texts: Design a circuit for rechargeable batteries supplied by a solar panel and generator?

texts:
I want to design a circuit for a rechargeable battery (or batteries) that can be charged by both a solar panel and a generator. I am working on the same project as described here, but my focus is on the actual switching between the two sources of power generation (rather than how much power the generator will produce).

Here's a rough description of the system:

2 sources of power:

solar panel that supplies continuous power while system is idle
generator that supplies a burst of power when system is active momentarily (< 5 seconds)

2 or more batteries:

a "primary" battery that acts as the voltage supply for the rest of the system
a "backup" battery that is continuously being charged by the solar panel
a "secondary backup" battery that will be charged in bursts by the generator

The idea is to have the primary battery dedicated to supplying power for the system, and switch this with the backup battery when the voltage of the backup exceeds the primary (using an analog comparator perhaps), or when the voltage of the primary depletes below a certain amount.

The context of this project is essentially a fingerprint authenticated door lock system that is powered by the two sources mentioned. The handle

Here are some of my thoughts and questions:

Do I need three batteries to be charged separately? Or should I only have a primary battery and one backup battery? What's the best type of battery for this?
The latter option would require switching between the solar panel and generator whenever the generator is activated, i.e. stop the charging from the solar panel and allow a burst of charge from the generator, then resume charging from the solar panel.
Thus, I would have to figure out if the power generated by the generator in the amount of time it takes to turn the handle is greater than the power "lost" by not charging through the solar panels for that period of time.

The circuit I've come up with so far looks like this:

simulate this circuit – Schematic created using CircuitLab

It is more of a general idea than a real circuit schematic.

The solar panel and generator are switched using a PNP transistor. When the generator is outputting a voltage at the base of the PNP, the current from the solar panel stops flowing. When the generator is not outputting a voltage, the current from the solar panel is let through the PNP from emitter to collector.

Now the next part does not make sense schematically. The comparator is meant to compare the voltage of the two batteries. The one that has less voltage should be charged by either the generator or solar panel. This is called the back up battery.

The next comparator again (redundantly?) compares the voltage of the same two batteries. The one that has greater voltage will become the primary battery, which supplies power to the rest of the system.

Does this idea seem reasonable? How can I efficiently switch between the batteries based on their relative voltage? (Low power consumption is a huge consideration here.)

Thank you for taking the time to read over my ideas. I would really appreciate any help with this!


texts:
Are there any other options for an extremely low loss switching circuit with extremely low switching frequency (about 4 times per day) and voltages from 0-3V with currents <2mA.

Current ideas include:

latching relays (<100mOhm, but use ~50mW for 5ms to switch) => would only consume power during switching, which is infrequent
analog signal switches (have about 100mOhm resistance and leakage/quiescent current in the tens of nA range) (eg. TI ts3a24159) => continuous quiescent power consumption

Does anyone have other solutions?

FYI: the switches are used in a "rectifier" that only changes the polarity of its input voltage about 4 times per day.
It will be part of a TEG (thermal energy generator) that scavenges energy from a temperature difference and stores it in a battery. Since the temperature difference can be of both polarities the TEG will also output two different voltage polarities.
So basically I want to minimize the total energy loss over a long period of time.


texts: When do you release and re-aquire control over SDA around an i2c Ack?

texts:
I am having odd behavior with Energia's Wire library, so I figured that I would attempt to do i2c myself.

I'm writing my own (bit-bang) implementation if i2c and keeping it pretty simple.  For now, I just want to detect a particular i2c device.  Here's my basic algorithm.

Start the message by driving SDA from High to Low while SCL stays high.
Send 7 bit address one bit at a time by driving SDA to high or low while SCL is low and then changing SCL to high so the slave device will read each bit.
Send 1 bit write or read.
Receive Ack from the slave.
End the message by driving SDA from Low to High while SCL stays high.

I know the above may be a bit oversimplified, but I just wanted to get things in context.  I'm having trouble with step 4 and knowing the particular timing as when to release and re-aquire control of the SDA line during an Ack.

So, after the last read/write bit has been set on SDA and the SCL set to HIGH, I need to know what the order of operations is in order to get an Ack from the slave.

I've tried every combination I can think of, but it doesn't seem to be working properly.  It would seem that I should do the following:

setMode(SDA, INPUT);                //Release the SDA line to the slave device
digitalWrite(SCL,LOW);              //Pulse the SCL line
digitalWrite(SCL,HIGH);
int ack = digitalRead(SDA) == LOW;  //Read from the SDA line
setMode(SDA, OUTPUT);               //Seize control of the SDA line

The sequence above doesn't seem to be working.  My digital analyzer isn't recognizing my communications as it should.

Any corrections in my assumptions or adjustments to the code above would be greatly helpful.

For Further Clarification:

I'm using a development environment called 'Energia'. It is a fork of Arduino and is used to 'simplify' the process of programming of TI MSP430x processors. Anyway, it doesn't seem to have any concept of 'OpenCollector' mode.

It's either Input, Output, or Input_Pullup. I'm wondering if Input_Pullup isn't their version of OpenCollector mode. I'll try that.. There is an interesting discussion of Input, Output, Input_Pullup here:

Energia Constants


texts: How to carry out signal integrity simulation with IBIS models

texts:
I need to determine if there will be high speed effects on the clock signal. I have not done such a simulation before.

I have the IBIS models of the circuit components involved. I think I still need to have PCB track information which will tell me the length of the tracks and perhaps the dielectric constant and I must make sure that the ground plane is continuous under the clock signal.

I have cadence design suite containing allegro design entry cis and allegro design entry hdl with AMS simulator.

I first converted the IBIS models to PSpice since I don't think that IBIS models can be simulated directly in the software tools I have. Now I do not know what to do next.

I realized that while the IBIS model clearly shows many pins of a device, its conversion into PSpice model contains only 1 or 3 pins. If its 1 it will be input, if it is 3 it will be input, output and enable. WHY!?

I have an IBIS model of the clock oscillator. Its conversion into PSpice gave me a single block with a single signal, named input. Actually the customer service person at Cadence did the conversion for me and I checked it myself later by doing it myself once I understood how to use the tool. How can the oscillator PSpice model (generated from its IBIS model) have just 1 signal and that also input, it must be an output right?

So I do not understand why the PSpice models do not have similar interface to the IBIS, I do not understand how to enter the PCB track information into the spice simulator. Do you have any advice?


texts: Design of ESC for bldc motor having encoder

texts: Is it possible to vary the speed of propeller or BLDC motor from maximum value to minimum value per cycle of rotation. I mean blade accelerated per half cycle and deaccelerated per next half cycle. What is the design criteria of ESC for this operation? To change the high speed low speed region on rotational plane I think encoder are necessary. How can it achived through a closed loop control? Any suggestion will be helpful for me


texts: Can a zener diode with a higher power dissipation be used in place of the original one in an audio amplifier?

texts:
Following my Marantz PM-68 repair question, I would like to change a faulty zener diode used in the amplification stage.

I don't really understand the purpose of this diode but I guess it's used for some kind of coupling between the positive and negative parts of the audio signal.

I had a look at the service manual, but couldn't find the exact replacement for this diode (BZX79C3V6). The guy at my local electronics store sold me a BZX85C3V6 diode, which has a higher power dissipation rating than the original one (1.3W instead of 0.5W). He told me this wouldn't be an issue.

Do you think it's safe to use the diode he sold me? Do you think it could change the accuracy of the audio signal?

Here is the diode I'm talking about:


texts: Transfer function derivation from Op-Amp linear control system

texts:
Need to derive transfer functions for blocks B, C and D, unsure on the best method to do so.

Any suggestions?


texts: How long will a battery last based on these numbers

texts:
Hi I asked this question on SU but seemed to have gotten into a bit of trouble, I was referenced here.

I am getting into doing hardware build based on things like microcontrollers and microprocessors.

I am curious how to calculate how long a battery can power a certain object.

Let's say we have a motor that says something like

3.5V and 100W

I don't have a motor yet a search lead me to this one: AmpFlow G43-500 Motor

The big G43-500 motors work great for applications that require sustained power output of up to 500 Watts (0.67 horsepower).

Specs
Watts - Continuous  500
Diameter    4.3 in.
Length  5.3 in.
Efficiency  80%
No-Load RPM @ 24V   3300
Output Shaft    11-Tooth #25 Sprocket
Weight  8.6 lb
The above specifications are for 24V. The motors can also be used at 12V or 18V. The RPM is proportional to the voltage so running at 12V will result in half the no-load RPM that is shown above for 24V. The lower voltage also reduces the maximum achievable torque by 50%. The motors have also been tested and used at higher voltages resulting in higher RPM, torque, and power. Shorter duty-cycles are recommended for higher voltages to allow the motors time to cool.

I also saw these specs on another site

Model                G43-500
Watts - Continuous   500
Diameter (inches)    4.3
Length (inches)      5.3
Efficiency           80%
Voltage*             24*
No-Load RPM @24V     3300
Output Shaft         Sprocket

The above specifications are for 24V. The motors can also be used at 12V or 18V. The RPM is proportional to the voltage so running at 12V will result in half the no-load RPM that is shown above for 24V. The lower voltage also reduces the maximum achievable torque by 50%. The motors have also been tested and used at higher voltages resulting in higher RPM, torque, and power. Shorter duty-cycles are recommended for higher voltages to allow the motors time to cool.

or something like that, how can I then say okay I have a  3.5 Volt 1000mAh battery

How long should it last?

If there's a formula that I can follow that would help. I am not trained EE.

[EDIT]
I want to thank David Schwartz for
actually providing a good information to help clarify what I needed
to then go do further research and learn the math behind all of this.
I'd like to add this tutorial on how to calculate how much
batteries you will need.
I didn't go to school for engineering so this is all new to me.


texts: Resistors in battery-powered LED device and Arduino

texts:
I have tiny christmas tree that has about 20 small LEDs, which are powered by 2 AA-batteries. So I'm assuming the LEDs are 3V (because of 2 AAs). This tree was bought in a store, as is.

What I want to do, is hook up the little tree to an Arduino and control the lights with some sensors (lights, sound, etc). I was planning to just connect the battery terminals to the 3V Arduino output.

Is it safe to assume that the battery pack has a built-in resistor somewhere and I can just safely connect it to a 3V output of the Arduino, or would it be wise to have an extra resistor somewhere?


texts: Does supply voltage affects stepper motor driver heat dissipation?

texts:
Below is a block diagram of a stepper motor controller with an external mosfet h-bridge that drives one of the stepper's coils. Let's say that the coil has 2ohm DC resistance and 3mh inductance, the motor is stationary, and the current through the coil is 2A (stabilized by the stepper controller).

Does the average current from the source Vm depend on Vm's voltage (e.g. doubles when reducing Vm from 24V to 12V)?
Does the power dissipation on the mosfets depend Vm's voltage (e.g. increased X4 when reducing Vm from 24V to 12V due to the fixed Ron of the mosfets )?

https://www.trinamic.com/fileadmin/assets/Products/ICs_Documents/TMC5160_Datasheet_Rev1.10.pdf

EDIT: added A,B,C,D transistor references.


texts: How do I cater for high instantaneous current in a power supply?

texts:
I'm trying to design a power supply for a GSM modem with 2A instantaneous current, but only
210mA operating current.

I believe my power supply does not have to be rated at 2A does it?

I'm wondering if an inrush current limiter like a thermistor will help protect the power supply, while still ensuring the modem works fine within its limits.

Is this ok?


texts: Hi I am using the SN754410 h-bridge driver to try to control a motor using two switches.  As I understand the SN754410 should be identical to the L293D.  I have hooked up a circuit and I think I have followed this tutorial correctly, however when I try to use it the motor will not work when I try to attach pins 2 or 7 to a 5 volt positive source the motor will not start.  Even stranger when I try to attach one of those pins to the ground the motor starts in one direction, and when the other pin is attached to the ground the motor spins in the other direction.  Can anyone explain this weird behavior to me.  I understand that the problem is caused by floating inputs acting as a high and when one of the inputs is brought low the motor moves, but i do not understand how I would fix this problem, as suggested i have connected a diode between the input and ground, however the circuit still doesn't work.


texts: Is the there a KiCAD plugin for making automatic board outlines?

texts:
Is there a plugin for kicad that can make simple shaped board outlines automatically? For example rectangles, rectangles with rounded edges etc.
I think that could be super usefull. Beacuse at the moment I edit the cooardinates of the lines manually to do precise cutouts.


texts:
Planning to use a green LED (forward voltage 2V, forward current 30mA) on a 12V circuit so
using as resistor calculator (led.linear1.org/1led.wiz) I bought a 390 ohms, 1W resistor.

However after connecting the resistor to the positive terminal the led refuse to light up.

Is the calculator wrong or am I making a mistake somewhere? (gather I am a complete novice)


texts: Possible to charge one phone off another?

texts: What's stopping the ability of charging a cell phone from another cell phone? If I were to create a crossover/patch USB cable and connect it between two phones or tablets, would there by any way to have one of their USB ports provide a charge to the other?


texts: Contradiction in solution for ideal transformer

texts:
I was trying to analyse an ideal transformer with one ideal independent voltage source on each winding.
I got a relationship between those voltage sources but it contradicts the fact that both voltage sources are independent of each other and there should not be any such relationship between them.
Here is my solution:

What is the reason behind this contradiction?


texts: Powering mutiple Infrared LEDs through a single Arduino Uno pin?

texts:
I'm doing this project where I control an RC Car using infrared. Everything is perfect with 1 IR LED, connected to a 220ohm resistor. I'm worried about the range of the signal so I'm thinking of using multiple IR LEDs (let's say 4 to 6 LEDs) to emit the signal.

My problem is how do I achieve this while controlling them through a single pin?

For testing I tried connecting 2 normal red LED serially through a 220ohm resistor and both of them became dimmer. The LEDs needs to be bright.

On hand now I have the IRF520 transistor. Will it work?

I bought my IR LEDs online, while it doesn't say it's part number it comes with this description:

IR Transmitter
Emitted color:infrared
Lens:5mm, water clear
940nm wavelength
Forward current:50mA
Forward voltage: 1-1.4V


texts: In OrCAD PCB Designer how do I get the trace width of a signal

texts: In OrCAD PCB designer, how do I see the trace width of a signal? When I click the "i" or "Show Element" icon it gives me everything but the trace width.


texts:
I am trying to build a fetal heartbeat sound detection using Adafruit AGC Electret Microphone Amplifier - MAX9814. I attached the MAX9814 mic to the hole of wood fetal hearbeat stetescope (picture attached).

Parallel the VDD and GAIN to get 40db output. The battery I use is two 1.5V button cell connected in series, so I get 3V power to drive the MAX9814 modules. I use the wiring from this [link][2] (picture attached).

Everything is ok when the nurse using a earphone to hear the fetal heart beat.
but when I connected the MAX9814 Modules output to the AUX input of a speaker like this one (picture attached)
I get hissing or buzzing sounds. I know the adafruit tutorial suggested for not to connected the output to any speaker or I'll get horrible feedback effects. But is there are any suggestion to able connect this MAX9814 output not just only to earphones, but speakers too? so does the couple can hear the fetal heartbeat sounds together with speakers.
I also play with PAM8403 amplifier module like this [one][6] (picture attached)

I connect the MAX9814 mono output to the L input of PAM8403 and the MAX9814 ground output to ground of PAM8403. I soldered small speaker (didnt know how much watts its are, but I salvaged it from the speaker I notice before above) to the L output only. So does I only using 1 channel of the PAM8403 output. connect the 5V power supply from 3.7V 18650 battery (boosted to 5V using DC-DC step up) (picture attached)
for your information, the component between stepup and 18650 battery is TP4506 Lithium battery charging module. and the component with yellow and blue wires is 3.5mm jack female (picture attached)
I connected the L and R of the 3.5mm jack female together with yellow wire and the yellow connected to the L input of the PAM8403 Module. the ground of the 3.5mm jack female is connected with blue wire and the blue wire is connected to the Ground input of the PAM8403 Module.
I test the DIY speaker first using my smartphone playing Tones and I-Dance Monkey song, and it works like charm, but at max turn of PAM8403 potentiometer and max volume of my smartphone, the sounds like distorted.
After several tests, the speaker work as good at lower or middle volume, but when I increase the volume to maximum turn of the potentiometer, the hissing or buzzing sound is back.
Any thoughs whats wrong with it? at lower or middle volume, the sounds too slow to hear the heartbeat (I use my heartbeat for the test, I attached the wooden stethoscope hole to my chest) so I need to play it at max volume without hissing or buzzing sounds. Or there are a trick to reduce the hissing or buzzing sounds?
Please apologize my bad quality of the pictures and my english, as this my first question in this forum.


texts:
I am currently working on my hexapod project that involves an Nvidia Tegra TX2 Development kit. The issue is as follows:
The Tegra (as the hexapod should be able to operate autonomously) is powered from a 6s Lipo battery which is able to supply enough electricity for a decent amount of time. However I would like to be able to hotswap the lipo battery (for the same model) and would like to know if and how this is possible. I am NOT intending to buy the 100 USD PowerBoard from Sainsmart.

Today I had a discussion with my instructor who recommended the following circuit:

Using the 2 Zehner Diodes the Lipos should be able to power the circuit without interruption and not destroying each other by loading.

I am sorry my electrical engineering skills are not very advanced even though I have a bachelor in applied physiks. So if anybody could help that would be great. If you need further clarification please let me know!


texts: Why doesn't the voltage of the load fluctuate in a Zener Diode circuit?

texts:
I'm very new to this field so sorry for this silly question.

What I've learnt is that when any number of devices are connected in parallel (and none in series with the battery) with the battery, the potential difference across all the devices is equal to that of the battery.

If 2 resistors are connected in series in one 'line' of the parallel circuit, how the potential is spent by the two resistors, their values of resistances, etc. shouldn't affect the voltage of the other 'lines' of the parallel circuit.

So when the Zener diode and the load are connected in parallel with the voltage source, whether the voltage is constant in the diode or not shouldn't affect the load from having the same potential difference as the voltage source right?

And yet, even though parallelly connected with the load, the diode manages to affect the voltage of the load.

How is this accomplished?

P.S - I may have misused some terms so sorry in advance :)


texts: Why is emitter resistance not reflected to base?

texts: Considering the first circuit, I want to determine the output resistance seen looking into collector of Q17. When the source \$v_i\$ is zeroed out as shown in the second figure, shouldn't the resistance across the transistor Q16 be considered \$r_{\pi16}\$ instead of \$r_{e16}\$ because \$r_{e16}\$ isn't directly connected to ground. It is reflected to the base and that base resistance is connected to ground.


texts: Arduino- Duty Cycle Changing When Frequency Is Increasing

texts:
I’m currently trying to increase the frequency from a pin from an Arduino using PWM. I’m using the Timer1 library as it has functions to output signals.

I connected a push button to my Arduino and this is meant to increase the frequency of the pin once pressed . But every time the button is pressed, the duty cycle is also changed. Also the frequency changes multiple when the button is pressed. I think that has something to do with the lastButtonState logic.
I was wondering if there’s anything that can implemented in my code that can increase the frequency but keep the duty cycle the same.
Thanks in advance.

#include <TimerOne.h>

int buttonState = 0;
int lastButtonState = 0;
int period = 1000;
int sig_out = 9;
int sig_out2 = 10;
int button =2;

void setup() {

  pinMode(button,INPUT_PULLUP);
  pinMode(sig_out, OUTPUT);
  //pinMode(sig_out2, OUTPUT);
  Timer1.initialize(1000);
  Timer1.pwm(sig_out,507,period);
  Serial.print(period);
  //Timer1.pwm(sig_out2,456,900);
}
void loop(){
    buttonState = digitalRead(button);
  if (buttonState != lastButtonState){
     lastButtonState = buttonState;
     if (buttonState == 1){
      period -= 10;
      Timer1.setPeriod(period);
     }
  }
}


texts: Is Rg, calculated in the linked PDF calculating the pulldowm/pullup resistor for a MOSFET gate?

texts:
I stumbled upon the following paper while looking for ways to calculate a specific value for the pullup/pulldown resistor for the gate of a MOSFET. I see several calculations for Rg. Is that the pullup/pulldown resistor for the MOSFET?

Related see this Q


texts: Is it wrong to use the mnemonics "ELI the ICE" [ From my understand means if its inductive current LAGS voltage and if its capacitive current LEADS]  in understanding the phase relationship of a Parallel RLC circuit? because I've just read in a book that its the opposite because given a parallel LC circuit,if current in the inductor is greater than current in the capacitor the current lags or if XC > XL current lags.


texts: MC34063A: Problem with obtaining step-up performance

texts:
I am working with a MC34063A voltage regulator in order to prototype step-up power management solution, with control logic to switch between three different output values. I encountered some issues while trying to assemble the circuit exactly accordingly to my needs - the output oscillated around 80-110 mA depending on the input setting. I decided to go back to the datasheet and to try build the exemplary step-up configuration in order to better understand what might be the problem while creating my own one.
I built the circuit on a breadboard with the only differences to the datasheet  one (picture below) being: 180uH coil, no Rsc resistor (no current sense, pins 7 and 8 connected together). When the input is set on 12V, the output measured is 10.96V. When increasing the input, the output increases accordingly, always staying around one volt below the input value.
Any advices what may be the reason for this kind of performance instead of obtaining the expected v_out value of 28V?
Thanks in advance.


texts: Altium: Including Text of Evaluated Parameter in Value of Second Parameter

texts:
I would like to include the text value of one parameter in the value of a second parameter. In my case, I am trying to add on the text from the schematic SheetNumber parameter to the end of the text of the schematic DocumentNumber parameter.

In other words, suppose the DocumentNumber parameter is populated with "ABCD" and the SheetNumber is "2". I want to populate the DocumentNumber parameter dynamically with "ABCD-2" (or "ABCD-1", "ABC-3", etc depending on the value in SheetNumber).

It would be nice  if there was a way for a parameter to be evaluated while within a second parameter, like "DocumentNumber-=SheetNumber" but this does not work. Is there a way to do this in Altium?


texts:
I am currently developing a robot with multiple modules that have to be connected using CAN (at 5V or 3.3V). The robot has 2 strong DC motors (with spikes over 100A) and also operates close to powerful magnetic fields.

In order to have a compact design I am considering to use flat-flex for the connections, but I am concerned about not using twisted pairs. Is it critical to have twisted pairs?

Do you have any suggestions for a cable type that would be compact and also suit such an application?


texts:
For a transfer function, a zero is defined as the value of s for which the transfer function's value is zero. A pole is defined as the value of s for which transfer function's value goes to infinity.

However when dealing with transfer function for an amplifier, a zero depending on right hand or left hand may decrease or increase phase, introduces +20 db/decade in gain and similarly for a pole (left hand for stability), decreases the phase response and introduces -20 db/decade in gain.

What's the significance of the definition of pole and zero for an amplifier's frequency response? Is it not valid?


texts: What is the wrong with this simple sine wave generator circuit?

texts:
I've designed this circuit myself aiming to generate sine wave at the collector of the transistor, but I doesn't work. the current at the collector is DC.

Is it a simulator error or the design is wrong ?
What modifications should I do to make it works ?

I know that there are many oscillator circuits on the internet but I just would like to know what the error in this circuit is.


texts: Chassis Grounding a Bipolar Floating Power Supply

texts:
I'm building a simple function generator powered from a 24V AC wall adapter.  I've rectified the incoming AC to 24V DC using a full wave bridge and an LM317.  I intend to split the supply into +/-12V rails with a virtual circuit ground (see image below).

My BNC connectors need grounding and my idea is to ground the chassis to circuit ground as shown in the diagram.  Are there any problems doing this?  More specifically, are there any safety issues and will it cut down on interference? The point where the circuit ground (from the supply board) meets the chassis will also be a star-ground point for all grounds in the system.


texts: Preserve the input voltage range while reducing part count for a power supply

texts: I have a design which uses a TPS40200 switching regulator that gives out 5V at 2A (max) by accepting input voltages anywhere between 8V to 40V. However, I now need the same 5V at not more than 800mA but the pin count has to reduce significantly. I was thinking of using a 7805 that just needs a input and output capacitor but it can accept input voltages only upto 30V. Is there a way to preserve the input voltage range while reducing the part count? The switching regualtor circuit has a BOM count of 24 and this needs to come down to not more than 5.


texts:
After reading a lot about 3 phase BLDC motors there's one concern that's nowhere to be found.
Let's say that we have a 1000 Kv motor and we want to rewind it to 10 Kv to get unrealistically high torque at low RPM. And let's say that we have the right diameter replacement copper wire.
Will there be saturation from iron or permanent magnets?
This questions is probably very wrong as magnets are passive and will probably not saturate, but I'm really unsure and don't have sufficient knowledge about magnetism, so from my perspective only the iron laminations can saturate from high enough force produced from current circulating around them.


texts:
I currently am using Li-FePO4 cells in the configuration below (picture):

I'm researching how to build a passive cell balancer for this battery pack. Though I'm getting confused on some specs I'm seeing in data sheets; for example in one of TI's spec sheets it says "# Series Cells (Min)". Now I'm not quite sure how I'd answer that. I know I have 2 cells in series X 3, connected in parallel; but not quite sure how to apply that to that spec. (shown in picture below)

How would I answer that?


texts:
I was creating a circuit using two dual input AND gates into a dual input NOR using three modules and module instantiation.

The first module is for the AND inputs and the second module is for the NOR. Both of these modules work correctly and this was verified using waveform simulation and checking the truth tables.

When I try to simulate the third module aoi22.v I get an error on this line
" orInv2 _orInv2_2 ( ._and1(_and1), ._and2(_and2),.f(f) ); " Missing conneciton for port _and1, _and2. When I take out the .f(f) I get an error Missing connection for port f? Any suggestions on how to fix this?

module and22 (input i1,i2,i3,i4, output _and1,_and2);
    assign _and1 = i1 & i2;
    assign _and2 = i3 & i4;
endmodule

module orInv2 (input _and1, _and2, output f);
    assign f = !(_and1 | _and2);
endmodule

module aoi22 ( input i1, i2, i3, i4, output _and1, _and2, f);

    and22 _and22_1 ( .i1(i1), .i2(i2), .i3(i3), .i4(i4) );
    orInv2 _orInv2_2 ( ._and1(_and1), ._and2(_and2),.f(f) );

endmodule


texts:
I have designed a GPS disciplined oscillator.

It's performance is nominal for the design, but the question I presently have is about conditioning the output for presentation to a front panel BNC jack.

At the moment, I have an NB3N551 1-4 fan-out buffer. 1 output of that clocks the controller and the other 3 go through 33 ohm resistors (the output is nominally 20 ohms impedance) to a 6 pin DIP header.

I've used this in a couple ways... I've viewed the output with a 10x scope probe (1M-ohm impedance on the scope input), and I've fed it to another circuit of mine with an AC coupled 50 ohm thevenin termination feeding a schmitt trigger buffer. Those work just fine.

What's not so great is if I look at the output on my scope with a 1x probe. It's not terribly square anymore. I haven't yet tried T-ing a 50 ohm terminator yet, but plan on it later on today (perhaps therefore this question is premature).

Is there a standard output/distribution circuit I should be using instead of or in addition to the NB3N551?

Keep in mind that while I don't really care about propagation delay in this application (as long as it's constant), adding tons of jitter would not be great.


texts:
I'm working on a I/O module to control AC, DC motor and lamps by using relays. But I don't know how to control the relays. Some says I should use optocoupler, some says transistor array.

I found an optocoupler TLP280, in the figure there is the schematic. Can I use it by supplying 3.3V to control 24V dc motor and some lambs.


texts: Filter circuit design for input: pair of positive and negative pulses and output: digital High

texts:
I am working with an IR sensor which gives the following output once the sensor is actuated. The sensor creates a negative pulse followed by a positive pulse. The pulses each are approximately 10 ms wide. These pulses are approximately 1 sec apart. Two pulses constitute one single output event.

I am reading this signal in LabVIEW cDAQ device using an analog voltage input module. My goal is to drive a digital output high in LabVIEW software when the event occurs (at the end of positive pulse). Another way to say is I want to completely ignore all negative going pulses and overshoots and I only want to observe the first positive going pulse. Once observed I want to drive a digital output high in LabVIEW.

I don't have good knowledge in signal processing. My thought is I need to filter out the negative pulse and overshoots. Then I can use filter to detect the positive pulse and drive a digital output high. I want to leverage the signal processing tools in LabVIEW but I don't know how to design filter circuit.

I would appreciate any direction on how to design the circuit with the help of LabVIEW signal processing tools. Thank you so much!


texts: LC filter - how to deal with additional inductor

texts:
In the circuit below we have a positive potential VDD=3.3V and ground potential VSS=0V which are supplying the digital part of an integrated circuit. Digital part of circuit is operating at frequency f=12MHz and can therefore cause some disturbances. Same integrated circuit also has analog part which needs more stable potentials VDDA=3.3V and VSSA=0V derived from previously mentioned potentials by using LC filters.

But this are not ordinary filters because there are always 3 electronic elements added. I haven't found any calculus for example like this that would show, how to derive size of L2 and L3. Does anyone have idea how to derive the equation for L2 and L3 or could at least recommend a good book on the subject?

I tried simulating it with some random values for L2, L3 & L1, but it won't kill the 12MHz frequency entirely so I am lost without theory. I don't know if this is even the response I need to look for...

After applying some changes like @The Photon suggested in the comments I really get better response and frequency is almost flattened out entirely. Not quite there yet, but it is better now. But it looks like it keeps on ringing...

Here is the clocking of my integrated circuit as user @analogsystemsrf requested in the comments:


texts: Phototransistor as a pull-down in digital circuit

texts:
I have very little experience with phototransistors. I'm trying to create a circuit that will effectively function as collision detection. I'm using OPB608A which utilizes an NPN transistor. My goal is to use said transistor to output logical signal to my PIC18F4520. The I/O pin I'm using for this has Schmitt Trigger Buffer - according to the datasheet any input above 0.8VDD (~4V) will be treated as logical high (and 0.2VDD - 1V - will bring it back down).

Having very little experience I am tempted to use the following circuit:

and adjust value of R1 to adjust the sensitivity. My question is: is this a good idea? Won't this cause any problems (such as pretty much shorting the circuit if R1 is low value)? Any better way to handle it?


texts: Multiple I2C slaves on Intel Edison I2C-6 Bus

texts:
I've managed to get my hands on an Edison a few weeks ago and have been messing around with the I2C-6 bus and have encountered a few problems.

Problem
I mainly have sensors on the I2C line. I can place 2 sensors on the line without any problems, however when I add a third sensors to the line, an already attached sensor will become non-respondent as well the newly attached sensor also not responding. I've double checked and there are no address clashes.


texts: ADC is detecting a sine wave as several clusters of points

texts:
I'm using an ADC (ADS4129) running at 125MSPS. I'm applying a 100kHz sine wave to a low pass filter (fc=15MHz). The ADC is being driven differentially, as intended. When probing the input signal with a scope I see a decent sinusoid.
My problem is that looking at the ADC output I get this:

The frequency is right, but the points appear in clusters in specific points. At the moment I'm lacking several of the 10nF decoupling capacitors needed (I'm waiting for them). Could these capacitors be the cause of this problem? It seems strange to me that this appears at specific points.
On the other hand, analysing the input in the frequency domain seems to just indicate poor performance of the ADC, which would make sense without the decoupling needed.

Edit:
The ADC is in a Mezzanine board. I'm using a FPGA to interact with it. The FPGA is expecting a LVDS input signal, and it is converting the the data from the ADC format (DDR, alternating even and odd bits). This was tested in a testbench. The FPGA inputs were contrained according to the ADC setup and hold time, with a margin to account for possible trace length mismatch.
Edit 2:
transition:
0b111000011 451,
0b111111111 511,
0b111000001 449,
0b111111111 511,
0b111111101 509,
0b111111100 508


texts:
I'm designing a high-frequency (\$6\,\text{GHz}\$) mixed-signal PCB. The design contains some noise-sensitive RF analog circuitry (mixer, LNA, 12-bit ADC, etc.) as well as some noisy digital circuitry (e.g. FPGA driven by a \$40\,\text{MHz}\$ clock with \$1\,\text{ns}\$ edges) and several switching converters. The design is small enough (a bit less than 10x10cm) that I'd previously assumed it would be a single PCB design (admittedly, I've never designed a system with more than 1 PCB). Despite the size, I'm beginning to think that this could be better suited to a multi-PCB design. The first benefit is being able to separate the analog and digital circuitry. I can individually shield these PCBs and I expect should be able to reduce the digital noise that creeps into the analog system.

Another benefit of separate PCBs is it makes the system more modular and easier to test. In particular, my current thought is to have 3 separate PCBs for the power supply, digital circuitry and analog circuitry. This would allow me to more easily test the power supply and substitute in different power supplies if I think one is too noisy or sub-optimal in some other way. Or, I could generate dummy data for the digital section, or command the analog section externally. You get the idea.

The final reason I'm intrigued by the multi-PCB system is cost. The RF analog portion requires a significantly more expensive PCB than the rest of the design. I can place the power supply and digital PCBs on cheaper (higher loss) materials and save a substantial amount without (I hope) sacrificing quality. I think the digital section is slow enough that the higher loss and less controlled dielectric permittivity shouldn't matter. Moreover, if I mess up one of the boards the cost of replacing just that portion is lower.

However, there are a number of challenges with the new design. For one, I run the FPGA, the ADC and an RF frequency synthesizer on the same fast edge 40MHz clock. The FPGA would be placed on the digital board whereas the frequency synthesizer and ADC would go on the analog board. If I place the clock on the digital PCB (which was my plan) I would need to ensure the clock signal and its return current have a low inductance path between the digital and analog boards. The same goes for the digital output of the ADC but in the reverse direction. Similarly, there are a few digital control signals that are sent by the digital board to control the analog one. I believe the solution to this is to use the proper board-to-board connectors. I'm not too familiar with these, but considering PCIe exists, there must be a number of varieties that are more than adequate for my use case.

Could this design benefit from being on multiple PCBs for the reasons I provided? Are there other reasons I haven't considered that are either for or against doing this? Any thoughts on the proper board-to-board connector to use for the clock and ADC digital data? All of my voltage and current levels are modest: the full design takes 12V 600mA.

I'm happy to provide more information about this design if it's useful, just let me know.


texts:
The circuit looks like this:

All the elements are known, except for \$I_{g2}\$.
\$E_1=3V,E_4=10V,E_6=2V,E_8=1V,E_9=4V,I_{g7}=1mA,\$
\$R_1=1k\Omega,R_2=1k\Omega,R_3=1k\Omega,R_4=2k\Omega,R_5=4k\Omega,R_6=3k\Omega,R_9=6k\Omega\$
But we also know the current \$I_8=1.3mA.\$
The task is to calculate \$I_{g2}.\$
According to LTSpice software, \$I_{g2}=1mA\$.

What I did:
I transformed the whole circuit into Thevenin equivalent in regards to the branch with \$E_8\$.
It was a long and demanding process, but, in the end, I got \$I_{g2}=11mA\$ which is nothing close to \$1mA\$.
I rechecked everything I did a couple of times, but I just couldn't find the mistake.
I will recheck it a few more times, but I would like you to give me tips and your opinions on solving this, do you have any better ideas?

Edit:

So, here is the detailed procedure of my solution:
1) I redrew the circuit for easier calculations. The picture below shows the circuit for which I found the Thevenin's equivalent.

2) Then, I found the equivalent resistance between \$A\$ and \$B\$ by cancelling all the sources with their internal resistances. The picture below shows the circuit after the cancellation of sources.

Now, I calculated equivalent resistance by replacing \$R_1\$ and \$R_3\$ with \$R_{13}=R_1+R_3=2k\Omega\$. Then I applied delta-wye transformation to convert \$R_4R_5R_{13}\$ into \$R_{45}R_{134}R_{135}\$. After that, everything is obvious. After a few calculations I got: \$R_T=R_e=\frac{10}{3}\Omega\$.

3) For calculating the voltage between \$A\$ and \$B\$ I applied superposition theorem and taken in account one source by one.

a) only \$E_1\$ active:

We can see the bridge is balanced, so \$E_1\$ has no impact on \$U_{AB}\$, so, in this case, \$U_{AB1}=0\$.

b) only \$E_4\$ active:

Using node-voltage analysis, I found that, in this case, \$U_{AB2}=-\frac{20}{3}V\$.

c) only \$E_6\$ active:

Again, using node-voltage analysis, \$U_{AB3}=-\frac{4}{3}V\$.

d) only \$E_9\$ active:

Again, using the same method, we get \$U_{AB4}=-\frac{4}{3}V\$.

e) only \$I_{g7}\$ active:

Using current dividers, I got: \$U_{AB5}=-2V\$.

f) only \$I_{g2}\$ active:

This is the part where I lost so much time, I found this circuit really complicated, but, solved it in the end using the combination of delta-wye transformation of \$R_4R_5R_{69}\$, compensation theorem and node-voltage analysis. Then, from the circuit I got, I calculated currents through \$R_1\$ and \$R_3\$ and then I used compensation theorem (replaced resistor \$R_1\$ with voltage source \$E_1=\frac{51}{84}I_{g2}\$ and resistor \$R_2\$ with voltage source \$E_3=\frac{33}{84}I_{g2}\$). After this, I used node-voltage analysis and in the end got \$U_{AB6}=\frac{4}{3}I_{g2}\$.

Then, I summed up all the voltages and got \$E_T=\frac{4}{3}I_{g2}-\frac{34}{3}\$

Now, finally, the equivalent circuit looks like this:

And, since we know that the current through that circuit is \$I_8=1.3mA\$, we get \$I_{g2}=11mA\$, which is incorrect.
I hope you can find the mistake somewhere.

Thank you for your time.


texts:
I was pointed towards the C18 library, but I'm using a PIC16.

Can I use the C18 library for a PIC16 using the MPLAB X IDE? If not, is there an alternative to this library for the PIC16?


texts:
Disclaimer: I have no formal electronics training.

I am reading this book: Raspberry Pi Zero Cookbook [2017]

Here's the paragraph from that book that's got me confused:

  The Raspberry Pi documentation allows up to 2.5 A for the Pi's
  power supply, in case you don't want to use a powered USB hub. For
  this cookbook, we will start with a powered USB hub but work toward
  low-power and low-profile solutions.

I was under the impression that, from an abundant supply of amps, a device will draw only the amps it needs.  But the first sentence above implies that you should not connect a power source to the Zero board that is more than 2.5 amps.  Can you please set me straight?


texts: Can anyone please identify this 6 pin SMD integrated circuit?

texts:
Can anyone please identify this 6 pin SMD integrated circuit or what it does? I could not find it by the code written on it.

It is from a solar charger and I need to replace it.


texts:
Despite hours of googling, I could not come to clear understanding how efficiency of 5V addressable LEDs compare to their 12V counterparts.

If 5V is supplied to WS2812, and the red LED only needs 2.1V, will the rest 2.9 be dissipated as heat? If not, why?

If 12V is supplied to WS2815, and exactly the same technology red LED needs 2.1V, where does the rest 9.9V disappear? How come it still produces more oomph per watt of power than WS2812?

And in general, how voltage of these LEDs (SMDs with multiple LEDs) affect their efficiency?

WS2812 5V "Neopixel" characteristics:

max current 60mA
max power 0.3W
total brightness around 6.8 lumen per led

~ 113 lumens per amp
~ 22 lumens per watt

voltages of separate components:

red: 2.0-2.2V
green: 3.0-3.2V
blue: 3.2-3.4V

WS2815 12V characteristics (possibly probably something is incorrect because I couldn't find whole lot of info):

max current 15mA
max power 0.18W
total brightness around 5.3 lumen

~ 353 lumens per amp
~ 29 lumens per watt


texts: AVR MCU running @ 32.7Khz Low speed LED multiplexing problem interrupt

texts:
Works fine with internal 8mhz, but when change to 32.7Khz, the multiplexing led display is not working properly (it's flashing very randomly). is this the limit of low clock speed or is there a problem to my code?

Timer0 is for multiplexing the 7-segment display;
timer2 is for an external clock counting.

I also have played around the TCNT0, ie, to increase the multiplexing speed, in the interrupt, but with no luck;

///////////////////////////////////////////////////
// B1, B2, D3, D5, D6, B3, D2, D4 (+) active HIGH
// B0, D7, B5, B4 (-) active LOW
///////////////////////////////////////////////////
#include <avr/io.h>
#include <avr/interrupt.h>

int8_t portA = 0b11011100;
int8_t pinA[8] = {1, 2, 3, 5, 6, 3, 2, 4};

uint8_t counter=0;

int8_t d1 = 0b00000110;
int8_t d2 = 0b01011011;
int8_t d3 = 0b01001111;
int8_t d4 = 0b01100110;

int8_t left=43;
int8_t right=21;

uint16_t one=9995;
uint8_t good;

uint8_t tsec;
uint8_t tmin;
uint8_t thr;

  int8_t dig[] = //digit mapping
    {
    //HGFEDCBA
    0b00111111, // 0
    0b00000110, // 1
    0b01011011, // 2
    0b01001111, // 3
    0b01100110, // 4
    0b01101101, // 5
    0b01111101, // 6
    0b00000111, // 7
    0b01111111, // 8
    0b01101111, // 9
    0b00000000, // BLANK
    0b10000000  }; //dot

//----------------------------------------------------

int main(void) {

    //timer 0
    TIMSK |= (1 << TOIE0);
    TCCR0 |= (1<<CS01); // timer0 No prescaler

    //timer 2

   TIMSK |= (1 << TOIE2);
   TCCR2 |= (1 << CS22) ;   // 64 prescaler
   //TCCR2 |= (1 << CS20) ;  // no prescaler
   //ASSR |= (1<<AS2);
     sei();

    //adc
    ADCSRA |= (1<<ADPS2)|(1<<ADEN)|(1<<ADIE);
    ADMUX |= (1<<REFS0) | (1<<MUX0)| (1<<MUX1);
    ADCSRA |= 1<<ADSC;

    // PORTs
    DDRD = 0xff;
    DDRB = 0xff;

  while (1) {

    if( one>=9999)one=0;

    left=one/100;
    right=one%100;

    d1=dig[left/10];
    d2=dig[left%10];
    d3=dig[right/10];
    d4=dig[right%10];

 if(counter==0){
  PORTB |=0b00110000;
  PORTD |=0b10000000;
     pinWrite(d1);
  PORTB &= ~(1<<0);
  }

 if(counter==1){
  PORTB |=0b00110001;
  PORTD |=0b00000000;
     pinWrite(d2);
  PORTD &= ~(1<<7);
  }

 if(counter==2){
  PORTB |=0b00010001;
  PORTD |=0b10000000;
     pinWrite(d3);
  PORTB &= ~(1<<5);
  }

 if(counter==3){
  PORTB |=0b00100001;
  PORTD |=0b10000000;
     pinWrite(d4);
  PORTB &= ~(1<<4);
  }

  if(counter==4) counter=0;

  }
}

//----------------------------------------------------
ISR (TIMER0_OVF_vect)  // timer0 overflow interrupt
{
   TCNT0=100;
   counter++;

  //19Khz @ 8Mhz/256/2=15Khz
  }
//----------------------------------------------------

  //2hz   @ 32Khz/256/64=2hz
ISR (TIMER2_OVF_vect)
{
  good=!good;
  if(good==1)one++;
}

//----------------------------------------------------
ISR(ADC_vect)    // adc interrupt
{
  //one = ADC;
  ADCSRA |= 1<<ADSC;
}

//----------------------------------------------------
// PortWrite

  int pinWrite ( int8_t data){

    for (int x = 0; x <8; x++) {

      if (data & (1 << x)) {
        if (portA & 1 << x) {
          PORTD |= 1 << pinA[x];
        }
        else {
          PORTB |= 1 << pinA[x];
        }
      }

      else {
        if (portA & 1 << x) {
          PORTD &= ~(1 << pinA[x]);
        }
        else {
          PORTB &= ~(1 << pinA[x]);
        }
      }
    }
}


texts:
I am a rookie in this area so please excuse my language as I don't know all terms.
The solder paste I am using does not either melt or stick and just looks dry when I try to solder a LED onto a MCPCB.
I am using this solder paste (Sn63/Pb37) https://www.mouser.com/datasheet/2/73/TS391AX10-1150148.pdf
I don't have a reflow oven and I am instead using a hotair reworkstation which I tried with different temperatures (150, 180, 210 degrees celcius) and trying to make it "wet" and stick to the to the solder joints.
I also tried heating it up slowly waiting all from 30s to 3 min holding the airgun on different distances. I am getting the same result all the time.
I can see on the product specification that it's called thermally stable (which to me is an unknown term) - is that the fault?
I cleaned the MCPCB as well between tries with chemically pure isopropanol
This is the result every time (pic without LED)

Is the solder paste old? Am I doing something wrong?


texts: How can two steel balls with same amount of charge be at different voltages?

texts:
Maybe this is the most fundamental question, but still it eludes me.

Is it possible for two balls each containing 1 Coulomb of charge be at different voltage levels, say 1V and 2V relative to a common ground?

Analogizing:

Mechanics as Electronics

Let,

Charge's mechanical equivalent is Mass
Voltage's mechanical equivalent is Potential energy
Current's mechanical equivalent is Fall (useful work can be done when a mass falls and also current flows)

In mechanics: For two bodies with same mass to be at different potential energy, all we have to do is vary the height from the ground.

So, what could be the Electrical equivalent of 'Height'?


texts:
I want to know how to calculate the gain of a VCO.  I've looked online and see that there exists a formula

$$K_{VCO} = \dfrac{f_1-f_2}{V_1-V_2}$$

but it would seem that this result would give outrageously high gain values.  For examples, for a VCO operating the MHz region, would it be realistic to see that the VCO gain value be in the range of millions as well? (This assuming that I would believe the control voltage value is in the range of 1-10 volts.

Is there another way I can calculate this value?  It just seems unreasonable to me to get such a huge gain factor.

EDIT/ADD-ON:  As an add-on example, assume I had some data for a VCO, and I used a "curve/equation fit" and the resulting equation is of the form y = mx+b. Is Kvco is this case still equal to 'm'?


texts: Audio Signal Switching Transistor For Shutter Release

texts:
I am a complete novice when it comes to electronics but I am trying to open a transistor when there is audio coming out of my iPod, completing the circuit for my dslr and releasing the shutter.

I have control of the audio so i am outputting a 20hz tone because it has the most voltage somewhere about 1 volt and 5ma AC of course. At the other end my dslr outputs a voltage of 2.7 volts and 0.06ma DC.

I tried this circuit without the capacitor or diode (does the transistor need it?) with a resistor about 2k and a bc548 transistor (only npn one I had) and the signal did trigger a response out of the dslr but it seemed to be interference I guess is coming from the other terminal of the audio line.

Would the capacitor and diode make my circuit work by rectifying the signal and do I need a diode on the other audio source as well.


texts: How is the effective parallel resistance of this resistor network determined?

texts:
I have this circuit:

The effective resistance at the reference node of D4801 is given as
Rb = R4802||(R4805+(R4807||(R4806+R4808+44KOhm))) = 9.129KOhm
I am not able to understand how this formula is arrived.
Shouldn't it be, Rb = R4802||(R4805+((R4806+R4807)||R4808+44KOhm)))
Please tell me how the first Rb is correct and the above is incorrect?
How should we factor or consider the R4806 resistor into this formula? I find it confusing on how to include the R4806 and R4807 into the effective resistance formula.
Any tips on how to find a easy way in these type of circuits?


texts:
I am working on the controller for a product that incorporates a humidity controlled chamber, such chamber is (generally) kept at rh80-95% but, even in normal usage, it is possible and acceptable that the humidity reaches 100% and condensing.

Honeywell HIH sensors, http://sensing.honeywell.com/index.php?ci_id=147072 , look great for the task, however they make a dinstinction between sensor that are suited for up to rh100% and those who are suited for rh100% and condensing.

Seems that the only difference between the two versions is the presence of a little "net" in front of the sensor orifice.
Can I just use (for economical reasons outside the purpose of this question) the "non-condensing" version and protect it with a fine mesh in front of the orifice or the under-the-hood difference between the two is bigger that the physical protection of the sensor??

Thankyou


texts:
What is the effects of replacing signed capacitors with 4uF ones related to Emi Filter performance (Electromagnetic compatibility issues).
We observed that the time with 4uF ones keeps longer (power to circuit) when power-off then 1uF ones but not sure how the emi performance will change.
(By the way, are they by pass capacitors?) Thanks.

Hi,


texts: I have a design in Xilinx system generator which meets maximum frequency of 50MHz (I found this from Timing and Power Analyzer of System generator). However, my FPGA board offers 100MHz clock rate. How could I solve this issue? (is there any way like creating a divided clock which can be assigned to the FPGA clock period of clocking options in system generator token?)


texts: How do you measure apparent power consumption of a transformer (primary coil) with no load on secondary?

texts:
Lets say 120 Volts at 60 Hz with a Transformer across it with 1 Henry as the primary and 1 Henry on the secondary. The secondary has no load and is an open circuit. How would I physically measure the Apparent Power of the primary coil?

Side question, if secondary is shorted, will voltage across the primary head towards zero?


texts: Confusion with signal/source being low or high impedance

texts:
Regarding the following excerpt:

High impedance source gives you more volts and less current
Low impedance source gives you lower voltage but more current

What is meant by low impedance source and high impedance source here?
By "impedance" is it meant the output impedance? If so how is that relates to the source utilizing more power? How to comprehend this by circuit model? I came to this confusion after reading about piezoelectric amplifying techniques.


texts: MOSFET drain current during turn ON time

texts:
In the below picture, once the Vgs is greater than Vth, the current Id starts to increase linearly.
But at the same time, Vds is higher and hence the MOSFET is in saturation region. In saturation region, as per the equation Id=K(Vgs - Vth)^2, the drain current should increase parabolically.
Is my understanding correct or in power mosfets, even during saturation period the drain current increases linearly with respect to gate voltage?


texts: How to measure temperature using a NTC thermistor?

texts: I have a TTC103 NTC thermistor. It has zero-power resistance of 10 kΩ at 25°C and B25/50 value of 4050. How do I use it to measure temperature?


texts:
I made a car tracker (a GPS/LTE module connected to an arduino that communicate to my web server) to log gps positionning data. I’m planning to use this to track my new car in case it gets stolen.

My initial thought would be to hot-wire the tracker to the car’s 12V battery followed by a DC-DC converter to 5V.

For redundancy I was planning to also power the tracker from an 18650 battery in case the thief disconnect the car’s battery.

My issue is that I’d like to use the car’s battery as the primary source of power, then the integrated 18650 battery. Finally the car’s battery would be used to charge the 18650 when needed.

The tracker would be low power usage (eg sending location every 10min, in sleep mode other wise).

What would be the best way of powering such system without draining the car’s battery with multiple DC converters ?


texts: Calculation of a Norton equivalent current

texts:
simulate this circuit – Schematic created using CircuitLab

By calculating the equivalent Norton circuit between a and b, I first calculated \$R_{eq}\$ and after \$i_{eq}\$.

When I calculated \$i_{eq}\$, I short-circuited the terminals a and b, and so the circuit becomes:

simulate this circuit

So \$i_{eq}=-\frac{E}{R_1}\$, but the solution gives \$\frac{E}{R_1}\$. Is it a typo?


texts: nrf24l01+ works on channel 10 but not channel 82?

texts:
Setup is nrf24l01+ with 328p running internal oscillator at 8Mhz.

I have been using it like this for a while with no problems at channel 10, but now want to change to a higher channel such as 82, but it does not work, why ?


texts: Help with digital switching for use with 555 timer

texts: I have a 555 timer set up in astable configuration to output simple audible tones. But instead of having mechanical switches to choose the resistor that ultimately determines the output frequency, I would like to drive this circuit with a microcontroller and I would like a signal on a transistor for example, to control the path taken for the discharge/charging between the capacitor and resistors. I have attached an image of a similar schematic, however, mine is a little varied in that I put the switches in series with the corresponding resistor (so each switch only activates one resistor instead of a cumaltive total). Basically, instead of those switches choosing the resistor of R1 through R9, how can I implement a transistor to control this? To be specific I'm planning on using an ATMEGA 4809 for the signals that will correspond to each tone and choose the resistor, but a general answer for how I should approach the design is appreciated. Thank you.


texts: What is the purpose of R3 on this circuit?

texts: What is the purpose of R3 on the shunt regulator circuit below? I simulated it but even without the R3, the circuit still works:


texts:
I'm testing a LTC490 with a hand-turned encoder.

As I only have one IC, I tried testing only one channel (A).

I wired as follows:

Pin 1 to 5v,
Pin 2 to pin header (to read output voltage with a voltmeter),
Pin 3 to CLK (Encoder A output),
Pin 4 to GND,

Pin 5 to Pin 7,
Pin 6 to Pin 8

The idea was to use the LTC490 to encode the signal, and then feed it back into the IC for decoding. As the frequency is so low, I saw no need to use a terminating resistor, and instead made a direct connection.

It would seem that the LTC490 is providing a path of no resistance between the Vin and GND pins, which caused my 5v power supply to melt, and emit smoke. Can anybody explain what's causing this? I suspect it down to the way in which I've wired it, although I have no idea why.

Datasheet: http://www.farnell.com/datasheets/1691473.pdf

UPDATE:

On closer inspection of the wiring, I realised I was feeding 5v into GND, and 0V into VDD, which I'm going to assume is what caused the short circuit.

Slightly unrelated, but the test schematic includes capacitors and a resistor (Figure. 2 in the datasheet). Can anybody tell me what these are needed for? I've wired as shown, minus the capacitors and resistors, and it seems to work just fine (of course, I'm using a low PPR encoder, turned by hand). Are they to remove AC noise?


texts:
An electrical circuit comprises a resistance R=1.1ohms in series with an inductance L=1.4H (model Ldi/dt+iR=v). Given that the transfer function model linking voltage supply to current is given as Z=a/(s+b), what is b?

I did Laplace tranform and got (1.4s+1.1)i(s)=V(s), therefore, i(s)=V(s)*1/1.4s+1.1.
Since Z=a/s+b, then s+b=1.4s+1.1. I got b to be 0.4s+1.1 but it's wrong. Can anyone explain why?


texts: How to simulate the impedance for this LISN circuit in LTspice?

texts:
I tried to simulate the following simplistic LISN circuit:

Below is the AC analysis with LTspice for two nodes:

But these above plots do not tell me anything related to the purpose of LISN which is impedance balancing. The idea of LISN to raise the grid impedance to around 50 Ohm, isn't it?. How can this circuit be modified so that we can see the impedance settles/stabilizes after a certain frequency? Can someone simulate and obtain that?

Edit:

I might have found the answer after I read the following:

  Since the currents exiting the device under test are dependent on the
  load on the ac power cord, and this load is the impedance seen by the
  device looking into the ac power outlet, which varies considerably
  over the measurement frequency range from outlet to outlet and from
  building to building, it is not sufficient to measure the noise
  currents on the power cord with a current probe. Instead, the product
  under test is connected to a LISN, which stabilizes the impedance seen
  by the product looking out the ac power cord.

So instead, I simulated the Z = Voltage/Current at DUT node:

The impedance seen approaches to 47 Ohm and I increase R2 to infinity it approaches to 50 Ohm.

What do you think? Is this a correct way of demonstrating it?


texts:
I'm looking at controlling some WS2812 5050 RGB LED strips from a microcontroller. I've successfully played with the Adafruit Neopixel library and I've written some code on a PIC18F2455 which I've also gotten working for some simple things (progressively change colour from red, to green to blue, and back etc).

However, all of that was for a single string. Ideally, since I'm using PORTB on the PIC micro, it'd be great to use all 8 bits to drive up to 8 strings from the one chip.

Yes, I know I'm getting greedy here :)

My question is, what approach would you recommend to take given that I have at most the timing involved for sending a 1 or a 0 on any individual channel is a few instruction cycles and the signalling protocol is non-standard 1-wire type protocol so the PIC doesn't have a dedicated peripheral to offload the work to (sending a 1 involves 'write 1, nop, write 0' and sending a 0 involves 'write 1, write 0, nop').

Additionally, there's probably only at most a hundred instruction cycles between the end of one bit at the start of the next before you hit the 50us "end code" and everything you've been writing out gets latched onto the LEDs and the data protocol resets back to waiting for the first bit again.

For a single string I've just been taking the three bytes for Green, Red, and Blue (that's the order these things use) and doing 24 "if (green & 0x80) write1(); else write0();" etc statements. But clearly that exact same approach isn't going to work for 8 bits at once.

Some options I considered:

Computing a byte based on the first bit of the green value, then using carefully crafted assembly to (a) write 0xff to the port, (b) write the computed byte to the port, and then (c) write a 0x00 to the port. Rinse repeat 23 more times for the first LED on each of the 8 strings, then repeat again for however long it takes to output the entire string. Only problem is all that computing takes a fair amount of cycles and it's quite possible to take so long it ends up interfering with your output.
Instead of storing each of the led string data as an array of GRB byte values and then computing them at output time, store them as a "smeared" bit array (eg, first string's LED 1 data is stored across 24bytes of memory in the first bit of each byte, second string's across the second bit of each byte, etc). Advantage is outputting is dead easy and fast, disadvantage is the workload is moved to the creation part of the process and you now need functions to get or set individual values.

Thoughts? Anyone have any reasons why you would or wouldn't do any of the above? Anyone know of any clever hacks to quickly "flip" an array of 8 bytes so byte 1 becomes the first bit of the 8 bytes in the result? :)


texts: I have read that Arduino can be powered by both 12v from dc jack and from USB as it is equipped with FET which takes power from only one input. At the same time I read that many people destroyed their arduino as they were not equipped with FET. How do I know if mine has one? Basically I want to power from 12v and open Serial Monitor on USB.


texts:
I would like to turn off and on a circuit by another circuit. I believe that could be easily achieved by a transistor but when there is a voltage regulator and an ESP8266 with wide range of input current I'm lost.

I have the ESP8266 programmed to send a notification when it's turned on. The V1 supply has unfortunately too low current to power the ESP so I have to power it by the V2 (4xAA 1.5V batteries should be probably enough to feed the voltage regulator 3.3V + 1.1V it's dropout and some transistor dropout)

The circuit below is my amateurish attempt that can be probably all wrong.

simulate this circuit – Schematic created using CircuitLab


texts: Analysis of a MOSFET circuit using node method

texts:
I am trying to learn SCS model for mosfets and I have two questions.
First, when a mosfet is not in saturation and it is turned on, it behaves like a variable resistor and its resistance changes depending on the gate to source voltage. From this, I draw the image below but I am not sure if it is correct. Is it correct ?

Second, how can I analyze the same circuit when the mosfet is in saturation using node method.

I thinks it is (Vout / RL) - ids = 0
where ids = K(Vgs - VT)^2 / 2
But again, I am not sure about this and I think it is incorrect.
(This is my first post in this website so if I made any mistakes I am sorry.)


texts:
I am looking for the best way to add both Bluetooth (LE, central) and ZigBee (Coordinator) to my hardware project.
There were trials to integrate BLE (peripherial) and ZigBee (End Device) into one SoC: CC26x2 and CC13x2 by Texas Instruments. They provided the DMM: https://training.ti.com/dynamic-multi-protocol-manager-overview.
However on multiple forums I have learnt that:

ZB Coordinator needs the medium almost 100%, otherwise network could/will collapse
BLE connection must not be interrupted, otherwise it will fail.

My first priority is the ZB Coordinator, but I sometimes also want to use the BLE (without losing the ZB network).
There are multiple scenarios, but I have no idea which is the most appropriate:

Finding a single SoC that handles this with one antenna.
Putting two SoCs on the board with the same antenna and apply/create a rocksolid synchronization between them
Putting two SoCs on the board with 2 separate antenna placed in good distance (at least λ/4) from each other

All has disadvantages:

first: does not seem there is a SoC existing
second: synchronization seems quite challenging if not impossible
third: ugly and might be totally instable (but putting a ZB Coordinator USB stick to RPi seems working together with its BT)

This might seem insane, but we have at least one common example for co-existing radio technologies on same(ish) frequency: smartphones. If you make a VoIP call with your BT headset, your phone is constantly using its Wifi and Bluetooth at the same time.
Co-existing ZB and BT seems requiring much lower bandwidth, therefore seems a reasonable goal.


texts: Continuous charging and varying load on 48v AGM - Will an ESC work with a battery that is being charged?

texts:
So, in a lightweight IC/electric hybrid motorcycle I am using a small 4-stroke engine to turn a Brushless RC motor (the generator). Then a 3-phase rectifier bridge to supply 59.2v DC @ 12amps to a 48v AGM battery bank continuously. I then intend on having a 200amp 60v ESC (intended for huge scale rc aircraft) controlling the drive motor. Can anyone see any likely problems with my plan??

The engine sits at very precise revs but I'm still considering some sort of overvolt protection if the ESC has none.

Is there a chance of interference from the rectified dc causing problems with the ESC? As I know they are designed for nice clean dc from a battery. Or will the battery act to smooth the dc anyway??


texts: Automotive power filtering, protection - feedback needed

texts:
I'm working on GPS tracker for automotive applications. Device should work in 9V-30V supply voltage range. In practice it will be fed from 12V car installation. This enforces the implementation of some protection/filtering circuit at the power input.

After reading some threads on load dumps, voltage transients, reversed polarity connection I feel a little confused. I'm not sure that design I came up with would stand against those hazards.

I'm also wondering if this could be done with less part count. I'm stuck with fuse selection as well. Should I use glass or PTC in this case.

I would appreciate any feedback on the following circuit.


texts: In the power spectrum of a random process, it's said if the PSD has a delta at the origin then it has a DC value, So is that value always one as it's a delta also how can i calculate the DC and AC power ?, and if i passed that Random process through a channel of specific function, how can i get the output ?


texts: What's the purpose of the T568A/B's color wires?

texts:
I know that pair 3 in T568A is used for transmitting data while pair 2 is used for receiving data. In T568B the logic is reverse, meaning pair 2 is for Tx and pair 3 is for Rx.

What's the purpose of the blue and brown pairs?


texts: PWM drivers of Shift registers that are not open drain?

texts:
I am need of a 16 channel PWM Serial based LED driver, or serial in – parallel out shiftregister. I had been looking at TLC5940 and TLC59025 respectively.

But for my current set up the ouptuts cannot be open drain, the output of each channel needs to be +5v 10mA, to switch a transistor. The TLC5940 approach would probably be better than the soft pwm approach with the TLC59025.

Does anything like this exist? if not what other approach would I take?

The individual LED driver circuits shown below:


texts: Is this ammeter and power reading correct?

texts: Is the ammeter reading 2A and the power absorption 100W or did I calculate this incorrectly?


texts: Op Amp output's noise changes when the gain changes

texts:
I use Arduino DUE to generate a 100 Hz pulse.

I wanted to remove the DC value so I added a high pass filter and this is connected to the Op Amp(ADA4000-1)'s input. A RIGOL's DP832 power supply is giving +/- 9V to the Op Amp.

These are connected to the breadboard and I noticed when I change R2's value.

The following screenshots are the Op Amp's output.

R2 = 0 (Unity gain)

Some noise is discovered from the signal's positive peak.

R2 = 40k, gain = 5

When the gain becomes bigger, reversely, the signal's negative peak shows noise and the flat line after the positive peak seems noisy.

What seems to be the reason for the noise when the gain changes?
Also, what could be the solution to remove these noises?

EDITED: You guys are right; the output was unstable due to the missing decoupling caps.

I changed it to a unity gain buffer.

Before adding the decoupling capacitor to the negative terminal,

the same phenomenon was shown.

As you see my pen pointing, adding 100nF cap,

now it is giving a stable output! Thanks!

Two more things;

When I touch the Op Amp's output with my finger, I discovered that the output becomes stable (by looking at the oscilloscope) without the decoupling capacitor. Why did this happen?
This happened due to the unpopulated decoupling capacitor. Is there a name/technical jargon of this phenomenon?


texts: Help ID maker of huge film cap, 50mm x 35mm x 24mm -- AD 256K 250V MP

texts:
I just pulled this thing from a large board, I think it's part of an inverter.
The board also has a huge CM choke, 8 IRF260N and other fets.  No manufacter shown.  This thing was part of the input filter it looks like, there are two screw terminals for the input.

Here is a picture.  The "256 250V MP" plus the makers logo are the only markings.  Size is 50 x 35 x 24 mm.

I've spent more than 30 mins doing the Google thing, looking at more than 10 pages of various logos.  Did I somehow miss it, or was it a rare company?
Who made this??

Ok, I know it's a 25uF 250V metalized paper capacitor, I would like to find out who made it.  I have seen none this big with this small a value.

[![US penny for scale1: https://i.stack.imgur.com/2NZFF.jpg


texts:
We've got some products that use 27C256 EPROMS.

The guy who wrote the original programs (many years ago) is gone and we'd like to make changes and write some new programs for some new products and keep it in-house.

We've got the burner and all that, so that's not an issue.

My question is very basic, how do you write an EPROM program?
Machine language? C? Is it specific to the burner we use?

All we've got is the compiled version of the existing programs, so no help there reverse engineering it to see the original format.
I've searched online, but can't find any specifics on how to actually write a program from scratch.


texts: Correct Initialization Routine for LCD Panel (HX8357D)

texts:
I have acquired a color 320x480 TFT LCD display based on a HX8357D driver.  It is an Adafruit 3.5" Touchpanel display.  I would like to use it for one of my projects based on Rust.  Currently, there are no drivers out there for Rust and therefore I plan to pull one together by altering existing drivers to work (likely target is the st7735-lcd-rs driver).

One of the things that I will need for this is the correct initialization sequence.  I have looked at the datasheet for the display (datasheet) and struggled to find a good definitive list of necessary commands to properly initialize the display.  Is this just a poorly written datasheet or am I just looking in the wrong place?

There are some drivers out there for the display such as the Linux Kernel (Which is driver variant agnostic and looks a bit dated, so not sure if it is valid for the D variant) and AdaFruit's own library (see line 183 where it defines the initd array.  I consider this to be the most authoritative source for the init routine sans the datasheet which is the subject of this post).

These could of course provide me with the necessary routine.  However, I would like to find this information from the datasheet.  It is very likely that I just do not know how to parse these datasheets as this is the first time I have tried to do this type of thing.  How do I get this information from the datasheet?  Thanks for any pointers.


texts: Decoupling and bulk capacitor number and value

texts:
I am currently finishing a circuit with TIVA C TM4C123G where the user manual indicate the following:

"decoupling capacitor typically 0.1uF in value and should be accompanied by a bulk capacitor. The combined VDD and VDDA bulk capacitance of the microcontroller is typically between 2uF and 22uF" "For optimal performance, locate one decoupling capacitor adjacent to each VDD power and ground pin par. At a minimum there should be one decoupling capactiro on each side of the microcontroller package connected betxeen VDD and Ground"

1./ Looking at the launchpad board TMC123G and other board EVM, the number of  decoupling capacitor and bulk capacitor are not respecting  those indication. So, how to know how many capacitor and of which value I should put (particularly for the bulk) ?

2./ What can happen if I put too many decoupling capacitor on one pin

3./What can happen if I put too many bulk capacitor on one pin ?

I am a bit lost here , sorry if my question look stupid

Launchpad guide reference: http://www.ti.com/lit/ug/spmu296/spmu296.pdf
DK guide: http://www.ti.com/lit/ds/spms375e/spms375e.pdf
Chip guide: http://www.ti.com/lit/an/spma059/spma059.pdf

I don't understand because in the chip they say some decoupling capacitor should be placed on each side of the mcu, but on the LQFP144 package there are several VDD +GNd pair... so i am supposed to put decoupling capacitor and bulk capacitor on all ?


texts:
I'm working on something where i need to display 20 independent 2-digit numbers that are located in different places. In current prototype there are 20 extruded in plastic numbers with led backlight. The drawback for my application is that I cannot change the order of numbers. I can live with that, but dynamic numbers would be cool and would enable some other useful features.

Long story short, while I was going to sleep last night I thought "woah, I can probably use some displays". Well, after some thinking it became obvious that 7-segment displays would require enormous amount of pins or expensive driver ICs. Also, my application is in very limited space. So, could someone help me out and give an advice how to implement this? Or prove that it's too stupid. I know that it sounds like an absurd idea, I just want to be sure. Thanks.


texts: How do I change and select which Polygon thermal relief Altium Designer 19 shall use?

texts:
How can I make a polygon in a Signal layer in Altium Desginer 19, to change its copper thermal relief?

I've created a rule for it, or so I think.

But I have not been able to find where I select which rule the Polygon shall follow.
In my case I want the blue marked areas to be filled, without thermal relief.


texts: Found a part on an old FM transmitter used for tuning. What is it?

texts: This is an old transmitter from the early nineties. The part is the white block with the screw through it.  I'm assuming it's a capacitor of some sort, but other than that I don't know much.  I don't have a meter to test capacitance with, which is why I'm asking for help identifying it.  Furthermore, if the part can be identified, is there something I could replace it with to make more minute adjustments to the broadcast frequency?


texts:
I disassembled my old Niko RC car today. Thought I could play around with the parts.

But what I can't seem to understand is the coil. The powersource of the rc car is a 7.2v NiCd 620mAh battery. And as you all see (image 1) I've tried to connect it directly on the coil - nothing happens.

As I know nothing about electronics I thought I might test with a 9v also (image 2) :-).

But still nothing happens. Does anyone know what's wrong? I did some simple measurements with a multimeter before disassembling and the coil got -3.3v / 0v / 3.3v depending on what it was doing. This coil is controlling the rc car so its voltages for left / center / right.


texts: Finding the resistivity of high resistivity liquids

texts:
I'm working on a project to determine the resistivity of 1,1,1,2-Tetrafluoroethane
which is estimated to be around 10^14 ohm-cm. The problem is, the most sensitive commercial conductivity sensors for liquids available only measure up to 10^10 ohm-cm. So I looked into transformer oils where a paper states the resistivity of Tetrachloroethylene to be 5.6 x 10^14 ohm-cm at 20C. I've been trying to find out how these other high resistivity liquids had their resistivities determined but can't find anything online. Was wondering if anyone here knows anything, I feel like i'm missing something like i'm overestimating how difficult this is. Would really appreciate the help, thank you.


texts: High voltage high frequency transformer driving

texts:
As I want to build SMPS circuit to produce high voltage output (about 4 kV). I was trying to build a circuit like this (not 555 but a 12V square wave to drive IGBT's gate). What I need to design is an arc producer about 4 kV (10 mA max) AC output from a DC supply of 300 V.

I was searching for solutions and I saw this topic. There was a term that says "resetting the flux".

What is the difference between these circuits. I am asking this because my circuit also won't swing between negative voltages to change flux direction. Do I need an H-bridge driver to drive this type of circuit?
Is there another topology that I can use? Can I use an ignition coil to do this?


texts: Sign of current through a voltage source

texts:
simulate this circuit – Schematic created using CircuitLab

I am a total newbie to circuits, so please forgive my naivety. My question is the following:

When I simulate the above circuit in LTspice, the current across the voltage source is shown to be negative (-.05). That means in this case they mark the current coming out of the the positive terminal of the battery as negative. Is that just a convention or is there some logic behind it? If it's a convention, is that the general standard?


texts: How to know UART DMA TX is finished for RS485 enable process in STM32F4 CubeMX

texts:
I am using STM32F4 series MCU with STM32CubeMX enviroment. I can send and receive data without problem in RS232 physical layer.

My problem is that when I use with it in RS-485 physical layer, I should know when transmission process is finished, last bit is sent from shift register and I am ready to terminate transmit function and enable receive function of RS-485 chip.

What is the flag convention of UART_Busy_Flag or related flag with this process.


texts:
I want to basically embed an FTDI cable in my board to avoid confusion with the RX/TX pins, wrong cable, etc.

I really want to make sure I choose the direction correctly though.  I have UART_TXO OUT of the micro and UART_RXI INTO the micro.  How should these be connected to the FT232R?  I'm having trouble really nailing down the direction of each pin.  Currently, I have:

Also the FT232R requires no programming, correct?


texts: Physical push-down toggle button that pops up on voltage

texts:
I have encountered innumerable variations to functionally identical 2-lead physical switches, like the push-to-toggle buttons I am currently working with. Manually depressing the button toggles between two alternate states, popped up and pressed down, each of which physically separates and bring into contact the conductors, respectively.

Does there exist a widely-available 3-lead variation of the described switch that physically pops the switch up when the trigger lead is supplied current, and what it it called?


texts: Low Frequency Response of BJT amplifier(effect of bypass capacitor)

texts:
Doubt related to impedance seen by the bypass capacitor:

or

What is the impedance seen by the bypass capacitor \$C_E\$

To calculate the impedance as seen by \$C_E\$, we attach a Thevenin volatge source as shown.

Applying Kirchoff's current law:

$$ \frac{V_T}{\beta r_e+R_S||R1||R_2}-\beta I_B+\frac{V_T}{R_E}=I_T$$
$$\frac{V_T}{\beta r_e+R_S||R1||R_2}+\beta \frac{V_T}{\beta r_e+R_S||R1||R_2} +\frac{V_T}{R_E}=I_T$$
$$V_T[\frac{(1+\beta)}{\beta r_e+R_S||R_1||R_2}+\frac{1}{R_E}]=I_T$$
$$V_T[\frac{1}{\beta r_e+R_S||R1||R_2}+\frac{1}{r_e+\frac{R_S||R_1||R_2}{\beta}}+\frac{1}{R_E}]=I_T$$

From here I get the resistance as
$$\frac{1}{R_e}=\frac{1}{\beta r_e+R_S||R1||R_2}+\frac{1}{r_e+\frac{R_S||R_1||R_2}{\beta}}+\frac{1}{R_E}$$

However in book, the resistance has been given as:

$$R_e=R_E||(\frac{R_s||R1||R2}{\beta}+r_e)$$

It seems the first term in \$\frac{1}{R_e}\$ vanishes!
Where might have I gone wrong?

(I have referred to the following text book: Electronic Devices and Circuit Theory, by Boylestad and Nashelsky.)


texts: no distortion amp circuit, max. (d(Vout)/dt )max< slew rate, why not (d(Vin)/dt)max?

texts:
I think slew rate is how fast a circuit can react to a given input. I was asked to find the frequency limit where the output would show no distortion and tried to find it by (d(Vin)/dt)max < slew rate. But my answer wasn't correct because (d(Vout)/dt)max < slew rate, is what I needed to calculate.
It still doesn't make sense for me to analyse the rate of change of the output if you look at the definition of slew rate I gave.


texts: Finding a Fourier series of a Burst Fired sine wave having consecutive 2 cycles on & 2 cycles off?

texts:
I have been trying to find the solution of the following problem but with no luck.

I have a system that generates a waveform of sinusoidal type with the only difference being that this wave has 2 cycles on, 2 cycles off, 2 cycles on and so on...

Here is a picture of wave,

The x-axis is time. Each cycle is 20 ms or 50 Hz. After two ON cycles, there are two OFF cycles.

I want to find out the harmonic content of this waveform through Fourier analysis. But I don't have any idea where to start. I am confused with the time period. For example, I have to find a0, for that we have this,

Now I am confused with what should be T and what shout be I (t). I computed it with T = 8*Pi. and i(t) = sin(wt). But I couldn't get answers. Because I don't know what limits should be applied to the integrals.

Please help me on this one or direct me to the source where I can find the answer. My goal is to find the Fourier series of this function and I already have an idea that this wave contains Sub-harmonics and Inter-Harmonics.

Edit (In case you're wondering why do I want this):

This actually is a test waveform in one of the IEC standards to test harmonics immunity of electronics devices. According to the standard, this waveform is supposed to contain Sub-Harmonics and Inter-Harmonics.

This is the spectrum of this wave according to the standard (IEC 62053-21).

I want to find out how this spectrum is achieved through Fourier series. This test also mentions some other waveform like half-wave rectified, 90-degree phase fired sine wave, etc. I did the Fourier analysis for these and I could clearly achieve the results (Harmonics Contents spectrum) same as Standards.

Though I can't seem to reach the results for this specified case (2 cycles ON, 2 Cycles OFF).

Any help is highly appreciated.

Thank you.


texts: Why does the input resistance of an inverting op-amp amplifier have to be high?

texts:
According to Sedra & Smith's microelectronics textbook, in order to avoid a loss of signal strength, voltage amplifiers are required to have a high input resistance, which I agree with. However, in case of the inverting op-amp, why does \$R_1\$ also have to be high? I don't understand why a voltage divider is necessary in this case, considering an ideal op-amp has infinite impedance in its input and all the current is going to go through \$R_2\$ anyways. From my understanding, what we want is for \$R_1\$ to be low, since that's what's going to result in a high \$v_o\$ given that \$v_o = -\frac{R_2}{R_1} v_I \$.

For reference, I'm referring to the text in section 2.2.3 of Sedra & Smith's 7th edition of "Microelectronic Circuits".


texts: Receiving image through USB to embedded device via USB CDC

texts:
I am trying to send images through the USB port to my stm32f7 eval board. I have taken pictures from webcam and send it by the code below

    import time
    import NumPy
    import cv2
    import serial

    vid = cv2.VideoCapture(0)
    vid.set(cv2.CAP_PROP_FRAME_WIDTH, 320)
    vid.set(cv2.CAP_PROP_FRAME_HEIGHT, 240)

    ser = serial.Serial(
    port='COM8',
    baudrate=921600,
    parity=serial.PARITY_ODD,
    stopbits=serial.STOPBITS_ONE
    )

    #encode_param = [int(cv2.IMWRITE_JPEG_QUALITY), 90]
    #result, encoded_img = cv2.imencode('.jpg', frame, encode_param)

    while True:
    ret, frame = vid.read()
    gray_img = cv2.cvtColor( frame, cv2.COLOR_BGR2GRAY )
    flattened_img = numpy.ndarray.flatten( gray_img )
    ser.write(data=flattened_img)
    time.sleep(0.1)
    if cv2.waitKey(1) & 0xFF == ord('Q'):
    break

It is better for me to take images in grayscale and bitmapped.
I think this part is not causing the problem, but I only get 64 bytes each time according to the debugger

debugger section

I still could not figure out what is wrong with the embedded side. USB Full Speed can work at 12Mbits/s but I can't even receive an image, what can I do to receive images fully?
This is the project link -> https://github.com/Emreiris/Personal_Embedded_Software_Projects/tree/master/Project


texts: I'm connecting to an arduino or raspberry pi and would like to have 256 io pins. I found a 16bit io expander which has 8 unique addresses for 128 but that's the max I can do on i2c. Any other thoughts on how to expand my io ports?


texts: Can movement be constrained to an Axis in Kicad Footprint editor?

texts:
In many CAD tools there is usually a hotkey or modifier to constrain movement to an axis, or 30/56/60/90 degree angles.

Is there a key to constrain movement in this way in the KiCad footprint editor?
My use case is to move the Footprint courtyard clear of the pins for a component.


texts:
We are going be buying a 15 HP motor, and using a VFD we have, currently not doing anything. While I'm told that typically, you buy a VFD for the Motor (i.e. 15 HP Motor + 15 HP VFD), we couldn't let the Mitsubishi VFD continue to collect dust.

That being said, could a 15 HP power motor be used with a 30 kW VFD (Mitsubishi FR-F740-00620-EC) without harming either unit?

Search on Google and Stack Exchange regarding running a low power on a high power VFD has yielded no results, so here I am asking.

While I can't imagine it being an issue (my thoughts are VFD is just a power supply deal), we figured it wouldn't hurt to be safe and check.


texts:
I'm working on a project that requires both 5v and 3.3v rails. It will usually be powered from 2xAA batteries, but the user will occasionally use USB to set parameters and perform firmware updates. I want the circuit to be powered from USB when USB is attached and from 2xAA when USB is not attached. Total current draw will be < 250ma at all times. I've come up with this circuit:

The MAX1797 will boost the battery voltage to 5V. The MAX1837 will convert the 5V to 3.3V. The MAX1797 will accept input voltages from 1 to 5.5v. The voltage drop across the SS2 diodes should be < .5v with the planned current draw. This will give around ~4.5v on the input of the 1797 when powered from VBUS and around ~2v when powered from the batteries. Is it appropriate to use schottky diodes this way? Would using a MOSFET switch be a better solution? Also the Maxim devices are quite expensive!! Are there less expensive devices that will do the job?

update:

After much thought and research and after implementing the suggestions above this is where I am.

Please understand that I'm a noob at this sort of thing. I may be totally wrong. But here is my thinking:

During normal operation, without USB, current should flow through the P-MOSFET and power the circuit. The voltage divider on LBI sets a shutdown voltage of ~1.6V. When the voltage on LBI is above 1.6v, LBO is open-drain and sinks current to ground, holding SHDN low. When the voltage drops below 1.6v, LBO goes high impedance and SHDN goes high. This shuts down the MAX1797. When USB is attached,  the MOSFET disconnects the battery causing the voltage at LBI to go to zero and causing SHDN to go high. During shutdown, OUT becomes a high impedance node allowing VBUS to be connected directly to the 5v rail without fear of 'back pressure' on the 1797.

I changed the output capacitor to 10µF to help reduce the inrush current from VBUS. Is 10µF low enough? Is it sufficient for a 250ma load?

A few more questions:

Do I have the MOSFET orientation correct? I'm not completely clear on the body diode. What would be a good choice for this device? Do I need a current limiting resistor on the gate?

Will this work?


texts: DFPlayer Module Sleep mode working for anyone?

texts:
I'm trying to put a DFPlayer module into sleep mode.
The command seems to be: 7E FF 06 0A 00 00 00 FE F1 EF. The normal power consumption my supply is showing (when the module is idle) is about 15mA, after sending the sleep command I read exactly the same. Sending the command another time will get an error (0x40).

Anyone observed similar behavior?


texts: Common mode choke selection for 5V 1A smps power supply

texts:
I am designing a flyback smps power supply circuit and having trouble deciding the exact common mode choke that I should use. My power supply specs are as follows:
Input - 80-270 VAC 50/60 Hz
Output - 5 VDC 1 A
I found a similar circuit but different output voltage/current:

This schematic uses 2x27 mH cmc.
On digikey these are the parameters -
inductance @ frequency
current rating - Is 100 mA enough?
DC resistance -
voltage rating -
What values should I choose? Smaller component is preferred.


texts: How to execute firmware from external flash memory interface to PIC microcontroller?

texts:
I have both PIC18 and PIC24 microcontrollers with 256KiB of flash memory.

My code size is 400kB and cannot be stored in the flash memory of those MCUs anymore. So I'm thinking about using external flash memory to hold the program code.

Can I store my executable file in the external flash and execute it from there? How do I do that?


texts: How to electrically shift the phase of a signal?

texts: Let's say I have a sine wave and I would like to shift it by varying degrees, like 90, 180, and 270. How would I do this?


texts: First step in pulsing a pulsed laser diode

texts:
here is the datasheet for the laser im looking at https://dammedia.osram.info/media/resource/hires/osram-dam-2496525/SPL%20LL90_3.pdf
All i want to know is where i even start, i see the input voltage is only 20v and it can pulse at < 30ns so with this information where do i start? I learned how a to make a CW laser driver circuit for any laser and i know this is a lot more difficult, but any help will be much appreciated.


texts: Can we apply a longer pulse to latching solenoid than its rating?

texts:
I've a 6-12V dc latching solenoid, which needs 60ms of pulse to set it to on/off.

I'll be using a microcontroller to generate the pulse. I've following questions.

What if the generated pulse is longer (say 10x of the specified 60 ms) Will it damage solenoid? Will it still correctly turn on/off.?
I was thinking of using pwm(pulse wave modulation) technique to generate pulse. So I was thinking of using 60% duty cycle for time period of 100ms. Then after sleeping for 100ms, I would disable pwm. So there is always potential of two pulses instead of one, (or more) going out. Am I thinking on correct lines?

Adding specifications:


texts: alternative values of these resistor in circuit?

texts:
i am working on a spectrum analyzer, concept is to feed audio signal to esp32 and perform FFT at 40000hz sampling rate. I tried MIC input but did not get satisfied by results.

link to diagram
I found this diagram on WLED GitHub page but problem is i don't have 680ohm resistors right now which alternative value should I use? and what is purpose of these resistors here. I am using laptop as audio source. The input voltage range for esp-32 ADC is from 0 to 1.1 V.


texts: How can i calculate Vs in this circuit knowing Vo=2?

texts:
I know that using Ohm Law i can calculate the I  of the 2k resistance:
I  = V/R <=> I= 1*10^(-3)<=> I = 1mA

But i dont know what to do after , i've tried using Kirchhoff voltage law and the voltage divider formula but i cant get it right.
(Supposedely from my appointments the answer is 24V but i dont know how to get there, thanks for any help).


texts: Operating limit of K-type thermocouple probes

texts:
I was looking to purchase a K-type thermocouple and noticed something peculiar. Wikipedia says it can withstand temperatures up to +1350 °C, but Amazon sells some K-type thermocouples that only go up to 200 °C, 250 °C, or 400 °C. What going on here?

What would happen if I tried to measure 400 °C with one that is advertised to only go up to 200 °C? Is it the insulation? Could I replace the insulation to get a wider range? Is it the build quality?

For example, what's the difference between:

http://www.amazon.com/Amico-Thermocouple-Thermometer-Sensor-Probe/dp/B00843IP20 (up to 200)

and

http://www.amazon.com/Type-Thermocouple-Wire-Digital-Thermometer/dp/B005CG2W3U/ (up to 250)?


texts:
Is there a way for converting 1 Gbps analog signal to digital, using 250 Mbps sample rated chips?

If you share your ideas, i will be happy.


texts:
I want to use PIC12F675 to control a relay such that when a switch is pressed, it should generate an output signal which should be ON for 2 seconds and then OFF for 15 seconds.

This should continue when the switch is pressed

When the switch is released, the output should be off.

I've done a program using loops, but the problem is even though it generates an output signal which is ON for 2s and OFF for 15s, however if i release the switch and suddenly press the switch again the loop is still continue for 1 full cycle.

Say for example after 2s, I've released the switch and pressed it again suddenly, the previous loop still goes on executing and will only take the new switching condition after the 15s (second delay).

Here is the program:

#include <xc.h>
#define sw GP2
#define out GP0
#define _XTAL_FREQ 4000000

void main()
{
    ANSEL = 0x40;
    TRISIO = 0b00000100;
    GPIO = 0x00 ;
    WPU = 0x00;

    if (!sw)
    {
        out = 1;
        __delay_ms(2000);
        out = 0;
        __delay_ms(5000);
    }
}


texts:
I want to know how much current a 16x2 (1602) LCD draws when the backlight is OFF and ON?

NB: My multimeter is broken.