-in. Other question is where to place it?

Later I can connect it to AVR and collect data.


texts:
I am looking for a 5V power source for some LEDs that I want to put in my XBox 360 slim.
I have soldered them to 5V on the USB ports, but they have constant power, and I only want power when the console is on.  Any suggestions?


texts: High-efficiency, battery powered high-side load driver

texts:
I need to drive a resistive load with low-voltage and relatively high current, in a battery powered system. Since I need my load to be grounded, I would like to use a push-pull or high-side drive. I am oriented towards maximixing simplicity over cost, and therefore I always choose off-the-shelf and ready-to-use solutions when available. I will drive my load from a 3.3V logic, with a square PWM signal and a carrier frequency of 500 Hz. The system is powered from a 3.7V battery, with the voltage varying among 2.7 to 4.2V. Obviously, the 3.3V voltage line to the microcontroller is stabilized with a buck-boost converter. The load will instead drain power directly from the battery, to avoid efficiency losses. I had some difficulties finding low-voltage half bridge mosfet drivers (except from the MAX15492, which unfortunately has no stock) and I focused in high-side mosfet drivers instead. After a long search, I found the LTC1981, and I drew the circuit below

simulate this circuit – Schematic created using CircuitLab
I studied the datasheet throughly but I still have some doubts: the VCC power voltage will vary among 4.2V when the battery is fully charged, to 2.7V when it is depleted. On the other side the PWM signal to SHDN will always be between 3.3V and GND. The datasheet clearly states that this is possible, but I wonder if I missed anything? Moreover, I am trying to select a mosfet with lowest possible Rdson, low Voltage threshold and faily low gate input capacitance. I need to switch at 500 Hz, which is not a high frequency, but I really want to minimize losses and save battery. Did I choose the right mosfet (DMN1008UFDF)?


texts: Configuration of AC Voltage Source for Sawtooth Wave

texts:
I have a little problem with circuit configuration as you can see below.
Every Voltage Source has configuration - 120V/10 kHz
And 1,3,5,7,9 - 0 Deg, 2,4,6,8,10 - 180 Deg

I need to change voltage on every source in such way that I will see Sawtooth Wave.

I tried several different ways, for example, I had changed all votage like 120,240,360,480,600,720,840,960,1080,1200

But it did not help me.

Can somebody give to me some advice or hint?

Thanks

UPD1:

So as I understand the frequencies of sawtooth wave is depends of harmonic's number.
I had changed frequencies: 10,20,30,40,50,60,70,80,90,100kHz
and I got something strange on oscilloscope:

Looks like I made new mistake

UPD2:
Finally everything looks almost perfect. I divide voltage by number harmonic

Thanks everybody for the help!!!!


texts: Designing a band pass filter using given specifications

texts:
I am trying to design a band pass filter using the below emitter follower circuit :

The Specifications for the filter include : $$ Z_{in} = 16k\Omega
\\ \text{Current gain} = 35dB
\\ \text{3dB bandwidth} = 418kHz$$
I am allowed to vary \$R_2 , V_{cc}, C_{1} , C_{2}\$ to achieve my specification.
I used the T-model of the amplifier and tried to solve for the collector current using the equation
$$A_{i} = \frac{(\beta+1).Z_{in}}{r_{\pi}}$$
where $$r_{\pi} = \frac{V_{T}.\beta}{I_{c}}$$
Using \$\beta = 381.7 , V_{T} = 26mV \; \text{,i am getting} \; I_{c} = 91\mu A\$
Using the above value of \$r_{\pi}\$ , I Plug it in :
$$ \frac{1}{Z_{in}} = \frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{r_{\pi}}$$
Putting the value of \$R_{1}\; \text{and}\; r_{\pi} \;\text{gives me}\; R_{2} = 28k\Omega\$
However , when I do a small signal ac analysis in Ltspice using the value found for \$R_{2}\$ and a sinusoid of frequency 1kHz for a duration of 5ms  and \$V_{cc} = 12\$ I am getting the collector current in picoamperes.
What mistake have I actually made in finding \$R_{2}\$ and what procedure should be followed to meet the required specifications ?


texts: DMM: auto-ranging and capturing transient current waveforms

texts:
This might be a follow-up/related question to the one previously asked on StackExchange here.

My question is: in an auto-ranging DMM, would I be able to capture transient current profiles - for example using the image below from TI AN092 as reference, if a BLE SOC is going from ~1uA in hibernate mode to ~30mA in transmission mode, within a period of 10s of microseconds, and the 30mA spike lasts for 10s of microseconds itself, is this something the DMM would be able to capture with auto-ranging?

The TI App-Note refers to using a scope to capture the current profile. But would I be able to capture this using a DMM?

What trade-off in terms of accuracy vs capturing transient spikes like the one above, should one be aware of when trying to capture a current profile similar to the one above, using a DMM in auto-range mode?


texts:
I have built a 12/24V 47A DC Power supply following this guide.  It works well for running my battery chargers, but I'd like to make it a CCCV supply from it for my projects.

What would it take to do this?  I've been looking around, but everything I find is either for a high voltage supply or is only a few amps.


texts: Waking ESP8266 from Deep Sleep Using a Motion Detector

texts:
I'm building a project using Adafruit Feather HUZZAH ESP8266 and PIR Motion Sensor.  I have everything working, but I'm trying to reduce power consumption as I'm running it off of a 3.7v/600mA battery.  The suggestion I found online is to put the ESP8266 into deep sleep mode.  This works fine, but I would like to wake it up when motion is detected by the motion detector.

The motion detector is powered independently from the battery and when motion is detected, it produces a HIGH voltage (~3.7V).  The way to wake ESP8266 up is via the CHPD pin #3. However, when the ESP8266 is asleep it produces a HIGH voltage on that pin and you need to pull it to ground to wake it up.  I'm trying to find a trick to translate the HIGH signal coming off of the motion sensor into a LOW voltage for the CHPD pin.

Thank you,


texts: Understanding Resistor Values in TTL NOT Gate

texts:
I've been teaching myself electronics and a current approach I am taking, is to be able to describe the purpose of every element in the standard TTL NOT gate:

Circuit lab TTL NOT Gate

At this point I understand the purpose of each of the transistors, the diode, and how the 130 ohm resistor supports the desired fanout. I'm still trying to figure out the other resistors. So for the 4 kΩ R1, 1.6 kΩ R2, and 1 kΩ R4, I'm trying to understand why these values (versus, say, 5 kΩ, 2 kΩ, and 1.6 kΩ respectively, for example).

So I have two specific questions:

Why would you choose those specific resistor values (if you were designing this circuit)?
If the values are chosen to support specifications (e.g. a particular sink current amount on the input), why would that specification be desirable in the first place?

Any help will be appreciated. Thanks!


texts:
I'm having trouble with this problem. Suppose the machine was at rest, and a weight of 5 kg was suspended from a horizontal bar of length 80 cm attached to the shaft.
What current must be applied to the armature to keep the arm horizontal?
I think I need an expression of the torsions equal to 0. but not sure how to proceed.


texts:
Ohm's law is valid for metals, but is it valid for semiconductors? Does it work there?

I am not talking about a PN junction here.

If I have a block of silicon and pass voltage across it, will I see current flowing, in accordance with Ohm's law?


texts: Is it possible to use two HM-10 on two Arduinos for bidirectional Bluetooth communication?

texts:
I am thinking about using the HM-10, or some other bluetooth module on two Arduino boards for Bluetooth communication.

What I want is to be able to send and recieve data from a single Arduino board. For example, if D2 is HIGH on Arduino A, HM-10A will transmit a signal to HM-10 B, telling Arduino B a button is pressed. And if a D2 on Arduino B is HIGH, HM-10B will transmit data to HM-10A, telling Arduino A a button is pressed.

If it is not possible with the HM-10, are there any other development boards that are capable of this task?


texts: Avoiding shorts when switching between bus lines with a mechanical switch

texts:
I've designed a circuit to choose between two 8-bit digital buses. I'm taking advantage of the fact that the 74AC540/541 chips have tristate outputs, so can enter into high impedance state to allow the other chip to drive the bus without creating a short.

I'm using the BYPASS and !BYPASS digital lines to enable and disable each bus. These lines are controlled by a DPST mechanical switch and pull-up resistors:

I'm worried about the switching operation: as the switch is toggled, I cannot guarantee that the two buffers will not be on at the same time and therefore, depending on their inputs, short their outputs together. For example, pin 2 of N2A could be LOW, causing its (inverted) output to be HIGH, whilst pin 2 on N8A might be LOW, causing its (non-inverted) output to be LOW, and creating a short between those two outputs. I imagine that switching operations with these chips are not instantaneous, and might not be matched, so there could be a situation where both chips are momentarily on during the switching operation (even with a break-before-make switch - I think).

How can I avoid shorts during this switching operation?


texts:
I am confused with how TDQS and TDQS# pins be driven in verilog syntax ?
I suppose these two pins are of inout nature which already mandates the usage of high-Z for in direction.


texts: How can I create signal interference in a circuit?

texts:
I understand that this is counter intuitive but, as an experiment I want to create interference in a circuit.
I want to expose an AC sinusoidal signal to a second sinusoidal signal. This will cause some type of interference and produce a resultant (third), output voltage signal across a passive element (such as a resistor) as shown at the bottom of the image below.

If I wanted to do something like this, what sort of circuit would I need to construct? I assume I would need to use two functions generators, how would they need to be set up?


texts:
I have two inputs for my LM393P comparator (https://www.rcscomponents.kiev.ua/datasheets/texas_instruments-lm393p-datasheet.pdf). I have checked these two inputs with the analog inputs with my Arduino Uno and they are typically at ~0.5v. I have 5v from the Arduino running to Vcc of the comparator and the ground of the comparator running to the Arduino ground. I am using input 1 of the comparator, having checked that I am using the correct input and output ports. The output port is connected to the Digital port 10 of the Arduino (set to "input") with a 1k resistor in between.

One thing I am concerned about, is that the marking on the comparator isn't the same as in the datasheet. The comparator does note it is the LM393P however, but I might have mistaken which side was "up". I believe it to be the side of the small circular indentation now.

The readings almost always return 1, but periodically return 0. These periodic readings seem to be separated with a almost fixed timing (~0.5s).

Having the comparator been placed in reverse, should I expect it to be broken or is there possibly another cause to my problem?

I'm not sure of a website or application in which I can draw schematics easily, as I am a beginner to electronics, but I'm willing to sketch a schematic if that's of use.

Update

Just ordered some extra LM393's. I will keep this question open and check whether a new IC will fix the problem.

Update

Made some new observations. I've got the LM393N's in the mail, and they show the same scenario. If I connect a led to the output, I see a faint light with a 100 Ohm resistor, while the same led on 5V input shows full brightness. Wiring digital ports to + and - inputs of the comparator and writing low and high, doesn't do anything either. I would expect the led to change in brightness. Is it required to use all the ports on the 393 comparator for it to work?
To add some info, originally I was using photodiodes to compare the outputs of two of them and send the result to the Arduino.

Update

I've tried replacing some of the connections to no avail.

Update

I got the comparator working! I accidentally mistook delay() for being seconds, but it is instead milliseconds. Writing with the digital ports, high and low, alternated by a second, I got the comparator to play nice.
I placed a 1K resistor between Vcc and output. Now to get it to work with my photodiodes..

Update

It now works with my photodiodes, but the accuracy and responsiveness are very low.


texts:
I've read on a Littelfuse page that I2T of a fuse is a measure of the let-through energy. The units of amps^2*resistance is power. Multiply that by time and you have energy. But in a I^2*T rating of a fuse, where is the R? Is 1ohm implied?

Link: https://www.littelfuse.com/~/media/electronics/product_catalogs/littelfuse_fuseology_selection_guide.pdf.pdf

I'm trying to predict whether my combination of protection devices will operate as intended: I want the fuse to open and nothing else to be damaged. My circuit is a 840V pulse into a 300uH inductor. On the otherside of the inductor is a 3A fuse (bel 0ADBP3000-RE), with a littefuse sidactor to ground (P3100EALRP1). The load in parallel with the sidactor is the input to another power supply. The fault is is 840V overvoltage pulse.

So basically I'm trying to calculate or plot the power into the sidactor, ideally so it survives until the fuse opens.


texts: How to build a 4 to 16 decoder using ONLY TWO 2 to 4 decoders?

texts:
Help please, I am new to circuits and decoders and I need some serious help.

How to build a 4x16 decoder using ONLY two 2x4 decoders?

Following the steps we took in the lecture, we are supposed to build a 4x16 decoder. So here taking k to be 4, k is even, so we will have \$2^k\$ so \$2^4 = 16\$ AND gates & 2 decoders each of size \$2^{k/2}\$ so \$2^2 = 4\$.

So we have 16 AND gates & two 2x4 decoders. Each 2x4 decoder has 4 AND gates so we have 8 AND gates that should be connected to the 16 AND gates, how do I do that?


texts: What type of transformer should I purchase?

texts:
I am trying to design an arduino board with an integrated power transformer that powers the board after off-course stepping down the voltage and then rectifying it to generate a 5V stable output. I have found this website where I can get cheap transformers:-
https://www.aliexpress.com/store/1459305

If you open the link, you will find that on the left side the type of the transformer is mentioned like EE, EP, ETD, RM..etc etc. My problem is that I cannot decide which type is suitable for my application. I just have simple theoretical knowledge about transformers. I just want to use the transformer to step down 220V AC (single phase 50Hz) to 9V or 12V AC which I will then rectify and feed to a 7805 ic, that finally powers the atmega328p microcontroller.

I did my own research and have only come to know that EF means Earth Fault type Transformer and have no idea what it means. So please provide me with some information regarding the types of these transformers and please suggest which one is best for my application.Here you can see the types being highlighted by the red box:-


texts: ATmega328P running on 3.3V using a CH340G as serial to USB interface

texts:
I'm trying to use a CH340G chip with an ATmega328P that is running on 3.3V to have a simple serial to USB interface. The available datasheets for this chip seem to be very minimal so I've tried finding out more in forum posts.
Some links provide more information but it's not completely clear:

http://fobit.blogspot.com/2014/11/ch340g-in-eagle.html
http://actrl.cz/blog/index.php/2016/arduino-nano-ch340-schematics-and-details/
https://forum.arduino.cc/index.php?topic=409415.0

When comparing the usage of CH340G with the popular FTDI FT232RL one thing seems peculiar:
In those user-provided example schematics the Tx pin of the CH340G is connected to the Tx pin of the ATmega328P and the Rx pin to Rx, when for FT232RL they would be crossed.

The schematic supplied by the fobit blog suggests:

Atmega328P Tx -> CH340G Tx
Atmega328P Rx -> CH340G Rx

CH340G D+ -> USB connector D+
CH340G D- -> USB connector D-

Is this correct?
Even though using a 3.3V 1117 voltage regulator for VCC, wouldn't one need additional resistors on the D+ and D- to drop the USB voltage of 5V to 3.3V on these data lines as well? If so, which value has to be used as it's unclear how much current flows on the data lines?
Neither the user supplied 3.3V CH340G schematic nor the datasheet mention that.

A minimal translated datasheet can be found here and some relevant info is on page 4:
http://www.handsontec.com/dataspecs/ch340g.pdf

A schematic for a 3.3V setup found on http://fobit.blogspot.com/2014/11/ch340g-in-eagle.html
http://i.imgur.com/vUIm3SF.png

Thank you in advance.


texts:
This is a newbie question. Can someone confirm: a resistor on its own is useless. True or false? I mean, I can't do anything with a resistor alone, or is there something that can be done with it?

Sorry, I know the question is too newbie.


texts: Why do you curl the wire when making electromagnets?

texts: What is the scientific explanation for adding turns in the wire when making an electromagnet? If two wires had the same length - would the one with several turns be a stronger magnet than the straight wire with no turns?


texts: How to know where to put the threshold signal of an op-amp comparator

texts:
I am really confused on where to place my signals on amp. So basically what I want is a comparator that when a Vsignal exceeds Vthreshold the output would read HIGH on the GPIO. My Op-amp is TLV7041 open-drain type op amp.

simulate this circuit – Schematic created using CircuitLab
Here is my attempt at the circuit, since my op-amp is an open-drain type makes a bit tricky for me since an "ON" will read a 0v on my GPIO. When Vsignal is below Vthres the op amp should be "ON" so that the GPIO would read 0v and when Vsignal is above Vthres the op amp should be "OFF" so that the GPIO would read 5V. I am having a hard time grasping the concept of which of the inputs is the typical reference


texts: Why should I use a resistor for a 3.3v-consuming led?

texts:
The white LED I bought consumes 3.3v. My circuit is fed with two AA bateries (total: 3v). There is no additional stuff here. When I inteded the circuit, was just a push-button which closed the circuit and the led was turned on. The guy who assisted me, said we should use a resistance before the led.

Original circuit: Two AA -> push-button -> LED -> closing to the two AA.

Final circuit: Two AA -> pb -> resistance -> LED -> closing to the two AA.

My question comes since the batteries voltage does not pass what the LED can hold (unless I'm wrong regarding the numbers here!). So: What am I missing here?


texts: Trouble in understanding current flow in this three phase DC-AC inverter circuit

texts:
Shown in the figure is one of the six steps of a 3-phase voltage source inverter where switches 1,5,6 are closed. The tutorial that I learnt this concept from draws the following equivalent circuit of a voltage source inverter connected to a 3-phase load.

I'm having trouble understanding how current flows in loops in this drawing. Does current flow from the battery to the 3 windings and then back to the negative terminal of the DC source? Or does the current flow to the neutral that is grounded?

What exactly is the neutral point in this case? Is it just a reference point to measure voltage or does it have an extended wire that is connected somewhere else in the circuit?

If the neutral point is just a reference point, then the three phase circuit gets of any 1 switching state gets reduced to an equivalent circuit of resistors in series and parallel. For example, the equivalent circuit drawn when switches 1,5,6 are on doesn't seem to be like an AC generating circuit. Seems just like two resistors in parallel with the combination in series to a third resistance. So how is this combination of resistors able to generate a sinusoidal waveform?


texts:
I’m new to soldering and this is my first time soldering SMD components on to a PCB I ordered online.

When I solder the components there are what seems to me burn marks from the iron touching the board..

What are these and what causes them? Aside from making the board look ugly, are these okay?


texts: Is a circuit simulation package available with models from multiple vendors?

texts: I need to simulate a filter that will be used with a DAC. I need to model noise, accuracy, and drift to calculate ENOB and identify tradeoffs. I have used LTSpice for my modeling needs for the last 10 years. My company is willing to buy a  more advanced tool for me to use, but I have no experience creating my own models. Most of the models available from Analog Devices and Texas Instruments are for their own SPICE programs (LTSpice and TINA-TI). Is there a popular SPICE package on the market that includes lots of parts models from multiple vendors?


texts: Trying to create a formula to estimate battery life for varied devices

texts:
I'm shopping for a AC Power brick like.  Sometimes they're rated in mAh like this one and other times they're rated in mWh like this one
To try to estimate the how long I can run a 10 watt LED wall lamp I'm doing this:
mAh Formula
mAh_of_battery_capacity / ((watt_of_lamp/120v)*1000)
So the calculation would be 60000 / ((10/120)*1000) or 720 hours.  That seems really high.
(and yes I know batteries don't go to zero so I should have a .9 in there).  But on a high-level is this correct?
mWh Formula
Is it just ((mWh_of_battery_capacity / 1000) / watt_of_device ??
Or (58830/1000) / 10 = 5.8 hours.  That seems really low.  Their ad says they can run a MacBook Pro for 7.9 hours which takes 10-30 watts of power.
Appreciate any help correcting these formulas.


texts: Is it possible to make distinction between the touch of a bare hand and an aluminum can?

texts:
Capacitive sensing can easily detect human touch, but my case is to detect an aluminum can touching a surface equiped with some kind of sensor.

Aluminum's electrical conductivity and almost non-magnetic properties make this quite difficult.

There's any practical alternative to sense aluminum touching another surface?


texts: Atmega 8 is not programming once it is set to external crystal?

texts:
I am using Asim Khan's Parallel port Programmer to program my AVR ATmega8 controller. The Problem is when I changes fuse bits to external high speed crystal, then the next time programmer does not detects the programmer. I am really frustrated to figure out what would be the problem. Can any one helps me to locate the problem?
Thanks in advance


texts: How to set up clock for the STM32 Nucleo-64 with libopencm3/rtos

texts:
I was using this code from github on a blue pill. Now I would like to adapt it for STM32F401 on a Nucleo-64 board. I tried changing the GPIO to A7 and attaching an led (which lit up when I attached it to 3.3v) to GPIO A7 but it dit not seem to work.

I think the problem might be in this step:

rcc_clock_setup_in_hse_8mhz_out_72mhz();   // Use this for "blue pill"

because afaik this is the only step specific to the blue pill.

The blue pill has an 8MHz oscillator and according to this, the Nucleo has a 32.768 kHz crystal oscillator.

Can someone please tell me how to modify this line?

I am using arm-none-eabi-gdb and make to upload code to Nucleo, as I was with blue pill.

TIA


texts:
I'm using a Banana Pi M3 with an ARM cortex-A7.
I want to perform a task in a cycle with a fixed period with no delays and I was wandering if I could use an interrupt for that.
Does this processor even have a cycle interrupt? If so, how can I use it?

Thanks


texts:
Is it fine to charge a pile of 8 2 Ah AA NiMH @ 11.6 V 0.5 A serially? They are from the same packaging and were bought only for use as an 8x pack - they were not used for anything else. Im not sure whether NiMHs demand balancing like LiPo.

Is it possible for a certain cell to have an abnormally high voltage - even surpassing its rated voltage while other serial cells have abnormally low voltages across them?


texts:
I am trying to sniff a serial communication between two devices. One of them sends a command (6 bytes + 2 bytes CRC),
the other one responds (4 bytes + 2 bytes CRC). My computer monitors the exchange with an USB-serial converter and PuTTY.
I have access to the source code of both devices, and the baud rate seems to be set to 57600.

However two things are quite astonishing :

In PuTTY, I must set the baud rate to 57100 to "get the bytes right". At 57600, I see gibberish.
There seems to be "junk" in the response once in a while (see picture below).

I don't know what could be causing this, anyone has an idea ?


texts:
We have the following diode circuit.We have found when the diode is on and off.Now the teacher gave an extra question.What is the ouput Vo (represented in a graph) when we have an input of

a) \$V_i = 100 sin(wt)\$

b) \$V_i = 150 sin(wt)\$

She then solved this exercise .I see the graphs but I dont understand them? Can you please explain them to me?
Here is the solved exercise (Excuse the sloppy drawing)

Here are respectively graph a) and b)


texts: I need to detect when an irrigation head is functioning, non-invasive. The heads are the Toro brand and when activated a cylindrical shaft extends several inches above ground. This shaft is a non-ferrous metal, I assume to be polished aluminum. It measures 1.75" in diameter. My thoughts are to wind a coil about 2" in diameter of say, 50 turns of # 22 awg. This coil will sit slightly above and centered with the head. I will energize the coil with a square wave derived from a pic chip at say 1khz. Will I be able to detect a change in the applied waveform when the head's shaft enters the coil? Does the core (head shaft) need to be of a ferrous material? Is there a formula I can use to calculate the coil parameters?


texts: Why does reflection coefficient phase depend on position along a T line?

texts:
I'm in an intro electromagnetics class. It makes sense to me that reflection coefficient at the load has an imaginary component, because I am thinking of it like "the reflected wave is some percentage of the amplitude of the incident wave, and it's shifted by some constant phase shift".
However I cannot understand why reflection coefficient along the T-line (i.e. reflection coefficient as a function of distance) has a changing phase angle. I'm thinking if you freeze-frame a T line at some moment in time and look at the voltage across the length of the T line, the reflected wave and the incident wave may be offset, but the offset will be the same for the entire length of the T line, because the two waves have the same frequency. I graphed this to hopefully help explain my line of thinking.

So why does the angle of the reflection coefficient depend on where you are on the T line? I would love a graphical explanation, I feel like I am getting caught in the math and not understanding what is really going on.


texts: Sharing Clock and Data for 74HC595 and CD4021B Shift Registers?

texts:
Can output shift registers (74HC595) and input shift registers (CD4021B) share the same clock and data lines on Arduino using SPI, with different latch pins "activating" either chain for input or output shifting?

I think this should work, but don't yet have all the parts I need to prototype it.  I already have all that parts for an solution that does NOT work, and am trying to skip that "opps, this won't work" step. :-)

I am currently using SPI from an Arduino Pro Micro (5v) to drive a chain of 74HC595 shift registers for a multiplexed bank of 7 segment display boards.  Each "Display Board" has two 74HC595's to drive a set of displays, and is connected via ribbon cable to the next (identical) board, which is the next display in a series of chained display boards.  This is built and working great.  I use a loop of the following to write out data to the 74HC595 shift registers.

SPI.transfer(myByteOut);

I would like to add an IR sensor (Vishay TSOP75356WTR) to each board.  The Arduino would be able to detect if the IR sensor on each chained board is high or low.

My plan is to expand the existing display board setup by adding a parallel chain of input shift registers (CD4021B?) to shift back to the Arduino the IR sensor readings from each board.  This would be done via a loop of

myByteIn = SPI.transfer(0);

Can one chain of 74HC595's, and one chain of CD4021B's share the same data and clock lines, using different "latch" pins to toggle between my input (CD4021B) reading and my output (74HC595) writing?

High speed is required, and Arduino only has one hardware based high speed pair, so I'd need to share the clock and data pins.  Will that work?  Anything else wrong with my plan?


texts:
What is the recommended AWG size for connecting a USB male connector?
The link from Instructables.com below uses only a spare LAN cable and no mention of the size:
http://www.instructables.com/id/Creating-you-own-USB-cables/


texts: RS-485 Connecting 100 devices - Avoid GND Loop

texts:
I'm new to community and it's my first question, so please forgive me for mistakes I could do referring to adding pictures and descriptions.
I plan to use 100 devices and connect them via RS-485 in half duplex manner as it can be seen in below picture. Each node will need max 150 mA and I plan to use 12V 20A power supply connected to 220V AC main. Termination resistors will be added to ends.

I searched for problems I might end up with RS-485 communication and saw that ground loops might be problematic. In that sense, implementing specific ground for communication and isolation is offered as it can be seen below picture;

However all of examples I could find related to ground loop problems in RS-485 mentions about ground differences according to different power supplies connected to building mains which are far away and might have different potentials although power supply reference is earth. Connecting grounds might create ground loops and interfere with communication signals. Large current might created in ground loop and might damage the circuit. If grounds are not connected, than ground potentials might be a lot different and transceiver could not handle ground potential gap.
In my case I will use single supply and connect all devices in daisy chain. And in worst case total of 15A will be used and I am afraid this might also create ground differences between devices. Would this will create ground loop like in the case with different power supply? I have no experience about transmission line but in my PCB designs I try to seperate digital grounds and analog grounds and also seperate high current grounds and connect them at one point to avoid ground loops. By the way, total distance (device 1 to 100) will be no more than 200 meters and baud rate is low (9600). I know isolation is the best way but from cost perspective this setup is my preferred one if there will be no problems.
Also I would like to ask about fail-safe pull up and pull down resistors connected to A and B lines. Having them only at the master device is enough or should I have them at every device?
Thanks for replies,
Mert


texts: How to calculate fuse size for primary coil?

texts:
How do you calculate fuse size for primary coil? I have an 230V AC to 18V DC.

What are the steps please?


texts: Why is Pulse Code Modulation called 'modulation' and not 'conversion'?

texts:
Since all that a pcm accomplishes is analog to digital conversion, why is it called a modulation technique?

There is a message signal but no carrier. According to my knowledge, modulation requires a carrier.


texts: Switch ON/OFF Voltage Regulator using a Microcontroller

texts:
I am trying to control (Turn ON/OFF) a Voltage Regulator which has an enable pin by connecting it to a digital pin of a micro-controller. I need help to find the resistor values (R1 and R2) to be used for the interfacing. Please find my circuit below.

simulate this circuit – Schematic created using CircuitLab
Specifications
The microcontroller works on 3.3V and the GPIO1 current is limited to 4mA. The Voltage Regulator enable pin logic high minimum is 2.4V, logic low maximum is 0.8V and the max current is 750uA
LDO
Datasheet - https://www.mouser.in/datasheet/2/268/MIC2915x_30x_50x_75x_High_Current_Low_Dropout_Regu-1889172.pdf
I am beginner and would appreciate any help to understand other challenges for this interfacing.


texts: At what point do we no longer need a diode in series with a solar panel to prevent discharge of a battery through the panel? Is it x amount of volts difference between peak power voltage and cell voltage? If so what's x?


texts:
I've had this question for a while.

Assume you have an otherwise perfect op-amp with a gain-bandwidth product of 5 MHz. You input a signal of 50mVp-p and amplify it by 10x. This limits your bandwidth to 500 kHz. Now, say you stack another op-amp on the output and configure that as a 10x amplifier. Your overall bandwidth is 500 kHz but you have amplified by 100x, so your GBWP is 50 MHz. Where is the flaw in this logic?


texts: Is double-sided mounting still possible with the latest packages?

texts:
When I think of packages like some DFN

or 0201 resistors I wonder where they would place glue dots. The UDFN pictured is 1.2mm x 1mm. And glue dots on 0.5mm pitch WLP

seem completely out.
Is it still possible to fix parts at the bottom of a PCB for soldering?


texts:
[EDIT] I'm going to give mesh analysis another go, and see where that gets me.
[DOUBLE EDIT] Mesh analysis didn't get me anywhere :(

Im tearing my hair out over this problem, so any help would be greatly appreciated.

Im solving the circuit with nodal analysis, and following the steps of:
1: Ground node equation

2: Voltage source and current source equations

3: Equations for each resistor

4: KCL at each node apart from the ground node

5: Substituting resistor equations into the KCL equations and solving for the node voltages

6: Solve for branch currents

7: Find power consumed or supplied

The problem is, i get to step 5, find a node voltage, but apparently it's the wrong answer. It doesn't match any of the answers supplied by the teacher (it's a practice multiple choice exam).

Attached is my working, with a picture of the circuit.

I get to a voltage for node B (circled in red), however, when I sub this in to find the voltage at node A, i get the wrong answer (12.8).

Please please please tell me what I am doing wrong.

Thank you in advance


texts:
I am just soldering my first ever TSSOP-16, on my first perfect toner-transfer board, and when I am tinning the TSSOP pads some of them are lifting up.  Which of these is most likely responsible?

The soldering iron is too hot (it's an uncontrollable 30w)
The board is inferior (it was cheap stuff from Maplin)
I have Parkinson's (Apologies to anyone who has a relative / friend with Parkinson's - no offense intended)
Something I haven't thought of?
All of the above

It's not the end of the world - the pads have remained pretty much in position and I have successfully soldered in the TSSOP chip, but it would be nice to know why it happened so I can stop it happening the next time.


texts: Does increasing AWG increase temperature?

texts:
My laptop charger connector broke, so I bought a new connector. However, I noticed that the new connector's wires were thinner than that of the existing charger. The laptop charges, but the charger brick is getting very hot. Make note that I did not open up the brick, but rather just soldered the old wire to the existing wire.

EDIT: The charger does not get hot when it is plugged into the outlet and NOT plugged into the laptop, so essentially without a load it doesn't get hot. This is completely normal, but I suppose it suggests there are not shorts in my soldering work.


texts:
I am pretty much a beginner in these parts, so can you help me?
Does the LM317 take ANY voltage and convert it into the adjusted one?
By "ANY" I mean that is in its voltage range, etc.


texts:
Well I have broken pcb and it has a PIC16f676 on it. PCB Not working very well. I want to replace it with new pic16f676 but I cant read data from on board PIC. it ruturns "0000" in everywhere. I've added image of TL866 buffer screen after reading process. it looks I cant read and it looks protected. because even if pic is empty, it will return "3FFF" not "0000". Actually I dont need to see code, may be it wont be legal. Just I want to replace the pic with new one. Also this PCB board is very old, I try to find owner of this board. but I cant find him/her.
this is config screen of 18f452 and it looks same problem but there is not code protected from docs page 201


texts: What would happen if a rotatable ferromagnetic rod were placed beside a magnet?

texts:
If one were to place a rotatable shaft (green circle), made of plastic with ferromagnetic material (grey circles inside green circle), right beside an electromagnet, what would happen?  I am trying to exclude the case where the shaft has magnets on it as a thought experiment.

For instance if the green circle were the rotatable shaft in this picture, would the shaft rotate due to the magnetic force?

Alternatively, is there an orientation that will cause the shaft to rotate?  This would seem to be a perpetual motion machine (which doesn't make sense).


texts: Should I use a Micro:bit or Arduino or something else?

texts:
I am creating a board with the following components:
Inputs:
Momentary button
Reed switch
Rotary Encoder with 24 detents
Output:
Bluetooth
The idea is to have it connect to a mobile device, such as an iPhone or iPad, and transmit the data to an application that I'm writing.
All's going well with my prototype. I would want to have someone create a proper PCB that could go into some sort of commercial production.
The question I have is whether I should be using a Micro:bit, Arduino or something else to piece my prototype together.
I already have a Micro:bit, but the way the Bluetooth connects doesn't seem like a good representation of my final product. I'm not sure how much of a problem this is, but would the Bluetooth connection from the Arduino be the same as something from a custom PCB?
Is it worth the effort to do it with an Arduino instead of the Micro:bit?


texts:
I'm just starting a project to build a universal Engineer's Remote Control Unit [EG. able to send the Panasonic 0xF2 code, etc.].

I have seen that IR LEDs come with (at least) three distinctly different coloured lenses, namely "Crystal Clear", "Blue" and "Black" ...Using Google, I can find no information about the difference made by the colour of the lens.

So my question is: Why do Infrared LEDs come with different coloured lenses?


texts: Does capacitance of pcb's copper used in conjunction with capacitance proximity sensor (analog) rises or lowers when the obstacle get closer?


texts:
I'm rather unexperienced on the field of microcontrollers, I come from a Java background so the question might seem a bit noob but I didn't find much information on this.

So is it possible to debug an STM32F4 board via bluetooth (using eclipse or some othe IDE)? And if so could you send me some links that might help? We're building a robotic car controlled by a discovery board and debugging using an USB cable is not really an option if we don't want to disassemble the whole stuff every time something goes wrong. Hence this would really come in handy. So any help is appreciated


texts: How to improve reliability of infrared signaling?

texts:
I built an AVR-based gadget (bare metal AT90USB162, not Arduino) that receives an infrared remote signal and does some stuff.  For testing, I used a random TV remote that I had, and it's VERY reliable: whenever I push the remote button, my gadget sees the message and does what it's supposed to do.

Next, I built an ATtiny-based transmitter to send the same message as the TV remote.  This works too, but it's much less reliable than the TV remote.  About 20% of the time, something goes wrong and my gadget misses the signal.  It usually works on the second transmission, and I can always move the transmitter and receiver around a bit and get it to trigger.

However...I don't know where to start looking to fix this.  Since the signals are IR, I can't really compare them for brightness or other characteristics.  I don't know if it's signal strength, timing variance, or what else.

Short of gutting a TV remote and sticking it where I need to transmit from (which is unacceptable for other reasons) I don't know where to troubleshoot next.  So...people who have designed or troubleshot IR communication systems, what do newbies to the technology usually screw up?  How do I figure out what I did wrong?


texts: Confusion about a step down transformer use

texts:
This might sound a dumb question but I couldn't find an answer myself. I have come across this transformer. It has selectable I guess primary 215V to 400V, and a fixed secondary 115V. I know that nominal mains is around 115V in the US.

I first thought It is to step down lets say European nominal mains to US standard 115V. But then I though in what scenario can this be used. Theres is an ocean between two continents.

Can you give me a practical example/reason when could this be beneficial to use in the US?


texts: coocox error on debug: Error: Failed to open flash driver file

texts:
I got an error while press debug on CooCox CoIDE Version: 2.0.6 Build id: 20170117-2.0.6.

this is console message:

C:\CooCox\CoIDE_V2Beta>"C:/CooCox/CoIDE_V2Beta/bin\coflash.exe" program STM32F100RBT6B "C:/Users/Peyman/CoIDE/workspace/F100-Scartch/F100-Scartch/Debug/bin/F100-Scartch.elf" --adapter-name=ST-Link --port=SWD --adapter-clk=100000 --erase=all --driver="C:/Users/Peyman/AppData/Roaming/CooCox/CoIDE/config/flash/coocox-flash/coide_stm32f1xx_md_128k/stm32f10x_md_128.elf;"
Error: Failed to open flash driver file
Program Download Failed !

I just tested other speeds. and I am using st-link version 2 embedded on STM32VLDiscovery board.


texts: Lithium ion battery impact of cycles on discharge rate

texts:
Basically all I've been able to read and find out until now is that the capacity of lithium ion batteries goes down with cycles. I'm currently programming an arduino to accurately estimate the State of Charge of a 58V+ Li-Ion battery. I've managed to obtain plots of cell capacity against cycles as well as discharge rates at different temperatures and current draws. I am wondering how that capacity reduction with cycles impacts the cells' discharge profile. Is it decreased by a factor so that it still is bounded by the same voltages (4.2V and 2.5V) but discharges more slowly. Or does the discharge rate stay relatively the same but the bounding voltages reduce in range? Or both?
Thank you for your help!


texts:
I'm trying to design a circuit that essentially will allow you to select which voltage will be used by a number of electronics on the board (VccISO in the schematic). The voltages are already being regulated elsewhere, so it's just a matter of picking from thme. I'm expecting a current of up to 1A on VCCiso. Originally I had hoped I could do this directly with a DIP switch, but the ones that fit my application can only handle 100mA.

So I tried instead to have a DIP switch control this indirectly using MOSFETs. The gate of one of the N channel MOSEFET goes high, which pulls the respective P channel MOSFET low and turns it ON.
However the issue I have since realized is that the given the body diode of a P channel MOSFET, as VCCiso raises higher and higher you quickly have an unusable circuit.

Does anyone have some suggestions for a different approach?


texts:
I have a ESP8266MOD, that I tried to flash over the air with mdash from mongoose os. I had originally done the following steps from this turotial https://mongoose-os.com/docs/mongoose-os/quickstart/setup.md steps 1-9 seemed to work fine, but when I tried step to update the firmware over the air, it seemed to upload but I never got the console in mongoose to display anything like the guide says. I unplugged my device, and plugged back in and no longer could connect to wifi, I tried reconfiguring wifi but it did not work. I want to factory reset, but I posted in mongoose os forums and they said I need to setup a button to pin GPIO0. I have attempted to do so seen in this picture. I am stuck at this point for the button does nothing noticable.

Thanks ahead of time


texts: Dipole Antenna impedance and feed point, what is the effect of long distance to coax connector?

texts:
I have a folded dipole being made with a pair of twisted wires where each wire is 1/4 λ long and the dipole is constructed by twisting the centers of the wires so that the twisted pair is solder for about 1/2 inch.
The two pieces of wire are then inserted into a Junction Box: one end of each wire is screwed into  each of two 2 pole terminal strip. The wires are blue and red with the blues connecting the two terminal strips with a 60 mm wire together. The red wires are fed from each terminal strip to the 2 pins (center and shield) of a coax.  The coax is 50 Ω, frequency range is from 7 MHz to 28 MHz ion 6 different bands.

I hope the image can be enlarged otherwise it's useless.


texts: Why does the V/Hz ratio of a motor affect the magnetic field strength?

texts:
When the frequency is increased whilst keeping the voltage constant, the magnetic field strength is going to weaken... I don't understand why and what actually happens that causes the field strength to drop.

If anybody has an information on this I'd appreciate some clarity on the matter.


texts: I'm building a project, installing solar powered air conditioners in six separate rooms, all with  separate battery banks. How can I get a battery charger that could charge the batteries with time since the air conditioners are only solar panel charged and not inverters?


texts: How to measure S11 of antenna using VNA for one port S-parameter measurement?

texts:
I have an antenna. I want to measure S-parameters of it using a network analyzer. I am not clear how to do it. Please explain.

Thank you


texts:
I have been reading about MOSFETs and the sub-threshold region.
From what I know about diodes, they have a set saturation current.

Would it be possible to bias a MOSFET to match the saturation current of a diode?


texts: Which is pin 2 on a Harwin Datamate connector?

texts:
The datasheet for M80-6651042 Harwin Datamate connector shows us which pin is pin 1.

But which is pin 2? Is it the one to the left, or the one below? Is there a standard direction that pin numbering always goes in for dial row connectors?


texts:
I'm currently an undergraduate electrical engineering student who recently took an elective mathematical course on complex analysis, where we learned about all kinds of singularities for complex numbers, like poles.

This semester, in a circuit analysis course, we are finding the poles of transfer functions, but the concepts don't make sense in my head.

Using an easy example (from Wikipedia), say we have a transfer function of

\$H(s) = \frac{1}{1 + RCs}\$, where they say that the pole is at \$s = -\frac{1}{RC}\$, which, sure, works out at the moment. However, \$s = j\omega\$, so equating the two,

\$-\frac{1}{RC} = j\omega\$

\$\frac{j}{RC} = \omega\$

But now this means that our angular frequency, \$\omega\$, is imaginary, which I thought was not possible due to \$\omega\$ being a real number, as the frequency of a circuit would only be real (please let me know if my assumption is wrong).

So basically, I don't understand how there can possibly be a pole for that transfer function, as we have a constant non-zero real part on the denominator, accompanied by a variable imaginary term, \$j\omega\$. Given that I am assuming that \$\omega\$ can only ever be real, then the denominator can never approach 0, thus not making it a pole.

Have I made an incorrect assumption somewhere, is my understanding flawed, or is there a mismatch between mathematics and electrical engineering in what a "pole" is?


texts:
Anyone have any recommendations on a good rs232-to-usb converter. There are a lot out there and from the looks of it some are hit or miss.

Good driver support is a must.


texts: in-car truck vibration/acceleration/gyro chip suggestion?

texts:
a project of mine requires to detect how much current vibration / acceleration is in units of (G), the car will carry important instruments, and the driver will be notified if the vibration is over certain limit.

I got a sample of Analog Device ADXL345 from my friend, works but the readout is no very accurate (when stationary, I got a -0.98G on Z, and when fliped over, I got a readout of positive 0.9G, while should be around 1.0G)

After some research I got so many chips, and I don't know which one to pickup, Is there any another better chip around you guys know of?

Requirements:

3 axes
Range >= +- 8g
Accuracy >= 10bit
Error <= 0.1g
Price: < US$ 50/chip

Thanks


texts:
my question is how VFF(voltage feed-forward) pin of L6565 IC works.
does it function as a multiplier like L6564 IC?
in L6564, multi pin multiplies to vComp and makes input reference peak current (multiplier*Vcomp=Ipeakref)
or is it a "constant on time" IC and doesn't need to multiply to the input reference?
thank you


texts: Generating a PWM ramp signal using logic gates

texts:
I have a microcontroller outputting a ramp signal on an I/O pin in PWM form. i.e. the duty cycle steadily increases from 0% to 100%, then drops to zero and repeats.  After smoothing I end up with a sawtooth-like wave (except of course the sudden drop to zero takes a bit of time due to the filter).

My microcontroller code uses a 1kHz interrupt and upon every interrupt decides whether the output should be high or low based on a) the current progress through the ramp, and b) for how many interrupt cycles the output pin has already been high or low.

This is all fine and dandy, and it works well for my application, but I need a faster solution.

Something tells me this should be realizable with a pure logic circuit rather than with firmware code.  After all, we have a steady clock pulse and a steady increase from 0% duty to 100% duty.  But I'm struggling with the implementation concept.

Can anyone think of a way to do this with logic gates, so that I can write this onto an FPGA/PLD and have many (much faster) waves being generated?

--

NB: To complicate matters, frequency must be adjustable.  In my MCU code this is as simple as having a variable representing how many samples the ramp should last for.


texts: How to calculate the resistors and capacitors for an amplifier circuit

texts:
Here is an amplifier circuit that I was given in a previous question:

They told me to use this for an experiment for using magnetic fields for nearby communication instead of radio frequency. Here is the link to it.
How do I figure out what values for all of the components I should use, Is there an equation? Lets just give an example, I want a 9v input, and I want the output to turn on if the voltage on the input is greater than .1 volts AC. How would I make the circuit do this?


texts: Safe shutdown Embedded Linux on Power-Down

texts:
I am not very experienced with Embedded Linux, just some projects with the Raspberry Pi.

I would like to know if there are any recommended ways to shutdown the Embedded Linux if the device's power is removed suddenly, or if common-practice is to just ignore it.


texts: Does cutting the covering of subwoofer wire affect the sound quality?

texts:
I have Sony 5.1 channel sound system. There is some cut on covering of subwoofer wire. The copper wire is not affected at all. So, I am curious to know whether it will leak the passage of sound and hence, the sound quality will be affected or not?

Is there any disadvantage of it?


texts: How much silicon is required for the most common ICs?

texts:
Where can I find information about the die surface for various ICs? I'm thinking about opamps in the first place.

The surface area is of course dependent on the features of the ICs (for opamps rail to rail, speed, noise) and on the max current they can handle.
I think the process technology affects digital electronics, but not much analog circuitry.

So, where can I find the surface area for various common ICs and especially opamps?

This is out of curiosity, I don't have a need for any project.


texts: Reducing strobing of LED based household light bulbs

texts:
I recently purchased some LED light bulbs. In many ways they are great - really low power, and bright.

However one problem (which was apparent with both of the types of bulb that I purchased) is a strobing effect.

This is not immediately obvious until something moves in the light (e.g. waving your hand in front of it) and people have complained that it bothers their eyes.

I believe this is because the LED react so quickly, that the 50Hz oscillation of the mains supply is visible.

My question is - what (if anything) can be done to reduce this?  Are there more expensive LED bulb that do not exhibit this problem?


texts:
I've been asked if a design of mine can be immersed in transformer oil. (And still function properly!)
The circuitry is mostly SMT Qs, ICs, Rs, ceramic Cs all of which I think are OK but I'm unsure about a couple types of components - Aluminum Electrolytic Caps and Connectors.
Oil type: I don't have that info and it could vary between installations but I assume paraffin or silicone based oil.
The components I am most unsure of are:
Aluminum Electrolytic capacitors such as United Chemi-Con EMZF500ADA101MJA0G.
Connectors, specifically Molex 22-23-2041 and On Shore Technologies OSTOQ045450.
The boards are conformal coated with polyurethane.
Any advice on component evaluation or cautionary advice would be greatly appreciated.
Thank you!


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(Excuse me if this is not the appropriate place for such question. I just moved it from StackOverflow.)

I just read the wiki article about Option ROM.

A few questions I'd like to ask:

Is Option ROM a special read-only chip on some peripheral devices?
The Option ROM contains device BIOS software which is meant to help the system BIOS to interact with specific device. Right?
When system boots, CPU will load the device BIOS from ROM into specific RAM address. And it is CPU that executes such device BIOS rather than the device itself. Right?

Thanks for response.


texts: I will try to design an inductive charger which will run by using cigar lighter of the car. Does anybody have any suggestions on my project? Taking the power from cigar lighter is easy but how should I choose my circuit components for best ergonomy & efficiency?


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I bought an SDR stick like the following:

http://www.ebay.com/itm/TERRATEC-USB-DVBT-DVB-T-Stick-SDR-Radio-FM-RTL2832U-R820T-USB-DVB-T-DAB-FM-/253116591451?hash=item3aeeecad5b:g:PUgAAOSwTuJYqUeQ

I wanted to shorten the antenna wire so cut the wire that connects the SDR component to the antenna, the problem is, when I wanted to solder the two ends of the wire I saw that the wire is inside some kind of transperent tube (see picture) , and outside the tube there is lots of metal/copper wires/fibers... and I want to remove them and only leave the transperent tube and the wire in it as is.

Can I do that? will it effect something in the antenna? I'm just trying to do those changes because I build something compact...
couldn't find the answer anywhere.

Thanks


texts: Open circuit voltage gain of JFET transistor circuit

texts: So this is one of the questions from my previous past papers, I worked out my Vgs and Vds value correctly (-1.25v and 10v). However, when calculating my open circuit voltage gain, I use the equation Av=-gm.Rd, and get the value -25. When I asked my tutor if this was correct, he said that the voltage gain was wrong. He said because there's no capacitor, I need to use the equation Av=-gm.rf/(1+gm.rs) (I assume he meant -gm.rs?) he hasn't elaborated further. Any help would be really appreciated :D (Also ignore the transfer and output characteristic)


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I have a few types of solder. One of them is 0.4 mm and the other is around 0.8 (not very sure). Which one should I use for SMD, and which is good for general purpose?

I have heard that it is best to learn with a thinner wire. Is this true?


texts: What does it mean for a digital instrument when its readout is 4.75 digits "long'. And what is it like in comparison to, say a 4.5 digit meter?


texts: 600 ohm modem transformer impedance calculation by formula

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From the datasheet of a modem transformer
we have:

Impedance, Primary:   600 Ω Typ. @ 1 kHz 1 Vrms*
Shunt Inductance Lp, Primary: 3.2 H min. @ 1 kHz
D.C. resistance @20°C: Primary = 82 Ω ± 15%

Also the impedance formula:

$$ Z= \sqrt{R^2+(XL-XC)^2} $$

How does 600 Ω result from 3.2 H and 82 Ω?
(The XC is negligible.)


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Quartz crystal oscillators have better frequency stability than tuned circuits of capacitors and inductors. However, they are used only as components with a fixed resonant frequency. Variable-frequency oscillators use variable capacitors and inductors even though the resulting frequency is less stable than it would be if variable crystal oscillator existed.

Why there is no a variable-frequency crystal oscillator? Something like this:

The resonant frequency of a crystal is determined by its size and shape. This is similar to capacitors and inductors: their parameters are determined by their geometries in addition to the materials they are made of.

Is it possible to make a quartz crystal with a thickness varying in one dimension, and a sliding elecrtodes to make its resonant frequency vary?


texts: Two dimmers controlling LED strips and blinkig at certain levels

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I have two LED strips powered via two dimmers, like so:

Certain combinations of dimming on both dimmers lead to the LED strips blinking. The level of blinking is not deep, maybe 15-20% of brightness, but very annoying nevertheless. The frequency of blinking can be changed by finely adjusting the levels on dimmers. These are not fixed values; several combinations lead to blinking.
Nothing is overheating. The dimmers are rated at 8A each; max total consumption from the power supply  is about 7A at 12V. Connectors and wires are fine.
If I turn off either dimmer, the other never produces blinking, at any level.
What might be the cause of this?
It looks very much like interference. My idea is that the dimmers, being PWMs, consume power in impulses. I suspect that the frequency of the PWM varies slightly with power. So two PWMs with slightly different frequencies can produce a wobble frequency in power consumption which the power supply fails to compensate. (I can be totally wrong, of course.)
How can I get rid of that?
(1) My idea is to add a large capacitor (e.g. 500µF) before both dimmers, to help level the input voltage:

(2) My other idea, in case I got the cause all wrong, is to add capacitors to the LED strip inputs, so that pulses from the dimmers are leveled:

Does this make sense? One of my concerns is the large charging current of the capacitors; the power supply and the dimmers have short-circuit protection, though.
Any advice is appreciated.