texts: How do I build a one shot non-retriggerable pulse generation circuit with 2 triggers?

texts:
I'm kind of a noob when it comes to electronics (I'm mainly a computer programmer), so please bear with me. I want to construct a one shot non-retriggerable pulse generation circuit that has two trigger inputs. The inputs on the triggers are going to be persistent signals (not just pulses) so I would like the circuit to only generate a pulse when one of the input lines is pulled high, and not generate another one until either the second input line also gets pulled high, or the first input gets pulled low and then high again (this behavior may be easier to achieve by using two pulse generators and tying the outputs together, but in this case it is still important that each pulse generator only fire a pulse when the trigger signal goes from low to high, and not continue to generate pulses if the signal then remains high for a while).

The reason the trigger signal may remain high for a while is because the triggers are going to be user-operated. For example, let's say that each trigger is connected to a button, and the output is connected to an LED (just an example, not what I actually intend to use this circuit for). If the user presses either button, the LED should flash once, regardless of whether the user continues to hold down the button after pressing it. If the user then presses the second button while still holding down the first one, the light should flash a second time; the light should not flash again until the user releases at least one of the buttons and then presses it down again.

I hope I'm making myself clear as to what I need this circuit to do. As I said before, I am mainly a computer programmer, so I will provide some pseudo-code below if it helps to understand what I am asking.

IF (trig1.prevState = 0 AND trig1.currentState = 1) OR (trig2.prevState = 0 AND trig2.currentState = 1) THEN
output.currentState <- 1
ELSE
output.currentState <- 0
ENDIF

I am not against using a microcontroller, but only if the delay it introduces is negligible (I need the pulse to occur nearly the instant the trigger line is pulled high).

As I said, I'm kind of a noob, so I would really appreciate it if someone could provide a full schematic of the best way to build this circuit, although any suggestions at all are still welcome. I don't want this to be too expensive, so no super expensive parts please.


texts:
I'm looking for suitable GLCD, so far I have found the RX12864H, however the datasheet describes a lot of voltages and I'm bit confused.

While the VSS and VDD are clear to me, I have no clue what do the V0, XV0 and VG mean. The internet research lead me to using V0 like contrast adjustment, but I still know nothing about the XV0, and the "LCD driving voltage for common circuits at positive frame" isn't very understandable for me. The datasheet specifies the Vop for typically 10V, which for me looks like really big value for the LCD powered by 3.3V, also I can't find any min/max rating for the VG.

Snip from the datasheet:

The full datasheet can be found here: Datasheet


texts: Powering 28 LEDs in series by 220VAC - simple stabilizer

texts:
I have a home-made thingy that I would like to use as a lightning in my living room. It contains 7*4=28 LEDs (red, 1.86V, 20mA), originally in 7 groups by 4, each switched on seperately, powered by 12VDC.

Now, I would like to power the whole thing by 220VAC. I thought of using a simple stabilizer as on the following schematic:

simulate this circuit – Schematic created using CircuitLab

If the stabilizer were optimal, I would get (220-28*1.86) / 8.2k = 20.4mA, which is fine for 20mA diodes I think. However, I have some issues:

Is my idea of ACDC converter correct? I have a bad feeling that the capacitor is somehow the 1st thing in the circuit and that it's not correct.
How well the signal is stabilized by such layout? Especially at the beginning, there might be high currents through the bridge, can't there?
Can I rely on the LEDs having moreorless correct voltage drop? It seems that 0.1V per LED would make a little difference in the current so I think it should be safe, but I'm not sure.


texts: How to connect together: Raspberry, Arduino, PC PSU, Usb Hub, Usb Hdd - without issues?

texts:
A pc psu provides power for:

arduino uno (via de standby 5v power + ground so it always has power)
raspberry pi (via a 5v + ground connection)
usb hub (via a second 5v + ground connection)

Arduino is connected from an analog port to the psu POWER-ON connector to shutdown / start the psu after a button press has been detected. (how to detect pi powered off state is for another day).

Can there be any problems here?
I would eventually like to use the psu 12v to power 3 to 9 rgb leds. Can i do that?
i know all electronic things connected together should have a common ground. Does a psu have a common ground for all black wires? or should i use power from the same pair of wires for all things?

ethernet/hdmi cables to the pi not shown but they will be connected.
i've read that it would be better with 1ohm resistance on the green wire (psu power on)


texts: How to connect the crystal to generate a simple pulse?

texts:
I have a 4Mhz (YIC 4.000006 ) crystal. I would like to generate a simple square or sine wave (whichever requires the least components), only for learning purposes, no practical use. I want to be able to see the output on a oscilloscope.

I can't seem to find any tutorials that explain how the crystal is connected/works. I believe I'm using the wrong search terms. Whenever I search for a 'crystal oscillator' I get results of complex schematics (I'm a beginner), but I'm looking for the most primitive way to get some kind of output out of the crystal as I'm trying to learn how it works, but now I'm completely clueless on how to even connect it.

What is the most primitive way using only the standard components to generate any kind of pulse/wave/output from the crystal, so I could pick it up using an oscilloscope? Thanks!


texts: Determining the potential difference between two points

texts:
In the figure above, I want to determine the potential difference between the points d and c, where there are two batteries connected in parallel, and two resistances connected in parallel too.
I was given that the potential difference between f and d is 12Volts, so the current entering the parallel connection is 3A(using ohm's law).
And using Kirchhoff's laws, (Vb)₃ is 10Volts.
I don't know how to determine the PD between d and c, I would appreciate any help or explanation.
 And that is what I think in:

  the voltage of the upper wire: V=1*7=7 Voltas
  And V=Vb+Ir (since the battery recharges) so V=8+1=9
  And Vtot=7+9=16

And the voltage of the other wire:

  V=IR=2*2=4V and V=Vb-Ir (since the battery discharges) so, V=10-2=8V and Vtot=8+4=12V

But I still don't know how to determine the whole PD between d and c.


texts: Connecting TDA7052 with a microcontroller

texts:
I am planing to use a digital I/O off a micro-controller unit (MCU) and connect it to a TDA7052 input. The TDA7052 datasheet specifies a maximum input voltage of 0.65 V. And since the MCU output bit give either 0 or 5 V, there needs to be a interface circuit between the two. A couple of options come in mind:

Use PWM (pulse width modulation) with an RC filter. The PWM output's duty cycle will have to be limited (by software) to 13% (\$0.13 \cdot 5\mathrm{\, V} = 0.65 \mathrm{\, V}\$).
Use an op-amp to reduce the voltage to a max of \$0.65 \mathrm{\, V} \$.

Any suggestions on which method would work better? I would also appreciate it to know if there are other (perhaps better) options. I don't have the components to try them out as I am planning to order them of the web. I do want to connect the MCU to an 8 ohm speaker and NOT A buzzer.


texts: what is the temperature equilibrium for a copper conductor conducting 4000 Amps

texts:
I have a copper conductor with a total resistance of 1 miliohm and a passing current of 4000 Amps.

I want to know what the temperature equilibrium is for a conductor in the electrical grid (conductor is located inside medium voltage switchgear). At what point is the temperature it creates equal to the temperature it loses to the environment?

The cable is inside a container full of oil (used for cooling). as said before it has a total resistance of 1 miliohm and a current of 4000 Amps passes through the conductor. the cable has a diameter of 2.5cm
the temperature of the environment is 20 degrees. time can be considered infinite for the cable cannot be turned off.

when will the temperature stabilize? has my conductor melted before it could reach that point?


texts:
I am using the TI SN65HVD230DR CAN transceiver on two separate CAN buses between three microcontrollers (MCUs) -- two are on the same board, and one is off-board.  This transceiver includes a Vref pin:

  The Vref pin (pin 5) on the SN65HVD230 and SN65HVD231 is available as a VCC/2 voltage reference. This pin can be connected to the common mode point of a split termination to help further stabilize the common mode voltage of the bus. If the Vref pin is not used it may be left floating.

Since the datasheet is terse with Vref details (How is it generated?  Can two transceivers have Vref connected simultaneously?) I am not certain how to connect this pin.  My intuition is to only have one transceiver connect Vref on the on-board CAN bus (CAN2 above) since the MCUs/transceivers are only a few cm apart.

For CAN1 between MCU1 and MCU3 (off-board) there will be 1~2 m of cable between them, so with the increased impedance my intuition is to connect Vref on both transceivers.  Is this a fair assumption?  Is there a better way?

EDIT:  Forgot to mention I am using the split termination scheme at all transceivers.


texts: Lattice FPGA: Mach X02 7000 Can it be used for DSP?

texts:
I have a MachX02 7000 having 6800 LUT's.
I want to implement DSP algorithm involving floating-point DSP algorithm on 2 14 bit ADC input data.
Is it possible to perform on this FPGA with low LUT's, No DSP blocks and 2-bit arithmetic function support per slice of 2 LUT's.


texts: For my Engineering project this semester, I proposed a luggage tagging system using integrated RFID. I know you're all thinking yes this has been done, but for my final presentation I'm looking for a way to present this to my professors thats not outrageously expensive. I've found readers and writers but they're low frequency, short distance and still relatively expensive. All I need is something to scan and read from a distance (not a bar code) and then show a series of numbers or letters on screen (laptop, small LCD) etc. I'm looking into an Arduino setup. Suggestions?


texts: Why does it matter which way I put a battery into an electronic device?

texts:
If I take a battery, some wire, and a light bulb and hook them all in a circuit that would create a current and light the bulb. If I turned the battery around so the terminals were switched then I would have a current in the opposite direction, but the light bulb would still light.

So why doesn't that principle hold for more complicated devices like a flashlight?


texts: Why my water level indicator outputs low to microcontroller even after disconnecting the positive +5V?

texts: The problem occurs only if leads are kept immersed in water.


texts: Designing Discrete differential inputs Amplifier

texts:
I am trying to analyse a discrete differential amplifier circuit by answering some question. I have done the analysis of the input stage, I would appreciate if I can get some feedback on my approach.

Here is my approach for the input stage

Here is the other part of the differential amplifier

Here are the calculations for the input stage


texts: What do smartphone manufacturers do differently with their cameras than the Raspberry Pi module camera

texts: There is a huge difference in quality between the image/video taken by the latest iPhone or Samsung smartphone compared to that taken by the Raspberry Pi camera module. What is different about the smartphone hardware or software that enables such superior image/video quality when compared to the Raspberry Pi camera module?


texts: Can you effectively run lower power 5V TTL signals through a large piece of metal?

texts: Is it possible to run a standard TTL signal through a very large piece of metal?  For example, say 1-3 meters of metallic rebar?


texts: Op-amp with constant output voltage (Peak to Peak)

texts:
I am new to opamps and am trying to amplify a variable frequency sine wave to a constant 5V peak-to-peak using opamps.
The input signal amplitude changes with frequency, but the opamp should always amplify to 5V peak-to-peak.
Aside: The input comes from an AD9833 waveform generator IC, and it's p2p is somewhere between 32-600mV. The output dfrequency ranges from about 1kHz to 2Mhz.
I could not find any information on how to accomplish this, or am just searching incorrectly.
I realize in a standard non-inverting amplifier circuit, I would just have to somehow control the feedback resistor value, meaning only the voltage divider on the inverting input would have to be controlled.
Kind of like this variable-gain amplifier.
I was thinking about doing it the following way:

Buffer the output of the opamp so as to not disturb the signal
Convert buffered signal to an average DC signal using a capacitor and resistor
Use this DC voltage as feedback

However, this seems extremely complicated and I am no sure this will work at all.
Here is a sketch of it:

Is there a standard configuration that will accomplish this without reinventing the wheel?
Did I just come up with something silly and there is a more obvious way?

I appreciate your help.


texts: Is there any symmetry in this opamp ckt?

texts:
By thevenizing the at the inverting input, I notice that when the variable resistor equals \$R_2\$ the output \$v_{out}\$ becomes \$0\$. Can this result be "seen" with out doing the algebra?

I feel there is some symmetry but I couldn't quite figure it out. The top \$R_2\$ resistor is connected to \$v_{out}\$ but the bottom variable resistor is tied to ground. This is throwing me off. Any help?


texts: Why does it take several seconds of time for the photodiodes to come out of saturation?

texts: I am currently studying about photodiodes and came across this fact that photodiodes take quite a bit of time to come out of the saturation. What really happens during this time (after it is saturated and time it takes to come out of saturation)?


texts: Isolated power supply to the DIY projects

texts:
I am very new to electronics and electrical engineering background. I am working in an electronics engineering job for the past 4 months.
My question is: what can I use or what is the best way to have at my workshop at my home for the DIY projects so that even if a short circuit happens in my experiment that does not shut off power to the rest of the house.
In my lab, we use an isolation transformer. Is it possible to create an isolation transformer from a normal transformer?


texts:
I am a bit confused about Figures 3 and 4 in the datasheet of the DMN3010LSS MOSFET transistor: Why do they show how the Rds(on) varies as a function of the ambient temperature TA?

I thought that the junction temperature Tj was important for the Rds(on).


texts: Any program to simulate electric motor performance?

texts:
Does anyone know any program that I can use to simulate the performance of an electric motor?
I'm trying to design one from scratch and I would need tools that don't make me spend a lot of money on experimental tests.
if anyone knows something they appreciate it very much


texts: Multiple audio inputs driven by one MP3 player output

texts:
I wish to make the following design using TPA3122D2N as  a DIY project.

Is it possible I make two or three of these units and share the MP3 players output among all three inputs on the TPA3122 IC?
If not, what sort of modification is required?

Appreciate all responses.


texts: Why is it so hard to get waves through the earth and ocean?

texts:
Quoted from the source Crystal sets to Sideband, the author said if you have an ohm meter measuring across the whole earth, the meter would display only 300 ohms.

A while ago, I asked about earth being used for communications. They answered I could go 100 meters with low frequencies, but this doesn't make sense if the resistance of the earth is so little.

Couldn't a single-wire signal be transmitted through this to pick up on the other side of earth?

If I had an audio cable, and a 300 ohm resistor in series, Im sure I could amplify this signal and still pick it up easily.

 audio ------------ /\/\/\/\/\/\--  |           | -----
                      300 ohm       | Amplifier |        Speaker
 source---------------------------  |           | -----


texts:
I am planning to build a device that includes an high power RGB LED (either a lightsaber or a decorative object for the girlfriend - I still have to decide), where high power means about 3x3W. I've found this little guy from Texas Instruments that seems to perfectly suit my needs, that's a sequential driver so I'll need only one inductor and one diode for the DC-DC, it has an I\$^2\$C interface and some other fancy functions.

There are a couple of questions that arise though.

1) Refer to page 4, bottom of the table, where the current accuracy is reported, and to pages 18-19, inductor choice. As per the EC table it seems that the LED current can be tuned from the maximum set by the resistors \$R_{1,2,3}\$ (first page schematic) down to approximately zero, while in the inductor choice paragraph a \$I_{LED,MIN}\$ is calculated and is as high as 600mA. Since my end application would have some 750mA as maximum current that would be unacceptable of course, so the question is: is that \$I_{LED,MIN}\$ another parameter or is it exactly what it seems to be?

2) As I said this is a sequential driver, only one LED at a time can be turned on. Since its target application seems to be pico projectors I am hoping I can hop from one LED to another fast enough to let the human brain do the mix and end up with a beautiful RGB light. To do so I'll need to bang the G,B,RCTRL inputs appropriately, i.e. one LED will be on only for one third of a given slice of time, e.g.:

time: 0  t 2t 3t 4t 5t
RCTRL 1  0  0  1  0  0
GCTRL 0  1  0  0  1  0
BCTRL 0  0  1  0  0  1

where \$3t\$ is the total time needed to turn on each of the three LEDs. Two questions arise then:

a) If \$t_R, t_G \text{ and } t_B\$ represent the time a given LED is on, is it correct to assume that they should be equal, i.e. \$t_R=t_G=t_B=t^*\$? Or I might want to tune them because for example for the huma eye blue seems less bright than red or whatever?

b) My LEDs are rated up to 750mA. Should I set the maximum current for each LED to a higher value because each of them is on only for \$\frac{1}{3}\$ of the time? I think that setting it to 2.25A, apart from the fact that the chip can deliver 2A at most, would burn my LEDs for sure but what about 1A or whatever? The LED I have is this (no advertising intended).


texts: How to measure SNR of a telephone Line? What is the device (without using router)?

texts:
I'm a beginner level eng student. I've just find this place and I need your help.

I need to create SNR detector without using a router login.
So,

Is there any small device to measure SNR by directly connecting phoneline to device? (without using router login)
Can I use arduino to make the snr detector?
If you have knoledge, please explain that what is the best and smallest way to make this.

Please help me. This is for a project!
Thank you all Engineers and other in this place.


texts: Can I connect multiple SN74HC595 shift registers separately (without daisy chaining them) to the same Arduino?

texts:
I'm sort of a newbie to this whole idea of shift registers and the Arduino shift register handling library. I've found many demonstrations online, where shift registers are daisy chained. But I need to connect multiple shift registers to my Arduino without daisy chaining them. My common sense says, Yes! you can, But I'm not quite sure and I don't have that IC on hand so that I can physically build the circuit and test.

I'm really shy and uncomfortable to ask this question to you guys whether if it turns out a stupid question. So.. please mercy on my soul :)


texts: Locate a mobile phone precisely for indoors tracking

texts:
Firstly, I don't know if I'm asking this at the right place, so excuse me if it's not.

Suppose i want to track a mobile phone in a local area, lets say a large hall of 200 m x 50 m, using any external beacons required but ONLY the default sensors present in most mobile phones: WiFi, B.T.(not sure if it might be useful) or GPS, how do I do it?

The tracking needs to be precise (say accurate to 0.5 meters).

Where do I start? Which sensors do I use? and is it possible for it to work without the beacons and the phones being in Line Of Sight?

Edit:

How about a hybrid between Qubulus' http://www.qubulus.com/what-we-do/our-technology/ and placing custom antennas? Instead of the conventional idea of placing multiple beacons throught the area of the same frequency, how about placing only 3 powerful antennas of different frequencies and repeating the "fingerprinting" process ourselves?

Also, what frequencies do the antennas in mobile devices allow us to monitor through an app? Are they hard-tuned to only 2.4/5 GHz bands or can they monitor everything? and do OS's like iOS actually allow us to monitor the signal strengths(without jailbreak)?

Sorry about so many doubts! I'm not a science student. No idea how these stuff work.


texts:
I am using an Atmega32-A microcontroller and an AD7798 external ADC. I am able to set the ADC registers and read back ADC values. I have written the following code:

  statusreg = AD7798_8(0x40, 0xFF);          // read STATUS register default value
  Id = AD7798_8(0x60, 0xFF);                 // read ID register  default value
  mode = AD7798_16(0x48, 0xFFFF);            // read MODE register default value
  conf = AD7798_16(0x50, 0xFFFF);            // read conf register default value

   AD7798_16(0x10, 0x0010);            // write Configuration reg = 0x0010.  2.5V range
   value = AD7798_16(0x50, 0xFFFF);         // read Configration register

   if (value != 0x0010)
   printf("unexpected conf setting %04x\r\n", value);

   while ((statusreg & 0x80) != 0);                         // wait till ADC is ready
   adc = AD7798_16(0x58, 0xFFFF);                           // read register
   printf("ADC value is %04d\r\n", adc);

From the above code, I am reading the ADC values. According to the AD7798 datasheet and according to my configuration register setup, I have to find out the analog input voltage using following formula:

  When the ADC is configured for bipolar operation, the output  code is
  offset binary, with a negative full-scale voltage resulting  in a code
  of 000...000, a zero differential input voltage resulting  in a code
  of 100...000, and a positive full-scale input voltage  resulting in a
  code of 111...111. The output code for any analog  input voltage can
  be represented as

  Code = 2N – 1 × [(AIN × GAIN / VREF) + 1]

  where:
  AIN is the analog input voltage.
  N = 16 for the AD7798, and N = 24 for the AD7799.

I am getting an ADC value of 1EF2(hex) for 0.6V analog input. I have measured using an oscilloscope. I have calculated the analog input voltage using the above formula and I am getting 0.15V. Here GAIN is 1, VREF = 2.5V. Which is wrong because I have to get 0.6V. I have converted resultant hex ADC value into decimal 7922 and also binary 0001111011110010. My analog input voltage is varying from 0V to 0.6V. According to my analog input voltage my ADC output is also changing from 0002 to 1EF2.

If I change the configuration register setup to any other setup like bipolar to unipolar (from 0x0010 to 0x1010), at that time I am getting an ADC value of 0000 always. It is giving an ADC value of 0000 for any configuration other than 0x0010 in the configuration register.

More over, I am not able to understand what the following sentence means:

  with a negative full-scale voltage resulting  in a code of 000...000,
  a zero differential input voltage resulting  in a code of 100...000,
  and a positive full-scale input voltage  resulting in a code of
  111...111.

How do I properly convert resultant digital signal to an analog voltage?
Are my ADC readings right or wrong?
Why does my code not work for any other configuration?


texts: Need safe power supplies for beginner class with indicator light

texts:
In an intro electronics class in high schools, we use 6v battery packs as a way of delivering safe power for experimenting.  However, the logistics of constantly getting fresh batteries, and our distaste for using so many batteries is leading to a search for an alternative.

We would like an inexpensive power supply that delivers small amounts of current (Ideally both 5V @ .2A, 12V @ .2A for example).  Building such a supply as a project would be possible for a class of the more advanced students.  So the question is to find a design.  However, it would have to be protected from short circuits, and ideally would indicate to the student (with an LED?) when they have made a mistake and short circuited.

I found one design for a DC circuit, though this one requires DC voltage in:

Obviously I could take the above design, add a transformer and full-wave rectifier, but that's both big and clunky as well as possibly not optimal.

In an earlier question, someone suggested a 5V wall wart.  student safe power supplyI can find inexpensive 5V wall warts, but would ideally like 12V as well, and have no idea if a given wall wart is short-circuit protected and even if they are, I want an indicator SHOWING when there is a short-circuit.  I would like to take one and build in short circuit protection with an LED or alarm showing when a short happens, as well as a power indicator showing when it is on.

Can anyone suggest a design that we can build or buy?  Since we are talking dozens of units per class, the cost has to be kept low.


texts: 18 VAC "OFF->ON" transition detection on multiple independent power sources

texts:
I am looking for a (simple) circuit to monitor between 1 and 16 independent 18 VAC power sources, all sharing a common ground.

While some might be OFF and some might be ON, the monitoring is about detecting the transition OFF->ON of any of those 18 VAC power sources.

When an OFF->ON detection occurs, I need to close ONE small single contact relay for ~8 seconds.

I do not need simultaneous detection capability; i.e. I do not need the detection to continue working during the ~8 seconds already triggered by one detected OFF->ON event. The monitoring just restarts after.

Your help will be really appreciated.

Daniel

Just for reference, here is one post that is related to my question, but not exactly covering my need:  AC detection for microcontroller


texts: XBee short wire antenna replacement to longer wire?

texts:
Is it possible to extend the 1mW wire antenna XBees from the short wire antenna, to a longer wire antenna? Will this harm the output stage of the XBee? The point being that I have an XBee in a metal box and I need to place the antenna outside the box. Due to the placement of the XBee, the wire antenna needs to be about 10cm.

Or alternatively, is it just a matter of replacing the wire antenna on the XBEE with a U.FL connector. Is that the identical connector used on XBees?


texts: A question about max TTL input of a converter device

texts:
I have a programmable f/I converter which can be modified for various types of inputs and outputs. They have also a more detailed manual. I read them and learned how to configure and set this device. As an output I set it to 0-10V and as input I set it for frequency with TTL type input. This is because for NPN and PNP inputs I need to add some transistor circuitry with certain voltage ect. Input to the converter will come from a circuit which is currently outputting 0-8.2V pulse train(8.2V is because of a zener limiting the amplitude)

Anyway the bottom line is I will use this converter to convert incoming pulse train from a circuit to analog voltage. And my inputs to the converter is 0-8.2V pulse train(input to pins 5 and 6 in the datasheet). I made the setup and works fine. The converter successfully converts 0-8.2V pulse train frequency to a voltage range set. I set the converter to TTL input as I mentioned.

My concern is coming from lack of knowledge here. So the input to the converter is a pulse train with 8.2V amplitude, on the other hand the converter is set to TTL input settings. But my input to the converter is 0-8.2V not 0-5V.

Is it alright to use this like that? I mean would exceeding 5V and using 8.2V amplitude pulse train cause damage in long run? I know that TTL stands for 0-5V signals. Should I reduce my input pulse amplitude to exactly 5V? I couldn't extract this from the manual from the max ratings.


texts: What is the best TVS/ESD protection for Wheatstone bridge circuit?

texts:
I have 150K ohm on three legs of Wheatstone bridge, one leg on human body (skin), bridge excitation voltage is 5V, differential amplifier is be used to read the differential voltage of the Wheatstone bridge,
I need to protect my circuit from ESD/TVS and any over voltage,
protect- Differential input of IA
protect- 5V power line for excitation of bridge
Max over voltage source 150V @ 10Hz-200Hz, max source current 50mA
IA - INA114
rail to rail 5V and GND
can I use Zener diode with required wattage?
can I use 5V TVS for 5V supply line?
can I use Zeners for differential inputs?
can I use 5v 2x TVS for differential inputs?
which is best Zener or tvs?


texts:
I'm trying implement a fairy basic filter, and right now I have just some simple test code for me to enter in values. It errors out on the line when it gets to where I call the function I have written. I am fairly certain my error is coming from how I am using the pointers but I just don't understand pointers well enough to know what I'm doing wrong. Any thoughts on what I am doing wrong?

If it helps to understand what the filter should be doing: when a new value is input it is added to the to the buffer and the old state of what the average of the buffer was at is subtracted from the the buffer. the new average of the buffer is returned.

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int a,b,a_buffer,b_buffer,valueToPrinta,valueToPrintb;
    printf("a value: ");
    scanf("%d",&a);
    printf("b value: ");
    scanf("%d",&b);

    valueToPrinta = integrate_filter_data_16bit(a, a_buffer, 2);
    valueToPrintb = integrate_filter_data_16bit(b, b_buffer, 2);

    printf("%d and %d", a_buffer,b_buffer);

    return 0;
}

int integrate_filter_data_16bit(int integrator_buffer_16bit, volatile int *pintegrator_accumulator16bit, int integrator_size_16bit)
{
  int temp_integrator_accumulator_16bit = *pintegrator_accumulator16bit;

  /* compute the new value of the IIR filter accumulator */
  *pintegrator_accumulator16bit = (int)integrator_buffer_16bit + (temp_integrator_accumulator_16bit - (temp_integrator_accumulator_16bit >> integrator_size_16bit));

  return((int)(*pintegrator_accumulator16bit >> integrator_size_16bit));
}


texts: Detection of CT secondary subsidence current

texts:
In utility power system protection we have a protection function called "breaker failure" protection. This protection is used to take appropriate action if/when a circuit breaker fails to open after a protective relay commanded it to.
One of the methods used to determine if the breaker is still closed is a simple fault detector that monitors currents from  current transformers (CTs) on the breaker. In some cases we need really fast breaker failure to support system stability. We not only may need this breaker failure to operate fast, but we also need it to be secure against incorrect operation.  If it takes it a long time to recognize that the primary current is gone then it is subject to incorrect operation.
In CTs, after the high primary fault current has gone, it is typical to have a "subsidence current" flowing in the CT secondary (L-R circuit) as shown below (taken from here):

After the primary current is gone, we need the current detector in the breaker failure relay to reset (to avoid accidentally timing out and tripping).
This subsidence current is a simple decaying L-R transient. There are digital relays now that can detect that the primary fault current is gone in under 1-1.5 cycles (16-25ms) now by recognizing that the secondary current is now only subsidence and not AC driven. But, there is an older analog relay, the Basler BE1-50BF, that boasts a current detector reset time of 1ms.
My question to the analog electronics experts is this: What analog circuit or approach could/would you take to detect that the CT secondary current being measured is no longer AC, but is just subsidence current?
This paper describes some of the challenges that one digital relay manufacturer faced.  But, I'm curious about an analog design like I mention above.  I have never seen a digital relay get close to that 1ms time.  I'm not building anything, I'm just curious.
EDIT: The subsidence looks like below (snipped from above reference). It is a simple L-R transient.


texts: Error (10536): VHDL Loop Statement error at InstructionMemory.vhd(31): loop must terminate within 10,000 iterations

texts:
Can someone help me solve this problem?

Its my code below:

library ieee;
library std;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use std.textio.all;

--
entity InstructionMemory is
    port (
        clk, rst : in std_logic;
        address : in std_logic_vector(31 downto 0);
        instr_out : out std_logic_vector(31 downto 0)
    );
end entity;
architecture aim of InstructionMemory is

    type instr_mem is array(0 to 20) of std_logic_vector(31 downto 0);
    signal imem : instr_mem := (others => (others => '0'));

begin
    process (clk)
        file file_pointer : text;
        variable line_content : string (1 to 32);
        variable line_num : line;
        variable i : integer := 0;
        variable j : integer := 0;
        variable char : character := '0';
    begin

        file_open(file_pointer, "C:/Users/MM/Desktop/PF3/MIPS-Monocycle-32-bits-master/Testcases/instructions.txt", READ_MODE);
        while not endfile (file_pointer) loop -- this is line 31
            readline(file_pointer, line_num);
            READ(line_num, line_content);

            for j in 1 to 32 loop
                char := line_content(j);
                if (char = '0') then
                    imem(i)(32 - j) <= '0';
                else
                    imem(i)(32 - j) <= '1';
                end if;
            end loop;
            i := i + 1;
        end loop;
        file_close(file_pointer); -- Close the file
        wait;
    end process;

    process (clk, rst)
    begin
        if rst = '1' then
            instr_out <= "00000000000000000000000000000000";
        elsif clk'EVENT and clk = '0' then

                assert (( (to_integer(unsigned(address)) mod 4194304)/4) < instr_mem'LENGTH)
                report  "Simulation has ended"
                severity ERROR;
            instr_out <= imem((to_integer(unsigned(address)) mod 4194304)/4);
        end if;
    end process;
end architecture;

this is line that apear the erro

    while not endfile (file_pointer) loop -- this is line 31

this is the size of intructions, 22 lines.

00000000111100000000100010010011

00000001010000000000100100010011

00000000101000000000100110010011

00000000010100000000101000010011

00000000001000000000101010010011

00010000000000000000111010010111

11111110110011101000111010010011

00000000000010101010111000110011

00000010000011100001110001100011

00000000010010101010111000010011

00000010000011100000100001100011

00000000001011100001001100010011

00000001110100110000001100110011

00000000000000110010001010000011

00000000000000101000000001100111

00000001010010011000010000110011

00000001100000000000000001101111

00000001001001001000010000110011

00000001000000000000000001101111

01000001001001001000010000110011

00000000100000000000000001101111

01000001010010011000010000110011


texts: 555 timer delay circuit: resume after supply outage

texts:
I have created a 555 delay circuit where output goes down after a delay of T minutes.

The 555 IC is in astable mode and is triggered automatically upon turning on the supply, Vcc.

After turning on the supply, when the output is still on (within T seconds) I turn off the supply for some time, after the supply resumes the timer output should be high for only remaining time.

In other words the circuit should remember the time it has elapsed before power outage.

Eg: Suppose T = 5 minutes . Ideally when the circuit is run without any interruption; the output goes down after 5 minutes. In case I turn off the supply after 2 minutes, and later turn supply on; the timer should only have a delay of 3 minutes

What is the simplest and cheapest way to achieve this?


texts: Connecting Garmin 18x 5hz GPS to PC via Serial TTL-232 USB cable

texts:
I want to connect Garmin 18x 5hz GPS (this) to computer via FTDI Serial TTL-232 USB Cable (this). But once I try to update the GPS via Garmin updater, I get framing error. "A communications error has occured. The hardware detected a framing error. Please ensure that the GARMIN device's Interface option is set to GARMIN or Host mode and try again."

This happens after I have chosen COM port and baud rate and click "OK" in the updater. I am not sure which baud rate I should use but Garming gives me 5 options in the updater (9600, 19200, 38400, 57600, 115200) and none of them work.

I have connected every wire individually, both GPS grounding wires into adapters grounding wire (blacks together), GPS' TXD into adapters RXD (white to yellow), GPS' RXD (RCV) into adapters TXD (green to orange) and red power cables together. Now after updating the adapters drivers and connecting the cable the adapters starts to flash green light (but not red). When I run the GPS updater the green light starts to flash for few seconds and then shuts off and error message pops up.

Is my wiring the problem (I just pushed the wires inside the other end of the adapter) or is the problem software side? Any suggestions or tips how I can connect the 18x 5hz through USB port?

EDIT:---------------------------------------------------------------------------

Thank you Andrew!

Now I need new adapter or MAX232 (or similar). Problem is the Garmin 18x 5hz only has cables on the other end that I can't connect to typical adapter. I have one serial port (RS232) to USB adapter lying around somwhere. I try to hook it up somehow into the Garmin and post results. I lack any soldering equipment or experience really...

EDIT2:--------------------------------------------------------------------------

I tried out the FT Prog and inverted the RXD and TXD signals but I still get the same problems as before. I also tried to invert every signal. After that did not work out either I dug up an old USB to RS-232 converter, but as I predicted, I really have no way to connect the Garmin GPS and typical RS-232 male port.

So either the problem lies in the GPS it self or the connections, because inverting the signals did not work. Thank you for the help!


texts: Biasing a emitter follower darlington configuration

texts:
Below picture is a simple voltage regulator(link to simulator):

The current at the op amps output is at nA region(why?), how can I increase the current at the op amps output without adding a third transistor with high gain?


texts:
I'm having a hard time getting my head around finding the transfer function.

I have a circuit that looks like this:

 o----------R-------C-----------o
                         |
                         |
                         C
                         |
                         |
 o------------------------------o

The solutions in my book say the answer is $$\frac{(RC)^{-1}}{s + 2(RC)^{-1}}$$ where s = jω. How did they get this?

Help will be much appreciated.


texts:
I am now confused by one piece of Verilog Codee, its kind of testing the blocking or non-blocking assignment features that combination with Delay model.

 module cl_tb;

  reg x,y,z;

initial begin
    x = 2;
    #4;
    y <= #9 x;
    x = 1;
    #50 $stop;
end

initial begin
  $monitor("%0t,%d,%d,%d",$time,x,y,z);
end

always @(x,y)
begin
   z = # 2 x+y;
end

endmodule

By hand-calculation, I could get the result
[ Time: X value, Y value, Z value] below:
[0: 2,x,x]
[2: 2,0,2]
[4: 1,0,2]
[6: 1,0,1]
[13: 1,2,1]
[15: 1,2,3]

However, the simulation result is
[0,0,x,x];
[4,1,x,x];
[13,1,0,x];
[15,1,0,1];

Which you can see from the link http://www.edaplayground.com/x/Was

I am wondering why the always@(x,y) was not triggered  at timeslot 2 and 4.

Best


texts:
I'm starting to learn about the state-space representation and i'm facing some difficulties. Suppose we have a system with connected blocks, like the one below:

where

Sometimes we want to choose variables that have physical meaning as the state equations. Suppose that these physical variables are the output of the second order block, the derivative of this output and also the output of the first order block. But by writing the time-domain equation of the transfer function of the second order block, we see that a derivative of the input will appear. Since we cant have an input derivative in a state equation, it makes me believe that I cant choose those variables, since:

If we took this block as an entire system, we couldn't do much more. But in an interconnected system, like the one above, is there a way i can relate the state equations of the other blocks so i can represent the second order block with those variables? For instance, we see that the derivative of the second order block input is equal to the derivative of the output of the first order one, since they differ by a constant, and also the output of the second order one is related with the input of the first order block. So is there a way i can represent the second block with those variables considering the interconnection?

Thank you.


texts: IGBT's Ic (peak current): why always 2 times of Ic

texts:
I would like to know:

1) Why, almost on every IGBT datasheet that \$I_{cm}\$ (maximum peak current) is 2 times \$I_c\$? - for example see datasheet

How, can I measure this \$I_{cm}\$, to verify that it is really 2 times \$I_c\$? Or is there maybe some regulation that on a datasheet that \$I_{cm}=2*I_c\$ ?

2) Energy losses: I see on the oscilloscope, that there is a tail  current after switching. To calculate Eoff, for example how much time do I have to consider the tail current? Some company determine toff for 1us. Why? Some rule specified that time of tail current for Eloss evaluation must be 1us? Or everyone could choose the time that they want?


texts: Using Mic from 10 feet away for voice recognition

texts:
I'm trying to use a mic from 10 feet away.

Background: for my senior project I would like to talk to a computer to run scripts, but I want to talk to the mic throughout the house.  So I need to be able to speak from about 10 feet away to a mic in the ceiling, and have it go to the computer, where the computer will execute the scripts based on the voice commands.

Due to my inexperience with op amps and audio signal design, what would be a good way of amplifying the signal, and what would be a good way of filtering the signal?

The Quality is important, because the voice recognition will work better with better quality mics, and I might be talking over the phone with the mic.  Budget is also important. because i have to build 4 to 5 of them.

Any Suggestions also for how to approach the problem are also welcome.
Thanks


texts: Why use asymmetrical capacitor values for crystal?

texts:
Are there any circumstances where you would want asymetrical load capacitors on a crystal? I came across this schematic in the documentation for an NXP UART. It looks just wrong to me. Can anyone tell if this is a typo, or if there is a reason behind it?

NXP Uart Documentation (see Fig 11 on page 18).

Here's the schematic at issue:


texts:
I am doing a project that requires that I implement a cruise control system on an RC car using a GPS for feedback.

I have implemented PID controllers before, but this is a little bit new to me because instead of generating a correction delta like -8 or +6, the controller has to output a value from 0 to 100, 100 being as fast as the car can go, and 0 being a dead stop.

At first, I attempted to use a solution where I kept a running tally off the current throttle and I simply added the mv from the PID controller to it. This became a big issue because the "currentThrottle" variable essentially became a second integrator and would frequently windup when the car didn't respond fast enough.

One limitation of this project is that I cannot modify the algorithm used for generating the PID correction delta, but I can do whatever I want with the setpoint and mv before/after the PID correction is generated like so:

(int)cruiseControl.CalculateCorrection(8, rmc.Speed);

Where 8 is the setpoint (8kts) and rmc.Speed is the current speed. This will return the correction delta calculated from the PidConfig variables (Kp, Ki, Kd, integrator windup control, etc) when I constructed the PidController object.

Any ideas?


texts:
I am trying to program an MSP430FR5969 for the first time. I successfully executed and modified a program to blink one of the LEDs connected to P1.0. The relevant predefined variable is P1OUT.

The other LED is connected to P4.6 but I do not know which variable corresponds to it. P4OUT doesn't seem to work, and I am not sure it is the right one because there are several pins: P4.4, P4.5, P4.6 and the variable P4OUT doesn't seem to differentiate between them.

What is the variable naming scheme? More importantly, what reference document would answer similar questions?


texts: Why don't infinitely many sinusoidals exist in an oscillator circuit?

texts:
A sinusoidal oscillator, takes the ambient thermal noise or any imbalance in the circuit as input and gives out an oscillation.

This kind of oscillators are called to be linear. By the nature of a linear system, if it gives out \$Y_1\$ when the input is \$X_1\$ and gives out \$Y_2\$ when the input is \$X_2\$, it must give out \$Y_1+Y_2\$ when its input is \$X_1+X_2\$.

The thermal noise which starts the oscillations is always present in the system, which means that there are literally infinitely many inputs. Why doesn't it start another oscillation in the system? Why don't other sinusoidal with the same frequency but random phases come out and take place in the system? What physical mechanism prevents existence of a second oscillation and makes the first one dominant?


texts: Derivation of diode voltage in three phase full wave diode rectifier

texts:
Considering ideal diode in 3 phase full wave diode rectifier we can present the system in picture below.

I found the final equation for \$v_{D6}\$, but can not figure it out how it was derived.
\$v_{D6} = u_{st} + \frac{L_i}{2L_i+L_0} (u_{rs}-v_0)\$

Can someone please help me with derivation of this equation(s).


texts: Converting power and speed of a bike axle

texts:
We want to convert the speed and power applied on the pedals of a bike to convert it to an digital signal. But we need to apply an variable load to simulate cycling up-/downhill.

My initial thought was to use an DC motor as generator to convert speed to an voltage we can read (with a power resistor to dissipate the power produced) and a second DC motor that would rotate counter clockwise to represent an load.
But as I cannot test my theory I'm not sure if the second motor would just burn up as motors aren't supposed to be used like that. (I am well aware of the current peak the motor could use when trying to spin while halted.)
Another option for the load would be using a pneumatic/electronic brake. But then we wouldn't be able to measure the power/torque.

I did find an similar question, but the situation isn't completely similar. As we plan on using the motor to continuously turn counter clockwise.

A simple nod in the right direction would suffice.


texts:
If the minimum load of a sensor(page 7) is 65k Ohm, what does that mean?
Does it mean that the sensor needs at least a 65k Ohm resistor, so a 100K Ohm is good?
Or does it mean the sensor needs at least a certain amount of current drawn off through the resistor, so a 10K Ohm resistor is good?


texts: What happens with voltage phase on the resistor and capacitor in AC circuit?

texts:
I'm currently studying AC circuits and I find it difficult to understand phase differences between voltage and current on different components. For example, let's look at this circuit:

And here is the time domain simulation in PSpice:

source - green, resistor - blue, capacitor - red

Why does resistor voltage preceeds source voltage, shouldn't they be in phase? If voltage on the capacitor lags current by \$\pi/2\$, it also lags voltage on the resistor by \$\pi/2\$, since resistor voltage and current are in phase. What am I missing? Thank you for you time.


texts: Is there a RF signal device for a 120 or 240 vac wire to start and stop a standby generator?

texts:
Our standby generators automatically start when a switch in the automatic transfer switch closes and the gen stops when that switch opens. Usually we bury 2 16ga wires along with two 120/240v hot and ground wires from the ATS to the generator that are used only when the generator runs during a power outage.  But often the 120/240v and ground wire are already buried for a previous non-automatic tractor PTO generator.  So now we need to trench and bury another two 16ga wires often several hundred feet in length.
   Is there or could a 12 vdc transmitter device be designed that could send a radio signal down any of the three #4 to #000ga generator supply wires that would trigger a receiver and switch to start the generator and when the main line power was restored would open the same switch to stop the generator when the ATS micro switch opens?


texts: How to connect 7447 decoder to 7-segment display?

texts:
I've connected a 7447 decoder to 7-segment display as shown in figure. When I connect an input, the LEDs doesn't form numbers but they light up randomly.

I just want to know the right way to connect the output pins of 7447 to the pins of 7-segment display?


texts: Replace filtering(?) capacitor on CRT deflection Board

texts:
I am doing partial recap on CRT monitor Sony PVM 20m2e. (monitor was working, but RGB lines at the top of screen which should be hidden were visible and geometry is not top notch)

I desoldered C584 from deflection board, sadly it's broken (0.15K ESR, 21% Vloss, but capacitance is OK). And my parts supplier did not send the part which I ordered. Now I don't have working 2.2uF 160V electrolytic capacitor at hand, but I have working 4.7uF 250V electrolytic at hand, would it cause problems?


texts:
I'm an undergraduate electrical engineer and my universities notes are not the best, I have an assignment in which I do not want the answers to but the question has given me the oxide capacitance, electron mobility, hole mobility, min feature size, max alignment error, Vt for both the Nmos and Pmos, VDD. I have to design a two input NOR Cmos layout.

However I haven't been given W to solve the aspect ratio. I do not know how to find W with these variables. All notes I have looked at W is usually given.


texts: PIC32 does not have Memory Managment Unit, why would a high end microcontroller not have such a peripheral

texts:
MMU is needed to run Linux and perhaps for other tasks related to OS. However, the PIC32 does not have one of these. Why would someone make a high end microcontroller and not include a MMU?

It may make sense for lower level PICs like PIC18F, PIC24 to not have MMU, but why did Microchip not put in an MMU into the PIC32 which is their high end processor?


texts: Step down voltage regulator uncertainties

texts:
The step down voltage regulator I'm currently looking at is the 5V, 5A Step-Down Voltage Regulator D24V50F5 from Pololo ( https://www.pololu.com/product/2851 )

In the description it mentions an EN (standing for enable) pin that can be used to power down or power up the regulator. This sounds like a neat functing I can certainly find use for, however, I'm not sure on the explanation on using it:

    The regulator is enabled by default: a 100 kΩ pull-up resistor on the board connects the ENABLE pin to reverse-protected VIN. The ENABLE pin can be driven low (under 0.6 V) to put the board into a low-power state. The quiescent current draw in this sleep mode is dominated by the current in the pull-up resistor from ENABLE to VIN and by the reverse-voltage protection circuit, which will draw between 10 µA and 20 µA per volt on VIN when ENABLE is held low.

If I understand this correctly, if i connect the EN pin with GND it will disable to regulator and thus cut the VOUT?

Thanks for your suggestions!


texts:
I've designed an active bandpass filter based on the one described in this article http://www.bu.edu/eng/courses/ek307/documents/ActiveFilterNotes.pdf (section 13.3.4). However, I want to use a single ended supply, and I want use  a non-inverting configuration. I've designed a circuit (below) and run some spice simulations, and everything is working fine.

But then I noticed that R3 is connected to the negative rail (GND) not my virtual ground (Vcc/2).  My instinct tells me that R3 should terminate at Vcc/2 but after some experimentation I found that it doesn't matter where it goes - ground, Vcc, Vcc/2, 10 megavolts - no difference.

How can that be? Can someone explain exactly what's going on here? Am I correct that R3 should terminate at Vcc/2?

simulate this circuit – Schematic created using CircuitLab


texts: The influence of capacitors and resistance in a BJT circuit

texts:
I solved the circuit and found these values for each one.
But I wanted to know:

Which capacitor has more influence in the low frequency and in the amplification?

Does RE have impact in amplification?


texts: Can I find run time of a refrigerator given the Watt Hours?

texts:
I took the following measurements on my mini fridge with a power meter.

Voltage: 123 V
Current: 0.71 A
Power: 50 W

I ran for 4.75 hours and the meter read 52 Watts used. So I know that the watt hour rating is about 11Wh per hour (54W/4.75Hr).

Can I then conclude, since the wattage during on-cycle is 50 watts (and thus if ran for a complete hour would be 50 watt hours), that run time per hour would be 11Wh/50W = 22% of 50Wh

Then: 22% of an hour would be 13.2 minutes of actual run time.

The math seems to make sense to me but I can't find any examples on the internet.


texts:
I want to make a square wave inverter for DC resonant converter. I have constructed this full-wave bridge inverter which is to work at frequencies of 50kHz to 100Khz.

The input is 37V DC. The gate signal in of 5v and at a frequency of 50kHz. The problem is that the output is not coming. Only a square wave signal of 1.4V is generated with the same gate signal frequency.

I think that the MOSFETs need a gate driver but don't know how to design one for this circuit or some kind of bootstrapping circuit. I have to run this with an Arduino UNO. kindly need suggestions on what to do.


texts: how to make a hole in the solder like here?


texts: PLDs, DSPs, MCUs, MPUs and SoCs Typical Application

texts: PLDs, DSPs, MCUs, MPUs and SoCs are all embedded devices, they can be programmed / configured to achieve a specific application. I've worked with MCUs and FPGAs in the past and realized that they are very different when it comes to their hardware architecture and programming / description language. In some applications, both MCUs and FPGAs could achieve the same goal but most of the time it isn't the case. I've heard that PLDs aren't optimized for mathematical operations but that DSPs are. I was wondering what each of these embedded devices can do that the others can't (what kind of application are they intended for).


texts: Removing stencil mask from chip for BGA reballing

texts:
I am in the process of reballing my ps3 system. This is my very first time so i am watching tutorials online.

My question is how do i remove the stencil mask from the chip without moving the balls?

If you take a look at this video youtube_vid at 6:20, it shows the guy pouring balls into the stencil mask, but the next frames show the chip without the stencil mask and the balls are still on it. So how did he remove the stencil mask without moving the balls?

I also have a station where you put your chip and it says there, then a big stencil mask gets screwed, but i have very little stencil masks and i cannot screw them. So i have to do like this guy is doing


texts:
I am trying to learn more about what I believe is called 'flex copper' ribbon cable.  This is the cable that you often see connecting CD drives to main boards in laptops etc. where the cable 'curls' back when the drive moves.  Similar to FCP and or FFC but made of a flat copper like material.

Is this called 'flex copper'?  Does anyone have resources for custom manufacture?


texts: Linear regulator after switching regulator

texts:
I need to power a board that works at 3.3V, and I have a regulated power of 12V.

I tried to use a single linear regulator like the TS2940 but the power required is so high that the heat produced was too high (melted the case).

So I decided to use a switching regulator (the LM2594) to go down to 5V and a LDO linear regulator to go down to 3.3V. I read everywhere that this is a common practice.

The switching regulator works fine but my problem is that the linear regulator does not work properly (2.8 Vmean, 1.2 Vpp).
That is because by datashet the output capacitance of a switching regulatr should be around 100uF, and the input capacitance of a linear regulator should not be greater than 10uF.

What is the best way to adapt those two impedences??

Thanks


texts: Design a two-stage LC low-pass filter with one fixed stage

texts:
I need to design a two-stage LC low-pass filter just as the picture below. The values of L and C in the second stage(L6 and C4) are fixed. I can only change L8 and C5. The required cutoff frequency is around 2MHz. The Q factor is not so matter.

So my question is: is there any special point I need to pay attention to when designing L8 and C5.
(I know that for the RC filter, the resistance of the second stage needs to be much larger than that of the first stage. But I don`t know whether it would be the case for LC filter. Or any similar rules)

Update: the source impedance is about 50ohm. And the load is about 30ohm. Of course at the end some resistors would be added into the circuit, but at this moment, I think I can just ignore them.


texts: A question about power transformer power rating on a diagram

texts:
As a part of the one-line diagram, a power transformer is shown as below:

Here what I understand is that 400/132kV means 400V is the primary nominal voltage and 132kV is the secondary nominal voltage.
And MVA is the nominal apparent power. But what does 140/155MVA mean in this context? Are they minimum and maximum power? Why there are two numbers with a slash?


texts:
CSMA/CD 's definition based on wikipedia is :

  Carrier Sense Multiple Access With Collision Detection (CSMA/CD) is a media access control method used most notably in local area networking using early Ethernet technology. It uses a carrier sensing scheme in which a transmitting data station detects other signals while transmitting a frame, and stops transmitting that frame, transmits a jam signal, and then waits for a random time interval before trying to resend the frame.

I know about this algorithm. But what I am looking for is which devices on computer networking field use this algorithm to access the medium?
Is switch use CSMA/CD algorithm to deal with collision on wired media ?


texts: Is it possible to create a stepping power supply switched with transistors?

texts:
I am relatively novice with wiring and circuits. I am attempting to power a fan and use transistors to increase the power supply to the fan as I close each transistor!
The base transistor and battery will pass 3 volts to the fan, then when the next transistor is closed (is this the correct term for sending voltage through the transistor when "activating?" the base?), the thought would be it would some how put the battery into series with the other one to provide the fan with 9 volts. I have wired this up at home a few different ways and to no avail.

I will provide further sketch information if requested.

EDIT - I have finally gotten around drawing up the sketch. I am hoping I sketched it correctly. The thought is I use an Arduino to close a transistor, and with the transistor closed current will then flow and power the motor. If it is the right most transistor the thought is it would only be powered by the single, right most power source (each power source is 3 volts). Then if I were to close the first (right most) transistor, and second (middle) transistors it would then supply 6 volts with the two power sources in series to the motor. Then the thought is with the third (left most) transistor closed, and the other two transistors to the right also closed, that the batteries will work in series to provide 9 volts to the motor.

Does this make sense?


texts: What is the proper method to become able to connect conduit signals inside Qsys?

texts: Qsys (now known as Platform designer) identifies Avalon MM, Avalon ST, Clock, Reset and some other type of interfaces and makes it trivial to be able to connect them between different blocks. However, although I have read that conduits are not supported intrinsically by Qsys, it is possible to be able to connect conduits together between different modules within Qsys. My question is, if two modules have conduit signals, some of which need to be connected together, how do we do it properly? The basic idea is that the required conduit signals themself are connected between different modules within Qsys and do not have to be exported and then connected outside in an RTL block.


texts: Loop gain calculation for the buck converter

texts:
The figure below is small signal model for buck converter from Switch-Mode Power Supplies Spice Simulations and Practical Designs by Christophe Basso.

Could anyone explain why the loop gain is 12000 here? It seems that the author doesn't include the D*Vin part.

  A 60 dB gain error amplifier monitors the output with a simple
  feedback capacitor \$C_f\$, making it an integrating compensator together
  with \$R_{upper}\$. In open-loop, the output impedance, as expected, is the
  inductor series resistance of 100 mΩ or –20 dBΩ.  Closing the loop with
  a total gain of 12,000 (1000 x 12) leads to a new closed-loop output
  impedance of Eq. (1-14)

    $$R_{s, CL} = \frac{R_{s, CL}}{1+T} = \frac{100m}{12001} =
  101.6 \: dB\Omega \:\:\:\:\:\:\:\:(1-14)$$

For anyone wondering about the model, this article page 5/49 explains the model in detail.


texts: Shutdown mode on stm32 consuming a lot of power

texts:
I am testing the demo code given in the directory STM32Cube\Repository\STM32Cube_FW_L4_V1.14.0\Projects\NUCLEO-L476RG\Examples\PWR for CubeMX. I am testing the code PWR_ModesSelection and am recording the current values across J6 IDD which I'll be writing down below.

For SHUTDOWN, I'm getting a reading of 3.84 mA.

For RUN Range 1, 80MHz with FLASH ART on, I'm getting 14.08 mA.

According to the document,  an4621, power consumption without RTC in shutdown mode should be 0.33uA. Why am I seeing such a high current value? Is there a drain due to the components on the board? I'm using STM32L476RG Nucleo board and have no peripherals attached.

void test_shutdown(void)
{
  printf("\n\r Executing test (SHUTDOWN) \n\r");
  printf(" Please measure current then use Reset button to select another test \n\r");

  /* Set all GPIO in analog state to reduce power consumption */
  GPIO_AnalogState_Config();

  /* Enable Power Clock */
  __HAL_RCC_PWR_CLK_ENABLE();

  /* Enter the SHUTDOWN mode */
  HAL_PWREx_EnterSHUTDOWNMode();

}

void GPIO_AnalogState_Config(void)
{
  GPIO_InitTypeDef GPIO_InitStruct;

  /* Set all GPIO in analog state to reduce power consumption, */

    __HAL_RCC_GPIOA_CLK_ENABLE();
    __HAL_RCC_GPIOB_CLK_ENABLE();
    __HAL_RCC_GPIOC_CLK_ENABLE();
    __HAL_RCC_GPIOD_CLK_ENABLE();
    __HAL_RCC_GPIOE_CLK_ENABLE();
    __HAL_RCC_GPIOF_CLK_ENABLE();
    __HAL_RCC_GPIOG_CLK_ENABLE();
    __HAL_RCC_GPIOH_CLK_ENABLE();

    GPIO_InitStruct.Mode = GPIO_MODE_ANALOG;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Pin = GPIO_PIN_All;

    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
    HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
    HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
    HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);
    HAL_GPIO_Init(GPIOE, &GPIO_InitStruct);
    HAL_GPIO_Init(GPIOF, &GPIO_InitStruct);
    HAL_GPIO_Init(GPIOG, &GPIO_InitStruct);
    HAL_GPIO_Init(GPIOH, &GPIO_InitStruct);

    __HAL_RCC_GPIOA_CLK_DISABLE();
    __HAL_RCC_GPIOB_CLK_DISABLE();
    __HAL_RCC_GPIOC_CLK_DISABLE();
    __HAL_RCC_GPIOD_CLK_DISABLE();
    __HAL_RCC_GPIOE_CLK_DISABLE();
    __HAL_RCC_GPIOF_CLK_DISABLE();
    __HAL_RCC_GPIOG_CLK_DISABLE();
    __HAL_RCC_GPIOH_CLK_DISABLE();

}

Above is the code that turns on the Shutdown mode for the given example. It's being called when a certain condition is being met in the main function.


texts:
Wasn't sure how to headline this but here it is:

I'm debugging one of my coin cell ON/OFF switch. Circuit is as follows:

simulate this circuit – Schematic created using CircuitLab

Basically a high side switch for the coin cell that would power a uC.

I've tested the MOSFET named in the schematic and also FDY4000CZ - both have same issue:

Issue is, that I am seeing some premature logic level on "uC GPIO", which

1) when applying power causes Vcoin to be slightly attached.

2) When removing power, the MOSFET does some 'jumps'. In frequent cases, keeps oscillating on/off - very dangerous for the coin cell which it can be depleted.

So here I just remove all power (3.3V and Vcoin) after some runtime. uC GPIO is high.
uC Vcc is slowly decreasing due to capacitance and uC is in sleep mode.
At one point ~1.6V the MOSFET switch closes and cuts power - All is good.
But then uC GPIO does some wierd jump - this should not happen! One of my good units does not do that, same mosfet, same circuit...

CH1: yellow, uC GPIO

Nothing else attached for this measurement.

Here I am manually dropping Vcoin (from PSU) voltage until cutoff, but I can now see some oscillation - as if the uC tries to power itself from Vcoin, but cannot, as uC GPIO self-charges High and then goes Low again. - Nothing like this is programmed via FW.

(NB: uc GPIO does NOT go High in startup, so it doesn't seem to be startup FW issue. So there must be some leakage?)

CH1: yellow, uC GPIO
CH2: magneta, Gate of M2
CH3: purple, uC Vcc
(ignore CH4)

Closeup of the small peaks:

All channels same as before.
CH1: yellow, uC GPIO
CH2: magneta, Gate of M2
CH3: purple, uC Vcc
CH4: blue, is now Current from Vcoin.

I'm all out of ideas, why this happens, or how leakage can turn uC GPIO high for a moment...

(The pull-resistors could be too high aka weak, but I cannot go much lower (I've seen 500k kind of solve this oscillation issue) because I need to keep current consumption for this circuit very low. These 10M resistors allow me to draw ~5uA average in total - which would be ideal.)


texts: How can I roughly estimate the load in this case?

texts:
A DC device operates with three industrial AA batteries meaning 1.5V times three = 4.5V. Besides that I only know that the approximate operating time is is 4 hours.

Is that possible to estimate the load in terms of resistance roughly?

Battery info: Three AA Type 1.5V 1500 mAH in series making 4.5V in total.


texts: Connecting a blind cable to electrical system

texts:
I am trying to connect a blind cable, (cable that doesn't have any end point connected to the grid), to the grid. This is how electrical wiring looks like. X's are lamps. and black lines in the first image are literally just a standard cable with live, neutral and ground(I omitted ground from the images).

Schematically it looks like this:
I tried connecting the left light(left X) to the grid, like this:

Apparently this is not how you do it, because the voltage at left X is just 100V and it should be 230V. What would be the correct wiring? The cables are already in place, so it is difficult for me to lay down a new one.


texts:
I am currently trying to write code for a 48 channel DMX controlled dimmer using a PIC24FJ32GA002. Using a scope I have confirmed that there is a DMX signal reaching the Rx pin of the UART which has been configured correctly using the PPS function of the pic. Also nested interrupts are disabled.

Below is the contents of my ISR for the UART Rx interrupt. What happens when I debug it with a breakpoint set inside the ISR is that the ISR triggers once or twice with null data reaching U1RXREG, it then fails to trigger again and the program runs with no further interrupts.

The main loop for the program has a loop that processes the incoming DMX packets and outputs to the PWM controller. dmxRecieveByte() takes the contents of rxbyte and places it into a buffer that's the right size to store a DMX packet (512 bytes) to then be copied to a separate buffer when the packet is received.

UPDATE: I have changed the ISRs so that there are seperate handlers for errors and incoming bytes, the uartRecieve() function now handles sorting the incoming bytes and the ISRs take care of clearing flags and such. The Tx ISR is there as a placeholder untill I get the DMX functionality working correctly.

UPDATE 2: Added the UART init code and the updated Rx ISR code, still getting the ISR firing once at the programs first run then not happening again. I've got the production hardware now so any variables that were in that have been removed. Poked around with a scope probe and everything seems to be in order signal wise.

UART Init function

void dmxInit(void)
{

    DMX_UART_MODE    = 0b0000000000001001;
    DMX_UART_BAUD    = (FCY/(4*250000))-1;
    DMX_INT_PRIORITY = 0x07;

    PORTBbits.DMX_RX_MUX = 0;

    spareBufValid = 0;

    DMX_UART_ENABLE_BIT = 1;
    DMX_INT_ENABLE_BIT  = 1;
}

UART Rx ISR

void __attribute__ ((interrupt,no_auto_psv)) DMX_INTERRUPT_FUNC(void)
{
    uint8_t dmxData;

    if(DMX_OVERRUN_BIT)
    {   // Overrun error
        DMX_OVERRUN_BIT = 0;
        dmxReset();
    }
    else
    {   // empty any data in the UART fifo
        while(DMX_DATA_AVAIL_BIT)
        {
            if(DMX_FRAME_ERR_BIT)
            {   // frame error
                if(DMX_DATA_REG)
                {   // data is not 0 - not a break
                    dmxReset();
                }
                else
                {   // its a break!
                    breakDetected = 1;
                    startDetected = 0;

                    if(writeCount)
                    {
                        dmxWriteBufSwap();
                    }
                }
            }
            else
            {   // data in the fifo
                dmxData = DMX_DATA_REG;

                if(breakDetected)
                {
                    if(startDetected)
                    {   // some DMX data
                        if(rxCount == fixture.DMXStartAddress)
                        {
                            pByteWrite = pWriteBuf;
                        }

                        if(pByteWrite)
                        {
                            *pByteWrite++ = dmxData;
                            writeBufSize++;

                            if( (writeBufSize >= NumberOfChannels) || (rxCount >= NUM_DMX_CHANNELS-1) )
                            {   // finished receiving this packet
                                dmxWriteBufSwap();
                            }
                        }
                        rxCount++;
                    }
                    else
                    {   // This is the start code
                        if(dmxData == DMX_DATA_START_CODE)
                        {
                            startDetected  = 1;
                            writeBufSize   = 0;
                            rxCount        = 0;
                        }
                        else
                        {   // some other start code
                            dmxReset();
                        }
                    }
                }
            }
        }
    }
    DMX_INT_FLAG_BIT = 0;   // Clear interrupt flag
}


texts: Estimating the current consumption of a DC motor

texts:
Good day, I am wondering if it's possible to estimate the continuous current consumption of a DC motor vs startup or rated current.

I am trying to put together a solar powered aquaponics system. The system would have one water pump that is rated at 24V/250W and two air pumps rated at 12V/80A. Obviously head height comes into play for a specific estimate but I would be happy with a general rule of thumb or a rough estimate of what my continuous power consumption would likely be.

I suspect these ratings are maximum or startup and the continuous wattage would be considerably lower?


texts: Will replacing the MOC3024 with MOC3021 make any change

texts:
I'm student of 10th grade and new to electronics I'm trying to make a switch to control appliances which runs on AC mains and I don't want to use any relay
 see the circuit diagram from the link to instructables below but I'm facing the problem that presently I have MOC3021 other than MOC3041 and it is used in the circuit so can I use MOC3021 in place of MOC3041?

http://m.instructables.com/id/Small-Triac-Switch/

Sorry for my english.


texts:
I just bought my Arduino Ethernet shield – a knock-off one for $10 instead of $60. I connected it up, but it doesn’t work – LEDs light up but do not blink, and no ethernet link is established (ethernet switch doesn't light up, can’t ping, etc.). It’s as if the Arduino cannot communicate with the board.

Trying to work out why, looking closely it appears as if the soldering on the Wiznet chip is messy, and a few sets of pins are bridged. Is this potentially the source of my problem, or could this be done on purpose?


texts: analog vs digital automatic level control

texts:
In an analog broadcast audio chain, an automatic gain control (AGC) or compressor is employed to maintain a nearly constant average audio level fed to the over-the-air transmitter.
In a digital audio chain, say as in a streaming radio station, what is the equivalent technique employed to maintain a nearly-constant average audio level? OR, is there no need to?


texts: Please help identify the positive and ground for BLE antenna

texts:
Please help identify the positive and ground for adding an external BLE antenna, after the chip antenna was removed.  I am connecting an external antenna (not the removed one) to this Nrf51822 BLE module made by Raytac, Model MDBT40.  There is a small blue SMT component right before the removed antenna was soldered, but cannot make out what it is. It seems to have a grey dot on it towards one end.
Cannot find the PCB circuit either for inside the metal shield. The module is mounted on the Adafruit Bluefruit 32u4 BLE Feather.  I do not have access to the bottom of the module.  There is a tiny hole in the motherboard holding the module about where the circle is which I suspect is the positive of the antenna. I thought initially that the trace coming out from the metal enclosure/shield is the positive, but I measured GROUND.
I also enclosed the photo of a MBTB42 module that has a factory external antenna connector.  That one has another version of the BLE chip.
Module is on the left (stock photo).


texts: Debugging dual LVDS display panel color issue

texts:
I'm on TI's AM5708 platform (custom board) trying to drive this Full HD panel via TI's DS90C387 Dual-Pixel Display Interface.

The SoC outputs 24bit RGB into DS90C387. And then DS90C387 outputs 8 pairs of LVDS signal into the display panel.

Mostly it's working - I can read the console which is good progress. However, whenever colored data is shown, the display adds extra noise.

For example, here is an image I want to display:

When I tried to show it on the panel using the fbi tool, it shows this:

[update] I notice any color that uses green has issues:

Any pointers will be much appreciated.


texts:
I have had issues in the past with using too close of an input power supply to the max rating of my main power regulator causing failures. For example, I used a 24VDC supply with a regulator with an absolute max rating of 28VDC. When this PCB was used with a PSU with a long cord, there would apparently be an inductive power spike upon turn on, that would destroy the regulator. The PCB had a 0.1uF ceramic cap on the input line parallel with a 47uF electrolytic cap. The chip also had a 0.1uF ceramic on each input pin. So obviously this inductive spike was a long event, as my capacitance should work for short spikes.

I now am working on another project that I don't have any options to go with a higher rated regulator. I have a 15VDC input supply with a chip with a max rating of 24VDC, recommended 20VDC. This system will be using a long (~6') cord.

What are my options to condition the input supply? A bad solution that I thought of, was to buffer with a linear regulator before this chip, that would only drop a small amount of voltage, but would be rated higher..

Do I just need more bulk capacitance? Something like 100uF+? The switching regulator will be going from 15VDC to 17VDC at up to 15A. Switcher:  MP3428AGL-Z

EDIT: Some clarification:

Power cord length is from the PSU -> PCB
On old PCB, when the PSU was plugged into the PCB and then the PSU was turned on, the regulator would blow. When the PSU was turned on, then plugged into PCB, it would be fine. So the inductive spike was from the initial inrush current.
New PCB has different PSU, much higher quality, so it shouldn't be an issue, but I want to plan for the worst case, as this is an important design.


texts: Thermistor with sharp "cutoff" edge (reaching around 45°C)?

texts: Is there a thermistor which has a very low resistance up to about 45°C and then, within a few degrees, raises the resistance to a very high resistance? Sort of like a self resetting thermal cutoff fuse, but with a raising resistance before cutoff.


texts: Trying to make an electrostatic battery charger

texts:
Can the DC layout charge a battery? I see as if it is in a solar cell format. I know that for a solar cell, when light hits the cell an electron is discharged but the semi conductor only lets it go in one direction. Here the diodes only let the charge go in one direction. If the insulators had 2000V and the conductor picked only 10% and the motor switched charges from postive to negative every 7milisecnds thats 60 revolutions per second, can it charge a battery?
Imagine the charged plastic rods are in a vacuum and not losing charge.


texts: Confusion with interpreting a functional safety diagram of a motor driver

texts:
I have a problem with interpreting the functional safety diagram of a servo motor driver. It has a long manual here but I will present the parts I'm stuck at. The minimum basic requirement for safety is given below with following diagram (from page 186):

As you see above on the right side, there is a section with X8 which is I/O Connection and at page 144 there are definitions of these pins for X8. X8/1 and X8/2 are fault relay output; X8/3 is common and X8/4 is output enable. At page 158 there is an extra information about X8/1 and X8/2 but it is not clear to me. Here is what is given:

What I understand from this diagram is that if a fault occurs and if X8/3 is enabled then X8/1 and X8/2 will act just as a switch and send 24V to a relay K1 where relay's DC ground G is connected to 24V DC power supply ground.
At page 34 there is this rating:

Below I tried to draw my own interpretation of this diagram wiring.
Please see my below drawing:

1-) Is my understanding of the mechanism correct?

2-) What does "Power ON" switch next to the K1 represent in the original diagram?

3-) How should I interpret relay output ratings above: 30V DC 1A and 42V AC 1A? Are they the ratings for the relay K1?

4-) The datasheet does not mention in which conditions "Fault Relay" de-activates. Does that mean it de-activates when there is significant amount of current passing through earth? "(terminals X8/1 and X8/2 ) is signaled by a floating relay contact" What do they mean by floating relay contact here? Is that the relay inside the driver?


texts:
I am putting together a Buffer-cum-Level shifter using dual MOSFET to deal with PWM signal for display backlight control.

This 3.3V PWM signal is driven by MSP430G2452 and would be reaching the panel through cable. I want this MOSFET to serve two purpose

Act as level shifter (convert 3.3V PWM to 5V PWM) if R3 is mounted.
Reason is some panels need 5V PWM.
Act as buffer / voltage follower if R4 is mounted.

Please help me with the following

What are the electrical specifications (thresholds) to be met for both modes of operation mentioned above?
Are there any mistakes on my circuit? Can 3.3V be switched using 3.3V and is FDC6327C the right choice?


texts: Downsides of Extending a USB Bluetooth Antenna?

texts:
I found an interesting video about how to extend the range on a USB Bluetooth antenna by resoldering a new antenna in its place: (https://www.youtube.com/watch?v=cwKWOdOHiWY).

I'm planning on using a Bluetooth enabled portable EEG as a input device for an arts display in a few months, and I'm somewhat concerned about interference from the audience's Bluetooth enabled phones.

The performer wants to be able to walk around the audience as a part of the performance, which might be about 20m from the stage where the computuer will be located.

What are the potential downsides of this approach? Is the extension antenna more prone to interference? Is it a good application for this kind of project? Is it better to have the extended antenna mounted on the ceiling near the center of the room?


texts: What is the B5 pin for USB-C cable? Something wrong with Wikipedia?

texts: On Wikipedia there seems to be inconsistency between the first and second tables: the first table says that B5 pin is for Configuration Channel, while the second table says that the B5 pin is for V_CONN power. What is exactly the B5 pin and the yellow wire for?


texts: Will the replacement LED driver work for the LED light unit I have?

texts:
I have a light unit with 12 LED in series.
The specs for the driver that fail are listed below.

LED Driver, Model XSD7X1LE.
Input: 120VAC 50/60Hz, 0.04A λ>0.5
Output: Constant Current: DC 280mA 19VDC
Load:.5..7X1W

The replacement that is available has the following specs with the differences shown in Bold.

LED Driver, Model XSD7X1LE.
Input: 120VAC 50/60Hz, 0.08A λ>0.8
Output: Constant Current: DC 350mA 24VDC
Load:.5..7X1W

I'm concern about the change in VDC from 19 to 24.


texts:
So I use Altium for designing and on most days a quick restart generally makes things normal. But today Altium refused to start at all.

I could see in task manager multiple instances of Altium though all were frozen.

Any way to get the Altium to run or do I need to uninstall and install the whole thing again?

Also any ideas why such a thing would happen so any mistakes can be avoided in the future?

Thanks!!


texts: Need help isolating source of interference

texts:
I'm pretty new to electronics, but have been successfully working with a Spark Core (www.spark.io) and some simple drivers/circuits for now. That said, I've run into a problem.

I have a Spark Core powered from a 9V power source, via a 5V regulator (LM7805) with the necessary caps between supply and out lines and ground (as per the LM7805 datasheet). The same 9V powers a motor (LEGO PowerFunctions) via a SN754410 dual H-bridge (getting its VCC from the 5V line). The Spark Core controls the SN754410 via 2 PWM signal lines, each with a 10kOhm resistor. This all works fine (meaning I can make a motor turn forward/backward, and control rotation speed using PWM).

I also have a mini RFID reader (this one: http://www.seeedstudio.com/depot/Mini-125Khz-RFID-Module-PreSoldered-Antenna-35mm-Reading-Distance-p-1722.html?cPath=19_24) connected to the 5V line, as well as to the TX and RX pins on the Spark Core. This works fine in isolation as well - it detects tags at 3-5cm distance (1-2cm if powered from the 3.3V off of the Spark Core), and nicely reports tag ids.

All circuits share the same ground, coming from the 9V power source.

The problem starts when I have AND a motor running (via PWM) AND try to use the RFID tags - the motor will run but the RFID reader does not see any tags. As soon as I bring my PWM signal down to <10 (out of 255), the RFID reader starts picking up tags again.

Here's what I tried:
- I have tried putting an aluminum foil cone around the RFID reader's antenna, to no avail.
- I have tested at PWM signals 200, 150, 100, 50, 10, 5 and 0. Only at 5 and 0 do I get RFID tags read.
- If I disconnect the motor, but still set my PWM signals, the RFID reader works fine.

This all leads me to assume I have some interference in my circuit, caused by the motor. I'm thinking I should probably put some resistors or caps in some of my wiring, but I'm not sure. I need some guidance. Here is a rough schematic of my setup:

simulate this circuit – Schematic created using CircuitLab

upon request, here are a few pictures of the mess that constitutes the circuit in question :) :

BTW, the two blue (-) bars on my breadboard (GND) are connected together via a white colored wire. One red bar (+) carries the 9V supply, the other red bar carries the regulated 5V.

How do I go about eliminating the interference that prevents my RFID tags from being read when the motor runs?

Thanks!


texts: Is my understanding of this level shifter correct

texts:
I am considering using this TI LSF0102 level shifter in my circuit - but would like to understand, based upon its datasheet, if I have my understanding correct.

It says it has a 100mA current rating, is that a limit on each of the 2 channels? Or total combined limit?


texts: Do batteries (voltage sources) supply constant voltage?

texts:
I know that voltage sources are those that can supply constant voltage. The producing current may vary with the load.

Suppose I have a rechargeable battery. I fully charged it and started using it. After some time I have to charge it again.

I'm not so clear about this. What happens when I use a battery in a circuit? Does the voltage supply capability of the battery decreases after some time? That means if it can supply 5V, and after using it for a few moments it will provide a voltage less than 5V.

If so, how can we say it's a voltage source as it can't supply a constant voltage? My understanding is not so clear. Can anyone help me?


texts: Controlling Wemos D1 power with N-Channel MOSFET

texts:
I am trying to implement something similar to this: https://youtu.be/nbMfb0dIvYc?t=4m27s

Basically, the idea is that the microcontroller (a Wemos D1 Mini in my case) is powered up by an external switch. As soon as it starts up, it sets up a MOSFET so that it can keep its power connection until it finishes whatever job it is set up to do. In the end, it "kills itself" by cutting of the power through the MOSFET.

The problem? The original design uses a P-channel MOSFET. Since I had no P-channels on hand, I tried to implement something using an N-channel MOSFET (IRZL34N). Here is my schematic:

However, no matter what pin I tried to use to control the MOSFET, there is always some residual voltage on the pin. For example, using D8, I'm getting about 2.2V on the pin (and the MOSFET gate) - enough to keep the MOSFET open.

Now according to the Wemos D1 Mini Schematic, that pin only has an external pull-down resistor. So whatever current makes it through does so through the internal ESP8266 circuitry. And I have no idea what the schematic is (and even if I could find it, I would probably not be able to understand it :) ).

Anyway, to make a long story short - is there any way to implement this using low-side switching (with an N-channel)? Or is my time better spent just going out and buying a P-channel MOSFET?

I did find another similar question on the site - but the only solution there is... well... "use a P-channel"! :)

Thank you!


texts:
So I'm trying to use a couple of rectifiers.  Specifically, the "NTE5326" and the "36MB120A."

I've tried following videos on how to calculate for a smoothing-capacitor but to no avail.

If you use these rectifiers can you please give the capacitance value for each, and show how you got your value?


texts: Voltage range of a differential pressure sensor px26, and opamp saturation

texts:
Im using a px26 001GV differential pressure sensor for a project with arduino, here is the data sheet. (http://www.omega.com/manuals/manualpdf/M1608.pdf)
Now, I have few questions regarding this.

1) I'm using this around a valve to know the differential pressure, lets say side A and side B
Now if side A>B i get a positive voltage in milli volts, what if side B>A would it give a negative voltage? so would I get a range of voltages for its full functionality from negative to positive like say -8mv to +8mv?

2)I'm using an op amp to amplify the reading so I could amplify 8.6mv to 1.8V and then the opamp saturates, is there any way around this?

3) the opamp AD620AN which is a instrumental amp to be precise , needs voltage ranges -5 t0 +5 so i used a 10 volts dc, made a voltage divider, created a virtual ground. So what if I connect this system to arduino (0to5V range) would the divider cut off the system to (-2.5 to +2.5)?If so, should I check my circuit by using a 5V Dc and using the divider and check how the opamp responds?

PS: I'm new to this , please try to avoid all the electrical lingo, I wouldn't understand it. Thank you for your effort!


texts: Middlebrook's Method VS Tian's Method VS Middlebrook's General Feedback Theorem

texts:
For https://sites.google.com/site/frankwiedmann/loopgain , how is Tian's Method different compared to Middlebrook's Method and Middlebrook's General Feedback Theorem ?
Tian's Method

Middlebrook's Method

Middlebrook GFT Method


texts:
Im planning on buying a useful book for PCB design. Until now, I have these two options:

High Speed Digital Design
Circuit Designers Companion

Both books seems OK, but the first one (the older one) is almost 2x more expensive.

Anyone with experience with one of two books or both? Would you recommend me another book? If so, why?

Thanks!


texts: Heat Sensitive Fan Project not providing desired output to fan

texts: I recently built a circuit I found online for a temperature sensitive 12 volt DC fan for the summer. The output seems to be regulated to around 0.23 amps which isn't enough to power the fan. I'm still new to electronics and I can't figure out how to troubleshoot it. I would appreciate an explanation as well. I've provided the schematic.


texts:
I'm working on an autonomous project with a 3.3V powered Arduino and I need to add a led that power on when some actions happened (pressed button etc..). This LED needs to be seen during a sunny day outdoors.
My question is: which type of LED I need in term of lumens and voltage?
I need to keep in mind that my project is running on a 3.3V alkaline battery.

Thank you for your help!


texts:
simulate this circuit – Schematic created using CircuitLab

Let's say we know the values of \$Z_1\$, \$Z_2\$, \$Z_3\$.
We know the value of \$I_3(0)\$ - the current in the wire with \$Z_3\$ and \$E_3\$ when the switch \$S\$ is in the position 0. We also know \$I_3(1)\$ - the same current when the switch is in position 1.

The task is: find \$I_3(2)\$ - the current \$I_3\$ when the switch is in position 2.
I have tried using the compensation theorem, replacing the wire with \$Z_2\$ with an ideal current generator, but that didn't work out.


texts:
When looking at schematics of amplifiers, filters etc, I often find that the output to the audio jack is going through a resistor in the 470-680 ohm range and also shunted to ground using a high value resistor, like in this example:

simulate this circuit – Schematic created using CircuitLab

What's the meaning of R2, I just know it's something like a "load" resistor. And how about R1, is it needed for when nothing is connected to signal? What are appropriate values for those resistors? Do I need them when I connect between two op-amps or just to the output jack? I hope someone can clarify those questions or point me to a source where I could read more about these basic topics.

Extra question: what happens when I add a coupling capacitor between R1 and R2? Version with added capacitor:

simulate this circuit


texts: Change programatically pin number in shield software library?

texts:
I was wondering if it is possible to change the software library for writing INO arduino sketches so that it would expect arduino shield under different set of pins.
For example I want to use theese shields together: RedFly Wifi Shield:

http://shieldlist.org/watterott/redfly

and Arduino motor Shield rev3:

http://arduino.cc/en/Main/ArduinoMotorShieldR3

I see that I cannot stack them together because they share pin D3 but if I connect RedFly shield not by stacking but with separate wires I can connect the Red Fly shield to any 4 pins I want, for example to D20-D23 of my arduino mega board.
I expect that the software library for using Red Fly won't work then. The question is: Are those libraries configurable, so they could be changed to use other set of pins? I mean is it possible without rewriting the while code?
Specifically I would like to know if it is possible to any of above shields. I hadn't bought any of theese yet, and I don't know what the software libraries look like.

UPDATE:
Thaks for your answers, but I couldn't found the source code of the RedFly.h library for using RedFly WiFi shield, so I don't know if it can be rewritten to use other pins. The usage examples (  http://www.watterott.net/forum/attachment/936  ) suggests that it does not takes pin configurarion in neat way (as arduino LCD library does). Anybody work with RedlFl WiFi shield? Is the library source code available on the web?


texts: Bjt active in circuit, \$ V_{cb} \$ is ignored, why?

texts:
Bjt in active region, physical representation:

In circuit:

Why is that in circuit base connects to emitter? Shouldn't it connect to "P" area, and then collector node and emitter node connect to "P". So P should be in the middle between C and E.

No?

Where is \$ V_{CB} \$ ?


texts: Resistor technologies that guarantee failure mode of OPEN and not short--need docs to prove

texts: From chats with several resistor manufacturers, it seems that there's a consensus that certain resistor technologies at high impedance ~120Kohm or more will always open and never short. Does anyone have documentation that reinforces this "fact"? Any ideas?


texts: Purchased a cheap LED monitor with no power leads, how do I find the power leads?

texts: I just purchased a cheap TFT LED monitor and it has no power leads, how do I find where to soldier the power leads onto this unmarked circuit board?


texts:
when we say that we are talking about a n-MOS in saturation region, what exactly can be said about the variation of \$V_{DS}\$   the drain-source voltage with the increase or decrease in the value of channel length modulation parameter?

was solving a question based on it, so rather cut out the numbers and posted my doubt


texts: Can I make a rectifier to convert from AC to DC?

texts:
I have a project that calls for an 18VDC power supply. I've found one that meets specs online for about $40.00, and I've found an 18VAC power supply that meets specs (apart from being AC) at my local science & surplus store for $3.99.

So I was thinking about this over the weekend, and it seems to me that I could run the AC through the rectifier (assuming the fwd/rev voltage is within diode parameters) and get DC out the other end without a significant voltage drop. But c'mon...is it really that simple?

Can I really get a working, safe, and reliable 18VDC power supply for $3.99 plus four diodes? Or should I stop being cheap and get the out-of-the-box 18VDC?


texts: Question about differential signals as input of an operational amplifier

texts:
I'm studying the circuits which are used to implement operational amplifiers. For example, I've studied the two stages amplifier (in which the first stage is a differential amplifier with differential to single ended transformation, the second stage is an inverter with active load), the telescopic cascode, and other circuits. Here a picture of these circuits:

I noticed that in all of these circuits the book I read always assumes a differential input, that is two (small) signals with the same DC value and amplitudes which are equal and opposite. As a consequence of the superposition principle and of the symmetry of these circuits, we can divide the circuit into two parts and all the nodes on the axis of symmetry become ac grounds. This simplifies the analysis, in particular it becomes easier to find the differential gain.

The question is: who says that, when I close these circuits with feedback, I will have at the inverting and at the non-inverting terminals a perfect differential input? It appears as if the book assumes that I will get for sure this situation. In other words, who says that, when I close the circuit with feedback, I get the same differential gain (if I close the circuit with feedback, in general I don't have two perfect differential signals, and as a consequence I am not allowed to divide by symmetry the circuit and to consider all the nodes on the axis of symmetry as ac grounds)?

For example, let us assume that I use one of these circuits to implement the classic inverting configuration:

You can see that the non-inverting terminal is fixed at ground, then it is impossible to have a differential input for the op-amp.

Thank you

Image added for the comment: