texts: PWM DC Motors with different gear ratios

texts: I have two dc motors, 9V, but each have different gear ratios. I would like to synchronize their rpm using pwm. Is there a way of calculating the duty cycle I need to make the one with a smaller gear ratio slower?


texts: Crossing independent domain clocks (slow to fast)

texts:
I have 2 time domain clocks (completely independent) and a bit stream (single bit)

The first clocks is at 12.29 MHz .

I want to asynchronously reclock it to a second time domain.

Meta stability is solved using 2 flipflops (better 3?).
For data loss , I understood that I need the second clock to be at least twice the speed of the first clock (so 24.6MHz).

Using the above, can I expect 100% reliability ?


texts:
I'm working my way through Bowick's RF Circuit Design. In the resonant circuit chapter he does a great job of describing how component Q affects circuit Q, and how loaded Q works. There, you set the bandwidth of a band pass filter by deliberately changing its quality.

But in the filter chapter describing filter prototypes, the design procedure is quite different. First you select a normalized prototype based on the attenuation and passband ripple needed. Then you transform if needed, then scale. But the component Q criteria are left at this table:

The lower the component Q, the wider the bandwidth and the shallower the rolloff attenuation. However, it was not explained by exactly how much. To calculate total Q, I can presume that I could take the Q of the last shunt segment and combine it with the Q of the second last series segment using Qtot = 1/(1/Q1+1/Q2). But I'm not sure how to then combine that with the next shunt Q. Or I could try to transform all resistance out of the filter into one series resistor. Not sure which approach to take. So that's my first question.

My other questions are:

Where do these figures in the table above for minimum Q come from?
How does component Q affect  the actual Butterworth parameters?
How do I adjust the Butterworth parameters to account for component Q, rather than just having to follow the general guidelines above?
If an ideal Butterworth has no resistance, how is it possible to have a wide bandwidth?


texts: Can I keep half of an addressable led strip on?

texts: If I bought some WS2811B led strips (300). if I ran them across a room is it possible to make the first 150 LEDs or so stay on, and the last 150 off?


texts:
Today power went down in my house and although my computer is hooked on a very powerful UPS AKA backup power soure, it shut down as soon as the power was off and started back up seconds later. The reason was that the inverter in the UPS didnt start fast enough to supply power so this few milisecond delay was enough to turn it off.

Although i am not very experienced with electronics, i happend to have a chunky 1.14μF 2100kv 50-60hz capacitor laying arround and i  thought that i could possibly hook it up between the UPS and the computer just to fill in this slight gap.
Below is a picture of the capacitor:

Unfortunately i cant calculate the power drawn by the UPS since it varies depending on the usage. (its quite a powerful machine)

My question -or more specifically- my questions are:
 1. Will it serve its purpose?
 2. Is it safe if done properly?
And another question not closely related to this thread,
How can i calculate how long a capacitor can provide power for given the voltage and current drawn?

Thanks in advance.


texts: How does a Dual-Antenna WiFi router work better in terms of signal strength?

texts:
I have observed that WiFi routers with 2 antennas have a better coverage than a router with a single antenna. How does that work out?

I can clearly make out that the second antenna is definitely not a repeater kind of thing, or is it?

Absolutely related: How does having more antenna help in a networking router

The answer in the question sited above speaks of Noise cancellation. I can correlate that to Efficiency in terms of reception quality, packet loss, etc, but not to the signal strength.


texts: Loop current of the loop containing a current source

texts:
I am currently studying circuit analysis methods and there is one thing regarding the Loop Current Method I do not fully understand.

Let us take a look on the loop current sketched below:

As far as I understand, in this method we will assign each loop a uniform current and then calculate the overall voltage drop in each of the loops.

What I do not understand is: why does the loop current of a loop containing a current source have to be equal to that particular current. In this example, we must say that IL1 = Ig.

I understand that the current source will maintain a constant current between the two nodes it was connected to and that the voltage between those nodes does not depend on the current, that is, does not satisfy the equation U = RI, but why couldn't the expression for this loop current be:

0 + IL2*R4 + (R4+R5)IL1 = 0

assuming that the upper loop is IL3 and the bottom left one IL2 (IL1 and IL2 go through the resistor R4 in the same direction). The zero on the left hand side comes from the fact that there are no mutual resistors for loops 1 and 3, and the one on the right side is there because there are no voltage sources in loop 1.

EDIT: The first step I did was to create a circuit tree (if that is how it is called), by merging every node in the circuit without making a loop. Also, the branch containing the current source must not be included in the tree. Every loop consisting of the branches that are included in the tree and only one branch that isn't is an independent loop.

There are multiple ways of making a circuit tree, this is only one of them.


texts:
I bought a computer for a person in which, when delivered, the video card (Gigabyte Nvidia GTX 570) never gave output. The only way the display got basic VESA output was when I moved the card into in the PCIe 8x slot (was on PCIe 16x) but of course blue screen on drivers install.

The warranty was void since they detected burned capacitors and excess of solder.

I've noticed in the pics from warranty that some components were burned and others where some solder was melted.
You can see the pics here: http://imgur.com/a/CVy3y

How can this damage occur? My guesses are:

Overvoltage: I think I would have noticed any behavior/sound of it; also, the PSU should block this.
Wrong overclock configuration that led to heating the GPU.
Video card was defective on arrival in some way.


texts: "Tagging" Data traveling over serial port?

texts:
If I'm reading data from multiple channels (UART) of a microprocessor, but I want it to be continuously read, I imagine the logical thing to do would be to cycle through the channels and output data, while, similarly, cycling through the inputs on the software-side of the receiving computer and reading them and inputting them into separate buffers. But, I find it hard to believe that the computer and the microprocessor send and and receive data in perfect synchronicity, thus it would make sense that each data might be attached to some sort of "tag" to identify its source channel as it comes through to the computer.

How would one go about doing that, because I imagine attaching tags as I surmised above would slow down performance on the computer's ability to read a large volume of signals as it then has to parse the data for these tags? This is just a logical guess on my part as to how this effect would be achieved though, so maybe there is a better way to do this that is totally different.


texts: Data Shift problem for Q6 & Q7 (starting from Q0) while using the 4094 I.C with a Micro-controller

texts:
Currently I am using a PIC micro-controller with a 4094 IC but when I WANT to shift data to Q6 or Q7 it shifts it on Q0 & Q1 and when I shift it to Q0 & Q1 it turns on Q6 & Q7. So I do not have problems operating the output I want but why is this happening?

Below are the codes:

    void ShiftData(unsigned char Data)
{
        unsigned char i;
//        OUTEN=1;
        LED_A = 0;  //STROBE = 0;
        LED_C = 0;  //DISPCLK = 0;

        LED_B = 0;  //DISPDATA = 0;

        for(i = 0;i < 8;i++)
            {
                if(Data & 0x01)
                   LED_B = 1;   //DISPDATA = 1;
                else
                   LED_B = 0;   //DISPDATA = 0;

                LED_C = 1;  //DISPCLK = 1;
                NOP();
                NOP();
                NOP();
                NOP();
                NOP();
                NOP();
                NOP();
                NOP();
                LED_C = 0;  //DISPCLK = 0;
                Data = Data >> 1;
            }

        LED_A = 1;  //STROBE = 1;
        NOP();
        NOP();
        NOP();
        NOP();
        NOP();
        NOP();
        NOP();
        NOP();

        LED_A = 0;  //STROBE = 0;
//      OUTEN=0;
}

What I perform is:

Reg_Data = 0x00;
Reg_Data |= (1 << 1);
ShiftData(Reg_Data);

This should turn Q1 high but it turns Q6 high.

Alternately:

Reg_Data = 0x00;
Reg_Data |= (1 << 0);
ShiftData(Reg_Data);

This action turns Q0 High rather than Q7.

Help would greatly be appreciated!

Link to 4094 I.C:
https://assets.nexperia.com/documents/data-sheet/HEF4094B.pdf


texts: How much AC Power will a DC powered (50 W DC) Device need if we operate it will an AC to DC Converter?

texts:
This question has been bothering me since my university days but I never got a clear answer for it. At the university I was told that if a device need 50Watts DC then it will need fairly less Watts in AC(if we design a AC to DC converter for it).

For example I have a device which needs 50 W DC i.e
Power = 20 Volts (DC) x 2.5 Ampere (DC) = 50 Watts DC

If I create an AC to DC Converter of normally attainable efficiency how much AC watts will this device need to operate.


texts:
Is anyone aware of a good linux program for drawing automation schematics?
Not PCB design, circuit simulation and fine electronics. Industrial automation.

Example:

I looked at a couple of different EDA applications, but did not find any functionality for multiple sheets in a single schematic. I will also need cross-reference symbols to handle nets/symbols that go across multiple sheets.

Perhaps someone knows about an EDA application with multiple sheets and good scripting capabilities to create the cross-reference system?

Solution:
I ended up using gschem with some custom scripts for cross-references and titleblock stuff. They can be found here.


texts:
In the figure below is shown the dynamic behavior of an SCR in terms of its current during switch off.
I'm interested in calculating the maximum reverse current (iR in the plot).
The parameters that I know are the common one that datasheet usually report: Vrrm, Irrm, trr..

What I don't know is actually Qrr that would have been useful.


texts: How is this multiplexer built? (on a logic gate plan)

texts:
I was watching this CrashChourse CS video (7:41) to learn about RAM.

Real quick, this is the definition of a multiplexer: (source)

MY QUESTION

Since the Multiplexer only has a single output, how can I ever map each of the 16 combinatons of 4-bit input to each of the 16 columns as seen on the image above? It seems impossible as, again, it only got one output?!


texts: Help understanding resistor placement in 741 voltage reference circuit

texts:
I want to build a low-voltage detection circuit, and while I found many online, I think I prefer the 741-based ones as they seem simple enough - i.e. circuits such as these:

source

source

My question is that in both of these circuits, there is an "ambiguous" connection to a resistor (i.e. the 100k in the first one, and the 10k in the second one) - how am I supposed to connect it, as it looks like 3 wires are going into a resistor (1 wire in the middle?)


texts: What is the difference between IQRn 0 and IRQn 1?

texts:
I am using STM32CubeMX to program my chip. Essentially I have a timer that i am trying to set to one ms, and every time that timer reaches a ms I want to toggle a pin. My question is that does it matter if my code goes in the IQRn 0 or IRQn 1 section of the TIM2_IRQHandler?

void TIM2_IRQHandler(void)
{
  /* USER CODE BEGIN TIM2_IRQn 0 */

  /* USER CODE END TIM2_IRQn 0 */
  HAL_TIM_IRQHandler(&htim2);
  /* USER CODE BEGIN TIM2_IRQn 1 */
      if(toggle_pin == 0)
      {
        HAL_GPIO_WritePin(TEST_PIN_GPIO_Port, TEST_PIN_Pin, GPIO_PIN_SET);
        toggle_pin = 1;
      }
      else
      {
        HAL_GPIO_WritePin(TEST_PIN_GPIO_Port, TEST_PIN_Pin, GPIO_PIN_RESET);
        toggle_pin = 0;
      }
  /* USER CODE END TIM2_IRQn 1 */
}


texts: ESD protection for OpAmp inputs and outputs

texts:
The following circuit is a preamplifier that we are currently using. In real practice, we do not have the photodiode connecting with OpAmp directly on board. Instead, the photodiode is connected with the OpAmp through a connector.

The input and output of the OpAmp are both connectors which will be exposed to user connections. Recently I am studying issues on ESD. Then I think the input and output of the OpAmp shall be prone to ESD. I am using a ADA4062.

How to design to protect the OpAmp input from ESD?
Can I use some RC filters shown in the diagram, before the input of the OpAmp?
How to design to protect the OpAmp output from ESD?

EDIT 2015-12-28

To be clearer, here comes updates on system information:

The capacitance of the photodiode is smaller than 1pF, which is to be designed working at 1GHz bandwidth.
However, we will only use the low-frequency region, which is below 100kHz.
The linearity of the system is very important, which means the second order, third order distortions are disastrous to the system. It is preferred that the total distortion is below -70dB.

simulate this circuit – Schematic created using CircuitLab


texts: stm32 CDC USB - Unknown device (error code 43)

texts:
I face a problem with making custom PCB with STM32F103C8T6 FS CDC but whole story looked like this.

I've made small test app using CubeMX and IAR on cheap PC from china with same MCU - in terminal on windows I was able to receive data. BTW I used 8MHz XTAL, 1k5 pull up to 3.3 on DP line no serial resistors.
On custom board same code (which I can download to MCU without any problem) and
I'm getting Unknown Device in HW Manager on win7.

Same MCU same application and clocks and two different behaviors - what I'm doing wrong?


texts: Boost regulator from 3V to 14V; then two LDO to make a +5/-5 power supply?

texts:
I am designing a mixed signal circuit and I need +5/-5 dual supply for my opamps. Could the following configuration work, else what are my alternatives?

 Li battery 3V--> Boost regulator--> 14V-->14 to 7---> Linear reg(e.g.,7805)--->+5V
 (coin or LiPo)                             0 to 7---->Linear reg(e.g.,7905)--->-5V
 The 7V would be the actual ground throughout the circuit for both analog and digital

Given that, I have a microcontroller and other digital components in the circuit, I will be drawing more current from the positive supply than I would be sinking from the negative supply, so a net positive current is drawn from the boost regulator (OR is there something wrong with this logic?)

Would this scheme work? Any other suggestions for achieving the same results? Any specific battery specs or otherwise I need to worry about?


texts: E-core current transformer: How do I wind main primary conductor?

texts:
I'm designing a current transformer. I know that current transformer are usually built by using toroidal cores. But I want to use an E-core instead. There are two reasons for preferring E-core over toroidal. One reason is, I have found some E-cores which are cheaper than toroidal ones. The other one is, winding an E-core by hand is so much easier than winding a toroidal core.

But, how do pass primary conductor through an E-core? I searched it in Google, but couldn't find any result. So, I can't make sure of what to do exactly, but my instinct says that it should be done as in the image below (the main conductor follows the red path).

Can you tell me how to do it?


texts: How to reduce 46v to 24v for a solenoid valve

texts:
I seem to have bought the wrong solenoid valve. It takes 24v (I assume AC), and I just tested the supply and it is 46vac. The valve obviously works at that voltage, but it sometimes makes a loud groaning noise, and I worry about damaging it. At this point, I can't return the valve, so I want to figure out how hard it would be to reduce the voltage of the input.
The valve listing is here, but I'll list the electrical specs below:

Input Voltage: 24V
Current Draw: 160mA
Power Consumption: 3.84 Watts

Can I just put a resistor on there? If so, what specs should the resistor have?


texts: Why is this BJT not going into saturation?

texts:
I built a project based off of this description, but substituted an STGP7NC60HD IGBT.  See the schematic below (Note: IGBT symbol doesn't exist as of this post, so JFET was substituted).  The coil and points breaker are external to the circuit.

I soldered everything together and tested it on an old car that has its coil and points configured like this circuit (points connect primary to ground).  The car cranked, but no ignition.

I took the circuit inside, hooked it up a 12V power supply, and substituted a 12V DC motor for the coil.  Not a perfect substitute, but what I had at hand and my power supply wouldn't be able to handle power required to run the coil.  I found that when I disconnected the lead that hooks up to the points from ground (the equivalent of the points breaker opening), the motor didn't stop as expected. I took the following readings with the equivalent of the points open:

Base voltage of the BJT: .638V (note that the data sheet lists base emitter saturation voltage at 1.8V).

Collector of the BJT/gate of the IGBT: 12.26V

IGBT collector: 1V

12V DC rail: 12.38V

This means \$i_b=(12.38-.638)/47k = .25mA\$.  With a current gain of 100 (EDIT: this is not the correct value! Thanks Tut!), I calculated \$i_c=25mA\$, and \$ v_c = (12.38-25m*10k)=-237V\$, and this being much more than the rail could handle would put the device well into saturation mode.

But these readings indicate the BJT transistor didn't go into saturation.  I'm a bit lost, and don't understand why the base emitter voltage didn't go to 1.8V, and why the BJT didn't go into saturation.  My solid state knowledge/skills/experience never was very good, and it's been rusting for 5+ years now.  Can someone help me understand what I'm missing?

EDIT: I just bench tested the device with a 100, then 40, then 20 ohm resistor as load with pretty much the same result: \$V_{be}=.63V\$, so the BJT isn't going into saturation and shutting the IGBT off.

simulate this circuit – Schematic created using CircuitLab


texts: How is electricity from the power supply turned into stored bits of data?

texts:
I'm not an engineer, I'm curious how this happens. I've googled a little, but it seems I don't know what question to ask. I'm looking for in depth content detailing the process by which electricity on the wire is stored as values.

I know binary. I get that current is on, a 1, or true, while no current is off, a 0 or false.


texts:
I know that by the principle of superposition that $$V_{\text{out}-1}=(1+R_1/R_g)V_{1}-(R_1/R_g)V_{2}$$
$$V_{\text{out}-2}=(1+R_1/R_g)V_{2}-(R_1/R_g)V_{1}$$
Could someone please explain the concept behind this derivation.  Could this have been derived without knowing the principle of superposition?


texts:
I'm currently trying to understand designing complex cmos circuits for logical expressions. I came across many examples but all of them feature expressions, which are negated: $$f=\overline { A+(BC) } $$ or the whole expression has no negation parts: $$f=A+BC$$
For both cases I know how to design these circuits but I couldn't find any examples with negation parts and non negation parts, like: $$f=A+\overline { B } C$$

Is it possible to design such a circuit with cmos and if so how can I do it?


texts: gilbert cell mixer implementation and balun

texts:
1) How do I interface LC balun with mixer using differential current RF+ and RF- input signals ?

2) How should I deal with the load impedance (RL) for LO+ and LO- which is almost infinite because it is mosfet gate ?


texts:
I read this document from ON Semi, it said the optocoupler features a parasitic capacitor, does this Copto can find in the datasheet? I read the VO617A datasheet, but I don't find any capacitor value in the datasheet.

and I see the figure below.

There are my questions:
1.) Can I use this figure to get the parasitic capacitor value?
2.) I try to use this figure to calculate the capacitor value f=1/(2piRL*C), when the RL=100, the C=7.9nF, when the RL=1000, the C=2.65nF. Does that mean the parasitic capacitor is not a constant value?
3.) In the datasheet, the coupling capacitance is Copto?


texts: How signifigant of an issue is Gold Embrittlement?

texts:
I have heard about gold embrittlement but have not seen any data regarding failure rates, or how long before solder joints are at risk of failing. We use an ENIG finish on all our boards and I'm wondering if gold embrittlement should be something we should be concerned with regarding short and/or long term reliability. If so what precautions can be taken to avoid it?

Thanks.

Update:

It looks like, according to IPC-610:

"Gold shall be removed from solder terminals plated with 2.5 um [0.0984 mil] or greater gold thickness."

also, it looks like an acceptable method to remove the gold is to tin the surface and then remove the tinning with solder wick - once being enough to leach out the gold.

Also found this graph:

I still dont know if this would be worthwhile though. Does anyone have experience with gold embrittlement or lack thereof?

Cheers


texts:
I'm trying to adjust the PWM frequency and dead time on an SG3525. I'm not using it on a switching circuit yet, just trying to adjust proper ct, rt, rd values.
I've created a combination(ct=1nF, rt=23k, rd=3R) and everything was ok until I decided to increase the dead time.
I just increased the rd value to have higher dead time but when I increased it, IC started to work weird and provided unusual PWMs at output like attachment:

These PWM waveforms are actually imposible for this IC, because each PWM has maximum %50 duty cycle on the SG3525.  As you can see on scope, the yellow PWM is more than %90 duty cycle here. PWM outputs has same duty cycle on 3525 normally but here it's also different.
This is the first time something like this happened to me with the SG3525.
Any ideas about what's happening to IC when I increase the RD?
Here is the datasheet.


texts: Why is there a separate Floating Point Units in some micro controllers

texts:
I would like to know why there is a separate FPU peripheral in some high end micro-controllers even if the small end 8 bit controllers can perform float calculations on their own.

I tried experimenting with a float division on a pic 18 controller which does not have an FPU (Majority of 8 bit family does not have an FPU)and found out by debugging(ICD 3) that  @48 mhz clock   a simple division of float variable takes minimum 800+ clock cycles.

  I don't have a controller with FPU on my side as of now to test with.But still I
  would like to know what effective difference and edge does the addition of a FPU
  make or provide .


texts: Using a small heatsink with a high power LED (50W)

texts:
Description

I want to use a 50 Watt LED like this one (42mm*40mm)

The space to integrate this component is limited. I have only 55mm*55mm*30mm in total.
So the LED + Heatsink size must not be higher than that.

I found one that is just with these dimensions: 55mm*55mm*13mm

However the description says Fit High Power Led 5 watt 10 watt.

The second option is to use a passive 40mm*40mm*20mm heatsink like this

The LED will be put in a tight spot: plastic under and metal (don't know which one) on the sides.

2cm away from the back (from the heatsink) would be some wires.

I can leave the top cover of my device open in order for the heat to go away, no problem for that.

Questions

Is one of these two heatsink appropriate in my case? Which one would be better? I have no idea how much heat produces an LED like this

What is the risk of using such heatsink with a 50 Watt LED? Could the LED blow up? Burn?

Is it possible the sheath of the wires on the back melt?


texts:
A centrifugal pump requires 21.6 hp to flow 350 gpm at 2800 rpm with a 230/460V, 40 hp, 2-pole (3600 rpm) motor.  The VFD available can operate up to a 25 hp motor at 230V, with a maximum output of 68 amps.  Would this work, provided the pump flow requires no more than 25 hp?  The VFD frequency would be limited to 48Hz to limit the motor speed.

This would be a temporary measure, pending a new 460V power supply and new 40 hp VFD.


texts: When connecting several AXI4-Lite slaves, must I use some kind of interconnect? If it is guaranteed that each slave decodes a distinct set of addresses, is it possible that the slaves would set their data outputs to high-z and be connected together?


texts: BMS for Li-Po with balancing and protection

texts:
I want to build a robot based on Raspberry Pi with Raspberry Camera. It will use tracked car chassis to move around my flat. I'd decided to use 3-cells Li-Po battery to power this robot (because of requirement of high current for chassis motors) but it's very inconvenient to extract battery and use my IMax B6 charger to charge batteries. So I want to implement some kind of BMS which will allow me to charge battery without extraction and even without turning Raspberry Pi off.

I've found such open source solution for Li-ion batteries http://libre.solar/devices/bms-5s/ but unfortunately I can't find something like this for Li-Po batteries (I've found bq25708 chip which does exactly what I want but there are no open source power management projects for Li-Po batteries). I've found such boards on aliexpress https://aliexpress.com/item/6A-3S-12V-18650-Lithium-Battery-Protection-Board-3-Packs-Li-ion-11-1V-12-6V/32821150469.html but as it is said in a description this board for Li-Ion chemistry.

So what is the best decision in this situation? Should I use Li-ion batteries instead? Is there some solutions for Li-Po batteries? Should I use some special chip from TI or ST or maybe there is some open source project based on avr/stm32? Why BMS for Li-Po chemistry are so unpopular? May be I just can't google it?


texts: How many cubic feet can 1 peltier cool efficiently?

texts:
I want to build a mini fridge, however, I want to build it a bigger than the ones showed in the tutorials I've watched.

For that I assume I need more than one peltier to cool it.

However, for that I need to know what is the maximum amount of space 1 peltier is valid for.

I want to make it 6 cubic feet.

How many peltiers would I need for that, and how much voltage do I need to power all of them?

EDIT:
I plan on using acrylic panels as its outside, laced with Auto Car Heat Sound Deadener Insulation and styrofoam
 on the inside, including gaskets wherever needed to make sure no air escapes from the box.

In order to cool the heat sinks from the hot side I want to use several 12cm computer fans.

The average temperature in the room the coolbox will be in is about 30 degrees Celcius.

I need the cooling inside to average at 0-3 degrees celcius at most.

My plan is to use more than one cooler, in order for easier cooling as both will work at half the power, and thus will be less noisy.


texts: How can voltage actually exist/change if electricity can't actually speed up or slow down?

texts:
PLEASE NOTE:  No this question does not already have an answer at the link posted above. This question was closed by individuals who didn't read it, nor the comments underneath it.

I am new to hardware/electronics and am coming from a software background. I'm ashamed to say, but I've never fully understood the difference between volts and amps. If you Google "volts vs amps" you'll get a plethora of articles/links/blogs/videos that all try to explain the difference, but IMHO they actually do a really lousy job at it, and here's why:

Most analogies to volts/amps come in one of several very-similar forms:

Water flowing through a stream; or
Cars traveling on a highway during rush hour
etc.

Let's take the "flowing water" analogy; it is typically explained that:

Volts: the pressure of the water traveling through the stream; and
Amps: how much water is traveling through the stream

The problem here (I believe) is that electricity is always traveling at a constant speed (speed of light), regardless of how much power you're generating, or regardless of the gauge size of the wire you're using. Unlike the speed of water traveling through a stream, the speed of electricity is constant and cannot be sped up or slowed down (I understand in the context of theoretical physics this is probably not true, but we're talking consumer electronics here).

With flowing water, if we increase the size of the stream (its width or depth), then not only will more water pass through any given point (volume), but the speed of the water will also increase. This is given to us by the Hagen-Poiseuille equation.

So I've always had this mental hang up with trying to understand exactly what volts are, because the analogies that are always used just don't stack up.

It makes sense that amps can be changed by changing the gauge of the wire the current is traveling through; this is the same as increasing the volume of the stream; but...

To me, it doesn't make sense that volts should ever be capable of changing, because volts are essentially the speed/pressure of the water passing through the stream, but electricity can't actually speed up or slow down! This is where the analogies break down for me, and is the root of my confusion.

Can someone please help me understand how electricity can have different levels of "pressure" or "potential", which is what volts are said to be, in a way that makes sense?

Again, if electricity travels at a constant speed, and we make the wire bigger, I understand that we will get more volume/amps. But I don't understand how this will create more "pressure" since the bigger wire will not actually make the electricity speed up.


texts: How do I convert 24 V from a car battery to 5 V @ 1A?

texts: I need to  make a phone charger using the batteries as source in my boat. Also i would also like to know the heat dissipation of the circuit as i need to use it for a minimum of 30 minutes.


texts: PC to Arduino wireless link (low latency)

texts:
I want to build a robot car with an camera gimbal on top of it. This robot and gimbal should be controlled wireless by a gamepad and the head tracking of an Oculus Rift. As it is with the Oculus Rift, it has to have a low latency. Now I am searching a wireless solution to send the control bytes (about 5 bytes with max. 1000Hz) from a computer to an Arduino. The latency has to be as short as possible (1-3 ms). I already searched and I found these RF systems:

RFM22B
nRF24L01+ and nRF24LU1+
RF Link 433Mhz

Is there a better solution? Or which of the RF systems above is the best for my case?


texts:
What does negative turns ratio in the transformer mean?
Some simulation software offers negative turns ratio, but in reality it does not exist.
So what does it mean?


texts:
I've seen lots of examples of avalanche diode (or other reverse PN junctions) white noise sources, and before I go out and build it, I've got some questions about the design. First, my first cut at it:

simulate this circuit – Schematic created using CircuitLab

The 20v source is going to be a boost converter - that's straightforward. I've tried simulating this circuit, but unfortunately, the simulators to which I have access don't seem to properly simulate the avalanche noise this circuit is intended to make. All I get is that the first NOT gate oscillates regularly. So questions:

Does the second self-biased inverter stage serve a purpose? The design I was looking at for this particular case used no less than 3 stages, but I can't see the point of more than 1.
Some other sources have suggested C1 (obviously not 0F) as a way of reducing the "wrong" kind of noise. Does this make sense?
Is the amplitude of the output of Q2 going to vary enough to influence the first NOT stage after AC coupling? Seems like that's really the crux of the biscuit. My take is that the first NOT gate is JUST on the verge (or past it?) of instability and that the avalanche source is influencing that instability towards chaos rather than away.
The MMBT3904 datasheet I've read (from Diodes inc) says that the absolute max E-B voltage is 6V and that the breakdown E-B voltage is also 6V. Am I just setting Q1 up to be blown repeatedly?

EDIT:

I threw this exact circuit together on a breadboard this afternoon, and it appears to work correctly. I get a very irregular frequency square wave (something on the order of high hundreds of kHz, but it's hard to be precise) on the output. When the output is low, there are frequent, very brief upward spikes that get more frequent just before it changes. There are no such (downward) spikes when it's high. The NOT gate was a DIP MC74HC04, but I am going to attempt to actually build this with a 74LVC2G04. The output from one stage by itself is unsuitable, and adding a third (pure inverter) stage at the end appears to do nothing useful (but invert the signal).


texts:
I'm helping build this art installation that amounts to a large 16 x 16 pixel display. I settled on using 16 TI TLC5926 constant current driver chips chained together to give me direct drive to each LED. In retrospect I'm doubting myself and wondering if this was a heavy-handed approach.

If I had done "the usual" LED multiplexing approach (i.e. LEDs at row, column intersections, and application of persistence of vision techniques), I might have perhaps been able to pull this off with 32 "drive pins" (rather than 256), at the expense of more software complexity and less effective brightness.

In a Multiplexed Anode-Row Cathode-Column topology, the TLC5926 would seem well suited to driving the Columns (sinking current). What would be an analogous / complementary chip for driving the rows in a similar chainable shift-register interface, and able to source up to 120 mA per channel (to match the TLC5926's sink capability)?

To be clear, I don't need a high-side current source. I'm basically looking for a serially controllable and chainable high side switch (preferably 16-bit to match the TLC5926 on the low side). Trivially, this could be accomplished by using two 8-bit 74HC595 shift register to drive the gates of 16 discrete FETs, but I expect there is a more integrated way to accomplish this.


texts:
At work we have a alcove hidden from direct view with a wall covered in "standard" domestic microwave ovens (MO). You put in you food there and then you join your fellow colleges chatting; after a while you forget about your food: is it ready or is is not? You rise and walk the 20 m or so to check, either the oven has only been in use for a short time and the food is still cold or the oven been off for such long time that the food needs re-heating. It's a serious issue :-)

If there was a way to detect if the MOs was running or not, we could connect some raspberry pis or arduinos and build a display of some sort indicating which MO that is running or not and put that display visible from the dining area.

The question is how to detect of the MO are running or not?

To further complicate the question: we don't own the MOs, hence they cannot be altered, which leaves the cord and the power outlet to be used.

Then there is the issue with the magnetron at full effect I guess it operates constantly but lowering the effects turns it on or off.

When of MO are done, the lights are still on inside, hence drawing current; so I guess some sort of threshold combined with measurement over time...

There are roughly ~30 MO in the alcove so the cheaper solution the better.

Is this possible to solve at a reasonable price that doesn't involve hooking a arduino/rpi up to each and every MO?


texts:
I am working on Contiki's cc2530 port (customizing for my custom radio). I do not unserstand how can i make SLIP work with SPI?
 I understand that SLIP is similar to UART (it is UART without parity, what does this mean?), but how can i use it with SPI?


texts: In general i see there are so many vdd and vss pins in micro controllers.Is there any specific reason for that? why cannot we have a single vdd and vss pin?


texts: bldc regenerative braking, braking torque

texts:
I'm trying to figure out the braking torque calculation for a BLDC simulation.
Now if I'm looking at a datasheet I know the torque at a given rpm at acceleration.
If I brake with regenerative breaking is that the torque at a given rpm as at acceleration? Or can I get any braking torque with the controller?


texts: How can Kill-a-watt show .1A, 12VA, but 0 watts?

texts:
I'm trying to verify whether a 10W aquarium heater is failing.  It has a safety fuse that renders it permanently inoperable if it overheats by running unsubmerged, which is suspected in this case.  My Kill-a-watt reports .1A, 12VA, 120V, but 0W.  I thought I understood that positive VA or positive current and voltage should be inconsistent with 0 watts.  What am I misunderstanding?
UPDATE:

I can measure an LED lamp at 1 watt and a filter pump at 5 watts, so it's not that 10 watts is below measurement threshold -- and I wouldn't expect different thresholds for VA vs the corresponding watts.
It turns out the measurements with the heater plugged in are the same as with nothing plugged in.  So I'm convinced the heater is shot, but what is the meaning of the Kill-a-watt showing 12VA but 0 watts when nothing is plugged in?  Shouldn't 12VA and .1A at 120V correspond to roughly 10 watts?  .1A seems suspiciously high too for just running the Kill-a-watt, and i would expect them to have "tare"d out the Kill-a-watt's own draw.


texts:
Do the very thin wires of headphones have a name?
by headphone wires I mean the usually green, red and twisted ground cables, about 0.1 mm thick.


texts: Can the USB interface be used in real-time works

texts:
USB works similar to the Master and Slave architecture. There is an Host which is manage the bus as like a Master. There can be various "devices" which is managed by host like slaves. I wonder that whether USB can be used in real-time motion control or not. For a real-time job, you need an deterministic interface. USB working principle is similar to the Master & Slave architecture. So this means that USB completely deterministic solution, right? At most how much cycle time can be reached by USB ? What is the drawback of USB for real-time motion control?

Say a system consist of one Host and 16-devices. Devices can be servo-drives and a few sensors (encoders, gyros etc.). For instance, I want to send motion commands to these servo-drives and receive back sensors feedback through the same USB interface. I probably would like to see sub miliseconds cycle-time such as 500 uS (2kHz), 250 uS (4kHz). USB interface can handle the these requirements? I concern about the delay of USB. Is it deterministic or non-deterministic?


texts: Name of 4-conductor twinned headphone wire

texts:
I would like to get more serious about repairing headphones, as well as making my own extension cords ( as the ones you can buy tend to be pretty low quality, and I am tired of breaking).

The kind of cable I am looking for was the primary kind of cable used for headphones a while ago. [1] It is composed of four conductors. Sheathed in the insulation in pairs, with pairs of insulation bonded. You can split the insulation down the middle and and have two pairs of insulted wired ( each pair having two conductors )go to each speaker separately.

What is this cable called? ( A link to some such cable would be useful. )

[1] It seems that modern headphones mostly use three conductor cable. Or it seems that way to me. Possibly because I use behind the neck type headphones.


texts: Integrating an ethernet switch IC to custom pcb with mcu using RMII

texts:
I have a custom board with LPC1768. It has also PHY (LAN8720) in order to connect to LAN via RJ45. So far so good.

Now, I have to extend that custom PCB including Ethernet-switch-IC by a choice of mine. It must have 5 ports minimum and 10/100 only, not gigabit.

Furthermore, I like to connect LPC1768 directly with that Ethernet-switch on the same board rather than using external PHY (LAN8720). As it seems, RMII interface is for that business and LPC1768 supports that. But, I am not sure how to do that and if this is even possible straight forward.

I picked KSZ8795. It says there is Port5 can be configured as RMII interface.

My questions;

Can I directly connect LPC1768 to KSZ8795 using it's RMII interface (TXD0, TXD1, TXEN, RXD0, RXD1, CRS, RXER, MDIO, MDC, RESET, RMII_CLK)?
if I can connect the way I assumed, apparently a configuration is required to set RMII interface on KSZ8795. If there is, I must missed that in the datasheet. How can I configure KSZ8795?

I appreciate your inputs from now.


texts: ESD and equalizing static charge of sensitive ICs before handling and soldering

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When I'm handling an IC that is sensitive to ESD that comes packaged in an antistatic bag, do I nullify my ESD protection procedures if I peel back the cut-tape and dump out the IC into a plastic cup instead of dumping it directly onto the surface of my ESD mat?  Do I need to dump the IC out directly onto the surface of my ESD mat for it to equalize its static charge with me, my mat, and my soldering iron?

Assuming that the answer to the above is "yes", then does it make a difference if the pins of the IC touch the mat or not?  I'm guessing that if you dump an IC onto a ESD mat and the pins never touch, then the internal conduction pathways of the IC are still statically charged relative to my local earth ground, and that when I plop it onto my PCB for soldering the ground plane of the PCB has enough stray capacitance to allow an ESD discharge from the IC to the ground plane of the PCB (which has been earth-ground equalized prior to this by way of me touching an exposed ground plane pin ).

Is this a thing?  Do I need to worry about the stray capacitance of the PCB ground plane and differential static voltage between the PCB ground plane and IC being placed on it?


texts: Is there a small (6-pin) DIP I can use to generate multi-MHz squarewave clocks with an external crystal?

texts:
I'm building a circuit that I'd like to run at 8 MHz to begin with, but I want to be able to try it out at 10, 12, 16, 20, and, maybe, 25 MHz. I know that many microcontrollers have the ability to just plug a passive crystal into two pins and the µC will generate a square wave and pass it on to anything else it's connected to which needs a clock. What I'm wondering is if that functionality exists on its own in a nice, small package which will run at 5V. (I know I can build it using Schottky fast inverters and some capacitors and resistors, but I'd rather avoid all that external stuff if at all possible).

Alternatively, is there an easy way to generate a continuous range of frequencies of this magnitude (similar to what you can do with a 555 timer at lower frequencies)? I'm not too fussed about the frequency being particularly accurate, I'm pretty sure a 1% variability would be acceptable (2% seems like it's pushing it, but I'd certainly be willing to try it out)

Additionally, I've seen a suggestion to use a higher-frequency crystal and use a frequency divider to divide it by four. Is a T Flip-flop the best way to do that at these frequencies? (or, rather, two since one flip-flop is only going to halve the frequency). Does this advice make any sense given that I'm running this on a breadboard? (yes, I know, parasitic capacitance and all that, that's actually part of the reason I'm doing this experiment, I want to see the effect of this parasitic capacitance at the various frequencies and to see whether mounting the breadboard on a grounded copper plate makes any difference)


texts: Is it possible for electrolytic capacitor to develop a short in one way only?

texts:
I've got a 1 F electrolytic capacitor and it seems to have developed a short.

I never used it before and its brand new. It reads zero resistance only when I connect positive lead of my DMM to its negative lead and negative lead of my DMM to its positive lead. In the other direction, there's no short.


texts: Is the electric field in a wire constant?

texts:
If \$V=I\cdot R\$ according to Ohm's Law, that implies that \$\frac{\mathrm dV}{ \mathrm dx} = \frac{I \rho}A\$ across an infinitesimal length of conductor, which is constant at all points along the conductor since the current, resistivity, and area of the conductor are all constant.
\$\frac{\mathrm dV}{ \mathrm dx}\$ is also equal to the electric field, which I wouldn't think would be constant at all points along the conductor since E is a function of the distance from a source (e.g., the battery that the conductor is connected to), so I would think that E would change depending on the location of the conductor.  This change might be negligible for a short length of conductor, but over long lengths, I would expect it to be significant.

So why is the voltage gradient constant if the electric field is not?
Or is the electric field somehow constant at all points in the
conductor?


texts:
I am trying to implement a secondary battery in one of my projects. When the main battery (24V) dies, the 3.3V battery takes over and the system operates in limp mode (some emergency functions). I am planning to connect the batteries like this, as my system runs on 3.3V and the secondary battery I'm going to use is a LiFePO4 cell (3.2V nominal). This way, my secondary also gets charged (to a safe 3.3V) when main battery is available. My load is hardly 500 mA with full functioning, and 200mA in limp mode. Is there anything I'm missing here? Will the LDO be fine when mains battery is not present? I'm attaching LDO's functional diagram as well.

I checked the oring diode methods and LT's powerpath ICs, but I want the circuit to be as simple as possible. LT has supply issues as well in my country, so they have to be imported.

Thanks!


texts: Dynamic range given the THD [Spectrum Analyzer]

texts: Imagine that I have to measure the THD with an error less than 6%, given the first 40 harmonics. How do I know the dynamic range of the spectrum analyzer that I have to use?


texts: Does Molex SlimStack round cable jumper exist?

texts:
Today I learned the following connectors are a SlimStack plug and receptacle.

However, I only found flex cables jumpers, like this one. Is there a reason round cables don't exist for this sort of connector?

I would need something like that for a project, as flex cables are not as freely movable as round cables.


texts: When to put resistor on comparator input

texts:
I am using a open-collector output comparator (ROHM BA8391G) to enable a voltage regulator when Vin > 12V is detected (comparator output will be HIGH when Vin > 12VDC). Vin can be in the range of 12-28V. (Note that I am aware that in reality, the output will not go HIGH until Vin is ~13.4VDC)

I am using a voltage divider circuit to feed Vin to the non-inverting (+) input of the comparator and connecting the 3.3V supply directly to the inverting (-) input. I do not plan on using feedback since the Vin voltages will not be very granular.

simulate this circuit – Schematic created using CircuitLab

Does the 3.3V supply connection to the comparator need a series resistor to limit current? And more generically, when do the inputs need current limiting resistors?

I have seen some examples online that do not have a series resistor. Such as this TI design guide

However, the datasheet for the component says "Excessive input current will flow if a differential input voltage in excess of approximately 0.6V is applied between the input unless some limiting resistance is used." My interpretation of that is that if the difference between the inputs is >0.6V than there can be excessive current flow...? The largest possible difference between the two inputs is when Vin=28V; Vdiff = 3.7V

Here is the simplified schematic from the comparator's datasheet that I am using:


texts: Evaluation of multiple Wheatstone bridges using one instrumentation amplifier

texts:
I need to measure 8 different strain gauges.  I am thinking about using just one instrumentation amplifier to evaluate all Wheatstone bridges (because of the high price of instrumentation amplifiers.)

I could use relays, but they are too slow for me. It would be nice to switch in 10s of kHz.

Do you have any idea?


texts:
I am using a MAX3485 for modbus communication through UART between a device and a modbus slave.
What I want to achieve is to put my MAX3485 breakout into low-power shutdown mode when I put my device into deepsleep mode.

The wiring my MAX3485 breakout is as followed:

DI/RO => UART GPIO of my device
RE/DE => 2 distinct GPIO of my device
Vcc/Gnd => respectively 3.3V/GND of my device
A/B => to the A/B of my modbus slave that is powered by the 5V/GND of my device

From the MAX3485 dataeet, I can read:

  Low-Power Shutdown Mode (MAX3483/MAX3485/MAX3486/MAX3491)
  A low-power shutdown mode is initiated by bringing both RE high and DE low. The devices will not shut down unless both the driver and receiver are disabled (high impedance). In shutdown, the devices typically draw only 2nA of supply current.

Bringing RE high and DE low is not an issue but how to achieve: the driver and receiver are disabled (high impedance). ?

Thank you in advance,

Bnjroos


texts:
I've just started working with the Stellaris LM3S9B92 (Cortex M3). I have some problems understanding the SysCtlClockSet() function. On the Driverlib page 350 they say that:

  The use of the PLL is chosen with either SYSCTL_USE_PLL or SYSCTL_USE_OSC.

and after that, to use an external source I should use:

  SYSCTL_USE_OSC | SYSCTL_OSC_MAIN.   and for the PLL use SYSCTL_USE_PLL | SYSCTL_OSC_MAIN,

My question is, what's the difference between SYSCTL_USE_OSC and SYSCTL_USE_PLL? I found this example on the net, and the person is using both an external clock source and the PLL! What is considered as a clock source and what is ignored?

SysCtlClockSet(SYSCTL_SYSDIV_2|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);


texts: What type of solder should be used for attaching electrical wire to a large clamp (base wire will be screwed into clamp handle).  I am making a fractal wood burning device so current will be coming from a neon light transformer. Note specs on transformer: 10KV 10000V - Power 120V AC 50/60Hz.  I have solder for small electronic projects, but have been told such solder is not durable enough for this job.  Thanks, R.


texts:
I got this connector in a CIS sensor board

the connector is 18 pin , dimensions (around 5mm X 18 mm )

Here's some images for it the male & female


texts: Can I covert a 3.3v/5v USB TTL Serial device to 1.8v using a LM1117 1.8v regulator?

texts:
I have a HDD which has serial access but needs 1.8v TTL serial. I only have 3.3/5v serial devices. The standard PL2303, A UART Usbbee, and a generic serial adapter. The PL2303 & generic have 3v/gnd/txd/rxd/5v pins and the USBbee is pictured below.

I found some LM1117 regulators which can take in 3-12v and have 1.8v output.

Is there any way I can modify the generic adapters or the USBbee with the regulator to enable reading of 1.8v serial?


texts: Purpose of perfboards with pads all connected

texts:
A while ago I saw a protoboard with the pads all connected; at the time I thought it was a manufacturing glitch, but today I saw another one. I cannot think how these boards may be useful - any ideas?

Here they are:


texts: MOSFET reduces LED switching time - why and how to resolve

texts:
I am trying to drive an LED to rapidly (~10 ns) turn on, remain constant and turn off.

I have tested the LED with a pulse generator (1 ns switching and 5 V, 50 ohm output). A high speed detector is used to monitor the LED output. The resultant signal is shown in Figure 1. The layout is the top diagram in Figure 2.

Figure 1. Signals recorded, sources as per legend.

Figure 2. Schematic diagrams of systems used.

However I would like the LED to be brighter so have used a MOSFET to drive the LED, see bottom Figure 2. This does make the LED brighter but the rise time seems to be vastly increased. As well as the LED output I have also measured the voltage across the MOSFET (again Figure 1) it's fall time seems fast so the slow rise time does not seem to be attributable so the MOSFET switching time.

Any suggestions on why this occurs and how to resolve it? I have tried changing MOSFETs, with little effect.

EDIT: Lots to questions about the MOSFET and drive. I used the 50 ohm signal generator to drive the MOSFET gate. The MOSFET is a NDS351AN. The data sheet quotes a 1.3 nC gate charge. For a 5 V, 50 ohm drive I calculate this takes 13 ns to 'fill'. That is also why the MOSFET drain voltage is plotted - surely if the MOSFET switching time was an issue then the voltage would still be dropping?


texts: MPU-9150 (IMU) - what happens at fullscale range boundaries?

texts:
We're debating the use of the MPU-9150 IMU in an application. This IMU has a user settable full scale range for the accelerometer (e.g. 2g, 4g, etc) and gyroscope (200dps, 400dps, etc).

Suppose I set the values at 2g and 200dps - what happens at the boundaries of these ranges? Are the values ceiling/floored (i.e. an acceleration of 3g-4g results in 2g sent to back from the sensor), or do the values roll over?


texts:
Hello, I am learning about the Fourier Transform, and I can do the math, but I'm having trouble with the fundamental concepts. From my understanding, the Fourier transform allows us to see the frequency components of a time signal, with "peaks" in the graph corresponding to the frequency components.

However, I am not understanding the Fourier transform of a rectangular pulse. Its a sinc graph with a large peak at f = 0, and little peaks gradually fading out at higher frequencies. Can someone help explain the significance of the graph? For instance, why is there the large peak at f = 0? Why is there also not a peak at f = 1, wouldn't that be the frequency of the rectangular pulse?


texts:
definations

\$x(t)\$ is a function of time. Physically, it can be voltage, displacement, magnetization and so on. It can be real, complex, vectors or more fancy numbers.

\$C(t)\$ is the auto correlation function of \$x(t)\$ , defined as:

$$ C(t)=\langle x(t) x^*(0) \rangle := \lim_{T\rightarrow \infty}\frac{1}{T}\int_0^T x(t'+t) x^*(t') dt' \tag{1} $$

\$I(\omega)\$ is the spectrum of \$x(t)\$, it is the  Fourier transformation of \$C(t)\$, or it is the square  of Fourier transformation of \$x(t)\$. These two definition are equivalent  (apply convolution theorem):
$$ I(\omega)= \int_{-\infty}^{+\infty} C(t) e^{-i\omega t} dt \tag{2} $$

$$
I(\omega)=
\begin{vmatrix}
\int_{-\infty}^{+\infty} x(t) e^{-i\omega t} dt
\end{vmatrix}^2 \tag{3} $$

non-negativity of \$I(\omega)\$

We can show that, spectrum is non-negative:
$$
I(\omega)=
\begin{vmatrix}
\int_{-\infty}^{+\infty} x(t) e^{-i\omega t} dt
\end{vmatrix}^2 \geqslant  0
$$
And physically it makes sense, because \$I(\omega)\$ means the energy density within frequency range  \$[\omega , \omega+d\omega) \$.

Energy density shouldn't be negative.

Question (1): what function \$C(t)\$ makes its Fourier transform \$I(\omega)\$ non-negative?

In practice, definition equation (2) is used rather than equation (3).

\$C(t)\$ is the inverse Fourier tranform of non-negative function \$I(\omega)\$.

I know some basic law like this:
$$
\text{FT}[real,even]=real, even
$$
$$
\text{FT}[real,odd]=imag, odd
$$

I have no idea what should \$C(t)\$ be?
$$
\text{FT}[???]=real, non \ negative
$$
Understand the function class of \$C(t)\$ might help us solve Question (2), because later on, you will see, I'm doing a transformation to \$C(t)\$ (essentially it's a discretization), then perform Fourier transform. This discretization transformation might take \$C(t)\$ out of that class, therefore makes \$I(\omega)\$ no longer non-negative.

subtlety in numerics: \$I(\omega)\$ is no longer non-negative!

In numerical calculations, things become finite and discrete.

Equation (2) is modified to its numeric version:

$$
\int \xrightarrow{\text{numerics }} \sum
$$
$$
\qquad \quad t \xrightarrow{\text{numerics }} t_i \quad i=0,1,2,\cdots,L
$$

$$
\qquad \quad \omega \xrightarrow{\text{numerics }} \omega_n \quad n=0,1,2,\cdots,L
$$
Or, an alternate way to understand numerics is to keep the continues integration, but sample the function \$C(t)\$ discretely and finitely:
$$
C(t) \xrightarrow{numerics} C(t) \times \sum_{i=0}^{L-1} \delta(t-t_i)
$$

Under this change, \$I(\omega)\$ is no longer non-negative.

I did some experiments, those negative value of \$I(\omega)\$ can be as large as 10% of the positive peak value of \$I(\omega)\$. Adding window function makes things better, but still have 0.1% negative spectrum density.

Only in some commensurate case, \$I(\omega)\$ is non-negative.

Question (2): is there any natural way to make \$I(\omega)\$ non-negative, in numerics?

I find adding absolute value might help
$$I(\omega)\rightarrow |I(\omega)|$$
but don't see any reason, such as conservation of energy, so on

So, is there a natural way, to generate non-negative spectrum density, in numerics?


texts: Is a ground connection needed in between master and slave for this RS485/422 scenario?

texts:
I will work on a small project where an SSI-output data (angle data) of a rotary-encoder will be read by a micro-controller board (such as an Arduino board) and the micro-controller will then send this data to the PC via USB port. The distance between the encoder and the Arduino board/PC is not more than six meters.

These types of encoders use differential RS422/RS485 electrical interface, one pair for data and another pair for the clock as follows:

I made a drawing for this particular implementation and the signal chain will look like the following:

The controller board is sending the data to the PC via USB. The PC is earth grounded, meaning its motherboard all the way is connected to the chassis and then to the mains earth. The Arduino board is powered also through the USB.

U1 and U2 are two of these Differential Bus Transceivers(seems there is no galvanic isolation). So these transceivers will be powered by 5V supply or from the Arduno board's 5V terminal. The transceivers and the board will have common ground as depicted in the above diagram.

On the encoder end however the encoder can be powered by a separate power supply(at least that is the plan). In the diagram encoder ground(also the encoder supply ground) is floating wrt controller ground.

My questions are:

Should the encoder ground better be directly wired to the
controller ground via a dedicated wire?
If I use the same supply for the transceivers and the encoder, does
it matter the location of the power supply? Can the encoder's power supply be
remote to the encoder?
Where should be termination resistors?

I came across this article but it is rather confusing.

EDIT:

A more detailed diagram:


texts: CMOS (or CMOS compatible) shift register with latched open-drain outputs

texts:
I've been looking for a 3.3V compatible shift register (SIPO) with latched open-drain outputs. I've settled on a 74xx596 (not a '595!), but of all the 74xx CMOS series I've been looking at omit this one. Any idea on why? and if it's possible to get CMOS variants of these, because of the open-drain outputs?

Correction: I was getting confused between 595 and 596. 595 has tri-state outputs, 596 has open collector outputs.


texts: Frequency Characteristics of Low pass filter

texts:
Can anyone explain to me how I would find the frequency charactertics of a low pass filter?

How can I choose frequencies and find corresponding gains?

Is the frequency from the x-axis constant or variable?


texts: Only Provide Backup Power to One Device On Bus With Cap/Supercap

texts:
In a robotic system I am designing, the computer, motor controller and motor amplifier circuits all run on the same 24VDC power bus, which is provided by a switching power supply. Like below:

In the case of power supply failure, a capacitor/supercapacitor needs to provide backup power to the computer for 100 milliseconds, long enough for it to shut down properly. However, putting the capacitor in parallel with the computer also puts it in parallel with everything else on the bus, which means it would have to provide power to everything else for 100ms as well. This would require the cap/supercap to be prohibitively large.

What is the simplest change to the system such that the capacitor only provides power for the computer? I would really prefer to not need a separate power supply for the computer.

Edit after Josip's Suggestion

So something as simple as this will do? The computer does indeed have a DC-DC converter that can tolerate the diode voltage drop.


texts:
I have an analog signal in the range of -12v to +12v and I want to read it by a high resolution ADC. In other words, I do not want to use a resistance divider or other scaling methods such as op-amp circuits. I searched on google a lot and found the AD7732.

Now I have several related questions to the part:

Does anyone know other alternative ADC to choose? I need high resolution and ±12v range and speed is not important for me.
Does the AD7732 provide a direct reading of an analog input in the range of ±12V or only ±10V?
What do these sentences mean in the datasheet?

a. Overvoltage tolerant

b. Up to ±16.5 V not affecting adjacent channel

c. Up to ±50 V absolute maximum

d. The AD7732 is a high precision, high throughput analog front end.


texts: Finding gains from the summing different phases signals

texts:
I have four signal which are the same frequency and different phases.
It is possible to think
S1=1kHz sine,0 degree
S2=1kHz sine,30 degree shifted
S3=1kHz sine,60 degree shifted
S4=1kHz sine,90 degree shifted
All signals are connected to a summing circuit but gains are different.
S=S1*G1 + S2*G2 + S3*G3 + S4*G4
I need to find gains for each signals by analyzing the summing signal called S.
I can think of FFT, as far as I know, FFT gives f vs phase response. But all signals have same frequency. If all signals were different frequency, it maybe possible.
Is there a method for finding gains?

Equivalent circuit of the question is given as a circuit

When all gains are equal to each other

When only gain of S4 is 2, others are 1


texts: Line to Line or Line to Neutral voltage to calculate 3 phase power

texts: I am confused as to whether or not I should use the line to line voltage on a 3 phase motor or the line to neutral voltage to calculate power? Would someone please be able to fill me in, and possibly offer an explanation as to why? I do believe there are explanations explaining how the L-L and L-N voltages are related, but I need to know which one is used to calculate power. Thank you.


texts: What are the issues of using the analog output of a microcontroller to control a power MOSFET instead of using digital pins and PWM?

texts: Assuming that one just want to control a single power transistor or MOSFET with a microcontroller and that one is using an intermediary transistor(s) between the microcontroller and the power MOSFET to get the full range of allowed voltages to the gate. What are the issues of just using the analog output of a microcontroller to control a power transistor or MOSFET instead of using digital pins and PWM?


texts:
This is the step response of the power stage of a buck converter. I tried tuning it
when i added a proportional term, the rise time and settling time improved.So kept on increasing Kp and the response never started to oscillate.
I added ki and the steady state error vanished for ki=1 but the rise time and settling time worsened (from microsecond range it became in seconds)
Please any suggestions


texts:
The shown Capacitor-Diode (Cockroft-Walton) voltage multiplier, with \$n\$ capacitors stages (from ground to output) has a AC input with amplitude \$v_{in}\$ and a DC output \$v_{out}\$, with diodes with junction voltage \$v_{j}\$ which in steady state happens to be equal to:

$$v_{out}=2n(v_{in}-v_j)$$

This depends on the frequency of the input, which need to be some minimum value for converging to the previous approximated value.

Below is the simulation, with \$v_{in}=5V\$, \$v_{j}=0.5V\$ approx., \$n=4\$, \$C=1uF\$, \$f=10Hz\$, for the voltages through each component, plus the output voltage in magenta (greater value), estimating the value of \$v_{out}=36V\$.

But i am unclear on how to get an estimate for other values of \$C\$ and \$f\$.
Do somebody have a reference for this kind of circuit, and for calculating|estimating an expression for this frequency?


texts: Is an RJ45 / 8P8C connector a good way of connecting an Arduino to a simple device / circuit?

texts:
I'm creating a two-part, bass guitar-style MIDI controller, where the left hand plays a small fretboard which detects which frets are being played, and the right hand "plucks" strings (actually senses touch on four separate wires). The right-hand device contains an Arduino and the MIDI output port, while the left-hand device just consists of shift registers to serialize the data from its frets. The right-hand device (with the Arduino) currently communicates with the left-hand device via five wires (clock, latch and data for the shift registers plus 5V and ground).

My question:

What is the best way of connecting the two devices? I would like a detachable cable, so I'm imagining something like a D-sub connector on each device, or maybe an RJ45 or DIN. Ideally, I'd like it to be a fairly common type of cable so that it's not too expensive, and preferably something with a few extra pins in case I want to add some LEDs to the left-hand device. Also, the lighter the cable, the better, so that movement isn't restricted (this might rule out D-sub?).

EDIT - additional info, as requested (answering as best I can!):

The cable would be about a metre in length
The current is about 40mA
The code is currently running about 50,000 times per second (I think), but it doesn't really need to if that's going to affect the cable choice; 1,000 times per second would be fine
The shift registers are both 74HC165


texts:
some of the LED are on and most of the bulbs are off but i checked individual bulb status with multimeter and those bulbs are in off status are actuallyy good let me know  how to check why the bulbs are not ON
how to check the connectivity issue


texts:
I am trying to get an integer value from the ASCII char. I have a code like this:

String abc = "ABC";
char b = abc.charAt(1);
int b_ascii_value = ...

What should the last line be, in order for me to get the ASCII value of char b in int b_ascii_value?


texts:
I'm in high school computer engineering, and I'm experimenting with the 555 Timer chip on my own. I'm using the Electronic Experimenter Box.

Pin 8 is connected to +5V
Pin 1 connected to ground
LED1 is connected to Pin 3 and +5V
LED2 is connected to Pin 3 and ground

At first, LED1 is off and LED2 is on. When I connect pin 6 to +5V, LED1 turns on and LED2 turns off. When I connect pin 5 to +5V, LED1 turns off and LED2 turns on.

The weird thing is that when I touch pin 6 with only 1 end of a wire, it produces the same results as if I connected pin 6 to +5V. The other end isn't connected to anything either and I'm not touching any metallic part of the wire. What's going on here?


texts: I need to detect a break in 28 V DC voltage of the order of 100 micro seconds.If the circuit breaks for the above mentioned duration i should get a latched output.Can someone help me.


texts: 74LS04 (5 V) outputs 1.2 V to input pins

texts:
I have tree 74LS04 inverters and I cannot make them work.
When I connect device to power and ground and measure input voltage pin using multimeter, it read 1.2 V, which I expected to be 0.
The device sees it as 5V and inverts so my output is 0 instead of 1.
I tried all input pins, and they are all at 1.2 V; I've tried using two other devices from the same bulk and they all show the same behavior.

Is it a user or hardware error?


texts:
What safety measures can be taken when using a 1:1 isolation transformer in order to avoid electric shock even if
someone touches both ends of the secondary?
Would an insulation monitoring device be a safety measure in this case or does it only detect a leakage between primary and secondary?


texts: XBee power supply design using a Li-Po 3.7V battery

texts:
I'm currently designing the power supply for a device which uses XBee PRO S2C as a medium of communication. We are using a Lipo battery 3.7V 3500 mAh battery and TP4056 based battery charger.

The problem is:

XBee PRO S2C operating voltage is 2.6 to 3.7V. However when the lipo battery is fully charged, its voltage jumps to 4.2V and at this voltage the XBee does not operate and is damaged.

What can be the best option to reduce the Lipo battery supply to feed the XBee power?

I can use a PN diode or Schottky diode, but it works only if the battery voltage level is above 4.0V as it is consuming 0.7V as voltage drop (PN diode) and Schottky depends on current consumption.

The best option I found is using a LDO regulator of operating voltage at 3.0V and low drop out of 0.2V. Will this regulator work for the requirement I'm looking for?


texts: How to turn a wired dimmer into a wireless one?

texts:
I'm working on a personal project for residential automation. I want to make a wireless Arduino controlled dimmer. I followed this tutorial and I made my dimmer, but it's wired.

Below is the circuit and the schematics (pictures are from the tutorial linked above).

What changes should I make to that circuit so that it can be actuated wirelessly?


texts: Why does Nyquist plot only need loop gain but not the entire closed loop transfer function?

texts:
I was trying to compare a Bode plot and a Nyquist plot of the same system and realized that I was probably comparing apples to oranges

Bode plot is plotting the entire closed loop transfer function, whereas the Nyquist plot is only plotting the loop gain

Given the above system, the loop gain is defined as \$C(s) \times P(s)\$, whereas the closed loop transfer function is defined as $$\frac{1}{1+C(s) \times P(s)}$$

Why does Nyquist only care about the loop gain (but not the entire closed loop tf) and does it make sense to compare Bode with Nyquist?


texts: IEC 60079 Explosive Atmospheres Compliance

texts:
I'm wondering whether anyone has some experience with designing electronics for compliance to IEC 60079 Explosive Atmospheres. I have designed a device to be installed in silos facilities which are considered explosive atmospheres due to fine dust present in the air. I have been given IEC 60079-7 - Explosive Protection by increased safety "e" and told that the device must be proven to comply with it.

I have read IEC 60079-0 and 60079-7 and since the device does not contain heaters, luminaries, motors or transformers, most of it is not applicable. The device takes 9V DC and works at 5V DC, has no-burn fuses and Zener diodes for overvoltage protection and ESD devices against ESD discharges.

The two questions I have is whether anyone has any experience working within IEC 60079 to give me some examples of things to look out for to comply with this standard? Secondly, from reading 60079-0 section 29.3 it does not mention the possibility of using "increased safety e" in Group III (dust) atmospheres which confuses me - is increased safety e compatible with Group III dust atmospheres (i.e. can we implement increased safety for Group III devices or not?) I find the whole standard very confusing and sometimes ridiculous (apparently one of the tests I need to pass is a 1kg weight being dropped repeatedly onto the device!!!) . Long story short:
1) Any things to look out for or examples to follow to comply with IEC 60079?
2) Can a device implementing increased safety "e" be used in explosive dust atmospheres (Group III) or is safety to be achieved only through enclosure, encapsulation, intrinsic safety and pressurization?

Thanks, any tips on implementing IEC 60079 compliance is welcome.


texts: I know that if I want to create a powerful electromagnet, then I'd better put a ferromagnetic material inside the coil I build.  So I was wondering if the same applies in the inverse scenario, that is for a generator (I simply mean a coil where I induce electric current by moving a magnet around).  Does the insertion of a ferromagnetic material inside the coil increase the output current of the generator?


texts: Effects of double snubber for TRIAC on SSR?

texts:
I'm designing a PCB where an MCU has to command a TRIAC to drive a coil, when googling an schematic for an SSR, I came across 2 snubber designs, and while researching them this question: Triac snubber: Where to put current limiting phototriac resistor?
For what I gathered one design protects the optocoupler and the other protects the whole circuit but special care should be paid to the values of the components.
I was wondering if I could combine both approaches like so, or if some interaction that I'm unaware of between them will cause the circuit to not work properly?


texts: Controlling/Reading Hard Drive Brushless Motor w/ uC

texts:
I am working on creating a Hard Drive DJ similar to the other posting on this website, except that I want to drive the motor when the user isn't scratching on it. Multiple sources recommended using an ESC for this, but I have two main problems:

I would like to drive the motor forwards and backwards at various speeds. Is this possible with an ESC?
I have to have some sort of additional monitoring system for checking when a user starts playing with the spindle so that I can turn off the ESC and switch to monitoring EMF voltage levels with the ADC. Can you think of a good way to do this?

Also, do you know of a good datasheet or tutorial that describes the protocol for talking with an ESC from a microcontroller?

Thanks for the help!

EDIT: I found an instructable that used Hall EMF sensors and an L6234 driver chip. Would the L6234 better fit my needs over an ESC?


texts: Risks of charging an empty lead acid battery from 10 v

texts:
My 12 volt battery suddenly fell to 10v, is there a risk in recharging it?

In my boat i have a 80 Ah, 12 v, sealed and vented lead acid battery. Normally charged with a solar panel, with no load. Recently I added a Raspberry Pi and a router to monitor stuff. These has slowly been draining the battery during a week (solar could not keep up). Today it fell from 12.2v to 10.0v, see picture.

I am planning on recharging it. Some rumour on the interwebbs suggest recharging is a risk if a cell is dead (is it?). My charger is a mains connected CTEK multi us 3300, three stage charger. It started alright, delivering 13.4v to the circuit last I checked. Ought i stop it and get a new battery?

Pls ignore the units and titles in the pictures, its voltage. Web-frontend is work in progress :)


texts: Maintain state of GPIO pin across reboot

texts:
I have an ESP-12 soldered onto this adapter board. I am using NodeMCU Lua based firmware to code the logic.

I have scheduled node.restart to execute periodically. 1 of the GPIO pins is used to drive an external component using HIGH or LOW state. I can restore the GPIO state (HIGH/LOW) after node.restart but during restart GPIO state is undefined. I want to maintain that state especially if the state was HIGH.

1 approach I have in my mind is to have another micro-controller such as ATTinyX which is connected to ESP-12 via UART. ESP-12 can give a string/char to  ATTinyX to maintain the state (ESp-12 GPIO pin and ATTinyX pin is connected to the external component via an OR gate) and then go for a reboot. Once ESP-12 reboot is completed it can tell ATTinyX not to maintain the state because ESP-12 can maintain it now after the reboot.

This adds a bit of cost and components, is there a different way to achieve the same? I'm more on the software side, have less electronics knowledge. Any help is appreciated. Maybe it is similar to 1 bit memory which is set/reset by ESP-12, can I use a flip flop in this case?


texts: Trouble running 2 devices on a single 12VDC power source

texts:
I am using a dual connections to bring 12VDC power to both a video camera and a telescope mount.  Both devices are supplied by the same 12V 5A transformer and I am using a split VDC power cord that I bought from Amazon.

Both devices power on OK, but when I press a button to run positioning servomotors on the telescope, the camera cuts out.

I want to use a single transformer because of convenience.  FYI, both scope and camera come supplied with 12VDC 2A transformers.  Also using a Kill-a-Watt meter to measure each device separately, I determined that the resting amps for both were about 0.1A, and when I activate the motors the amps on the scope the amperage came up to 0.3A (the camera for its part is just a constant on video signal NTSC).

If there is some kind of amperage spike when I work the motors, is there a component that I can insert in my hookup that will keep the camera happy and prevent it from shutting off?


texts: What is the derivation for shot noise current?

texts:
The screenshot is taken from
Principles of Electronic Communications
by Louis E. Frenzel Jr.
I don't know where the formula came from and I tried searching, but couldn't seem to find any that I understand.


texts:
I have a circuit where there is a high level of noise at 100 kHz. For now, I'm not allowed to rework the circuit. I wanted to use a ferrite core, but when I look at the impedance characteristics chart, they all start from 300 kHz.
What would you recommend to start with?


texts: is it true that a computer will slow down after it is used for a long time?

texts:
Intel claims that a computer will become slower after it is used for a long time while the power consumption remains almost the same according to some media source.

At first I thought this was just marketing, but then some friend confirmed this is truly the case.  I can understand when bicycle is used for a long time the friction increases within the component, but that can be fixed anyways. What about the chips? Is the capacitor that takes longer to charge?

is this really the case or it is just marketing ?

source media material  if you can read Chinese

source transistor aging thanks to @sergio

clarification I am definitely not talking about software related stuff, otherwise wont post here.


texts: What is the purpose of adding a 300 ohm to 500 ohm resistor on the WS2812B Neopixel data line?

texts:
Adafruit's best practices for their Neopixel LED strings say:

  Place a 300 to 500 Ohm resistor between the Arduino data output pin and the input to the first NeoPixel.

What is the purpose of this optional but recommended resistor?


texts:
Hi I am working on STM32F103c8t6 MCU.I am trying to run sd card with spi wiht this library https://github.com/eziya/STM32_SPI_SDCARD do every thing like youtube video and my connection is like video https://www.youtube.com/watch?v=spVIZO-jbxE&t=321s.
This is a part of my cod:
send_uart("SD program ready....\r\n");

DSTATUS my_status = SD_disk_initialize(0);
 if(my_status == STA_NOINIT ){
    send_uart ("error in initializing SD CARD...\n");
 }else send_uart ("SD initializing OK...\n");

 if (my_status == STA_NODISK){
    send_uart ("No medium in the drive...\n");
 }
 if (my_status == STA_PROTECT){
    send_uart (" Write protected...\n");
 }

 fresult = f_mount(&fs, "0:", 1);
sprintf(buffer,"mounting SD CARD result:%d\n",fresult);
send_uart(buffer);

/* Create second file with read write access and open it */
fresult = f_open(&fil, "file2.txt", FA_CREATE_ALWAYS | FA_WRITE);
sprintf(buffer,"open SD CARD result:%d\n",fresult);
send_uart(buffer);

strcpy (buffer, "This is File2.txt, written using ...f_write... and it says Hello from
Controllerstech\n");
fresult = f_write(&fil, buffer, bufsize(buffer), &bw);
sprintf(buffer,"write SD CARD result:%d\n",fresult);
send_uart(buffer);

This is my response from uart:
SD program ready....
SD initializing OK...
mounting SD CARD result:1
open SD CARD result:1
write SD CARD result:9

return SD initializing OK.. but mounting SD CARD result:1 that means FR_DISK_ERR.
What is the problem ?
Iam using a SD module that has a 5v to 3v level shifter ic it can cuse problem?


texts:
I'm trying to use a 0.5V signal as a source.

I've wired a TL072CN as follow:

VCC+ to 11V
VCC- to GND
OUT2 to IN2-
IN2+ to 0.5V

The thing is when I measure the voltage on OUT2 I get 10V where I am expecting 0.5V.

I made some test and for different values of IN2+ I get the values under:

IN2+ = 0.5V : OUT2 = 10V
IN2+ = 1.0V : OUT2 = 1.3V
IN2+ = 3.0V : OUT2 = 3V
IN2+ = 5.0V : OUT2 = 5V

Do you have any idea where this effect could come from?

Edit: the schematic (I didn't know you could do this)

simulate this circuit – Schematic created using CircuitLab


texts: I am working on a system where I need to have 16 I2C devices on one bus. Due to data rates I need to run at 3.4 Mbit high speed mode. Are there any design/layout guidelines to help deal with a large number of slaves on a high-speed I2C bus? I am worried about reflections/stubs corrupting the signal too much as I've never used high-speed mode.


texts: Building an waveshaper device for my analog synth

texts:
I have a nice analog synthesizer that can do fancy sounds but has limited options in shaping the tone. It has two oscillators but they don't output sine waves (low pass filtering is not an option in many cases). It also lacks a high pass filter.

Because I'd like to get a specific waveform my idea is to build something like a guitar stomp box which gets fed with only a basic saw wave from the line output of my synthesizer. The box should split this signal into 3 paths:

input signal unchanged
input signal inverted and time delayed by a fixed value about 200 µs (would be nice to have a trimpot to vary the time from about 170–230 µs)
input signal's saw converted to a sine

The mix of such signals would give a waveform that's similar to one that can be heard in many techno tracks like e. g. "Satisfaction" by Benny Benassi

As my understanding of electric engineering is rather poor, can you tell me if this is a task that can be accomplished by beginner? Or would it be a too complex circuit requiring good calculation skills? The circuit should be capable of notes playing fundamental frequencies of down to about 32 Hz. The high cutoff of the synth is at about 20kHz (4 pole).

What I have found instructions for already is this 3 channel line level splitter circuit, and also this schematic for a saw to sine converter.

I guess path 2 could be made flipping its output terminals and using a 555 timer for the phase shift but don't know how to connect it.


texts: I am in need of a cheap DC motor that spins at a very low speed, preferably around 10-15rpm. As I am new to electrical engineering, I am not quite sure what to do. The only things I know of are expensive high torque slow motors, which I do not need. The only other idea I had was to make a circuit comprising of only a fast motor, battery, and potentiometer to slow down the motor. Would this work? Would I be able to get a over 1000 rpm motor down to 10rpm? Any feedback is appreciated. Thanks


texts: does Tera Term handle software flow control internally?

texts:
The title may be a little confusing but i'll explain the situation:

We have the following situation:

ARM MCU -> UART -> FTDI chip -> USB -> PC -> Tera Term terminal

The FTDI chip has built-in hard- and software to handle software flow control (XON/XOFF) internally. So i expect that when you select software flow control in Tera Term that it will send commands to the FTDI chip to enable flow control.

This means that Tera Term will not handle flow control itself but only enables/disables it on the FTDI chip by sending commands at initialization?

If so, is there a terminal program which do handle flow control on PC?

edit:

if you downvote, tell at least why.


texts: What kind of motor is used in electric room heater?

texts:
I did enough surfing to know about the kind of motors used in electric room heater, but not able to finalize. The principle seems like working of an induction motor with a electromagnetic stator but not sure.

I need to decide one such small motor working at 220v AC which will be able to drive a fan blade. Further, the motor should be moist and humidity proof along with protection from 1000w heating element in close vicinity. Any links or clarfication will be helpful.


texts:
My application is a PCB that has 2 different 100 pins connectors and has to be capable of arbitrarily connect each pin on the first connector to each pin of the second.
The signal going through the board, once ALL the connections are set, will be on only a subset (4) lines at any given time and will be in the DC-20 Hz band at a maximum of 1mA @ 0.1V. Cross-talk is not to be considered in this application.
I have to change the configuration once in a while and when I have to do that I can access the board manually. Active components (like MUXes) are discouraged because the signals are used for cryogenic 4-wires measures and the cost of suitable components quickly becomes inaccessible.
My original solutions have been:

Using a set of DIP SPST switches to build the connection matrix
Using a lot of small (16mm^2) push-down buttons to build the connection matrix

Both this solutions are expensive and space consuming. I was wondering if anyone knows a better component for this application.
The need for flexibility comes from the deployment environment of the application. Once (and if) this component is deployed in the field (South pole station) and set I won't have access to it for ~1y. So in 3 months I'll spend there I'll have to make sure everything works and there's the possibility I'll have to reroute some channels. The good old hydra cable soldering is not reliable, thus I was exploring other solutions.


texts: How to send a signal over long wire that is pulsing 9kV DC (agricultural electric fence)

texts:
Maybe a signals person can help me with this.

I'm looking at building a circuit that can be remotely controlled, using an electric fence as the comms bus or antenna.

I've seen this working in a production unit but
I don't have one of the units to disassemble.

The working unit allows a person at a location anywhere along the fence line to push the remote against the electric line and with a button, turn the fence unit on or off.

My question is what type of communication system is this likely to be using?

The fence's electric line is insulated from the posts, so in theory is a direct non-interrupted connection back to the unit.
The remote control is not earthed, but the fence unit is earthed as the unit operates as a single-wire earth return.
The distance from the unit may be 0-5 miles.
The typical fence pulse voltage is 7kV to 9kV once every 1.5 seconds, via capacitor discharge.


texts: How practical would a car booster using supercapacitors be?

texts:
Currently car boosters (a portable unit charged of an outlet and then connected to the car electrical system to start a car when the car battery is dead) typically use batteries - lead-acid, Li-Ion or LiFePO4. Over several years a battery in the booster will wear out.

Would it be practical to use a bank of supercapacitors that are more durable instead of a battery in a booster?


texts: How to determine correct voltage input on a multivoltage power-transformer?

texts:
I have an old tube radio that has multiple mains selector - 240V; 220V; 127V; 110V. The back-plate where the description how to set the selector correctly has gone missing. There are no markings anywhere that may give me additional clue. So how can I find the right position of the selector using tester.
I have measured the resistance of the primary coils as follows 21 OHM; 17 OHM; 11 OHM; 7 OHM


texts: How to avoid duplicate messages in a mesh network of mcus

texts:
I'm working on a project, where each pcb has a connector on every side, so you can connect these board in a grid. It's basically a mesh network of modules.

These modules need to communicate with each other. Since they are connected in an arbitrary way, there is no predictable path that we can relay on.
The grid can have missing modules, for example a 3x3 arrangement can have the middle module missing, or it can be two 2x2 grids connected with one module.

Messages can be either directly addressed to a node or be a broadcast.

My initial ideas:

I2C:
Length of the line would be pretty long (and pretty much undefined) it's not a good contender. Adding I2C drivers would increase the cost and complexity of the boards.
It would be too slow, because even if two adjacent modules would need high speed communication, it would hog down the whole system. There's also a danger of interference, especially in high speed mode, since because it's a mash network, there could be multiple paths to the same destinations.

UART:
Current solution of choice.
The MCU i'm using has 4 UART modules, so there is a dedicated UART peripheral for each edge of the board.
Each message is received by the MCU and processed. If that MCU was the target, it ends there, if not or it was a broadcast message, it sends it to the other 3 UART peripherals.

The problem:
Each message can get to each mcu multiple times, through multiple paths.
This causes severe problems: we don't no if we acted on a message, and because we don't know that we handled the message, it will be kept repeating, potentially indefinably.

The solutions:
I have not come up with a satisfactory solution yet, here are my ideas so far.

The first idea was to always send a message id, and each mcu will keep track of the last index received for each sender. This way we know which messages are new. We only forward and process messages that have a higher id than the last one.
This has downsides:
We need to send additional data with each message, the id.
Even if the id is a 32 bit number, which is not trivially small for each message, it may overflow. I'm not really sure how could that be handled, since receiving messages delayed on another path does not make that straight forward.
If a message is missing on the faster path, the previous message will be lost, since the counter is already incremented.
With a large number of nodes

An other solution is to store the last n message ids.
This has a downside of higher memory consumption, even just storing the last id for each sender address consumes relatively high amounts of memory, which is a scarce resource on an mcu. Also, if a module receives n+1 messages on a faster path, the messages coming from the slower path will be processed again.

My last idea is to create a map on startup.
This would involve each module sending a message to it's neighbors to has their address, after they've got all the addresses, each node should broadcast their neighbors. Filtering out duplicates is easy on the initial broadcast, since each sender should only send exactly one message. After that all nodes should have the same information, and using the same algorithm the should arrive at the same path, that makes sure that each module get's each message exactly once.
The downside is that this wrecks the ability to hotplug, although that was never a goal, so i don't mind loosing that. This is something that makes software update a bit trickier if the routing part is update, since unless they all run the exact same routing algorithm, some modules may not get the intended messages.

Is there something i'm missing? Is there an easier way to solve this?


texts:
I have a clock coming from a pin (GMI_CLK). It passes through a PLL and a new clock with 4 times the frequency is generated (Sys_CLK).
Now I need a pulse each time a rising edge of the original clock is detected (Sys_valid).

This works perfect in the simulation.
It has been coded as followed, but both ways generate errors during synthesis:

make_clkvalid: process(sys_clk)
    variable GMI_CLK_alt : std_logic;
begin
    if rising_edge(sys_clk) then
        if GMI_CLK = '1' and GMI_CLK_alt = '0' then
            Sys_valid <= '1';
        else
            Sys_valid <= '0';
        end if;

        GMI_CLK_alt := GMI_CLK;

    end if;
end process make_clkvalid;

  [Synth 8-5535] port  has illegal connections. It is illegal to have a port connected to an input buffer and other components. The following are the port connections :
  Input Buffer:
      Port I of instance clkin1_ibufg(IBUF) in module
  Other Components:
      Port I1 of instance i_43(LUT2) in module GMI_IO
      Port I1 of instance i_42(LUT2) in module GMI_IO
      Port D of instance GMI_CLK_alt_reg__0(FD) in module GMI_IO
      Port D of instance GMI_CLK_alt_reg(FD_1) in module GMI_IO

or like this:

make_clkvalid: process(GMI_CLK, Sys_clk)
begin
    if rising_edge(GMI_CLK) then
        Sys_valid <= '1';
    elsif falling_edge(Sys_clk) then
        Sys_valid <= '0';
    end if;
end process make_clkvalid;

  [Synth 8-27] else clause after check for clock not supported [GMI_IO.vhd":183]

How can I implement it for synthesis?


texts: 2 channel per circuit component election

texts: I was looking for some references for a level shifter connected to an intel edison and a found that they used a  74LVC(H)1T45 which have one channel per circuit. Then I found the same IC but with two channel per circuit (74LVC(H)2T45) and it have the same price. Considering that they use the same IC seven times (see link), Which criteria should I use for choosing the components? Is there an advantage of using one channel per circuit instead of two?


texts: What is the role of these two resistor please tell me that Why is first resistor 1 mega ohm the second is 100 k ? what formula has been used in this circuit to calculate first resistor and second one and also tell me what if both resistor are not used ? forgot to tell you the role of the circuit is to detect static electricity and magnetic field thank you.


texts:
I am a little confused by UART protocol. Can we map it to any layer in OSI model?
Certainly, it's not physical layer because it doesn't talk about voltage levels. Is it datalink layer?


texts:
I'm reading a tutorial and it is showing how to control a DC motor with Arduino board's micro controller. A DC motor is fed by a 9V battery and a transistor is controlling the PWM as in the figure I uploaded.

But the text is also mentioning to connect the grounds of Arduino board and 9V DC together. Why would it be recommended? It seems both Arduino's 5v and 9V battery are floating power supplies. Any ideas why they should be grounded together? Text says it is to obtain a common reference. But what happens if we do not connect them together since both are zero volts (ground)?


texts: I've been tasked with non-invasively measuring a 200 mA pulse signal through a wire. The solutions that come to mind are using a current clamp or a hall effect sensor. I don't need an accurate reading, I just need to sense when the pulse is there. Any suggestions?


texts:
I am trying to build this envelope follower:

And I haven't been able to get it to work. Without any inpt signal, I'm getting a constant voltage at pin 6 (just before the 1k resistor and LED) and even with an input signal, it stays the same. Can anyone help with this? I can find little information on the circuit so have no troubleshooting leads whatsoever.

FYI: This is for an audio circuit, using an instrument's input to alter PWM on a square wave oscillator


texts: Limit of the voltage and current of my electronic product for CE certification

texts:
I would like to know if there is a regulation that would require me to get my product certified because it uses to much power or uses a too high voltage.

My product uses an external adaptor AC-DC that transforms the standard AC (230V) into DC. I want to avoid to use an internal power adaptor because of the certification issue i would face.
This adaptor is CE certified.

If my product voltage usage is less than 30V and the power is about 100W.
I could in a different configuration go above 30V but always less than 50V.

Is there a voltage or power limit that inforce me to get my product certified?

Thank you


texts:
So, I picked up this book and am working through it by myself. I am a bit stuck on problem 1.6:

In the bottom you can see how I'm approaching this. I'm assuming the transmission cable goes across NY, and New Yorkers draw power from different points along the line. Since they each draw power at 115V, then the total voltage at the station, V@Station minimum, is 115 x 107V.

The power dissipated through one foot of cable is

(V@Station ^ 2) / Resistance per foot of cable

This worked out to be 2.645 x 1025W. And 1010W would be dissipated in 3.78 x 10-16 feet.

I haven't calculated the temperature because I don't know how to.

The last part of the question comments on these strange  results and asks for a resolution to this problem. I'm guessing that, since power rises non linearly with voltage, we reduce the V@Station by the use of transformers in order to reduce power dissipation through the transmission cable.

Is this approach and the answer correct? Please add your own thoughts and point me in the right direction if I'm wrong.


texts: Are large pulsed currents the most deadly type of electric shock?

texts:
As opposed to sustained electric shock via DC or AC?

I might be wrong, but when people are killed by electrocution it is usually due to a large current of very short duration passing through their bodies. And perhaps the electronics stack exchange is the wrong place to discuss something so macabre (if it is please direct me to the appropriate community), but I am asking this question in regards to the Electric chair. Could the electric chair be made more lethally efficient by using a high voltage Marx generator delivering a very large pulse of current into the executee, killing them instantly instead of having to deliver multiple shocks until they're deceased?


texts: Control of transistor as switch at power up and power down

texts:
I need to replace a physical switch with a transistor. I have a 12V supply which is always on, and i have a 12V control signal.

I need some way of generating a short pulse on both the power up of the 12V control signal and the power down of the control signal. It must be a short pulse (to replicate a short button press <1s >500ms).

I looked at 555 monostable timer circuits but they need to see high-low-high. Where as I can provide only high-low and low-high.

Can anyone provide any hints on possible ICs or circuits to achieve this please?


texts: I bought these RGB flood lights cause I liked the LEDs I saw in them and I was wondering what kind they are so I can just buy the LEDs and not the whole flood light.