texts:
When I pet my cat, and then touch her on the nose, I get a little shock. Sometimes, when she walks up to something, her nose sparks and she jumps back and puffs out. I was wondering how I might go about measuring the capacitance of my cat.

So how many micro-farads does my cat have? I don't think I can just attach the black thing on the multimeter to her tail and then touch the red side to her nose as in this wikihow article. Neither the wiki article on Body capacitance nor this stack exchange question on the same topic tell me anything about measuring.

I have an I2C capsense chip for my Arduino, but that just seems to throw out randomish numbers between 200 and a couple of thousand, and I'm not sure what to do with those numbers even if there was any repeatability to them.

Would it be possible to create a strap on display for my cat that would show "current charge" for my cat on a bright orange LED grid? Or do I necessarily need to have a reference voltage (my understanding of electricity is that voltage is always relative, does this apply for static electricity as well?)

Thanks in advance,

Tim

EDIT: While Russell McMahon's answer in theory seems to work, I don't think his method is as easy to implement as George Herold's. Both answers do seem to answer the immediate question as posed in the title. However, neither is entirely complete. They both hinge on the requirement of having a fully charged cat. But how do we know how many times to pat our cats before they are fully charged.

It is vital to also be able to measure the charge in real time, as per JRE's response in order to set a foundation for Herold's or McMahon's methods. Using JRE's technique, we can charge the cat until the charge stops rising, THEN measure the cat's capacitance.

Ideally, if we are to verify the potential for petting power as the purrfect post-fosil fuel energy source we will need reliable real time measurement of the cat's stored milliwatt hours as well as purrcentage charge and charge stored purr pat.


texts:
For a 300 MW power plant, 14.5 MJ / kWh of heating capacity must be provided. For this you can use coal with a heating value (hW) of 29 MJ / kg and a price (P) of 35 € / t or gas with a calorific value of 36 MJ / m3 and one
Price of 90 € / 1,000 m3.

What is the hourly cost (KB) for these fuels?

This is a question from school. I dont understand how 14.5 MJ / kWh could be possible? I can shorten this to 14.5 k / h. This make no sense?


texts:
I have a circuit meant to manage a shutter (or a shutter motor to be more precise). The motor has two power lines - depending on which power line one connects power, it moves up or down.

I designed the following circuit to operate the shutter:

RY1 and RY2 are operated via a uC / Mosfets.

I now have the problem that the SSR (RY2) does not turn off even though there is no more current flowing through its control pins (voltage ~20mV, current <1uA). The SSR only turns off when the shutter reaches a final position (fully open or fully closed) - then the motor stops automatically, hence draws no more current on the 230VAC line, and the SSR then stops conducting.

I've already applied a varistor to protect the SSR (R2) because the motor produces some nasty voltage spikes when it reaches an end position. I also added a snubber circuit (R1 / C1) and tried different values (100/100n, 22/100n, 47/47n) to reduce the dV/dt rise across the SSR (as described here), but so far I haven't been successful.

The motor draws roughly 110W.

Is there an "easy fix" for this circuit or should I replace the SSR with a mechanical relay?

Thanks!


texts: Magnetic float switch + relay setup to control a water pump

texts:
I have a question regarding connecting a Standard magnetic float switch with a relay to control a waterpump.
Relay being used is RM22LG11MR from Schneider with  datasheet here
My setup looks like as shown in figure
  (Brown line is standard 220 V, and blue is the Nuetral)
Under normal conditions, the relay is in Normally Open (12) state. But when the water level in the tank  goes down, the float sensor overrides the relay default setting by bringing it to Normally Closed (14) state, and this should start the pump to fill the tank.
The timing diagram of the relay is also shown below

The relay has two modes, i.e., a fill mode and an empty mode. I am using it in fill mode, so that as long as water tank is not full, the magnetic flow sensor activates the pump.
My question, is that the sensor has only three cables, one is neutral, one is ground, there is only one cable left which i am connecting to "Max" as shown in the figure, i could connect to Min as well. My concern is that in either case on of MAx or Min would be left Open due to the sensor and relay setup i am using, and now i am wondering how to correctly setup this sensor and relay together to make it work for my usecase. Any help will be highly appreciated


texts:
I'm trying to find the Fourier Transform of: $$t^2e^{-2t}u(t)$$
I know that from the FT pairs table, $$ FT(te^{-2t})= \frac{1}{(2+jw)^2}$$
So I assume that we can just use the multiplication property and do $$\frac{1}{2\pi}\left(FT(t)*\frac{1}{(2+jw)^2}\right)$$
However when I try that, I do not get the correct answer, which should be $$\frac{2}{(2+jw)^3}$$
Am I missing some kind of trick I can apply here?


texts:
I'm tasked to reproduce the following signal

using only Op Amps (and resistors).

I'm pretty sure I must add two signals, the square and triangular waveforms, it is just pretty hard to figure out how to twist the signal from -8V to 0V.

I've tried to get the transfer function according to a square waveform signal V2 (-6V min to 0V max, freq=1Hz) and a tringular waveform V1 (0V min, 2V max, freq=1Hz) with this, I get the following output Vo:

Vo = -2V1-2V2-4

Which satisfies the following table EXCEPT AT POINT V1=0,V2=0

    V1  V2   V0
    2   -6   8
    2   -6   4
    2    0  -8
    0    0  -4   <---HERES THE PROBLEM ! (Should be zero)
    0   -6   8

What would I do?

Both the square and the triangular are provided as input signals, the circuit does not generate them just process them to give as a result the signal shown in the figure. It is for a project so it's kind of a homework and I'm working hard on it right now. Both amplitud and time domain are equally important.


texts: How is the heat lost in a peltier distributed?

texts:
I'm looking at peltier elements to heat my project. I seem to find that most are about 5% efficient, but how is the 95% turned into heat distributed?

Does the cold side get 47.5% and the warm side get 52.5% of the energy, or is it more complex depending on the difference between the temperatures? I'm really surprised this hasn't b een asked before.


texts: Calculate a voltage angle offset for a 3-Phase utility meter

texts:
I'm trying to analyze and write a program around some data that I was given. The data is a collection of readings from 3 Phase smart meters of an electrical utility. One value in the data that I can not for the life of me understand is something called a "Voltage Angle Offset" or VAO. Here is what a few records of data look like for each of the phases:

Volts          Amps             Angle       Power Factor    VAO
124,121,220    23.3,45.3,20.4   0,180,270   353,356,270     7,4,90
122,122,213    9.3,8.9,9.1      0,180,270   44,280,15       44,80,15
121,121,210    27,21.9,13.1     0,180,270   18,25,273       18,25,87
122,122,212    7.9,7.7,9.7      0,180,270   52,299,310      52,61,50
124,125,216    13.1,11.6,12.9   0,180,270   303,246,270     57,114,90
123,123,214    9.4,11,13.9      0,180,270   126,34,86       126,34,86
122,122,212    12.7,21.8,24.2   0,180,270   23,298,356      23,62,4
122,121,206    36.8,50.7,38     0,180,270   125,36,46       125,36,46

I can't figure out how one would calculate the VAO given the other bits of information. I'm not an electrical engineer by any meaning of the word (a computer programmer, actually), so perhaps I'm interpreting the data completely wrong.

Any insight?


texts: How is the capacity of link more for single network link

texts:
In networks
capacity_of_link = bandwidth*propagation_delay

My doubt is how can a same wire carry multiple signals? Is is because the wire is very long (still the wire can be either high or low). I can understand if parallel wires are the reason for increase in bandwidth and thus capacity increase.


texts: Why is a system description in control theory important?

texts: If you want to control a system (with a loop controller), why actually do you need to know anything about the system itself (its dynamics or the transfer function or impulse response or whatever)? Isn't it enough to just have a feedback loop that can compensate any disturbance and ensure the target value?


texts:
I need to identify some SMD component.

COMPONENT 1:
Markings are T5 and G7.
Seems package is DFN 6.

COMPONENT 2:
Markings are J90 (underscored)
Package is a 6 pin SOT
This one I suspect is some kind of double transistor

Enclose hand drawing (my camera is busted!)

Thanks for your help


texts: Why measure potential with a three winding transformer?

texts:
I have a single line diagram where it's shown that the voltage is measured with a three-winding transformer on the busbar (22kV), and two-winding transformers on the feeders.

I've seen this on many single line diagrams, but never really thought of it before now.

Why does the voltage transformer on the busbar have three windings? What can be measured with a three-winding transformer that you can't measure with a two-winding transformer?

I don't know anything about the vector group, winding ratios and so on.

The two symbols that are used are:

The diagram shows several current transformers too. It doesn't show which relay functions that will be used (often shown).

I'm not at work, so I can't provide the single line diagrams, unfortunately.


texts:
My question may seem weird, but I am very new in nxp micro-controllers. It seems to me that people use different syntax in C programming. For example, in order to set a pin as an output we have:

LPC_GPIO1->FIODIR |= (1<<29);

while there is another syntax which does the same thing and it looks like this:

FIO1DIR |= (1<<29);

And they both have similar libraries. As I am learning the second type, I wanted to know if there is a reference for this type of coding?


texts: Reversing the direction of rotation of a DC cooling fan

texts:
We usually connect a small DC cooling fan as show in the diagram.

But is there any method to reverse the rotation of this fan in real time, by adding any external circuits?


texts: LiFePO4 Constant Current charging circuit with micro controller

texts:
I made a small off-grid solar station a few years ago, that was relying on lead acid batteries. I am now planning to change it for a 12v 8Ah LiFePO4 battery, because of it's low weight, space needed, and good performance.

I would like to make my own controller to manage the station, including the charging of the battery and the load consumption.

After reading a few batteries datasheets, I know what algorithm I have to write for the charging.

The solar panel gives a max current of 1.12A at Pmax, so just below the recommended 0.2C constant current charge rate (1.6A). However I have some difficulties with the this constant current circuit.

I found some different designs, such as this one which seems the simplest and the same as this one.

I am planning to use an ACS712ELC-05B instead of the Rref resistor.

1) Would that be a good choice ?

Also, I know that I will probably need a Non-inverting Amplifier to convert the 185mV/A output of the ACS712 to an output of about 1V/A, but I'm not sure of which values I should use to calculate the resistor values.

2) What is your advice ?

And my last question is,

3) Will the TL081 op-amp be suitable as the negative feedback op-amp ?


texts: Automotive Pulse Doppler Maximum unambiguous range?

texts:
I am trying to calculate the maximum unambiguous range for FMCW automotive radar.

In automotive, the pulse repetition rate (Tp) is typically 50 - 60ms.  My equation is as follows:

where c is the speed of light.  This becomes

Have I done the above correctly?  7 million metres seems wrong.  Is it different as automotive is using FMCW?

Looking here

  For example, a given radar with a linear frequency shift with a
  duration of 1 ms, can provide a maximum unambiguous range of less than
  150 km theoretically. This value results from the remaining
  necessarily overlap of the transmission signal with the echo signal
  (see Figure 1) to get enough time for measuring a difference
  frequency. Most this range can never be achieved due to low power of
  the transmitter. Thus always remains enough time for a measurement of
  the difference frequency.

This suggests my calculation is correct but for FMCW the chirp duration is used (in the example 1ms), as answered by Neil_UK


texts:
I need to connect a power ground and an analog ground. The power ground is a SMPS output.  The analog side consists of 8 opamps and their resistors and capacitors.
What's the best way to connect these two ground? With some ferrite beads? Resistors? Or directly connect them without any components between them?


texts: Why would electrons cross a cross section when there is no potential difference?

texts:
There is a cross section , it's said that electrons move from left to right and vice versa, and the total sum of the electrons crossing this section from left to right is equal to the ones crossing from right to left.

When we have potential energy (a battery connected to 2 sides of this section) electrons going from left to right are more than the ones going from right to left, and then there will be electrical current.

My question is, why would electrons move when there is no difference of potential?

Edit :
electrons that move are free electrons.


texts: 16 Pin IDC to 40 Pin with different pinouts

texts: I'm trying to connect a 16 pin led panel to a raspberry pi with more permanence than jumper cables.  Is it possible to build a cable with IDC on both sides if the pinouts are different?  Doesn't have to be a flat ribbon cable.


texts: Can I merge two impedance matching circuits?

texts:
I've got an RF transceiver (Nordic's nRF24L01+) which shows a typical circuit to match its antenna output to a single ended 50 ohm impedance.

I've also got a chip antenna which comes with an example circuit to match a 50 ohm line to the antenna feed point.

If I am going to place the transciever and the chip antenna very close, then there is no need for a 50 ohm transmission line right? If so, can I somehow merge those two matching circuits into one and thus reducing component count?


texts:
Possible Duplicate:
  Choosing power supply, how to get the voltage and current ratings?

I'd like to power my new LG M2450D monitor with a basicXL BXL-NBT-U02 universal AC-DC power adapter.
This PSU is rated 90W max and supports 15-24V output voltage.
The original monitor PSU (PA-1650-68) was fixed at 19V and 3.32A.

Now, doing the math:

90W / 19V = 4.74A

Of course this is an ideal value, what is "safety margin" i should assume for the real max amperage?


texts:
This statement was deemed true:
Given any self-complementing decimal code scheme, if we know the codes for the number 283, then we can deduce the codes for 671.

I wanna know why. I took Excess-3 BCD as the self complementing code:

0-0011
1-0100
2-0101
3-0110
4-0111
5-1000
6-1001
7-1010
8-1011
9-1100

So 283 = 0101 1011 0110
   671 = 1001 1010 0011

So why is the statement as it is as 283-ex3 is not a 1s complement of 671-ex3?


texts: What datasheet should I trust for TIP 35 and 36?

texts:
I'm trying to refine a SPICE model for TIP35C and TIP36C and I'm looking for some trustworthy curves to supply points for the model wizard.
I found the models here, but they seem not to be working properly on MultiSIM for some reason and the gain seems kinda larger than what I saw on some datasheets back then.
Then, checking again, I saw the datasheets don't agree with each other.
The datasheets from ON Semiconductors and Motorola both use this same graph for this pair (actually the whole datasheets are exactly identical):

This graph has some issues. The values at the side of the axis are pretty off. Take for instance the Y axis, it has 3 major ticks at 10, 100 and 1000, and the minor ticks between them correspond to 2 to 9 times the value of the last major tick, as it's standard in those base 10 log axis. But the values on the side don't match their respective ticks at all.
Anyway, correcting that, I reverse-engineered the graph to find that the max hFE in both reaches around 300, and the values on that curve don't quite match the values the datasheet itself says it has on some points (it says the typical gain at 15 A is 40 but in this curve it's over 60 for both transistors).
These datasheets also lack a VBExIC curve, which I needed. Then I found two other datasheets, this time from Power Innovations and Savant (which use 2 slightly different but greatly matching graphs) where the hFExIc look like this for both transistors of the pair:

My question is: Which of both is more trustworthy?
I know the second one use a pulse technique, but 300 us looks like a quite long pulse for me. Could all this difference arise from that alone?
And even then, which one should I use in the model wizard?


texts: RC circuit analysis with parallel capacitances (using Thevenin equivalent)

texts:
I am trying to determine the voltage across capacitor C3 (voltmeter VM1) with respect to time. I believe that simplifying the circuit to its Thevenin equivalent is the correct way to proceed but I'm not sure how to.

Specifically, I am unsure how two parallel capacitances can be combined if only one has a resistor connected in series. I know C2 and C3 can be be simplified into a single capacitor with capacitance C2+C3. However, I am unsure how this can then be combined with C1, as resistor R2 is connected in series with C2 and C3 but is parallel to C1.


texts:
DE is a capacitive load.

In a source the waveforms of the buck converter are given as:

On state

Off-state

I am confused about the waveform of \$v_{dS}\$.
On Wikipedia the waveform is shown constant.
How can the voltage change if the rate of current is constant?
Did somebody see this before and has an explanation for me?


texts: Safe to use StepUp-Converter to power LED-Monitor?

texts:
I would like to use the following setup, since I already have the meanwell-powersupply. Can anybody tell me if this should be safe as long as I care for good cooling of the Step-Up-Converter, good and safely soldered connections with quality cables (not just jumper cable)? :

DC230V (Germany) =>
Mean Well Powersupply LPV-100-5, 60 W, 5V, 12A =>
DC/DC-stepup-converter range 4,5-32V convertable to 5-35V with max 4A
current out =>
LED-Monitor, 12V, 3A, 36W

I want to parallely power a raspberry pi and a few 5v powered sensors. The StepUp-Converter shall be heatsinked from 20W output on, to I plan to cool this with active, but slow-running 80mm fan and passive heatsinks.
I am thankful for any hints =) ! Best regards, Oliver


texts: Is this BRAM being fully utilized if I use a different data width?

texts:
Background

I am using a Xilinx FPGA from the Kintek-7 family. The documentation for the memory resources can be found here.

Here are some important excerpts from the document (referencing pages 11 and 12):

  The block RAM in Xilinx® 7 series FPGAs stores up to 36 Kbits of data and can be configured as either two independent 18 Kb RAMs, or one 36 Kb RAM. Each 36 Kb block RAM can be configured as a 64K x 1 (when cascaded with an adjacent 36 Kb block RAM), 32K x 1, 16K x 2, 8K x 4, 4K x 9, 2K x 18, 1K x 36, or 512 x 72 in simple dual-port mode. Each 18 Kb block RAM can be configured as a 16K x 1, 8K x 2, 4K x 4, 2K x 9, 1K x 18 or 512 x 36 in simple dual-port mode.

and

  Each 36Kb block RAM can be set to simple dual-port (SDP) mode, doubling data width of the block RAM to 72 bits. The 18Kb block RAM can also be set to simple dual-port mode, doubling data width to 36 bits. Simple dual-port mode is defined as having one read-only port and one write-only port with independent clocks.

From this, I interpret that the data width of the BRAM is in multiples of 18. So it is 36 with dual port, or it could be 72 if you double that.

Question

In my implementation I only need a data width of 64 bits. What happens to this extra 8 bits? Does it mean that I will not be utilizing the entire BRAM block?

Here is a graphic to help understand the way that I'm thinking:


texts: Why do I need to keep Led drive and photodiode ADC supplies and traces separate in a pulse oximeter design

texts:
I've seen a couple of application notes recommend keeping led drive supply and ADC supplies separate.
To me it seems that since the LED will illuminate the photodiode that ADC is reading anyway, keeping this two close would make sense. Including the reference voltage for current source and the reference voltage for ADC.

I'm referring to this datasheet. Page 78 "11.1 Layout Guidelines"
http://www.ti.com/lit/ds/symlink/afe4400.pdf

  TXP, TXN are fast-switching lines and should be routed away from sensitive reference lines as well as from
  the INP, INN inputs.

Is is possible that this are just general recommendations and the author did not consider this special case where LED illuminates the photodiode from the same circuit? Or is this to prevent oscillations.


texts: Why is current different in 2 identical parallel branches of my circuit?

texts:
I'm trying to build the classic thermoregulated fans for an IT cabinet, and I'm struggling with some weird phenomenon. Here is my circuit:

simulate this circuit – Schematic created using CircuitLab

+5V is provided by an arduino Uno, itself powered by a 12V supply. The 3rd pin of each sensor goes to the analog input of the arduino. There are 2 sensors because the cabinet will have multiples floors and I want to control the fans independantly of each other.

It works, but datasheet for LM335AZ (thermal sensor) says that for maximum accuracy, current through the component should be around 1mA. Its voltage drop is 3V, so that's 2V in R1, with the 1kΩ resistor there should be 2mA, split in 2 that's 1mA for each branch.

However what I'm seeing is one branch takes 1.7mA and the other 0.3mA. As they are strictly identical I really don't understand why. My electrical basics are quite far, so what am I missing?


texts: Creepage and clearance when using relays

texts:
I'm looking at this 10A, 277VAC relay and wondering if there is sufficient spacing between the low voltage (3.5V, 100mA) and the high voltage(277VAC, 10A).  The foot print looks like this:

Are the 5V leads too close to the high voltage leads?  Why aren't the high voltage leads on one side and the low voltage leads on the other side?  Also, the use case is to be mounted on FR-4 and there will be a fuse before the high voltage goes to the relay.


texts: Are flash memory and ROM also considered integrated circuits? And so, is it possible to embed a flash memory or a ROM into an ASIC?


texts: Losing sensitive data when trying to send them via GSM

texts:
I am working on a system which collects data from a set of ultrasonic sensors. Those sensors work at 40Hz frequency, and each data they send are valuable to me. I need to send those data to a mqtt broker using mqtt protocol. I use TCP/UDP connection of SIM900 in order to send data. There are two scenarios to make my system work:

1- I send the data as soon as I read it from sensors. It means I should connect to a server, send data and disconnect it in less than 1/40 seconds. I dont know, but using AT commands with SIM900; it seems pretty impossible to me.

2- I collect the data for a while, (lets say for a minute) then I send the data to server as a bulk. But there another problem arises: I am facing losing sensitive data I collect from sensor while I am making TCP/UDP connection.

My hardware consists of SIM900, an arduino and bunch of ultrasonic sensors work at 40Hz (HR-SC04)

Is there a way to save every bit of data I read from sensors and send them to Mqtt server, losslessly?


texts: Switching a PAM8610 sound amplifier board with a Raspberry Pi or Wemos Di mini GPIO

texts:
I'm a complete novice.
I want to be able to switch a PAM8610 sound amplifier board, which runs on 12VDC, with a GPIO that outputs 3.3VDC.  I know I need some sort of relay. The board draws around 2A and googling I found the LM338T.  Can I use a transistor?  Is this the right one? Do I need any other components to make it safe?
My plan would be to remove the jumper from the switch pins next to the pentitometer and run those pins through the transistors input and output.
Edit to add:  It occured to me after I posted that there might be less than 12v across those pins so I checked and in fact it seems like there is 7.25V across them.  Still to much to run through the Pi.
This is the datasheet for the underlying module:
https://www.diodes.com/assets/Datasheets/products_inactive_data/PAM8610.pdf


texts: What is the main difference between the GTO and BJT in terms of advantages/disadvantages from a power electronics point of view ?


texts: Thoughts on Kickstarter project, USB Based Variable Power Supply For Small Projects

texts:
I am new to electronics and am still just learning.  I saw this project on Kickstarter for a small USB based DC power supply and was wondering what some of the more experienced people thought of it.

I am considering buying two for experimentation/hacking at home. Is this a good idea or should I be considering an alternative product?

Link to the Kickstarter project: http://www.kickstarter.com/projects/210251816/usb-based-variable-power-supply-for-small-projects-0. UPDATE: It is closed and didn't meet funding but was relaunced here http://www.kickstarter.com/projects/210251816/usb-variable-power-supply-for-small-projects-relau.


texts: Maximum surge current through short run of 24 gauge wire

texts:
I'm making a sequenced rocket launcher.  I want to apply 5 amps for 3 seconds through a 12 inch run of 24 gauge wire.

Since the launcher has four slots, I figured I could use cat5 ethernet cable.  This bundles the necessary 4 pairs of wires nicely and is color-coded and conveniently available.  Since each ignition will have its own circuit, each 24 gauge pair will only see the surge once.

Is the 5 amp surge going to be too much for the 24 gauge wire in the cat5 cable?  From examining tables like these (http://www.powerstream.com/Wire_Size.htm) I know that my current requirement is about 10 times the limit for 24 gauge wire.  Max current is further degraded by the wires being bundled.  However, I can't find good data on acceptable surge limits.


texts: MOSFET Bi-directional current channel selection

texts:
With the circuit below:

Q2 and Q4 burn down when 15A is injected into the circuit. Q4 burns even if it were never activated.

The gate voltage control is 0 or 12V to activate a particular channel.

I've tried to add protection components (zener / res on the gate), but it still burns down.

I don't really get why. The circuit is referenced to the ground with Q3 and Q6 forward diod make sure the voltage drop is reasonable, which would create a dV of 1-2V. The shunt itself would make a dV of less than 0.1V which would give a Vgs of ~10V in the worst case which is plenty enough to drive the mos:

Is there something I am missing on this circuit?


texts: Which footprint to use for LM324 SO-14 in KiCad?

texts:
I want to use the LM324 quad-amp in my PCB design. KiCad already provides the symbol in the Amplifier_Operational package. However I don't know which footprint to assign.

I tried assigning the generic Package_SO:SOIC-14_3.9x8.7mm_P1.27mm footprint which has the correct mechanical dimensions. However, there does not seem to be a connection between the pads in the footprint and the symbol.

Therefore I have the following questions:

Does KiCad already provide a footprint for LM324?
If KiCad does not already provide a footprint, how to connect the generic footprint's pads to the correct nets?


texts: Rectify AC and keep the voltage below V_max for DC step down converter

texts:
I bought a DC-DC step down converter (MP1584EN), but I found out my input was actually AC (24 V). I plan to use a bridge rectifier with a smoothing capacitor

The problem is that the converter is recommended for 28 V. AC V_max is around 35 V.

How do I keep its input voltage within the limit?

Output should be 3.5 V, max 500 mA. Converter's efficiency around 28 V is above 75 %.

I don't have many parts. Large transistors (irf520), diodes, caps (\$100\ \mu \text{F}\$), tiny resistors.

What about installing a transistor operated by a voltage divider: voltage gets above 28 V -- disconnect the converter. If there is a leak through transistor's drain-source I could ground it through a high R resistor.

I need to make sure that the transistor is operating fast enough to disconnect it before the voltage builds up.

That wouldn’t probably deliver enough power and I would need large capacitors I don’t have.

Edit:

The diodes are 1N4007, the resistors (axial) I believe 1/4 W (around 6 mm length, 2 mm diameter).


texts:
I want to make a counter that can count the time between pulses in nanoseconds. The counter starts to count when a pulse enters a pin (at the start of the pulse) then stops when a second pulse comes. Then the timer sends a signal to either a display or LED and starts the counting again.

The time between each pulse is anything from 100 ns to 1 s and the pulse width is 100 ns to 1 µs. The counter needs to be as cheap as possible and does not need to give me a 100 % accurate time. For example, if the time is 100 ns and the counter says its 200 ns it is acceptable (basically ±100 ns).

Resolution: There is no need for it to read in 0.1 ns but rather 10 ns steps.
Display: Either a simple LCD, CRT or anything really.
Noise: The pulse will be from 0.5 V to something higher.


texts: Trace Length Tolerance Calculation - High Speed PCB Design

texts:
I have to interface a video format converter with a ADC IC, which converters RGB analog data to digital. The connection between this ADC and Converter is a 20 bit data bus which clocks at about 170MHz. Since I have the PCB area constraints I cannot perfectly match the trace length of this data bus. I heard that there are matched trace length tolerances depending on frequency so that it will not damage the signal acquisition by the destination.

My question is how to calculate trace length tolerances in a High Speed PCB design? (in differential pair routing and high speed data bus routing)


texts: Beginner - unable to use AND gate with buzzer and flashing light circuit

texts:
I have a circuit which needs to turn on the buzzer and flashing lights when both my switches (switch 1 and 2 left side of the circuit) are on. I was trying to do this with a AND gate but couldn't get it to work (needs to output 9 volts). Does anyone have any suggestions?

Help would be much appreciated as this circuit goes towards my test grade and I'm currently stressing out about it.


texts: Calculating capacitance and resistance for transformerless power supply

texts:
Here is the circuit:

Zener diode is 6.2v, 1watt and R4 is the load so that
$$250\le R_4\le500$$
If ripple voltage of C2 is 2V, determine values of R3 and C2 such that a constant 6.2 voltage appears across R4.

Note: Values of other elements are fixed.

Using reactance of the C1, we find that current through the source is approximately 45.9mA. Also we have
$$2mA \le I_z \le 161mA$$
$$12.4mA \le I_L \le 24.8mA$$

I don't know how to calculate R3 and peak voltage across C2 with that information. If we find them, then determining C2 is straightforward using ripple formula :

$$V_r = \frac{V_p}{2fRC}$$

With the help of simulation, I tested several values and R3=100Ohm, C2=1mF worked very well but don't know how to actually calculate them by hand.


texts: Is there a way to trade off amperage for voltage?

texts: I was planning on buying a motorcycle battery or some other large battery to charge my laptop, but most of the batteries I found are 12v or lower, and I need around 20v to charge my laptop. Is there a way to trade off amperage to get more voltage? I would rather do that if I can instead of buying 2 batteries and getting a resistor to get the right voltage.


texts: I have a GPS chipset. I need to attach an intenna which has 50 ohm impedance. When i read the data sheet of the antenna it mentioned that the feed line to the antenna should have 50ohm impedance matching characteristics. So what kind of wire I should use to connect the chip scale GPS antenna to the pin on the GPS chipset which says GPS RF. Should I measure a wire of 50 ohm resisitance and connect it between the chip scale antenna and the pin on the GPS chipset or is it something else? Should I use any special coax cable which has 50 ohm impedance? What did it mean when it was written in the data sheet that the feed line should have a matching impedance of 50 ohm. Please let me know.


texts:
I would like to generate a 30 kHz & 60 kHz sawtooth waveform using an LM358P operational amplifier per the following schematic.
Theoretically, and in the simulation, the circuit should work perfectly, generating a ~30 kHz or ~60 kHz signal depending on the switch position. In reality, the signal is distorted and varies between 6 & 8 kHz respectively.
Resistors/capacitor values were calculated based on the equations from the LM741 lab exercise which I am linking below.
What can be causing the issue?

Falstad Simulation: Link
LM358P Datasheet: Link
Lab Details: Link

Calculations
I haven't taken the slew rate of a device into the account initially, but here are my calculations for the 30 & 60 kHZ sawtooth generator.
1. Biasing
Generator is driven from a single 24V power supply, virtual ground is derived from the voltage divider - two 1k resistors in parallel with 220nF capacitors, and saturation voltage is chosen to be 1V & 23V respectively.
Note: Saturation voltage was chosen without consulting the datasheet, so that was the first mistake.

2. Amplitude
Chosen amplitude of a signal was 22V, so the following resistors were chosen.

3. Duty Cycle
As I wanted to generate a sawtooth wave, chosen duty cycle was 10%.

4. Frequency
To keep resistor values small, 10nF capacitor was chosen for the integrator, and for the 30kHz frequency resistor was calculated with the equation from the attached lab.

Note: The frequency had to be appropriately increased to take into the account selected duty cycle.
4. Slew Rate
The slew rate of the LM358 is only 0.3 V/μ - which I didn't take into the account. For the 30 kHZ triangle wave generator minimum required slew rate is 4.14 V/μ, and for the 30kHZ sawtooth wave generator 6.9 V/μ.


texts:
I have two different transformers. The output of the first one is 15 volts and 1500 mA. The output of the second one is 5 volts and 500 mA.

If I connected them in series (to get 20 volts) what will happen to the current?

If I connected them in parallel (to get 2000 mA) What will happen to the voltage?

Is there any danger in the previous connections?


texts:
I'm trying to design a constant current solenoid driver using UC3843 PWM IC.
The datasheet is available at https://www.ti.com/product/UC3843
Since I'm only utilizing constant current function using current sensing, I don't
need voltage feedback compensation using error amplifier. Hence I'm simply clamping
COMP pin to required voltage using external voltage divider (max voltage = 5V).
The VFB pin is simply grounded using a 1K resistor. The circuit works and operates as a constant
current driver very well, but I'm not sure if this is the correct way of doing things.
Should I just clamp COMP voltage or should I configure error amplifier as an unity gain amplifier and
provide target voltage to the input pin?
Here is the block diagram of UC3843

This is my configuration for VFB and COMP


texts: Problems with deriving output resistance without using a model

texts:
I was reading different texts about input and output resistance of the above circuit and trying to understand the Rin and Rout without using any transistor models such as pi-model or T-model. I think I understand how can we comprehend what input resistance is. Here is the summary from what I understand for Rin without using any model:

Lets assume the voltage at the point Vb is increased by ΔV.

This means the voltage at the point Ve also will increase by ΔV.

If we want to write an equation for the input resistance Rin(the resistance seen from the point Vb); we can use the β relation between the base current Ib and the emitter current and the fact that the same ΔV will appear both at Vb and Ve.
So Rin can be derived by using the following steps:

ΔIb = ΔV / Rin

ΔIe = ΔV / (Re//Rload)

since Ie = (1+β)*Ib

Rin = (1+β)*(Re//Rload)

So Rin input resistance can be written in terms of Re, Rload and β.

Question:

I cannot find a similar step by step comprehension derivation of the Rout without using a model. I mean I would like to clearly write down how Rout is obtained as I have written for Rin above.

The texts say that the Rout(looking back at the emitter) is:

Re // (Rsource/β)

But I'm very confused at this point how this is derived
How they obtain Rsource/β conceptually.

How can we step by step explain Rout here as in Rin case?


texts: Need Help... So Confused with this QFP32 SA663 Socket

texts:
I purchased an SA663 clone QFP32 Socket online, but to my extreme dismay, it doesn't work, or at least I haven't been able to get it to. Basically the original SA663 is a 1:1 pinout. But after trying at least a million pinout combos, I can't seem to get this thing to work. From what I can tell it is NOT a 1:1 pinout.

Here is the email I received from the original makers of the SA663. He says they're a 1:1 pinout, but the one I have isn't, and upon inspection of the board, the traces aren't going to the same number pins. It almost looks like DIP1 is going to QFP26+ (I can't tell without separating the two boards, and I don't think I can)

I'm sure one of you mega-geniuses out there has one of these and knows the pinout. I'm about ready to trash this thing. Can't even get the pinout from who I bought it from or anyone who sells them. Major waste.

And in my defense, I had no idea this was a clone. I just thought these were THE programming sockets, not that there was a company being ripped off for designs and such. I feel dumb, but I'm still making some rookie mistakes.

Thanks in advance, friends!


texts: Gate Capacitance and Miller Capacitance on the MOSFET

texts: How is the Gate capacitance and the Miller capacitance modeled for a MOSFET. What is the behavior for both when a Gate Voltage is applied?


texts: Does peak shaving reduce the stress on power lines

texts:
I am not an eletrical engineer and have a question about demand side management in smart grids. One application is peak shaving, which means that the maxium power is reduced. Does this decrease the stress on the power lines?

Basically I would like to write the following sentence in a scientific article:
"Another application for flexible electrical loads is to reduce the peak load in a local grid in order to decrease the stress on the transformers and power lines"

Is that true or would you advice me not to state something like this


texts:
I'm having issues controlling a single relay module with an arduino. It works fine when its up and running but the relay initially starts triggered until the arduino can send a "high" signal to turn it off again. I should have used a high trigger relay instead of a low trigger one.

My question is whether I can use a pull-up resistor on the input of the relay (being the output pin of the arduino)

both the arduino and relay are powered by a common 5v supply.


texts:
I'm reading Analysis and Design of Analog Integrated Circuits by Gray & Meyer. In the differential pairs' chapter, there is this circuit

and it says:

  Assume the collector resistors are small enough that the transistors do not operate in saturation if \$V_{i1} \leq V_{CC}\$ and \$V_{i2} \leq V_{CC}\$.

I don't understand why large values of \$R_C\$ would lead to saturation for input voltages that are less than \$V_{CC}\$. Any ideas?


texts:
I know there are lots of questions and instructions on how to use a netduino (a variation of the arduino) as a dimmer.
But all I would like to do is read the output of a light dimmer with my netduino.

Big Picture Idea:

I have my netduino configured with some RGBW strip lights and it works great, but I would like to be able to dim them from a standard wall light dimmer like this:

http://www.amazon.com/Lutron-S-600P-WH-600-Watt-Skylark-Single-Pole/dp/B000MAVU2A/ref=sr_1_19?s=hi&ie=UTF8&qid=1456953055&sr=1-19&keywords=light+dimmer

The thing is, I have no idea how a dimmer works.  Is it a potentiometer?  Something else?  Is there a particular one I should buy that would easily work?

I would like it to be thin, because I would like it to stay on the wall with adhesives, as I live in an apartment so I can't go knocking holes in the wall to add another light switch.


texts: In complex power and power factor analysis, how do I get the Thevenin impedance if there is a dependent source?

texts:
I'm preparing for my exam tomorrow, and I've found something ambiguous. How do I get the Thevenin impedance for this circuit?

Is it possible for me to get the impedance of the dependent source and then get the equivalent Thevenin impedance of the whole circuit? I have to find the equivalent resistance of the circuit because I need to add a power factor correcting reactance as seen from the terminals of the independent source.

Ia is already in RMS by the way since the given source is an RMS voltage.

simulate this circuit – Schematic created using CircuitLab


texts: FPGA design rules - Using a Module Output Register Value Internaly

texts:
I'm trying to optimize a verilog code and I found something that I don't feel it's correct. I found a module that has an output and it's using that output value as a condition in a case statement. There is an example:

module TT
(
    output  reg                             Busy        =   1'b0
,   output  reg                             Finished    =   1'b0

,   input   wire                            clk
,   input   wire                            rst
,   input   wire                            start
,   input   wire    [   5 - 1   :   0   ]   freq
);

always @ (posedge clk)
begin
    if(!rst)
    begin
        case(Busy)
            1'b0:
            begin
                //do some logic...
                if(something)
                    Busy = 1'b1;
            end

            1'b1:
            begin
                //do some logic...
                if(something_else)
                    Busy = 1'b0;
            end
        endcase
    end
end
endmodule

Is it good practice to do this? If not, why?
Thanks a lot.


texts:
I'm getting a streetlight, most likely with a HPS bulb (high-pressure sodium).
I'll probably hook up some sort of sensor to turn it on only when someone is actually parking lot.

Why do some streetlights seem to take a long time to turn on?
Is there anything that can be done to get parking lot lights to turn on quicker?

Why do some companies say you must let the bulb cool down for a minute or so after you turn it off, before you can turn it back on?
Is that a limitation of the bulb itself, or the control ballast, or what?

Can "dimmable HPS" systems reach full brightness from a nearly-off dim state quicker than traditional on/off HPS systems?

The only dimmable HPS systems I've seen so far can dim down to a minimum of 1/2, which visually seems only slightly less bright than full on.
Is there some reason HPS can't dim down to 1/10 or 1/100 like other lighting technologies? (Am I just not looking in the right place for dimmable HPS systems?)

How do you dim a streetlight bulb -- how is the voltage/waveform applied to the bulb different at dim than at full power?

Are there any reasonable alternatives to HPS bulbs?
If Haitz's law continues, then someday LEDs will cost less -- but the current
LED lamps that last 10 times as long, but cost 100 times as much to get the same brightness, don't seem reasonable in 2011.

(Edit: dropped protocol question as suggested by Jay Kominek - it's at motion detected protocol )


texts: Does PCIe hotplug actually work in practice?

texts:
I've got into a discussion in the comments of https://security.stackexchange.com/questions/109199/is-physical-security-less-important-now-for-securing-a-server?noredirect=1#comment194327_109199

The question is simple. Has anyone experience of successfully hotplugging a PCIe card? Does it require special motherboards and cards, or is it supposed to work on all consumer hardware?


texts: Send data over server from microcontroller

texts:
How large chunk data of data is send over internet using GSM module or ESP from some kind of microcontroller.
As they both have a limit of data sent by TCP so how is it done and what is used to achieve the same?
Continous multiple requests will be time taking isn't it?


texts: Avoiding noise coupling by power switching to ground plane in multilayer PCB

texts:
I've a 4 layer PCB in which I've to layout a power switching supply mixed with digital signal circuit.

My stack up is:

Top Layer: component and routing (power net and signals)
Internal plane 1: GND
Internal plane 2: +3V3
Bottom Layer: routing (power net and signals)

Now the question is: what's the better way to layout the GND internal plane?

I've thought of three possibilities:

use all the PCB area with GND plane
clear out both planes on the PCB area in which is present the power switching circuit and use the only what remains with GND
split GND planes and make a dedicated analog GND internal plane only for power switching circuit

I was thinking to proceed with solution 1), but I'm wondering if the power switching circuit may inject noise to the GND plane by coupling.

Is solution 1 OK? How should I modify it?


texts:
I have been considering using Nitinol wire for some experimentation as a component in an autonomous system.  My understanding is that it will return to its original, contracted state when it reaches ~70°C, which seems to be capable of some pretty neat applications by passing current across it.  I assume that if I were to buy some, I should purchase the stuff with the thinnest diameter for maximum resistance in relatively short (<20cm) lengths.

So, for those of you who have been able to play with the stuff, is Nitinol the nerdy engineer-candy it appears to be?


texts: UART: Only receiving mess on RasberryPi when connected to a PIC18

texts:
I have a PIC18LF27J53 running properly and I'm able to make an LED blink. FOSC is at 8MHz (which is confirmed through the LED).

Now, I want to make the PIC send some bytes to the RaspberryPi via UART (I'm using minicom to inspect /dev/ttyAMA0 and have disabled both bluetooth and the serial console). I tried with both TX1 and remapped TX2 but I'm only receiving the same mess (fààþæ). I tried to invert the logic, but that didn't help and I'm receiving ~øxøxxøxþ instead.

This is my code to setup the UART interface (with BRGH, 8-bit BRG @ 9600):

TXSTA2   = 0b10100110;
RCSTA2   = 0b00010000;
BAUDCON2 = 0b01000010;
// BR=FOSC/(16(n+1)) <=> n=FOSC/BR/16-1
n = (uint8_t)round(1.0 * CLOCKSPEED / BAUDRATE / 16.0) - 1;
SPBRG2 = n;
RCSTA2bits.SPEN = 1;

The formula outputs 51 for CLOCKSPEED = 8MHz and BAUDRATE = 9600 which is the same as written in the datasheet (page 343).

This is the code I use to send a string:

void putc(char c)
{
    while(TXSTA2bits.TRMT == 0);
    TXREG2 = c;
}
void puts(const char *str)
{
    const char *p;
    for (p = str; *p; p++)
        putc(*p);
}

Finally, I call it like this:

const char *str = "HELLO\r\n";
puts(str);

What can I do to make the RaspberryPi receive the correct characters?

EDIT: I just tried to print the character U (01010101) continously via UART. Minicom receives continously alternating the chars f (01100110) and æ (11100110). So I'd guess that there is an issue with the baud rate. How can I check this and find the error?


texts: Correct way to show 2 different power supplies on a schematic

texts:
I am creating a schematic which is spanning multiple pages, and for clarity, the various ICs/components are being drawn with "+5v" & "Gnd" symbols.

However, due to current limit constraints I'm having to provide two separate 5v supplies.

What is the correct way to show this on a schematic though?

Should I just be adding extra labels to my +5v symbols to identify the source?
Should I actually add in the two different power supplies and then use net names instead of the +5v symbols?
Or is there another way?


texts: 5k Ntc thermistor series resistance calculation

texts:
I have a NTC thermistor It has zero-power resistance of 5kΩ at 25°C. I will use general  voltage dividing and reading but I have 2 questions.

How to calculate     the series resistance    needed  when         using 10V supply ?
What changes whether the series       resistance is at  the upper leg or the lower leg?


texts:
What's the cheapest way to detect vibration with Arduino?

What's the vibration sensor that I need?

I want to detect PING PONG NET vibration and light on led if touched.


texts: What is amount of current required for p-mosfet when load is not applied?

texts:
I am using p-channel MOSFET(NTR4502PT1G) in my application in the configuration shown in the image. If 9 V input is absent, p-channel MOSFET (NTR4502PT1G) turns on, and battery power is supplied to entire system if on/off button is switched on.

I would like to know the amount of current drawn from the battery when on/off button is turned off, the 9V input is not connected to gate terminal of MOSFET and battery is connected to the source terminal.

Please help me in this regard.


texts: How important is it to seal/coat a PCB project for *normal* conditions?

texts:
Reading through What's the best way to protect a board from corrosion in a hot/moist environment? it has specific advice for a board/project that will be used in a harsh environment.

How important is sealing a board for use in a normal or even a kind environment?

Do people assembling DYI kits generally worry about it?


texts: Current sink for microcontroller port not constant

texts:
I have designed a two-transistor current sink for my application. I need it to keep the current constant which flows through an IR-LED:

simulate this circuit – Schematic created using CircuitLab

The current should be constant at:

I = UBE1 / R1 = ~0.7 V / 120 Ohm = ~5.8 mA

Now the problem is that the current will not stay constant as desired when varying the voltage between 2.6 V and 3.3 V. It varies between 1.6 mA and 4 mA. What do I miss here?


texts: How is data transmitted along with an FM broadcast signal?

texts:
When listening to FM radio on mobile using 3.5 jack headphone , sometimes the name of current show or other "xyz" information are displayed, how is that possible?

How do analog signals contain that information and how does a mobile phone identify such data from all mixed signals and show that differently?


texts:
Hello friends of stackexchange,

I want to make a magnetic brake based on a universal motor from a Candy wash machine TYPE 20584.528. I suppose that the best way is to use the motor as a DC generator using the field winding as a permanent magnet and extract the current from the rotor winding, the issue that I have is that I havent found any datasheet from de motor for kwowing the maximun voltage I can use in the winding so not destroy the isolation. Also I want to calculate the disipation power for calculating the resistance that I need as a load for closing the rotor circuit and act as a brake.

The field windings are connected in the way that there is three cables and the resistance is gray-brown 2 Ohm, gray-black 1.3 Ohm and black-brown 1.3 Ohm I suposse that is because is a two speed motor, but seems to be conected in triangle way.

too I want to know if it possible to use a counter current for incresasing the resistance and how to do it, having always in mind that heat can destroy the windings.

The purpose of all this mess is to implement a bike roller with magnetic brake  that could be great for these quarantine days.

So thanks in advance and be free to give any advice suggestion.


texts:
I have a twisted pair input to the IN+ and IN- pins of the MAX9278 deserializers.
The Parallel data output of the deserializer consists of 4 LVDS data channels and 1 LVDS Clock channel to a 3.1" TFT whose Pixel Clock is calculated to be as 27MHz.
So, I guess the twisted pair inputs IN+ and IN- would also be 27MHz. Am I correct is assuming so?
In that case, what impedance should be maintained between the IN+ and IN- twisted pair input signals to the deserializer? Should I maintain the 100ohms impedance just like if it was a coax input or what should I do?


texts: IEEE test system accuracy and transmission line connections

texts:
In practice, do transmission lines ever directly connect two electrical generators to each other? Or is it more common for two generators to be connected indirectly through a substation? In the IEEE test systems, this seems rare, so I was wondering if the test systems are accurate.

Along these lines, are there any "standard" references which describe the IEEE systems and their limitations?


texts: can moulding RTV silicone be used as a solder resist? note that this silicone is made for casting low melt alloys/metals.


texts: 4-bit memory serial to parallel memory register circuit question

texts:
I am  building a 4-bit serial to parallel memory register and I feel like so far I have gotten things right, but I'm unsure of where to connect the CLR connections.

Could someone have a look at my diagram just to check?

Just as a heads up I know that it can be made with D flip-flops, but the logic gate board that I'll be using only contains J-K flip-flops, so I had to convert them.

Does anyone know a program that has a virtual Logic Gate Board or anything which is better than Logisim?


texts: How to measure amperate going through a 220V cable?

texts:
Meta objective: I want to pull up a TV with a winch, when the TV is turned off. I can already move up and down the TV invoked by my controller (Arduino Nano). The physical push-sensor stops the winch automatically. Good so far.

Objective of this questions: I don't want the guest to push an extra button to make the TV go up or down. There is an indicator when the TV is used and that is the Watts that are going through the 220/230V cable to the TV. If amperage is high, I instruct the winch to let the TV down (viewing position). If it is low, I pull the TV up.

See the sketch for a general idea.

Now, I'm not an electronics engineer. My question is:
1) How can I measure the high amperage (or watt) of the 220/230V cable and give that value to my 5V-controller (Arduino Nano). With my little experience I cannot think of an electrical component that could do that. However, there certainly must be a way to detect the big difference between 300 mili watts and 75 Watts. Nice if someone could point to a real component so that I could read up on that component.

2) Can one achive my meta objective without a controller? (This is nice to know. I'm totally happy if questions 1 is answered thoroughly.)


texts: Parsing Raw ADC Data into Voltage Levels

texts:
I'm collecting single-tone test data on the ADC12J4000EVM using the TSW14J56EVM and the High Speed Data Converter (HSDC) Pro software and ADC12J4000EVM GUI. I am trying to capture raw time domain data to a binary or csv file format so I can post-process the data in MATLAB.

Following the HSDC User's Guide, in the HSDC GUI I save data using File-->Save Raw ADC Codes as Binary File. I also explore the option of saving the data as Signed 32-bit ints using File-->Save I32 Codes as CSV file. I'm having trouble figuring out the correct way to parse the data, which is apparently stored as ADC Codes rather than voltage levels. I've seen a few similar posts on the TI forums, but I would like an explicit explanation on how to parse the data, and if MATLAB code could be provided, it would be much appreciated.

Here's my MATLAB code thus far, assuming the binary data is stored as 32-bit integers, non-2's complement. N is the number of bits, Vfs is the typical input full-scale peak-to-peak voltage from the Analog Input Characteristics section of the ADC12J4000 online datasheet.

function Data = ReadTiAdcData(filename)
fid = fopen(filename,'r');
Data = fread(fid,'int32');
fclose(fid);
N = 12;
Vfs = 0.75;
Data = Vfs*Data/(2^N-1);

ReadTiAdcData calls a Spectrum_Analyzer.m function which I provide with time-domain voltage data, and the sampling rate of the ADC. It generates a FFT spectrum, SNR, SFDR, and ENOB from this information.

Now, there is nothing wrong with the Spectrum Analyzer function. I have used it before many times on raw ADC data I took from another ADC (the Analog AD9625) with the same number of samples (65536). Other people have also used it with no problems. So the problem is not with the code, it's with the data I'm getting.

If I use this code on the binary data and take an FFT of the data using a MATLAB Spectrum Analyzer function, the spectrum looks nothing like what's recorded in the HSDC GUI. It's not just a scaling issue (fundamental shows up in the wrong location, there's very high spurs, etc.).

If I instead read in the CSV data directly, the spectrum looks similar to what is displayed in the HSDC GUI. There is a fundamental at the right frequency. The noise floor is about the same shape and dB down. However, the SNR, ENOB, and SFDR calculations are wrong by a significant margin.

It boils down to this:

What is the difference between how HSDC formats the CSV file and binary file?
What is the correct way to parse raw ADC data that is stored in a binary file or csv file into time-domain voltage data?


texts: HIFI amplifier: diagnosing power amplifier stage

texts:
I have a Sony HCD-MD373 HIFI which experiences odd issues:

there is no sound on attached HIFI speakers
there is sound on headphones plugged into the headphone jack
there is sound on headphones attached to the HIFI speaker connections

Signal path [click to zoom] (see top right hand corner):

The above descibed phenomena lets me conclude:

the speaker output relay is working correctly
mute control is working correctly

To me this leaves the following options:

amplifier is defective
overload detection is defective
"DBFB DET" is defective (I believe that is some kind of bass feedback loop)

Amplifier board circuit [click to zoom]:

The amplifier fuses in the above board are ok.

Questions:

Can anybody take an educated guess what the issue is likely to be?
Any hints on how to proceed diagnosing this with only a multimeter?
Can the Sanyo STK4132MK2 power amplifier IC be defective given that it is still able to drive headphones?
Can the power supply to the power amplifier IC be defective given that the amplifier still drives headphones?


texts:
My project aims to measure the current of a photovoltaic module after applying a certain voltage across it.

That means applying a voltage from 0V to 38 V with 0.1V step and measure the corresponding logarithmic currents (which vary from almost 1mA to 8A) then draw the Current-Voltage curve after sending the measured data to the computer.

I have developed an initial system using an Arduino Uno R3 ..... I measured the big voltage across the module using a voltage divider (0V to 40V down to 0V to 5V) and the current was measured by current sensor ACS712. However the current measurements were so bad since it is logarithmic and in the mA range.

My supervisor has suggested that I can't measure such low current and high ones in the same time, and that I have to divide it to 3 ranges. After reading and searching online, I decided to have 3 ranges:

4mA to 20 mA using RCV420 (Precision 4mA to 20mA CURRENT LOOP RECEIVER)
20mA to 200mA using INA118 instrumentation amplifier with \$0.1\Omega\$ shunt resistance, but I am not sure about the gain and other components that should be implemented in the overall circuit.
200mA to 10A using the current sensor ACS712

Am doing the right thing?


texts: Suppose I have several hundred pieces of the same module to test and flash, and the connectors themselves have wire holes in them like below. What's a good way to make the connection without soldering?


texts: Is it safe to leave a SLA battery connected to 12v all the time for "trickle charging"?

texts:
I am considering building a 12v DC UPS for network equipment, and found this other question which contains a description of how one might build such a device. It suggests:

  A Buck DC/DC converter handling charging, but a simple LM317 could also be used, especially if the battery is stored at a fixed temperature, (look up "SLA charger lm317).

The suggestion that a buck converter alone could be used for this purpose makes it sound like the battery would always be connected to the power source.

Will this damage the battery or create a safety hazard?
How would you determine the output voltage to set on the buck converter?


texts: Spectre - measuring subcircuit current with wild cards

texts:
Presently I am measuring sub circuit current as under:

.probe isub(segio.Vdd)

Its working well but i have to write separately for all subcircuit.

Is there any option to use wild card or give depth in spectre as under:

.probe isub(segio. *.Vdd) depth=10


texts:
Does anyone have a schematic for the usb005 Infineon dongle?
We need to program exactly Infineon IC's, and I would like to understand is there any special features, or we could use any similar dongle or MCU.


texts: What is the use of BOOST converter in this circuit?

texts:
Here is a circuit in which a supercapacitor is in parallel with the battery to manage the high pulse current requirement without stressing the battery. What is the use of boost converters here?

One more doubt-->

Are these boost converters are required if i am using 3.6v battery and I only need a 3.4v-3.6v Vout? I am using 5.5V, 4.7F cap.


texts:
I'm looking for a way to track people in rooms.

iBeacon track Smartphones. But it requires people to have a smartphone.

I'm looking for a reverse beacon ? People wear iBeacon and trigger a kind of BLE "light smartphone"

(There is RFID answer put "it's complicated" and imply antena, etc ... )

Any Ideas ?


texts: Circuit breaker selection that can be tripped with a microcontroller

texts: I am designing a system that will simulate an upstream fault with a micro-controller action. the micro-controller will send a signal to a circuit breaker to simulate a line to ground fault(just like the test button on several circuit breakers). What kind of circuit breaker can i select that can be electronically actuated by a micro-controllers digital i/o pins. Or what technique can i use to simulate this fault.


texts: How to reduce code size in flash of atmega8?

texts:
I write code for Atmega8 in Atmel studio and the size of code is overflow the flash size of microcontroller. Could anyone help on How to Optimize code for Size? or have experience in reduce code size in flash?
Thanks a lot.


texts: Trouble using a generic 4-20mA to 0-5V board to connect transmitter to Arduino

texts:
I'm doing a big project, where I will connect a lot of sensors to my Arduino Mega 2560. Eagerly, I bought boards of this type, but I can't get them to give me any voltage output! I've connected them with +24V, and my 2 wire 4-20mA sensor, a pressure transmitter, to the other end.
There's no documentation to be found about the board, despite it looking like a popular product.

I have Vout measured with a voltmeter, it says 0.13. It's no different than the other cards, where there is no sensor attached at all.
I was expecting there to be +24 between I+ and I-, but there is nothing. It's 100ohm resistance between them internally in the card.
I have 16 of them, and they all behave the same, so there must be somehing I'm not doing right Could it be that they are made for 3-wire sensors? How can I wire it differently in order to make it work? Here's a photo of the card:


texts:
I know <math.h> can be a large amount of code to include, but want to test out something using sinf() on a low-cost PIC.  Is there a slimmed down version of math.h that is being used by the XC8 Compiler?  Why is neither sin() or sinf() defined?

#include <xc.h>
#include <math.h>

#define DELTA_RAD   0.01

void main(void) {
  float x = 0.0;
  float y;

  while (1) {
    x += DELTA_RAD;
    y = sinf(x);  // <-- ERROR on this line

    // Do something with y
  }
}


texts: Purpose of capacitor across transformer in AC-DC power supply?

texts:
I have been looking to buy a AC-DC 5v power supply module to power a mains relay in a circuit I am making. I came across a couple of different models on eBay and am trying to understand their basic working design.

This one in particular has good resolution pictures. To my untrained eye, a lot of thought seems to have gone into the separation of the AC mains and DC output. The underside of the board (see second photo) shows that the PCB has been milled under the yellow thing (transformer?). However there are two other components next to this transformer(?); on one side is a black chip which I believe is an optocoupler (I looked up a part number from another photo I saw of the same board), but on the other side is a capacitor labelled C5.

My main question is what is the purpose of this C5, given that it seems to be going from the AC side to the DC side? Wouldn't that defeat the purpose of the separation? My guess is that the larger capacitors provide filtering, but I can't work out what C5 is doing there.
Secondary questions are how I should approach understanding a circuit like this? Is this a common design for a AC-DC power supply? Could you explain in simple terms what this circuit is doing?

Here is my guess of the circuit functioning: The power comes in and goes some kind of filtering and over-current protection (NTC thermistor). Then it passes into a full-wave rectifier (D4) and the black coils (another transformer?), in some order. I assume then that after this the voltage is a bit lower. The 400V cap on that side helps smooth this rectified output. There is an IC just visible on the top of the board under the black coils which I'm guessing does some PWM with feedback from the optocoupler driven by the DC output; this feeds the yellow transformer which then somehow induces a DC voltage on the other side (I thought that transformers only did AC-AC, but maybe this is not right?) Finally the output, which should be 5V at this stage, goes through some final caps for filtering and into the optocoupler for feedback. Is any of this right?

For what it's worth, the other power supply module I was looking at was this one which is a bit cheaper, but doesn't seem to have the same level of input filtering or isolation (also, no black coil thing?)


texts: Atollic + STM32F4 + ST-Link v2 connection problem "Unknown MCU found on target"

texts:
I currently have a problem with the connection between the debugger ST-Link V2, ARM Atollic 8.0.0 and a custom board with STM32F469. The Atollic and the ST-Link utility believe the Target is halted (and can't load programs or debug), the ST-LINK_gdbserver and the ST-Link utility can't recognize the target device but the ST-Link Utility seems to be able to connect to the debugger with the Hot Plug mode, although a Read Out protection was somehow enabled, and can't erase flash.

When trying to start a debug section, the Atollic console shows the following:

  Target not halted

  Error in initializing ST-Link device. Reason: Target not halted.

While a message box with the following warning appears:

  "Error message from debugger back end: localhost:2000: The system
  tried to join a drive to a directory on a joined drive."

The Atollic settings are the default ones. I also tried changing the gdb server port to 2000, but still the same result.

This error doesn't allow the debugging or loading of .elf files. I already tried to do the following:

Turned the ST-Link on and off.
Turned the computer on and off.
Updated the ST-Link firmware.
Updated the computer drivers for the debugger.
Tried the ST-Link_gdbserver server and client
Installed ST-Link utility
Tried erasing the FLASH memory (Utility popped error saying "Read out memory enabled" and can't enter "Connect Under Reset" mode)
Tried reprogramming the board, but it showed me "The elf loader file
is not accessible." (Since Atollic only outputs .elf files, I
tried saving a .hex file from the STM32 ST-LINK Utility, and used
that one)
Tried the ST-Link_CLI interface

After this, I also tried to run the ST-Link_gdbserver to see if I could get a different response, but all I got was the following:

  "Target unknown MCU target

  Error in initializing ST-Link device Reason: Unknown MCU found on
  target"

On the other hand, when trying the ST-Link utility, when running from "Normal" or "Connect Under Reset" mode, the utility pops a message saying stating:

  "14:53:37 : Can not connect to target!
                    Please select "Connect Under Reset" mode from Target->Settings menu and try again.
                    If you're trying to connect to a low-frequency application, please select a lower SWD Frequency mode from
  Target->Settings menu. 14:53:41 : Can't halt the core"

But, when running on Hot Plug mode, a connection is made available. What's interesting is that the Device ID is not recognized, nor is the Device Family.

Although the FLASH memory cannot be erased due to a Read Out Protection, this read out protection cannot be disabled with "Option Bytes", an error message pops up stating

  "Could not set Option Bytes!,  Please reset the target and retry"

I believe the debugger can't recognize the MCU, and therefore a read out protection is interpreted somehow.

I don't currently have access to the hardware connection between the ST-Link and the board, so, besides from a bad connection, I'm not sure what could be wrong.

In short, I'm unable to read or write the MCU, I get "Can't halt the core", "Unknown MCU found on target" and "The system tried to join a drive to a directory on a joined drive" errors from different software.

Im running on Windows, Atollic 8.0.0, STM32 ST-LINK Utility v4.1.0.0, STLINKUSBDriver.dll v5.0.2.0, ST-LINK_CLI v3.1.0.0


texts: 60Hz "click" or clipping noise when differential amplifier is surrounded by salt water

texts:
I am a graduate student attempting to take electrophysiology recordings from a lobster under water.  In the current set up I am using, two differential amplifier boards are attached the the lobster's back in waterproof casing, with a transmitter and power source in a float being towed around the water surface.

The amplifier boards function properly for bipolar EMG recordings when the lobster isn't in the water, but once the lobster is submerged with the amplifiers on its back, I pick up very large amounts of sinusoidal 60Hz noise as well as a 60Hz "clicking" noise (see attached image).  The sinusoidal 60Hz noise I can filter out post recording, but I haven't found an effective way to remove the clicking noise.  Both are drowning out the desired physiological signals.

NOTE: the amplifiers have bandwidths of 200-1000Hz, but no 60Hz notch filters.  I've run trials with the reference electrode in the salt water, but also bipolar tests with both electrodes placed in the target muscle tissue.

From what I've read I imagine the salt water is amplifying the ambient 60Hz noise, which causes it to increase in the recording once the amplifier is submerged.  However, I'm still trying to figure out what about my circuit may be causing the clicking/clipping 60Hz noise.  Please let me know if you have encountered noise like this in the past, and if you have any advice on how to address it!


texts: how to get the line voltage of 3 phase delta circuit with power factor known at first?

texts:
In the following picture, it shows that a black box at right. the circuit inside the black box is a 3 phase load balanced delta connection circuit. the line voltage of it is 500V and the power factor of it is 0.8 lag.
then, I wanna get the voltage difference between A and B.

In the second picture, it shows the formula to get voltage wanted. However, I don't know why that there is a 3^(1/2) inside the formula. Can someone help me?

BTW, don't use the trick to change the delta circuit to star connection circuit. even though I know that it will be much easier to get the answer. I just wanna know how to get the voltage between A and B by delta connection.


texts:
We are trying to produce a sound wave with speaker. We also need to be able to control the frequency (we don't have specific numbers, about 50-500Hz).

As far as we are concerned we are looking for a function generator or a VCO (voltage-controlled oscillator).
We would love to know which specific component we need.

We will synchronize this sound wave's frequency with another timer controlling an electromagnet; information about this connection will also be helpful.

Please take into mind that I don't have much electronic knowledge (learning physics in school, including electromagnetism).

EDIT:
What we are actually trying to achieve is to make two sine sound waves. One is constant and the other can be changed by hand with a potentiometer or so. For example if the constant is 440Hz, the other can be changed between 170Hz to 270Hz or something similar. Another timer will turn on and off an electromagnet, it will be turned on and off with a frequency linear to the changing sound wave's frequency.

Thank you


texts:
Im desiging a circuit with a binary counter which rates it's maximum count frequency in terms of load capacitance.

Im quite confused and having a lot of trouble wrapping my head around how to calculate this.

The input to the counter im using is a typical CMOS Inverter Oscillation Circuit shown here, with the output connected directly to the clock input of the counter.

The data sheet of the particular inverter im using specifies the input capacitance as 3.5pf, and the load capacitance of the crystal can be tuned (currently 8pf), but I cant work out how to determine what the total output capacitance of this circuit is?  Which im assuming is what the load capacitance to the counter will be.

I plan to use a SN74HCU04 inverter and this binary counter.  The binary counter specifies the maximum frequency in terms of load capacitance on page 6.


texts: using a multiplexer for a high dynamic range current sensing

texts:
I am working on a project in which I am supposed to do current measurements for a sensor node.

the range of the current varies from 0-30 mA
the sensor node has two modes:
 1. active mode (maximum value is 30 mA as stated from the datasheets )
 2. sleep mode  (maximum value of current during sleep mode is 35 uA  )

to be able to detect up to 1 uA in this system, I need an ADC of a dynamic range of 30mA / 1 uA = 30,000:1 while my ADC is only 10 bits ADC which will only provide 1000:1 dynamic range or to be more accurate, 1024:1 dynamic range

I decided to take two different sets of readings, one during the active mode, and another one during the sleep mode. this way I will have a better accuracy for the sleep mode ( measuring current in micro-Amps). a multiplexer will choose between the two modes as follow

during the active mode, my shunt resistor is going to be small, lets say 1 ohm, that means 1 mA, is equivalent to 1 mV, this 1 mV will go through a differential amplifier with 200 V/V gain to be 200 mV, for my maximum 30 mA , voltage will be 30 mV when amplified it will be 6V.

during the sleep mode, I am using a larger resistor 250 ohm so that 1 uA will produce 250 uV which is .25 mV, and this 0.25 will then go to the 200 V/V gain to produce 50 mV which is measurable using my 10 bit ADC.

my question is, is this really a better way of describing the system? and will it work to get current measurements for this sensor node that is a part of a Wireless sensor network ?
and what kind of multiplexers needs to be used? is there such a thing as switching speed ?


texts: Common source amplifier with current mirror active load

texts:
I am reading about common source amplifier with a current-mirror active load from the book Analog Integrated Circuit Design by Tony Chan Carusone, David Johns, Kenneth Martin.
I am confused by the yellow sentence below:

For a fixed bias drain current,ID , the effective overdrive voltage is reduced by increasing the device width W.

From the formula that relates between Veff and W/L it is clear that Veff is reduced if W is increased. However, from the circuit on the picture, the basing network for Q1 is not shown.
How to make the basing network for Q1 so that Veff of Q1 decreases when W increases?


texts: How to sharpen blue LED voltage-to-current knee at 3.0 V?

texts:
I want to use blue LED as simple 3.0V nominal vs brownout indicator. It will be mounted on tiny proto board and will be plugged into rails or other various parts of breadboard. I want to make same plugs for 4.9V and 1.8V.

The LED is bright at 5mA 3.2V. And it is still visible at about 2.2 V but very dim. I want it to shut completely at about 2.8V and stay bright at 2.95..3.1V.

How can I improve sharpness (steepness) of threshold with any amount of simple BJTs, resistors ?
Thank you.

Answer: as accepted, but with more details for 95% sharp threshold near 3.0V.

Green trace is jump of output voltage on collector of T2, when power is reaching 3V -5%.
Blue trace is a normal diode + resistor current for comparison. Red trace is power voltage. Scale is 3.3V for voltages. For simplicity, consider milliseconds are percents of voltage nominal.

Update after physical implementation: The resulting threshold is 2.92V=dim, 2.96V=bright. The resistors were slightly changed (no 91K in stock), so R1=23.5K(2x47K parallel), R2=2K, R3=82K, R5=270), LED=blue smt one from dead HP laptop.


texts:
My question is about designing a microphone pre-amplifier that uses an electret microphone. I saw a video of Doug Ford on the EEVBlog, in which he shows some pre-amplifiers for microphones.
My question is: does it make sense build a FET pre-amp for for an electret microphone, considering that a FET it's already inside the microphone package?
Eventually, the microphone noise is produced from the FET inside the microphone, so is it pointless to connect a FET pre-amp outside the microphone?


texts: Individual Phase shift provided by Op-Amp in Closed loop configuration

texts:
When comparing the input and output of the Op Amp alone (Vid1-Vid2 and Vo and not Vsupply and Vo) in a closed loop configuration the phase shift is only 90 degrees? Why it is so?
And the Simulation shows its is 90 degrees!!The white wave form is the input of Op Amp (V-diff) and the Red Waveform is output.

Does it implies that the closed loop Op amp individually by themselves gives only 90 degree phase difference?
If so which part of the external circuitry give the remaining 90 degrees to satisfy the known experimental fact that the overall phase shift in closed loop- inverting configuration is 180.

And the circuit diagram of implimentation:


texts: Can someone please help me with this circuit pulled out of a solar led light. The original battery was a lithium iron 3.2 volt battery, and I’m with wondering if I can put in a lithium ion 3.7 volt battery in this circuit. The reason I want to do this is because lithium iron batteries seem to be pretty expensive.The yellow and white wires are from the solar cell, and the battery connects to the bottom right at b+ and b- the board on the left seems to be a motion detection board and is not a part of the charging circuit.


texts: Led bulb lights up even when 1 wire is connected. How?

texts:
I have a blue led light of 4Watt...one wire is connected to the AC source and the other one is not connected(1Live and 1 Neutral)...surprisingly enough the led lights up(very dim though)... how is it possible, we even dont have a closed circuit? Below are the images

When One wire is connected--

When two wires are connected--


texts: USB C Spec Compliant way of splitting power

texts:
I'm trying to get a Y Splitter going on, where one of the sides is passthrough on the CC pins and the other side has a step down/buck converter that can take 5-20v input and always do 5v output. I came up up with this rough diagram but there's a flaw where if USB C passthrough is not connected, the CC pins on USB C upstream remain floating. I think because of default profile this would work but it seems wrong.

What's the correct way of doing something like this?

simulate this circuit – Schematic created using CircuitLab


texts:
I have a project with arduino. Most devices are powered by the arduinos 3.3V source.
But a gsm modem with 5V input and high current consumption cannot be connected with the arduino, because the arduino cannot support such strong current. I use an external transformer for it

Now, if i make a custon pcb for my circuit, to leave the breadboard.

How do i deal with different power sources? (voltages and current consumption)

Can i feed it from a power supply and is ther somnething like a voltage regulator with double outputs that i can solder on the pcb?


texts: Do I need resistor between NodeMCU and TIP122 Transistor

texts:
I have a NodeMCU Dev Board that I would like to connect to a RGB Light strip to control over wifi. I have found a digram on the internet explaining how to connect it up. It includes a 500Ω resistor, but since I don't have any, I want to know if it is safe to not include the resistor and not fry anything.

Diagram:

http://www.esp8266.com/viewtopic.php?f=11&t=12259

I would appreciate your response.


texts: Soft latch switch circuit with buck converter load does not work

texts:
I have been experimenting with soft latch switches. There is one that EEV Blog has developed that only uses 2 NPN transistors and a P-Channel MOSFET. The circuit is seen at 14:44 in this video.
I have connected that to a buck converter and I am observing some strange behaviour. You can find my full schematic below.
The connection is as follows:
USB/12V --> Voltage Selector --> Soft Latch Switch --> Buck Converter

On power up the circuit delivers a 5V to the Vin of the buck converter and it works on regulating it to 3.3V. However when I press the button the voltage at the output of the soft latch drops to ~4.375V and reverts back to 5V when I release the button.
I am monitoring it on the oscilloscope and what I would expect in such a situation is an oscillation when the button is pressed. What I am observing is a fixed DC voltage.
What may be the cause of this? I don't really understand what is going on. Any input would be appreciated.
Improved Edit:
Based on input from  user287001 and Dave Tweed:
It works now however, rapid follow up pushes do not work. It starts turned off, on pushbutton turns on, on follow up push button it turns off. If zou push one more time after that it starts oscillating. So you need a couple of seconds between rapid turn on/off events. But nobody needs such an application.
On connection of inductive load the turn on event happens faster than the turn off. Again rapid turn on/off is not possible. One has to wait aproix 1-2 secs between rapid pushes.
Modifications to circuit:

Removed C4, in finalised version I will put it on the Input of the latch circuit.
Added a 33kohm between B and E of Q4
Flipped the D and S of Q7 and Q5.


texts:
Hello everybody

This circuit is a high shelfing-Filter. I do have trouble calculating the maximum cut / boost. I know that the devider (R3 and R4) sets the maximum cut and boost  but how do I calculate it exactly?
Thanks for your help!


texts: can aluminum foils increase the boost the range of nfc reader?

texts:
I have been working on a project where I have to read data from an NFC tag and store the information locally.

Currently I have a range for the NFC tag of about 5 cm. The tags will be present inside a case with a glass lid on one side which is where the NFC tag will be facing out. Without the glass lid I am able to read the tags successfully but when I out on the lid and try to read it works 50% of the time and fails the rest of the time.

I have recently read that by partially shielding the antenna and making it directional we can increase the range of RF signals like wifi, bluetooth, etc.

I would like to know if the same trick can work with NFC readers as well? Is this a good method to increase the range of NFC by another 1 or 2 cm to read the tags?


texts: Can someone convert this circuit from 12VDC to 6VDC

texts:
It is a small sensor which activates relay when there's dark.

I just want that circuit to work with 5Vdc or 6Vdc.


texts:
Why there are IPC footprint Levels A and B?

I believe it has to do with the standard related to tape and reel feeding, but I will appreciate a more elaborated answer.


texts: Isolated MOSFET gate driver VCC and VDD power suppl

texts:
I am planning to use UCC21520 for HV SiC MOSFET based full bridge  design. My operation frequency would be around 100kHz.  I selected UCC21520 in order to achieve the isolation between the power and signal side. However, during design I am stuck at deciding how to select power supply for the VCC and VDDA/B.

http://www.ti.com/lit/ds/sluscq2b/sluscq2b.pdf

My questions are following:

If I use same power supply for VCC and VDDA/VDDB ( say 15V) would that work? I would use a laboratory 15V power supply ( isolated) and connect the ground of the power supply to the ground pin of the IC.
If I indeed need to use two power supplies say 3,3V +GND1  for VCC and 15V +GND2 for both VDDs, how do I deal with two new ground points? and how would they connected to the GND pin of the IC.
Speaking of grounds, I am planning to carry over the PWM signal to H-Bridge board from another PCB that has its own auxiliary power supply. I will carry over the PWM signals and and respective ground ( SGND) to the H_bridge PCB. How should I deal with this SGND with respect to aforementioned GND1 (and /or GND2).

Since, aim of using the IC is to achieve isolation from SGND and PGND, I am really confused how to deal with other grounds ? Your kind support is solicited.


texts:
I was looking at the INA225 datasheet and wondering how to appropriately design the PCB for this device.

My question is rather simple, the shunt resistor will be far away from the microcontroller and there will be switching regulators along the way, and I want to avoid using an external ADC, so I have two options:

1) Place the INA225 close to the shunt resistor and route the analog output to the microcontroller.

2) Place the IN225 close to the microcontroller and route the kelvin connection like one would route a differential pair.

I'd like to know which one is better considering since the signals may pick up a lot of noise along the way. If possible, please provide explanations on why one approach is preferable over the other.


texts: Problem setting registers (SPI) [NodeMCU fw, nRF24L01+]

texts:
I can read registers somewhat fine, but when I try writing to a register in the nRF24L01+, it either crashes and I have to pull it out of the board, or the register becomes all 0s, and I can't reset it back (so I have to pull it out to reset it)...

local buffer
local address = 0xE7E7E7E7E7
local addrlen = 5
local misolen = 64
local command = 0x06
local datalen = 8
local data = 0x0A

spi.setup ( 1, spi.MASTER, spi.CPOL_LOW, spi.CPHA_LOW, 8, 80, spi.FULLDUPLEX )

spi.transaction ( 1, 8, command, addrlen*8, address, datalen, 0, misolen )

for i = 0, misolen-1, 1 do

    if ( i == 0 ) then
        buffer = spi.get_miso ( 1, i, 1, 1 )
    else
        buffer = buffer .. spi.get_miso ( 1, i, 1, 1 )
    end

    if ( (i+1)%8 == 0 ) then
        buffer = buffer .. ' '
    end

end

print ( buffer )

It's probably a stupid thing, but it's my first time with SPI, and an nRF24L01+, and I don't have an oscilloscope, and I've been fiddling with this for two days now, and I'm out of switches and knobs to turn, so I turn to you...

Any help much appreciated,


texts: In Parallel resonance circuit mentioned below, is current equal for Resistor and Inductor?

texts:
The parallel capacitor will have current leading voltage by 90°. In the case of Resistor and Inductor (which are in series with each other but they both are parallel to capacitor). Now, the upper half of circuit(containing resistor and inductor) should have same current as per intuition(since they are in series). But if they have same current through them then, Current through resistor(ILcosθ) and current through inductor(ILsinθ) must be equal,which implies θ=45°. This concludes that whatever inductance be in the circuit, current in upper half will always lag voltage by 45°. This seems somewhat mistaken.

When I consulted to the teahcer, he said that the resistor and the inductor will have different current through them, (due to inductor behaviour against change of current). But isn't this against basic law that the components in series will have same current thorough them?

So, I wanted to be sure, what actually is happening in the circuit?


texts: My Mastech MY-64 DMM shows incorrect voltage for specific selected option

texts:
My Mastech MY-64 DMM suddenly started showing incorrect voltage on DC 20v option only. When I select dc 200 option it show correct value, even a aaa battery in 2v dc option show correct voltage.
Why is only 20v dc option showing incorrect reading, is there any way to fix this.
P.S. I changed the multimeter battery to a new one, didn't help.


texts: Op-amp voltage buffer attentuates the input

texts:
I'm using the LPV821 op-amp (http://www.ti.com/lit/ds/symlink/lpv821.pdf) for a buffer circuit (voltage follower). Below is my circuit, where the desired output has the same voltage as the input (V2):

The circuit works only with ideal source (little or no impedance between V2 and non-inverting pin). But it does not output anything for my non-ideal voltage source (When there's a large resistor between V2 and non-inverting). I was wondering if I could have some suggestions on why I'm not getting the desired output.

NOTE:

1- The V+ - V- supplies for this op-amp cannot be more than 4V.

2- This circuit works as expected with LM741 op-amp. The only difference is that I removed R12 because LM741 needs higher supplies.

UPDATE:

Below are my observations in order to figure out the problem:

1- When I connect the positive (1.4V) and negative (-1.4V) supplies to the op-amp and disconnect the other pins, all the pins are at 0V.

2- When I connect an ideal source (no R10), ALL the pins have the same voltage as the input (V2).

3- When I add the R10 (700KOhm), the output goes to zero. I also measured the voltage at the non-inverting pin and it's at zero, even though the input (V2) was not zero.

4- When I paralleled a 100K with R10 the output was almost like input: a sine wave with minor drop in the amplitude.

5- When I replaced R10 with a 200KOhm resistor, the output was substantially attenuated but not zero.

From 3,4, and 5, I can conclude that the current in the non-inverting pin is pretty high and this current causes a voltage drop across the R10. I don't know why this happens.
Maybe the op-amp is damaged?


texts: How do causality and stability affect the response of a linear time-invariant system?

texts:
Suppose that there's a linear time-invariant system with the following transfer function:
$$H(s) = \frac{1}{3(s-2)}-\frac{1}{3(s+1)}$$
If the system is causal and stable, I can determine \$h(t)\$ by simply evaluating the Laplace transform of \$H(s)\$.
Now, if the system is neither stable or causal, how would I determine \$h(t)\$? I can't figure how the response in time domain is affected by causality and stability, in general.


texts:
I'm trying to design a custom intelligent electronic cigarette battery, but I'm more of a programming guy. I know basic electronics, but I need some help with the details.

I've sketched up an outline of my future ecig, with STM32 as a core, high discharge current 26650 battery, 2" e-ink display and some powerful DC-DC converter like PDT012A0X.

But I'm unsure how to go on about charging that thing. I want it to have embedded charging circuit taking power from the USB port. But I also want to have an ability to use it while it's charging.

There can up pretty high currents running from DC-DC converter to the coils (probably up to 10A), so that's where I find my knowledge lacking.

How would one go about that problem? Should I stop the charging process when the coils are firing up? Or it would be OK for it to continue?

I would really appreciate your help or some links where I can educate myself more.
Thanks.


texts: Find Io(t) of RLC circuit (from Electric Circuits, Nilsson )

texts:
My question is from the Electric Circuits, Nilsson 10th edition.

My solution is

For \$t < 0\$, we get \$i_o(0) = 2 \mathrm{A}\$ and \$v_o(0) = -400 \mathrm{V}\$.
For \$t > 0\$, the circuit becomes a series of C, R, L. (suppose \$i_c\$ go up, \$i_L = i_o\$)
$$
 i_c =C {dv_o \over dt} = i_o = i_L.
$$
So I get
$$
v_o+CR {dv_o \over dt} + LC {d^2v_o \over dt^2} = 0,
$$
So I get
$$
{d^2v_o \over dt^2} + {R \over L}{dv_o \over dt} + {1 \over LC}v_o = 0
$$
By solving 2nd ODE, we get

\$v_o = A_1 e^{-250t} + A_2 e^{-1000t}\$, and then by initial condition, we can get answer.

Is the above true?

The solution gives the same ODE for \$i_o\$ not for \$v_o\$. Not sure which one is true.


texts: How do I simplify this equation using boolean logic?

texts: I tried using reduntion, absortion and consensus but all of them were impossible to use.


texts: How do capacitive screens work with rubber head stylus?

texts:
Now I kind off know that Capacitive Screens have like capacitors built into them that create an electrostatic field. Now whenever a thing that can carry charge or a conductor touches it distorts the field. Then the processor somehow calculates the location of touch

The thing is when I use a battery and try to use it as a stylus the -ve side does register touches but not the +ve side. Can anyone tell me why this happens?
Edit : Got the Answer It was cause there was not good amount of surface in contact.

Is this the same reason that when I connect a wire to the cell and try using it to distort the field but it doesn't sense it?

And how do these rubber tipped stylus work? They are not conductors right?

I know there are many similar questions out there but I didn't find any of them helpful. Any articles or anything will be helpful.


texts:
I replaced some old electromechanical relays by those solid state relays from Wieland to improve the switch speed of my system but I can't manage to switch off the solid-state relay.

Here is the relay schematic as presented in the datasheet:

I am trying to control the relay with a digital output comming from a PLC (24V) connected in A1 while with the ground is in A2. My objective is to control the release of pulses coming from an encoder (+13) and going to a camera (14). When the PLC output is turned on, the LED in L1 brights up and it shuts down when the PLC output is turned off. Now, even when the light is switched off (or when I remove the cables) pulses pass from +13 to 14.

I have a quite basic knowledge in electronics and was expecting I could use the same circuit as with my electromechanical relays. I am aware of the problems related to triacs when people buy AC solid state relays instead of DC ones but I don't think this is the problem here as the constructor clearly state it is made for DC.

Do you have any idea why the relay never switches off ?

In addition, I suppose it is probably not relevant but...

What does represent the half circles on the top of +13 and below -A2?
In the datasheet, the Nominal input current is between 4 and 6 mA. Does that mean that a bigger current would pass the relay no matter the PLC output? Since that value was not specified at the seller's site, I'd be quite surprised that such a discriminating value would not be better advertised.

EDIT:
Here are some voltage measurement I made as requested by user Transitor.
Without any load (relay not connected to the pulse divider):

When the PLC output is off, from pin A1 to A2: 200.0 mV
When the PLC output is on, from pin 14 to 0V: 0.5 mV (so ~0V)
When the PLC output is off, from pin 14 to 0V: 0.0 mV
With a load:
When the PLC output is off, from pin 14 to 0V: 3.7 V
When the PLC output is on, from pin 14 to 0V: 10.27 V
--> that should be interesting as I suppose a circuit could be used to lower the voltage so that my device is not detecting it when the plc output is off. Still I don't know why this small voltage exists.


texts: Best approach to design or implement short circuit protection?

texts:
I'd like to implement a safety mechanism in my circuit to avoid overvoltages/overcurrents in the event of a short, but am unsure as to what what the most robust or appropriate design approach would be. The primary rail is +15V and I want to limit the power to 15W.

After looking around, it seems that this should be pretty straightforward with discretes (e.g.link here), but would this be robust enough? Are there tricks/pitfalls in scaling as necessary?

I thought that there may be ICs for what I'd imagine is a common problem, but I'm unsure of what the appropriate one would be: inrush current limiter? surge suppression IC? power NTC thermistor? Something else entirely?

Or perhaps the simplest solution is a fuse, but that raises other questions as well. Will it trigger quickly enough? Does it need to be resettable?

Any help steering me in the right direction would be greatly appreciated.


texts:
Is one side of R050 connected to OUT- ?
To nut for the acrylic housing would bridge the little gap there - is that a problem?
Thx.


texts: fourier transform for non-stationary signal

texts: I have read that for non-stationary signal we break the signal into smaller segments by applying a window function . My question is how this can help to make the signal has a fixed features or to became stationary signal even it's not?


texts: Is it acceptable to use 1uF decoupler on a 7805?

texts:
I am feeding an arduino, presently through its Vin pin, with a 0.9V drop on its onboard regulatorZ I'd of course like to feed it via its 5V pin, which has a strict upper limit of 5.5V. I don't have any 7806/7808s, and already soldered the 7805 in place. I also have no 0.1uF caps, my nearest value is 1uF. The 7805 briefly spikes to 6-7V when powered up. I need to absorb that spike - can I get by with a 1uF cap on the output?

I am sorry for this trivial post, but I would be very sad if my arduinos died. I have already ordered 7808s and more suitable caps.