texts: NTC Project (Wheatstone Bridge + Instrumentation Amplifier) - Stuck!

texts:
I've been lurking through these forums for years but just now had the urge to ask for help.

I'm creating a thermometer (using an NTC thermistor) for my college project. I began to analyze my sensor in terms of its linearity, temperature range, etc (specifications in general) ... For this project, I decided to use a temperature range from 55ºC to 150ºC (celsius).

Afterwards, I implemented my sensor in a wheatstone bridge. In order to do so, I defined my lowest temperature (55ºC) resistance value (2989 Ohms) and my highest temperature (150ºC) resistance value (182.6 Ohms). I proceeded to find the value of the other 3 resistances so I could end up with a [0 ---- 5] voltage at the end of my bridge (beeing 0V to 182.6 Ohms and 5V to 2989).

My biggest problem now is implementing an I.A.:

My current wheatstone bridge voltage ranges from -13mV to 5.05V which is fine (tho I'm currently designing a gain = 2x I.A. and I'll then throw it back to my voltage range by using a summing amplifier in order to reduce circuit's noise). Thing is, I'm not able to have 2x my bridge's voltage at the end of my I.A. (even tough I'm following the I.A. equation in order to find it's gain).

As you can see, I simply defined the same value for every resistance besides the middle one (this should mean that (1+(2*Any-other-resistance / Rmiddle)) * (V+ - V-) = 2(V+ - V-), which should define a voltage range of [-0,0026 ---- 10,1]V).

Note: I'm using TL084's to build my I.A. (tho I'm testing some other components like TL082 or LM324)

There's a picture attached as I know I messed up explaining this. Any help would be appreciated. I'm really stuck and I have no idea what's the problem (also thought it might be balancing the bridge or having high voltage on my op amps but atm I'm just throwing possibilities into the air without any thinking).


texts: Connecting a microcontroller to the PC via USB

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I'm developing a circuit on a breadboard and using PIC18F4550 microntroller (supports USB connection) but I just wonder how I can connect it to the PC.
Should I get a type A to type A cable, cut it from one side and connect the internal wires (D+ and D-) to the microcontroller?
Or is there a specific connector for that purpose? I got a male type A USB connector but looks like it can only be used with PCBs.


texts: I need to find a housing connector for an LED

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I am trying to find a connector for an RGB LED (Mfg P/N: LZ1-10R102-0000). I don't want to solder wires onto the board because I want to gift it to my grandparent for easy assembly and change if LED destroyed. Please Suggest me any plugable connector (just like house hold bulb connectors).
Thank you.


texts: IC power consumption under 50% vs 100% busload

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Is the dynamic power consumption difference significant for a uC,
 if it has to raise its activity on the chosen bus protocol from, lets say 50% to 100%?

I look in overall to the uC+CommController+Transceiver consumption.

Is this a mostly a general rule, or there are exceptions?

Post edit:

For an exemplary calculation, I would say the following setup:

Infineon Tricore TX family MCU (tx29)
TJA 1081B Flexray Transceiver OR TJA 1145 CAN FD transceiver
100-120 ohm impedance ensured in physical layer


texts: Buck Converter Switching Pin and Voltage Output

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By using rohm's BD9G341AEFJ-LB buck switching regulator, we want to take 5V. In datasheet BD9G341AEFJ-LB's datasheet
the example circuit given like

But we had to try circuit that is in Image-2, because of component absencity. Before trying this circuit we simulated at PSPice and it worked well except of some current ripple.

When we powered circuit in real it gives us 24V at output despite Vin 24V, too. First question, despite we tried PSPice and worked problemless, why did we take this 24V? Does it components value?
And we tried to measure the LX pin with oscilloscope in ac coupling mode. The screen of oscilloscope is (Forgive me I haven't better oscilloscope)
In dc coupling mode already oscilloscope gives us 24V DC. Second question, Is voltage ripple normal? And at the datasheet example circuit, by setting RT resistance to 47k ohm frequency can set 200kHz, that is, if we look to oscilloscope screen, should frequency equal to 200kHz? Or Is frequency is equal to 200kHz?
Last situation as of 05 August
According to last comments and ROHM technical service, I made these:
I found closest components values as possible like in  adviced circuit in the datasheet(Image-1) . At the end, I obtained circuit that in below and results.

And layout like that:

When I supplied VCC with 24V, there was a fluctuating in LX pin between 0 to 1 V during first 20 seconds . And then abruptly I saw 24V at output. Before soldering all components, I controlled again the board and there wasnt any short circuit or different situation.
According to ROHM technical service, when I said this situation to them. They wanted me remove schottky barrier diodes one lead if you use RB095B-90. But why this problem occurs, they didnt tell. Im waiting a response,again. I will inform in here.


texts: Measuring forward and reverse current on a photodiode

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I'm in need of a different perspective here on how to approach the circuit I'm designing.  Currently I have a PD that I want to reverse bias with 2V and measure the current from the PD.  This is easy enough to do using a TIA IC like OPA380.  I can even easily apply voltage to the INPUT+ to reverse bias the PD.

Unfortunately, this would only work for measuring the current in this condition. I don't think I can forward bias the PD and measure the current using this.  One thought I had is to use 2 analog MUX ICs to just swap the PD polarity around.  I think that will work since the current direction is still the same and I don't have to worry about voltage being negative.

Why am I measuring PD in a forward voltage mode?  Well, I'm actually doing an IV characterization of the PD and trying to plot a current vs. voltage curve going from -1 Bias to +1 Bias on the PD.  The design I have now would require having to measure from 0 to +1 twice to get my data (switching the polarity at 0V).

Are there other more elegant ways to measure the PD reverse and forward biased using the same TIA?


texts: Is it possible to over-power a 3-Phase AC motor with a AC Controller?

texts:
If I have a 200kw motor controller, and a 30kw motor, is it possible to overpower the motor with the controller? My application is for an electric vehicle (golf car, small bicycle, and so on).

I'm certain this answer would be self-explanatory if my understanding of VFD's and 3-phase power was more understood. To me, it would seem that if went 'full throttle' or full-demanded torque for the controller, that it would send too much current to the (uncooled) motor and burn it up. This then, begs me to ask the question "what if the load is very, very high on the same motor/controller application, wouldn't the demanded torque from the controller cause the current to the motor to increase beyond the rated limits of the motor?"

Thank you in advance! :)


texts: I am looking for a IC with mininum 6 channel PWM output and preferably USB support so that I can control it uing a software. Any ideas ?


texts: Should the reset pin on MCP23S17 go to a GPIO?

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Most example schematics for Arduino, Raspberry Pi etc have the reset pin tied to GND.

If number of GPIOs on the MCU wasn't a problem, would it be beneficial to have the reset of the expander connected to a MCU GPIO with a pull down resistor?


texts:
I have designed a operational amplifier in Lt spice as shown in the 1st image. I changed the name of the BJT models as I wanted to change the beta value.
2nd image shows the symbol of the op amp
3rd image shows another schematic where I am testing the op amp. When I try to run it, it gives an error as shown in the 4th image.
I have watched many videos and tried many solutions I found on the internet but nothing works. Can someone advise?
Thank you


texts: Confusion in cut-off frequency of LTI System

texts:
Why cut-off frequency  is at (in figure given below) the frequency where $$|M(j\omega)|=0.707=1/√2(D.C gain)$$
But isn't cut-off frequency  according to its definition should be at frequency where $$ |M(j\omega)|= 1/√2(|Mr(j\omega)| )$$ as 3db from from peak determine the cutoff frequency?


texts: Wiring case fans in parallel to a USB cable with an inline switch, still spins slowly

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I have 2 separate projects one is a case for a Raspberry Pi 3b+ as NAS server and the other is a media cabinet.
The NAS kit has 4 30mm 2-wire fans (5V 180mA) and a wired in USB cable that is plugged into a 5V 2A USB wall adapter and a 2 pin switch rated up to 16A. 3 power cables, 1 for fans, one for RPi, one for Power Hub for drives. I get the fans to spin but slower than the specifications. The other project is 5 120mm (12V 250mA) with a 12V 2A wall adapter, again more than enough.
I have not tested the second project but want to have an answer just in case. There is plenty of current and the voltages are correct for the components.
I am just not sure as to why there is such a notable drop in speed or if there is a way to increase the current without another lead to run a transistor.
Here are the links to the components:
Project #1:

    30 mm Fans

    USB adapter

    Switch

Project #2

    120mm Fans

    Power Supply

Edit:
To clarify, only the fans are plugged in to usb wall adapter for project one, the RPi and the hub have their own power supplies.


texts: Sandisk micro sd card not detected. How to diagnose the problem without knowledge about the sd card protocol?

texts:
Seems to be a common problem with Sandisk micro sd cards.

Just a little before or after the warrenty period, the micro sd card suddently stop to be recognized. I mean phones and external card reader complains no sd card is inserted at all when put inside them (nothing is detected).

Of course, before going to find a logic analyser maybe some ata commands which can be launched from a computer might be useful (but I don t know which ones).


texts: Which MCU (Atmel) I can use with QTouch library?

texts: Some MCU have QTouch support - # touch channels implemented as a hardware. Is it true that QTouch library was designed only to work with such MCUs? Can I use it with, for example, 'old' ATmega48? Is it only a software solution which can be ported to any AVR microcontroller despite of hardware QTouch support?


texts: Transferring different signals at the same time via rf

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I am thinking about a device which is able to receive data from my computer (how, is currently not of interest for this question), and then transmit it via rf to multiple receivers. The receivers should obtain the signal approximately at the same time (approximately: several microseconds delay are acceptable, several tens rather not, if possible). The challenging part is that the data for the receiver is not identical, each of them should get different data. Data is a soundfile, length ~5 minutes.
What is the best way to transfer the data, if the receivers should be as cheap and small as possible? Should I rather operate at different frequencies, or multiplex the data, and the receiver have to find their own signal? Which ICs are suited best for that application?


texts: Fullsize HDMI vs microHDMI, electrical considerations

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I'm going to use an HDMI cable in an industrial setting to connect a screen to a Raspberry Pi. We are considering using the Pi 4 instead of the Pi 3 which we have been using earlier. The Pi 4 has switched from the fullsize HDMI connector used in the Pi 3 to a microHDMI connector.

My questions is then if there are any noteworthy electrical differences or concerns when comparing fullsize HDMI and microHDMI? Does microHDMI generate more EMI for example?

Thanks in advance!


texts: Altium short circuit error at x=0 mm, y=0 mm. Don't know why

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I have found 824 short circuit errors at [x=0 mm] [y=0 mm]. I think they came from I copy/paste polygons. But I don't know to solve them.

I have checked there is nothing selectable at this original point. It's strange. Any idea on them?


texts:
USB type-c has alternate mode now. DP, MHL, Thunderbolt, and HDMI signals could be transfered over USB Type C cable directly.
My question: is it possible to transfer SATA signal (preferrably 6 Gbps 3.0) over USB Type-C cable? The main concern is the impedance matching for high speed signals.
The USB Type C specification seems to allow developers to define their own alt mode. I had seen some examples from TI's documents. So this is probably not an issue.


texts: Why does a Colpitts oscillator oscillate at a particular frequency?

texts:
The feedback network used in the Colpitts oscillator is an LC circuit is shown below.

I understand that the phase difference between the terminals 1 and 3 is 180 degrees.
Also the amplifier output is fed at terminal 1 and voltage at terminal 3 is fed back to the
amplifier.
In that case won't the feedback signal will always be in phase with the input of an inverting amplifier?
Then why does the Colpitts oscillator oscillate only at one frequency?


texts:
How the does hardware designer determined the suitable frequency of the clock for his device to work on? After which he created the timing diagram which is then further used for interfacing.

All I need to know what is the mechanism for determining the suitable clock and then creating the timing diagrams. My own logic is first designer creates the device such as Microprocessor then give it different instructions and then check the results on different clock rates but this is hit and trial method is there any specific algorithm to do that?


texts: Digital operation on a microcontroller or FPGA

texts:
I have a simple question about logic propagation in an MCU or FPGA within a single clock cycle.

Let's say that we want to multiply two numbers. Multiplication ends within a single clock cycle on most MCUs, but it takes more than one logic stage to perform the multiplication. By "logic stage" I mean operations that cannot be performed in parallel, but rather recursively.

The question: is there another clock within the "multiplication circuitry", derived from the main CPU clock via PLL or something similar, that triggers these logic stages, or everything works continuously. In other words, does the "multiplication circuitry" behave like one system that needs some time to settle, and this settling happens within a single clock cycle?


texts: How to place "Power On" indicator lights?

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I'm working on a replacement board for an old system. I have two terminal blocks.

Terminal Block 1 (left) is the input from the power supply to the board. This is the primary power supply to the board and rest of the circuit. Pin1 = +, Pin2= -, Pin3 = -.
Terminal Block 2 (right) is the input from the battery and charger. Battery
Charger datasheet The battery system is to come into use if the power from the factory was to go out. Pin1 = +, Pin2= -, Pin3 = -.

Here's my schematic I'm working on at the moment.

Is this the correct way to add indicator lights to the inputs? I want to be able to tell when the board is receiving power (INPUT) from the power supply and when the Battery is in use. I'm pretty sure that the Battery LED (BATT) is going to be on all the time since it's being powered from the input. Is there a way to single this out?

I was going to initially put the resistor and LED in line with the "+" trace on both circuits, but I don't know if that's would effect the charging circuit on Terminal 2.

D1 is to protect against backwards connection to the power supply. Can I place one at the same location for the battery supply? Will this effect the recharging ability?

Edit: "Truth Table"

INPUT LED - On when Terminal 1 is supplying power (IE outside system, such as a factory main line, is able to provide power). Off when outside system is loses power.
BATT LED - On when the battery is used to power the system (IE power from Terminal 1 is no longer being supplied and the system needs to run off a battery). Preferably off when Terminal 1 is in use.

Edit 2 - Full Circuit


texts: Is there a way to get more PWMs from Arduino Board?

texts:
I want to control 4 steppers with Arduino UNO and I'm all short of PWMs.In every tutorial over the web they have used PWM pin , in that case I can at-most use only two steppers with Arduino.So why it has to be PWM only that is to be used or is there a way I can extend PWMs on my board either with software or hardware ?
for example : We use softwareserial library to get Rx, Tx pins .

Here are some of the tutorials :

http://learn.adafruit.com/adafruit-arduino-lesson-16-stepper-motors/stepper-motors

http://arduino.cc/en/Tutorial/MotorKnob


texts:
I know there is a similar question but it did not solve my doubts, I will be clear and concise.

I recently bought the SIM800L module and then I started to try it, at the beginning it restarted itself and I realized it was due to voltage problems. After this I decided to make my own voltage regulator, using an LM317T and some other components. This worked well and placed the voltage in 4v, this way the module stopped re-starting if it was not used with a SIM but if you put one the voltage went up and down and the module was reset logically since its voltage parameters were exceeded. My question is what can I do to have a stable voltage? And if this will be my problem?

I made a video to show the problem, from minute 2:30 I put the SIM.

This is the regulator diagram:

Thanks in advance!

P.D: The battery provides the required amperage, that is if the regulator can not affect it.


texts: Digital isolator says it is bidirectional but its block diagram does not follow that statement

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I am wondering if ADUM1285CRZ is Bidirectional or unidirectional digital isolator. It says it is Bidirectional, but the block diagram says otherwise.

Tha datasheet block diagram shows one direction isolators.
As far as i know, when a digital isolator is bidirectional, internally it functions like this:

Image from: https://www.analog.com/en/analog-dialogue/articles/digital-isolation-solutions-to-design-problems.html
So its functional diagram should be similar (aka for each channel, a dual FR transmitter/receiver).


texts: Reduce 32 amps generator output to 10 amps

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First you need to please understand that I am a truck driver, I lift heavy things and have a smaller brain pan than you good readers. Aka; not an intellectual that understands elictrickery.

While on the road 2,000 km from home for an extended period, the wife needed a generator for back-up power to our home during a particularly stormy season. She bought one that is a petroleum fuelled 12 kVA large enough to run all household and sheddy items - with the 12 kVA thingy detail. However, she is as un-smart as me and purchased a 32 A 2nd-handgenerator instead of 10 A (which is what Australian households are).

So without pointing fingies at her further, my question is:

Can a 32 A generator be converted to output 10 A somehow or do I just scrap the generator in the back of the shed and source another one?

Have a nice day, thanks for reading.


texts: Intuitively, why does voltage drop across a series circuit?

texts:
I'm having a really rough time intuitively grasping the basics of electricity.

Taking into account that current is constant across a series circuit

Using water flow analogy, suppose we have a piston that’s pushing water molecules through a constricted pipe at a rate of 3 molecules passing through the pipe per second with a constant voltage or “pressure” of 5V.
(values are for illustration purposes only)

We notice before, during, and after the constriction, the current is the same.

So if the current coming out of the first constriction into the second constriction is the same as the current going into the first and the resistance is the same across both constrictions, why would the pressure be divided among the resistors equally rather than the two resistors having the same pressure, how does this make any sense?

I understand Ohms Law and how the math works out but I’m asking intuitively why would voltage divide in this case rather than be equal across the “constrictions.”


texts: The percentage of utilization for the single level mux implementation

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Is the percentage of utilization equal to 100% here? If so, can I calculate the utilization like this?

$$\frac 4 4 \cdot 100 = 100%$$

Also, I have to sketch a 2-level MUX implementation based on 2-1 multiplexers (74157 devices). Is my sketch right?


texts: Ammeter and controlled sources in different subcircuits in LTspice

texts: Is it possible in LTspice to control a current dependant current source by the current readen by an ammeter (voltage source set to 0) in a different subcircuit? I've been struggling with this for a while, but I can't find a solution. Subcircuits are hierarchical blocks. CCCS and ammeter are placed in different subcircuits.


texts: Understanding Electric Distribution Pole Anatomy

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Can you please take a look at these two overhead distribution pole images (US and Canada) and let me know what are the 1,2,3, and 4 wires in each images?
Can you also let me know what is main difference between these two?
Image A - US

Image B - Canada


texts: How to connect a two-seven segment displays to an I2C chip on simulide

texts: I am trying to create an AC control unit where I need to change the display of one seven segment precisely. I tried connecting the I2CToParallel chip to the Arduino-UNO board but I can't find the address of the 7 segment so that I can send data to one of the 7 segments precisely.


texts: How to plot input reflection coefficient in dB scale using Matlab

texts:
So I have a problem that asks to plot the input reflection coefficient of a transformer in dB scale between 0.5 GHz and 4 GHz using Matlab. Here is the code I have thus far, it is plotting in Reflection Coefficient (y-axis) vs Frequency (x-axis). I'm not sure how to convert it to the dB scale.

f0 = 1e9;             %% Defining operational frequency
c  = 3e8;             %% Defining speed of light constant
f = [0:0.01:4]*1e9;   %% Defining frequency scale
lambda = c./f;        %% Defining wavelength equation
lambda_0 = c/f0;      %% Defining wavelength equation
ZL = 120;             %% Defining input impedance
Z0 = 60;              %% Defining characteristic impedance
Z0p = sqrt(ZL*Z0);    %% Defining transformer impedance equation
beta = 2*pi./lambda;  %% Defining phase constant equation
ell = lambda_0/4;     %% Defining quarter wavelength euqation

t = tan(beta.*ell);   %% Defining time equation

Zin = Z0p * (ZL+j*Z0p.*t)./(Z0p+j*ZL.*t); %% Defining input impedance equation
gamma = (Zin-Z0)./(Zin+Z0);               %% Defining reflection loss equation
agamma = abs(gamma);                      %% Defining abs value of rl

plot(f/1e9,agamma,'b','linewidth',2);     %% Defining plot
xlabel('frequency (GHz)');                %% Defining x-axis label
ylabel('|\Gamma|');                       %% Defining y-axis label
grid on;                                  %% Grid on


texts: 3.5 male to IR Transmitter - Receiver [amplified] back to 3.5 female

texts:
Trying to recreate a DIY headphone with IR transmitter and receiver

I already searched this is what I have found so far:
1.- http://www.instructables.com/id/DIY-Infrared-transmitter-for-iPhone-iPod/ [For only the transmitter]
2.- Connecting Headphone Jack to Amplifier Help [For the troubles I might have amplifying the signal]
Based on [https://www.youtube.com/watch?v=DtCwJU6YMaA] if you don't want to check the whole video, basically some buddy is using 3.5 connected to a laser beaming through a photovoltaic panel which is connected to an amplifier and streaming music by this method with enough quality at half a mile distance.

The problem, basically is: I can do the same, connect 3.5 to IR LED and a LED IR receiver listening it, so I plug the headphones as wireless DIY headphones but i need to amplify it. Do you think I can mix 1 and 2 projects, and that little amplifier on the second link, is suitable to be feed by a AA or AAA battery so I can make this portable?


texts:
I'm replacing a blender's circuit breaker.
750W -Blender
Current breaker is rated at 2.8A ~230V
So the maximum power output is 640W

But the blender itself is rated at 750W.
So the lower rated breaker would mean the blender would never reach 750W.

Is this done to help with heat dissipation?
How would it affect the blender if I went with a 3.x A ~230V breaker instead of a 2.8A breaker?


texts: How can I rename a Sheet in Altium Designer?

texts:
I'm trying to rename a schematic sheet file inside Altium Designer 14 (in Project Panel).

The only way I can do it is renaming the sheet file in Windows Explorer and relink the file to the project. This is very time consuming and unproductive.

I found no way to do it directly in Altium. I tried the context menu, F2 shortcut and the File menu with no success.

Does someone knows if it can be done directly in the program? And how to do it?


texts: How to exit from this view mode in Altium!

texts: There are so many shortcut keys in Altium. I entered this view mode without noticing what keys I stroked, just can't exit from this view mode :(.


texts:
I have an Arduino Digital Out pin connected to a 1k resistor, then connected the base of a 2N3904 transitor. In fact, that same digital out is connected to several resistor->base-of-2n3904. Each transistor is in turn driving a p-channel mosfet.

I would like to add a pushbutton to override the digital out. By that, I mean that the digital out is most of the time OFF, but sometimes ON from a brief moment. Pressing the pushbutton will have the same effect as turning ON the digital out.

I don't think I can simply add a momentary pushbutton between the digital out and +5V, can I ? This will probably feed 5V directly into the output pin. Should I maybe add a resistor in series with the pushbutton ? do I risk frying the pin by adding the pushbutton like so:

simulate this circuit – Schematic created using CircuitLab


texts: Control a stepper motor with a 3-phase controller

texts:
Is it possible to run a stepper motor with a closed loop 3-phase controller? What i have seen is, that some people short A- with B-, so that it is tranformed into a 2 coil 3 phase system. So i tried this myself with a field oriented control inverter with absolute position sensing, but I had no success yet. If this is possible, what would be the number of pole pairs for a normal 1.8°/step stepper motor?

This is what I found here (http://ijcsiet.com/pdf/01082014-026.pdf):


texts: Explaining the positive and negative regions of the output waveform in a circuit involving a Zener diode

texts:
I am trying to find the explanation for the output waveform at Vo of the circuit below:

The output voltage is as follows:

Perhaps the explanation why the form is as such during the + cycle is because only approximately 7.5 volts is available after the current went across R2, and the Zener diode needs 5 volts to activate. Hence, only about +2.5 volts appeared on the positive region of the output waveform.
I am quite unsure for justifying the appearance of the negative region. I think the current went through the R3 first. The output voltage, thus, decreased to more or less -5 volts. Am I correct?


texts: Discrete lamp dimmer circuit: how to choose component values?

texts:
As you can see, the VAR is 500K Ohms, the capacitor is 100nF. (AC voltage = 220V, freq = 50Hz)

I already built this circuit and it works perfectly. Can anyone show me how those values were chosen? Can I use other values, like the VAR = 50K, the cap = some value?


texts: Is it necessary to remove ground on all layers when using isolated DIO

texts:
So, I am using uptocouplers and digital isolators for a project connected to a microcontroller GPIO. I removed the ground (ground plane cutouts) under the load side of the components, is it necessary to do this on all 4 layers or just on the toplayer where the components are located?
I do have vias carrying the load-side signals near the components, that's why I cut away all ground. Is this correct?
The PCB is meant as a control hub for an AGV with a nominal working voltage of 48VDC (battery supplied, 55V charger supplied, during deceleration or braking up to 100V). The loads controlled are various contactors, detectors and a motor brake input.


texts:
I'm using the MCP2021A for my project. In this component, there is a voltage regulator but I have no use for it. They usually power microcontroller like the PIC18F2455 but I'm using a Raspberry Pi which consumes too much current.
If I don't use this regulator, I have no output on my LIN BUS.
Can someone explain to me how it works so I can find a solution ?
Schematic:

I just connected pin 3 of IC (MCP2021A) to an unused Arduino so I can have VREG_OK which I don't have if it's floating.


texts: PIC32 UART Communication Wrong Characters

texts:
I am fairly new to PIC32 and am attempting to set up a very basic UART transmission to my computer through a DB9 connector. I am using a PIC32MX440F256H as my testing board. I have gotten the data to transmit, but the characters do not appear the same in the serial monitor (Tera Term). My assumption is the baud rate is not right, but I have attempted different fixes to no avail. I would appreciate any possible help in fixing this. An example output is sending 'A' returns a 0 on TeraTerm , and other characters appear as seemingly random characters on the TeraTerm. The code is as follows:
Main.c
#include "xc.h"
#include "p32xxxx.h"
#include "MX440F256H.h"
#include "UART.h"

void led1_on() {
    LATGbits.LATG6 = 0; //LED1 pin HIGH
}

void led1_off() {
    LATGbits.LATG6 = 1; //LED1 pin LOW
}

void led2_on() {
    LATDbits.LATD1 = 0; //LED2 pin HIGH
}

void led2_off() {
    LATDbits.LATD1 = 1; //LED2 pin LOW
}

void delay() {
    int i;
    for (i = 0; i < 250000; i += 1);
}

int main() {
    UART_Start();
    TRISDbits.TRISD1 = 0;
    TRISGbits.TRISG6 = 0;   //Setting LED pins to output

    while (1) {
        delay();
        led1_off();
        led2_on();
        delay();
        led1_on();
        led2_off();
        UART_Send("a",1);
    }

    return 0;
}

MX440F256H.c
#include "MX440F256H.h"

#pragma config FWDTEN   = OFF    // Turn off watchdog timer
#pragma config FNOSC    = FRCPLL // Select 8 MHz internal Fast RC (FRC) oscillator with PLL
#pragma config FPLLIDIV = DIV_2  // Divide PLL input (FRC) to get into required range 4MHz
#pragma config FPLLMUL  = MUL_20 // PLL Multiplier
#pragma config FPLLODIV = DIV_1  // PLL Output Divider
#pragma config FPBDIV   = DIV_2  // Peripheral Clock divisor
// 8/2*20/1/1= 80 MHz

UART.c
#include "xc.h"
#include "p32xxxx.h"
#include "MX440F256H.h"

int sysClk = 80000000;
int pbClk;
char test;

void UART_Start(){
    pbClk = sysClk/2;
    U1MODE = 0;
    U1STA = 0;

    U1BRG = pbClk/(16*115200)-1;

    U1STAbits.URXEN = 1;
    U1STAbits.UTXEN = 1;
    U1MODEbits.PDSEL = 0;
    U1MODEbits.STSEL = 0;
    U1MODEbits.ON = 1;
    U1MODEbits.BRGH = 0;
    U1MODEbits.ABAUD = 0;

}

void UART_Send(const unsigned char *data, unsigned int nBytes)
{
    unsigned int i;

    for(i = 0;i < nBytes;i++)
    {
        while(U1STAbits.UTXBF);
        U1TXREG = data[i];
    }
}
```


texts: Why don't three-phase transformers use toroidal cores?

texts:
When looking at different transformer core designs, three phased, I never see any core designed as a circle or torus.

Why is that so? Will it not work as well as the common B-shaped core?


texts: BMS won't output voltage despite good LiPo Cells

texts:
I have an 20 cell LiPo battery pack that is healthy at 80V in total, the BMS uses 12 MOSFETs in parallel to switch the negative terminal and they all seem healthy but won't switch on, so I can't get a voltage from the terminals, only from before the BMS at 0V and the positive terminal. I have two of these battery packs, they're e-scooter batteries, and all that was done to break them was opening the external casing to count the cells originally, although now the BMS's have been disconnected and inspected.
I don't know if this is:

that the MOSFETs are broken, although I've measured their resistance across source-drain and they're all open circuit when unpowered, I'd love to know if there's a better way to test them if there's a way?
or if the circuit controlling the MOSFET gates isnt sending a signal anymore. I can't measure the voltage at the gate when the BMS is attached to the battery because there's physically no space. Is there a common component that breaks and stops this gate voltage signal to the MOSFETs?
do you know how an electrical engineer is supposed to go about diagnosing a circuit like this in general?

Any advice or thoughts would be appreciated, thank you.


texts: Load sensing relay/power switch/adapter which switches on when it detects some load on its input

texts:
Complete newbie here. I'm not using the right terms, so my apologies in advance.

The problem is simple. I want my powered computer speakers (2.1) to turn off when the computer is turned off. I have the same problem with my TV - it is connected to another set of powered (5.1) speakers. Right now I leave both speakers (computer/TV) always powered on, which wastes energy.

How can I create a "load sensing relay" which would monitor the power draw of the computer or the TV and if it goes above some threshold, to switch on the power line to the speakers? I'm sure that such thing already exists, but I don't know its name or how to find and buy it or to wire it myself.

I tried with a traditional relay, which was supposed to be driven from a computer/TV's USB port and when it is on, it would switch on the device connected to it. But this didn't work as both computer and TV's USB ports are always powered, even when the devices themselves are powered off.

That's why I want to monitor the power draw from the "input" device (computer/TV) and activate the relay if it goes above some threshhold (as the computer/TV draw some small amount of current even when turned off).


texts: Are there smaller packages for Standard rcl (resistor, inductance, capacitor) than 0402mm

texts: I need to miniaturize a PCB as much as possible. Are there packages available on mouser for standard components like resistors (100k) or inductance (Up to 30nH) or Cap (Up to 100pF)?


texts: How can I edit a pre existing component in Altium design?

texts:
There are some simple component in Altium Desing like LED or Diod or Resistors but How can we edit or modify them because its schematic and pins are good , I want to add a 3D object or some text or lines to it , but I don't know how?

It is easy for component file which could be found in internet because they are a simple file which adds to your project but the altium component are part of a bigger library like miscellaneous devices.

PS : By modifying, I don't mean to double clicking on theme and change some properties , I mean editing their schematics and PCB layout.


texts: Is this output normal for a capacitor filter?

texts:
I have a question regarding oscillator outputs and capacitor filters.

I'm trying to build a voltage regulator. I've already calculated and tested the transformer and rectifier, and also the filter part. But when I looked at the output waves from the oscilloscope, the output is straight. Like this:

From the photos I have seen online:

The output waves are very different, is this a normal output from the filter? Take note though that I have a very high value for the farads.

The equation I used to solve this is:
C = (Iload  /  2) * frequency * Vpp
where Iload = 1 A, f = 1Hz, Vpp = 1V

The result is 0.5F or 500000uF.

Is it an acceptable output from the capacitor filter?

Here is my schematic so far:


texts:
I need help with the following AC circuit problem:

Given the circuit (attachment 1) with known data:
$$\underline{Z_3}=200(3-j4)\Omega$$ $$\underline{Z_4}=100(3+j20)\Omega$$ $$\underline{Z_5}=100(3+j4)\Omega$$ $$\underline{Z}=100(2+j5)\Omega$$ $$\underline{I_{g2}}=-10(2-j)mA$$

After the switch is closed, the increment of voltage 1-2 is given: $$\Delta \underline{U_{12}}=(4+j3)V.$$

Find the complex apparent power of $$\underline{I_{g2}}$$ after the switch is closed.

Attempt:

By using current compensation theorem on the branch with the switch and impedance Z we get the following circuit (attachment 2 - switch and impedance Z are replaced by Ic):

In the case when switch is open, compensation current Ic is equal to zero, and in the case when the switch is closed, it has some unknown value.

By using superposition theorem,  we can analyze the circuit from attachment 2 by looking at Ic and other generators are removed.
Now, we get the following circuit (attachment 3):

From this circuit, we know potentials of nodes 1 and 2 since $$\Delta \underline{U_{12}}=\underline{V_1}-\underline{V_2},$$ so we can use potential of nodes method to find the complex value of Ic and the voltage U23. By setting the potential V2 to zero, and after solving the system of two linear complex equations with V3 and Ic as unknowns, we get:

$$\underline{V_2}=0$$ $$\underline{V_1}=(4+j3)V$$ $$\underline{V_3}=(12.48+j53.4)V$$ $$\underline{I_c}=(-6.44-j41.57)mA$$ $$\underline{U_{23}}=(-12.48-j53.4)V$$

Complex apparent power of Ig2 (attachment 1) after the switch is closed can be found by the following equation:

$$\underline{S_{I_{g2}}}^{(c)}=\underline{U_{35}}^{(c)}\cdot \underline{I_{g2}}^{*}$$

where $$\underline{U_{35}}^{(c)}$$ is the voltage across Ig2 when the switch is closed, and $$\underline{I_{g2}}^{*}$$ is the complex conjugate of Ig2.

We can find the voltage $$\underline{U_{35}}^{(c)}$$ from the following equation:
$$\underline{U_{35}}^{(c)}=\underline{U_{35}}^{(o)}+\Delta \underline{U_{35}}$$

where $$\underline{U_{35}}^{(o)}$$ is the voltage across Ig2 when the switch is opened, and $$\Delta \underline{U_{35}}$$ is the voltage across Ic from the attachment 3 and is equal to $$\Delta \underline{U_{35}}=(-12.48-j53.4)V$$ (look at attachment 3).

In order to find the voltage $$\underline{U_{35}}^{(o)},$$ we look at the circuit from attachment 1, where only the generator Ic is removed.

Question: Since the following parameters are not given: $$\underline{I_{g1}},\underline{Z_1},\underline{E_2},\underline{E_6},\underline{Z_2},$$ how to find the voltage $$\underline{U_{35}}^{(o)}?$$

Is there another method to find the complex apparent power of Ig2 after the switch is closed?


texts: I have been on this for about two days now and I'm so frustrated already I don't know what I'm not getting right. I want to be able to use the stm link utility with my stm32f103c8t6 so that I can use the print function in the mcu. I have the stm link v2 mini, and I know that the SWO pin on the board is responsible for send debugging data out of the mcu, what I want to know now is which pin on the stm link v2 mini will I have to connect the SWO to? Pls any idea will be so much appreciated.


texts: 5 Band resistors and correct orientation

texts:
few days ago i bought few (about 500) resistors and i noticed that they have 5 color bands instead of 4. My question is how do i count them (which color is the tollerence) and how should i put them? Do they have a good or bad orientation like + or - ?
I tried to use an online calculator but i dont know the first and the last band.


texts: Need a cheap embedded linux board that has WiFi access point and USB2.0

texts:
I need a small embedded Linux board that has the following:

On board WiFi access point
USB 2.0 high-speed HOST.
Under $100, preferably under $70 or around $50

Basically I need to send real-time video or multimedia data/files received at the USB HOST, over the WiFi access point very fast.

I saw this one board that seems be a good one, MiniEMBWiFi

http://robosavvy.com/store/advanced_search_result.php?keywords=miniembwifi

I'm in USA, but that board seems to be in the UK, dont know if UK Wifi will work in USA??

Anybody knows of any other Linux boards out there that can fill these requirements?

Thanks


texts: 4 to 16 decoder made by two 3 to 8 decoders not working properly

texts:
I have a function f(x,y,z,w)=x.y.z+ y’.z’+x’.w’ and I need to make a circuit using two 3 to 8 decoders, an inverter, an or gate with as many inputs as we want (I use two because I need a 9 input one and on DEEDS I found up to 8) and up to 16 and gates (???). So far I've made this circuit based on the fact that f= Σ(0,1,2,4,6,8,9,14,15).

I don't seem to figure out where the AND gates go. Also, this circuit is not working properly as it returns 0 when y and z are 1 which, by the truth table returns 1. I provide the truth table below.

Why is this happening? Aren't the outputs of the decoders the minterms of the function? (e.g. D0= x'y'z'w')
Also, any suggestion about the AND gates and the solution? No need for the full solution just some help to guide me.


texts:
This is the circuit diagram for a Line Commutated Inverter which I came across in my power electronics book.

The input and output voltage waveforms are give below:

My logic says that from π to 2π, the thyristors T1 and T2
must be reverse biased due to the -ve half cycle of input AC voltage. But it can be seen from the waveforms that this is not the case. Please explain how T1 and T2 are conducting from π to 2π.


texts:
Please, can someone explain me how the transistors here reduce the voltage from +40 VDC to +15V in the positive side (upper part of circuit)

These are the voltages observed across different components of the power supply card.

O/P Positive side : + 15.40
O/P Negative side : - 13.79

R1   0.525 VDC           R2     0.445 VDC
C1   44.6                C2    44.8
R3   14.40               R6    18.16
R4    9.57               R5    12.05
C3   29.40               C4    26.94
ZD1   5.08               ZD2    5.20
R9   10.28               R10    8.48
R11   9.70               R14    7.89
R12   5.65               R13    5.82
R7    4.71               R8     0.536

There is a striking difference between voltage drops across R7 & R8 which are current limiting resistors. Is R7 responcible for TR1 heating up ?

And which is causing difference of O/P voltages on both sides ?


texts: I am using the transformer (a ballast), and its specfication sheet could be found here ballast specification. But on the data sheet, it doesn't says where we need to ground it. Usually, we would ground the transfomer on its outside case. However, since the data sheet doesn't say this, should I still ground it? I would perhaps connect a ground wire to the aluminum plate on the figures below. Would this work?


texts:
(Sorry this is a tad long, but I've marked the questions in bold!)

So I found these 14-segment alphanumeric LEDs online and wanted to control 16 of them using a TI microcontroller. Each alphanumeric LED has 15 pins, 1 for each segment and then one for the dot at the bottom right. If I wanted to power each one directly, I'd need 240 GPIO pins. Not ideal (and not possible).

My next idea was to control each individual LED square using two 8-bit SIPO shift registers. The thing is, I'd need 2 of these for every single LED square, meaning I'd have to use 32 in total. Again, not ideal.

My final idea was to use only two 8-bit SIPO shift registers, but "redirect" the collective 16-bit output to an individual square using some sort of circuit. I know decoders are one-to-many, but they only send one bit out. I need a circuit that sends 16-bit data. I'm thinking this involves combining a ton of decoders, like this chip which has two 1-to-4 decoders in it. This seems really inefficient though. What sort of circuit would I need for this type of redirect?

Also, my problem is that each square will only be lit 1/16 of the time, so they'll be 1/16 as bright. I could pass 16 times the current, but that just sounds like a bad idea... How do I make sure the LEDs are operating at their brightest?

Also, is there a way to have the LED's "persist" using some sort of memory? If the values of the square don't change, then I don't see why I need to keep cycling through them. Would a gated D-latch do the trick?

Please let me know if I'm going about this all wrong. This is my first time trying something this complex, and I'm a bit lost at the moment.


texts: Why do you have to use a voltage divider with HC-05 bluetooth module? (Arduino)

texts:
simulate this circuit – Schematic created using CircuitLab

I am trying to connect my bluetooth module to my Arduino but it takes 3.3 volts (the bluetooth module HC-05, The Arduino mega takes 5v) and the tutorials online say to connect the RX pin to the Ground with a voltage divider.

With a Arduino mega instead but it's still the same thing.

heres the Tutorial i'm following:
https://www.youtube.com/watch?v=hyME1osgr7s

i'm not sure how it works but i don't understand because if i'v learned anything by playing around with electronics it would be that you should never connect positive voltage to GND. I mean it's not connecting 5v to GND but it seems like a bad idea i'm not sure. If someone could explain this that would be quite helpful. Could i just use a resistor from the RX from the Arduino to the HC-05, to make it 3.3v? Is RX and TX considered Positive voltage?


texts: How can I power a cellular phone for a week with a car battery or other type of battery?

texts:
I am about to start construction of a new house, and unfortunately the property is not near where I live.  I wanted to keep an eye on the construction site (No electricity) to make sure workers are showing up. To do so I want to put a cellular phone in a bird house, which will transmit a video from the camera over the cellular signal. (The Android/iPhone app is called "Alfred") My only problem is, how do I keep my cellular phone powered for 7 to 14 days without charging?

I would GREATLY appreciate any help anyone can give. I think the best option would be to connect a 6 or 12 volt motorcycle  or car battery to the phone, but what do I need to consider other than converting the voltage from 6V or 12V to 3.7V? How do I convert from 12V to 3.7V? The screen on the phone will be off the whole time.  All I will be running is the camera, and data transmition.

Does it make a difference if I connect the external battery directly to the phone so the phone thinks it is the internal battery versus connecting the external (6 or 12v) battery to the phone via its USB connector which the phone would think is a charger?

Solar won't work because of tree coverage. My other thought was breaking open laptop batteries and using the cells. I would like the least expensive and a simple way of doing it. Can I just connect a cigarette lighter USB plug to a car battery directly and plug the phone into the USB?

Thank you in advance for any help anyone can give.


texts: When a battery is your power source, what is ground?

texts: For the sake of not incorrectly connecting my power supply and damaging my board I'm going to ask a relatively dumb question. Is ground on my board the negative terminal on my battery? Explicitly should I connect the ground to the negative terminal of the battery?


texts: Eagle- multisized capactor connection issue

texts:
im quite new to Eagle and currently ran into a problem with the multi-sized capacitor package in eagle. The board layout is shown below.

as you can see pin two and pin 3 should in theory be connected, however there is simply no way for me to make this connection, in the schematics the symbol looks like an ordinary capacitor with 2 connections

I tried to use the invoke command as the internet has suggested but that gives me an error 'Part only has 1 gate :c4'. I tried to edit the package itself but the package is from the default eagle library rcl and i cant seem to edit the packages from there. the part name is C025_050-025X075 from rcl if that helps. Many thanks!


texts: I'm looking for a frequency to voltage converter IC that can operate with an input frequency of around 500 kHz. The device does not have to be high-precision and the operating voltage can be anything. I would be looking for a target price of less than $3.00 each in quantities of 100. I haven't been able to find anything. Thank you.


texts:
I am starting to plan a project that involves either an Arduino or Raspberry Pi (haven't decided yet) connected to a number of sensors. The unit will be located outside, battery powered and will send data to a base station located in the house.

I've found a number of different wifi modules that I can connect to Arduino/RPi such as this one, however I'd like to get a bit of an idea of the what sort of range I can expect from the unit.

I understand that there are a number of different variables: whether the transmission is line of sight, the dB gain of the antenna used, etc. However I'd like to get a bit of a ballpark idea of what kind of range I'd expect from units such as the one linked above.

Does anyone know how I can determine this?


texts: Run a servo Nimh battery vs Alcaline batteries?

texts:
I was now about to power a microcontroller (3.3V) and a servo (HS-755 HB) externally via batteries. The target is to have the max. life time.
The servo will work with 4.8V or 6v as the max. Torque changes respectively.
After researching about batteries I have identified  two feasible options (considering price, mobility and space) disregarding the mAh value of the batteries.

Option 1: 4x 1.2V AA Nimh batteries --> 4.8 V

Option 2: 4 x 1.5V AA Alcaline batteries --> 6V

Currently the advantage I see at the Nimh batteries is that  they supply an average 1.2V throughout most of their discharging life time whilst the voltage of alacaline batteries drops quickly.
As I have followed this discussion (see link below) it is said that the Nimh batteries will go below 1.1V after 70% usage whilst the alcaline will go below 1.2V even after 50%. I guess my servo will not work if the Voltage drops <4.8V.
Is my choice of Nimh batteries the most beneficial one considering maximum time of usage for me as long as the torque provided with 4.8V  is sufficient? Is there any mistake in my assumption?
Replacing 6 series AA alkaline batteries with NiMH batteries – how do I compare possible arrangements to optimise usable capacity?

dathasheet of the servo: http://cdn.sparkfun.com/datasheets/Robotics/33755.pdf


texts: Compare over discharge protection disconnect circuits

texts:
I am trying to implement a "discharge protection" circuit for an uC (Arduino) powered by a battery. The uC monitors battery voltage and needs to be able to signal the circuit to turn off. Turning on is accomplished by pressing a momentary switch.
The goal is to save power and the circuit should use no or very little power (uA) when on and when off. Due to power requirements I understand that I need to use MOSFETs rather than BJTs.

I have tried to implement the following circuit: http://educ8s.tv/auto-power-off-arduino-simple-circuit/ which is using one N-channel MOSFET to disconnect the negative lead of the battery.

Circuit 1 http://educ8s.tv/wp-content/uploads/2016/03/schematic.png

The result is that the uC is using the Drain as its ground. If I want to send "low" from the uC to the Gate I get strange results that I don't understand and the MOSFET conducts. The only time it doesn't conduct is when Gate is pulled down to battery ground (Source) and not connected to anything else.
Trying to understand why my implementation doesn't work as in the article I found other circuits for this purpose.

Arduino Battery Over-Discharge Protection (O-DP)
Describes a circuit with two BJT transistors, a NPN and a PNP.

Simple low voltage disconnect circuit for Arduino
Describes two circuits.

One similar to the two BJT transistor variant but with MOSFETs

And another with an opto-coupler and a MOSFET

I am trying to understand what the differences mean.
Can the first, 1 MOSFET, circuit work or is it incorrect?
Which circuit is most power efficient?
Why is an opto-coupler used? How much current does it use and how does it compare to BJT/MOSFET?
Should I switch the positive power source lead or the negative one?
Can the uC function correctly when its ground is Drain and not the power source ground?


texts: How to make the Vout from an OPAMP to 0V?

texts:
I'm trying to design a Analog to Digital Converter circuit with a OPAMP circuit helps convert Vin from bipolar to unipolar signal before goes to input ADC pin (just look at the circuit!)

well the circuit works so far, but when the Vin = GND, I can't get the Vout from OPAMP = GND (0V). it just higher!
So how to solve this? I tried using LM358, LM393, LM324, MCP6002, but it still not worked =(
Please help
Here are some of my ideas i think might work but i don't know how to build:
- Switch to another OPAMP. i think good OPAMP might help but i don't know what type, and the price will be a problem because i don't have so much money
- Are there any ways to subtract the Vout from OPAMP? like VinADC = VoutOPAMP - Vsubtract, then it can get to 0V. but I didn't found anything seem possible!
- I tried researching the Virtual Ground methods, so I think there are some how make the ground of the ADC circuit "higher" than the OPAMP circuit ground, but still supply enough current for the ADC and following circuits (at least 50mA). Any suggestions?
Please help!! And by the way sorry if my English is not good =)) thanks!


texts: Controlling individual LED strips of different kinds and lengths with a single microcontroller

texts:
I am designing a little bit of a lighting show composed of a few individual led strips which will be controlled by a microcontroller, Arduino UNO in particular. I want to control 7 individual led strips:

5x RGB 5050, 60 LEDs per meter.
2x UV 5050, 60 LEDS per meter.

Taking in consideration that the RGB LED strips need 3x PWM pins each, and I want to have a full control over the brightness of the UV strips too, we come up with a
5x3 + 2x1 = 17 PWM pins in total. Obviously, neither the Arduino UNO, nor even the Mega have that many PWM pins so I decided to go after a LED driver - TLC5940. It can control up to 16 channels so I'll need 2 of it(+ the option to add more strips later). Can you guide me if I have any flows in the design and maybe if there's a better solution for my situation. The current setup is something like this:

The LED strips will be of varying lengths but I'll keep them 4 meters of length maximum. So:

4x RGB LED 5050, 3 meters each:

Amperage: (1.2A/m * 3m) * 4strips = 3.6A/strip * 4strips = 14.4A
Power: (14.4W/m * 3m) * 4strips = 43.2W/strip * 4 strips = 172.8W

1x RGB LED 5050, 4 meter:

Amperage: 1.2A/m * 4m = 4.8A
Power: 14.4W/m * 4m = 57.6W

1x UV LED 5050, 3 meter:

Amperage: 1.2A/m * 3m = 3.6A
Power: 14.4W/m * 3m = 43.2W

1x UV LED 5050, 2 meter:

Amperage: 1.2A/m * 2m = 2.4A
Power: 14.4W/m * 2m = 28.8W

Totals:

Amperage: 25.2A
Power: 302.4W

I'm planning on powering all the strips with a single 12V power supply allowing:

Amperage: 30A
Power: 360W

Each pin of the LED driver will lead to a TIP120(or maybe TIP31C) transistor to control each color channel of the strips(3 transistors for each RGB strip, 1 for each UV).

I'll also need to use some additional wiring for the strips in other to get them all to the controller(1-3m) because they'll be quite spread so should I be concerned about reduced brightness?

Also, never worked with a LED driver before, can it handle the job I'm assigning it for?

Do I have to add any resistors to the transistors?

Any help and positive criticism will be appreciated.

EDIT: The question is also posted on the Arduino forum. You can find a reference to the thread HERE if you're interested.


texts: Understanding of Dominant Pole Compensation

texts:
According to Miller Effect, within amplifying devices such as transistors that have inverting voltage gain higher that one, there should be increased input capacitance with increased voltage gain of an amplifier.

I has been also said that this effect is limiting the amplifier at higher frequencies. This is where it comes to incorporation of a method of increasing the transistor's bandwidth. One of them is dominant pole compensation.

According to Wikipedia:

  "When a capacitor is introduced between the input and output sides of
  the amplifier with the intention of moving the pole lowest in
  frequency (usually an input pole) to lower frequencies, pole splitting
  causes the pole next in frequency (usually an output pole) to move to
  a higher frequency."

I get the part when it states that 2nd pole should be moved higher in frequency (that is probably the 2nd roll-off), but why the heck would you want to decrease the 1st pole and consequently first gain roll-off begins at lower frequencies than before. What is the point of it?

I mean, shouldn't it be desired for that gain vs. frequency curve to be as flat as possible, as long as possible - to higher frequencies? But with addition of capacitor between input and output node of voltage amplifying stage, the 1st pole is decreased in frequency and at the same time that flat gain curve just became shorter then before.

I kind of get what upper plot is trying to achieve there - constant decrease of gain with increase of frequency; the straight dotted line from 1st to the 2nd roll-off of gain curve. But still, the gain is decreasing in that area, decreasing! Wouldn't it be desired to be flat as long as possible?

There are still two or three questions that are unclear to me (if some good comments are added then this post can be easily edited):

Referring to the phase margin: Between which two points the phase shift occurs? Within negative feedback? Is it added to basic 360° shift from output of amplifier to input of negative feedback?

Also I read somewhere that the phase margin is the negative feedback to positive feedback factor. Can it be represented in such manner?


texts: How to control ESP-05 power using Arduino (both are 3v3 devices)

texts:
I have ESP-05 connected to Arduino Pro Mini. Both are 3v3 devices. I need  Arduino to power on/off ESP-05 device using GPIO when needed. Please suggest.

I tried to use N Mosfet but that did not work possibly because example is with different power supplies.


texts:
I'm trying to understand this material from C.Basso regarding TL431 compensation (Designing Compensators for the Control of Switching Power Supplies

If you refer to pg.110, there is one example regarding TL431 based on type 2 compensator.

From the example, it stated that it require to provide 15dB at 5kHz with 50 degree phase boost. Basically, I understand all the calculation & phase boost operation using type 2 compensator.

However when it comes to pg.111, it mentioned that with Cpole = 2nF (this is based on pole value in optocoupler @ 4kHz) & C2 = 581pF, the bandwidth cannot be reached, therefore crossover frequency need to be reduced.

Questions:

From the slide above, how they know that the bandwidth cannot be reach with these Cpole (2nF) & C2(581pF) value? Any calculation example would help.
If bandwidth cannot be reached, what will happen to the system? Any example case will be help, because it’s hard for me to imagine the impact of bandwidth to power supply system.


texts: ESP8266 and Arduino - SoftwareSerial vs Serial problem

texts:
I'm using Arduino Nano and ESP8266.

When I setup like the picture and connect Arduino Nano to PC by USB:

The ESP8266 properly works. (Arduino Nano is just used as a bridge)

I print and read from serial with a C# program, it correctly works.

What I send from C# program:

AT+CWJAP="APN", "Pass"

The message from ESP:

AT+CWJAP="APN", "Pass"
OK

But, when I change the setup as follows:

Green wire (green wire on picture) to Arduino Digital2 pin
Red wire (red wire on picture) to Arduino Digital3 pin
Use Arduino code to read/write serial, instead of C# program
Create a software serial from code (esp8266 = SoftwareSerial(2, 3))

What I send from SoftwareSerial:

AT+CWJAP="APN", "Pass"

The message from ESP:

AT+CWJAP="APN", "Pass"
ERROR

Do you have any ideas? Why isn't the result on SoftwareSerial identical to Serial?


texts:
I'm trying to switch high-quality audio signals using 2 serial relays like the picture below.

I'm not sure if this is the best solution to switch between 2 inputs and 2 outputs, but here it is.
In this case, I'm sure ESD protection is a must. So I'm trying to place fewest TVS diodes at the best location.
I thought it would be the best to place it in between 2 relays because regardless of the input/output selected, it will go through the middle.
is my thinking on the right track? Do I just have to find the right Diodes now?
Any comments or suggestions are welcome on any part of my thought.


texts: How to make a LED bar display a binary value?

texts:
I have a 5-bit binary number from 0 to 11110 (30 decimal). I want to display it in a led bar using "bar" mode. It means that if the number is 10000 (see the picture below) I want ALL 16 leds from the first to 16-th be on. The circuit below turns on only one led corresponding to the input number.
How can I make it?

Update:
I ended up using 74HC238 as 3 to 8 bit decoder + 29 logical OR elements (7432 IC).


texts:
I'm experiencing a strange behaviour on a board where I'm using LTC4353 as a "12V Main and Auxiliary Supply Diode-OR" . The circuit I'm working on is depicted below (it's pretty the same circuit found on page 11 of the original LTC4353 datasheet)

When VIN exceed 9V OUT value it correctly feeds OUT (with a value around VIN minus the voltage drop on Q2 RDSOn). When VIN falls below 9V U5 correctly switch the power source (shutting off Q2 and enabling Q1) and +BATT feeds OUT. BUT In this condition (Q1 enabled) I can measure an unexpected voltage drop around 0.6V on OUT (I was assuming being near +BATT minus voltage drop on Q1 RDSon ... far less than 0.6V).
I cannot understand why this's not working and if this's a standard behaviour why it's not symmetrical.. BTW the circuit have been tested with a light load conneted between OUT and GND (1kOhm).

On page 8 of the datasheet I found "The disadvantage of these approaches is the diode’s significant forward-voltage drop and the resulting power loss. The LTC4353 solves these problems by using an external N-channel MOSFET as the pass element. The MOSFET is turned on when power is being passed, allowing for a low voltage drop from the supply to the load. When the input source voltage drops below the output common supply voltage it turns off the MOSFET, thereby matching the function and performance of an ideal diode".

In my opinion this device should work as an Ideal Diode power supply OR circuit but it seems not to work properly ... someone suggested me that the voltage drop should be caused by the body diode effect  (which one?) but I cannot understand how it can lead to such a voltage drop on OUT since both MOSFETs drains are equipotential to OUT.


texts:
It is my first question on this site and I'm probably doing something wrong, try to be gentle! haha
I want to provide 3.3V to my ESP8266 module from my Arduino, but people say this WiFi module requires more current than that 3.3V pin can provide. So I'm getting 5V from Arduino and turning it into 3.3V through LD1117 (just as it is done here http://iot-playground.com/2-uncategorised/17-esp8266-wifi-module-and-5v-arduino-connection).

simulate this circuit – Schematic created using CircuitLab

This is the little guy.

The problem is I can't get it to provide 3.3V. With no Resistor Load, output is 4.2V.

With low Resistor Load (1k Ohm) just for the purpose of testing voltage does not keep at 4.2V, it drops, but it shouldn't, right?

simulate this circuit

I'm starting to think that maybe providing 3.3V directly from the Arduino isn't that bad of an idea. Can someone guess what I am doing wrong with this LD1117? Thanks in advance!


texts: I've researched this for a while now and can't find any answers for the life of me.. How can I add a headphone jack to an audio amp with speakers that disables the speakers when headphones are plugged in? There are only two possible explanations I can think of: there would have to be some sort of physical switch that cuts the speaker lines when headphones are plugged in, or something would have to be coded in a chip to disable the speakers. Can someone tell me how it's done?


texts:
Is it possible to use mesh analysis in BJT circuits? I tried to do it, but it does not work.

EDIT: the exercise in which the mesh analysis does not work is the following (the correct value of resistance is \$R_{E2}=640 \Omega\$).
Data: \$V_{CC}=12V, h_{FE}=100, I_{E1}=I_{E2}=0.002 A, R_{B1}=25467 \Omega, R_{B2}=74533 \Omega, R_{E1}=1000 \Omega, V_{BE,ON}=0.7V\$


texts: Both diodes are ideal, can we find what is potential drop acoss each diode in this situation, if yes what is potential difference across each diode


texts: I have a Dayton 2m145 universal motor that has four wires as shown in attached image. Red connected to brush and yellow connected to other brush, purple connected to armature and grey connected to other side of the armature. I know nothing about motors, please help connecting to 115 volt wall output.


texts: Simple, efficient "breathing" LED circuit

texts: I'm currently working on a small circuit, which I intend on running off a CR2032.  The intent is to have the circuit last at least 2 weeks (the longer the better), pulsing a green LED every 3 seconds, with a DIP switch to toggle power.  I'm planning to use a 555 timer with a generic green diffused LED, but I feel like there's an IC that may accomplish this more efficiently.  What's the most energy efficient, small (the PCB is going to have a surface area no larger than 1"), simplest way to pull off this circuit with a CR2032 or comparable?  Thanks guys!


texts: With this question, I am not too sure about the V1. Would it be the same as the 15V source on the left or is my calculation correct?


texts: Driver circuit for Figaro FECS sensor - specifically FECS44-100

texts:
I need help designing a driver circuit for a Figaro ammonia sensor FECS44-100

I also have in my possession, the official evaluation module EM-FECS(A)

The schematic for this (on page 2 of the link) seems to be an amplifier to convert the output from uA to a 0-5v output. However I would prefer to read the voltage into a precision ADC, something like AD7791. The datasheet specifies a 33 Ohm load resistor, so I assume this should be placed between 2 of the pins, giving a full scale output of 3.3 mV

The sensor itself has 3 pins labelled:

Counter
Working
Reference

Is anyone able to shed some light the function of each of these pins?


texts: Implementing a 8X1 multiplexer using two 4X1 multiplexer

texts:
"Obtain an 8 X 1 multiplexer with a dual 4-line to 1-line multiplexers having separate enable inputs but common selection lines. Use a block diagram construction."

This is a question i came across recently . now the doubt i am having here is that can we just implement it by assuming that mux has a enable pin .I mean is there any other way of implementing it .


texts: Is the BLDC motor and "brushless AC servomotor" same thing?

texts:
Are the terms BLDC motor and "brushless AC servomotor" exactly the same thing? I cannot find information so far whether there is difference.

For instance, at this site they are treated as if the same thing.

And at the moment I have this brushless motor where it is called at page 8 as "AC servo motor". And here is the photos of its stator and rotor:

stator:

rotor:

It seems very similar to BLDC but they don't call it as such and they call it brushless AC servo motor. What are the differences if there is any?


texts:
I'm using the A6 GSM module to send data from my sensors board to a server via GPRS.

The problem is that most of times, usually when the module attaches to the network or connects to the server, noise appears on the UART A6 TX line and the controller reads garbage. After this noise appears, the next command sent to the module gets a CME error response. I suspect the noise it generated by the chip, maybe caused by the RF transmitter.

Sometines it works, but most of the times it fails. I've tried putting 100pF capacitors to GND on the UART lines and lowering the baud rate to 2400 baud, but with the same results.

If it has anything to do with this problem, I mention that I am applying 3.3V level on the UART line (the A6 supports 2.8V), since I did not have a voltage translator available when I made the board.

Has anyone encountered this problem? Is there a solution or should I use a different GSM module?

UPDATE

The GSM module is a ready made breakout board from Ebay. The module is connected to my microcontroller board by wires. My power supply is a R-78E5.0-1.0 DC-DC converter that provides 5V/1A. I've tried powering the module from a separate 2.5A power supply, but the results are the same. These are my schematic and setup.

The SIM card is connected via an extender. I've also tried without the extender, but with the same results. In the setup you can also see the logic analyzer connected to the UART lines and GND.

This is the output from the logic analyzer (the last waveform is module TX analogic):

The noise consists of bursts of impulses, from 2.2V to 3.7V, or longer pulses from 1.9V to 3V. I usually receive CME Error 50 (EXE_FAIL) and CME Error 58 (which is not described in the module documentation).

I tried connecting the antenna via an RG316 cable coax cable and the noise disappeared. With or without shielded wires to the microcontroller board, there was no noise. Does anybody know why?


texts:
I just want to check my understanding of LVD.
I have a portable device that operates on a 30V DC input. Its output is less than 30V DC and is powered by a wall plug (UK 240V) that I supply.
Am I correct that LVD does not apply to this device as it is under the DC threshold of >= 75V DC and <= 1500V DC ?


texts: Current flowing in an open circuit to make it the same voltage

texts:
I've tried to research this answer for quite some time but i'm struggling to find a proper answer. I think my question falls between antenna theory and batteries.

So in a dipole antenna we supply a sine wave across the antenna and this generates a small current due to capacitance and the electron flow at that frequency.

Now suppose we take this example to a DC circuit I understand DC current cannot flow in an open circuit because the battery has a net neutral charge and if you just discharge one side the other side creates an electric field to pull the discharged side back.

But if put that battery across two huge metal blocks one on each terminal will you get a current flow as one side has electrons added and one side electrons removed? As I understand for one side to be at +12v it must have a lack of electrons and the other side a surplus so there must be some electron flow to make each block equal to the voltage? Otherwise my understanding of the antenna doesn't seem to make sense.

Then theoretically if you charge one block to 12V and one block is at 0v then disconnect the battery what happens to the charges on each block?


texts: Replacement for low resistance JFET current limiter?

texts:
A classic way to protect opamps from excessive input current and still preserve a low source resistance (for noise reasons) is to use dual JFETs in combination with rail-clamps internal to the op-amp.

simulate this circuit – Schematic created using CircuitLab
With JFETs all slowly going EOL, I wonder how to do this without JFETs. Ideally, how do it better than JFETs.
This means:

Negligible resistance in a non-overvoltage case. Say maximum ~100 ohms.
Allowing no more than e.g. ~5mA to pass in either direction.
No leakage to rails, to preserve the low input current rating of FET amps. E.g. maximum rail leakage of 10 pA over temperature.


texts: How do I drive 4 motors from a single L293D?

texts:
I have 4 DC motors, and I do not need to individually control each of them. Can I connect all the motors parallely to one pair of motor pins on the L293D? Does this pose any issues?

I'm using BO geared motors with the following specs:
    RPM - 100;
    Output Torque - 0.8--5kgcm;
    Operating Voltage - 3v-12v;
    No-load Current - 57 mA;


texts: How to make LC tank circuits oscillate continuously?

texts:
An LC tank circuit produces oscillations, when the capacitor is charged and connected to the inductor, but the oscillations decay gradually. How to make it continue, i.e. oscillate continuously?

I know we need to add energy continuously, but I don't know how.

Could anyone describe a circuit that provides a non-decaying oscillation?


texts: Can VCC and ground be swapped on a microcontroller?

texts: We have a Particle Electron microcontroller connected to an Adafruit RFID Shield(PN532). Somehow, the microcontroller's VUSB (+5V typical) ended up connected to the GND pin of the Shield and the microcontrollers 3V3 to the Shields 5V input. Oddly enough, the devices seemed to properly function despite this. Shouldnt this cause an issue? Is it okay to just swap the ground and supply pins on a microcontroller?


texts: Using a voltmeter to measure RMS value of a sine signal with a DC offset

texts:
Imagine you have a periodic signal F which is nothing but a sinewave (S) plus some DC offset (D).

Here is an illustration of such signal:

Imagine I want to measure the RMS value of this signal F.

The rms value of this signal mathematically can be written as:

rms_of_F = sqrt[ (rms_of_S)^2 + D^2 ]

So far so good.

First of all, if I use the DC settings of a voltmeter I would obviously not read the rms value.

Then I may use AC settings.. But recently I came to a question: What value does ammeter or voltmeter measures (RMS, Average or Peak )?
where the answer is chosen as follows:

  Measuring RMS values is a bit more expensive than measuring average
  values, so most multimeters avoid the former. Instead they presume
  your signal is a sine and measure the average value for the rectified
  sine or the peak value, after which they apply a conversion factor to
  find the presumed RMS value.

Does that mean the rms value of my signal F can never be mesured accurately by using a voltmeter?

I'm asking because in case the voltmeter in AC settings doesn't measure the rms value: if one calibrates an instrument and relate the rms value of such signal output to the device reading(any parameter like temperature, flow ect.);
and if another person would use a multimeter/voltmeter to use the calibration expression, this could lead him a wrong conclusion because he will not read the true rms voltage but something else.
Is that right?


texts: differential instrumentation amplifier in LTspice not working

texts:
I was trying to simulate an instrumentaion amplifier in ltspice.
the problem i am having is the output when measured across C1 is wrong. since i have an amplification factor of 11, i was expecting to get (V2-V3)*11. which should be 11V. but i get 5.5V instead. if i change the power supply for the opamps from single supply (15V,GND) to dual supply +/-15V, then it works perfectly. any help?


texts: 8/16 bit microprocessor for hobby project

texts:
I'm evaluating different processors for a small hoby project. My first choice was the Z80 but it seem to be hard to come by nowdays.

Whats left for us that wants an 8/16 bit CPU clocked on 10-20 Mhz with an external memory bus ?


texts: Converting differential-current output to single-ended voltage; adjustable gain

texts:
I want to convert differential-current output of DAC2902 to single-ended voltage. Can I do it with following differential op-amp configuration at the output of the DAC?

The voltage gain is fixed = 1 in this circuit. If I need to make the output voltage gain adjustable then how can that be done?


texts: Two power supply units, equivalent settings, different results, why?

texts:
I recently bought a 3d printer which runs on a Melzi v2 board [http://reprap.org/wiki/Melzi]. It came with a 12V 20A power supply unit (multimeter readings showed values ranging from 11.8V-12.1, im my books that seems ok). After completing all the assembly work and re-checking [multiple times] that all connections were correct and secure I powered it up. Everything seemed to be working perfectly up until I plugged the USB port into my computer, windows  notified me that a power surge has occurred on the port and shut the port down. The USB cable was burning hot and one end of the connector started to smoke. I quickly turned everything off. I disconnected all the wires on the board and discovered that one of the IC's on the board had short-circuited. Further inspection showed that the GND pin on the usb was sinking a large amount of current (cable was permanently damaged so I threw it away). I contacted the manufacturer and they sent me a new board.

This time around I decided to place some safeguards between my pc and the board, so I placed two 50 ohm resistors on the D+ and D- lines and a 6V 0.1A fuse on the GND (see image below). When I powered everything up, once again everything seemed to be working fine up until I connected the USB cable in. R1 and R2 both burnt up so I disconnected everything (this time around board and pc were fine). I changed out R1 and R2 and decided to retry the experiment with my lab power supply set to 12V. The problem disappeared.

simulate this circuit – Schematic created using CircuitLab

So my question is why would two different power supply units, both at equivalent settings, be giving me different results?

Any help/suggestions would be much appreciated!


texts: I have an AC PWM dimmer board from eBay that uses a potentiometer to control the dimming level. I want to replace it with a digital potentiometer that would serve the same function. However, it needs to be able to handle at least 120VAC and 0.5mA. It also has to be able to be controlled by 5VDC from an Arduino, Raspberry Pi, etc. Does anyone know of any such part?


texts: General question about Capacitor sizes in DC circuits

texts:
A general question -- let's say there is a DC circuit with a capacitor that needs to be replaced.  Can I use any capacitor that is at least as large or do I have to use one that is exactly like the original one?

Of course, for AC circuits, they have to match exactly because they determine frequencies, but in DC circuits I don't think it matters. Another way to ask the question is can anyone think of an application other than frequencies/filters where the capacitance cannot be too big?


texts:
We are doing a massive purge of "stuff" from home and storage. I am accumulating a large quantity of random, unmarked power cords. Some will have "Nintendo" or "Norelco" on them - so I know to go confer with my boys about their gaming stuff or check my husbands grooming items, etc.

But what I am confounded by is several totally generic type cords - with a specifically shaped female pin end and standard oriented plug end(one prong larger than the other). There are numbers imprinted on both ends as well as printed in white ink along the wire. Lots of numbers. I attempted a google search but the results were equally random. "AC power cord for some electronic device."

How can I determine what each cord is for? I don't want to store them all "in case" - but I also don't want to throw them out only to discover they were needed for something we still use (or want to sell, give away, donate).


texts:
I currently have an Unipolar Stepper Motor with 6 wire and a A4988 Pololu Stepper Driver also Arduino Board, but there are not any guide to connect Unipolar Motor with Driver, Only Bipolar.
  Someone help me solve this problem, does this driver support Unipolar ? and How?

Many thanks!


texts: Why don’t 12v batteries connected in a series get overloaded?

texts:
Suppose I have two 12v AGM batteries and I connect them in a series to up the total voltage to 24v.

My question is: how come this doesn't overload the batteries if individually they can only be charged at 12v~? How come they can collectively now be charged with a 24v input when connected in a series? I thought excessive voltage damages electronics. Also, what's the max number of batteries that can be chained together in series and how can I determine what kinds of voltage would damage a battery?

(I tried searching for a long time to understand why batteries might allow this but the only information I could find on this was explaining how to do it instead of why it works. Apologize if this is a basic question.)


texts: Can a 3.2V, 400mAh battery charge a smartphone?

texts: I have a solar panel that slowly charges this battery and I am thinking of trying to make a cell phone charger out of it. I know it won't be fast, but will it be able to charge a phone?


texts: Reading frequency of an audio signal from Android device

texts:
I am doing a project that reads frequency of audio signals generated from Android device through the headset jack. The audio jack is connected to Atmega microcontroller as shown in the figure.!

I am using the analog comparator to compare between a reference voltage 2.61v and the audio signal (DC biased; AC + 2.5v).
The audio signal range is 200mv p-p so after DC biasing it will be from 2.3 to 2.7.
When the comparator input 1 passes 2.61 (reference volt), a timer starts to measure the frequency.
But the problem is I am not getting a stable reading of frequency. For example, if the signal is 1000Hz, I read it between 4000 and 5000 Hz. The values always change. Sometimes the comparator outputs one for few microseconds even there is no audio signal (the output should be zero).!!

I think the problem is one of these:

The power supply has a high ripple so I cannot read low-level signals properly.
I should use a higher blocking capacitor C2 like 10uF instead of 100nF.
The 200 mv is in the range of noise signals, I should amplify it before read.
The voltage divider should use high values of resistors like 3MOhm as in the Hijack project below.

What do you think.

This is similar to the hijack project proposed by UMICH. Their schematic is shown below.


texts: Is an LR Phase Shift Oscillator possible?

texts: All the phase shift oscillators I've seen use RC stages each of which produces a 60degree phase-shift. Is it possible to inductors instead of resistors? My understanding is that inductors also cause a phase shift, but I've seen no designs which use inductors. I tried to simulate the following circuit, but while I can get it to resonate I can't seem to find a set of values/configuration that oscillates:


texts: To use a Dual Voltage Electric LED Bulb E26 in a E27 environment/ socket?

texts:
To use a Dual Voltage Electric LED Bulb E26 in a E27 or B22 environment?

So I bought a Universal LED Bulb that emulates Circadian Rhythm for lighting to help manage my sleep cycles, locally (wherever I am) as well as when traveling.

Most of my time is spent between:

US (Currently ordered & Shipped E26) &
India (mostly B22 around and newer installations have E27)
Some other nations now & then (not long enough to order there)
I have a local India store bought (Similar to pic below) B22 to E26/E27 converter I've used before)

Wont work with new E26 bulb; appeared it would, but did so for E27.
On checking, previous china made bulb model was E27 bought via Amazon US

When I googled why, this was the answer that popped up -

Can A Bulb With An E26 Base Fit In An E27 Socket?
The answer is sometimes. Sometimes an E26 base will fit into an E27 socket, while other times an E26 base will have one extra tread, preventing it from reaching the bottom of the socket and forming a connection.

Question: How do I make it work in India or any E27 / B22 locations ?

Find a converter that does B22 to E26 and a E27 to E26 also (Hard find?)
Small DIY hack on converter that manipulates / fixes around this E26/E27 difference?

Updated Data: "Standard" bulb base: E26 or E27? Both?
https://www.homeownershub.com/maintenance/standard-bulb-base-e26-or-e27-both-266061-.htm

Sarah wrote:

E26 (US) are one millimeter shorter and may not make contact with the base. No contact, no light.
Longer, E27 bulbs will make contact in the shorter base. I have had the same experience.
All my USA purchased lamps worked great in Europe.
None of my European lamps or ceiling lights worked in the USA without bulb base adaptors.
It has been so long since I purchased them I can't tell you where to go.

The difference of the lamp socket E26 and E27
http://www.lampholder.net/support/lamp-socket-E26-and-E27.html

The threads are the same but I believe E27 is a longer base, meaning a European bulb would fit an American socket but the reverse might not be true.
I seem to remember a German customer of one of my former employers who brought several lamps over from Germany, and had no problem getting American bulbs to fit.
They are the same diameter and thread size. The only difference is that the E26 is 26mm long and the E27 is 27.5mm long.

https://en.wikipedia.org/wiki/Edison_screw

E26 or E27 Edison Screw?

There is only a 1mm difference between the threads of E26 and E27, so they are virtually identical. Still, it's important to buy the correct bulb certified for use in your country. This is because each country and region of the world, have different certifications. B22 bulbs are also available. They are not as popular, and generally used in the UK, Australia, and India.

An easy reference of what Bulb type is used in major markets is as follows:

United States - E26 Edison Screw
Canada - E26 Edison Screw
Japan, Korea & Taiwan - E26 Edison Screw
Australia - E27 Edison Screw (or B22 Bayonet Cap)
Europe - E27 Edison Screw
United Kingdom - E27 Edison Screw (or B22 Bayonet Cap)

For legal, and cost based reasons, the only bulbs we sell/ship to the United States are E26 connector bulbs.
E27 bulbs are only available to ship to countries where they are certified. We do not ship, under any circumstances, E27 bulbs to the United States.

"Bulbs have a universal power supply. They will work with electric grid power from 100-240V 50/60Hz"

"The following countries use E27 bulbs:
..India..
"


texts: Find the transfer function of the system given by its weight function

texts:
I've understood that, to find the transfer function of a system, given its weight function, Laplace transform should be used.

I.e. if $$w(t)=50\,\cdot(e^{-5t}\,-\,e^{-10t})\,\cdot\,u(t)$$ then

$$W(s) = \int\limits_0^\infty w(t)\,e^{-st}\:dt$$

How is this solved further? I understand that w(t) is inserted into the formula for the transfer function W(s), but cannot obtain the correct answer through sequential math steps.

The final answer should be:

$$ W(s) = \frac{5}{(1+0.2s)(1+0.1s)}$$


texts: Is there a current-to-voltage converter circuit for professional applications?

texts:
We want to measure the information from three sensors that generate current (4mA for the minimum value and 20 mA for the maximum).
Obviously, a simple solution could be to use the classic current-to-voltage converter with an OP.

But if I want to do something a little more professional, I imagine that there is some dedicated integrated circuit that does this conversion.
Am I right?
Any comments or suggestions are welcome.


texts: What is the purpose of an "anti-pumping relay"?

texts:
A project I'm working on has another firm replacing the anti-pumping relay on a motor starter (4160 V, 500 hp). I've never heard of an anti-pumping relay and after googling it, I still don't understand the purpose. My summary is that it prevents a circuit breaker from 'hunting' and repetitive closures.

How does a circuit breaker 'hunt'?
How do repetitive circuit-breaker closures occur?
What does an anti-pumping relay do?


texts: How to build AND Gate using transistors?

texts:
I am very new to electronics field. Especially to the digital electronics.

I am trying to make an AND gate circuit using transistors, switches and LED.
I have tried the below circuit:

simulate this circuit – Schematic created using CircuitLab

But there is a problem when simulating this circuit.

SW1     |     SW2     |     LED
OFF     |     OFF     |     OFF
OFF     |     ON      |     80%
ON      |     OFF     |     20%
ON      |     ON      |     100%

As you can see that above mentioned truth table is not AND Gate but it looks more like OR Gate. So, what is my mistake??


texts: What is the general form of a first and second order dynamic system, in laplace and time space?

texts:
I have some of the information, but a lot of it is missing and I cant find a clear answer on the web.

The general form of a second order dynamic system is:

$$\frac{d^2x(t)}{dt^2}+2\zeta\omega_n\frac{dx(t)}{dt}+\omega_n^2x(t)=f(t)\:\:\:\:\:\:\:[1]$$

where

x(t) - is the output, e.g current
f(t) - is the input, e.g a voltage signal
zeta - is the damping coefficient
wn   - is the natural frequency

An example of a second order dynamic system is a RLC circuit. If a resistor, capacitor, and inductor are connected to a power source with voltage at time t equal to f(t), the summed voltage across the three components always equals f(t) at any time t.

$$Ri(t)+\frac{1}{C}\int_0^ti(t)dt+L\frac{d\,i(t)}{d\,t}=f(t)\:\:\:\:\:\:\:[2]$$

So for example if f(t) is a step input from 0 to 6V, the equation will be:

$$Ri(t)+\frac{1}{C}\int_0^ti(t)dt+L\frac{d\,i(t)}{d\,t}=6\:\:\:\:\:\:\:[3]$$

If this equation is rearranged so that it is in the general form shown in equation [1], then you will be able to find out the natural frequency of the system (omega_n) and the damping coefficient of the system (zeta).

The general form of a first order dynamic system in laplace space is:

$$G(s)=\frac{k(s+a)}{s+b}\:\:\:\:\:\:\:[4]$$

where

G(s) - is the transfer function (output/input)
k    - is the "gain" of the system
a    - is the zero of the system, which partially determines transient behavior
b    - is the pole of the system, which determines stability and settling time

An example of a first order dynamic system is a RC circuit. The voltage across the resistor plus the voltage across the capacitor equal the voltage of the source f(t) at any time t.

$$Ri(t)+\int_0^ti(t)dt=f(t)\:\:\:\:\:\:\:[5]$$

So again, for a step input from 0 to 6V, the equation will be:

$$Ri(t)+\int_0^ti(t)dt=6\:\:\:\:\:\:\:[6]$$

In laplace space this is

$$RI(s)+\frac{1}{Cs}I(s)=\frac{6}{s}\:\:\:\:\:\:\:[7]$$

rearrange to general form:

$$I(s)*(Rs+\frac{1}{c})=6\:\:\:\:\:\:\:[8]$$

$$I(s) =\frac{6}{Rs+\frac{1}{c}}\:\:\:\:\:\:\:[9]$$

$$I(s) =\frac{\frac{6}{R}}{s+\frac{1}{Rc}}\:\:\:\:\:\:\:[10]$$

Since the input was the step input 6, you can see that the steady state gain is equal to 6/R, the pole is equal to 1/RC, and there are no zeros. You could do the inverse laplace transform of this equation to find out the instantaneous current i(t) at any time t.

Now my questions:

I have shown the general form of a first order dynamic system in laplace space, and the general form of a second order dynamic system in time space, but what is the general form of a first order system in time space, and a second order system in laplace space? I have definitely seen these written somewhere but I can't find them in my notes or online.
How would you go from equation [3], to the general form (time space) as shown in equation [1]?

Any answer is much appreciated, even if it only answers one of the questions, or partially answers a question. Thanks for reading!


texts: Using an NPN tranistor as a switch for two bipolar stepper motors

texts:
this is my first electronics project which requires controlling 2 different stepper motors with two motor drivers (L293D). I have found that the number of GPIO pins on my microcontroller (ESP8266) is 9. However, i require 10. I have found on the arduino website a method of using a transistors as switches as shown below which would reduce the amount of pins needed on the microcontroller.

My question is what do the wires control 1 and 2 lead to? is it just back to the GPIO pins of the microcontroller and i code for when the transistors turn on and off, or is there another piece of equipment in between? Also, where do I start from when choose what resistors and transistors to use? Thanks


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simulate this circuit – Schematic created using CircuitLab

If this circuit is a part of a 4 bit full adder, where A1,B1 are adder inputs and C1 is carry in from previous bit, does C2 give the correct output for the carry out bit? According to my calculations C2 doesnot, although S1 generates the correct value of the sum. Please, I need a cross-check.


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I'm trying to apply the superposition theorem.

I'm confused how the value of \$I_2\$ is calculated, from where does the value of 1 come?


texts: AXI WSTRB and AWADDR issue with overlapping writes

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I am having issue with AXI Protocol Checker pc_status[22] AXI_ERRM_WSTRB .

  Write strobes must only be asserted for the correct byte lanes as
  determined from the: Start Address, Transfer Size and Beat Number.

What does it mean by The information on the low-order address lines must be consistent with the information on the byte lane strobes. ?


texts: 3 phase induction motors with poles not equal to 3x

texts: I am having trouble finding diagrams to show induction motors with poles not equal to 3x.  Everything I find is 2 poles per phase.  Can anyone explain and help me visualize, for example, a 4 pole 3 phase induction motor?


texts: Stair lift lead-acid batteries - dead after 1 month

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I encountered the following issue: the lead-acid batteries (2 * 12V 7Ah) that power up the stair lift motor (24V, 0.3 kW) died (the motor wouldn't start anymore, with a nominal voltage at no load of about 12.0V or less for each battery; didn't check them at load) after just 1 month of usage. The lift was lightly used, at most 6 times a day, with a ride of only 6 steps.
The previous batteries lasted for one entire year.
I checked the charger (24V, 300mA switched mode power supply) and is suplying succesfully 24.6V when the lift is at the end of the rail. The new batteries are charged full time with 24.6V and 0.04A (which means that the batteries are full from what I can remember.. 3% of 7Ah is 0.21 Ah).

should I change the power supply with a less nominal current given the fact that the batteries are full time on-charge?
should I disconnect the power supply from time to time so that the batteries won't charge continously?


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I wanted to know the difference between the motor(s) used in the Tesla Model-S and commercially available motors.

(source: insideevs.com)

eBay Motor^
I have been very confused. They both are approximately the same size and of approximately same dimensions. Yet, the motor in the Model-S is capable of delivering upto 259 horsepower, where as a similar sized motor is rated to deliver only about 15 horsepower.
My question is, what makes these two motors so different even though they are physically so similar?
PS: I won't be surprised if in reality, the RPM and Torque output actually depends completely on the controller (VFD maybe?).


texts: If we cannot directly generate DC, why is it said there cannot be any DC transformers?

texts: No matter if permenant magnets, or electromagnetic field is used to generate electricty, there is no way to generate DC directly (except batteries). So, why do we say there cannot be DC transformers? Does it mean we cannot supply a transformer with DC ?


texts: Testing hall effect sensor of a motor [Beginer question]

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I would like to test the hall effect sensor of a motor (DC brushless Papst dual coil) I have for a small project of mine. I have found a bit of information online, but I cannot seem to figure out what I am doing wrong.

I tried this kind of setup to test it : garagelab.com/profiles/blogs/tutorial-how-to-use-the-hall-effect-sensor-with-arduino

Here is a picture of the motor : http://s11.postimg.org/sqfr6jmar/IMG_20150301_161751.jpg
and here is the info that I have with it : http://s18.postimg.org/ra5e6gz61/IMG_20150301_161803.jpg

I am trying to read the output with an an oscilloscope. Here is what I tried : positive battery side to the violet cable, negative battery side to the green cable, positive battery side to 10ohm resistor to my oscilloscope probe and finally the blue (or yellow) cable to the probe.

The only thing I see is a constant 5V from the battery when I manually rotate the motor.

Is something wrong with the hall effect sensor ? With my setup ? With my very basic and limited knowledge of electronics ?

Thanks a lot for you help.


texts: LEDs sharing negative output from driver issue

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I am having an issue with the above circuit when LED DRIVER B has 0 PWM and LED driver A is being driven by a signal driver B is supposed to be off but the leds from BANK B are still lit dim. I checked with a scope and have 0 PWM on LED DRIVER B. One LED from BANK A is enclosed with one LED from BANK B. Bank A is white LEDs and BANK B is Green LEDs. The same issue happens in reverse. When LED driver B has a PWM and LED driver A does not, all LEDs are on. I was not involved with the design and need to find a way to fix this. The LED's are very difficult to get to and it is a last resort to modify the boards they are on by separating the grounds. The banks are never supposed to be on at the same time. When one turns off the other turns on and both are supposed to dim up or down at the same time. The drivers for this circuit are LDD-1500L https://www.meanwell.com/Upload/PDF/LDD-L/LDD-L-SPEC.PDF. I am hoping someone can provide a solution to this without modifying the boards they are on.

We did try adding a diode at the - outputs of the driver to block any possible feedback into the driver but this did not work.


texts: How to trigger a relay and LED when a certain threshold of 0.15 volts is passed

texts: I am learning electronics so this question is learners question. So what is a circuit (referred to as A) that does the following. It has two input wires (say a DC battery for example) , from some circuit referred to as B,  which is a input voltage source to A . When this source voltage exceeds 0.15 volts then a 5v relay is turned and and also an led (that needs a minimum of 1.2 volts to work). The LED is turned fully on with no flickering. The input voltage,into A, can range from between 0 to 6 volts. The power supply for the circuit A is isolated from B power supply meaning  it does not power B  (from which the two input wires come from). A has an independent power supply.  The circuit is to use the LM339N-which seems right to use- which I dont fully understand so far how it work. So I am asking this question on here.  I dont need a fancy answer-just an answer that show how to use LM339N in a clear way to make the circuit.


texts: How to increase an electromagnet's magnetic field size?

texts: I made this electromagnet out of a microwave oven transformer by taking out the secondary coil. It very strong but it can only attract the metals if I bring it really close. How do increase the distance at which it can attract the metals?