texts: Do the recombination of charge carriers cause the diode to stop conducting?

texts:
This might be a stupid question but I am either having a mental block or I'm getting something. I'm learning about excess minority charge carriers.

So, when an electric field is applied across a pn diode (in such a way as to decrease the depletion layer width, i.e. forward biased), the carriers move from their "majority" sides to their opposite, "minority" sides.

We call this excess of the minority charge the excess minority charge concentration.

As the length travelled increases, more and more charges recombine with their opposites. So in short diodes, the charges go straight across to the "wire"/contact with only a few of them recombining.

Question:

But in (say very) long diodes, the excess charge carriers recombine with their opposites (almost) fully. So then, how is charge carried across the pn diode?

It feels like I'm missing something here. I don't fully understand the significance of the excess minority charge carriers? My book says that the initial gradient of the decay of minority charge carriers is the current. I don't understand this at all.

Can anyone shed any light on where I'm going wrong?


texts: Chosing the right motor for a vibration platform

texts:
The following photo depicts a vibration testbed that uses a motor, springs and some wood. The purpose of this effort is to make a test bed vibrate the attached kinetic energy harvester at the movement frequency controlled by the motor.

The vibration plane is connected to a stable surface by means of two springs. On the vibrating place is a motor that has a weight attached to it. This weight is fixed towards a side of the motor. This is similar to the approach utilised in mobile phone vibrators except in this case, I want the motor to drive a larger weight.

As the motor drives the weight (rotate the weight), the vibration surface will start moving up and down at a perticular frequency. This is what I want. Inorder to limit other directions of motion, I will made sure the moving platform is 1 degree of freedom. i.e. it can only move up and down.

By doing this, the attached kinetic harvester will also move up and down at the same frequency of the moving surface. This is the whole purpose of this setup; a testbed for my research.

I want to have a frequency ranging approximately from 0.5Hz - 4Hz. My mass may range from 100g to about 600g.

In that case, can someone please propose me a type of motor that I can utilise for this purpose? I think it should be a DC brushless motor. But I am not sure. Could someone please be kind enough to tell me what type of properties my motor must have? Any additional information will be highly useful. Thank you for your time.


texts:
Given the following circuit, it seems like we could use ohms law to conclude that current = voltage / resistance. With a source voltage of 3.3 and a resistance value of 220, current = 3.3 / 220 = .015 amps, however, after measuring the current with a multimeter, this value was wrong.

The actual measured current was .0061 amps.

So it seems that we need to subtract another value from the source voltage to get the right current result, I believe this value is the voltage drop.

What value do we subtract from the source voltage? Do we select the voltage drop of the resistor or the voltage drop of the LED and why?

It seems that based on the obvious values of a source voltage and a resistor, we need to include less obvious values in the calculation of current which seem to be only available by circuit measurements or by consulting a spec sheet of some sort.


texts: Does a current transformer produce a proportional voltage or current?

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I bought a current transformer which looks like the one below:

Datasheet

I wrapped the transformer around my 10A kettle, and measured the values using my multimeter.

Measuring AC Voltage, I measured 10mV (according to the datasheet I should be getting 5mV...)
When I connected it up to measure AC current, I was reading almost nothing (~5uA)

From wikipedia,

  a current transformer produces a reduced current accurately proportional to the current in the circuit.

How can a transformer produce a proportional current if it has no idea about the load? If I connect a 10Mohm resistor across the connections, will I get 10M * 5mA = 50kV across the resistor?

The labelling suggests I should get a proportional current, but the datasheet states output voltage. Which is correct?


texts:
Given the image below, we know that the second filter circuit is a Passive Low Pass Filter circuit. I'm assuming it is still a Passive Low Pass Filter with a different corner frequency. Am I correct? So my transfer function for the top circuit is just a voltage divider, which is-

$$\frac{V_o}{V_s} = \frac{Z_c||R_2} {(Z_c||R_2)+R_1}
  \approx \frac{.67jw} {jw + .33}$$

But my corner frequency should be \$\dfrac{1}{RC}\$. Do I include \$Z_c||R_2\$ with \$R\$ or ignore the capacitor?

So given this circuit, which is a high-pass filter. I get my transfer function to equal,

$$\frac{V_o}{V_s} = \frac{R_2} {(R_2)+Z}
\approx \frac{10K} {15k + \frac{1} {jw.1E-6}}$$

Now to find the corner frequency, which occurs at, \$\dfrac{1}{RC}\$, we set the magnitude of \$\dfrac{V_o}{V_s}\$ equal to \$\dfrac{1}{\sqrt{2}}\$. Included is a screenshot because I'm too lazy to type this in mathjax. I feel like I'm missing some key part of knowledge which is netting me a wrong answer, or I suck at math. Shouldn't the corner frequency occur at 667 rad/s.


texts:
I have a question that has been bugging me for a while. I have an 48 W EC-fan with nomimal Voltage 24 V (voltage range 16-30V). I wanted to plot the current-voltage line of the motor so I thought of using a laboratory power supply and apply different voltages and measure the current in the circuit and the voltage across the fan and that was it. Now, what I did is I et the supply to say 24 V and then connected the fan. The fan starts turning until it reaches its final speed. Of course as it turns faster and faster the voltage drops to say 17 V as the fan reaches its final speed. The current is 2 A. The power supply also shows 17 V. My question is then, what is the plot point for the I-V curve, 24V - 2A, or 17V - 2A?
What is the reason for the voltage drop? Is it the internal resistance of the power supply, the back EMF which substracts from the power supply voltage, or both?
Thanks


texts:
I have some trouble with my ST MK126V3.

Is it possible to program the board with the ST-LINK/V2? I can't work out from the datasheet what debug interface is used and how to connect it properly.

Link to other datasheets/manuals will do the trick.

10x

Some link: debugger, dev board


texts: What's the most economical way to digitally measure 240V mains voltage, current and power factor?

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I'm looking to capture and analyse measurements of the mains energy that I use per circuit.

I've found a few consumer products that offer powerpoint energy monitoring such as the Kill-A-Watt, but PC connectivity needs to be hacked into devices like these, and while more advanced units offer builtin USB, I'm not aware of anything off-the-shelf that comes with drivers/support for FreeBSD.

My attempts to find DIY energy monitors via Google have failed dismally, as I'm not entirely certain what to search for, but I did find one particularly interesting-looking PDF on power monitoring, which describes a variety of different software-based power monitoring techniques and how to implement them.

One of the things this PDF highlights is the relationship between voltage, current and power factor, and the fact that you cannot accurately calculate energy usage (wattage) without voltage and current, and that the power factor must be taken into account as well. I'm generally looking for a measurement solution that tracks voltage, current and PF.

The Kill-A-Watt would appear to be the most effective, simplest starting point to measuring voltage and current (and thus PF), but I'm concerned about using this device for a couple of reasons:

There are several variants of the Kill-A-Watt circuit design out there, apparently from different contracted OEMs. Hacking instructions only seem to be available for one variant.
The PCBs do not use a full voltage converter or transformer, so all components operate at 240V potential. I would describe my electronics experience as "extremely rudimentary," so I regard modifying a device like this as firmly out of the scope of what would be a good idea for me to tackle.
The listed designs are for the US version of the Kill-A-Watt, but I am in Australia. The Australian design is completely different (entirely different enclosure, etc) and completely undocumented. I understand the Kill-A-Watt will probably handle 240V as the US uses a split 120/240 system, but still.
Reading this forum discussion thread, I get the impression that not only is the Kill-A-Watt device design itself not especially advanced, but that the voltage/current monitoring hack itself could be pulled off standalone without the Kill-A-Watt in the first place.

With these considerations in mind, I'm looking for an inexpensive way to track the power consumption of my computers and other peripherals in realtime.

I have a corner I can shove a good square ft. of equipment into, so the solution does not need to be compact. My only requirements are that the system track current, voltage and power factor, and be moderately easy to build (I would describe my soldering skills as acceptable).

Software design is not at all a problem, and a microcontroller-based design would be fine. In fact, one of the things I do like about the KAW hack is that (as noted by one of the posts in the thread I linked earler) the system captures circuit current and voltage 17 readings times a second (for PF calculation). This is pretty cool, and would make for nice graphs :)


texts: What is the science behind percussive maintenance?

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On electronic devices in the '80's, electronic malfunctions could sometimes be temporarily fixed by physically "hitting" the device.

For example, I once had a colour TV - "ECTV" (from Electronics Corporation of India ECIL) which would lose image. It was enclosed in a MDF/particleboard case, and as a kid I discovered that whacking it on both sides together would sometimes temporarily make it function correctly (for a few minutes to a few hours).

I think it wasn't purely physical (like an unseated component or dry solder) because it would stop working again after a while, and eventually it was fixed by a repairman replacing a capacitor in the power supply if I remember correctly (this happened around 1996 and my recollection is hazy).

We also see this happen in various movies, where hitting an old piece of electronic equipment makes it start up. There's even a term for it, "percussive maintenance".

What's the science behind this?


texts:
This question is related to How do I use directional couplers on a differential signal?

I understand that if I have an impedance mismatch at the end of a signal cable, E.G. from a terminator which doesn't match the cable impedance, then I can expect to get reflections back.

What I don't understand is exactly what happens when you have an impedance mismatch at the driver end of the cable.

If a very short part of the cable at the driver end has an unknown impedance, is this a problem?  Will is cause noticeable reflections? My instinct would be 'no' because the length is so short.

I mean, this must happen in all situations anyway. The impedance of the driver IC's legs are not impedance matched, but they are so short that it's not a problem. Obviously, the length in that case would be very short indeed. If that's the case, then the question would be: "How long is too long?"

This cable will be carrying 100Mb/s LVDS (which stands for Low Voltage Differential Signal). This is my estimation of the spectrum of the signal.

Which is based on this wave shape:


texts: Can anyone help me to understand what these capacitors do in this design?

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I have a circuit design makes a button latch on-off and drive a mosfet. When I energize the circuit Vout that drives thr mosfet is initially low.

After pressing the button, the button state changes and the mosfet turns on. If I disconnect the enery from source while mosfet turn on state so "output of latch circuit is high", Vout starts from high level if I connect source again. However, if I disconnect the energy while output is low, Vout starts low if connect energy again. My design must be start always low latched when disconnect energy from circuit no mattter what Vout is.

I didn't understand C12,C11 and resistor connected these two capacitor what does, but these components are so important. Tell me best values for these capacitors and its reason.


texts: How to flip polarity of battery with DIY device

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Say I have a small electric motor I'm spinning with a hand crank to generate electricity and charge a battery. Every ten seconds, I slowly slow down to a stop and start spinning the other way. This will flip the direction of the current, and I will "anti charge" the battery, right?

What is the simplest way to set up a system so the electricity generated from cranking in the wrong direction is still used to charge the battery?


texts: How is the board connected to this chip?

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I have a dataflash memory that is too small to fit on a prototype board, so it has been put on a small board. I am having trouble figuring out where pin 1 is on this board. Below is a picture of the setup. The small circle on the chip is where pin 1 is. Underneath the large circles are the pins that connect to the board. Where on the board is pin 1? How do the lines connect to the memory? For the large circles on the right, how can they be connected to the chip if no lines can be seen going to them?

The pins on the dataflash memory are like this:

1. chip select
2. data output
3. write protect
4. ground
5. data input
6. clock
7. hold input
8. vcc

If I do a continuity test on pins 4 and 8, I should get continuity, right? What are pin combinations will work?


texts: How do I protect my circuit from getting more than 3.9V from a CR123 battery? With minimum components and minimum consumption during normal operation.


texts:
I have 4 PMR446 radios ("walkie-talkies"). They work great, but when using an earpiece, every-time the internal audio amplifier fires up/down, you hear a huge THUMP noise. Connecting to a computer speaker, I see the speaker move out when firing up, and in when firing down. I can only assume that there is a DC bias in the audio signal that the people at Binatone (make of radios) haven't filtered out.

Is it possible to just filter out the DC component using a capacitor in series? If so, what one do I use? Since it's a radio, I'm not fussed on low frequencies.


texts: Controlling an electromagnet strengh with arduino

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This previous question Controlling an electromagnet with Arduino deals with binary control (ON or OFF) only.
On my side I need to choose the strength of the magnetic field.

It is a home made electromagnet, I managed to power it with 12V DC + a 5ohm resistor which gives around 2Amps. The resulting magnetic field is big enough. The resistor gets hot, but this is bearable.

Now I want to modulate the intensity between 0 and 2 amps from some sensor reading, so I'm planning to use an Arduino.

Can I use PWM knowing that the inductive load is significant? Is the frequency choice of the PWM critical? Will I have trouble with Eddy currents in the soft core? (I can't use laminated core).

So my question is : is PWM a good choice really?
If yes, should I keep the 5ohm resistor? How can I calibrate my PWM frequency + alpha?
If no, what could I do instead? Which circuit?

Thanks


texts: Relation between terminal voltage and charging speed in Lithium-Ion/Polymer batteries?

texts:
I tested charging a 5200 mAh (20 Wh) battery at 10W.

Its charging level at the beginning was 20%. The terminal voltage was 3.68V. Now, I applied 10W of charging rate to the battery. The terminal voltage has then risen to 3.94V, so risen by 0.26V.

Let's increase the charging rate until the terminal voltage increases by 0.26V again. Now, we have 4.2V of terminal voltage.

Is the charging rate now 20W or higher?

00 Watts at 3.68 Volts
10 Watts at 3.94 Volts
?? Watts at 4.20 Volts ?

Is there a formula for that?


texts: I need help with making a ground loop noise isolator

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I want to build a ground loop noise noise isolator for 3.5 mm audio jack.
After some research online I found multiple circuit diagrams centered around using audio 1:1 transformers to isolate each channel. The diagrams were quite different, some featuring capacitors, resistors and diodes. Due to my rather limited knowledge of electrical engineering, I can't figure out how to build mine.
This is the transformer I plan on buying (its the only 1:1 transformer I can find in my country): https://www.tme.eu/ro/details/tr-1_1/transformatoare-pcb/
This is my current design:
Would this work? If not, what would i need to change/add. A explanation would be very appreciated since I also want to learn why is each component need.
Many thanks in advance!


texts: Difference between 7805 and ref02 module

texts:
Both of these chips provide a constant supply 5V.  My guess is, based on price and datasheets, the ref02 is much more precise and does better under varying temperature characteristics.  Watching Peter Oakes video tutorials on modular power system, he uses three different options for adjusting the op-amp input voltage; zener diode, JFET with zener diode, and a ref02 module.  He chooses the JFET with zener to give pretty precise control, but says for the best precision to use a ref02 module.  I was wondering why a LM7805 (maybe $.50) wouldn't function in the same way?  The output stage in the schematic will probably be mosfets or darlingtons or something, this is just representative and my question is related to the input.
All credit on the schematic and circuit design goes to Peter Oakes (thebreadboardca).

simulate this circuit – Schematic created using CircuitLab


texts: Can anybody explain how the inverter circuit works?

texts:
If transistor is just like a switch, it shouldn't affect the led since it forms a closed loop with the battery. So why does the led turn on and off?

I am new to digital electronics(and electronics in general) any help is appreciated.

Thanks in advance.


texts:
Imagine a hydrocarbon being pumped through a flow line

Now imagine if a valve downstream of the pumps was shut and then you were pumping against pressure !

Ok, this will cos a rupture of your flowlines, obviously

My question is, if voltage can be likened to pressure

And current to the actual hydrocarbon

And the closed valve = resistance

Can we ever have a similar occurrence in electronics/electricals ?

I am thinking no because in the hydrocarbon case the pressure differential (equivalent of EMF) is between the pumps and the closed valve, so you still have flow between those paths

But in the electrical world, the Potential difference( equivalent to pressure differential) is between the electrode with more electrons and the one without, and since we have an infinitely large resistance between the two electrodes, there is practically no differential anymore so current does not flow

Also, the mass of an electron is too small to cause a breakage or rupture of the wires

Am I right or wrong?

Thanks


texts:
I am currently facing following problem: there is a system, which consist of one master device and some number of slave devices (all those devices have tiny MCUs). They communicate with some custom protocol based on serial wire (looks pretty similar to Modbus).
All slave devices must have unique IDs within one bus, so master device can address each of those slaves. Currently I am forced to hardcode those IDs into each slave device. My goal is to flash all those devices with same firmware, so no hardcoded IDs should be used for this to be possible. I am thinking of master device, which is able to assign unique adresses to all those devices, but cant figure out, how to do that. Can anyone give me some idea or concept how to extend my communication protocol for this to be possible? Maybe someone can give me an example?


texts:
I need to limit the voltage coming out of the sync function on my radio signal generator so I can plug it into my laptop's audio input. This is what it looks like without any voltage limits:

I used a symmetrical clipper circuit with a 1.1K resistor and two diodes with 0.7V voltage drops to limit it. (I don't have enough rep to post a schematic, but if you google "symmetrical clipper circuit" click the first link and scroll down to the third image.)

Theoretically it should hold the voltage at 0.7V and it does when I use a waveform generator and give it a 10V peak to peak sine wave at 1kHz. But when I decrease the voltage I'm giving it, but still keep the voltage above the 0.7V cutoff, the peak to peak range decreases.

The really strange thing is that when I use it to limit the sync output, the function seems to decay. The later pulses cannot even be seen. When I tried using different resistors I still had the decay problem. Also the peak to peak voltage is more than the 0.7V it theoretically should be.

I suspected that the frequency was too high for the diodes, but I tried lowering the frequency of the sync output very low, to less than 1Hz and it still produced a similar result. I have read a few different questions here about clippers and articles about them, but none seem to mention this decay. Any help would be appreciated.


texts: What is the range of feedback resistors of LM2577 adjustable version?

texts:
I am making custom boost converter with LM2577 adjustable version.

I have a question about selecting feedback resistors R1 and R2

For R1 and R2 formulas available in the datasheet, but they do not specify the range kilo or mega or just ohms.

Which range I should use?   Ohm range or kiloohm range?


texts: Requirement for a high-speed (10 Mbit/s) PCI-bus synchronous serial port

texts:
What high-speed PCI-bus SSP can be recommened, capable of 10 Mbit/s supplied with suitable drivers to interface to a .NET application?

Data is sent via RS-422 type drivers with differential twisted screened pairs terminated at both ends.
Data is accompanied by a clock with +ve transitions mid-bit.
Every 5 msec the data stream transmits 2000 bytes
Each byte will have one start bit, eight data bits and one stop bit (no parity).


texts: Why put more than one winding on the low voltage side of a transformer?

texts:
In a transformer, the ratio of voltages is equal to the ratio of the number of windings on each coil. So in theory, a transformer with 1 and 10 windings should be equal to one with 10 and 100 windings. Most transformers then should be able to be reduced to have one coil with only 1 (or at least, very close to 1) winding.

I would think this would be beneficial, because less wire means less resistance. Why, then, do many transformers have many windings on both coils? (my experience mostly comes from taking apart TVs and microwaves. I don't know if this is still true for power grid transformers)


texts: Different printed circuit layout for a transistor

texts:
The below figure shows a schematic for a transistor where there exists an external magnetic field :

This schematic has two layouts to choose from. The first one is shown below :

The second layout is also shown below :

The second layout is better than the first because this will cancel the unwanted induced voltage in the transistor. I don't understand how this will happen, I am trying to figure this out using the right-hand rule but I always fail. Please, someone, explain this in details and how to figure out exactly the polarity of the induced voltage in this case.


texts: Do switched capacitor integrators have lower drift?

texts:
Im interested on getting long analog integration times, the continuous-time integrator drifts due to DC offset errors such as voltage offset, bias current and offset current, limiting its useful integration time. I turned my attention towards switched capacitor integrators which employ only capacitors and MOS switches, my hypothesis is that due to the lack of resistors, current errors can be minimized, leaving only voltage errors, which means lower drift.

There is a lot of info on the web about switched capacitor integrators and how great they are to manufacture at the IC level, however, I have not found a source that mentions the practical integration times that can be achieved using switched capacitor integrators VS continuous time integrators. Im aware that the opamp used for the integrator is critical, but opamp aside, do switched capacitor integrators have lower drift than continuous time integrators? If so, is it worth building a discrete switched capacitor integrator using capacitors, MOS switches (Like the 4066) and opamps?


texts: 100v audio source volume control / distribution

texts:
I have an audio signal from a class-d  100V and 500W. amplifier.

I want to distribute this to 16 different sets of speakers and control the volume of each set individually. I am unable to find any solution for 100V.

If volume control isn't possible I would like to be able to switch ON/OFF.Relays are one of a solution but that will be taking a lot of board space ,which is limited for my application. I was interested in this Chip, but the availability is an issue and I cant find it.

Can someone please help me to find any solution for volume control, or finding me an alternate IC or any other solution.


texts: ttl 3.3v but almost 0 amps, max232 does not send anything at 12v

texts:
Here I have basic board which has ttl serial working on 3.3v (yes I measured it) but it does not have any amps, it barely can light up pore led diode, with my meter it shows 0 micro amps current with led as load. The led light up only when its connected directly to board pins so what i can do to boost current on this ttl so so it could talk to max232

Many tnx cheers :)


texts:
I am trying to adapt an RC car to control it with an arduino. In order to do that I am trying to understand the PCB.

In the car PCB, there are:

one "RX28 TXM ZYX13AA" with 16 pins
two "TC117HS CE1P1D" with 8 pins

Where can i find the data sheets?

I only find the "TC117HS CE1P1D" in chinese.


texts: Metals Al and Au are connected in series. An ideal voltmeter, with both of its leads made of Cu, is connected across them. Then how come the voltmeter gives zero reading but why can't we measure contact potential between them if there is potential difference electrons flow right then why electron flow can't be measured If so how can we prove on paper that it is 0 V


texts: Use voltage regulator instead of zener to protect GPIO

texts:
I've read several articles about protecting 3.3v GPIOs from unregulated over voltage, all of which involve using a zener diode, a diode for reverse protection and resistors in some fashion. example 1 example 2

What I'm wondering is why I couldn't instead use a voltage regulator and get some of the benefits of thermal overload protection and reverse current protection all built into one IC. To me using a voltage regulator seems to be much more robust way of protecting the GPIOs with just one component and without having to get into logic levers or more complex solutions with many more components.

Here is the voltage regulator I'm considering using knowing that my typical input voltage is <9V and typical current well beneath 100mA.

I'm I thinking about this correctly or is something in my logic flawed?

Thank you

Scott


texts:
I'm having trouble in explaining kirchoff's laws to my cousin who is studying in first year Engineering.
Can somebody explain me in simple plain english.
Thank you very much in advance :)


texts: USB device with 2 ports - how to protect against user plugging in both

texts:
I've got a Full speed USB device which I want to provide 2 ports for - one each on opposite ends of the enclosure. This is so the cable can be connected wherever is most convenient. My MCU (atmega32u4) has only one interface, so the physical ports will shared, but only one should be plugged in at one time.

Of course users can't be trusted to not plug in both sides at once. How to protect against this?

Ideas I've come up with:

Just wire them up "as-is" and hope the host can deal with joined D+/D- pins
NAND gate with separate 5V pins as input, output to a MOSFET that disconnects Vcc when both are plugged in.

Does the second option sound reasonable, or is a more complex solution required?


texts: Valve guitar amp head with headphones only

texts:
I ordered Marshall DSL1HR valve guitar amplifier head.

As you can see in specs it has built-in "Emulated line output".
I know that a valve amplifier must be running with a speaker cabinet attached.

Is there any problem if I run my valve guitar amplifier without speaker cabinet attached, but with headphones plugged in the upper mentioned "Emulated line output"?


texts: We aways find lots of materials which explain various methods of tuning a PID controller. Also, it is not hard to find out what are those parameters. Once I've read that P and D parameters, in general, help the system to respond fast but may increase overshoot. And the I parameter should help steady state error but may lead the system to instability. My question is: are there general rules which will always be true when dealing with those parameters? Like "always when you increase X parameter will increase overshoot" or things like that. Or it will always depend on the system and I cannot say anything like that?


texts:
I've got a project where I'm trying to get the power consumption down as low as possible (on an STM32F103RCT6).

I looked at ST's document on getting the STM32F2 power consumption down as low as possible, and tried to follow its recommendations:

Setting all unused pins to AIN
Turn off the ADCs
Turn off USB
Using
PWR_EnterSTOPMode(PWR_Regulator_LowPower, PWR_STOPEntry_WFE); to go
into STOP mode while being able to wake up with EXTI

Thing is, power draw is still 4.6mA (down from 15 in standard _WFI sleep, and around 30 when actually doing stuff). The datasheets seem to suggest that power consumption in STOP should be under 0.5mA.

I've put a scope on the external oscillator and that does indeed stop.

Is there anything obvious I'm missing? Is there any way for me to check what could be causing the extra power draw?

UPDATE: I've come up with a very simple test program, derived from ST's example code:

#include "stm32f10x.h"

GPIO_InitTypeDef GPIO_InitStructure;

int main(void)
{
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB |
                         RCC_APB2Periph_GPIOC | RCC_APB2Periph_GPIOD |
                         RCC_APB2Periph_GPIOE, ENABLE);

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_All;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
  GPIO_Init(GPIOB, &GPIO_InitStructure);
  GPIO_Init(GPIOC, &GPIO_InitStructure);
  GPIO_Init(GPIOD, &GPIO_InitStructure);
  GPIO_Init(GPIOE, &GPIO_InitStructure);

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB |
                         RCC_APB2Periph_GPIOC | RCC_APB2Periph_GPIOD |
                         RCC_APB2Periph_GPIOE, DISABLE);

  RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR | RCC_APB1Periph_BKP, ENABLE);

  while (1) PWR_EnterSTOPMode(PWR_Regulator_LowPower, PWR_STOPEntry_WFI);
}

Power draw with this is still 4.3mA. I've checked the circuit too - it's REALLY basic and I've measured the voltage across every resistor (and it's zero).

Any ideas? I'm currently thinking that it's actually the LD1117 voltage regulator that's at fault!


texts: How to safely connect multiple switching power supplies to one single cold device socket?

texts:
I apologize in advance, for only quickreading howtos, and, since I am only hobbyist, I actually don`t tinker with ac power generally.

Today I can`t bypass this : I need to connect 3 switching power supplies (1x 230V=>5V, 300W,60A; 1x 12V 20A; 1x 12V 15A) to a single cold device socket.

Question is : Is it safe to connect all three supplies in parallel to the cold-device-socket (whats the correct name in english for those !?) as long as I care for good wires (I have 1.5mm pure copper core cable with good pvc isolation, which should be a bit overdimensioned already) and propper soldering and isolation?!

Are there any hints that a professional electrician could give me ?
(Apart from : dont touch ac power if you dont know what u are doing) .. I will be really really careful, I promise .. (soldered some cold-device-sockets to 3d-printers successfully already etc..)

Will the current evtl. be too much for the fuse thats built into the socket ?! I think in 230V AC all 3 together shouldn`t reach 10A !?

I`d love to read carefully and answer the question myself, but from my little knowledge, this should be possible and simple, I just want to be sure and I am already late with progress...
thx in advance, Oliver


texts: How can moving my foot possibly affect electronics meters away?

texts:
I'm curious about a strange effect I observed.

I was designing a device, which sleeps most of the time and can be woken up by a loud sound signal, like an opening door, a clap, etc.

The relevant part of the schematic:

simulate this circuit – Schematic created using CircuitLab

The ambient noise is picked up by an electret mic, amplified, and sent to a digital input on the MCU. The trimpot serves for sensitivity adjustment, so the user can tune the sound pressure level that should trigger the device. All this is very crude, as the pin threshold is not strictly defined, and the pot is not in the usual "divider" configuration (the gain selection is not linear), but that is not the issue.

When I soldered this, I noticed it didn't work; it wasn't picking sounds unless they were very loud, so I increased the amplification to absurd levels (trimpot turned to the limit, think of 19990 ohms on the right side and 10 ohms on the left side). Even at that levels, clapping hands only registered as 300 mV pulses.

While walking around the room, pondering on what can be wrong, I noticed that the oscilloscope was picking enormous signals on the opamp output, up to 5 volts. Thinking that must be the noise of my walking, I experimented more, and discovered that even in a completely quiet room, just lifting my foot of the ground produced that signal. It wasn't the sound of it, just the movement. And I was 2-3 meters away from the circuit. In a sense, the slight act of lifting my foot (or just altering its position) got registered by the sensor; whereas flipping a light switch, making a big noise with hands, etc. did not.

In the end I found what the problem was. The sensor I was using is a ECM30B. It has the traditional two pins, along with a metal tab protruding from the casing, that also seemed that needs to be soldered. Usually these mics have the ground pin and the casing inherently connected. But this one wasn't. When I connected them, the circuit behaved as expected, and with the huge amplification it picked even minute sound noises.

In a sense, the circuit was open at the "X" point. Not really, since the ground pin of the mic was soldered to ground, but just the casing was floating. With this in mind, what could have been the effect that captured my foot moving meters away (even considering the enormous amplification), but ignored similar movements with my hands?


texts: Can I use one resistor divider to provide virtual ground to both halves of LM358 OpAmp?

texts:
I am trying to use an LM358 opamp to amplify an electret mic to something that I can read with my attiny85's ADC. (What can I say? I like DIP-8's :)

I feel that I need a gain of about 100 to get a decent signal.

I'd like to use a single-supply configuration, with a voltage divider to provide a virtual ground.

My first design used one half of the LM358 as a basic inverting amplifier with gain 100, and the second half to provide a virtual ground as in:

http://www.swarthmore.edu/NatSci/echeeve1/Ref/SingleSupply/SingleSupply.html

Now, the LM358 has a gain-bandwidth product of 1 MHz or so, which means that my 100 gain will start to be affected at around 10 kHz.

What I'd like to do is to use both halves of the LM358, each with a gain of say 10 and a coupling capacitor between them.

The page I list above indicates that the virtual ground current of an inverting amplifier is zero, which suggests that I should be able to use a resistor-divider for both amps.

Does that sound right? Or am I missing something?


texts:
I wanted to run LED bulbs with a mobile phone charger/adapter ( input: 220v AC, output: 5v 350mA, nokia). but the LEDs become very hot & I'm afraid they may burn. i don't know the ratings of these LEDs bcoz the shopkeeper from whom i bought these also doesn't know. but they r the common type in market.  i think I should reduce the power. but which one? (ampire or volt, which harms LED?) & how can i do that? i tried to add a resistor in 'series connection' but it make the LEDs very dim. i heard resistors in series don't reduce voltage, they reduce ampire. is it true? should i add resistor in parallel to reduce voltage?
please pardon my poor English. I'm not a native English speaker & also newbie to electronics.


texts:
in the datasheet of the Si823x family of gate drivers, the Si8234 is mentioned as being a high-side/low-side driver with PWM input, but actually this "PWM" input pin is only there for switching between the High and the Low sides.

simulate this circuit – Schematic created using CircuitLab

in the absence of the "true" PWM functionality in the place where I was hoping to find it; can i use another pin, wich is the disable pin, as a "true" PWM input?:

according to the datasheet the Disable pin when it's active drives outputs VOA and VOB low; and -in consequence- both sides are disabled...

my question is:

is this behavior of this input pin and its fast switching time (60ns) sufficient to make it a PWM input?

Note: example of use: an H-Bridge DC Motor Driver.

simulate this circuit


texts:
Can you see the output waveform of this transformer across it's terminals
if neither is tied to ground ? I assume it follows the input waveform in shape
but if there is no zero reference would it still be able to be seen on a scope?
Thanks


texts: Problems with OpAmp based amplifier simulation

texts:
I'm trying to simulate a simple amplifier for an electret microphone, but having problems regarding the output level and virtual ground.

The circuit in Multisim is as follows:

What I'm having trouble understanding is:

Why is the virtual ground at 3v and not 2.5v?
Why is the output swing 3x larger than the input swing and not ~100x?

Also, here's a scope trace which may be useful: (input - orange (ch.A), output - red (ch.B))

Edit:
Here are the currents in the feedback network:


texts: Would a 7805 5 V regulator drain a 9 V battery?

texts:
Doing some DIY as a hobby, I'm making a small humidity-temperature radio sensor.

An ATmega328 is reading from a DHT11 sensor and then transmitting data to a Raspberry Pi by an STX882 radio transmitter. It is powered by a 9 V battery using a 7805 5 V regulator with 10 µF and 100 µF capacitances.

The C code on the ATmega is reading humidity and temperature and then sending it every 30 minutes:

const unsigned long DELAY = 30*60*1000UL;    // 30 minutes
void loop() {
    delay(DELAY);
    send_data(); // Maybe a little overcomplicated, but I think it is not the point
}

This was working like a charm, but the battery life has been unexpectedly short. It was brand new, and I made some sporadic tests with a short delay, with no abnormal heat coming from anywhere.

When I was satisfied, I put the 30 minutes delay and leave it alone (which was maybe a bit hazardous?), but after less than 24 hours the battery was 5.4 V dead. The 30 minutes delay was approximately respected for its lifespan though.

What could explain such a short battery life? Could it be the 5 V regulator? How could I build a long-lasting circuit?

PS: I'm still trying to Fritzing some diagram, but this takes age for noobs like me...

I used a 6lp3146 generic brand alkaline 9 V battery which apparently provided 300-500 mAh at 100 mA current, which is far more than what my circuit use.

Here is all information I could gather from the datasheet:

+-----------------+-------------+----------+-----------+---------+
|                 | DHT11       | STX882   | ATmega328 | 7805reg |
+-----------------+-------------+----------+-----------+---------+
| Voltage         | 3-5.5 V     | 1.2-6 V  | 2.7-5.5 V |         |
+-----------------+-------------+----------+-----------+---------+
| Active current  | 0.5-2.5 mA  | 34 mA    | 1.5 mA    |         |
+-----------------+-------------+----------+-----------+---------+
| Standby current | 0.1-0.15 mA | <0.01 µA | 1 µA      | 4-8 mA* |
+-----------------+-------------+----------+-----------+---------+
*"bias current"

If I understand correctly, my system is active for a few seconds every 30 minutes, so the standby current is all that should matter, and it is indeed driven by the 7805 regulator.

So yes, in the worst case, with 300 mAh I should be able to keep the system alive for only 40 hours.

Is there a way I could feed my system 5 V for a much longer time without a much bigger size?

For the record, here is a very good video about LM regulators vs. buck converters: Buck converter vs. linear voltage regulator - practical comparison


texts: Is there possibility for a race condition in the following circuit?

texts:
On this wikipedia page, there is an example of a circuit which implements a D latch using NAND gates :

Let's say the flip flop is initialized correctly (eg : Q = 0 and !Q = 1).

If D = 1 and E = 0, the right part (which is, AFAIK, a SR latch) will have S = 1 and R = 1 (which will maintain state as expected).

Let's say E goes to 1.

S will become 0. If the gate at the bottom left would update at the exact same time, R will be 1 (which is what we want, the SR gate should now output a "1").

However, what happen is that bottom left gate will only update slightly later. Because of that, the right part will have S = 0 and R = 0 for a very short time (which is a forbidden state). Is this OK ?

So to me, there is possibility of a race condition. I might be missing something, that is why I'm I am asking here.


texts: How does adding an output resistor isolate an op amp from a capacitative load?

texts:
Many datasheets recommend this, for 'stability.' I've never understood this. Googling the subject I've seen much talk about "adding additional poles" but, not being an electrical engineer I don't know what they mean by this or why it helps.

Can anyone provide some physical intuition? It seems that the op amp will 'see' the capacitor whether or not you put a resistor on the end of it.

Another question: how does one choose the value of this resistor?


texts: 24V truck battery - voltage when the engine is running?

texts:
What's the actual voltage when the engine is running for a 24V truck?
I know that for regular cars, the 12V battery voltage is above 13V, but I was wondering what the voltage is for a 24V truck battery when the engine is running.


texts: Identifying a wall socket with 8 small, 2 larger holes in trapezoid/star configuration

texts:
What kind of connector is this?

Country: Germany
Location: University Building (Department of Computer Science)
The logo in the middle rather looks like an "h"
6 smaller holes form a trapezoid
2 of the smaller holes are horizontally arranged in the middle
The 2 large holes are horizontally arranged at the bottom

It is located in a wall panel where also power outlets and telephone and ethernet sockets are located.


texts: How would I use a rotary encoder without housing?

texts:
I'm looking to buy a rotary encoder and I've stumbled upon this:

which I assume is an encoder stripped of its housing.
My question is how would I use it? There is no shaft to turn, so I'm assuming I would need to buy the housing separately, which probably would affect accuracy.
It is however much cheaper than standard encoders and has a great resolution.

EDIT:
It is an AS5600 as seen
on this site or
this site.


texts: How can I measure voltage up to 120V in an Arduino?

texts:
I'm a beginner in electronics world, I've developed things before but not so sofisticated. Now I have to create a prototype and I need to measure voltages up to 120V. I've seen there are sensors that can do this job but they're only capable to measure 5-25V. Is there any way I can transform voltage from 5-120V to 5-25? I need to know when there's a change in voltage. Or any other idea that could help me?
I explain: my controller will have storaged the voltage when there's a device plugged-in and it's working, I need to find the way to measure this voltage so I'll be able to storage it dynamicly and compare this storaged value to the actual so I'll know when the device plugged-in is ON or OFF.
I appreciate your attention, thanks.


texts: 3-phase Inverter in single phase operation

texts:
I'm working on a standard (AFAIK) 3-phase, 6-pulse inverter.  I'm testing it under single-phase conditions to see what the de-rating will be.

My understanding: With everything else staying the same, if I pull one of the AC phases, I should end up with effectively 1/3 the RMS current out because I now only have 1/3 the number of pulses.  But the peak currents seen by the transistors should stay pretty much the same because that's controlled by the differential voltage across the choke and transistors... and the voltages haven't changed.

My question is: Can I rewire the 3-phase choke within my system so that the third winding (which normally would not be used for single-phase operation) is in series with one of the other windings? Like so:

simulate this circuit – Schematic created using CircuitLab

This would allow me to increase the inductance value without needing to have different parts for 1 vs 3 phase operation.
My concern is whether the physical asymmetry in the inductance values will cause a problem.  On paper, there is only one current path so everything is in series. In reality, the factory AC grid is in the middle... so who knows what goes on out there.


texts: What could be causing an unreliable output for 3 different IS31FL3731 chips

texts:
I have a board that uses the Adafruit breakout of the IS31FL3731 to control 81 illuminated switches. I have some code that runs on an Arduino that should turn all the lights on, but only about half the lights turn on - a seemingly a random half.

I have three IS31FL3731 chips and they each turn on different set of lights, so I think the chips, or how I am using them, are the issue.

There are so many different places where things could be going wrong (board layout, soldering, code, faulty chips, too few amps, etc.), but I'm hoping somebody may be familiar with a problem like this. If so, it could save me a lot of troubleshooting.

It is also worth noting that when the board has the shift-registers in place, there seems to be some sort of short circuit - the current rose to about 1.3A before the controlling Arduino shut down.

My part of the code and pictures below.

void loop() {
    int numLEDS = 81;
    for(int i = 0; i< numLEDS; i++){
        LED_PWM(i, 255);
        Serial.write(i);
        delay(20);
    }
}


texts: I have here a 3 phase inverter and a PMSM, where I can measure the phase current of two phases and the input voltage of the DC supply. The PMSM is connected in star connection. I would like to estimate the current drawn by the DC power supply, but I don't know how to do this.


texts: Volatile keyword with ADC, USB interrupt readings

texts:
I was just reading an answer about global variables, it also stated that I should use volatile affix whenever a global is used in an interrupt.

In my program I am using a 30 byte ADC buffer without interrupt, it just gets regularly updated with DMA transfers.
There is also a 4 byte USB buffer which gets updated whenever I receive an USB interrupt.
There is a variable that gets changed every time main while loop starts over, it reads one of the adc values and updates itself with a proper math function, and then gets used in another function frequently to generate something else.
There is a counter which I increment in every while loop start over, it is used widely in my code ecosystem. Has nothing to do with interrupts or external sources, just gets incremented whenever code finishes a full cycle.

In which of these four situations I should use volatile and would it lead to any memory based side effects in my system?

I wasn't using volatile fix since now and not sure if I ever faced a problem related to this.

I am using cortex M-4, pure C code.


texts: What possible ways can I upload sketches to Arduiono Mega chips?

texts:
I have been updating the embedded code on a set of Arduino Mega chips.

I have been performing the upload via USB. Unfortunately, this is extremely unreliable. I get an error along the lines of

avrdude: stk500_getsync(): not in sync: resp=0x00
avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51

I simply get another board (we have a whole shelf full of them) and work with that one until it stops working as well.

According to this forum, I'm not the only one who's having this problem.

I've heard (somebody telling me he heard from somebody else) that the USB transfer is unreliable, and that there's some other way.

Can anyone tell me if I'm hearing correctly, and if so, what the upload method is?


texts: Chipscope ILA unable to capture signals correctly

texts:
ALL the ILA modules that I am having now do not work .
I mean they failed to even capture the user-assigned 'clk' and 'resetn' signals. Why ?
Note: the PCB schematics could be found here


texts: Efficient low current buck controller topology

texts:
In SMPS there are two sources of loss: parasitics, and the controller. Usually, the load consumes more power than the controller, and the parasitic losses dominate. I have the opposite situation. I have a buck converter with a load of 50mW, input voltage of 5V and output voltage of 1V. My question is: what is the best topology that minimizes the controller current consumption? Assume that the dynamic performance is not important.

My current solution is 1 comparator + 1 opamp for a current source in order to get accurate hysteresis implementing a bang-bang controller. Is there anything better?

I should also point out that a 200mW controller will give you the same performance as a linear regulator. Since the controller needs to be powered by the input, this give an upper current consumption bound of 40mA.


texts: Circuit analysis with 2 diodes : Constant Voltage model

texts:
It's a problem about sketching V_in  V_out characteristics(sketching graph with V_in as x axis, V_out as y axis) with constant voltage model in different V_D,on (V_D1,on != V_D2, on)
Starting from V_in = -inf, both D1 and D2 are turned off : (D1, D2) = (off, off) and it's obvious that V_out = V_in until one(or both) of diodes will turn on.
After that, I have to find the condition for one of diode turning on : like (on, off), or (off, on).
But how can I know which of 2 diodes will turn on first as V_in increases from -inf?
Both (on, off) and (off, on) are reasonable I think... I can't decide what's collect :(


texts:
In this code the one LED is glowing at one pin PC0 with flash every 50 ms. It has XTAL of 16 MHz. With CPU frequency 16 MHz, even a maximum delay of 16.384 ms can be achieved using a 1024 prescaler. Every 256 prescalar value, it is achieving interrupt.

DDRC |= (1 << 0).... In the given code, what does it mean.
I want to glow all LED at PORTC. For this, what i have to change in
DDRC |= (1 << 0).

#include <avr/io.h>
#include <avr/interrupt.h>

volatile uint8_t tot_overflow;

void timer0_init()
{
    TCCR0 |= (1 << CS02);
    TCNT0 = 0;
    TIMSK |= (1 << TOIE0);
    sei();
    tot_overflow = 0;
}

ISR(TIMER0_OVF_vect)
{
    tot_overflow++;
}

int main(void)
{
    DDRC |= (1 << 0);
     timer0_init();
    while(1)
    {
        if (tot_overflow >= 12)
        {
            if (TCNT0 >= 53)
            {
                PORTC ^= (1 << 0);
                TCNT0 = 0;
                tot_overflow = 0;
            }
        }
    }
}


texts: Flip-flop vs combinatorial description - what exactly is the difference?

texts:
I was going through some reference design from Altera's Wiki and ran into the following piece of code:

always @* begin
   in_ready <= out_ready || ~out_valid;
end

My understanding is that having a flip-flop like that helps get more deterministic timing, synthesis tool can refuse to synthesize if out_ready || ~out_valid combinatorial delay exceeds the limit and timing requirements are not met etc. Other than that, that should be en equivalent of the following combinatorial description:

assign in_ready = (out_ready || ~out_valid);

What made me think about it is the larger piece of code that I am readying. Sometimes combinatorial logic is used to drive the "ready" output of some modules, but sometimes this style. I cannot really spot a functional difference and see an obvious explanation.

I've read somewhere that combinatorial logic is not welcome in FPGAs because of timing issues and synchronized design is always preferred, and this project specifically targets FPGAs. But the mixing is what confuses me. So two questions popped out in my head:

When and why one solution should be preferred over another?
Is there any difference in behavior (or analysis of the design) when the output of the module is "reg" versus when it is a "wire"?

Any help is appreciated. Thank you.


texts:
I have a container with flux paste.
It is not very practical so I would like to transfer it to a syringe.

Can I simply melt it by heating it (double heater with water)?

It is also pointed out that sometimes I used the iron directly in the paste for cleaning so here and there there are puddles of water, which usually disappears when I leave the container open, but still could be embedded in some pockets.


texts: which generates more efficiently, single or 3 phase systems

texts:
I want to build a hand crank generator for my travels and I am curious if there is an advantage to a three phase "motor used as generator" design or if it will be around the same output to a similarly rated ac motor or even a brushed dynamo.

I recently tried using a super potent rs775 with a nice long lever and high gearing ration of 1:160 but boy getting 20 watts (per hour rate) is hard, i could barely do 15 min. yet I saw this one small 25 watt generator review online with a lever half my size and was matching my output. I feel dumb almost, that they managed to do more with so much less. they had a small 3 phase generator with a much lower gearing.

So is this possible because of the 3 phase motor? or is this witch craft.


texts: How is Line and Phase Voltage the same for a Delta connected system?

texts:
I am having a little bit of confusion for some reason understanding how the phase and line voltage can be the same for a delta connected system, i understand why the current is different for the phase and line current (since there are 2 paths for the line current to go through etc and hence it is larger then the phase currents).

All i have found is pages, youtube videos etc mainly just saying it is equal to the phase voltage, nothing specifically saying why. I understand why no neutral connection is needed as well (since the sum of the voltages etc is 0).

Essentially what i am asking is how/why are the line voltages and phase voltages the same?

Is it due to the fact that they are 120 degrees out of phase? Hence say a 3 phase balanced source of 120 V was connected to a delta system, how is VRY=120V when Y is at 120V peak? If Y = +120 V peak, then wouldn't R be 0V? However it is not is it?

To get VYR to be a difference of 120 V, what does VR and VY equal?

I guess i do not get how say point R can be essentially 2 different voltages for YR and then RB.


texts: Efficiency comparison between six step and FOC for a given motor

texts:
For a given PMSM motor with sinusoidal back-EMF, it can be driven by either six-step (as in drone applications) or by FOC (as in servo control). However, for a given motor and given DC link voltage, how to compare the system efficiency difference between six-step control and FOC control?

The reason to ask this question is that drone development is getting popular and majority of ESC solutions in the market are using sensorless six-step control. However, now people began to talk about sensorless FOC for drone ESC. So I would like to understand their difference in terms of efficiency because for drone, IMHO, flying longer time and longer distance is more important than acoustic noise.


texts: I have studied the fact that the capacitor does not like a varying voltage across its terminals, and it acts as a short circuit initially so that there is no voltage drop across it. If this is true, then why does it acts a short circuit (or a low impedance connection) in case of AC signals, which have alternating or changing voltages every moment?


texts: Function of undocumented pads on PCB mount power module

texts:
I'm hoping someone may be able to explain to me why are there extra pads on the bottom of APXW003 DC/DC SMPS PCB mount module from ProLynx series from GE Industrial. I am doing a design and it turns out cheaper for me to use these modules than to make a SMPS from discrete parts.

The datasheet, which can be found here:

http://apps.geindustrial.com/publibrary/checkout/APXW003A0X?TNR=Data%20Sheets|APXW003A0X|generic

makes no mention of the circular pads which can be seen in the land pattern presented on page 19 of the document. I have ordered a few of these modules and checked for continuity of these pads, and found it to be as in the picture attached (two of them connect to GND, one of them connects to VIN). I have read the datasheet twice carefully and was not able to find any mention of these except on page 19 where they are just labelled "keepout".

Could someone explain to me the function of these pads? Should I connect them to GND and VIN on the PCB as I have found (with a multimeter) they are internally connected to those pads? They strike me as very strange as solder can easily bridge a pad and those circular "keepout" marks - especially the one between "VS+" and "VOUT". What is their function?

Thank you!
-Igor


texts: Do I need to cross my Tx and Rx for an Ethernet AUI interface device?

texts:
I have one device with an AUI Ethernet interface coming out of a non-standard connector. I'm making a cable to attach the device to a COTS transceiver which contains the standard D-Type AUI connector. On the non-tranceiver device documentation, it has pins labeled as "Tx+", "Tx-", "Rx+", "Rx-", etc. On the transceiver documentation, it just says "standard D-Type AUI connector" which I can readily find a pin-out for.

I'm a little confused on whether I need to cross the Tx and Rx lines in my cable. The standard AUI connector lists pin 3 and 10 as Data Out, and I think this is relative to the device that houses the connector (the transceiver).

Here is the installation manual for the transceiver: http://www.unicomlink.com/pdfs/20028T_Manual.pdf

It says I need a "transceiver drop cable." Any ideas what that means?


texts: What does it mean when there is a voltage difference between ground and neutral?

texts:
Between ground and hot there's approximately 120V as expected.

I had expected the voltage difference between ground and neutral to be 0v, but instead it's 0.4V.  Why would this not be the case?  Is it a hazardous condition?  How would it be corrected?


texts: Why does the PWM signals amplitude drop once connected to low-side n-mosfet switch?

texts:
I am applying a 3.3 V pwm signal to a circuit similar to the following (Credit: Olin Lathrop):

I am using an IRLR024N N-MOSFET, which switches if i connect the gate to the 3V3 pin of my microcontroller. It doesn't switch if i use the PWM signal though. The oscilloscope shows it clearly: The voltage difference between gate and source terminal is not great enough (from datasheet): $$V_{gate\_treshold\_max} = 2 V$$
Sorry for the bad image quality, 1V/div, math mode, ch1 (red) is the pwm pin, ch2 (yellow) is the ground pin, green is ch1-ch2. The first picture is without connection to the circuit in the first picture:

Now when i connect the PWM-pin to the gate, ground pin to source of the mosfet (I have an 12V 5A Power supply which feeds the circuit):

Do you have an idea what may be the issue or what could be a solution?

If you have any questions, i will answer ASAP!

Kind regards

Update:
All good now, IRLU024N just wasn't up to the task. IRF3708 does the trick.   Also fixed my measurements and used the ground clamp on the probes. I get around 7V@100% Duty-Cycle. I tested the circuit on a breadboard though. Next step is diagnosing where the rest of the voltage drops happen and then soldering to a PCB. Running into this problem and your answers helped me expand my understanding tremendously though, so thank you!


texts:
I want to convert my tail light(Peugeot 405) to LED light.there are 5 lamp in this case.

Instead of each lamp I think 6 white LEDs are enough. as you know better than me, each white LED is 3.3v and 20mA, so it is my circuit diagram for that :

So my questions are:
1) Is this circuit diagram correct ?
2) How many LEDs are you suggest for each lamp ?
3) Is it better parallel all LEDs together and at the end I calculate a resistor or like I draw instead of 3 LEDs I put 120Ohm resistor.

At the end it would be great if you have a video or pictures for that step by step.

Thanks in advance


texts:
The datasheet of the IR2110 shows this as the typical connection:

And in some cases even a gate-source resistor is used, as in this and this post

But the app note shows this as the connection for a buck converter, no resistance whatsoever:


texts:
I have two circuit boards that are almost identical. One has a JTAG socket, and one does not. I want to add a socket to the one that doesn't have one, but I don't know which part to get.

This is the socket in question:

This is what the board looks like without one:


texts:
I purchased this product:
https://www.sparkfun.com/products/11502

I've wired it up to 5 membrane pressure sensors which provide variable resistance depending on the pressure exerted. However I'm not sure if the GPIO expander I purchased above supports the analog signal coming from the pressure switches.

My issue is that the pressure switches are too sensitive and are giving false presses, and I was hoping I could use the variable resistance to calibrate how hard one must press to register, but I would need the analog signal to make this possible.

Here are the switches:
https://www.sparkfun.com/products/9375


texts:
Given: Va= 10V, Vc= 15V Ve= 20V find Vb and Vf
so I calculated the voltages using KVL and I got Vb= 10V and Vf= 25V but when I checked my answers it showed that Vf was 5V
is Vf = 5V if so then why?


texts: Significance of negative setup and hold time

texts: What do you mean by negative setup and hold time i.e what happens if hold time is negative or setup time is negative. Does -ve setup or hold have any advantage ?


texts:
I'm going to buy a PC tower case which has only one LED intended to be used as the power LED, thus no HDD LED is available.  My intention is to have that single LED at about 50% of its intensity when the PC is turned on and there's no HDD activity, and to have it at about 100% brightness to indicate HDD activity.  Thus, it would become some kind of a "hybrid" LED indicator.

I'm not sure how the LED outputs are actually constructed on the motherboards, so my initial thoughts were to use optocouplers.  Please keep in mind that I'm nowhere close to being an expert when it comes to designing electronic circuits, even the simple ones.  So, here's what I had in mind:

I haven't calculated the resistors yet, though having 220 ohms in all places should be fine -- or at least it looks to me like that.  Also, I haven't looked yet at exact optocouplers and their CTR values.  Could the whole thing be made simpler without risking to damage the motherboard which is an expensive one?

Please advise.  Thank you!

UPDATE: Based on a reply below, here's how a simplified circuit might look like.  It would also handle ACPI sleep states when there's no +5 V from the PSU except the +5 VSB, and the power LED blinks in such cases.  Would it work?

UPDATE #2: Yeah, it should work as pointed out below, and it also cuts the required number of components in half.  I'll try it out once my tower case arrives so I can see which brightness level works well, and I'll report back.

UPDATE #3: D1 is redundant, as the LED inside the optocoupler can't be damaged by receiving a reverse voltage coming from the motherboard's HDD LED output.


texts: A zener diode versus a linear regulator for a 5 V 100 mA output

texts:
I have a 12 V supply and wish to use it to provide 5 V supply to NodeMCU, which draws about 110 mA.

Which would be better to use? A 5 V 1 W zener and a 70 ohm resistor? Together they cost about $0.10 and only two parts to solder.

Or voltage regulator? An AMS1117 5 V with two capicators costs about $0.30 and three parts to solder. Or maybe a 7805 which outputs 5 V?

I will be making about fifty of these boards.


texts: I would like to regulate LED brightness with audio signal tone 1khz

texts:
I'm working on school project where I need to control LED strip brightness with
audio input...

The stereo signal is playing some music on left channel and LED is suppose to react to
generated 1khz tone on right channel. Audio signal is far to low to work so I would ned some amplifier...
I've tried to do it with LM358 but I couldn't find any working schematics.

I have some basic knowledge about circuits, but not in this area.
Any provided schematic is welcome.

EDIT:

Here is a picture of circuit that acts like this.

I know that this circuit is not like it should be, but hey, at least some result.
All I need is some more 'amplification'. So to be clear, I don't think I need filtering because the tone is stable 1khz and all it maters is strength of it.

*I only use 5V supply from Arduino on video


texts: I don't understand transformer power ratings

texts:
I'm befuddled.  I have a wall wart power supply that supplies 65W (it's for an Intel NUC).  I'm interested in building my own power supply that will put out... several different voltages and currents.  So I go to mouser.com and try to find an appropriate transformer.  I plug in several different power ratings.  And then the trouble starts.  They all cost much more than I expect.  And, I notice, they're huge.  So I search for something that ought to be in my NUC's power supply.  What I find for 75VA is about 8-10 times larger than the entire NUC supply.  And it costs twice what the whole NUC supply costs.  So I cut open an unused wall wart.  Yes, it has a transformer.  No markings on it at all.  So now I'm wondering whether I know what a power rating on a transformer is.  If I believe mouser.com, then the NUC's transformer (if it has one) is wildly undersized.  If I believe the NUC, then mouser's are wildly oversized.

What am I missing?


texts: Buildint series voltage regulator using transistor and zener diode

texts:
I am a new to the electrical engineering and currently trying to calculate the series voltage regulator for raspberry pi at maximum current draw.
Raspberry Pi works at 5 volts and 2.5 amperes at maximum load(they specify that power supply is recommended to support 2.5 amperes therefore I use 3 amperes in my calculations for wiggle room).
Here is the circuit I came up with:

Ignore heat management, I would like to figure out math first.
My questions are:

How to mathematically determine zener voltage needed?
How to mathematically determine resistor properties needed?
How would I calculate Vb of transistor?

Thank you.


texts: data signal on headphone jack input on iPhone

texts: I am building an external device for the iPhone that will produce an analog signal that I want to send through the headphone jack.  From all my reading, all data sent through the jack is in analog form, yet when i've read up on other hacks doing similar things(like hijack) everyone is including a microprocessor as part of the external device.  if the iphone has an ADC(which it does) why bother with the microprocessor?  It seems to me all you would need is a signal amplifier/rectifier and then use the output from the native ADC to create your end result code.  Meaning basically treating the analog signal like any other signal from the headphone set and normalizing the results to create the effect/outcome you are looking for.  What am i missing?  any answers greatly appreciated.


texts: Fan control circuit not working, Fan remains ON

texts:
Goal:

I am attempting to only turn on the fan when the THERM signal of the temp IC (IC2 in schematic) goes LOW. The IC works in that it triggers an active low on THERM when a temp threshold is crossed (40degC in our case)

Issue:

The fan is on at the beginning even before the active low is triggered (5V still passing through emitter to collector).
The active low does little to the base voltage (I measured over 4V at the base even though I verified almost zero at THERM)
I chose a PNP BJT because I thought ON would be triggered from a low signal and OFF when high..but this doesn't seem to be the case.
Does it have something to do with my Vb < Ve at the beginning? (3.3 at base through pull up resistor vs 5 at emitter?)

Could someone possibly recommend a transistor that might work in this application?
Thanks so much!


texts: Connecting different length led strips in parallel

texts:
I'm planning to illuminate a section of the house using some standard 5050 led strips.

However, All the parallel wiring examples I've seen have equal length strips. I was planning to have some strips of different lengths, like a 6m strip and a few 1m strips, connected in parallel to the same power source.

My limited (and very rusty) EE knowledge is telling me that this is probably a bad idea. I just wanted to double check here to see if what I'd like to do is actually viable (without additional circuitry or components).


texts: Is there a light sensor that varies output with wavelength?

texts:
What components are sensitive to the wavelength (energy) of impinging light?

I am wondering if there are any that have a reliable and detectable response to wavelength instead of just intensity.  For example, if some hypothetical component responded to light in the range of 400-1000nm, then when exposed to say 10 photons at 400nm perhaps its voltage (or impedance) is a significant multiple of the voltage when exposed to 10 photons of 800nm?

Clarification: I know that it's possible to do spectral imaging using prisms and/or filters so that a sensor can say, "I was just hit by this many photons," and based on the filters we know what those photons' wavelengths could be.  What I'm wondering is whether there is any component that can say something like, "A photon hit me this hard," where this is a relatively precise measure of the photon's energy.


texts: How do I add a phone number to the SIM900? Can I add a phone number to the SIM900? Assuming I can, would I send the phone number through the AT Commands or the actual SIM card? I don't know how to write to a SIM card without another phone, so I am lost on how to write it standalone. The purpose of this is that I want to add my phone number to another device that uses Arduino and an SIM900 breakout. It is a project that could use that "phone" to receive calls and SMS and etc.


texts:
What are the voltages and currents on diodes D1 and D2 in the circuit below?

The diodes are modeled as ideal and allow current to pass at 0.7V.

R1=9kΩ, R2=1kΩ, R3=9.3kΩ

Edit: Sorry for making it seem like i just want you to do my homework, i have tried solving it but with no success, which is the reason why i'm asking this here. Anyways, I am assuming both diodes are conducting, but the setup of the circuit is confusing me and i can't seem to reach a solution


texts: 4 to 1 multi-bit multiplexer implementation [Q]

texts:
We are tasked with creating a 4 to 1 multiplexer with 4-bit inputs. I believe I fully understand how to create a 4 to 1 1-bit multiplexer, but I completely do not understand what the 'input' side and 'output' side of a multi-bit (4-bit in this case) 4 to 1 multiplexer would look like. This is my first ever introduction to circuits so I do not understand more advanced topics.

My updated attempts at what the MUX and DMX would look like are below:

Diagrams were made in Logisim.


texts: How to hand solder pads underneath an IC?

texts:
I have to design a board with a package case called MSOP-16

It has a large ground pad underneath the IC.  What are good methods for soldering this pad by hand with a soldering iron?

Since it is a prototype, I was thinking to put a large enough via inside of the pad and to heat the via and drop solder through it from the other side after the outer pins have already been soldered.


texts: Is there an equation for the cutoff frequency of a chebyshev filter?

texts: I have this circuit here which is a low pass chebyshev filter, I have been asked to find it's cutoff frequency. I have used matlab to plot an output response against angular frequency graph here. But I'm unsure of how to find the cut off frequency from this, is there an equation to do this?


texts: Understanding PLL performance: PFD output bandwidth

texts:
For an application I need to FM modulate a signal with a 10 MHz bandwidth. Due to constraints I have no control over, I have to do it in an analog way (so I can't just digitize the signal, IQ modulate, etc). The center frequency of my modulator is not of too great importance since I will have to use second converter stages to shift it up to the target band anyways.

Since no manufacturers (of which I can easily acquire ICs in low volume) seem to make FM modulators that support that bandwidth, I am looking at building my own, based on a PLL.

For the modulator, this translates to injecting the to-be-modulated signal into the error loop, after the low-pass filter of the PFD, and thus modulate the VCO. For the demodulator, we input the received signal as reference, and given the PLL loop, the PFD will try and output the wanted signal as error to the VCO (but the filter prevents it from reaching the VCO).

In the modulator case, we require that the VCO control bandwidth is high enough to actually modulate. In the demodulator, we require that the PFD has sufficient output bandwidth to keep up with this 10 MHz modulation. However, in single-chip PLLs, neither of these parameters are often specified (and I don't think they have enough bandwidth for my application, though I will have to verify this with measurements).

For this reason I am now also looking at using standalone blocks to build a fast enough PLL. Minicircuits have various oscillators with high control-voltage-bandwidth, so that just leaves me with the PFD. There are a few very fast ones on the market, but none of them give a bandwidth as they operate in a more digital manner (pulsing currents to go up or down in frequency) and list rise and fall times. For example, the ON Semi MCH12140 datasheet lists a worst-case 20-80% rise/fall time of 350 ps. How do I relate this to the bandwidth of FM demodulation I can perform using this device?


texts: Why parallel diodes on the output of a switch-mode?

texts:
I am looking at buck-boost converters on the Texas Instruments design tool, and multiple of these topologies have parallel diodes on the output. I cannot see any reason to do this.

Can anyone explain the purpose of paralleling D4 and D2 on the output?


texts: What is the function of switches in optical panel encoders?

texts:
I want to use optical encoder in my design.

In the datasheet of the optical encoder, pin2 and pin3 are used as switches.

Could you please explain how these switches work and how to use them?


texts:
I've got two USB computer mice, one with a defect click button and one with a defect USB plug. Would there any issue if I simply cut them open and soldered together the mouse part of one with the USB plug from the other? Or the USB plug from any old USB cable, for that matter.
They're both USB-A and not USB3. I know that there's a length limit for USB to get timing to work. Would a so-so solder job affect that? Could there be any other electronics in the plug part that differs between them?


texts: Is there a term for when a component desolders itself from the circuit?

texts: When a chip heats up too much it could desolder itself from the circuit. Is there a technical term for that?


texts:
I've recently aqquire a board which have an embedded PIC32MX460F256L of a project and working on. Nonetheless I'm not being able to connect to connect the MCU to my desktop even when I used MPLAB ide.

When I received the board I've been told that with only the USB cable connecting directly to the computer I'ld be able to flash the MCU. I also have the microhip driver for the MCU but shen I try to install it in windows 10 it gives me a signature error.

I know the MCU is wirking because everytime I connect it to the laptop it makes the sound, nonetheless I can't see it either in the device manager when its plugged in, therefore I think it should be a driver issue.

Does anyone is having this issue and is not being able to flash a pic or is it another way to flash the PIC32MX460F256L?


texts:
I'd like to run some tests by using 4-20mA sensors outputs, by somehow connecting them to my PC (and eventually run some analysis on the collected data).

I'm looking for a converter (that can perhaps be plugged in via USB), or some other interface method to my PC / Laptop.

Any suggestions?


texts:
I recently stripped a motor out of an old 2887-z gaf dual-8 mm projector. I'm not even sure if the motor AC or DC, although I suspect its a brush less ac motor. Unfortunately, I disposed of the connections between the chord and motor without analyzing what they did to the power - although I was under the impression they didn't do much.

I've included images of the motor - there's a large transformer built around the motor.

Q: How do I determine the motor's power needs and characteristics so that I can buy a power supply?

motor images
http://imgur.com/a/i1Z5c

user guide
http://www.atsrentals.com/docs/8mm-Projector-Manual.pdf

other:
the motor is very pre-internet age so I am unable to locate specs. but I thought I shoud mention there is a serial number "846-542" paint stamped onto the secondary winding and a "J" "R" stamped on either side of the motor.


texts: Does a DC motor that needs 100V require a battery that outputs 100V?

texts:
I'm trying to build a large drone.  The motor/motors I have selected all need a voltage of 100V to run. I got that number from this site:
https://www.alibaba.com/product-detail/T-MOTOR-62-inch-propeller-Matt_62532907503.html?spm=a27aq.15005574.7694076370/01_1091_1_1.71.faf557760dGHiO
With the thrust I require for the length of time I need, I need a battery/batteries with at least 160000mAh.
However I have been unable to find batteries that have a voltage of 100V. Most LiPo batteries I have come across only have a rating of 5-7, or 12 volts. So does the battery have to match the motor voltage?


texts:
Voltage-controlled current sources (VCCS) can be used when we need to model a device or any part having voltage as input and current as output. Same is the case for voltage-controlled voltage sources (VCVS).

Now, what should be my strategy when I want to model some device in ORCAD PSPICE having the output as capacitor or carrier concentration other than voltage and current?


texts: How difficult is to reverse engineer a IC Die?

texts: Can anyone tell me how difficult, time consuming and expensive is to reverse all layers of a die ? Say a die from a recent model SoC Processor IC found in smartphone devices such as the Qualcomm Snapdragon SoC IC ? Also is it possible to de-cap safely an IC using a houshold kitchen microwave ?


texts: How could you detect a microphone attached to a smartphone?

texts:
I've a circuit that makes sounds through an a standard audio jack (3.5mm) and I would like to connect it to a smartphone (let's say iPhone).

When I connect it to an iPhone, it will be detected as headphones, so it would listen not only to my circuit but also on the iPhones built-in mic.
If I take my jack and connect it to a microphone - it would detect a HeadSet connection and then listen only on the audio jack mic input.
If I substitute the microphone with a resistor - it loses that detection and goes back to headphones (my assumption was it detects resistance. probably was wrong).

Any ideas how a smartphone would detect a microphone connected and how that could be simulated?

Many thanks!


texts: I have a hardware setup where I am trying to null the input offset voltage of an op-amp using an I2C digital potentiometer. The op-amp inputs are shorted and I am measuring the output using an NI Data Acquisition card. Depending on the measured ouput, i want to adjust the offset nulling using the digi pot. I am under pressure to put together a routine to carry out this calibration procedure so I am wondering if anyone has ever done something similar and would be willing to share a pseudo code snippet of how they implemented it.


texts: Off line 3V3 power supply with 3V3 LDO without a transformer

texts:
Attached is a schematics page from Microchip's development board. This question is only about the 3V3 power supply they use for powering their PIC circuit.
Can someone minimize this schematic to the bare 3V3 power supply? Maybe mark the necessary components with color or list them in a text. I would like to be able to build just the 3V3 power supply without the rest of the circuit, to power a simple PIC circuit with blinking LED. Mind you, I have other solution working, I just wanted to really understand the Microchip's solution, which looks simpler then mine.
I want to learn from this, how this supply works. Specifically, I do not clearly see how the LDO ground gets returned back to 230VAC main. How does the Q5 FET even opens (where the gate voltage comes from)?
Thank you for taking time to explain this. I am sure I am missing some crucial detail here.


texts:
What is the input impedance of a typical MCU ADC? In this case I'm working with a PIC24FJ64GA004. I don't need high speed sampling - a maximum of 100 samples per second.

I wish to connect a resistive divider with a 100k resistor and a 10k resistor, so the impedance should be higher than 1M or else the impedance will start skewing the readings.


texts: How to measure positive, negative and inbetween currents

texts:
I am making a variable +12V / -12V bench power supply, where I will have 3 output pins: 0- -12VDC | GND | 0- +12VDC, where I want to measure all possible voltages and currents.
I will use voltmeters to measure potentials between: -12V and GND, GND and +12V, -12V and +12V; but I got stuck here, how to measure same currents.

I want to be shown at all time the current between GND and -12V, -12V and +12V & GND and +12V, but don't know how to wire the ammeters here.

Red resistor is between 0 and +12V;
Blue resistor is between 0 and -12V;
Black resistor is between -12V and +12V.


texts: How can I make a half-duplex UART to TTL converter for communicating to a servo with a HC04 and a HC126?

texts:
I have been trying to configure this circuit for some amount of time.
I am using a HC04 chip and a HC126 chip.
The HC04 is an inverter chip. The HC126 is a buffer gate. I found that for the servo connection, I can set up the schematic like so:

The Linux SBC I am using handles GPIO pins with 3.3V. I have a GPIO pin in use, a UART (TX/RX) connected, and those three pins are tied to a logic level shifter.
I am also using a Micro AnyVolt. This is being used to handle the 12V of the battery supply to the Dynamixel Servo for powering the servo and all while stepping down the voltage to the HC04 and HC126.
I have all my unused pins tied to GND. Direction_Port on this schematic a GPIO Pin on my SBC.
My questions are these:

How can I make this schematic work or should I take another route for UART communication from my SBC to a Half-Duplex TTL line on my Servo?
and...
Is this schematic a good schematic to use to handle these chips for use with a GPIO and UART from a SBC to TTL line on the Servo of choice?

I have a normal servo with three pins: http://www.robotis.us/ax-12a/
One pin is GND, one pin is 5v logic, and the other pin is a Half-Duplex TTL (TX/RX) Data Pin.
So, I am expecting to see the Dynamixel SDK on my Linux SBC (BBB) with 3.3v Logic to send and receive specific communications. The Micro AnyVolt handles the 5v logic to the Dynamixel from the 12v supply. The Micro AnyVolt also handles the powering of the HC04/126.
https://github.com/ROBOTIS-GIT/DynamixelSDK/blob/master/python/tests/protocol1_0/read_write.py
This link provides the Python3 example I am trying to run from the command line.
I was able to compile the source in Python3 and C so far. Anyway, w/ Dynamixel Servos, there are two types of protocols, i.e. 1 and 2. With my AX-12A Servo, I use the protocol 1 structured sections.
...
I have changed the port to "/dev/ttyS2" onboard my BBB.
The logic level shifter handles my 3.3v to 5v conversion. I think this may get closer to what is going on for your ideas to become added here. Also, Direction_Port goes to a GPIO, TX_Data goes to RX, and RX_Data goes to TX on the SBC.
The software states that I successfully change the baudrate and successfully open the port. The issues lie here:
[TxRxResult] There is no status packet!

This basically means that the Dynamixel is not sending out the required feedback. I think I need a separate program to run the GPIO HIGH/LOW but I am not sure exactly how to perform this action within their SDK.
Anyway...let me try one more thing. The TTL and GND connections to the Dynamixel Servo (AX-12A) might need to be swapped. I have not had any correct info. regarding the connection at the servo and the below schematic. I will test and get back to you.
Here is a simplistic edit:

Okay...I have to admit something. I should have asked this question in software engineering because of the DynamixelSDK that I came across and now that I know it is mostly software related, and taken back a bit, I should have not posted this effort or concern under my account. I apologize to anyone who read over it and wanted to supply support. Anyway, thank you for your guidance and help.


texts: Why are thyristor stacks hung from the ceiling?

texts: The Wikipedia article on thyristors as well as the one on valve halls mentions that thyristor stacks in HVDC applications can be hung from the ceiling or supported by insulators mounted on the floor. What is the reason for hanging them from the ceiling? Is it simply as the article states: to better survive earthquakes? Is there some electrical benefit given the high voltages present in the stacks? Why are mercury arc rectifiers generally mounted on the floor?


texts:
Schematic below is a current sensing circuit, Rs is 35u sensing resistor and current I1 is bi-directional. I am confused on why diode D2 makes this circuit a full rectifier.

Schematic:

Simulation results on Rs and output D2 (N_HALF):


texts:
This is one of questions our prof gave to students in recent years and im preparing myself for this exam.

What is Common Mode and differential Mode gain of this Cmos diff Amp inverter?

i understand that Q1 and Q2 with Q1l and Q2l are making a differential amplifier with active load. but what is Q5 ? is that a current source ? if so why its Gate voltage comes from N1.

also the output is connected to a Cmos inverter,  in digital this makes sense but here what if input of Cmos inverter is not either zero or vdd but vdd/2 ? isn't it going to also amplify the output in that range making the amplifier non-linear ?


texts: Is De0-Nano an alternative to Arduino/RaspberryPi?

texts:
Arduino and Raspberry Pi are touted as ideal programming boards for beginners and hobbyists. Could De0-Nano fit in that role, too?

What does Arduino or RaspberryPi have that De0-Nano does not?


texts:
I am a student EE major working on a control algorithm for a 3 phase sensored BLDC motor. Currently the motor is running well. I'm currently pursuing fault condition safety software for the motor. One possible fault that could occur is an invalid state read in for the hall effect sensors.

If the hall effect sensors read in 000 or 111 that means either one of the hall effect sensor's is shorted (111) or one is disconnected (000). My question derives from how to respond (in my control software) to a condition such as this?

Obviously if a hall effect sensor has gone corrupt (short / disconnected) I need to stop the motor from commutating. However, I'm worried that if this invalid state is caused by a fluke then I would not want to force the motor to stop immediately.

My current thoughts would be to just increment a counter each time an invalid state gets read in, then if 10 invalid reads come in consecutively I would stop the motor for good.

Thoughts? Am I crazy to think that hall effect sensor inputs straight from the motor could randomly be incorrect?

The more I think about this "issue" the more I'm leaning towards trusting the hall effect sensor data absolutely. If a random bit were to flip in the transmission the commutation pattern wouldn't be correct...

Thanks


texts: Solenoid Getting Hot and Not Functioning Properly

texts:
Please forgive my ignorance on this schematic.  I am new to using relays and solenoids so my diagram may be a bit inaccurate.

I am attempting to control a DC solenoid with the GPIO pins from a Raspberry Pi.  The solenoid and other components are connected according to this schematic:

I am using the following components:

Raspberry Pi 3
12V DC battery
diode
Relay SPDT Sealed
N-Channel MOSFET 60V 30A
12V Solenoid

I am not sure that I have the relay pins labeled correctly in the schematic but this picture of the relay I am using illustrates which pins are connected to the other components and corresponds to the pins on the schematic:

The relay documentation can be found here.

I also have an indicator light attached to one of the other GPIO pins to determine when the signal is supplied to the circuit in order to open the solenoid.  When I run the script to open the solenoid, the indicator light is on the solenoid does open but when it is off it seems like the solenoid is not completely closed as a little bit of water is leaking out.  In addition, my understanding was that this solenoid would open when voltage was supplied (normally closed).  However, when I put a voltmeter on the circuit in place of the solenoid the voltage jumps to 12V when the indicator light is closed. The current in the circuit when running is ~560mA.  I also noticed the solenoid getting hot when hooked up.

Is there something I am missing here that would help me understand why the solenoid seems to be partially closed?  Also, I am concerned about the heat as well.

After considering comments below, I am wondering if I could simply use this design to solve the problem with out the use of a relay.


texts: Regulate 9VDC@7A PSU output down to 3 to 7.5 vdc at a 1Hz sine wave rate

texts:
First post here. What would be a simple way to take the output of a  switching 9vdc 7Amp PSU and produce a slow 1Hz sine type wave DC voltage that varies between 3vdc minimum and 7.5vdc maximum? Is this even possible?

This will be used to do a final brush seating on small Hobby DC Motors that have been repaired or rebuilt.

They will draw between 1-5amps depending on voltage applied and the current state of the brush seating.

I'm trying to make this more automatic instead of doing the adjusting manually like I am doing it now. I have hobby level electronics skills, and already have several TIP122's, 2N3055's or LM338's if they would help.


texts: Near field magnetic & electric wave impedance formulas

texts:
I am looking for the exact formulas for the impedance of an electric and magnetic wave in the near field region.

We have some approximates:

Zwe≈ 1 / (ω * ε0 *r)

Zwm≈  (ω * µ0 *r)

where r is the distance, ω is the angular frequency, ε0 vacuum permittivity,  µ0 vacuum permeability

However these formulas are only approximations, and I believe the accurate formula involves complex numbers.

I could not find the full formula for this, I was hoping somebody here would know it.


texts:
I want to make a schematic of this board.
Can anyone tell me how?


texts: Confused by voltmeter reading in DC parallel circuit problem

texts:
I am a beginner and have been doing some circuit problems from a book.
However I am confused about this one:

simulate this circuit – Schematic created using CircuitLab

Question:

Assume a 9V battery and all reisistors are the same value.
What is the voltage drop across

A and B?
A and C?
B and C?

Answer:

is 4.5 V. I understand this one.
is 6V. This is fine as well.
is 1.5 V. I don't get it.

The book simply says to do 6.5 - 4.5 = 1.5 but provides no explanation why.

I made the circuit and 1.5V is correct. (Incidentally it is -1.5V if you move point C one resistor to the right.)

What is the actual path of the electrons in this case?

Do they go from point B, through R1 (+4.5V) then "backwards" through R3 (-3V) to get a reading of 1.5?

Or does the voltmeter allow them to take a shortcut, avoiding R1?

What is really happening?

I have searched for an answer but cannot find a similar circuit anywhere else.

Thank you


texts: The best way to wind copper wire around rod for lowest resistance

texts:
So I have wound 200m copper wire around a rod which gives me 180 Ω, previously I got only ~80 Ω. Both of them were randomly shuffled and the first attempt was on bigger in diameter rod. How to make magnetic fields do not interfere with each other as least as possible?

If you need any more data just say so. I will edit.

Wire Lenght 200m.
Current type: AC.


texts: Why do we need to synchronise asynchronous inputs in FSM?

texts:
I have been newly learning digital electronics. I know that there are gates which perform logic functions, I learned about RS-Latch, D-Latch and Master-Slave-D-Flip-Flop. Now that I can perform logic functions and store states, I can create a Finite-State-Machine (for example traffic light). In class we talked about this particular traffic light example and there was a discussion about what problems arise, if we would add a start/stop button (signal to traffic light that a pedestrian is waiting for green light).

Conclusion was, that this button would be an asynchronous input we need to put an flip flop before the state machine so this input can be first synchronised.

What I don't understand is, what is the problem with the asynchronous inputs? Why do we need to synchronise it? And why would a flip flop in front of the state machine or the back help with synchronising? I read trough several articles, talking about "metastability" but I still don't understand

Thanks a lot


texts: Dividing negative voltage source with three cables - What should one do with GND?

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I have a sensor with an output between (-10 V, +10 V) and three analog out cables: Sensor(+), Sensor(-) and Sensor(GND). I want to scale down the signal to (-2 V, +2 V) and feed it into an ADC. I understand how to implement a voltage divider when scaling a positive voltage signal with two cables (Vin and GND). However I am not sure how to do it in this case with three cables.

On the one hand I imagine it should be possible to scale-down each end individually and probe them with the ADC

On the other hand, wouldn't the previous case imply that I am scaling down twice? So this might be correct instead:

However the  2nd circuit would not be measuring the voltage difference between +V and -V, while this one would. However the GND cable is not being used at all

Which circuit is right?


texts: The precision of internal voltage reference in PIC

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I am designing some circuit with PIC16F18345 and I need some voltage reference (±0.5% or better). I can add some external reference or use built-in internal voltage reference in that MCU (that means simpler design and saved 1 IO pin).
What is the precision of that voltage reference? I am not able to find this info anywhere.

Datasheet:
http://ww1.microchip.com/downloads/en/DeviceDoc/40001795C.pdf


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I have the following diagram of a  HD44780U LCD controller

What is the difference between CGRAM and CGROM.

What is DDRAM for ?

Where are the customised characters stored ?

What does it happen when I send an instruction vs a data stream on DB0-DB7 pins ?


texts: Should it be possible to read values from automotive sender units with an Arduino?

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There are after-market sensors you can get for cars, for example, reading the oil temperature. You basically screw a sensor in and it has a little sender that goes to an electronic gauge.

Would it be possible to instead run these cables to an Arduino and infer the same information? I imagine so, but how would it be done? A lot of experimenting or would it be relatively straightforward?

I want to have a custom interface for this information combined with a Raspberry Pi and the auxiliary video input to a car stereo's display.


texts: dsPIC30F: 10-bit ADC. What happens after the bit DONE is set?

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Documentation on the 10-bit ADC gives numerous samples. But none of these samples explain in clear what happens and what should the software do once the DONE bit is set.

Let's consider the section 17.16.1 Sampling and Converting a Single Channel Multiple Times. It is the most simple. Documentation gives a very nice chart:

So, what happens after the DONE and ADIF signals are set? It is to the right, outside of this chart.

Is it right understanding that module with continue its work filling
and refilling the buffer (assuming that software will not do anything)?
Will the DONE signal be reset shortly
after it was set, when the 17-th conversion will start?
If the answer to the first question is true, this means that software has very short time (maybe just a few instruction depending on the system clock speed) when the value in the ADCBUF0 will be overwritten and lost. Is that correct understanding?

How should I modify the setup described in this section if I want ADC to grab 16 samples and stop? After that I will process the interrupt and start a new ADC session later when it will be the right time to do that.