texts:
I am experimenting with a stripline square spiral inductor in Sonnet and the graph is showing both a positive and negative inductance.
What does it mean to have a negative inductance?
Why does it swing above and below 0?
What does it mean about the inductor that the negative spike is 2x greater than the positive spike?


texts: I am searching for a linear regulator with tab connected to GND instead of Vout because it would be easier for thermal management. Unfortunately, all linear regulators seem to have their tab connected to output. Is there any linear regulator with tab connected to GND ? Thanks a lot.


texts: What Reference-Potential does an Operational Amplifier use as "Ground"-Potential?

texts:
Wikipedia states on operational amplifiers, that, simply speaking, they provide an output voltage at their output which is the difference of the two input voltages, multiplied by some (very very large) number.
Since voltages are just electric potential differences, I'd like to know what point in the circuit is the reference point for the output of the operational amplifier?

For the inputs, it essentially doesn't matter. Since the behaviour of the operational amplifier only depends on the difference of the two inputs, it doesn't matter what ground they correspond to.

My simplest guess would be that the output voltage of the operational amplifier has the same common ground all the other devices in the electric circuit have. In that case: How does the operational amplifier know of this common ground, if it doesn't have a connection to the common ground?

I need to know what the reference point is to even make any sense of the statement "the output voltage is A times the input difference". If I don't know what the reference point is, then the output voltage is just a number without meaning.


texts:
Trying to make second circuit.

Here is my outputs

(source: cs608722.vk.me)

In1+ connected to ground, OUT1 blue and after diode red

In1+ signal red and Out2 blue

(source: cs608722.vk.me)

Why cap charges if there is no signal.. Capacitor is 0.1uF
Plot's data is from Arduino, 5V-1023 0V-0
LM324 supply from arduino +5V and 0V


texts: Positive and negative voltage regulation

texts:
This is my first post so please be patient.

I need to get three voltage rails, +18v, 0v, -18v and am trying to use a cheap XL6009 voltage boost module to do so.

My plan is to connect a 12v line to two modules. This will give me +18v and 0v.

I was then planning to connect it as follows:

Module 1:

+18v output to +18v load
0v output to 0v load

Module 2:

+18v output to the same 0v load as module 1
0v output to -18v load

I am not sure if this will work or if it will damage anything.

This is the type of module I am using.


texts: Measuring average current with uC and current shunt

texts:
This is my first post. I'm a software guy trying to do hardware so be gentle :)

Circuit

I'm designing a small circuit (see pic, and sorry for messy schematic) that plain and simply is a bunch of MOSFETS and gate drivers designed to switch resistive loads (heating pads in this case) from a microcontroller. The heating elements often has a very low resistance, and to keep power at the desired level, the MOSFETS are switched using PWM.

Measurement

Besides the purely functional aspect, there's an educational focus as well. I want to be able to get some feedback on the current consumption. And my naive approach was to simply throw in some current shunt sensor IC's.
When using a multimeter to measure the output voltage from the sensor, I actually get something that looks like the average current (with PWM switching) due to the "slowness" of the ammeter. But when connecting same output to i.e. an atmega328p ADC, I get some bad readings - the speed here puts a reading anywhere on the PWM square wave.

So, my question is how do I go about measuring the (average) current when switching with PWM?

It seems the design is OK, but I might have missed something in both the design and how the uC ADC should be used in this context.


texts: Non Minimum Phase Systems and Sensor Location

texts:
A stable minimum-phase system could potentially turn into a non-minimum-phase system after moving sensors to the AFT (behind) of the CG (Center of Gravity) of the vehicle 1. This is specifically applicable to conventional airplanes.
How sensor location can affect the minimum/non-minimum phase state of the system? In other words, how sensor's location can affect the presence of the RHP zeros in the system?
I understand that moving sensors does change the output of the system (C matrix) which will be reflected on location of zeros in S-Plane. But the part that I can not wrap my head around is the mapping from sensor location to location of zeros in the system.
From Control System Design by Karl Johan Åström, 2002 - Chapter 5:

Problems that are caused by time delays and RHP zeros can be
approached by moving sensors to different places. It can also be
beneficial to add sensors.


texts:
I am relatively new to the smartwatch manufacturing process and I am not hardware engineer. I have seen few videos on DIY smartwatch. Following is what I have learned so far:

We need to manufacture the PCB by uploading the Geber file.
Solder the components to PCB.
I need the Arduino Bluetooth module to transfer the data from watch to the phone.
Motion sensors (gyroscope and accelerometer) to track hand movements.

The goal is to make a simple band that can track movements of my hand and send the data to cellphone.
My questions are:

Any suggestions on the specific components (motion sensors and battery) which I should buy to achieve the goal.
Is using cellular data and sending the data to the cloud better than using the Bluetooth. What can be the caveats, if any?


texts: Can the metal tab at top of a TO-220 package be cut off?

texts:
I am using a TIP120 Darlington transistor in a through-hole (specifically TO-220) package, in a very simple application which does not generate much heat.

I remember reading that the metal tab at the top is only for connecting to an optional external heat sink.

Due to a design dimensional issue (unforeseen!), I need to reduce the height of this package in my case.

Can you cut the metal tab off without any effect on the functionality of the component?


texts:
Source

What I know (I think):
Q1 and Q2 are PNP transistors.
A1 is a differential amplifier.
When A1's output is low, current through Q1 and Q2 is increased.
The Q1 and Q2 collector voltage must be less than the A1 output voltage.

How do I calculate the collector voltage of transistors Q1 and Q2 in this constant current circuit?


texts: Is an even number of DRAM chips required?

texts: I want to design a microprocessor based board (NXP imx 8m). All the boards I've seen so far have an even number of DRAM chips. If I want 4GB of RAM, do I have to use two 2GB DRAM chips or can I use one 4GB chip?


texts: Waterproofing electronics by dipping into polyurethane or lacquer

texts:
I've been looking at and thinking about a few related topics...

https://arduino.stackexchange.com/questions/9163/using-arduino-for-industrial-process
Reliability of the Arduino platform for industrial use

...and I decided to throw out this question. I've seen professional circuit boards with chips and all that are 100% waterproofed via clear-coat finishes across the whole board. Is it a reasonable, good method to just dip a whole, final, soldered circuit board, such as a completed Arduino Nano project with all wires soldered, into polyurethane or lacquer to give it a protective finish against water, corrosion, humidity, chemicals, etc?

I'm thinking of using these products specifically:

http://www.homedepot.com/p/Minwax-1-qt-Gloss-Fast-Drying-Polyurethane-63000/100136801
http://www.homedepot.com/p/Minwax-1-qt-Satin-Fast-Drying-Polyurethane-63010/100201939
http://www.homedepot.com/p/Minwax-1-qt-Gloss-Clear-Brushing-Lacquer-15500/100534503
http://www.homedepot.com/p/Rust-Oleum-Specialty-11-oz-Gloss-Clear-Lacquer-Spray-Paint-1906830/100194482

If this is a reasonable thing to do, which is better: satin, semi-gloss, or gloss?

Dipping into an (oil-based) Minwax Gloss Polyurethane 1 qt can sounds the most reasonable to me at the moment.

The one exception to this technique is to simply ensure you don't cover up any sensors that destroys their ability to function (ex: barometric pressure sensors, humidity sensors, etc). Also, I'm sure the board won't cool as well...

Update:
Looks like the keyword I needed was "conformal coating." Here's one source mentioning polyurethane as a good choice: http://www.conformalcoating.co.uk/Conformal_Coating_Material_Types.php


texts: I've heard of someone getting RF burns by touching a high power antenna. If enough power is supplied to the antenna could it melt, or would anything else happen? If so, how much power would have to be supplied?


texts: Are there multiple bits on a data cable at the same time?

texts:
Let's say there is a copper under sea cable from New York to Lisbon with a length of 5350km.

Then a signal needs approx. t = 5350km/c ≈ 19ms to arrive.

Now let's imagine sending a file from New York to Lisbon.

I assume that you don't have to wait until one bit arrived before sending the next bit.

Because if you would have to wait you would have a speed of only 1000ms/19ms ≈ 53bit/s.

So let's instead assume a speed of 1 MBit/s (still slow).
That would mean there are 19ms*1MBit/s = 19000 bits on the wire at the same time.

I did the same calculations with a standard LAN cable of 20m. With a speed of 10 MBit/s you can wait. But to get a speed of 100 MBit/s there must be multiple bits on the wire at one time.

Is that correct?


texts: I want to interface stm32f0 with rs422 (half duplex and full duplex). What I'm not getting how to connect RE and DE signals to rs 232. From UART I'll be having RX, TX, VCC and GND pins which i need to connect to TTL to RS232 converter ( http://www.emartee.com/Images/websites/emartee.com/T1d6JsXfBrXXXJ2U79_105143_jpg_310x310.jpg ) but where i should connect the RE and DE signals?


texts:
I've been building USB powered audio DAC circuit which is using multiple LDO voltage regulators.

I discovered one of the regulators, namely TPS79333, which is responsible for supplying 3.3V to PCM2706 chip, is outputting 4.92V (more or less equal as input voltage). Is this a clear case of faulty voltage regulator or could a problem be something else? Is there a way to trace which component is causing it?

Also I'm afraid it's over for DAC chip with such high voltage on supply pins. :(

Thank you for your answers.

EDIT: To clarify I'm building PupDAC. Schematic can be found here: http://www.diyforums.org/PupDAC/schematic/pupDACschematic.pdf

Regulator in question is U2.


texts: How to prevent iPhone 6 acting as faraday cage

texts:
I have experimented with attaching my work RFID access card to the back of my iPhone 6 which is made from aluminium.  However it appears that the phone is acting as a faraday cage and preventing my card from being read.

Is there a material I can place between the back of my phone and my access card to disable the faraday cage effect?


texts: What do you call a switch/relay which switches on an appliance for a given set of time?

texts:
I need a relay/switch, which would have a push-button switch upon which the button is pressed, it would power an appliance on.

I have a water pump, and its water pressure switch is defective. I would like to make it such that I can switch it on for 10 minutes, and it automatically switches off after the 10 minutes have elapsed.

What is this type of relay/switch called? This is not to be confused with a 'timer', which would say switch on an appliance at a given time every day, like those which are sometimes used for Christmas lighting, where you can switch it on at 5 pm and automatically turn off at 11 pm.


texts: How to understand the timing report after synthesis?

texts:
After synthesis of my verilog code. I am getting the below timing report. I think it showing any mistake in my code.

Timing Summary:

Speed Grade: -2

Minimum period: 2.334ns (Maximum Frequency: 428.376MHz)
   Minimum input arrival time before clock: No path found
   Maximum output required time after clock: 1.282ns
   Maximum combinational path delay: No path found

The main thing which bother me is the comment highlighted by bold. Is it showing of any kind of error?


texts: How to count the number of the generated PWM pulse on ESP32 micropython？

texts:
pin=Pin(17,3)
pwm=PWM(pin, freq=freq, duty=duty)
dir(pwm)  #  ['__class__', 'deinit', 'duty', 'freq', 'init']

How can I count it? Does micropython provide this feature?


texts: What options are there for connecting peripherals to a micro controller?

texts:
I'm developing a prototype based around the netdunio and I am not looking at connecting external sensors to the device. I need to be able to disconnect the sensors when required but  I am looking for a more elegant solution than using jumpers.

My initial thoughts where to use RJ11 jacks and ports. I like the click-in capability of the RJ11 jacks plus is meets my need to disconnect but I only require two channels so its a bit over engineered.

What other options are out there that would meet my needs?


texts:
I am trying to simulate a testbench on ModelSim, but when I run the simulation, it never advances in time. The delta does not increase, either.

Are there any useful tips for debugging in a situation like this? I suspect that the problem may not be in my testbench, but in the maze_solver entity itself. Here are some possible problems:

maze_solver also contains a structural description for another entity within it. Is it okay to simulate like this? As long as I have added that other entity into the ModelSim project?
Could it be a problem with my sensitivity lists? I have checked them all, and all the right-hand side signals have been included on the sensitivity lists.
Could it be a problem with my testbench? I have included the testbench code below.

Since the maze_solver design is long, I have not included it, but I can include it if necessary. It is a finite state machine (uses only case and if statements).

Below is my testbench:

library IEEE;
use IEEE.std_logic_1164.all;

entity solver_testbench is
end entity solver_testbench;

architecture tb of solver_testbench is
signal clk,reset: STD_LOGIC;
signal cell_data: STD_LOGIC_VECTOR (7 downto 0);
signal data_rdy: STD_LOGIC;
signal rd, wr: STD_LOGIC;
signal row, column: integer;
component maze_solver is
    generic(maze_width : in integer);
    Port (clk, reset : in STD_LOGIC;
        start : in STD_LOGIC;
        rd_cell_data : in STD_LOGIC_VECTOR (7 downto 0);
        data_rdy: in STD_LOGIC;
        rd,wr: out STD_LOGIC;
        row, column: out integer
        );
end component maze_solver;
begin

aravindans_maze_solver: maze_solver
    generic map(maze_width=>2)
    port map(clk=>clk, reset=>reset, start=>'1',rd_cell_data=>cell_data, data_rdy=>data_rdy, rd=>rd, wr=>wr,
         row=>row, column=>column);
process
begin
clk <= '1';
wait for 10 ns;
clk <= '0';
wait for 10 ns;
end process;

process
begin
cell_data <= (others=>'0');
if rd = '1' then
    if row = 0 and column = 0 then
        cell_data <= "01000000";
        data_rdy <= '1';
        wait for 20 ns;
        data_rdy <= '0';
    elsif row = 0 and column = 1 then
        cell_data <= "00010000";
        data_rdy <= '1';
        wait for 20 ns;
        data_rdy <= '0';
    elsif row = 1 and column = 0 then
        cell_data <= "00000000";
        data_rdy <= '1';
        wait for 20 ns;
        data_rdy <= '0';
    elsif row = 1 and column = 1 then
        cell_data <= "00000000";
        data_rdy <= '1';
        wait for 20 ns;
        data_rdy <= '0';
    end if;
else
    cell_data <= (others => '0');
    data_rdy <= '0';
end if;
end process;

reset <= '0', '1' after 5 ns;
end architecture tb;


texts: Question about Thermocouple to digital convert output

texts:
I have a MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter. I have a question displaying the outputs on a LCD module. The FPGA board has a built into LCD module, so there is not much do to other than to tell it what to display for a given input. My trouble is figuring out what the input of the MAX31855 is going to be. I am reading the table, and it says the data comes in as a 14 bit SIGNED value. I understand signed notation, zero MSB is positive, 1 MSB is negative. What I don't understand is that the Digital Output is 0000 0001 1001 00 (100 in decimal) for the temperature in Celsius is 25+.

If I was trying to figure out a one to one relation, binary number [x] refers to temperature [y], how would I go about doing that?

Here is the datasheet, table 4 on page 10 is what I am referring to.

https://cdn-shop.adafruit.com/datasheets/MAX31855.pdf


texts: How to get Keil Trace to work on stm32f4 for debugging?

texts: I'm using stmf429-disc board with Keil 5.I've enabled trace check in hardware debug's trace window and have set trace clock to 168MHz which is the core clock freq. Also enabled the port 31 for rtx trace and 0 for for user trace. When I start debugging the debug's os event viewer doesn't update although "System and Thread Viewer" is updating as expected(I'm running an OS). Also ITM_sendchar(char) function doesn't send anything apparently.


texts: Specification Requirements for a TVS Diode

texts:
I want to add a transient-voltage-suppression (TVS) diode to my design, but am getting confused about the specifics around Maximum Clamping Voltage, Maximum Peak Pulse Current and Minimum Breakdown Voltage.

My intention is to use the TVS to stop spikes in voltage causing damage to components (they are 5v RGB LEDs, which are sensitive to voltage increases)

I need the TVS to keep voltage under a maximum of 5.5v and be able to handle about 15Amps of current, though this is a maximum, current use could be anything from 1Amp to 15Amps (and could change quite rapidly).

So what are the specification I need to consider when selecting a TVS Diode?


texts: My customer's schematic uses a 0 ohm resistor for connecting analog(AGND) and digital (DGND). I think it is for testing, current measurement , fuse, jumper, test point etc but is there another reason?


texts: What is the most energy effecient type of RF oscillator?

texts: Here are the options: the Gunn Diode, the Barkhausen-Kurz Tube(AKA "transmitting triode"), the so-called Lighthouse Tube, the cavity Magnetron, the reflex Klystron. I'm leaving out the Gyrotron because it is very much a cut above all the rest but can someone rank them from least to most in terms of energy efficiency.


texts:
I want to analytically calculate the power spectral density (PSD) for noise at the input of the given circuit as a function of frequency. Both resistors cause noise, as well as the opamp itself, with V_n and I_n.

I interpret V_n as noise voltage source connected at the positive terminal and I_n as current source connected at the negative terminal.

From my current understanding PSD is the total power with reference to a specific frequency f.
$$
PSD(f)=\frac{P(f)}{\triangle f}
$$

So what I do is sum all the power values together and divide by the frequency.
$$
PSD(f)=\frac{1}{\triangle f}(\frac{V_n^2}{R_1}+I_n^2(R_2||C)+\frac{4kTR_1 \triangle f}{R_1})=\frac{V_n^2}{R_1\triangle f}+\frac{I_n^2}{\triangle f}\frac{R_2}{2\pi fCR_2+1}+4kT
$$

Is my procedure and the result for calculating the PSD at the input correct?

Note: This is not homework. I am preparing for an exam.

simulate this circuit – Schematic created using CircuitLab

EDIT: The following picture shall demonstrate what I currently understand under PSD (on the basis of resistor noise):


texts: Altium Gerber Top Paste is missing components

texts:
I just finished the design of my board on Altium, and when I generate the Gerber files, everything seems correct except for the Top Paste File, looks like some components are missing on this file. Any idea of why is this happening?

I used ViewMate to check if there was any problem with the Gerber viewer from Altium but the file looks the same.

Here are some screenshots.

It's evident that a lot of components are missing, capacitors and resistors in specific. I want a stencil so that's why I need the Top Paste Layer. I hope you guys can help me out, I've been playing around without any solution.

Thank you.


texts:
What online tool can I use to tinker with circuit boards / dimmers / buzzers etc?

I'm wanting to learn more about electronics without spending too much time & money on buying parts I'll only use once.


texts: How do I distribute power to a multi-component electrical system?

texts:
I'm designing a multi-component system for a walking device and want to use a centralized unit to power the four joint motors. Each distributed unit needs a 12V DC signal to power the onboard components (arduino, solenoid, encoder, etc.).

I feel like having the four distributed units in parallel will greatly reduce the amount of current I can draw from the central power unit. Is it possible to use a single 12V DC power unit (connected to a wall socket or maybe a rechargeable battery pack) to power all four of the devices? It'd be nice to be able to use something like this with a splitter.

If this isn't the best option, what alternatives should I consider?


texts: How does kiCAD / eeschema merge multiple wire labels into the netlist?

texts:
I was hoping multiple labels on wires would allow using different physical and logical names for the same signal (e.g. "net42" to match a different schematic on "the other side" of a connector, and "PWM" for the logical signal).

KiCAD allows this (http://docs.kicad-pcb.org/4.0.7/en/eeschema.html#connections-wires-and-labels):

  Note 4:

  If two different labels are placed on the same wire, they are
  connected together and become equivalent: all the other elements
  connected to one or the other labels are then connected to all of
  them.

Unfortunately, when I try to extract the signal names for each pin of a specific component, it seems only the label that has been used first is used in the netlist.

I was hoping to get information about the additional wire name(s) from the netlist (i.e. a list ["net42", "PWM"] or a combined string like "net42, PWM"), but it seems I have to limit myself to one label in order to have that info show up in the netlist?


texts: How accurate are the crystals on ST's Nucleo boards?

texts:
I got myself a cheap ST Nucleo-L053R8 on discount, to play around with a couple ideas.

The main STM32L053R8 only has a low-frequency 32.768 kHz crystal for RTC, but it can also be provided with an 8 MHz clock from the included ST-Link USB programmer. The LF crystal is marked 32G501, and the ST-Link's is marked 8.000Q5G.

Does anyone have any idea how accurate these two crystals are at room temperature? The documentation doesn't seem to specify.


texts: AVR: disassembler with named-register support

texts:
Is there a AVR disassembler which produces human readable output, e.g., writes

OUT       SREG,R0

instead of

OUT       0x3F,R0

(I would like to get a better understanding of what the compiler is doing.)


texts: How to create EMI/EMC noise for testing product behavior in noise environment?

texts:
We have product which works on three phase AC supply. We were facing issue on I2C interface of external RTC due to noise from external environment. After some inspection, we realized that because of improper isolation of analog and digital ground, I2C device was getting reset due to bouncing of ground level. We eliminated that issue to some extent by isolating ground. Still the issue persists with I2C interface of external RTC on noisy sites.
     We obviously never faced noise issue in our lab, so I want to know how we can generate noise in three phase supply going to the device so that we can replicate the issue in the lab?


texts: Typically, there is a CPU with a flat metallic top which is connected to the heatsink with a thermal conductive grease. What metal is the top of the CPU package?


texts: Circuit for switching LED with minimal impact on digital signal

texts:
I am looking for a ciruit which allows switching an LED according to a digital (bus) signal. The actual signal should only be minimal affected (rise time etc.).
An example: Light up an LED when a SPI device is selected by ~CS. I dont want to use another digital pin of the master for this.
What circuit would be appropriate?

My thought was using a Darlington transistor as it is available in arrays in an IC (e.g. ULN2003D) and should work with low currents to switch Q1:

simulate this circuit – Schematic created using CircuitLab

Is this a good approach and how large should R2 be?
Note : The SPI ~CS Example needs an additional NOT gate to flash the LED when the Slave is selected.


texts: Any Ideas for Understand one of the 3 phases has powered

texts:
I want to ask you about a situation which i couldnt find the exact solution or better way to do the job.
The situation is i have 3 phase (380V) induction motor and one of the phases to the motor had a switch and the rest two phases and the the phase after the switch goes to conductors and then to ac induction motor, what i want is how can i make a circuit to actualy count if the switch is on/off and if the switch is on but also detect the power outage

One idea for me to use opamp for the phase after the switch to count if the switch is on/off
and one opamp before the switch if there is power in the phase but im not sure if i can do these with only one phase of 3 phase system

And another idea while i was looking to some similar questions is directly connecting the phase after the switch to the pic controller with a high resistance to verify if switch is on or not and again the same before the switch if there is power or not

Any ideas, or links or just a way for me to overcome this situation?

btw the switch is a push once switch i actually dont know the exact name but what it does is when you push, it closes the circuit and when you push it again, it opens the circuit.


texts:
How to understand term wavelength of radio wave in real life. What this column 'Wavelength range' means to us in real life?

I theoretically understand what it is (distance between two successive peaks in signal), but cannot imagine what is it in real life.


texts:
I have an LED strip with 7.2 Wattage/m and the strip is 3 meters long.  The led strip has R,G,B,+12v inputs and I have connected a 12V DC 1000mA power supply to the +12v and attached transistors to the R,G,B running to ground.  When I run this circuit alternating between dimming the transistors and changing the light combination the Arduino gets hot.  What can I do to keep this from happening?

The LED strip says that is requires a 12VDC 3A 36W power supply.


texts: I am giving a 25MHz signal input to pll for simulation in cadence. But I also want to modulate its frequencies from 1Khz to 2Mhz. But how to do the frequency modulation of a signal in cadence?


texts: Why do optocouplers require a resistor at the collector?

texts: In this circuit, if the resistor in the collector R1 is 0 Ohms, the circuit doesn't work. That is, the output will be 12V DC signal as it is from the battery. And if R1 is non-zero, then the circuit works and produces expected output. Can someone explain me why that resistance (R1) is required in this circuit?


texts: Driving mosfets when supply is greater than Vgs Limit

texts:
I have an application where I need to drive a 24V load with PWM, and high side switching via a P Channel Mosfet.

Most mosfets appear to have a Vgs limit of +/-20V.

This feels like a well established problem, and I am trying not to re-invent the wheel.

I can see the direct solution of a pullup on the gate to 24V and an NPN BJT + Zenner to pull it down without violating the Vgs limit, but this doesn't seem like a particularly quick switching method (slow to switch off).

Is there a special gate driver chip that solves this standard seeming problem.


texts: Can you use rectifiers from different transformer sources in parallel?

texts:
Consider following circuit:

simulate this circuit – Schematic created using CircuitLab

It uses two transformers, rectifies their output separately (so that they can't interfere), filters the |sin(x)| using capacitor and then uses combined power of both transformers.

I can't see any problem with this design, however so far I learned that using power sources in parallel does never work well.

So is this design also flawed?


texts: What does sequences like 1-3, 1-10, 1-3-10 etc in a spectrum analyzer mean?

texts:
I have read in a paper explaining spectrum analyzer basic 'When selecting the RBW(resolution BW), there is usually a 1-10 or a 1-3-10 sequence of RBWs available. More RBWs are better because this allows choosing just enough resolution to make the measurement at the fastest possible sweeptime.' Its was also written higher the RBW faster would be the sweep time required.
What does these sequences like 1-3, 1-10, 1-3-10 etc in a spectrum analyzer mean?


texts: PV panel -a current source or voltage source?

texts: I'm reading about PV behaviour and am confused on whether a PV panel/cell would be considered to be a voltage source or current source or both or neither (from the characteristic IV curve). The IV curve looks like a combination of both constant current and constant voltage. It seems that from (a) panel is unloaded to (b) panel is loaded to max power--the operating point travels from Voc to MPP(If this is the case; I'm confused as to the reason behind why a PV cell is modelled as a current source). Do we use only this region under load conditions? Under what conditions does the operating point traverse from  MPP to Isc point?  Why is a solar cell modelled as a current source?


texts: Why does my bandpass filter act as highpass?

texts:
I have designed a bandpass filter. Here is the circuit and spectral characteristic:

As you can see from the response curve, it has cutoff with the peak ranging from 260 kHz to 290 kHz.

Here is the actual circuit :

However, the filter works more like a High pass, passing frequencies all above 250 kHz, without any distortion or attenuation.

Here is one of the outputs :

(I observe outputs at all frequencies above 250 kHz. This is just one example)

Where am I going wrong, and what corrections do I need to make?

Update :

I decided to simulate my circuit , and it was clear why my circuit acted as Highpass. (The last freq is graph in 1 MHz). Dunno why the filter design tool showed that (incorrect) graph then.


texts: AC Adapters: Do watts have to match? / Is 19v close enough to 20?

texts:
Two questions on points not covered in either of these two threads about AC adapters:

Choosing power supply, how to get the voltage and current ratings?

Reading and understanding electrical specs on laptop AC adapters

1) Watts aren't mentioned. Is it okay to replace a 65w AC adapter for a laptop computer with 90 or 120w?

2) Voltage: It says an adapter must not have higher or lower voltage than a device's specification but it doesn't say how much higher or lower, e.g. whether a difference of 1 volt out of 20 is a rounding error, or physically meaningful. Specifically, is it okay to replace a 20v adapter with a 19v one, for a laptop computer?


texts:
I have got an iron nut with a diameter of about 5 cm. I would like to solder a pin to it so I can connect a wire to it. (I want to make a capacitive sensor.)

I tried it already, but it won't attach to the nut at all.

How can I do that?


texts: How to design an square wave Oscillator Circuit with 1-20 MHz range?

texts:
I need a circuit that will generate square waves in a range of 1 to 20MHz. The circuit also should be adjustable in a scale of 0.05MHz for each step. There is no need for adjustments during the circuit operation.

It's possible to use some kind of LC circuit that i can simply replace the inductance/capacitance values?

Thank you.


texts: Use both mini-USB and micro-USB power supplies in parallel

texts:
I would like to add both mini-USB and micro-USB connectors onto my PCB for Li-Ion battery charging.
Is the attached schematic fine (safe) ?
I have never tried such type of connection yet and it would be nice to get a advice from experienced engineers before producing my PCB. Googling the problem didn't give me any useful results.


texts: How to implement diagnostic switching of power transistors in the three phase voltage source inverter?

texts:
I have been developing a control software for the three phase voltage source inverter.

For diagnostic purposes I would like to include a special operating mode of the control software in which I can test individual transistors \$(S_1-S_6)\$ in the inverter via switching them without current loading.
My idea is to write a special service application running on a laptop and via its graphical user interface select one of the six transistors. Based on that selection the control software at first transits into the "diagnostic" operating mode and then will start generate firing pulses for the chosen transistor.
My first idea how to implement this diagnostic feature at the control software level was to use the standard pwm peripheral of my MCU and configure it for the center aligned mode. Then in the diagnostic mode set a output mask for chosen transistor and set some appropriate fix value of the duty cycle.
Do you think that the simple solution I have described above is usable? Can you tell me how to determine the fix value of the duty cycle?


texts:
I'm looking to build a component (simulink) that cuts off short pulses in a digital signal (that has a varying pulse length). Does anyone have an idea?

I thought about using an integrator and comparing the output value to a calculated value that would be the integral of the shortest pulse I want to keep, but it didn't really work out so far (resetting the integral to 0 at every rising edge of the digital signal).


texts: Is there an error in the datasheet for the AOZ1284?

texts:
I am working with AOZ1284A a buck converter.
Datasheet:http://aosmd.com/res/data_sheets/AOZ1284PI.pdf
According to the datasheet:

I think they mistaken 5000 for 55000. But this works only with the 2 first frequency. for the swF of 1M I get 50K.
My Question :

Am I right?
Is it normal to take 1M as an approximation of 1065K?

(with 46.6K and when we replace 5000 with 55000 we get Rf=1065K)


texts:
My goal is to design a circuit using MOSFETs that would switch 12V power to one of the two high-current loads, using high-side switching. Control is done by a 3.3V MCU. The reason for using MOSFETS is to keep the size down.
This is my current design. The problem is that there's a short period when both of the MOSFETs are on.

One obvious solution would be to separate the control of the circuits so that both could be turned off before switching between the loads. The downside being that the responsibility for keeping the loads from being turned on at the same time shifts to software.
I've looked into using gate drivers, but unless I'm missing something, there doesn't seem to be a driver for a pair of P-MOSFETS which is what I think I need to be using for high-side switching.


texts:
I have a situation where I need to measure a capacitor connected to a live circuit like the image shows. I'm considering a LCR meter because we also have to measure both capacitance and resistance of the entire circuit.

The circuit will be powered by red and black terminals and the measurement is done by red and blue terminals. We need the relay to be opened and that's why we need to apply mains (AC) voltage to it's coil.

Is there a way to measure it with a LCR Meter? Any grounding trick maybe?


texts: Prevent Reception from an Extended Distance (Beyond Design)

texts:
I have a magnetic field that is being induced onto a power line by a transmitter, which is following the length of the power line to the receiver.  The receiver communicates via a loosely coupled coil with the transmitter.

This artificially perceives the transmitter a significant distance away from the receiver.  I suspect the AC-DC power supply line may be picking up some of this bringing it within enough distance of the receiver to be perceived.

The problem I am finding is that the copper lines running from the power supply to the receiver cannot be effectively shielded against this phenomena.  I have tried graphite sheets ideal for the resonant frequency of the system, however that approach is flawed as the signal is being brought within proximity of the receiver.

What would be a solution to attenuate or reflect the flux lines away from the power cable leading into the receiver?

Edit:

To explain the "phenomena" more technically, what is happening is the RF-field is inducing eddy currents in the non-ferrous metal, which induces a magnetic field opposite to the original field (aka Lenz effect). Of course only part of the field is reflected, so in theory I should be able to use a material with high magnetic permeability to attenuate the signal.  I wish there was some sort of flexible graphite sleeve I could use which had a sufficient attenuation at 13.56 MHz.


texts: I'm planning to put lots of phone chargers on one circuit, how to calculate this

texts:
This would be primarily for samsung S7 devices.  Would like to be able to charge, say, 256 of them.

They will work in groups of 16, trying to design the power flow of this.  Was imagining that each group of 16 would plug into a USB power strip of some kind, and then each group of 16 would link up to another power strip.

So, 16 groups of 16.

But I think that this will not work on a single 120V/15A power source.  I would like to understand the math involved with how to scale this.

It will probably be more like 100 devices at a time, but trying to understand how to calculate this and know what the limits are.


texts: Using L9110 (or HG7881) with external power supply

texts:
I want to drive a DC motor with a L9110 H bridge IC using an Arduino UNO with an external 12V power supply like this

The breadboard for the L9110 he is using is the following :

If VCC is 12V and IB and IA of the L9110 are conected to 12V and the connected to the 5V pins of the Arduino ... why the Arduino is not getting fried? I Guess the resistor has something to do with it but what is the reason for that? is there a better design?


texts: 61000-4-6 CDN calibration - how to factor in the 6 dB attenuator?

texts:
I am seeking some clarification around CDN calibration for 61000-4-6 (RF conducted immunity test).

By following the standard and some application notes, I am pretty sure I have it sorted. I just have one question.

If you look at figure 8c in 61000-4-6 it does not show the 6 dB attenuator in the setup for level setting at the EUT port of coupling/decoupling devices.

Whereas in the application notes I have read, it shows the 6 dB attenuator in circuit.

http://www.teseq.com/products/downloads/datasheet/NSG_4070.pdf

https://www.emcstandards.co.uk/files/61000-4-6_immunity_to_conducted_rfi_1.pdf

To quote the application note.

  It is important to be aware that the test levels are specified as the
  voltage into an open circuit, not the voltage that is actually applied
  to the EUT, nor even that which is observed on the measuring
  instrument during calibration. Because both source and load impedances
  are known during calibration the actual indicated voltage for an
  applied emf level can be calculated. For the CDN calibration jig, the
  source impedance is 150Ω, the load impedance is also 150Ω and the
  measuring instrument impedance is 50Ω. The indicated voltage must be
  multiplied by 3 to allow for the 50 to 150Ω conversion and again by 2
  to reach the open-circuit voltage, hence the indicated value is 1/6th
  the desired stress level.

Nowhere does it talk about the 6 dB attenuator’s effect on calibration.

My question: I kind of understand that the purpose of the 6 dB attenuator is to help match the impedance between the two circuits (correction, The 6dB pad is to improve the 50ohm output impedance of the 'generator assembly' at the test cell), but I don’t understand how it doesn’t influence the calibration level.


texts:
I was wondering if anyone has any ideas of a way I could Dim a 110v Halogen light with the use of 5V PWM, or with 0-24v control.

My controller, has the basic (designed) 0-24v control. It also has the ability to be used for 0-5v PWM by using the connection to the gate.

I have seen Light Dimmers for 110v AC lamps, and using an Arduino, however most of them want Zero Cross, which my controller (TC420) cant do. So I need a way to dim 110v AC, with just PWM, or 0-12v.

I seen talks of using SSRs, to do this, but again the Zero Cross comes up, and I am not sure I can zero cross the controller.


texts:
Why is that in the frequency domain, I always see mirror images? What causes these mirror frequencies to appear? How do they pop in? Where do they come from?

Secondly, what is this concept of negative frequency? In normal life, most of the time I only hear people mention the positive frequency. What is the role of the negative frequency and why is it always a mirror image of the positive frequency.

The lowest figure shows the frequency domain of a cosine function (two impulses appearing, also a mirror image)


texts:
I got an article on this link. In this article the author chooses a PWM frequency of 31,372 Hz to get a smooth signal.
How do these frequency values get a smooth signal?
I've read other articles on the website but I can't find the answer.


texts:
I'm looking for an optocoupler but looks like I don't undersant their parameters well. What is "Optocoupler min collector-emitter voltage"?

For example, I found optocouplers like this but in the datasheet it is stated that "Collector-emitter voltage: 80 V (min)"

Does it mean that transistor in the coupler won't open in case voltage on it will be lower than 80V? What is the meaning of this parameter? I need the optocoupler to control 5-20V load with up to 5 mA current.


texts: Powering module directly from LiPo Charger with LiPo connected

texts:
I have a GSM module (Particle Electron) which has pins for powering it from a LiPo battery. The pins accept voltages from 3.6V to 4.4V. The module can also be powered from 5V supply through another pin (Vin).

I have a solar charger based on the MCP73871 LiPo battery charger IC from Microchip. This charger has a BAT+ output for charging LiPo batteries, and we have added a regulator giving a regulated 5V at LOAD+. However, this has current limitation of 1A.

Now, normally we would connect the GSM module's Vin pin to the 5V output. However, since the module has current surge requirements of 1.8A, we are thinking of connecting the Li+ pin of the GSM module to the BAT output of the solar charger.

I want to know what could go wrong in this setup? Could this setup somehow damage the battery, or the solar charger, or the GSM module?

simulate this circuit – Schematic created using CircuitLab

To put it simply:

  Can we connect in something in parallel to a LiPo battery while it is being charged by a LiPo charger? Can the charger or the LiPo get damaged in such a case?

Some essential info:

GSM module has surge current requirements of upto 1.8A


texts: Does LTSPICE automatically include avalanche parameters in its power dissipation measurements?

texts:
Does LTSPICE power calculation window like this

take into consideration MOSFET avalanche parameters and include them into the overall average power value?

That particular image is for a resistor not MOSFET.


texts:
When I compile my project in QUARTUS, it provides me with information about "internal fmax"
Info: Clock 'clk' has Internal fmax of 39.37 MHz between source register <...> (period= 25.4 ns)

What does it mean exactly? Won't my program work on a frequency higher than fmax? I've seen a working project that runned on 50 MHz and had internal fmax of only 12.99 MHz. Should I care about it? Can I optimize it?


texts: MOSFET terminology seems to vary in every article I read

texts:
For someone trying to learn about FETs, it seems there is no consistency in terminology (unless I am reading things wrong.)
I am trying to understand the FET as a switch (for power applications.) It has become clear that you want to operate a switch in the ohmic region. To get to the ohmic region you would need to go from cut off -> saturation -> ohmic region.
TI refers to it like this in an app note:

From this I implied that the 'linear' region is in fact rather confusingly the saturation region of the FET as shown all across the web for a FET curve:

However, when I went to wikipedia I came across the following image:

This is saying the exact opposite of what I understood which is saying that the ohmic region is the linear region.
Infineon has an app note around FET switching, titled Linear Mode Operation
They refer to the linear mode as the saturation region as shown from this:

So what is it then?
Also just to be clear: Is the reason we want to minimise time in the saturation region with an FET because here we have a VDS and an ID current flowing through the FET, whilst as soon as the FEY reaches linear region, it's VDS would fall close to 0 and hence minimise losses?
When we say the FET is saturated, it means for a given Vgs, Vds makes no difference to drain current (because channel can't let more electrons to flow?) Shouldn't the ohmic region be called saturated? Since increasing VGS makes no difference to drain current as the ID is now limited by the circuit and not the FET?
Edit:
Answers in electronic stack exchange say it is the saturation region:
Link1
link2


texts: Odd Parity Output as Input to Second Circuit

texts:
Lets say there is a circuit that takes 3 bit input and produces an odd parity bit output.So I have arrived at the following truth table.

      A    B   C    Output(D)
1     0    0   0       1
2     0    0   1       0
3     0    1   0       0
4     0    1   1       1
5     1    0   0       0
6     1    0   1       1
7     1    1   0       1
8     1    1   1       0

As an expression this comes to

A'B'C' + A'BC+ AB'C+ ABC'

So far so good. My problem begins now.

Now I am asked to design a second circuit which takes the three inputs and one output of the first circuit and output 0, if the odd parity is satisfied.

I have to put up a truth table and use Karnaugh map to design the boolean expressions for each of the output bits. But as per my understanding taking the 3 input ad one output bit from the previous circuit as inputs to the new circuit will always yield a 0.

But had that been the case, the question of using karnaugh map would not have been asked in the first place.

What am I missing or misunderstanding in the question ?

Here's the original question, just in case I have understood it wrong.


texts:
I want to implement an RS485 absolute encoder, values 0-2048, on a canvas rapid door. The controller MCU that reads the encoder, which I will programm, may not be powered all the time, but it should be aware of door position on power on. Limit switches will not be installed. The door's movement will never translate to more than 360 degrees revolution on the encoder. It is expected that maximum movement will have a span of around 1600 values.

The installer will set the lowest and highest positions during a setup procedure: Move the door to its lowest position, store the encoder value, move the door to its highest position, store the encoder value, setup completed.

The lowest position can translate to any value on the encoder due to the fact that the canvas is fitted on the roll bar without knowledge of encoder position. So it can have a lowest position at encoder value of 100 or 1000 or 2000. This means that in normal movement, the value will wrap around 2048. Moreover the installer can fit the motor on the left or right side of the roll bar, so the encoder value might increment while the door goes up, or vice versa. To complicate matters even more, the door might move further from the lowest position, due to break heating, gear oil temperature change etc, so if its lowest value was 50, it could wrap over zero and reach a bottom value of 1950.

Considering the above description and scenarios where lowest (Lxxx) and highest (Hxxx) position have corresponding value pairs of: L200-H1400, L800-H300, L10-H1500 and the reverse movement of those L1400-H200, L300-H800, L1500-H10.

What algorithm - conditions would you use to stop the motor at the lowest and highest positions?


texts: can i connect two similar antennas to two ends of a cable to to re-transmit the signal received from one end?

texts:
Scenario:

I've set up two wifi hot spots outside of my house at distance lesser than 20 meters as i don't get any ISP signal inside my house. But the problem is now i get very weak signal in my house because of nature of walls.
I'm afraid of buying any repeaters as they reduce the speed by two.

My Idea:

So i've thought of building two simple omni-directional WiFi antennas myself (such as biquad or helical) and connect them to each other by a cable, and put one at outdoor and other at indoor. But i'm not sure if this would work out, so i need your suggestions please..

Additional Infromation:
I got this idea  from following instructable, but it is not for WiFi, and not simple as i think
http://www.instructables.com/id/DIY-2G3G4G-Wireless-Cell-Phone-Signal-Booster/


texts: How should PCB traces be treated in different situations?(as capacitance, resistance or inductance)

texts:
I know that for signal integrity, the  PCB traces are always considered to be part of the electrical circuit.
How should traces be considered in different situations, like high current, RF, high edge rates etc.?


texts: 12V Battery Backup Supply for GPRS Tracker

texts:
I have little knowledge on electronics apart from following a few guides. I have made a few 7 segment displays, nothing complicated.

Recently my girlfriends car was stolen and she has an insurance style GPS tracker, but only gave the road that the tracker was down. We spent hours looking for clues and eventualy we found the car and it had been chopped up into bits with the tracker striped out.

Now these GPRS trackers are good but useless if the battery is pulled out.

So my question is:

How do I create a  circuit so that when the car battery is dead/removed, a small 12V battery hidden away kicks in and powers up the tracker.

Now I have done my research and all I can come across is complicated circuits that involves the 2nd battery being charged up aswell.

I don't need this, all I need is a few good hours out of the second battery so charging the second battery is not needed.

This is the tracker:   http://www.amazon.co.uk/Tracker-Vehicle-Theft-Protection-System/dp/B003XDN58K/ref=sr_1_2?ie=UTF8&qid=1389875239&sr=8-2&keywords=gps+tracker


texts: TCA9548A I2C Multiplexer - 10k resistors on the address lines

texts:
I'm looking over the schematics and PCB layout of the Adafruit TCA9548A I2C Multiplexer breakout board. I've attached the schematic below.

I cannot figure out why there are 10k resistors on the A2,A1,A0 addressing lines. Do these serve just as current-limiting resistors?


texts: How do I conduct an experiment to find the discharge curve of a lithium ion battery?

texts:
I want to conduct this experiment with a multimeter only. What sort of load do I put?
I used a Sony Li-ion Np-BPL battery model and after full charge, I put the battery across a load of 1k Ohm; however, the battery discharged suddenly in 5-6min. Its voltage was 4V at the charged state and it dropped to 0.10V. Why did this happen?
What should I correct?


texts: Understanding the failure mechanism of capacitor

texts:
Most ceiling fans and table fans designed for household use, eventually slows down before completely failing to work.

By close observations I found these fans are using capacitor-split-phase motor and failure of the motor is electrical  and not mechanical such as ill bearing etc. When the capacitor feeding one of the two coils of the motor get weak (dropping capacitance), the motor not able to develop and maintain the torque needed to sustain rotor speed.

The type of capacitor used in this fans are generally Metallized Polyester Film. Why this capacitor fails?

Capacitance is depends on dielectric constant of the insulation of polyester, thickness of that insulation film and total area of the metallized surfaces.

I belive the drops of capacitance is due to  somehow the metallized surface effective area drops due to discontinuity develops within the rolled film. Polyester is stable thus it's dielectric constant or its dimension will not change over time.

If the cracks that cause discontinuity of metallic surface on the film is what cause the drop of capacitance, why it happens?


texts: TPS61025DRCR regulator input voltage drops to below 3V when powered - trouble shooting techniques?

texts:
I'm currently using Texas Instruments TPS61025DRCR voltage regulator in a project (digikey link. When attempted to be powered with a 3V input, the regulator input voltage drops down to ~1.4V. When I unplug the 3V power source and measure its voltage, I again receive 3V. Thus, the issue has something to do with interfacing with the regulator.

My regulator circuit is illustrated below.

Note that this circuit was influenced by the TPS61025DRCR manual here.

Here is what I have done to troubleshoot the issue so far:

Because VIN_RAW (per my diagram) is dropping to 1.4V, I first checked to make sure that there was no short circuit from VIN_RAW to GND. I was able to verify that VIN_RAW is not short circuited anywhere.
I next verified that none of the solder on the pins had bridged.
I then verified that the VCC (voltage regulator output) was not short circuited (or had low resistance to ground).

I'm looking for a little feedback on other potential errors. Things I can think of:

I used too much hot air when soldering and just broke the chip.
There is something wrong with how I designed my circuit.

Any ideas?


texts: Electromagnetic compatibility and external sensors

texts:
I have two main questions regarding the electromagnetic compatibility (EMC).

If I develop an electronical device and market it in Europe, it needs to be EMC-compliant, right?
How come I can buy European devices which are not EMC-compliant? Do the devices truly need to pass the EMC test to be certified?

Let's say I have to develop a system with a microcontroller which retrieves data from a sensor. The sensor is outside of the PCB, and I have to use a wired communication between them. For instance, temperature sensors are usually accessed through I2C. However, transmitting I2C through a cable will not pass the EMC (and maybe not even work if the cable is too long). I can use an I2C buffer to make it work but still it will not pass the EMC.
Is it necessary to convert the data to another protocol (RS485, RS422, RS232, CAN...)? Does it mean that each external sensor would need its own microcontroller? I find it a bit onerous, are there other solutions?


texts: How to change PORTx register in other place of program?(Codevision & AVR-GCC)

texts:
I have a question related to AVR microcontrollers using AVR-GCC and CodeVision:
Normally we set the port related registers inside the main function using DDRx/PORTx registers, for example like this:

DDRB = 0x00;
PORTB = 0x00;

How can I change the content of these registers in other places of the program?

And another question, is it wise to set DDRx and PORTx registers using the following way:

DDRB.0=0;
PORTB.0=1;


texts: Is the input voltage on power adapters RMS voltage or peak AC voltage?

texts: For example, would a laptop power adaptor with a voltage input of 100-240V ~ be safe to use in a country with 230V RMS wall voltage? Thanks in advance!


texts: Why aren't there many (voltage controlled) variable capacitors above ~1000pF?

texts: I was looking into finding a variable capacitor to implement in a closed-loop self-tuning RF circuit and I noticed there aren't many options above 1000pF and I got curious. Do they not exist because they are difficult to manufacture above a certain capacitance? Or is it because there aren't any use-cases for variable capacitors above 1000pF? Or is there another component that fills this criteria?


texts: Help in the design of a super low power device

texts:
I'm building a wireless device that have to last with batteries as long as posible. The device has an rf module with a microncontroller that manages the control, that part is bought and works fine. When that module recieves an especific rf signal, has to activate a motor, using a motor driver (LB1930MC).

I'm not a expert in that field, but i achieved this with literaly 5 components (module, 2 capacitors, the motor driver and the connection header for the motor and the JTAG for the module), and that makes me think i'm doing something wrong. If i want to sell it i need a device that is ready for produccion, and i need help in that field. Is something i'm missing?, is something needed in the power part of the circuit or for safety norms that i have to have in mind for production?

And by this I do not mean certification as the FCC for the radio module or anything like that. I mean what is necessary for my product to be a final product, safe and ready to go.

Second question:

In the power part of the circuit, the microcontroller can work from 3.8 to 1.8 volts, so i'm using 2 AA batteries. If i want to replace it with a lithium battery, i can't  because when is fully charged it's voltage is 4.2 volts. The simplest-cheapest conclusion was to put a diode in series with the lithium battery, so now the maximun voltage of the battery drops 0.7 volts (3,5 v), and the minimun voltage of the battery (2.7-3 V for lithium battery) least 0.7 volts is still above the 1.8 minimun voltage of the microcontroller. My question is: a low dropout linear regulator or a DC-DC converter is a better choice for achiving more battery life? (both alternatives are more expensive, and the product needs to be very cheap)

One last question is:

The device needs to run 24/7 countinously forever, so if i use lithium batteries i have to charge it at the same time the device is running.

I read that i can't charge the battery and have a load at the same time because in the constant current part of the charge the current is low and if the device uses more power, the battery keeps discharging and never charges. Achiving this needs an extra circuit that disconnects the battery from the load and powers the load from another source.

The power consumption of my device will be less that 1 mA normaly, with some peaks of current when the rf module is transmiting (the motor is powered from other source).

If i have such low current, that means i can charge the battery and still power the device with no extra components? or is that a risk?

EDIT:

As i said the average current of the device is less than 1 mA, with peaks of 50-60 mA for the Rf module.
I have not the option of pluging it into the wall.
The number of times the device will wake up and activate the motor are from 0 to 10-15 times in a day, with an average of 6-7 times/day.
I need at least 4 months of battery life (time between recharges).
I was thinking in using a 500-1000 mA lithium battery.
The motor used is a little dc motor. It's not dangerous, but the old system that is already used for the motor should continue to function without any problem, so my system must interfere with it as little as possible (in my example only interferes getting in parallel with the motor).


texts: Is it okay to join two ethernet cables by soldering?

texts:
I want to connect two Ethernet (UTP) cables. Both of them have connectors only on one side. Is it okay to solder the wires together?

Could it affect maximum speed? (For example I wouldn't be able to use gigabit ethernet.)
Could transferred data be significantly corrupted?
What about electromagnetic interference?

The cable would be approxametly 4 m long.


texts: Multiplexer diagram of \$C = A \cdot B\$

texts:
I'm having some trouble figuring out how to illustrate, as a diagram, a multiplexer. I realise that a multiplexer takes in a number of input signals and depending on the control sign, outputs the selected signal as a single output. In my course a normal Multiplexer looks like the following:

Before I did anything, I set $$se1 \equiv S$$ and $$out \equiv X$$. Therefore the Boolean expression, for the following will be $$(\neg SI_0)+(SI_1)=X$$. For me that's not the hard part but what if I have the following Boolean expressions and I want to convert it into a Multiplexer diagram:

$$C = A + B$$
$$C = A \cdot B$$

How would I go about doing this? My initial thought was that since the Boolean expression is in the form $$C=(\neg S \cdot A)+(S \cdot B)$$ and the only explanation I could come up with, is that $$S \equiv A$$ therefore the control sign would be A and not S, therefore the it has the same diagram as the one above but with $$I_0 \equiv A$$ $$I_1 \equiv B$$ $$S \equiv A$$ . But then how could I do that with $$C = A  \cdot B$$


texts: Considering Delta Sigma ADC. How to set an arbitrary sampling frequency with ADS1675

texts:
I have been reading about what delta sigma ADC (DSADC) is and if they can help me in my project and I think they will.

The oversampling reduces the requirements on the analog anti-aliasing filter and DSADCs have very good resolution.

I have been reading on a DSADC from Texas Instruments, ADS1675, but don't understand how I can control the sampling rate with better resolution than the already built-in options. I assume that if the crystal oscillator has variable frequency I can somehow be able to set an arbitrary sampling frequency?

If so, what kind of crystal oscillator has a range between 1kHz to 32MHz? I want to be able to set a sampling frequency of about 1kHz to 1MHz.

So how can I achieve this? Is it possible or are one restricted to the built-in sampling rates?

Side note:
I am using a microcontroller with 72MHz clock.

Here is a direct link to the data sheet:
ADS1675 Data Sheet


texts:
I have gyro sensor l3g4200d and output from sensor is angular velocity (deg/sec), i want convert output from sensor to angle value (deg). And to convert, i must integrate angular velocity (deg/sec) like equation below:

$$\Theta = \Theta_0 + \int \omega(t) dt$$

Where:

\$\Theta\$ = angle (deg)

\$\Theta_0\$ = start angle (deg)

\$\omega(t)\$ = angular velocity (deg/sec)

\$dt\$ = time (sec)

How to write that equation into cvavr source code?


texts: What's the purpose of these two diodes in this circuit?

texts: What's to point of using these two diodes? Can't you just replace them with a resistor?


texts: Where to install potentiometer to control volume in this circuit?

texts:
I have a little mic + pre-amp board and a little class D amp board. mic output -> 20nF cap -> audio + input on the amp and audio - input is tied to ground.

Where do I introduce a potentiometer to control the output volume?

If I put the microphone output on a voltage divider to ground, if it ever goes 100% to ground would that short out the pre-amp?

Both the mic pre-amp and the class D amp have little tiny gain trimpots, but I would like something more user accessible.

[in the diagram below I used op-amp symbols for both the pre-amp and the class D amp, and class D amp has differential output.]

simulate this circuit – Schematic created using CircuitLab


texts:
I have an automotive alternator, and would like to rewind it for higher voltage for wind power application. Since I am going to use it for Battery Charging, should rewinding it for single phase instead of three phase has any advantage ?

I think, voltage will be on higher side in single phase winding and current will be less, what are other advantage or disadvantage I should look out for ?


texts: Honeywell Pressure Sensor TSCDANN150PGUCV, Amplifier circuit?

texts:
I have been trying to find amplifier circuits for this sensor. The datasheet has one on page 29 (pic attached). However as seen in the pic, the values for the resistors are not specified and we can't find them in the datasheet. Does anyone know what the values are? We've tried some resistor values but we don't get reasonable values when we test the sensor.

Any help, or link with an example project where this sensor is used, is appreciated. I haven't found anything from my google searches


texts:
I'm driving an opto-isolated MOSFET gate driver with a 2n2222 transistor from a 3.3V microcontroller (TI Tiva C, 2-8mA max per pin). The IX3108G that I selected needs 10-16mA to be driven ON.

This is the circuit I created to do this, but the optoisolator just stays ON and never gets turned off: https://imgur.com/H4l0Q7R

Am I doing something wrong in the circuit, or is it more likely that I have a wiring mistake or bad chip?


texts: Is it possible to drive a 6 or 5 lead stepper motor with 3 phase inverter/bldc driver

texts: I wanted a good way to test my inverter circuit and all I have is a 6 lead stepper motor and a 5 lead stepper motor. Would this work for testing? I have no idea how I would wire the motor. I own a  Adafruit 858 Unipolar stepper motor (5 lead ) and a Decitek 33275-P26 stepper motor (6 lead). I was not able to find documentation on the Decitek stepper motor. I am extremely unfamiliar working with stepper motors. I understand that inverters produce 3 phases of ac 120 degrees out of phase with one another. To my knowledge most bldc motors operate with 3 coils than can accept the 3 phase inverter output. However I am not sure if there is a way to modify the stepper motor inputs/ connect in a certain way such that I could produce rotation with either of these stepper motors. When I pull up documentation for the unipolar stepper motor I find that it is essentially 2 coils connected by a center tap. Is this possible without external circuitry.


texts: Some LTspice questions. Decoupling capacitor doesn't effectively block DC. Pull up resistor voltage doesn't drop to logic low level

texts:
I'm trying to design an interfacing board that is used between a micro-controller and a phone simulator (a picture of the schematics is attached). The 44VDC is used for the phone simulator to detect phone off-hook state; this state is triggered as the GPIO pin sends a signal and turn on the M1 NMOS.

And the AC signal V3 is used to model the ringing AC current generated from the phone simulator and send to micro-controller side circuit. This AC signal is converted to DC and triggers optocoupler which should pull the signal at gpio pin from High to Low. However, it doesn't work as expected.

I'm completely puzzled by the voltage levels measured at those specific nodes near the Rectifier circuit. Also, I don't understand why the C2 capacitor doesn't completely block the 44VDC. I needed to block this DC because I don't want the capacitor C1 to be pre-charged.

Also, I have to pick a extremely High resistance for the pull-up resistor R1 to drop the V_drain to Logic low level. If I use 10k resistor the V_drain will stay at Logic level high when the BJT inside the optocupler is triggered.
Need some help. Thank you so much, everyone.


texts: Has anyone seen an FT2232H port not go into the mode set into the EEPROM? I've got a device that is programmed to be in asynchronous FIFO mode on port A, but functions as though it's still in UART mode. Curious if any else has ever seen something like that, and if there's a solution for it.


texts: I am working on a project that will boost my Lipo voltage to 5V.  I am looking at trying to use a boost converter like the TPS61235P from TI.  Is there a good way to prototype this IC package (9-VFQFN) without having to create a custom breakout board just for this IC?


texts:
I am using MSP430F5340 MCU, IDE is IAR workbench，today after adding some lines of code, I found my data that previously stored in flash was crashed. So I supposed the code memory size in flash has beyond the data flash boundary.
This MCU has total 64K flash (0xFFFF bytes), my data start address is 0xF400，and ends at 0xF9FF，in total 3 blocks of 0.5K bytes. So from 0x0000-0xF400 (61K) is for code area.

From the last lines of map file, I found something below:
41196 bytes of CODE  memory
3 022 bytes of DATA  memory (+ 83 absolute )
5 421 bytes of CONST memory

41196+3 022+5 421 <61K bytes, so how could my own data in flash was crashed?
Previously, when my data was not influenced, the map file shows:
39 478 bytes of CODE  memory
3 022 bytes of DATA memory (+ 83 absolute )
4 755 bytes of CONST memory

I wonder the code memory starting address is not 0x00，and after adding some lines, the code area just cover the data area.
Hope someone could help to explain me this matter.
I think this question involves both on firmware and hardware section, so I posted it both places.
The two maps files and MSP430F5340 datasheet were attached.
Map File1 (Data is right): https://drive.google.com/file/d/13g3YaZKI10u1q55rDdmwMBhIGRPOl71d/view?usp=sharing
Map File2 (Data is wrong):  https://drive.google.com/file/d/1l5opnbOKgD1kPARb_j0NY6KI2WhXvE9J/view?usp=sharing
Msp430F5340:  https://drive.google.com/file/d/1De8R4SqtLIoAC6_SqyonO0Nbdk6oP29L/view?usp=sharing


texts:
I am looking for some input into getting a good integrated development environment set up for AVR programming under Linux (Assembly and C).

My studies gave me some limited practical experience with AVRs but I fear I am getting a bit rusty so want to get busy with some projects but also want to persist in performing all development under Linux.

I use Ladyada's USBtinyISP and have been programming my chips using AVRdude but have yet to find an IDE that works as I like under Linux so have been compiling and building via my Windows lappie and AVRstudio. (This is why I love Arduino, good IDE & works straight away!)

So, does anyone have any first hand experience using an IDE with Linux that they have successfully developed their AVR projects with start to finish?


texts:
I'm very new to the world of EE and I'm attempting to build my first buck/boost converter using Linear Technology's LT8390A.

For the most part I have been able to follow the datasheets instructions; however, the one thing I'm unsure about is how to calculate the necessary power ratings for each of the resistors.

Below is a copy of the image schematic in the datasheet that I am replicating. The resistors circled in red are the ones that I am unsure of the power rating on. Any help in both calculating the maximum power ratings for each resistor and showing out the math would be greatly appreciated.

Datasheet: LT8390A


texts: Getting 3.3 (V) from a 5(V) rail - Emitter Follower, or something else?

texts:
I am using a Bluetooth module (RN-41 SM) that is spec'd to run at 3.3(V).

I can operate this module at 5(V) however, due to another part of the circuit, I need to run the micro controller at 5(V)

The issue I have is that the only rail I have available is a 5(V) rail. My idea was to use a 3.3(V) zener diode and buffer it through an emitter follower, however when I tried this, it failed on me. I have to supply at max 100 mA to the circuit.

I am using a garden variety transistor (2N3904).

I think my issue may have been related to biasing the transistor properly. Could anyone guide me on how to bias a circuit like this or suggest any other method I could use to supply the 3.3 (V) rail.

Thank you for your time.


texts: Addressable like 7-segments number display

texts:
Scenario

I'm planing to start a project that is a number display. It consists in 2 components:

The controller: a smart component that knows which number to display
The (single) digit: it display a single number;

I'd like to make them "chainable": [digit] + ... + [digit] + [controller].

From right to left: we start with a controller. It knows which number to display. The controller pass this information to its left side, that is a digit and the information should be send to all digits in the chain.

Please, ignore the complexity of the controller or how it knows the number to display.

Despite the title, I'm not using the 7-segments component. I'd like to 3D print a big 8-shape, and fill it with LEDs.

How should I build the digit?

I have 2 options in mind.

Options:

The digit has 7 addressable RGB LEDs. In this case, the controller sends a signal to control each individual led, in each digit.
The digit has 7 non-addressable RGB LEDs + a microcontroller. From right to left, the first digit receives a number (eg: 1234), displays the "4", and pass the rest to its left side. The next digit do the same, displaying the 3.

Questions:

For option 1:

Can the controller "auto discover" the total number of addressable RGB LEDs?
Maybe, each segment needs more LEDs (2 or 3) depending on size. Meaning that each digit could be 14 or 21 LEDs. A 10 digits number would have up to 210 addressable LEDs. Is it a problem?

For option 2:

Which microcontroller is recommended for this setup? It should receive an information (if possible, a string), parse it, and pass some other information.

And a last question: is there an big price difference between these options?

For this long text. But I'd like to hear from people more experienced before start.

Thanks


texts:
2 years ago, bought a name brand cordless VSR drill motor with a 12 V battery pack for only $20.
(I realize now, it was on clearance, as Manufacturer moved to a line of 20 V interchangeables...so it had been on shelf a while.)
Been happy, but now it's not putting out much work before dieing.
Checked charger module that came with it (it looks like a regular AC/DC converter, with a 90 plug going to handle, so you won't try to use it plugged in).

Charger label says output is 24V DC 1 amp: is that too much?

I put multimeter to it: read 30 V, is THAT too much?
(Is that a bad reading if the 9V in the multimeter is a little low?)

There is no indicator light on this model charger, or product, so I tended to leave it plugged in a lot, since, when I left it UN-plugged, it would go half dead, or all dead, after a week or so...

was this 'over-charging' and bad for it?

The battery is ten NiMh cells,  1.2 V - 1000 mAh:

Will it damage the drill motor and/or circuits in it, to put a 18v, or 24 V pack on it? (IDK if the connector/latch would even be compatible...)

I have read about people 'jump starting' cells that go into a charging station (usually in pairs, I guess); is this something I can do to the cells in this battery?  (I opened the case, and all the tabs' welds are intact; I tested cells, some show over 1.1 V, but a couple show like 0.1 V.)

Can those cells be jumped to facilitate charging?
At this point, the battery pretty useless, and cost of repair is almost more than getting a whole new deal...
Thank you!


texts: LTSPICE: How to display traces automatically when press Run Button?

texts: I have a question related to LTSPICE. Some of the examples placed in Educational folder have this feature (i.e. when I press Run button, automatically some traces appear). I analyze example, but I don't find a command, an option or a directive able to make appearing trace automatically. Any idea?


texts: Problems Getting NPN Bipolar Transistor to Switch On

texts:
I am working on a circuit that controls the power to another circuit.

As you can see in the schematic, when the switches are closed, current runs through the circuit, and no positive voltage is applied to the base of the transistor. However, when the switches are open, a positive voltage applied at the base allows current to flow through, switching on the relay and powering the "noise maker."

My problem:
I cannot seem to get the transistor to switch on when I open the switches. I tried checking the current flowing through the transistor, but simply touching the leads to collector/emitter causes the transistor to switch on.

So I know all the components are correct and that the rest of the circuit is working.

How can I solve this problem? I understand that for this NPN transistor, I need to apply voltage ~0.6 volts greater at the base than that at the emitter. Also, the voltage at the collector must be more positive than that at the base. If this is my problem, how can I adjust these values?

Edited to add part details:
- Circuit includes 2N222 Bipolar Transistor, 1N4001 Diode, HLS-14F3L-DC12V-C Relay


texts:
I'm trying to convert 11-16 Vdc to 5 Vdc @ 3 A to run an array of low-impedance ratiometric sensors.  The outputs are going either directly into an ADC or amplified through an instrument amplifier.  Either way I need fairly low noise (<5mV).

To achive this I'm thinking about either using a switching supply to 6-7v and then a linear regulator or just a quality low noise switcher.  The problem is I'm not a power guy and I don't really know what the best options in terms of parts for the switcher and linear regulator would be.  Looking around a bit most high current linear regulators have pretty poor PSRR at switching frequencies.

What are good choices for ICs?


texts: Why does the overshoot exist when transmitter turns on?

texts:
I am implementing power amp. with 16-QAM. Because of issue on power consumption, I am using time division duplex (TDD). By TDD, the power amp. turns off if the carrier wave is not needed and vice versa.
As represented in the figure, PLL makes 4 output signals P0~P270 with 90 degrees difference each. When PA turns off, the switch between PLL and PA disables to block AC signals.
Here is the issue:
There exist some overshoots when the power amp. turns on by TDD.
Does anyone experienced this overshoot when the transmitter turns on? What would be the reason?


texts:
This PCB is supposed to have 12-15V and 0.5A of current. How I should provide power to it? As I understand +V(as +) and OUT(as -) are places where power should be. Could I buy some adapter and solder plug for it? But there seems to be no place for it...

Detailed scheme:

General view:


texts: Characterization of an Amplification/ADC circuit

texts:
I build a small amplification circuit in order to amplify the low voltage signals of my passive sensors (the sensors have a source impedance of about 50-200 Ohm and they output a low voltage signal in the range of 0-20mV. The sensor output changes very very slowly as they measure sun irradiation and the sensors respond very slow as well, respond time >20 sec).

The hardware I build consists an instrumentation amplifier (AD8237: Datasheet) and a high resolution ADC (MCP3422: Datasheet). Please see the schematic below for a better understanding:

simulate this circuit – Schematic created using CircuitLab

Now that the hardware is ready I was thinking about how to characterize the circuit.
I began by getting familiar with the most important specs of the components I used (gain, offset, DNL, INL, linerarity etc.). Basically the values of interest I will need to evaluate during the characterization of my custom board.

Also I came accross this website that has a neat little overview regarding ADC characterization: Link.

The first thing that came to my mind is the use of a signal/function generator.

| Question |

How would you go about doing the characterization in my case?
I think in my case for sure I should apply the test signal at the input of the instrumentation-amplifier as all components are going to introduce noise/offest/errors and to do a good compensation for these errors later in the digital domain (in software) I should include the whole signal chain (complete circuit) in the evaluation/characterization.

My first idea was to hook up the non-inverting input of the circuit to a signal generator and start a DC-sweep/ramp within the valid range of the sensors I will use (0-20mV).
The inverting input of the amplifier would be tied to common ground during the tests (however as you see in the provided schematic I will use differential measurement in my final setup with the sensors). Any other ideas or thoughts on that? Should I even hook up two function generators for this (one on every pin of the instrumentation amplifier)?

How about impedance issues? As the inputs on the INA are high impedance (100 MOhm) and my sensors will have a low output impedance (about 100 Ohm) I guess that my signal generator should also exhibit similar conditions. I guess It would be sufficient to just select a 50 Ohm output impedance for the probe of the signal generator? Any other pitfalls?

So this is my basic idea: Hook it up to a signal generator, driving it with a DC ramp and taking digital values for some defined DC-points from the ADC (still not sure how to automate this process, are there options to connect signal generators to a computer and synchronizing the DC-ramp with the ADC readings?).
I would appreciate any input from experienced people how to do it the best way, any insights on past experiences, pitfalls, best practices is welcome (as the basic idea is there but I'm still pretty clueless regarding the practical execution).

Thank you very much.


texts: How to use zener diode for negative voltages?

texts:
Every one may be familiar with zener diode function in positive voltages but I don't know how to use them in negative voltages.

For example in the schematic below, if we use a 10v zener and the input voltage is around 12v, we can expect a rather 10v output, but if we reverse it for a negative voltage as in schematic number 2 ( ground is now a positive voltage compared to -12v), all we get is power dissipation ( because it tries to bring down the ground voltage and as it is impossible, the diode just starts getting hot). What is the correct design for using a zener for negative voltages?

1- Positive Voltage:

2- Negative Voltage:


texts: Multiple Broken Relays -- What About My Circuit Is Making Them Fail?

texts:
I recently purchased one of these relay boards ...

to use along with my Raspberry Pi to switch an AC outlet on/off to control a fountain pump. Since the relay board requires 5V for the control lines and needs to pull more current (IIRC) than the RPi can supply on 5V, I put together this little circuit to test out my system:

simulate this circuit – Schematic created using CircuitLab

Relay Schematic:

I know that my "To Relay Control" line is only going to pull down to ~.3V when the RPi GPIO is high, but it was enough to toggle the relay, so I went with it.  I have software that turns the pump on 15 minutes out of every hour, and the system was functioning fine for a few hours.  However, after a few (~8) hours of operating the relay is no longer switching -- even if I pull the "To Relay Control" line directly to ground the relay will not flip into the "on" position.  I thought this might have just been a random bad part, but I switched to another relay on that board and had the same problem after running fine for a few hours.  The LED on the relay board lights up when the line is pulled low, but that's it, I don't hear a "click" out of the relays anymore when I toggle them.

Is there something about my test circuit that is causing these relays to fail?  In general, what would cause a relay to fail in the manner that I've described?


texts: How to get instantaneous voltages in everycircuit?

texts:
What i want to do is to add scope probes to nodes between resistors and then run a transient analysis for 5ms in order to see the measured voltages for those nodes at exactly 1.25ms. Is there any way to do this in everycircuit? I added those voltmeters just because i have no idea how to achieve my goal. Google doesn't seem to help.

Edit:

everycircuit is pretty bad for this. Use this one or LTspice


texts: ADC with programmable quantization levels

texts:
Does anybody know if there are ADCs with programmable threshold levels?

The continuous signal is a radar signal which is to be digitized with an ADC with controllable qunatization levels.

I am not looking for a software or etc. I want to know if such ADC is available or not.


texts: What are the reasons that the emitter is heavily doped in an NPN BJT?

texts:
Is doping the emitter more than the collector crucial?
Would current not flow at all if both regions were equally doped? Why?
Is there a way to explain this in a simple fashion?


texts: For instance RG-6, RG-58, RG-59 and RG-173? Also do the numbers have a specific meaning (like referring to a part of the specification)? Is there a document that lists all RG-* cables with their specifications?


texts: Creating a new power source for light-string ornaments

texts:
I have a couple Hallmark Star Trek ornaments that plug into Christmas light strings.  I'd like to convert the power supply to them from the light string plugged in the wall to a battery pack so I'm not anchored to a string of lights and to better protect them**.  My experience with electronics is minimal so I'm having a hard time even Googling for where to begin.  The box for one of the ornaments says to use it with light strings of 2.5, 3.5, or 6-volt bulbs.  The other says us strings with multiples of 35 or 50 lights - it needs 6 volts, 1.2 watts.  The plugs on the ornaments are the push-in T1¾ style if that helps.

Just going with the 6 volts that each can handle... I assume plugging in a 4 pack of C cell batteries would do nothing or damage it with the constant current going in one direction.  I assume I need to convert my battery pack from DC to AC.  Is this feasible without breaking the bank and without having a brick-sized box of electronics for each ornament?

** regarding the protection, they're both almost 20 years old (wow, I'm old) and, with them currently on AC, I'm worried about a brown-out stressing them or power spike just zapping them. I'd like to have whatever electrical protection I can reasonably add (fuses, resistors, etc.) inline with the battery pack.


texts:
I need to display the voltage at the probe, varying the Vout1 from 0 to 67mV and I expect the voltage to be 0.1V to 0.5,  but my simulation stops way before 0.5V. I have checked the calculations and they are correct, also tried with an ideal opamp and it works.

How can I solve this, any ideas?

EDIT:

It's supposed to display at the probe a voltage of 100mV when the Vout is 0 and a voltage of 0.2 mV when the vout is 67mV.
It controls the gain of the Vout.
Actually it works when I use the ideal opamp, my question is what kind of opamp should I use to get my results..


texts: In PCIe, why are config writes non-posted?  Why can't they be like mem_wr which are posted?


texts: Validity of AWADDR once AWREADY is asserted in AXI4-Lite interface

texts:
This question is a follow-up to Relationship between AWVALID and WVALID in AXI4-Lite interface, from which I learned that AWVALID and WVALID have no specific timing relationship.
Now I have a slightly different question. If AWREADY is asserted in response to AWVALID, is there any guarantee that AWADDR will stay asserted till WREADY, BVALID, or BREADY is asserted? I'm only asking this because I have seen some codes that look at WVALID alone for completing the write operations. They totally neglect AWVALID and keeps AWREADY=1 at all times, with the assumption that AWADDR will be valid. Is this perfectly fine to do?


texts:
I have a battery powered device that runs from 4 AA batteries. Whilst testing, I am wanting to power it from an adjustable bench power supply.

How can I work out what amperage to set my bench supply at? Do AA batteries have a standard amp rating? There is nothing mentioned on the battery itself.


texts:
I have a small laser diode I ripped out of a CD/DVD read write drive. It has 3 pins on it and my first question is what function does the third pin have? Is it a second ground? How do I go about determining the function of each pin safely without damaging it?

I'm attaching a photo of a driver circuit I found online. Would this be a suitable driver circuit for this laser diode? I'm not for sure on the specs of the diode but I'm guessing it's more than 100mW.

Furthermore, in a driver circuit for a laser I need to regulate not only voltage but current as well. Therefore, I'm confused on how I'm supposed to design a circuit that satisfies both of these conditions. For some reason as beginner electronic engineering student I can only make sense of having one of these regulators in a circuit controlling voltage OR current. To me, changing one would effect the other. So how can I control both since controlling one will control the other.


texts: Can a processor do a for loop within 1 clock pulse?

texts:
I am in a digital circuits class.  In this class we are using verilog to simulate (but not actually physically synthesize) different circuits. We have an assignment where we are supposed to simulate a circuit and one of the requirements makes it so there must be a for loop with a basic calculation in one clock pulse:

always@(posedge clock)
    for (i=0; i<11; i=i+1) begin
        if (i*i == data)
            isPerfectSquare = 1;
    end

What I am wondering is if this circuit is actually possible to implement in real hardware and not just simulate.  To me it seems impossible to fit an entire for loop within one clock pulse because a for loop would require registers that are updated ON the clock pulse.  The way I see it you would need at least 1 clock pulse per iteration.  Am I correct or is it actually possible to build a circuit that represents a for loop within a single clock pulse?


texts:
I need to build fast level converter, 5V in -> 12V out using transistors.

I've seen Voltage level shifter , but it drives output high using resistor pull-up, and it's slooooow....

I have 100-1000pf load and need some 15-100ns fronts.

Any suggestion on how this should be done?

PS. I have both +12V and +5V power rails.


texts: Powercast Powerharvester Chipset PCC110 Issues

texts:
I recently picked up a PCC110 datasheet, an RF energy harvester. I assumed the 3 pins would correspond to GND, Antenna, and Vout (the datasheet does not specify).

I attempted all of the permutations for the pins in a relatively radio noisy location, but I was unable to detect any current (uA range) across a simple load. I wasn't expecting the rated max of 50mA, but not even a uA?

Is there something I am missing? Do these devices work in ambient radio environments, without the Powercast booster station? The device is quite small and I had a difficult time soldering the connections; could I have damaged the device with the heat?


texts:
I'm in my 3rd year of my electrical eng. degree. I have a project right now, where I must create a PID controller for implementation. They gave me the exact values for constants Kp, Ki, Kd and the maximum acceptable frequency.
My integrator circuit is based on the Miller integrator, but with a resistance in parallel with the capacitor, so I can have constant gain with low frequency signals.
My question is: How do I choose or calculate the values of the resistances and the capacitor, based on the max frequency they give me and the integration constant Ki?
My integrator looks like this picture:

Image source: Electronics Tutorials - AC Op-amp Integrator with DC Gain Control
I uploaded a photo of the PID i am trying to use. Feel free to point any erros. It uses a proporcional, integral and differentiator components and then a inverting summing op amp.


texts:
There was an UV Led lying around, I wanted to check bank notes with it. I soldered a 3W led on PCB. And powered it with 4 AA batteries (connected in series)

The light was bright and purple. (I mean, visible)

So I guess that wavelength was not small.

Because of my ignorance; I touched the LED to check if it was overheated (and it was), and looked directly at it. I do not have any sight issues for the moment, but what I read on internet made me fear.

Is there any possibilty that my finger got harmed? Does visible violet LEDs cause any illnesses such as skin cancer?

By the way, the exposure and the contact (I touched the LED) lasted both approximately 20 seconds.

Thank you in advance.


texts: Wire up multiple slave Arduino devices to a master Arduino device

texts:
I want to use serial communication between a master and multiple slaves.

I've already connected the RX of the master to the TX pins of both slaves, and vice versa (thus connected the TX pin of the master to the RX pins of both slaves). I also connected the GND pins.

But now I got weird characters when I open the serial monitor window.

Now how do I properly connect a master Arduino device with at least two slave Arduino devices using the RX and TX pins? Do I need to connect 5V pins?

PS: I see a lot of words like "SPI" and "I2C", and people start using terminology. But I'm not thát experienced, so please, if using the terms, explain them.
Another PS: I want the Arduino devices to use power from the master Arduino device.


texts: Copper layer delaminates on Printed Circuit Board

texts:
I have been making the PCB boards by the conventional process since last few years (pressing, etching, drilling, soldering).

I usually iron the photo paper to the PCB board for around 15-20 minutes but this time something unusual happened and the PCB board had this shape. The copper rose from the board while I was pressing and left it in this shape:

This is my first encounter, can anyone suggest why this happened? I pressed for only 6 minutes.


texts:
So I've confirmed the Thevenin voltage ( between A and B ) to be .5V and a the VLoad as .3633V. I'm now supposed to verify that RLoad is 4k by redrawing the circuit as its Thevenin equivalent and using voltage division.

My Thevenin resistance was 1.125k. I shorted V1 and opened I1, then combined R2 + R6 in series as well as R3 + R5 in series. Then I combined the three remaining resistors in parallel.

When I use voltage division, I get VLoad = .3912V, which is of course greater than .3633. Is there something wrong with my process or calculations that anyone can see?

Thanks for any help!


texts: What if I use 4 pin XLR instead of the 3 pin one?

texts:
I'm a guitar player and my knowledge about connectors and stuff is very disappointing.
I use a wireless device to play live and the cable I use to plug the guitar is a Jack to mini XLR (3 pin) cable, such as this:

However, the quality of this cable is dreadfull as it is a lowcost cable. So I was searching for a better one and saw this one:

The problem is this XLR connector is a 4 pinned one.

So here goes my question:

Will it make any difference if I plug a 4 pinned XLR instead of a 3 pinned one, as the extra pin will not be plugged anywhere?

What I think is, since the jack is 2 pinned the 3rd and 4th pin would not be used anyway.

I hope everything is clear to you, thanks!

Thanks, after reading all your quick responses I've decided that the way to go would be to make my own cable out of connectors and wire.


texts: Input current to a non-isolated boost converter

texts:
I am measuring the current at the input to a non isolated boost converter.
See Fig 1

I am measuring different currents on the positive input and the negative input terminals to the boost converter.
I am not sure why this is the case.
Here are some examples of the input currents measured:
Measurement 1

+ve side input current: 5.045 A
-ve side input current: 3.359 A

Measurement 2

+ve side input current: 10.090 A
-ve side input current: 7.929 A

DC current measurements in both cases. Measured with 2 x shunts. Shunt 1 connected between the DC input source positive and the positive input of the boost converter, shunt 2 connected between DC input source negative and the negative input of the boost converter.
The boost converter in this case regulates the input current.
The power supply connected to the boost converter input is floating from earth ground. The output side of the boost converter is also floating from earth ground.
I am trying to understand these results.
Why is the negative side input current measured lower than the positive input side current?
Can you suggests some tests I could carry out to understand this better if necessary?


texts: Formula to calculate heating time of nichrome?

texts:
Is there a formula to calculate how long it will take for a nichrome (NiCr-A) rod of given dimensions to heat up to a certain temperature (or maximum temperature) for a given supply of AC or DC current and voltage to the rod.
Assume the rod is surrounded by stationary air at ambient temperature (~25°C).


texts: How do I choose a cable /cord, connected to mains part, that is compliant with IEC 60601-1 3rd ed.?

texts: IEC 60601-1 is a standard for medical devices. It describes which are the requirements for the Means of Operator Protection and Means of Patient Protection, the current leakages and so on. I don't understand which are the standard cables/cords that can be considered having 2 x MOPP up to 250Vac.


texts:
I was trying to figure out the real reasons why USB signals are converted to RS232 serial. I came to understand that(if I am not wrong) USB is faster and synchronous, whereas the chips are using UART which needs RS232 protocol.

Are all the chips designed for TTL(RS232) serial data communication? Is that the reason USB is never directly used for data communication with integrated circuits?

And one more thing related. When we are uploading sketch(code) to the Arduino micro-controller, we configure the baudrate first i.e. 9600. I think this is the data transfer speed from USB to Arduino. If USB is converted to RS 232 before reaching to the UART of the ATMEGA what is changing? Voltage level? Baudrate? Is the baudrate still 9600 at the UART?


texts: Is the ALU control unit enough to execute all the instructions in a MIPS processor?

texts:
The ALU control unit dictates the operation to be done by the ALU. It's truth table though describes only 7 operations, which are enlisted in the truth table below.

How the processor handles the rest of the instructions like XOR, NOR, Shifts etc.?

Should I extend the ALU Control Unit and include this instructions? Send the opcode through registers to the ALU stage and decode there also? Or something else?

None of this is explained in either MIPS diagrams or ALU Control Unit tables I looked at.


texts: How does using a 60Hz device on a 50Hz supply affect it?

texts:
I've two Vibro Graver electric engravers (120V 60Hz) with me. I gave one to a friend who recently moved to another country. He got a step down converter from 220V to 110V but then he noticed the frequency used there is 50Hz.

What would the effects of using the device on a 110V 50Hz supply when the device is meant to be used on 120V 60Hz supply. Does the 10Hz difference cause any damage?

Edit: The voltage is stepped down from 220V 50Hz to 110V 50Hz
Img 1