texts: AVR C 74hc595 rgb matrix multiplexing and brightness

texts:
I have built a test matrix 2*2 rgb LED's, common Anode. Connected the anodes into columns, and the Cathodes trough 220R resistors into R,G,B rows. Both go to two different 74hc595 shift registers. I am then using this code to light up two LED's diagonally from an atmega48 connected to the registers (bottom left and top right).

/*
 * RGBMatrix.c
 *
 * Created: 15.12.2017 23:35:52
 * Author : Rando Hinn
 */
#define F_CPU 1000000UL
#include <avr/io.h>
#include "util/delay.h"
#define data_out PB2
#define shift_clock PB1
#define store_clock PB0

#define rgb_out PC5
#define rgbshift_clock PC4
#define rgbstore_clock PC3

#define SetBit(BIT, PORT) (PORT |= (1<<BIT))
#define ClearBit(BIT, PORT) (PORT &= ~(1<<BIT))

void shiftOut(uint8_t data) {
    for(uint8_t i=0;i<8;i++) {
        if(data & 0b10000000) {
            SetBit(data_out, PORTB);
        } else {
            ClearBit(data_out, PORTB);
        }
        SetBit(shift_clock, PORTB);
        ClearBit(shift_clock, PORTB);
        data=data<<1;
    }
    SetBit(store_clock, PORTB);
    ClearBit(store_clock, PORTB);
    return;
}

void shiftOutRGB(uint8_t data) {
    for(uint8_t i=0;i<8;i++) {
        if(data & 0b10000000) {
            SetBit(rgb_out, PORTC);
        } else {
            ClearBit(rgb_out, PORTC);
        }
        SetBit(rgbshift_clock, PORTC);
        ClearBit(rgbshift_clock, PORTC);
        data=data<<1;
    }
    SetBit(rgbstore_clock, PORTC);
    ClearBit(rgbstore_clock, PORTC);
    return;
}

int main(void)
{
    DDRB|=((1<<shift_clock)|(1<<store_clock)|(1<<data_out));
    DDRC|=((1<<rgbshift_clock)|(1<<rgbstore_clock)|(1<<rgb_out));
    /*RCOL/LCOL*/
    //shiftOut(0b10111111);

    //shiftOutRGB(0b11010100);
    /*BOT_R/BOT_G/BOT_B/TOP_R/TOP_G/TOP_B/NA/NA active low*/
    while(1) {
        shiftOutRGB(0b01111111);
        shiftOut(0b01000000);
        _delay_us(60);
        shiftOutRGB(0b11111011);
        shiftOut(0b10000000);
        _delay_us(60);

    }
}

The problem here is, that while I do get the LED's to light up, they are incredibly dim. Switching delays to ms, makes them brighter but causes visible flickering. What could I do to properly light the LED's?


texts:
This question is based on the Philips I2C specification UM10204.They gave (section 7.2.1, page 56) for calculating the maximum frequency of the bus:

$$F_{max}=\frac{1}{T_{low(min)}+T_{high(min)}+T_{risetime}+T_{falltime}}$$

\$T_{risetime}\$ depends upon the RC time constant of the bus and \$T_{falltime}\$ depends on lowest output drive on the bus. How are \$T_{falltime}\$ and the lowest output drive related?


texts:
I'm playing with a small 6V ceramic heater. However when I connect it to my 12V .8A DC source it pulls it to 0.  Does anyone have any idea what's going on?

But when I connect it to 4AA batteries it works just fine. I was thinking that the current is not enough from my ppeer source. Is there a CCT I could make to get this heater to work with my 12V,.8A?


texts: How to read this figure (UDN2981 max current)?

texts:
This question is related to this question: why-are-the-pins-of-an-udn2981-related?

In the UDN2981 datasheet, the figure below shows the maximum current (page 14, bottom left picture).

Does this mean if I connect 8 pins (thus using the lowest line in the figure), I can use around 120 mA per pin (thus 960 mA for the total IC), or is it 120 mA for 8 pins together (thus 15 mA)?


texts:
For my senior high school project I decided to build a basic CPU from discrete components. I plan on using a 5V logic level and the current design calls for around 2000-3000 N-channel MOSFET transistors. This question is specifically about the value of the pullout resistor in NMOS logic.

In my breadboard testing I just used 10k resistors as I had a bunch lying around and the value is typical for a pull-up resistor so it seamed reasonable, but it may not be optimal for what I'm trying to accomplish.

As far as I understand the choice of this value is a tradeoff between the power consumption of the CPU and the speed it takes each gate to reach its output value and therefore the max clock speed I could drive it at.

Power consumption:
Lets assume that each transistor has one 10k resistor and all transistors are on. As typical values for R_dson are much less then 10k we can ignore them. This means the power consumption would be on the order of 3000*(5^2)/10000=7.5 watts. This seams surprisingly low - is this value reasonable?

Clock speed:
Here I'm more in the dark. At what clock speed would I be able to drive NMOS circuitry with a 10k pull up vs. a 1k pull up? How would that compare to CMOS circuitry using comparable MOSFET?


texts: using max power transfer theorem to calculate the value of the Rload

texts:
I am clueless of how to find the RL with Max power transfer theorem because don't you need RL to do the max power theorem? I've researched this for like 2 hours now help would be appreciated.
my understanding:
I=Vs/Rs+Rl
then you complete a table of current against power?


texts: Cause of background buzz in my walkie talkie example?

texts:
I got a simple RF24Audio walkie talkie example working.  I'm using the sketch file provided by the RF24Audio getting started example:

https://github.com/nRF24/RF24Audio/blob/master/examples/GettingStarted/GettingStarted.ino

Although my receiver can produce an intelligible audio transmission, it does have a very loud and distracting buzz sound in the background (edit: the sound is a 1.5kHz buzz).  Here's a short video clip so you can hear what it sounds like:

https://www.youtube.com/watch?v=8oKtmhoIhSw

I tried replacing the computer speakers with other computer speakers, with ear phones, and with an 8 ohm speaker.  They all have this background buzz.

This is what my set up looks like:

Link to Circuit

I do not hear this buzz when I hook up speakers and ear phones to the A0 of the transmitter.   A human voice sounds pretty good at A0.  Hence, I suspect this buzz is coming from the Arduino, the nrf24l01 modules, atmosphere interference, or something else.

Can anyone suggest what it might be and what I should consider to reduce or eliminate this noise?

EDIT

When I put the speakers next to several musical instrument tuners, the musical instrument tuners report the buzz I'm hearing is 1.5khz, which is between F#6 and Gb6.


texts: Voltage gain of the MOSFET Push Pull Amplifier

texts:
In our final exam we had a question about the following MOSFET push pull configuration:

simulate this circuit – Schematic created using CircuitLab

where
$$V_{TN}=V_{TP} = 0$$
$$K_N=K_P=4 mA/V^2$$

The question was to plot \$V_{in}\$ vs \$V_{out}\$ for \$-10 < V_{in} < 10\$.
The answer is given as

But I think this is not correct. I wrote the following equation to find the relationship between input and output when \$10 > V_{in} > 0\$
$$
I_D = K_N(V_{GS} - V_{TN})^2=4 \times 10^{-3} (V_{in}-V_{out})^2
$$
and
$$
V_{out} = I_D \times 50 = 0.2(V_{in} - V_{out})^2
$$
Similarly for \$0 > V_{in} > -10\$
$$
I_D = K_P(V_{SG} + V_{TP})^2=4 \times 10^{-3} (V_{out}-V_{in})^2
$$
and
$$
V_{out} = - I_D \times 50 = -0.2(V_{in} - V_{out})^2
$$

Plot of these two equations are

which is substantially different from the one given in the answer.

Am I doing something wrong?


texts: Identification of SWD header for footprint

texts: I figure StackExchange is the fastest way to get an answer. I need a header to put up a SWD connector, looking like this (and yes one of the solder pad is missing), a part number would be appreciated!


texts: How can Kirchoff current and voltage law be applied here

texts: Assuming all the resistors have a resistance of 4 ohms, I’m having difficulty trying to figure out how to find the values for potential difference and current across each resistor. I tried to apply the law to 3 different loops in the circuit, giving me 4 simultaneous equations but there are no real roots. How do I go about tackling this problem?


texts: Level-shifter messing with other voltage rails

texts:
I have a problem that may lead to deeper problems very soon. I have a board with two isolated DC-DC regulators (for 3V3 and 5V):

The outputs share a common ground, as seen. Both regulators have an LED on their respective output rails.

As I am soldering the board and testing step-by-step along the way, I realised that if I power the 3V3 rail, the 5V status LED also lights up. On the contrary, if I power the 5V rail, the 3V3 status LED does NOT light up.

I believe that this is caused by some level-shifter circuitry:

It explains this behaviour I suppose.

Between the 5V rail and ground, I measure several million ohms of resistance, which is expected. Between the 3V3 rail and ground, I only measure 1.2k.

The reason it is 1.2k is because there are six of these level-shifters on the board. The parallel configuration of six 10k resistors more or less conforms to this.

I suppose it's not going to be an issue since the current is limited by the resistor. Is there anything I should be concerned about in terms of the regulators themselves?

NOTE: The regulators have NOT been populated yet. I am simply powering the pads externally.


texts: Chinese power supply schematics/components

texts:
I have a chinese power supply which i brought from a garage sale which has some problems. I opened the case and I concluded that some resistors and capacitors are burned. I would like to repair this power supply to use it for small electronic projects at home (60W, 12V, 5A - these are the written ratings).

I would be very happy if somebody could help me somehow to solve this. I just need to know the values of the resistors (for capacitors is easy) and, of course, some guidelines and tips for replacing them.

I attached some photos, to see what I'm talking about.

Have a nice day ! :)


texts:
I was reading about diode circuits for clippers
According to my observation, I felt only sinusoidal signals are used to give the input.
So, my question is can any wave,for example, square wave, triangluar wave or spikes be provided as an input?

If yes, how?
If no, Why?


texts: Where to start with PCB Schematic optimization

texts:
I am new to PCB and electronics design and I just finished designing a PCB that includes POE flyback converter, Ethernet Phy, a li-ion battery charger, and a DC/DC converter. My design is based on the reference design and BOM/datasheet recommendation of all the ICs to be on the safe side. I ended up with about 300 total and 120 unique components. Mostly it is different resistor and capacitor values but also different FETs for the various power switching converters. Assembly service is very expensive due to the high component count.
How is PCB Schematic simplification and optimization usually done? Where to start? Are there any best practice tips or resources?


texts:
I need to design an edge detection circuit to detect when a square wave signal goes from Low to High (rising edge) and when it goes from High to Low (falling edge). The circuit should preferably use simple logic control such as 74LS series logic. I know people are gonna suggest using an arduino with interrupts but in my application this needs to be done in hardware rather than software.

Edit: The output is expected to be a short digital pulse, used as a trigger.


texts: voltage divider in series and parallel circuit

texts:
I have these two series and parallel circuits and I want to know how I should find the voltage through R1, R2, R3 and R4. I know I should use the rules of voltage divider but I don't know how when I have resistor (R5) in the way and also in figure 1 there is a wire between for the current to go through.

How I should get the voltage through voltage divider in figure 1 and how the voltage changes for R1, R2, R3 and R4 in figure 2 (when the wire for current isn't there anymore).

R1 = R4 = 1k ohm
R2 = R3 = 100 ohm
R5 = 10 ohm
E = 5 V


texts: Can you use batteries to power a device that uses a plug?

texts:
Can you use batteries to power a device?
I have multiple 1.5V batteries, there is a way to tie them together and power a device that uses a plug power supply?
Can I cut the plug and connect it to the batteries that added together have (6V) and the device uses 6V?


texts: Is there an IC that can charge multiple NiMH batteries at once?

texts:
I'm building a battery charger that can charge multiple batteries at a time, and I'm currently looking at Linear Tech's LTC4011 IC, but I think it can only change once battery at a time (a single battery containing up to 16 cells, as I understand it).
Are there any ICs that can charge multiple batteries simultaneously yet separately?
(Also, how might an IC such as the LTC4011 react to charging multiple batteries that are placed in series, "pretending" to be one big battery?) I imagine the chemical charging profile would be all messed up if the individual batteries aren't all at the same charge when plugged in)


texts: Circuit design for co-layout the XTAL and CPU clock output

texts:
I got a circuit design problem. There is a ethernet switch in my circuit.
It is needed 25Mhz crystal input.

There are two option, 1). Using external crystal. 2). Using CPU clock output.

Its block diagram is shown as below.

However, I wanna co-layout both solution, witch means layout these both two solution on the PCB, but finally only chose one solution in the product. For this example, if I chose clock from CPU, it won't mount external crystal, but if I chose clock from external crystal, the clock from CPU won't affect the input clock to ethernet switch.

My question is how to fulfill this idea in my circuit of crystal side?

Kind regard, Zu Wang.


texts: Confused on the notation from a TI datasheet

texts:
So I'm trying to implement this IC onto a controller that I'm designing: https://www.ti.com/product/UCC5350 I understand for the most part how to apply it, I am just lost on one key part

The specific point on concern that I have is the double vertical lines. I've never seen this notation and not sure what it's supposed to represent. Does anyone know what it is?
Thanks


texts: Im trying to understand different comparators. What is the difference between different LM339 ICs, especially between LM339D and LM339N?


texts: Regarding Return currents of the traces in PCB

texts:
This Question very basic and may be dumb question..

I remember for every trace a return current will flow exactly under it(minimum inductance path) or shortest path(minimum resistance).

I have a 2 layer board with GND on bottom and routes on top layer and GND Copper pour on Top layer.

When there is GND very near in the form of a copper pour for signal, why a signal will take only GND plane on bottom layer for return signal.( i assumed interfaces like SPI  max freq can be 40Mhz)


texts: Voltage regulator for linear constant-current (1.5A) LED driver?

texts:
I am considering building my own driver for a ~1.5A LED to power a microscope for my research.
For this application, efficiency isn't critical, but because exposure times to the camera can be short (~1ms), stability/lack of ripple is important. Thus buck/boost or other switching regulators, and PWM, are usually avoided here. (Perhaps suitable output filtering would sort this out, but <500ns [edit: <500 microsec] turn-on/off time is also highly desirable.)
What's the best current regulator for this set-up? (I'll be using a decent switching DC voltage source wall-wart to provide input power to whichever constant-current source I choose.)
One option would be to use an adjustable voltage regulator like a LM317 (but capable of handling more current, so maybe the LT1764 which also has a useful shutdown pin), set up in the standard constant-current mode where current is determined by a resistor between the Vout and Vadj pins. (The voltage between these pins is maintained at ~1.21V for the LT1764, so for 1A you'd want a 1.2-ohm resistor, and for 1.5A a 0.8-ohm resistor.)

(source: diyaudioprojects.com)
The other option might be using a new "one-resistor" voltage regulator like the LT3083, where the voltage is controlled by the resistance-to-ground from a single pin (through which 50 microamps is pushed by varying the voltage: so e.g. a 20kohm resistor induces a 1V output, and a 1-ohm resistor on that output will therefore cause 1 amp to flow).
Here there are two "suggested" constant-current circuits from the datasheet:
A constant-current source:

Or a lower-dropout LED driver

The nice thing about the LT3083 is that a 20-kohm potentiometer can be used to adjust current, unlike the LT1674, where you'd need a 20-ohm pot (rather harder to source) to adjust between ~.1A and 1.5A. But I'm not sure which of the two suggested driver circuits for the LT3083 would be more resistant to ripple from the input voltage source, if either. And I don't know if this is a bad idea for other reasons compared to the more standard regulators. (e.g. if the adj pin is left floating, it looks like the LT3083 will probably drive the voltage way up and fry the LED. So if the pot fails or a connection breaks, this could be bad news.)
So, anyone have suggestions for the best option?


texts: Calculating the pulldown resistance for a given MOSFET's gate

texts:
I searched and read many similar questions, but did not find a specific answer for how to calculate the correct value for a pulldown resistor for a MOSFET's floating gate. It seems like everyone dodges the question with a 1K, 10K, or 100K "ought to work".

If I had an N-Channel IRF510 and I was going to run the gate from 9V to switch a \$V_{DS}\$ of 24V at 500mA, what value should I use for the gate's pulldown resistor and how did you calculate that value?


texts: Why can't I get the output of a 74LS221 to idle at 5 VDC?

texts:
I have an industrial machine with an encoder feeding a Measurement Computing USB-CTR08 counter board.

In order for the board to count the pulses the counter's gate C0GT needs to be held at a positive level, basically 5 VDC. With the 74LS221 disconnected, if I connect C0GT to 5 VDC it counts the pulses as expected. Disconnecting 5 VDC to allow the 'COGT' input to float, or connecting it to 0 VDC, causes the count to reset to 0. This is desired behavior.

In the machine there is a homing lug that passes an NPN sensor that is connected to a Phoenix Contact solid state relay to convert the pulse from 24 VDC to 5 VDC. When the lug makes the sensor the signal drops to 0 VDC for a short time and this is passed on to the 74LS221 monostable-multivibrator. I am using this for a short duration one-shot.

In this configuration when the lug pulse goes low, a single 155 ns pulse is to be generated on not 1Q. This pulse is supposed to go from high to low. Causing the counter to reset and start over each time the machine is in home position.

My problem is that the idle output is only about 2 VDC.  I tried a 1K pull up resistor tied to 5 VDC, but it didn't make a difference.

The table for the configuration on the 74LS221 looks like this:

   Inputs     |  Outputs
Clear  A   B  |  Q     !Q
  L    X   X  |  L      H
  X    H   X  |  L      H
  X    X   L  |  L      H
  H    L   Up |  Up    Down
              | Pulse  Pulse
              |
  H   Down H  |  Up    Down    <- My configuration
              | Pulse  Pulse

simulate this circuit – Schematic created using CircuitLab

Additional info 9 Feb 2019

The counter board is a Measurement Computing USB-CTR08-OEM. The specifications on the reset gate in question:

Measurement Computing USB-CTR08-OEM Product Data Sheet

Input type: Schmidt trigger, 47K ohm pull down to ground with 33 ohm in series.
Schmidt trigger hysteresis: 0.76 V Typical, 0.4V minimum, 1.2V maximum.
Input high voltage threshold: 1.74V Typical, 1.3V minimum, 2.2V maximum
Input high voltage limit: 5.5 V absolute maximum
Input low voltage threshold: 0.98V Typical, 0.6V minimum, 1.5V maximum
Input low voltage limit: -0.5 V absolute minimum

I made another circuit using the original 74121 (note that it is not an LS part) that was used two years ago and it works. I'm assuming that a 74221 would probably work, but the LS version doesn't.


texts: LTSpice: How to vary resistances in a simulation depending on the value of a voltage?

texts:
I am trying to implement the Hodgkin-Huxley model for simulating neurons using LTSpice. One feature of this model is that the resistances at any given time actually depend on the transmembrane voltage at that time. Is there a way, in LTSpice, to change the values of resistors dynamically in a simulation?

I can find answers on how to vary the value of a resistor in pre-defined increments during a simulation. However, this approach will not work in this case, because I don't know these increments before the simulation starts. Rather, they must be recalculated dynamically from a particular voltage. Does LTSpice (or any other version of Spice, for that matter) have this capability?

EDIT: To be more specific about what the Hodgkin-Huxley model entails, the simulation code I need basically boils down to , where the g's represent the conductances, the E's are all constant voltages, gL is constant, and the other conductances all update according to :

where m, n, and h are state variables, and Vm is the transmembrane voltage (the voltage between Istim+ and Istim- in the above schematic). The alpha's and beta's are known functions of the transmembrane voltage.

In particular, I need to be able to keep track of the "current values" of the m, n, and h parameters during the simulation because the next value of these variables will depend on them.


texts: How to control 12 DC motors simultaneously with Arduino Uno?

texts:
I am using Arduino Uno.
I need to control 12 dc motors rated voltage 9V and current 150mA.
definitely, I will use MOSFETs and back emf diode for each PWM output.
I need to know whether I can use a 74HC4051 multiplexer to multiplex a single PWM output from Arduino to 8 channels so I can have 2 mux (8 channels) I get the above task done.
I do not have enough pins left in Arduino also I need to minimize the usage of Arduino digital pins that's why I am looking for multiplexing method

Is possible to use a 74hc4051 mux to multiplex PWM signal? PWM frequency will less than 200kHz

I need to control multiple motors same time as well


texts: Addition of 2 unsigned values in VHDL IEEE numeric_std : why this choice?

texts:
In VHDL, the IEEE numeric_std package does not behave as one could expect. The addition of two unsigned values coded on 8 bits is not given on 9 bits, but on 8 bits.

What are the reasons of this choice ?


texts: I am now learning avr programming using c. I have a problem with bitshifting. Suppose I have a 8 bit register named jcb containing 01110011. I want to get the upper 4 bits in vh variable. So, I do vh = (jcb >> 4). Now the value of vh must be 0111. But if now I do vl = jcb , what is the binary value containing in vl in 8 bit?


texts:
Is it possible to get KiCad to represent and then enforce (via design rules) the inclusion of copper pours? Something like this:-

I know it can be done manually at the layout stage, but can it be incorporated into Eeschema and the layout editor? If you have several pours/planes it all gets complicated. I can't find any suitable component in the schematic library, and clearly you can't have a predefined footprint. So there appears to be no way to capture a pour on the schematic, other than in my (unchecked) graphical manner. Is there a cheat?

Idea (feature request): Not great, but Eeschema could include a pour component like it has an oscilloscope component. And then the layout editor could enforce that the pour component has been at least associated with a copper pour (notwithstanding it's geometry).


texts:
I have a burglar alarm remote key pad.  It's a Honeywell Gen4, which is a good quality common unit in the UK.  Honeywell are not beginners at electronics.  It has a small SMD chip with about 20 pins that's probably an 8 bit micro controller.  Next to it is a shiny 8MHz crystal.    The are 9 traces like below scattered randomly about the PCB:-

This is approximately drawn to scale, and are about 7mm long.  What is it for?

These two images show the PCB:-

I don't think that this is a serpentine track for a high speed transmission line.  The PCB runs at 8MHz.  The folded tracks are all separate, not in pairs as differential lines might be.  They are all exactly 5 folds.  I'm not sure how they would reduce reflections from 1 - 50m long wires strewn randomly throughout a house, routed past mains cables.  They are covered in solder mask and on the back of the PCB, so they're not cheap landing pads for the push buttons.  Do not be fooled by the small switch in the middle of one of the images.  That's a tamper switch on the back of the PCB.  All the key switches are on the other side.  The tracks are however adjacent to various connectors where the alarm circuit wires are connected. Comms is 9600 baud so unremarkable. The board runs at 12V.

The panel is fully wired.  It is not wireless, so these are not antennae.

Before this gets marked as a duplicate, I don't think that this is for high speed operation as 8MHz isn't that high.  An Arduino runs at twice this rate, and doesn't have these.


texts: converting induction motor winding to reluctance motor winding

texts:
I want to build simple reluctance motor for education purpose. I have couple of small 3 Phase AC Induction motor with 24 slot stator lap winded for 4 pole design.

I want to convert it to reluctance motor, for that I will cast rotor of silicon steel with slots according to ( 24/16 ) design or similar.  But as I do not have much winding experience, I want to reuse the existing winding on stator with may be little rewiring of phase ( i.e. remove star / delta, and use all six wire to switching circuit. )

Can this work ? Is this concept possible to work ?


texts:
I'm interested in creating a custom linux based solution that will crunch sha256 cryptographic algorithms at insane levels of speed. I'm also on a limited budget...  I have no background in EE but I do w/ Software.  My question is custom ASICs have to be designed by some big company w/ some crazy fab process and takes a while.  Anything out there that has the low power consumption and high speed processing of an ASIC?  I read about SoCs and what looks to be hybrid type chips... i.e. - Zynq-7000   and this Parallella makes use of the same board/chip I believe.

Wondering if I can build something to produce tens of thousands of hashes per second. Even if I need to cluster them (at decent power and price constraints)

Thanks for any help. Currently reading research papers about ICs and everything, just don't understand how something economical yet powerful doesn't exist.


texts: What is the purpose of the sharp edges (aka mouse bites, aka perforated breakaway tabs) on the PCB?

texts:
I have received an NVIDIA Jetson board this week and it has the following edges near the mount holes:

I did a quick search on the internet but was only able to find similar edges on the Raspberry Pi Compute Module:

Could you please explain me why would you put those edges? I think it is for a better grip when mounted, but I fail to understand against which object the board will grip. Also, is there a standard for that, i.e. how do I design one for my boards in future if needed?


texts:
What is the maximum and minimum output on the Vout in differential amplifier circuit?
Is it Vcc and Vcc-R*I0?
And when does differential amplifier enter saturation?


texts: Transistor as a heater device and measured by LM35 temperature sensor?

texts:
The aim is to make a temperature control circuit using an Arduino Uno as a controller, an LM35 sensor as feedback to measure the actual temperature, a TIP31C transistor as actuator to control the power dissipated (heat.) I have a 12V,1A power supply.

Note: The transistor and sensor are near to each other.

I know that the Arduino Uno should send PWM through a resistor to the base of transistor, but what about collector and emitter?

Should I put 12V to the collector and ground to the emitter? But that would mean a short circuit.


texts: ESP8266-12E MicroPython Unable to access REPL (Python prompt)

texts:
I am trying to install MIcroPython Firmware on my ESP8266-12E chip. I am using esptool.py to flash the firmware. I have successfully uploaded the firmware esp8266-20170612-v1.9.1.bin followed by a flash_erase. I have used following commands to flash the chip.

$ sudo esptool.py --port /dev/ttyUSB0 erase_flash
  esptool.py v2.0.1
  Connecting........_
  Detecting chip type... ESP8266
  Chip is ESP8266
  Uploading stub...
  Running stub...
  Stub running...
  Erasing flash (this may take a while)...
  Chip erase completed successfully in 13.0s
  Hard resetting...

$ sudo esptool.py --port /dev/ttyUSB0 write_flash --flash_mode qio --flash_size detect 0x0 esp8266-20170612-v1.9.1.bin --verify
  esptool.py v2.0.1
  Connecting....
  Detecting chip type... ESP8266
  Chip is ESP8266
  Uploading stub...
  Running stub...
  Stub running...
  Configuring flash size...
  Auto-detected Flash size: 4MB
  Flash params set to 0x0040
  Compressed 598432 bytes to 390604...
  Wrote 598432 bytes (390604 compressed) at 0x00000000 in 34.5 seconds (effective 138.8 kbit/s)...
  Hash of data verified.

  Leaving...
  Verifying just-written flash...
  (This option is deprecated, flash contents are now always read back after flashing.)
  Flash params set to 0x0040
  Verifying 0x921a0 (598432) bytes @ 0x00000000 in flash against esp8266-20170612-v1.9.1.bin...
  -- verify OK (digest matched)
  Hard resetting...

As you can see verification of flash process is OK. And I can see a new wifi ssid on my wifi list.

Now when I am trying to access REPL via picocom it is hanging on following:

picocom v1.7

port is        : /dev/ttyUSB0
flowcontrol    : none
baudrate is    : 115200
parity is      : none
databits are   : 8
escape is      : C-a
local echo is  : no
noinit is      : no
noreset is     : no
nolock is      : no
send_cmd is    : sz -vv
receive_cmd is : rz -vv
imap is        :
omap is        :
emap is        : crcrlf,delbs,

Terminal ready

I also tried screen, putty and minicom same behaviour on them as well. Also encountered a strange behaviour that it is working perfectly via ESPlorer.

Is there anything that I am missing? Or any suggestion to hunt this situation?

Thanks


texts: Are gas bubbles ok in Flooded lead acid battery charging?

texts:
I Have HBL power system's 2cell 4.2v lead acid battery which has capacity of 12Ah for C/ 100 and 9Ah for C/10.

I found it in the rubbish     and thought it may useful and in working condition.I refilled it with dilute sulphuric       acid.

I charged it with smartphone charger at 5.06V at 400 to 500mA .When it is charging it produces very small bubbles of gas. I think I     am  charging it at   the gassing voltage.

Is it OK to charge it at 5V?
If not than its OK to charge it using LM317 at fixed safe voltage or just use small resistor? Or use a low drop P channel linear reg?


texts: Purpose of cylindrical attachments on Power Transmission towers

texts:
Attached below is an image of a Power transmission pole. What I am interested in is the cylindrical shaped objects attached to the transmission tower.

Some other observations and relevant information:

These objects are not present in every tower but on one in every few towers or so.

These towers are from a mixed Residential and commercial neighborhood

The towers in question are in Japan. I have not observed these cylindrical objects on similarly sized transmission towers in my Home country

A less relevant observation is that even though these are overhead transmission lines, they are insulated, perhaps because of the proximity of the houses and buildings to the towers
EDIT: There is a similar question linked here, however, this picture has both a single phase and larger 3 phase transformer while this earlier question had only a single phase one. Further, the question uses different terminology to describe the transformer (cylinder vs canister)


texts: Volume Control - Logarithmic Potentiometer Placement

texts:
Thanks in advance!
I am building an headphone amplifier with PCM1794A, OPA1612, and OPA1622.
Where would be the best placement of the logarithmic potentiometer for volume control without decreasing the bandwidth and without introducing a lot of distortion and noise?
My best solution was to add a small value potmeter at the output at VF3. Left channel below:


texts: active miller clamp and desaturation detection in mosfet drivers?

texts:
Newer mosfet/IGBT gate drivers like 2ED020I12FA and TD352 have features called : Active miller clamp and desaturation detection . However the example circuits are shown with IGBTs only.

So my Questions are :

1- Does Active Miller Clamp function work and have any significance when driving a Power Mosfet ?

2- Does The desaturation detection function work and have any significance when driving a Power Mosfet ?


texts:
I was reading about System on Chip on wikipedia and I was wondering

Is the iPhone an example of this?
Is the system saved on a processor?
How is the system actually put on the device?
Thanks!


texts:
After reading some answers on SuperUser, I started thinking: Can EE/E/PROM be damaged by only reading it, with no writing at all?

I've read several datasheets for EEPROMS and products that contain them and all I've ever seen were write and erase cycles. I do know that just reading few datasheets does not make me an expert, but up until now I was convinced that you can't wear out EEPROM and relatives just by reading them.

After some searching, I couldn't find a definitive answer which would convince me that reading an EEPROM can wear it out, so I'm asking here.


texts:
I have a sensor tag from Texas and have been able to communicate with it over BLE and get magnetometer readings using a node.js library.

However I am tough time going from the x,y,z mag. axis readings to being able to say NORTH, SOUTH, EAST, WEST. Any pointers in the direction would be of great help.

Thanks. :)


texts: Benefit of using RAM, or some form of internal memory on a FPGA

texts:
I am at moment trying to store an image onto an FPGA. I calculated the space required by it to be 19200 kb, and are therefor wondering whether i should store it some other way than a 2d array?..  Or does the program i create automatically store the image i create in the RAM.. And what is the benefit of storing it in the RAM...

I not quite sure why i would/should store in the ram, rather than store it as an 2d array, what benefit do i have..  It only going to be used for a look up..


texts: Problem stacking accelerometer and SD card shields on Arduino UNO

texts:
I have an ADXL345 accelerometer on a Makershield stacked on top of a Seeed SD card shield. Both of those are stacked on an Arduino UNO R2.

I've got each working individually, but when stacked they share pin 12. The SD Card shield uses 12 for MISO of SPI and the ADXL345 uses it for SDO/Alt address.

I'm new to Arduino and have not stacked shields like this before. I'm not sure what the best course of action is here to get them both working, Ultimately, I want to log the data from the accelerometer to the SD card, but first things first!

I'd be grateful for any help. I've linked the data sheets for the ADXL345 and the SD shield above.


texts:
This is a question from antenna book.I need to find entire pattern of a 5-element linear array that is equally spaced with  $$d = \frac{\lambda }{2}$$ ,uniform phase$$\theta  = 90$$ having triangular current amplitude distribution(1:2:3:2:1).

To find the entire pattern,we need to find array factor and element factor.
This is the entire pattern(answer).

I know the array factor of a 2-element array for this is $$AF = \cos \left( {\frac{\pi }{2}\cos \theta } \right)$$

How to find element factor?


texts: Need to isolate my ammeter (measuering and powering the unit from same power source)

texts: I have a problem and Im not sure what the best way is to address this. I converted an ATX PC power supply to use as a lab power supply I installed a digital volt meter and a digital ammeter. To power my meters I am routing a 12v wire and ground to my meters. I am also measuring my voltage and amps ( on the same power) with these meters. it works fine for the volt meter however my ammeter will not function properly this way. if I hook up my ammeter to a 12v battery then measure the current from my power supply it works but I dont want to hook up my ammeter to a separate power supply to use it. how can I isolate the 12v power to my ammeter to run the meter? I was thinking a 1:1 transformer but this is DC to DC so that may not work. maybe an optocoupler?


texts: How to convert from S-parameters to power gain?

texts:
With reference to the part below, which states 17dB gain at 500MHz for Vce = 12.5V

https://www.digikey.co.uk/product-detail/en/stmicroelectronics/PD55003TR-E/PD55003TR-E-ND/1664253

It's data sheet shows |S21| = 1.65,  S21∠Φ = 34 for Vce = 12.5V

How do I convert between the two parameters?


texts: What is the best approach to test a new PCBA?

texts:
So you went through weeks of schematic design and PCB layout design and Sent files over to fab house.
Now, you got the PCB from FAB house.
What is the first step you do when you get PCBA? What are typical tests tes that you follow for testing?
Assuming we have some sensors, some boost circuits, lipo chargers, antenna , MCU and I2C outputting sensors which have sensitive analog input on the board.
[EDIT] I hope the question is not to vague. intention here is to learn about best practices from people who are working industry for years.


texts:
I'm trying to capture a digital signal that consists of 8us HIGH pulses with 8us or 16us LOW pauses in between. There are additional LOW pauses of about 6ms (yes, ms) that separate data frames.
I'm looking to measure the time between rising edges, so I need to measure 16us and 24us intervals while not tripping over those 6000us pauses.
My first attempt was using the Arduino API attachInterupt in RISING mode, then getting the time with micros() in the ISR. That worked somewhat, but also produced lots of wrong data, probably due to interrupt latency. The CPU is also drawing a bit on the display over SPI, not sure if that matters.
As this looks like a good use case for Timer Input Capture, I'm now trying to use the Capture facility of MCPWM. The counter is clocked at 80MHz, which should be plenty of resolution. This is what I have so far:
namespace pins { enum
{
  pxx = 17,
}; }

volatile int measure[2];

static void IRAM_ATTR pxxIsr(void*)
{
  static uint32_t lastTime;

  auto now = mcpwm_capture_signal_get_value(MCPWM_UNIT_1, MCPWM_SELECT_CAP1);
  auto dt = now - lastTime;
  lastTime = now;

  measure[0] = dt;
  ++measure[1];
  MCPWM1.int_clr.val = CAP1_INT_EN;
}

void setup()
{
  mcpwm_gpio_init(MCPWM_UNIT_1, MCPWM_CAP_1, pins::pxx);
  gpio_pulldown_en((gpio_num_t)pins::pxx);
  mcpwm_capture_enable(MCPWM_UNIT_1, MCPWM_SELECT_CAP1, MCPWM_POS_EDGE, 80); // prescale by 80 to directly count us
  mcpwm_isr_register(MCPWM_UNIT_1, pxxIsr, nullptr, ESP_INTR_FLAG_IRAM, nullptr);
  MCPWM1.int_ena.val = CAP1_INT_EN;
}

The ISR is a bit condensed above, but that's all it does at the moment. measure[1] increases rapidly while the signal is connected to the pin, so I know the interrupt is working. measure[0] however is zero most of the time, with the occasional 6-digit number.


texts: Trigger Monostable 555 When Capacitor Raises above 0.5 Volts

texts:
So I want to trigger a monostable 555 to fire when a capacitor raises above 0.5 volts.  My plan was to use a Zener diode to bias an NPN transistor that would trigger the 555.  But I discovered the smallest zener voltage you can buy is 1.8 Volts.

Is there any way I can somehow bias the zener to react to a lower reverse voltage than its actual threshold?

-or-

Does someone have a better idea on how to get the 555 to trigger when intended?

ASIDE: I would also be satisfied with having the 555 trigger when the capacitor drops below 0.5 volts.  I don't think it matters to me if it's going up or down, just so long as I can make the trigger at the stated voltage (very close to zero).  The purpose is I'm trying to trip the 555 at some point where the cap is very close to zero volts.


texts: Needed someone to double check my boolean equation to my schematic diagram

texts:
I wrote out the boolean equations for each output but after {(AB)' +C}', I wasn't too sure if it was right. Thank you in advance.

This is the truth table that I made so far if the boolean match the circuit.


texts: Solar Panels Series / Parallel Switching Circuit

texts:
I am an electronics know-not-much :) I do understand the basics of current/voltage/amps etc.

I have an array of 10 x 15watt x 12v (max 17.5v) amorphous solar panels here in the UK. I want to arrange them in 5 banks of two (5 pairs) and when light levels are low (they are a lot in the UK especially during winter) I want to switch each pair from parallel operation into series operation. At the low light levels that exist during the long morning & evening periods and during heavy cloud the panels tend to produce 8-9 volts, which is not much use for charging, But if they switched to series operation, each pair then would produce a useful 16-18 volts. When the sun shines fully I want them to switch back to parallel so as not to over volt the charge controller.

My question is such a control circuit easy or difficult? I have searched & googled but cannot find such a control circuit..


texts:
I am designing a PCB that will incorporate a HiLink HLK-PM01 AC-DC converter.

The only AC that will be on my PCB is the two connections between the AC pins on the HLK-PM01 and a screw terminal header that I can connect the mains cable to.

I have these two traces in one corner of the board, and there is no copper within 8mm of these traces. I believe that keeping the traces away from ground pours and any signal traces is good, however as I would also like to know if there is an effective way to connect Earth directly to the PCB?

I was considering a small copper ring around the AC traces, that is earthed, so if for whatever reason a live voltage did jump across the board, the first thing it would find would be an earthed section of copper.

While I thought this sounded sensible, I can't find anything online that shows such a technique, and that makes me think it probably isn't a good idea.

So can someone tell me if there is an effective way to earth a mains section of a PCB to increase safety and reduce potential noise?


texts: How do I calculate the number of rotor and stator poles in AC motor?

texts:
I just started studying AC motors and I found myself in some trouble here. Basically the exercise asks me to calculate the number of rotor and stator poles in an AC motor, given the nameplate data.

Data:

Nominal speed: nn = 1440 rpm
Stator voltage frequency: fn = 50 Hz
Line voltage: Un = 380 V
Line current: In = 30 A

Basically I found out that:

The synchronism speed n1 = 1500 rpm
n1 = (60 * fn)/p => p = 2 for stator poles

My question is the following. How do I calculate now the number of rotor poles?


texts: I always wonder what screens are used as backgrounds during most of the stage performances? Most of them are as huge as 50ft high and around 100's of feet wide. I can assume they are LED screens but last year while I was looking for LED billboard I was told that it consumes a lot of energy and needs a dedicated transformer and are very heavy to keep transporting it from one place to another.


texts:
I am working with the Keil compiler in a project using the STM32F769I-DISC1. For debugging I use the ST-Link provided by the board. The idea is to use the on-chip DAC using TIM6 for triggering the output signal.

I need to debug the code and watch the DAC values so I am trying to configure the Logic Analyzer tool inside Keil. I have been looking some documentation but I am still not able to make it work.

I have been working with the ST-Link debugger until now and all the functionality seems to work fine, except the Logic Analyzer.

Here is the configuration:

and here the Trace options:

The clock is the same as my CPU clock.

The last option I tested was also to enable the Debug (SYS) from the STM32CubeMX configuration. But Logic Analyzer still doesn't work.


texts: What are these teardrop-shaped loops in power lines for?

texts:
I just happened to notice this along a road near where I live:

So these were in a pair, oppositely facing, "tip" to "tip" of the teardrop.
At first glance, this doesn't seem to be a bird diverter like here.
What is it for?
Note - I wrote "power lines" but I'm not actually sure what function this line has. Since its just one wire/cable, I didn't think it would be electrical transmission. Most other poles around here (rural) have a lot more on them than these do.

Minor addition - now that I'm looking for these, I'm seeing a lot of them in my area.


texts: Beginner trying to learn how to read start and end addresses for memory chips in hexadecimal

texts: I'm new to electrical (construction management student) and am trying to learn how to read start and end addresses. The practice problem I have been given is in the picture, and I was wondering how I would go about reading the start and end addresses of the entire section, as well as chips A and B in hexadecimal. The setup contains eight 2048x4 memory chips connected to a 16 bit address bus and 8 bit data bus


texts: Identifying quiescent current source in low power module

texts:
I designed a low power BLE modul with a nordic BLE SOM and I have some trouble with the quiescent current, when the Nordic SOM is sleeping, but also when the LDO is turned off by the undervoltage lockout IC.
From the current measurements, the quiescent current when the Nordic SOM is sleeping is around 180uA, when the undervoltage Lockout triggers and the LDO is turned off, the quiescent current is at 3.2V around 150uA and goes down linearly with the supply voltage. The measurement is correct and sampled with a Multimeter as well as the nucleo lpm01a dedicated low power current measurement board.
So, something draws me around 150uA and it is not the Nordic SOM in sleep mode, since the difference is only around 30uA when the LDO is on and off.
The button does not leak any current, since it is normally open. R15 from the PMOS is 100kOhm (verified) and should only draw around 4uA. So, the only thing that can draw that much current seems to be the LDO AP7365, but it should only draw around 37uA according the datasheet.
Has anyone an idea, what could be the cause of this high quiescent current?

Edit: So I desoldered R6 (ADC for battery measurement) and R15 (Pull-Up PMOS), but still I get around 130uA when the LDO is triggered off.
From the datasheet of the LDO, the shut down current is at most 1uA, so I really don't see, what could cause such a high current.
Edit2: So i finally identified the problem, it is the diode leakage current through D3. How can I prevent D3 to have such a high leakage current?
Solution: I use now a Si based diode, with a much smaller reverse current characteristic for the VUSB path.


texts: How come product makers tend to make their own boards rather than putting together modules?

texts:
It seems that most, if not all, companies that produce mass market goods use custom boards rather than putting together modules that are already available in the general market.

For instance, battery chargers use custom circuits rather than some module from aliexpress. Bluetooth speakers also tend to use custom circuits instead of a HC06.

Wouldn't it be more economical to put together existing modules than to build custom boards? Wouldn't that require lower development and testing costs?

Thanks


texts:
I'm doing a DSP project using the MSP430. I want to take an analog signal and convert it to a digital output using a microcontroller attached to an ADC on a DSP board. How would I program this in C?

  Input  -->  Output
 Analog  --> Digital
Digital  -->  Analog


texts:
I have a 900 watts transformer from a microwave, this used to have a secondary voltage of around 2000 volts (for the magnetron) but I removed it. I wonder if by using 15 turn secondary that will give 12v (each turn gives 0.8 volt, tested) instead I can create a 75 amp (as 12x75 is 900) transformer and what cable diameter I should use, also whether to use single conductor or multi strand cable. Primary is 285 turn and capable of the 900w aka 3.91 amps it would take to achieve this. I have considered using solid copper bar max 6.5mm squared(insulated) that will fill the space left by the secondary that I removed is that feasible? I plan to run it at max 230v 2.5A(fuse) primary aka 575 watts, and after a bridge rectifier a 600w(12v 15A max input)dc to dc variable voltage and current converter for maximum control in a DIY power supply.
Any advise on how I best can do this?


texts: Braided or stranded tinned copper for flexible connection?

texts:
I need a series connection between sets of batteries dealing with around 120A at 52V peak in an electric longboard. I expect the highest flex will be around 45 degrees, but mostly less than 20.

I think I have two options (please correct if wrong); I can use flat tinned copper braid in heat shrink or standard silicone stranded copper wire. Ignoring the height advantage of the copper braid, what other pros/cons are there for each choice in terms of current, wear due to flex, etc?


texts:
I'm looking into receiving data to toggle a led. The data would have to come from a microphone that picks up sound at inaudible frequencies transmitted by standard speakers (TV, PC).

I've looked at ultrasonic sensors but they work at 40khz instead, which cannot be relied on because the speakers might not support it.

Microphones ranging from 20hz to 20khz can be had cheaply. Looking at this page, it seems to put quite a burden to check the frequencies with Arduino timers. I figure there must be a simpler way to do it instead. Is there? Can I do it without an Atmel processor? I'm not very familiar with sound workings in electronics, so excuse my ignorance.


texts:
I need to produce about 200 Gauss magnetic field by power up a copper coil (as shown in picture) using 9V battery.

When I connected to 9V battery, Voltage across the coils are very low (~ 0.7V) and unable to give sufficient current to produce the magnetic field I wanted.

The Coil:

Turn = 120

Wire = AWG #16 (1.2mm Diameter)

Diameter = 8cm

Thickness = 2-2.5cm

Question:

I don't understand why the voltage become so low when I connected to the coil (Because of short circuit?)
How to increase my current (to 4 - 6A) so that I could produce enough magnetic feild.**

Thanks!

** Sorry for the missing info.


texts: Positive Definitness of Noise Covariance Matrix in Kalman Filter

texts:
I am reading a paper on Kalman filter and trying to understand measurement noise covariance and positive definitness of the covariance matrix. It is mentioned in the paper that if the matrix is positive definite then then no measurement is exact. I fail to see how is this the case

  The existence of the inverse matrices that appear in Kalman filter  equations  is  guaranteed  in  the  case  where  the measurements  noise  covariances \$R_k\$ are  positive  definite, denoted  by \$R_k > 0\$;  this  happens  in  the  case  where  no measurement is exact.


texts: Are my theoretical power consumptions of this avr correct?

texts:
After being inspired by a simple ATMEGA 168 based darkness alarm that has a theoretical life span of 3 years on batteries utilising sleep mode, I had decided to make something similar of my own (a wakeup alarm, using the oscillator for roughly okay precision rather than light)

My confusion is in the way the battery life is calculated (see the "Battery live time calculation" section) so I had decided to do my own calculating.

The AVR apparently at 1.8V in power down mode consumes 0.1µA. In active mode, 250µA assuming a 1MHz external oscillator (datasheet here).

Now a few (ideal maybe) AA batteries would have 1200 mAh, so

1200 / 0.001 / 24 / 365 = ~137 years standby life time
1200 / 0.250 / 24 / 365 = ~0.5 years active life time

Assuming my piezo buzzer + 10k series resistor for it takes 5 mA total, I could maybe average the current usage by hour

5mA * 10 (second alarm)? / 6 (intervals of 10) / 60 (in to hours) = ~0.138mAh
0.250mA (active current) * 10 / 6 / 60 = ~0.00694 mAh

End result being (ignoring that active power draw overlaps powered down status)..

1200 / (0.001 + 0.138 + 0.00694) / 24 / 365 = 0.9 years

Can you suggest major flaws in this? What would be a method to calculate all this current draw over time especially when batteries use mAh rather than Wh, and the data sheet only specifies "xx uA @ 1.8v" (and not ~4.5V I am using). Is there a simpler way to calculate power consumption when things only draw energy at certain periods (rather than my "average per hour" calculation) I've done?

I seem to have hit a wall at the theory side of the personal project. It just interests me how long it can run if I design it as simple as possible.


texts: How to make sawtooth wave from square or triangular wave?

texts: I know it is easy to convert a square wave to a triangular wave by an integrator. I know also that they can be made out of Harmonics but I don't know how to make a sawtooth wave form. Having a constant amplitude is also a concern ( 10Hz - 50MHz) and integrators naturally reduce the amplitude in higher frequencies. Is there any clean and standard way (especially any integrated circuit ) for this purpose?


texts:
I'm using MikroC Pro, PIC16F1824 with XTAL 4Mhz.

Basically I have 2 mode of LEDs. I use serial cable to send which mode to play.

Mode 1 = On for 3 seconds and Off for 3 seconds.
Mode 2 = On for 1 seconds and Off for 1 seconds.

Everything works fine and I use an interrupt. But when I send a new mode to play,
it waits until the current running mode is completed. It doesn't stop the current Mode immediately.

Questions:

How do I use interrupt to stop the current mode immediately (delay_ms) and play the new mode?
I was told I need to use counter looping. How does it work?

Code:

 void OnLed(short nMode){
if (nMode == 1)
{
    PWM1_Set_Duty(100);
    delay_ms(3000);
    PWM1_Set_Duty(0);
    delay_ms(3000);
}
else
{
    PWM1_Set_Duty(100);
    delay_ms(1000);
    PWM1_Set_Duty(0);
    delay_ms(1000);
}
}
void interrupt()
{
    cnt++ ;             // Interrupt causes cnt to be incremented by 1
    PIR1.TMR1IF = 0;    // Reset bit TMR1IF
    TMR1H = 0xFC;       // TMR1H and TMR1L timer registers are returnesd
    TMR1L = 0x18;       // their initial values
}

`void main()
{

...

T1CON = 1;          // Turn on timer TMR1
PIR1.TMR1IF = 0;    // Reset the TMR1IF bit
TMR1H = 0xFC;       // TMR1H and TMR1L timer registers are returned
TMR1L = 0x18;       // their initial values
PIE1.TMR1IE = 1;    // Enable an interrupt on overflow
INTCON = 0xC0;      // Enable interrupt (bits GIE and PEIE)

...

UART1_Init(9600);

...

while(1)
{
    if (UART1_Data_Ready())
      {
        sByte = UART1_Read();
        if (sByte = '1')
            OnLed(1);
        else
            OnLed(2);
    }
}


texts: Not sure if my calculation is correct, can anyone check this RC circuit for me?

texts:
Hello everyone, so in my book I decided to do this practice question but failed to notice that the answer was not given in the back of the book. If anyone can help me confirm my answer I would much appreciate it.

The problem asks me to find the current over the 5 ohm resistor as a function of time.
The initial condition is that the capacitor is charged to 5 volts. Top of the capacitor is positive polarity bottom is negative; should have put the signs in.

The answer I got to was the following:

$$
i_{R_{(5\Omega)}}(t)=\frac{(20sin(4t))}{(241)} + \frac{75cos(4t)}{241} + \frac{10}{3} - 2.6445e^{(-15t)}
$$

If the formatting of this post is all wrong please forgive me. This is the first post I've ever made on a stackexchange site!

The INCORRECT Work I did to get to the answer above

ANSWER

The question has been answered thanks to a reddit user!

Here is a link to the reddit post.

Here is a direct link to their solution.

Here is a direct link to the corrections I did to my work (marked in red).

Hope this helps anyone in the future!


texts: I am using ESP8266 (2.4GHz wifi) in my product which has metallic enclosure on outside but only plastic on the other side. I will be placing this device outside home near gate. Will it be problematic for the wifi to be in metal enclosure. (Plastic side will be towards the router). Do i need to put window or will it work without window?


texts: Can grid-tie inverters charge UPS batteries if connected to the UPS output?

texts:
If you have a UPS powering some load in an off-grid situation, and you have a solar panel with a grid-tie microinverter, is it possible to connect the grid-tie inverter to the UPS output, such that the microinverter assists with powering the load plugged into the UPS, and if there's an excess of power available, actually charge the UPS batteries?

I've read that it's possible with certain kinds of inverters, and that Tesla's "Powerwall 2" is apparently one of them.  It accepts power from grid-tie inverters on its output and uses it to charge its batteries, or if they are full to feed back into the grid.

I thought this kind of function would require additional circuitry to extract the extra incoming power, but from what I've read, it sounds like there are some inverter designs that inherently have this capability.

Is this true?  What sort of designs would work this way?  Is there any quick way you could tell whether a given UPS is capable of this, without getting hold of a schematic?


texts: what battery(s) do i need to power a 12 amp 200 mph motor for 1 hour?

texts: I have a plug in leaf blower/vacuum and would like to convert it to battery power. here is a link to the equipment in question. http://www.amazon.com/Factory-Reconditioned-Ryobi-ZRRY42110-Electric-Mulcher/dp/B004NC014Q/ref=cm_cr_pr_product_top?ie=UTF8. 12amp is its maximum output and i don't necessarily need it running that high but would like to know if it is possible to simply wire it to a 24v battery and still use it for at least an hour?


texts: Few doubts about turning an atx psu into a bench lab power supply

texts:
First, thank you for your time of reading my questions. As the title suggested, my questions are about turning a computer power supply into a lab power supply. I already did my homework and read pages and pages, and also tested the power supply unit itself while took great caution not to get executed by electricity doing so, yet I still have few doubts that I want to get a precise answers before moving on.

1, some say that it will explose; some say that it will be fine; some just doesn't really know. Will it be okay if there is no load connected to the psu? As far as I know, my tested unit didn't explose, but it could be an exception. I need to know this because I don't like the idea of a dummy load that wastes 5 watts.

2, I don't see manual switch, and I used to see those in older units. I love the idea that it's possible to switch the unit on/off using a simple signal. Here is my observation: With no load and with ps-on not connected to ground, after removing the power, I connect ps-on to ground while got a voltage reading on my meter for a brief moment. Here is my question: is the capacitor still hold a high voltage when ps-on is off after removing the ac plug? I think it probably is. The main doubt for me is when I connected ps-on to ground after the removal of the ac plug, will that discharge the lethal high voltage capacitor to a safe level?

3, I notice there are 2 small yellow pots on the board. I think it is use to change the voltage of 2 of the output. if I am correct, can I turn it as a variable voltage source?

4, I notice that there is a small blue capacitor connected between one ac input line to the ground/metal case (shield). I know it's for filtering high frequency noise, but is it safe for me to touch the metal case when I don't have ground connected to anything? Ac does go through capacitors and metal does go through me, I think. Interestingly, when measuring the voltage difference between that metal case and a water pipeline, it reads 65v ac, so it's not safe? should I remove that capacitor?

again, thank you for your time, and please have a nice day.


texts: modeling transfer function of ping pong ball levitation in a tube as a damper

texts:
I am building a control system to levitate a ping pong ball at a given height in a clear plastic tube using an arduino and implementing PID control.

I have to come up with a transfer function... I am using an air pump with pulse width modulation that controls the air speed, the pump is attached to the side of the bottom of the tube, and one end is closed and the other is open in the tube.

I was wondering if my idea would be correct, since one end of the tube is sealed and the other end is open, and the tube is a diameter that just barely fits around the ping pong ball, would I be correct in saying that to develop the transfer function for this system I could model it as a damper?

I was thinking it could be modeled as a damper or piston because the air forms a pocket beneath the ping pong ball and little air escapes around it?

I was looking up Bernoulli principle of lift, but not sure if a damper/piston would be the correct way in modeling this behavior?

If anyone could please shed some light on this I would be truly grateful!

or would it be easier to have both ends of the tube open? Not sure how the math would complicate for the transfer function in either case

Thank You!


texts: Calculate the electrical current density (international metric systeml )

texts:
I have a doubt about a result on a result. I have to calculate the electrical current density like $$\frac{\,\text{A}}{\,\text{m}^2}$$ I have the following parameters:
$$r=1\,\text{mm} =10^{-3}\,\text{m}$$
$$I=1\,\text{A}$$
so I have do this:
$$  j=\frac{I}{S}=\frac{1}{3.14\times (10^{-3}\times 10^{-3})} = \frac{1}{3.14\times (10^{-6})}=318471.3376\frac{\text{A}}{\text{m}^{2}} $$
Is this result correct?
Thank you


texts: What is the minimal schematic (needed capactiors/resistors) to use FPGA Altera Cyclone 4 EP4CE6E22C8N?

texts:
I can't find any information about how wire the Cyclone 4 FPGA.
I do not want to use development boards.


texts:
I have a project where I need to put a switch in between the resource from tester and the DUT.
My DUT is a 48 pin device (semiconductor IC), each of the pins has its own ESD diode. The switch, for example, can be an ADG1612.

FYI on my project :
I need to do a continuity test. It is to check if the DUT exists or is placed properly in the socket by measuring the DUT's ESD protection diode. The test method is to apply current and measure the voltage, expecting ~ 0.6v.

My tester resource has already shorted the Force and Sense pins, so there is no way to use Force and Sense to detect if DUT is place correctly in socket.

Since there is a switch in between resource and DUT, it will still get a diode measurement if the DUT does not exist because it is checking the ESD diode of the switch now.

For the DUT pin which connects directly to resource, it will get clamp value if there is no DUT connected or get a real diode measurement if the DUT does exist.

my question is:
Is there any switch on the market (from AD, TI..etc) that has a switch without an ESD diode? Or called a flying diode?
Or is there any switch on the market that will not affect/confuse the diode measurement?

Thanks!


texts:
Just trying to switch a relay when a comparator goes high with a transistor but the comparator outputs 1.3v when 'low' which is enough to set the transistor.

Using a 741 opamp as the comparator with a zener diode as one input and a pot providing the source for the other input. Positive rail is approximately 13v while the negative is 0v.
Obviously the positive side of the relay is connected to power, just isn't shown in the schematic below.

Is there a good way an easy way to fix this or should I be looking to use another chip with lower output?

Thanks!


texts: MSP430 USCI - Are the interrupt flags still active when interrupts are explicitly disabled

texts:
I am using an MSP430 USCI in SPI mode. I would like to confirm my understanding of this:

If UCTXIE and UCRXIE are explicitly disabled when the interface is initialized after UCSWRST is cleared the UCTXIFG and UCRXIFG should still operate as expected even though the interrupts are disabled, right?

From SLAU208M 35.3.8.1

  The UCTXIFG interrupt flag is set by the transmitter to indicate that UCxTXBUF is ready to accept another character. An interrupt request is generated if UCTXIE and GIE are also set.


texts:
I want to implement a PoE solution and I started to design the board based on WIZnet's W5500 reference designs. I am using the design with the external transformer.

My questions are:

How to adapt the schematic to use 2 pairs for PoE and be compatible with both modes of PoE? In DFRobot's Ethernet shield (see schematic at bottom of page), the pairs were filtered with an C-R-C network, but, correlating with WIZnet's schematic, should these components support 2kV? Also, for me it is not clear if DFRobot's design works in both modes of PoE.
I've seen RJ45 jacks with integrated magnetics and WIZnet gives a separate reference design which uses this type of jack. Can that design be adjusted for PoE? How?
I've found many types of jacks which integrates PoE magnetics such as:

MagJack SI-52008-F

Wurth 7499210121A

Why do some jacks, like Wurth, integrate diode bridges when PoE is DC? Also, see Silvertel's PoE 9600 module which integrates diode bridges.

In the schematic from DFRobot, a PoE PD interface and regulator circuit is used. Can't I just take the 48 V DC and use that voltage in a simple DC-DC converter? Why does such an interface is required?
Would it be better to use a jack with metallic enclosure, than a plastic one?
Would the PoE design work if I used a lower voltage, 5-12 V, instead of 48V?
Relating to the WIZnet designs, why does the center tap on the TX transformer, on the chip side, needs to be connected to 3.3V?

Thank you!

UPDATE
Thanks to your answers I managed to obtain a working design.


texts:
I am supposed to measure a battery's voltage, current and temperature for a project. And for this purpose i am finding an ADC module which can give me 12bits of resolution. However it should be having differential inputs, as i will be measuring the battery's voltage differentially (not referenced to ground), but the current and temperature would be measured single endedly . This ADC will be interfaced with Arduino (Leonardo most probably) to process the measured quantities. Also i want this ADC to have an external reference Voltage allowable so that i might provide it with an accurate reference voltage with some IC like MAX6161 (from maxim). I have visited companies websites, and tried to find ADC with my requirements, but i couldn't so far. Also i find some ADC's to be pseudo differential rather than just differential, and i read online about their difference, and i think differential would be needed in my case.  Can anyone please help me in this regard ?

So what i want in my ADC are the following :

1) At least 12 bit of resolution

2) 4 channel input (differential)

3) External reference voltage allowable

4) SPI interface (to microcontroller) (as ive read online that SPI is better than I2C in terms of noise senstivity if only one slave is to be connected with Master, which is my case)

5) A very good accuracy, i.e very low INL(<=1LSB), DNL(<=1LSB), Offset(<=4LSB) and Gain error(<=4LSB).

Thankyou.

B = Battery

C.S = Current Source

Xu = Voltage measured

Xi = Current measured


texts: Advantages of Isolated DC-DC Converter over non-isolated?

texts:
I am trying to understand in what type of situation I will need an isolated DC-DC converter instead of a non-isolated one. What are the design criteria that can lead one to one way or another?

In my case, I am looking at a Boost Converter design.


texts: Practical Limitations to 1-Wire Communication Speed

texts: What are some practical limitations to the speed of a 1-Wire interface?


texts:
I am using this large 24V power brick (rated for 9.2A) to power a small circuit (an arduino controlling some RGB LED strip, drawing less than 0.5A).

If I physically pull the plug out of the wall, the circuit runs on the transformer's stored energy for about a second before shutting down, which makes sense to me.

If the power supply has been plugged in for a long time, and I switch it off at the wall outlet, then the circuit continues to run for a very long time-- more than an hour-- before shutting down.  But if I physically pull the plug, it still shuts down in a second or so.

The switch on the wall socket is working correctly (tested with a desk lamp), and as I understand it, this switch interrupts the 240VAC live conductor.
The power supply connects to the live, ground and neutral conductors on the AC side, and on the DC side provides a +24V and an AC ground connection
Because I use an Apple laptop, I know the ground and neutral wires in my home are not at the same voltage

So, where is this circuit getting its power from when the live AC is disconnected?


texts: Checking interrupt flags for UART data receiving and transmitting on STM32

texts:
I'm trying to develop a UART receiver/transmitter for an academic project. For now i developed the UART continuous data receiving part and it works quite well. Here is the code:
Interrupt file:

extern volatile char RxData[10][8];
extern volatile uint8_t RxComplete;
extern volatile uint8_t RxCompleteOneRow;

extern volatile uint8_t ColumnRxBuffer;
extern volatile uint8_t RowRxBuffer;
void USART2_IRQHandler(void)
{
    //HAL_UART_IRQHandler(&huart2);

        if(RowRxBuffer < 9)
        {
            if(ColumnRxBuffer < 7)
            {
                RxData[RowRxBuffer][ColumnRxBuffer] = (uint8_t)(huart2.Instance->DR & (uint8_t)0xff);
                ColumnRxBuffer++;
            }
            else
            {
                RxData[RowRxBuffer][ColumnRxBuffer] = (uint8_t)(huart2.Instance->DR & (uint8_t)0xff);
                ColumnRxBuffer = 0;
                if(RowRxBuffer == 0)
                {
                    RxCompleteOneRow = 1;
                }
                RxComplete = 1;
                __HAL_UART_FLUSH_DRREGISTER(&huart2);
                RowRxBuffer++;
            }
        }
        else
        {
            if(ColumnRxBuffer < 7)
            {
                RxData[RowRxBuffer][ColumnRxBuffer] = (uint8_t)(huart2.Instance->DR & (uint8_t)0xff);
                ColumnRxBuffer++;
            }
            else
            {
                RxData[RowRxBuffer][ColumnRxBuffer] = (uint8_t)(huart2.Instance->DR & (uint8_t)0xff);
                ColumnRxBuffer = 0;
                RxComplete = 1;
                __HAL_UART_FLUSH_DRREGISTER(&huart2);
                RowRxBuffer = 0;
            //  tick = 0;

            }
        }

    return;
}

UART Config:

static void MX_USART2_UART_Init(void)
{

  huart2.Instance = USART2;
  huart2.Init.BaudRate = 9600;
  huart2.Init.WordLength = UART_WORDLENGTH_8B;
  huart2.Init.StopBits = UART_STOPBITS_1;
  huart2.Init.Parity = UART_PARITY_NONE;
  huart2.Init.Mode = UART_MODE_TX_RX;
  huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart2.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart2) != HAL_OK)
  {
    Error_Handler();
  }

  __HAL_UART_ENABLE_IT(&huart2, UART_IT_RXNE);

}

The device needs to send some data over UART in non blocking mode, so i tryed to modify the code, using some if statement to check if the interrupt is generated from the incoming data or the completed transmission.

To do so i used if(__HAL_UART_GET_IT_SOURCE(&huart2, UART_IT_RXNE)) and if(__HAL_UART_GET_IT_SOURCE(&huart2, UART_IT_TC)) in the interrupt handler and adding __HAL_UART_ENABLE_IT(&huart2, UART_IT_TC); in the config function.
Doing these modification the micro doesn't even start: it goes in an unknown state and remain stuck to it. Debugging the code step-by-step i noticed that the micro goes to this unknown state when it tries to turn on a LED, which is the first thing that does this code. If necessary i could upload the entire code.

What am i doing wrong?

For sake of readability, here it is the modified code that i mentioned before https://pastebin.com/qhS2JjLm


texts: Transponder pulse signal width measurement

texts:
As we can see in the following link: http://www.radartutorial.eu/13.ssr/sr06.en.html

SSR interrogations formats are differed by pulse width and spacing between them.

How is this measurement done in the circuit level? Can this be done by an ADC or microcontroller or is it done by software?

So, how do we identify if it is one kind of interrogation or another?


texts: By increasing the size of the piezoelectric ceramic disc used in ultrasonic humidifier, does it increase the amount of mist generated?

texts: I'm fairly new to piezoelectricity and I have managed to research online on how ultrasonic humidifiers work. However, there has been very little mention on the size of the piezoelectric ceramic disc affecting the generation of mist. Will the amount of mist generated be the same or will it be different considering that only the size of the ceramic disc is changed?


texts:
Is resistance what makes a diode have a voltage drop?

Or is it impedence?

If it is electrical energy being converted to light, please tell me what this effect is called.


texts: Build a High-Voltage High-Frequency Power Supply

texts:
I need to build a HV HF power supply to ionize gas. The specifications are 12V input voltage and 10kV output voltage @ 13.56MHz. I know this is not an easy task at all, since in this frequency area, all the paracitic capacitors and inductors have to be taken into account.

What I have tried to simulate yet is:

1.) Slayer Exciter: The problem here is, that the resonance frequency mostly depends on the parasitic capacitors and I don't reach such an output frequency at all if I want to use electrodes with a capacitance of some nF.

2.) Royer Converter:I tried to simulate the behaviour of a Royer Converter, but also with an output capacitance of a few pF, the frequency comes not in the needed range.

3.) Flyback Transformer: Most people use flyback transformers to generate high voltage for ionizing gas, but I think this would not work at all at this frequency, since the transformer is saturated.

Has anyone an Idea how this could be done, or is it impossible from 12V? If it's nearly impossible, has anyone a suggestions what could be done to generate this 10kV at a high frequency as possible.

Edit: I simulated now the class-E amplifier circuit and the switching behaviour works fine. The problem is, that I cannot put the input voltage too high to achieve a high output voltage, especially also because of the MOSFET. How could I go from here to increase the voltage to 10kV AC? Tesla magnifier? Another problem is the huge input power of around 1kW.


texts: What kind of wire-to-board connector is this?

texts:
It has a pitch of approximately 3.9 mm. Pins are 1.1 mm square. On the board there are 2 and 3 pin versions of this connector.

Here are a few pictures:


texts: Stability of saturated amplifier and overdrive recovery

texts:
I have two questions. First paragraph is background, second is questions.

Background:

I have a photodiode amplifier (low capacitance APD + fast transimpedance amplifier) that has a nice response with small amplitude light pulses. It has good phase margin and there is no overshoot.

When I increase the amplitude of the incoming light pulse, the amplifier output will get close to or hit the rail, and I get overshoot and ringing.

Questions:

How do I analyze amplifier phase margin with a large signal response that may saturate the amplifier?
How do overdrive recovery circuits work? I can't find any reference to overdrive recovery in my Gray & Meyer book. Where can I learn more about overdrive recovery?

Thanks


texts: Does a multi-speed fan operate at a different wattage at different speeds?

texts:
This question has been phrased to be a non-use, theoretical question on electrical design, as it has always been intended. Note to moderators: please be careful editing or re-phrasing to reduce the risk of this becoming a usage question.

Will an AC electric fan with discrete speed settings draw less current at lower speeds or will it simply be less efficient, producing a higher percentage of waste heat and a lower percentage of kinetic energy?


texts: Understanding USB processing and polling delay in USB host controller

texts:
I am doing measurements related USB delay with USB-UART converter chip(CP2102 Silicon laboratories chip). I am sending array of data, when 0xee is received the microcontroller will echo the byte. I am taking time stamps between instant i start sending the data to until I receive the 0xee. To find out the processing time at CP2102 chip I have measured chip ack delay(It is the time between point packet to the instant ack packet received from the chip). USB-UART chip is bulk device with two end points(IN and OUT)max packet size of 64 bytes, USB2.0 full speed usb(12Mbps) is used. I am taking 500 samples for each data size(1 byte sent 500 times and measurements are taken, similarly 2 bytes until 127 bytes).

I have plotted three graphs one for total_delay, chip_ack_delay and total_delay_without_uart_delay_chip_ack_delay =  total_delay - chip_ack_delay - 86.6*data_size This delay should represent processing delay and USB polling delay at the host computer. I am using Linux PC with Ubuntu 16.04, UART baudrate is 115200(hence 86.6 microseconds per byte). It is understandable that chip ack delay increases as packet size becomes more than 64 bytes since it has to wait for two transactions. I am not able to interpret second plot It is showing host side polling and  processing delay decreases as packet size becomes more than 64 bytes, Can someone explain how to interpret this? Or Am I missing something here?

By the way, I measured chip ack delay using USBmon log. In the graph x-axis is data size, y-axis is MATLAB boxplot shows the range of values of delay measured  for particular data size.


texts: I2C Communication to the Matlab from Sensor board(8051 µC)

texts:
I like to connect my board to Matlab through I2C communication(I2C-USB cable).
Is there any library or example scripts in matlab to do it?
What are the procedure to do it.

for example, I connected the device with uart with this code

properties (SetAccess = protected)
        sp
        baudRate
        dataBits
        stopBits
        parity
        flowControl
        terminator
        timeout
        port
        waitTime

    end

    methods

        function obj = Dev(comPortName)
            %% Dev constructor for initializing device object properties

            % INPUT PARAMETER
            % * comPortName     - name of the com port (e.g. "COM1")

            % OUTPUT PARAMETER
            % * obj             - initialized device object

            obj.sp          = serial(comPortName);
            obj.baudRate    = 115200;
            obj.dataBits    = 8;
            obj.stopBits    = 1;
            obj.parity      = 'none';
            obj.flowControl = 'none';
            obj.terminator  = 'LF';
            obj.timeout     = 2.5;
            obj.waitTime = 1;

            set(obj.sp, 'BaudRate', obj.baudRate);
            set(obj.sp, 'DataBits', obj.dataBits);
            set(obj.sp, 'StopBits',obj.stopBits);
            set(obj.sp, 'FlowControl',obj.flowControl);
            set(obj.sp, 'Parity',obj.parity);
            set(obj.sp, 'Terminator',obj.terminator);
            set(obj.sp, 'Timeout',obj.timeout);
            %set(obj.sp, 'waitTime',obj.waitTime);

            obj.port = comPortName;
        end

similarly, is there a possibility to connect through i2c communication?

Response greatly appreciated.
Thanks


texts:
I would like to split yellow RCA cable (because I need 2 input cables for 2 tvs/monitors). And do the same for S-video cable.
Can I use cheap simple "splitting" cables with one input and two outputs for this? Many thanks.


texts: What are the considerations for PCB layout, and connector selection for video signals. Is it necessary to follow 75ohm impedance criteria in a closed system. The pipeline starts at Sony FCB IX 11 A camera core which outputs VBS 1V p-p NTSC signal with no impedance specifications, goes to a processing board (TI processor based), and outputs as a same specification video signal. I do not have real estate budget to accomodate 75 ohm RF connectors in the design and was wondering if I could work with Micro D connectors, and treat video as just another analog signal. The output is not to be transmitted over lengths more than 2 feet.


texts: Design of "simple" 1000W AC motor/ heating element controller

texts:
I have been working on designing a circuit which can reliable control the on/off cycles of a 1000W (vacuum cleaner) Motor and a 1000W Cartridge heating element. It should be noted that the motor and heating element both have an separate circuit. The circuit is as follows:

It works as follows:

The circuit is designed for 230V Mains
A micro-controller (ATMega328) will detect the zero crossing of the grid and decide whether to turn the motor/ heating element on or off for the following period.
If the triac must be fired, PD4 will be pulled to high, triggering the photo triac, which will trigger the BTA208S-800E Triac.
The snubber networks consisting of the resistors/ capacitors are supposed to protect the Triacs from misfiring.

Though, there are a few unanswered questions I would like to ask: First, the motor causes a lot of noise on the grid, does the snubber filter this unwanted EMI or would it need separate filtering (what/how)?

In the datasheet of the BTA208S-800E I found that the thermal resistance from junction to ambient is: 75K/W. How do you calculate the amount of Watts dissipated in the Triac? I plan on using a copper ground plane as heat sink.

Most European wall outlets have 2 pins for the power and a separate for earth. Can I connect the earth wire to the enclosure where both the heating element and motor are placed in?

Last, I would like to detect if the motor is not malfunctioning (if it is, both the heating element and motor should be shut down). I was wondering if detecting this would be possible by monitoring the back EMF caused by the motor?


texts: Why is my RGB LED strip passing current through the transistor?

texts:
I am following this schematic: http://www.electronoobs.com/eng_arduino_tut13_sch2.php

It uses a BD140 PNP transistor. I checked the wiring was correct. Basically, the transistor boosts the current when I set the Arduino PWM pin to 0 and should dim the LEDs when I set it to a value of 255. (PWM pins connect to a resistor and then to the body of transistor)

However, I noticed the blue is almost off, while the red and green are just sorta dim when I set all three pins to 255 (turn off or almost off). I'm guessing the blue just uses more current and that explains why I should use more resistance values on the red and green LEDS.

I also want to simulate this on LTSpice to explain what is going on but I'm not quite sure how to simulate a PWM voltage or the RGB LED strips.

I was thinking of just adding 500 ohms to the blue, and 1k to red and 1k to green, based on the brightness I see.

Any advice on how I can accurately determine the resistance needed to turn these LEDs almost off without just incrementally guessing?

Additional info: when the arduino is off but the power supply still supplies 12v to the rgb led strip, it is in full brightness for all 3 colors.


texts: How would you combine DC power, bi-directional serial data, and an RF signal on a single 50-Ohm coax feedline?

texts:
I would like to power a remote device and communicate with it over some serial protocol on the far-end of a 50-Ohm coax feedline (RS232, i2c, SPI, etc), while at the same time sending/receiving an RF signal (144-148MHz ham band).
A bias tee is simple enough to get power down the line, but how could I add serial communications?

Are there existing components or ICs to facilitate such a data encapsulation?
What bitrate can you achieve?


texts: Designing a MOSFET circuit for low pass filtered PWM operation and with saftey considerations

texts:
I am designing a circuit at the moment and, as part of that, I need to be able to run 4 12VDC fans (which i will run in parallel) with an operating current of 150mA and a starting voltage of 4.5V. My problem is that my supply rail is 24V.

At the moment I am thinking of using a 5V PWM signal from my microcontroller to control the gate voltage of a MOSFET. With a 50% duty cycle, I should achieve an average votage of 12V. However, PWM is noisy and it would be nice to be able to smooth the output voltage with a Low pass filter. It would be nice to put the filter between the micro and the MOSFET gate, I just have to make sure that the gate voltage is above the threshold voltage.

Here's my question: is something like this suitable? Also, how do I protect against anything that might go wrong? For example, if the fans short etc, I don't want to start a fire if the MOSFET is dissipating high amounts power.

Here's my thought process for choosing the MOSFET

\$V_{GS(th)}\$  =  \$0.67 V\$ which is greater than the expected 'off' voltage from my PWM pin
\$V_{GS(max)}\$ is \$8V\$ which is less than my \$5V\$ max PWM output
Max continuous drain current is \$6.3A\$ which is greater than my 4 fans ( \$4 \cdot 0.15 = 0.6A\$)
With \$V_{GS}\$ at 2.5V (5V at 50% duty) I can supply over 20A. I don't understand this bit because the datasheet says a max Drain current of 20A pulsed. I guess that I can only do this for a very short amount of time?)

Max \$V_{DS}\$ is 30V, greater than my 24V
\$R_{DS(on)}\$ is  typically 0.038Ohms at 4.5V gate voltage. At (\$4\cdot 150mA =\$) 600mA power dissipation is 22.8mW which I guess is low enough.

Here's my Schematic. What can I do to improve it and/or protect against anything that might go wrong?


texts:
Lets say we have a circuit and we find the G parameters for the two port model. Then for that same circuit, we find the Z parameters.
If we arbitrarily set I1 and I2, could we calculate the same V1 using either model? Would that V1 be equal?
I have written V1 in terms of I1 and I2 on the right, from the g parameters. And on the left is the Z parameter equation for V1.
My goal is to broaden my understanding of what these models mean. I had been thinking of these as simply different ways to relate what goes in and out of a black box but perhaps not?


texts: How do I use this VFD from Futaba with an Arduino?

texts: I salvaged this display unit from an old VCR about 20 years ago. Since then, it's been lying in my electronics box. Now I would like to play around with it on an Arduino. I can't find the datasheet for this VFD online. I've never used a VFD before, so this is completely new ground for me. Any assistance would be greatly appreciated.


texts: BUCK converter considerations in a battery charger,with battery as a load

texts:
What are the essential considerations of a BUCK converter with a battery(lead-acid) as a load?
Here are some basic questions which i need some clarification:

1.Is it better to use a synchronous buck(free-wheeling diode used) or a non-synchronous buck(free-wheeling diode replaced by a FET)?

2.Is there a requirement of the output capacitor,as the battery itself would act as a large capacitor in this case.

3.Assuming that the step-ed down voltage is always greater than the battery voltage,How to calculate inductor value which would ensure continuous current flow from the BUCK to the battery,in order to charge it.

4.Would it be better to user a low side shunt or a high side shunt to monitor charging current.


texts: Would an analog mux be able to output various voltages?

texts:
So from my understanding, an analog mux such as CD74HC4067E will be able to output diferent voltages based on its inputs.

Thus for an example if I connect 4V, 3.3V, 2.2V and 0V to a 4:1 mux with 00, 01,10,11 being the selectors for each of the above voltages respectively. What would it output if I select 10?

My understanding is that it should output 2.2V or whatever is connected to that corresponding channel. Sorry for the basic question, I just want to be sure before I buy the chip.


texts: ERROR:Xst:827 - while synthesizing the code

texts:
I 'm trying to synthesize the below code using Xlinx ISE 14.3 but I get below error.I could simulate it successfully.Please help as I'm a newbie in VHDL.

  ERROR:Xst:827 - "D:/programs_xlinx/BZFAD/DFF.vhd" line 42: Signal Q cannot be synthesized, bad synchronous description. The description style you are using to describe a synchronous element (register, memory, etc.) is not supported in the current software release.

Below is the code.

Entity DFF is
  Port (
    reset : in STD_LOGIC;
    clk   : in  STD_LOGIC;
    D     : in  STD_LOGIC;
    Q     : out  STD_LOGIC
  );
end DFF;

Architecture Behavioral of DFF is
begin
  process(clk,reset)
  begin
    if reset='1' then
      Q <= '0';    -- clear register
    end if;
    if (clk'event and clk='1') then Q<=D; --positive edge of clock is used
    end if;
  end process;
end Behavioral;


texts: How to differentiate a control path signal over data path signal?

texts:
I'm really new to digital systems. I'm trying to understand the difference between control path and data path. As far as I understood data path is where all the operations regarding ALU and registers happen. In control path we basically controls the above mathematical operations and etc.

Imagine I have to make a simple block diagram of a system which does parallel to serial conversion. The operation is as follows

The conversion shall be started when a signal ENABLE is asserted for one clock cycle.
an output signal READY is asserted when the module is ready to accept new values.
an output signal DONE is briefly asserted when the conversion has been completed. Now I tried to add the above signals as input and output signals to the below block diagram which specifies it's control path or data path. Did I understand it correct? If it's wrong please explain it to me.


texts: Low voltage power "distribution" board design

texts:
I got a cheap 12 volts power supply (this one specifically) which I want to distribute to several CMOS CCTV cameras (such as this one) which are spread around the house (15m max. distance).

Normally you would connect each camera via its own power supply to the mains, but since I don't have a lot of space for all these individual power supplies, I thought of creating a "power distribution" board with nice connectors to connect all individual cables to the single powerful supply mentioned above.

Now, obviously connecting them all in parallel worked when I tested it, but for a permanent solution I was wondering - should I add some protection to the circuits? Inverse polarity / overdrive / surge etc.?


texts: What methodology to build an electronic system?

texts:
Electronic engineering is not my field but I enjoy build some very little electronic circuits for fun. When I try to build something, I have no methodology at all: I try, fail and try again until my circuit does what I want.
I think it is not an efficient way to produce things (even if it is interesting to learn new stuff). That's why I'm wondering if there are methods that can be used to build an entire electronic systems just from a set of requirements. What are the steps? How to choose the best components?


texts: When to bias diodes in double balanced ring mixer?

texts:
Do I need to bias up the didoes in a double balanced ring mixer?

Some diodes have turn on voltage at 0.3V, and some turn on at 1.2V. If LO power is about 5dBm (~0.6V peak voltage), I would need extra bias if the diodes I choose has turn-on voltage of 1.2V. Am I correct?

If so, where should I add the bias, I am confused now.

Thanks.


texts: How can I adequately recreate a signal with a biphase line code after band-pass filter in python?

texts:
I want to create a python model of a transmitter. The transmitter uses a biphase line code, which looks like this (from a datasheet):

Additionally, the datasheet states that the signal is "passed through a bandpass filter which conditions the signal for the line by limiting the  spectral content from 0.2 fBaud to 1.6 fBaud <...> The resulting transmit signal will have a distributed spectrum with a peak at 3/4 fBaud."
The resulting pulses at the actual transmitter output look like this:

How can I adequately reproduce this resulting signal shape in python?
What I've tried:

Put square pulses through bandpass filter: I would expect it to give me the desired result, but I couldn't figure out the correct implementation.
Imitate the pulse shape by combining sine waves with different frequencies: it looks very similar in comparison with the actual signal, but it doesn't feel adequate.

Results:

Python code:
import numpy as np
from scipy import signal as sig
import matplotlib.pyplot as plot
from random import randint
from math import sin, pi

data_f = 16 * 10**6             # freq of samples
symbol_f = 320 * 10**3          # freq of symbols
T = int(data_f/symbol_f)        # period of symbols

N = 15                          # number of symbols

# sequence of random numbers
symbols = np.zeros(N, dtype=np.float32)
for i in range(N):
    value = randint(1, 2)
    if value==1: symbols[i] = -1
    elif value==2: symbols[i] = 1

# bi-phase line coding
biphase_symbols = np.zeros(2*N, dtype=np.float32)
biphase_symbols[0] = symbols[0]
biphase_symbols[1] = -biphase_symbols[0]
for i in range(1,N):
    if symbols[i] == symbols[i-1]: biphase_symbols[i*2] = biphase_symbols[i*2-1]
    else: biphase_symbols[i*2] = -biphase_symbols[i*2-1]
    biphase_symbols[i*2+1] = -biphase_symbols[i*2]
N = 2*N
symbols = biphase_symbols

# Option 1. Square pulses with band pass filter
signal1 = np.zeros((N*T), dtype=np.float32)
for i in range(N):
    signal1[T*i:T*i+T-1] = symbols[i]

nyq = 0.5 * data_f
lowcut = 0.2 * symbol_f / nyq
highcut = 1.6 * symbol_f / nyq
order=6
sos = sig.butter(order, [lowcut, highcut], btype='band', output='sos')
signal1 = sig.sosfilt(sos, signal1)

# Option 2. Combination of sin waves
signal2 = np.zeros((N*T), dtype=np.float32)
i = 0
while (True):
    if i>= N-1: break
    if symbols[i] == symbols[i+1]:
        for j in range(2*T):
            index = T*i+j
            signal2[index] = symbols[i] * (sin(pi*j/(2*T))+sin(3*pi*j/(2*T))/3)
        i+=2
    else:
        for j in range(T):
            index = T*i+j
            signal2[index] = symbols[i] * (sin(pi*j/(T)))
        i+=1

fig,myplot = plot.subplots(2, 1)
myplot[0].plot(signal1)
myplot[0].set_xlabel('Time')
myplot[0].set_ylabel('Amplitude')
myplot[0].grid(True)
myplot[1].plot(signal2)
myplot[1].set_xlabel('Time')
myplot[1].set_ylabel('Amplitude')
myplot[1].grid(True)
plot.tight_layout()
plot.show()


texts: Is XOR equal to XNOR when odd number of inputs are considered?

texts:
I was attempting a question which said that you can convert a Full Adder into a Full Subtractor with using just one inverter. Later I researched on this XOR and found that that for even no. of inputs it is the invert of XNOR and for odd number of inputs it is equal to XNOR. Is it true?
Also Can we say that the XOR gate gives true or 1 value only when there are odd numbers of 1 in the input.


texts: Can't get any output in LCD with 18F2550

texts:
I have made circuit of contact less tachometer using PIC18F2550 micro controller. when I testing my circuit I cant get any output on LCD. But the LCD is turn on. I check all the connections one by one. Actually I cant get the helloworld output in my LCD also. The helloworld program and the tachometer programs have compiled successfully in mikroC and had desired output in proteus.So what can cause this problem.help me.

Microcontroller circuit

helloworld program

tachometer program


texts: Can anyone tell me what are these smt devices. Especially the one with square drawn at centre


texts: Small detail about the super diode circuit that bugs me

texts:
I was going over the super diode circuit and I was trying to solve it for a particular case as shown

simulate this circuit – Schematic created using CircuitLab

I understand that we must assume initially assume that the op amp is closed loop gain, because of the diodes. V1=0, so there is a current coming from the voltage source. I know that all the current is going through the D2 diode, because if it went through the R1 resistor to Vo, the D1 diode would be in reverse bias and wouldn't allow any current to Va which would contradict our initial assumption that the op amp is in a closed loop.

My question is where does the current go?there is 1mA current going through D2.Since we now know that D1 is off, and there is no ground, my only other guess is to the output terminal.
It might seem like a dumb question that I should already know how to answer, but from how I understood it up until now, since no current goes through the input terminal, it has to go through the loop, but now that I think about it, it doesn't really make sense because the op amp is the one that is supposed to produce the current in the first place, isn't it?


texts: How does the Colpitts Oscillator reach a loop gain of 1?

texts:
How does the Colpitts oscillator reach the loop gain \$A_V*B\$ of 1?
The loop gain started >>1 (oscillation builds up) but it eventually reaches a state where loop gain is equal to 1(oscillation stabilises). Since feedback is constant \$\frac{C_1}{C_2}\$, it seems to me that \$A_V\$ self-adjusts to the reciprocal of \$B\$. How does that happen?
And why this is only possible to LC oscillators and not to RC oscillators(for example a Wien-Bridge oscillator will not automatically adjust its own loop gain to 1 without using external components like tungsten lamp)
This is the Colpitts oscillator:


texts: Measuring volume with eTape Liquid Level Sensor + Arduino

texts:
I have the 12in Tape Sensor and an Arduino Uno. I'd like to get use this to measure volume in a cup. They gave me a resistor and a little connector for the 4 pins with the sensor, and I have some wire and a Multimeter.

I am really unsure of how to do even this very basic thing. I would like to extend this into a more useful hack, but right now I'm trying to get basic functionality. In this video, it looks like they're literally just connecting two ends to the multimeter and that works. I have 4 pins though.

Where do I begin?