texts: Assigning to a parameterized 2d Verilog array

texts:
I have a Verilog array defined as :
logic [ 0 : num_elements - 1 ] [ element_width - 1 ] some_array ;

I want to assign every array element with a vector that is all ones: "11...1".
I tried this but I get an error:
some_array <= { num_elements { element_width { 1'b1 } } } ;

What's the correct syntax ?


texts: newbie confused with PCB designing a TO3 transistor

texts:
hi guys im a first year electronics student with no background on PCB designing or anything and im confused on how to connect this collectors of a to3 transistor into the capacitor

cause the collector the transistor is its body

i have to fit it all in 2x6 inch pcb

thanks in advance


texts: Can I estimate the leakage inductance of a power transformer taken from a catalogue?

texts:
I'm using PLECS to simulate an HVDC system and I've been using two ideal transformers (Y/Y & Y/D) in order to get a 12-pulse rectification. However, now I want to consider real parameters. PLECS gives me this box to replace leakage inductance and winding resistance, as other specs, for every winding:

That being said, I've been searching for these parameters and some catalogues only include its impedance in %.

With this I can know the impedance in ohms but not 'separated' as R+wL. Do you have a different approach for this? Is there a typical proportional relation between R and L depending on voltage level or MVAs? Finally, is important to mention that I only want these values to have something 'real' but not too real as I will be studying the efficiency of a converter at the DC side (after 12-pulse rectification). In other words, as minimum I have to consider overlap angle due to leakage inductance.


texts: How to measure uA/mA current without breaking the circuit?

texts:
I was wondering if there is any known way of measuring DC current without breaking the circuit?
I have an application where breaking the circuit simply isn't an option but we still have to verify power consumption.

I'm aware of the following product but it's range is above what I need measure: http://www.aimtti.com/go/iprober/

Any thoughts are appreciated!


texts: Need some help here - I need to light up a normal LED with ONLY 1.5v; yes, 1.5V to light up an LED sounds ridiculous since we need a minimum of about 1.8V or more. But, is there any solution?


texts: Controlling an Electromagnet using a microcontroller

texts:
My question stems from this one here: Controlling an electromagnet strengh with arduino

Background

I am working on the classic magnetic levitation control systems problem. I have a 10N electromagnet (150 mH, 40 ohms) that will be used to levitate a steel ball. I will be using an optical time of flight sensor to determine the balls position. I plan on going above and beyond the typical undergrad magnetic levitation problem by allowing the set point (ball height) to be changed on the fly, similar to this video.

I took non-linear control systems course in grad school so I am aware this is a difficult problem. We never went beyond the theory though, so I thought this would be a fun problem to extend my learning.

The Problem

The control system I derived expects that the input variable (the voltage applied to the electromagnet) is a continuously varying DC voltage. I've been looking at using a DAC, but they are relatively expensive and don't seem to be designed for power applications. PWM seems like the way to go, but I am struggling finding a way to model the PWM system; a square wave is not mathematically friendly.

The Question

What is the best solution for the problem: using something like a DAC or PWM? I need to create a fast-acting (< 1ms delay), accurate control signal.

If PWM is the best solution, how would I go about modeling it in a control system?


texts:
Consider the following circuit,

Running an AC simulation,

Now consider this,

Running an AC simulation,

How come with the RC circuit, we have a constant -90 phase shift. I don't understand how the "voltage lags current by 90 degrees" comes into play here. Surely, we're just plotting the transfer function right (i.e Vout/Vin) so who cares about current? And even if a capacitor provides a constant -90 degree shift, why doesn't it happen with just the capacitor circuit?


texts: Wireless DC Motor & Linear Actuator Control

texts:
These are the 2 items that I have:

24V 110RPM 1Amp DC Motor.
24V 100mm Linear Actuator.

First Question: To run the DC Motor I am thinking of getting this 24V 2A power supply in the hope that both of the items can run off it. Would this be wise? The linear actuator will only run very rarely, while the motor will be running for long periods of time.

Second Question: I want to control both of these wirelessly. I can find plenty of examples of a dual push button remote to control linear actuators via wireless, however, I want to control the speed of the DC motor via a control dial like this, but am not sure how to make a wireless version. Does anyone have any recommendations please?


texts:
I am beginning my study of electrical engineering and I apologize in advance if this question has been asked or if this question does not make any sense. I was wondering why short circuits are "bad" and complete circuits are "good".

From what I understand, when you have a battery, and short the two terminals together, you introduce a large current into the battery causing it to overheat and possibly combust.

simulate this circuit – Schematic created using CircuitLab

However, when you add some form of resistance to the circuit, you create a complete circuit and the battery source is not in jeopardy of overheating.

simulate this circuit

My question is, is there not current flowing into the battery in a complete circuit? How come the battery is unable to handle the current under its own voltage? And if some form of resistance on the circuit is required in order to prevent a short circuit scenario, how much of a resistance do I need, in order to prevent the battery from overheating? Thanks in advance. Cheers.


texts: How do you calculate the current and voltage when the emitter is grounded for saturation mode

texts:
For example, assume you have this transistor with a grounded emitter:

Since we are dealing with a saturation mode, \$v_{ce} = 0.2 \$ making the drop across the resistor 9.8 v. The current going through the collector is \$ I_c = 9.8/10 k\Omega = 9.8 mA \$ and assuming \$ \beta = 100 \$ then \$I_b = 0.098 mA \$. But \$v_c = I_c \times R_c = 9.8\$ volts. For a transistor to be considered in the saturation mode \$v_c < v_b \$

My textbook has some contradictory statements about saturation mode. In the beginning of the course, we learned that when a transistor is in saturation mode, the collector should read close to zero volts. The book now says that when a HIGH (> 2 volts) is applied to the input supplied to the transistor's base, it will cause the transistor to conduct and the collector voltage drops to a LOW. But in the calculation from above (assuming that it was done correctly), I can clearly see that the voltage on the collector is 9.8 volts, close to 10 volts and not anywhere close to zero or LOW.

EDIT: Am I suppose to assume that \$v_c = v_{cc} - I_c \times R_c = 0.2\$. Since the emitter is grounded, \$v_c = v_{ce}\$


texts: Why is it required to put an external inductor and diode at the output of a step-down switching voltage regulator?

texts:
I'm using a LM2576 switching voltage regulator and I see that an inductor and a Schottky diode are required at the output.
The schematics is below:

I understand why the capacitors are there, but why is the inductor required? Is it used for filtering purposes?
Why is the diode there? Can I put a normal diode instead of a Schottky one?


texts: How to design a crystal oscillator circuit

texts:
I need to produce a 32.768KHz frequency for a binary counter but I have no idea how to design a crystal oscillator circuit.
I tried multiple simulations in Proteus 8 but always failed in making it oscillate.
Can you please tell how should one generate an oscillating signal for a circuit?
I am trying to use a 74HCT93 counter.


texts: Charge controller same volts "input" as "output"

texts:
I have bought a Steca Solsum 10.10F and I am having some problems with it.
I would like to ask you guys and gals some advice to figure out if it's a problem from my side or if it a problem with the charger control.

I have 2x40Watts solar panels connected to the charger control and from there to a AGM battery.

In between this points I have devices to measure (Watts Up? Meters and other digital multimeters) Volts/Amps.... in this way I am trying to see what is going in and what is going out....

If I do not plug the solar panels to the charge controller I am reading from 19V to 20V... and after connecting it to the charge controller I read around 12.9Volts in the "input" as well on the "output"?

My AGM battery should need 14.4 to 14.7Volts in order to cycle.....

I read the user manual for this charger control and according to the specifications the DC output should go to 14.4V (Boost charge voltage).... unfortunately, no matter the sun/sky conditions I never saw higher than 12.9 volts...

Am I doing something wrong? or what is the problem?


texts:
I have 6 18650 Li-Ion cell from a very old Dell laptop. Unfortunately I could not find any info about them from their markings.

They were connected as 3S2P with a total of 11.1V and 4700mAh.

Measured each cell individually and all read 3.7V or very close.

I'm charging one with a bench supply starting with 4.15V and 1A. Read somewhere that 0.5C would be safe, and if I got it right 1C=2.35A.

Now, the weird thing is, that after it gets down to about 300mA charging current, it starts increasing. What's going on? Should I be worried?

Thanks.


texts:
As far as I know, SCRs are basically the DC-only cousin of a TRIAC. However, in my travels I have not encountered a TRIAC being much different in price than a similarly spec'd SCR, so I guess I don't really understand the point of SCRs from an applications point of view.

To clarify, I understand the fundamental differences in operation between the devices, but I don't see why, from an applications point of view why SCRs would even be manufactured. It seems that if you buy an SCR, you are buying half the "features" of a TRIAC for approximately the same price. In what instance would you only want to use an SCR? Is it merely that you want to only conduct an AC waveform in one direction?


texts: Help in plugging equation in arbritrary current source LTSpice

texts: I cannot plug in the following equation and parameters in arbitrary current source. Any help would very appreciated. ltspice cannot read my parameters..


texts: How to control the power to an LED strip using a micro switch?

texts:
I've never worked with electronics before so I want to be sure I do things correctly and safely.
I have this LED strip which is powered by a 5V USB port. I would like to control the power to the strip using a micro limit switch similar to this one.
Is it safe to just splice the switch in-between the power adaptor and LED strip? If not, what is the proper way to achieve my goal? Thank you in advance.


texts:
Here is a simple audio amp. Is there an easy way to calculate the power it gives?

edit
Resistor value, input level and speaker impedance changed.


texts: Is there a good solution to connect Segger J-Link to a solderless breadboard?

texts:
I am working on a project where I created different prototypes on different solderless breadboards. To program and debug the used MCU using SWD, I just use male jumper wires, from the j-link connector to the pins of the MCU on the breadboard.

Now, I would like to cycle through the different iterations of the project, which are on different solderless breadboards. But every time I have to carefully reconnect the jumper wires from one breadboard to another.

Is there any better solution to this? So I can faster and especially safer switch the J-Link connection between the different solderless breadboards.


texts: How do I source an Audibly noiseless (< 3dBA) power supply?

texts:
This is not a shopping question; this is a "what is the best way to solve this problem" question.

To power a medium-size project, I'm looking for a 15W/12V board mount power supply, taking mains AC in (auto-switching voltage is nice, although US-only would be acceptable) and providing reasonably-regulated 12VDC out.

I first tried the cheapest thing I could find on DigiKey with parametric search: a 35W Delta PSU, cageless (plain board.) Unfortunately, it had quite significant coil noise, which is right out for this application -- the device will be in a bedroom and ears are very picky about coil whine. As clarified in the comments, I'm looking for something as low as 3 dBA audible noise at 1 meter.

Second, I tried a more expensive model, with a perforated case: a 25W TDK/Lambda. It, too, has coil noise, although less of it. But, this is still too much.

I understand why the coil noise happens: These switching power supplies regulate the voltage by sending a signal all the way to the mains side, using a flyback regulator.
But, this is not acceptable to me.

Unfortunately, I have not found any parametric search (digi-key, mouser, farnell, jameco) that rates board mount power supplies on noise. And they don't even advertise the topology used -- a transformer-based down converter with buck topology on the DC side would probably be fine for my needs, for example.

So, other than buying one of each of everything in stock, which I can't really afford to do, how can I find a power supply that doesn't make any noise? If you had this design requirement, how would you solve it?


texts: I am not getting output I want in ModelSim - Altera (perhaps something related to timing requirements not being met?)

texts:
I am writing some basic verilog code that blinks an LED at some frequency. The code is the following:

module FPGA_Testing( input clk, output wire LED);

    reg [32:0] counter;
    reg state;

    always @ (posedge clk) begin
        counter <= counter + 1;
        state <= counter[20];

    end

    assign LED =  state;

endmodule

and the testbench is here

`timescale 1ns/1ns

module FPGA_Testing_tb;

     reg clk;
     wire LED;

     FPGA_Testing test(.clk(clk), .LED(LED));

    initial
    begin
        clk = 0;
    end

    always
        #5 clk = ~ clk;

endmodule

When I compile, I don't get any errors, but I do get the following warnings

Warning (18236): Number of processors has not been specified which may cause overloading on shared machines.  Set the global assignment NUM_PARALLEL_PROCESSORS in your QSF to an appropriate value for best performance.
Warning (18236): Number of processors has not been specified which may cause overloading on shared machines.  Set the global assignment NUM_PARALLEL_PROCESSORS in your QSF to an appropriate value for best performance.
Warning (292013): Feature LogicLock is only available with a valid subscription license. You can purchase a software subscription to gain full access to this feature.
Warning (15714): Some pins have incomplete I/O assignments. Refer to the I/O Assignment Warnings report for details
Critical Warning (169085): No exact pin location assignment(s) for 2 pins of 2 total pins. For the list of pins please refer to the I/O Assignment Warnings table in the fitter report.
Critical Warning (332012): Synopsys Design Constraints File file not found: 'FPGA_Testing.sdc'. A Synopsys Design Constraints File is required by the TimeQuest Timing Analyzer to get proper timing constraints. Without it, the Compiler will not properly optimize the design.
Warning (18236): Number of processors has not been specified which may cause overloading on shared machines.  Set the global assignment NUM_PARALLEL_PROCESSORS in your QSF to an appropriate value for best performance.
Warning (18236): Number of processors has not been specified which may cause overloading on shared machines.  Set the global assignment NUM_PARALLEL_PROCESSORS in your QSF to an appropriate value for best performance.
Critical Warning (332012): Synopsys Design Constraints File file not found: 'FPGA_Testing.sdc'. A Synopsys Design Constraints File is required by the TimeQuest Timing Analyzer to get proper timing constraints. Without it, the Compiler will not properly optimize the design.
Critical Warning (332148): Timing requirements not met
    Info (11105): For recommendations on closing timing, run Report Timing Closure Recommendations in the TimeQuest Timing Analyzer.
Critical Warning (332148): Timing requirements not met
    Info (11105): For recommendations on closing timing, run Report Timing Closure Recommendations in the TimeQuest Timing Analyzer.
Critical Warning (332148): Timing requirements not met
    Info (11105): For recommendations on closing timing, run Report Timing Closure Recommendations in the TimeQuest Timing Analyzer.
Warning (18236): Number of processors has not been specified which may cause overloading on shared machines.  Set the global assignment NUM_PARALLEL_PROCESSORS in your QSF to an appropriate value for best performance.
Warning: Warning: File FPGA_Testing_run_msim_rtl_verilog.do already exists - backing up current file as FPGA_Testing_run_msim_rtl_verilog.do.bak7
Warning: Warning: File FPGA_Testing_run_msim_gate_verilog.do already exists - backing up current file as FPGA_Testing_run_msim_gate_verilog.do.bak11

Afterwards, when I run modelsim, I see the clk in the testbench oscillate, but all the other variables remain low or high the entire time:

I don't know why the waveform is showing the other variables change. I don't know why I am getting a timing requirements not met warning. And I don't know whether or not the two are related.


texts:
I've started playing with electronics a while ago and making simple logic gates using transistors. I know modern integrated circuits use CMOS instead of transistor-transistor logic. The thing I can't help wondering about is how CPUs are designed.

Is design still done at a (sub)logic gate level, or is there not much innovation in that area anymore and have we moved on to a higher level of abstraction? I understand how an ALU is built, but there is a lot more to CPUs than that.

Where do the designs for the billions of transistors come from? Are they mostly auto generated by software or is there still a lot of manual optimization?


texts: I need to do a DC sweep of a circuit involving a NMOS, but my version of Multisim doesn't have that option. Which free simulator would you recommend for a DC sweep?


texts: Component has a x% tolerance: What does this mean exactly?

texts:
All components have specification tolerances and ranges.  Some examples are:-

Resistor 1%

Electrolytic capacitor 20%

Zener diode breakdown voltage 5%

Clearly it kinda indicates that the specification may vary by x% from that stated.  So a 5%, 24V Zener diode may change it's breakdown voltage by 1.2V.  But this is a statistical measure.  So are they saying that you will never find one of these diodes with a 1.3V difference for as long as you live?  Or might one in ten exceed the 5% range.  It must be (somewhat normally) distributed around a mean, and the manufacturer must have measured several to arrive at a 5% figure.  Similarly, is there a percentage chance that a 1% resistor may actually be out by 1.5%?

If I were manufacturing precision thingies with thousands of resistors, I would need to know the statistics to a greater degree.  There must be a fair few resistors in a 12 core Xeon processor, so statistical considerations would be important.  I would have thought that perhaps a mean and standard deviation might be more appropriate in a data sheet of a part intended for large scale production.

The only examples of a statistical description I've seen is like this one for a LT1007 op amp:-

Is this what Linear Technology would call 3nV/root(Hz)?

My personal interest is that I'm trying to match some Zener diodes by the greatest degree reasonable.  Should I buy a 1000, or just measure the pack of 5 they came in?  Others do this with valves and transistors so I'm not crazy.


texts:
I order the REG1117-3.3V IC and after reading the REG1117 datasheet I found the following on page 8 :

  Figure 1 shows the basic hookup diagram for fixed-voltage
  models. All models require an output capacitor for proper
  operation, and for improving high-frequency load
  regulation; a 10µF tantalum capacitor is recommended.
  Aluminum electrolytic types of 50µF or greater can also be
  used. A high-quality capacitor should be used to assure
  that the ESR (Effective Series Resistance) is less than
  0.5Ω

I will use this regulator to power from microUSB (5V to 3.3V) an ESP8266 and several MPR121 (IC sensor). I was wondering which value for the ESR capacitor should I order ? I don't know which value for the capacitor because there is no other information on the minimal value to avoid instability.


texts: The energy of an inductor is \$\frac 12 LI^2\$ and a capacitor is \$\frac 12 CV^2\$. Why isn't the frequency also included in the formulas? As a higher frequency wave is more energetic than a low frequency wave.


texts:
I am looking for some microcontrollers with USB capabilities and some are said to have USB 2.0 HS Host/Device with PHY others say USB 2.0 HS OTG Host/Device with PHY.

I am not a specialist in the USB specifications, so I wonder, choosing a OTG part will have any set backs or limitations?

I am expecting OTG parts to behave just as regular USB parts do, so if I program my part to act as host, and I connect it with a regular USB 2.0 device, they will connect as usual.


texts: How to combine 5V-powered ATmega16A and MAX44009?

texts:
I'm programming my ATmega16A through LPT port using uisp -dprog=bsd. Although ATmega16A supports \$V_{CC}=2.7\,\mathrm V\,..\,5.5\,\mathrm V\$, to make logical levels compatible with LPT port, I have to supply 5V to the ATmega.

All works fine, but now I need to connect MAX44009 lux meter (working via I²C) to the controller. MAX44009 supports \$V_{CC}=1.7\,\mathrm V\,..\,3.6\,\mathrm V\$, which appears too low to safely input 5V to it.

For transmitting data I could use e.g. a voltage divider to supply a fraction of 5V to MAX44009, and pull-up the SDA and SCL lines to this power source. Since SDA & SCL are open drain, this would work fine as far as we're only driving MAX44009's input. But when we want to read data back, we have a problem: 3.6V doesn't seem to be good enough to be seen as high level input for 5V-powered ATmega.

So, how can I actually safely connect ATmega16A to MAX44009, without losing the ability to program ATmega via LPT port? Some web pages like this one simply suggest powering MAX44009 with 5V without explaining why. Others like this one say that working voltage is 3 ~ 5 V, which also looks strange.


texts:
I want to create an "Ambilight" using Raspberry Pi. But because this is more about electronics than the Pi itself I think here is a better place to ask this.

For different reasons I do not want to put the Pi directly near the LEDs, but have a distance of about 2 meters (6.5 feet).

The max. power consumption of the LEDs will be 60Watts. The Voltage is 5V.

Now I am a bit unsure about the diameter I need for the cable for this 5V DC. Is there a way to calculate this? I had something for 220V AC (according to the Ampere value) but don't know if this applies also to low Voltage and DC.

In Addition I need a "signal-cable" which switches the about 200 LEDs on and off in quite a fast way (my guess would be of a frequency somewhere in the kHz-Area). (also 5V, very low Ampere) What cable would be the right one for this? Coax Antenna-cable?


texts: Unable to flush TX FIFO queue of NRF24L01+

texts:
I am writing code for an ESP32 to send data using a NRF24L01+ module to another NRF24L01+ module connected to an Arduino Pro Mini. The Arduino can successfully send data to the ESP32. So everything is properly wired up and the RF settings are compatible. However, when I switch roles, no packets are received on the Arduino and all transmitted packets set the MAX_RT (maximum retries reached) flag in the status register (on the ESP32 side).

The strangest thing is that I'm unable to flush the TX FIFO queue, which one is supposed to do to continue with the next package. Sending 0xE1 to the RF module seems to have no effect. After three failed packets, both the STATUS and the FIFO_STATUS register indicate TX FIFO full. And no amount of flush commands can clear it.

Question: Why does the FLUSH_TX command have no effect?

The code is written in C for the ESP32 SDK (aka ESP32 IDF) based on FreeRTOS. The communication is a simple unidirectional communication: either end is either sender or receiver only.

I've already ruled out many things:

I have verified the SPI communication with a logic analyzer and not found a problem.
I have compared the SPI communication of the ESP32 to the Arduino and they are almost identical. Main differences: timing; and ESP32 code stores configuration registers in memory to reduce number of register reads.
I have swapped the NRF24L01+ modules with no effect.
I have added a 47µF capacitor between GND and VCC close to the RF module.

Here's a dump of most of the registers:

STATUS = 0x0f: RX_DR=0 TX_DS=0 MAX_RT=0 RX_P_NO=1 TX_FULL=1
FIFO_STATUS = 0x21
RX_ADDR_P0 = 0x38a8bb7201
RX_ADDR_P1 = 0x389f30cc1b
RX_ADDR_P2-5 = 0xc3 0xc4 0xc5 0xc6
TX_ADDR = 0x38a8bb7201
RX_PW_P0-6 = 0x20 0x20 0x00 0x00 0x00 0x00
EN_AA = 0x3f
EN_RXADDR = 0x03
SETUP_AW = 0x03
REG_SETUP_RETR = 0x5f
RF_CH = 0x52
RF_SETUP = 0x03
CONFIG = 0x0e
DYNPD/FEATURE = 0x00 0x00


texts:
Im trying to connect a MIDI input cable to an arduino. To do that, I need an optocoupler, that secures the internal circuits from damage.

This is the schematic as shown by the MIDI specification:
edit: The input uses 5V.

I have a PC123 optocoupler by Sharp lying around, so I'd like to use it in the circuit. The problem is, that I'm not quite sure if this optocoupler can be used for this circuit. I think that the maximum ratings are acceptable but maybe I'm missing some details.

these ratings can be found in the specification here.


texts:
There are 2 possible ways to calculated the signal sum: either by amplitude or by power. According to the paper http://authors.library.caltech.edu/824/1/HAJprocieee05.pdf, we should add the amplitudes together: if we have 2 synchronized signals with amplitude 1, their sum has an amplitude of 2 and a power of 4 ("if each element radiates P watts, the total power that will be seen at the receiver in the esired direction is m^2P watts). But I think that is against the low of energy conservation. Anyone has a good explanation?

Thanks in advance!

Bile

p.s. I understand in the paper above, what we calculate is not the total transmitted power but the power in a certain direction. So can this method be applied only in case of beamforming or can it be used also in a circuit?


texts:
Hi I am new to electronics and I want to know is there any difference, using different ratings of an electrolytic capacitor, can I use any 50/100/200/400Volts etc and 1000/2000/4700/10,000uF etc to make a Center tapped rectifier for a 24_0_24 VDC toroidal transformer. Last week I made one but the rectifier gets hot within second, I used this diagram

[![enter image description here][1]][1]

The parts I used to make the rectifier are "four IN5408-diodes and two electrolytic capacitor 25volts 4700uf, I have tested the rectifier on a 12_0_12 VDC laminated transformer but the rectifier gets hot, so any help will be greatly appreciated. Thank you.

This is the transformer.
https://i.imgsafe.org/6c5e203e9a.jpg

will a 200/250 VDC cap work, if not will this cap work.
https://www.eightaudio.in/products/elna-4700uf-63v-aluminium-electrolytic-capacitor?variant=17590826756

Thank you.


texts: Can not keep pin LOW during FPGA configuration

texts:
I would like to have a control signal that stays low all the time and goes hi only when I tell it to. Initializing the pin in the entity does not seem to set the value to zero (xc6slx25-3ftg256):

Entity myEntity IS
PORT(
     -- clock and other IOs
     mySignal : OUT STD_LOGIC := '0'
);
END myEntity;

ARCHITECTURE structural OF myModule IS
BEGIN
-- ...
-- at some point I set mySignal to 'HI'
mySignal <= '1';
-- ...
END structural;

.UCF content

-- other nets
NET "mySignal" LOC = "H15";

I realize that during the configuration, the FPGA structure is not set, so it may have some random values on its outputs. However, after pulling down the pin with 10k, it still stays 'HI' during reset and configuration. How to make it stay low?


texts:
My stage 1 amplifier alone is perfectly bias and the q point is in the middle of the load line. The collector voltage is around at the middle of the supply voltage (to be precise, around 24 volts and supply voltage is at 48 volts). Now when we add another exact copy of stage 1 and attached it to stage 1, the q point of the stage 2 suddenly misaligned from the middle point of the load line (it went from 24 volts to 11 volts). Why is that so? It should be that the original bias condition and q point must be inherited since both stages are exact copies of each other (like identical twins)

which results to severe distortion


texts:
A function generator has a 50 ohm and 600 ohm main outputs:
http://www.ece.mtu.edu/labs/EElabs/EE2303/model_25.pdf What does it stand for? What is the difference? Is that about the load resistance?


texts: Problem with using comparator to amplify signal

texts:
I want to use LM293(comparator) to amplify signal. The input signal from 0 to 2.5V, and make the output signal double(from 0 to 5V).

Then I use the LM293, and I do the simulation  first, it works fine. But when I test the circuit in reality, it doesn't works, which means when the input is 0 or something below about 1.6V, the output is always about 3.2V. When the input signal > 1.6V, the Vout= 2*Vin, which is I want.

Here is my circuit below, if you have any suggestion, please let me know. Thanks!
I have draw the signal almost as I get.
(I am sorry that C1 is connected between output of Lm293 and Gnd, I will update this Asap)


texts:
I know what it is in general terms of course. But I mean specifically what does the M7 mean. I certainly can't just go to digikey and order an M7 diode because such a part does not exist. I'm making a rugged arduino clone (using kicad) for my own use and intend to put a fuse or possibly resettable fuse in front of that diode so as it doesn't burn out etc... so I have thought of that.

It appears to indicate that the diode must have a 1000v reverse voltage.

See here for the circuit (see the external power supply circuit):
http://arduino.cc/en/uploads/Main/arduino-leonardo-schematic_3b.pdf


texts: Why are so many old lamps switching the neutral wire?

texts:
So I am deconstructing old houses and I noticed that there are many Lamps that are switching the Neutral Wire instead of the Phase.
Why was this done ( Especially as it has no advantages afaik)


texts: op amp non-inverting input isn't working?

texts:
simulate this circuit – Schematic created using CircuitLab

Why in above schematic if i left the non-inverting input floating or connected to 1V or 3.3V the LED stays ON and current doesn't change with increasing/decreasing the Vref voltage?

Also LED current increases with increasing voltage and it's not constant...

Table 1 (when 3mm LED and transistor is connected):

Vref | Op-amp out | Emitter |  VBE
-----+------------+---------+--------
0.0 V|    2.96    |  2.75   |  0.81
0.5 V|    1.16    |  4.48   |  0.66
1.0 V|    1.68    |  3.96   |  0.68
2.0 V|    2.77    |  2.93   |  0.75
3.0 V|    2.98    |  2.75   |  0.80


texts:
I'm testing out the BQ25887 2 cell balance charging IC, and I'm trying to read the data from the I2C interface. But I'm not getting any results. I am unable to see any values from the serial monitor on the Arduino IDE. To read the data, in my test setup, I have my Arduino Nano attached to my computer with the SDA and SDL lines plugged into Arduino header. The IC and 5V pull-up voltage is being powered by an external voltage source (in this case a battery pack,) which is outputting 5V.

I tried using the 5V from the Arduino Nano to pull-up the I2C lines, but the LEDs on my PCB were oscillating, so I decided not to. Any recommendations would be appreciated.

Schematic

Test Setup

#include <Wire.h>

void setup() {
  Serial.begin(9600);  // start serial for output

  Wire.begin();        // join i2c bus (address optional for master)
}

void loop() {
  Wire.beginTransmission(0x6B);
  Wire.write(0x0D);
  Wire.endTransmission();
  Wire.requestFrom(0x6B, 1);    // request 6 bytes from slave device #8

  while (Wire.available()) { // slave may send less than requested
    int c = Wire.read(); // receive a byte as character
    Serial.println(c);         // print the character
  }

  delay(500);
  Wire.endTransmission();
}


texts: Can you calculate how long it would take to drain a battery given the watts?

texts:
I'm looking at an LED light and it says it takes 2.2 watts with a 3.7V / 900 mAh battery.  How do I calculate how long the LED light will last if it's on continuously?

The item in question is this


texts: Arduino connect to internet without ethernet shild

texts:
I'm beginner on arduino, and I'd like know if there are some way to connect to internet without ethernet shield just using an arduino plugged on my computer using a usb cable?

Thnaks.


texts: Help with capacitor circuit calculations


texts: I am working on a project which include displaying RGB colors. I would like to know what is the difference between RGB and SRGB. Is it possible to have srgb colors in led. As SRGB has been used for printers, monitors and internet colors.


texts: Resources to learn about the AVR/RISC architecture

texts: I think I have used enough of the AVR series by atmel to say that I understand how to use it. I know somethings about how it actually works, but I would like to know more. Are there any good resources which describe the architecture of Atmega or RISC architecture in general? I know the datasheet has all this (and I really looooovvee the datasheet, its kinda my bible) but I need something little more simple than that. Any help?


texts: Microcontrollers: Can I perform floating point operations in a Picoblaze controller?

texts: I wonder if I could perform floating point operations in a Picoblaze controller? Thank you to all posible answers with direct references to documentation or articles.


texts: I don't understand how I can find RS, RD and RG so that ID=.1mA. Help.


texts:
I am powering a bunch of LEDs with a 60A/5V power supply.  For extra protection, I wired a 50A circuit breaker between the supply and the LED array:

http://www.digikey.com/product-search/en?mpart=W23-X1A1G-50&vendor=41

The LEDs started flashing and acting weird so I used a clamp meter to determine the amount of current I was pulling and saw it was a little over 60A.  I have an extra breaker and the same thing happened when I switched it out.  Am I using the wrong type of breaker?


texts:
I have an application that requires switching on a load very fast (1ns or so).
There are N-channel / low side GaN MOSFETS. I would really like to switch a load on the high side, which causes problems when the FET output/"source" rises above the gate driver voltage.
I would really like to a find an ultra high speed switching SCR / Thyristor for this, but have been unable to find them.
Can anyone suggest a family of components I may want to look at?


texts:
If this is a repeated question, please let me know.  I'm a hobbyist electronics person, and ran across symbols on a diagram I didn't recognize.  I've attached the image below:

What I'm trying to figure out is what the different rings around the wires mean.  For example, Earphone Pilot has a connection that shows a ring around one of the wires, and then that hits a T connection where all of them have rings around the wires, too.  I've been trying to look it up, but I'm having a really hard time finding info.  The full diagram is part of the wiring diagram for a Becker Avionics AR620X transceiver, and the diagram is on page 77 of the PDF here.


texts:
Folks,

Let's say I have a USB 3.0 card with four USB 3.0 ports on it. I just connected the card to my mother board.

When we say 640MB/s of bandwidth for USB 3.0, is that bandwidth per port (or 640*4 = 2560MB/s total), or is that the total bandwidth (or 640/4 = 160MB/s per port)?


texts: What is the term for a DC-AC Isolated Power supply?

texts:
I'm reading DC coupling in tube based guitar amplifiers and how avoiding capacitors in the signal chain reduces signal loss, phase distortion, and noise introduction from the resistors that also have to be brought in.

The topic is fascinating, but there's an upper limitation on how many times one can DC Couple gain stages, mainly to due to the maximum cathode-heater voltage. Most tubes are 100v, others are 180v.

The heaters on tubes don't care if they're ran by DC or AC (AC is probably better if the filaments are in series).

If my initial power source is 24vdc, is there a prebuilt module that can kick out 12.6vac/vdc, or 6.3vac/vdc at high amperage? Everything I'm finding is like $100+. It seems like if you have a sine wave generator drive a transformer, one could make a simple DC-AC isolated converter. It seems like an idea so simple, but I cannot find anything like this, so I'm wondering if there's a specific term I need to be searching for, or if there's a design I could use to build my own.

Thanks!


texts: Track clearance with flex region cutout in Altium Designer

texts:
In Altium Designer, I created a simple rigid-flex board with the 4 layers in the rigid part (top, in1, in2, bottom) and 2 layers in the flexible part (in1, in2).

I set 5mm clearance on a top layer track by means of a simple rule. On the rigid board, the track doesn't have 5mm clearance with respect to the board outline (which is the correct behaviour), but it has 5mm clearance with respect to the split line that divides the rigid part from the flex part.

Said in other words: I can route the track up to the very board border, except when it is a rigid-flex border.

How do I remove the 5mm clearance with respect to the border between the rigid and the flex part?

The error I get is Celarance contraint between track on TopLayer and PolyRegion on MultiLater:

The net with the problem has class1 class; I set a simple 5mm clearance rule on this class. All other rules are set to Altium defaults.

The only way I found to remove the clearance violation is to set the clearance matrix as in the picture below, but this is not accepable for a standard circuit:

EDIT: I updated the image to be more clear.

EDIT 2: I added more screenshots.


texts:
I'd like to formally understand this simple biasing circuit:

Let V+ be the supply voltage, Vi be the input voltage at the seemingly unconnected terminal of the capacitor, and let Vo be the output voltage at the junction between the resistors and capacitor. Let S be the impedance unit (i*omega)

using VI relations and Kirchoffs laws:
(V+ - Vo) / R1 - Vo/R2 + (Vi-Vo) * C*S = 0

which after rearranging gives:

Vo = (V+/R1 + ViCS) / (1/R1 + 1/R2 + C*S)

decomposing the numerator it becomes clear that the biasing term is:

= (V+/R1) / (1/R1 + 1/R2 + C*S) = V+ / (1+R1/R2 + R1CS)

Does the amount of bias really depend on the driving frequency? At DC, S=0 and everything reduces to a voltage divider regardless of the voltage at Vi.

(Sorry for the eye-sore math. Is it possible to do math input on this website like it is on math.stackexchange ?)


texts: I am interested in using an STM32 to flash an sof or pof file onto a Cyclone IV FPGA. The sof/pof will be stored in SPI flash memory, and the plan is to use the STM32 as a programmer. I haven't been able to track down any projects that do this but am super keep to learn if and how it could be possible.


texts: LM317 voltage regulator with high current boost by 3 npn transistors

texts:
I am building a rectifier (~230V+-10%/50Hz) with voltage regulator from scratch. My output needs to be 3.3V with a maximum current(before short-circuit protection trigger) of 16A.

I have chosen three npn transistors in parallel to boost my current (2N3055) up to 16 amps and calculated respective resistors, powers, temperatures in order to work properly with real elements. However I experience problems in my simulations and the output is nowhere near what I expect. Vin is what I will have after my transformer, rectifier and LC filter- around 7V with 80mV pulses.
Ic across each transistors should be~5.33A.

However during a simulation with a load of 0.22 Ohms, a current of 15A is expected but this is what I get.

Vout is around 2.1V and Iout is 9.45A. Why so?

I also want to add a short-circuit protection that is triggered by Iout greater than 16A.

I guess it should be with a pnp transistor and a resistor but I am not sure how to calculate and where to connect it.

Here is a 2N3055 datasheet 2N3055 and LM317 datasheet LM317


texts:
I know AD620 is an old part but it is available at my place. I intend to develop a Load Cell amplifier. Load cell is 2mV/V. I am planing to use AD620 for it. Following are my calculations:

Excitation Voltage for Load Cell = 5V
Full Scale for load of 140 kg = 2mV X 5V = 10mV
Gain = Vout/Vin = 5000mV/10mv = 500
From formula of Rg we calculate it to be 98.99 Ohm

I have worked on Following schematic:

What is the problem?

If I leave the pin 5 open then Min Voltage is 1.9 and max is 4.2 volts. If pin5 is grounded then min voltage is 0.6 and max is 1.9 (strange)
the max voltage (4V) is reached at 6 mv Input. even gain calculation is done. But we have added 100 Ohm resistance instead of 98.99 Ohm.
Is there any difference between AD620AN, AD620AR and AD620ANZ ?
In some circuits i see that at sense + and sense - sometimes before feeding these to operational amplifiers some resistance is added. what is the purpose of adding these keeping in mind the voltage is already in mV
Can you suggest load cell amplifier other than INA125 because that is not available


texts:
I'm 'testing the water' if you will on driving a Panasonic TUV PL-S 5W UV lamp with a low-voltage (12 ~ 24 V) DC supply.  The lamp is rated at 34 V, 0.18 A.

Since I have a DC source, magnetic ballasts are out.  I have read some app notes from ST and Infineon on electronic ballast design, yet these sources are concerned with mains-connected fluorescent lamps (i.e. the artificial sun above your cubicle).

The closest products I could find are the UC3872 and UCC2973 which seem geared towards automotive and laptop computer applications.

Since the lamp is only rated for 34 V I would use a different transformer (1:3 for 12 V, etc.).  Other than that I feel a bit clueless.  Am I heading in the right direction, or are there simpler slash better paths to take?

EDIT: a dimmable feature is not needed.


texts: Confusion regarding Common-Emitter configuration of a BJT

texts:
This is a picture of a Common-Emitter Configuration of an n-p-n BJT, taken from a book :-

For the BJT to be in active mode, the Base-Emitter junction should be forward biased, and the Collector-Base junction should be reverse biased.

Here, I am having difficulty understanding how the Base is at a higher potential than the Emitter, and how the Collector is at a higher potential than the base.


texts: Are there general guidelines for LiPo discharge current?

texts:
I'm doing a hobby project where I'm designing a smart RC car around the size of a mini sim card. The BOM has been narrowed down, and I reckon it's doable with a 4-layer board.

Image source: https://www.gsmarena.com/glossary.php3?term=sim
I'm now doing research on possible batteries to use. I'm eyeing the Panasonic CG-320 (15 mAh rated) or this 70mAh LiPo battery. Both are well within my size targets, but I'm unable to find any datasheets that specify a maximum discharge current.
For reference, my power budget is less than 5mA when sitting idly, less than 100mA when running around, and 300mA worst case (e.g. in case of motor stall).
Are there any rules of thumb regarding discharge? Based on what I've read, a maximum current of 0.75C for charging is ideal, but I'm unable to find any figures for the other way around.


texts: Caseless PC - should I be concerned about incoming EMI

texts:
This is a follow-up to this question. I have built a custom PC case that is essentially cardboard. Are the components likely immune to ambient EMI or do they build them under the assumption that a quality case will attenuate such signals.

I am new to EE SE (though I foresee many future interactions as I plan to enter the field).


texts: Does a photo-coupled SSR need a series resistor for the internal LED?

texts:
I am trying to control an LCA710 SSR with an Arduino digital output. The data sheet says the control inputs are "CMOS and TTL compatible". It also has a schematic of the internals of the chip, showing an internal LED and photo-sensitive something-or-other (switch, basically).

Do I need to put a resistor in series between the digital out pin of my Arduino and the control pin of this IC?


texts: can I rewind a 220 volts coil into 24 volts?

texts: My machine's magnetic contactor needs replacement but it's quite difficult to buy a 24 volt coil magnetic contactor. Can I purchase a 220volt coil magnetic contactor and rewind the 220v coil into 24 volts? Can it be done with the existing wires?


texts: I've been doing this question for quite a long time, can someone explain to me why b would be different from part d, and what im doing wrong from part b and c?


texts:
I want to do a simulation with two type amplifiers (PA107DP) in cascade to expand the bandwidth.
How can I do ? just I connect the output of first to the input of second (out-one I connect it to -IN of second amp) or there are modifications necessary to make at the input of second amp (like resistance ect )


texts: Efficient temperature control for a growbox

texts:
I am making a growbox controller. It has (among other things) a heater and a temperature sensor. Heater has no temperature controls, it can be turned on/off.
The objective is to maintain temperature between 23 and 27 Celsius. A simple 'if else' might do, but I am not fond of constantly switching heater. So I'm wondering, is there any algorithmic approach to do this with maximum efficiency? Don't want to reinvent another wheel, so decided to ask here first


texts: What is a good way to solder small transistor to wire?

texts:
I have a really small transistor with very little space between its pins. I want to solder resistor to base and wires to collector&emitter. So I am worried about transistor pins come in contact by accident. The wire is about three times as thick as transistor pin, which doesn't help either.

Edit:

Here is small schematic of the things that I need to solder. Wires that connect to relay will be soldered to connector instead of wiring directly to relay.


texts:
I'm trying to write a bootloader for an STM32F4xx (currently for the STM32F429 discovery board). My application should start at address 0x08020000 while the bootloader starts at 0x08000000 (start of flash).

I created the application with CubeMX, changed the FLASH ORIGIN in the linker file to 0x08020000 and the VECT_TAB_OFFSET to 0x20000 in the system_stm32f4xx.c file (this changes the VTOR to 0x08020000). My application just blinks a LED and works as expected at this new address when started from the IDE.

while(true) {
    HAL_Delay(200);
    HAL_GPIO_TogglePin(GPIOG, GPIO_PIN_13);
}

Instead of writing the bootloader immediately (actually I did that and it didn't work) I used the ST-Link utility and did a few things: I verified that everything, beside the application, is erased (0xff). I reset the CPU and manually set the PC to 0x08021924 (this is the Reset_Handler according to the map file from the application). When I slowly step/run through the application, I can see the following: The SP is corretly written (as this is part of startup assembler code from CubeMX). The VTOR is corretly set to 0x08020000 (I read out the SCB manually at address 0xE000ED00, the 3rd value is the VTOR) and after some time the application loops inside the HAL_GetTick & HAL_Delay function (I read out the PC an compared it to the map file). I even see that the application reads the uwTick (at address 0x20000020 in my case), which is never increased, and therefore the HAL_Delay loops forever. so my conclusion is:

The interrupts seem to not work correctly

in this case the SysTick ... Despite a correct VTOR and the application seems to run fine. When I replace HAL_Delay with a Busy_Delay (which just consists of a loop of millions of NOP), the LED blinks. When I start it manually through the mentioned method (or a manually written bootloader with jumps to the correct address) then the application runs normally (because quite likely nothing depends on interrupts in this short example).

What I'm missing to write a working bootloader (with working interrupts)?


texts: Verifying electric brake current with opto-isolated feedback

texts:
I would like to find a way to sense (or detect) current through an opto-coupler.
This opto is used to power an electromagnetic brake, but depending on the type of brake the current through it can range from 400mA to 1500mA.I want an opto-isolated digital signal to verify current is within a specified range in an electromagnetic brake circuit. The electromagnetic brake current can range from 400 mA to 1500 mA.
How do I detect this current safely and provide an isolated signal to the microcontroller? It could also be a current present/not present detection system.
The reason behind this is somehow detecting that the brake is powered (current is flowing) or not.
Thanks!


texts: Open Collector Comparator for Voltage Glitch Detection

texts:
I recently ran a round of PCBs which included an experimental circuit to detect short glitches in my input voltages. I attached the schematic for reference:

The intent is that C29, in parallel with R27, should hold V- at ~3.1 V even if 3V3 has a short glitch. So a quick glitch on 3V3 should be detected by the comparator and trigger an output which I can read with additional circuitry.

After testing a few PCBs and seeing initial input current spikes and some minor smoking from the board, I've narrowed it down to this chip as a possible culprit. I started taking voltage measurements and saw big disparities in V-: 0.96, 2.82, 1.58, 1.32, 3.96?? Seems like this chip is just completely fried, but I'm not sure why this would have happened.

Link to Datasheet

Does anything stick out as an obvious mistake? Some thoughts/notes:

I noticed the same input current jump when I applied only 3V3 to the board, without any power on 5V.
Without desoldering the resistors from the board, I can't accurately measure the individual resistor values because of the rest of the board.

Edit 2016-06-03:

Think I got to the bottom of it. I think the chips were actually still operational, and the smoking/initial current surge was coming from somewhere else (to be determined where). The actual problem had to do with my biasing circuitry for V-, and the comparators actual bias voltages.

The datasheet gives the bias current anywhere from 25 - 400 nA.

My "ideal" biasing current would be ~ 310 nA (3.3 V / 1.0634 MΩ).

Considering the wide range of possible comparator bias currents, this could definitely explain the difference in V- readings I was seeing. For my next round of PCBs, I'll spec the ideal biasing current to be in the 10-100 uA range so the comparator bias current becomes insignificant.

Does this make sense?


texts:
I am trying to simulate a load in SPICE(PSICE). This load is modeled by a resistance that can go from a high value(thereby sinking low current) to a very low resistance that can draw a large amount.
How can I model such a variable resistor (w.r.t time) in SPICE ?


texts: Say I used a 12v car inverter powered by a 12v brick connected to ac mains (no ground pin) to isolate a scope and bench dmm, the inverter has no earth ground. Is the equipment isolated? Is lack of earth ground an issue?


texts: Optocoupler driving 300mA continously (or use darlington topology?)

texts:
Looking at driving two LED strings with a DC/DC constant current LED driver module. The constant current side can't be referenced to ground of the control circuit, so I need to have an isolated switching to choose which of the two strings I would like to drive.

I'm "only" driving 300mA current, so I was thinking of using two optocouplers to select the string I want. I am having trouble finding a optocoupler that can take 300mA continuous current.  How can I change my circuit so the optocouplers can drive 300mA? Can I add another transistor?

Schematic of what I had in mind:

(note - the driver I'm using cannot handle no-load situations, so I can't just use a SPDT relay, as I will have no-load conditions during switching causing voltage spikes and god knows what other issues)


texts:
I'm new to electronics and my Bluetooth speaker broke and want to fix it. This is the chip I think I need to replace.

Can anyone help me find this chip's datasheet? I just need to know what each pin does.
I have tried to find it but I couldn't find any info on it. Maybe because it's  from a dirt cheap speaker.


texts: Verilog Error: System task finish is always executed

texts:
I'm using a Mimas V2 with a Spartan 6 CSG324 LX9. Trying to teach myself to use Verilog and I've been using this tutorial. I've had no issues running VHDL modules and running just this code Verilog code (which appears towards of the problematic chunk further down) seems to work:

module myModule(A, B);
    input wire A;
    output wire B;
    assign B = !A;
endmodule

Doesn't really do much though, as the inputs and outputs aren't set up to do anything though.

It seems to be having a problem with line 15 here:

module myModule_tb();
    wire out;
    reg clock;

    always begin
        #1 clock =!clock;
    end

    initial begin
        //Initialize clock
        clock = 0;

        //End simulation
        #10
        $finish;  //<-------this line here
    end

    myModule notGate(clock, out);
endmodule

module myModule(A, B);
    input wire A;
    output wire B;
    assign B = !A;
endmodule

The error message I get when I try to implement is

  HDLCompiler:1689 - "C:\Xilinx\Projects\Test2\myModule_sim.v" Line 15: System task finish is always executed.

Now as best as I could tell, I followed all the steps correctly. I even went so far as to download the example files provided (the Mimas version) at the bottom of that tutorial, and it does the same thing. I understand roughly what the $finish task does, but I'm not sure why it's causing a problem here. Seems like it's fussing at me for expecting finish to do what it's supposed to do here.

I've tried a semi colon after the #10 on the preceeding line, putting them on the same line, commenting out #10, commenting out both #10 and $finish and I always get the same or an error related to not having $finish

Help! I'm not sure why ISE is rejecting that line!


texts:
My biggest problem is when I discharge a supercapacitor, let's say 100F 2.7V, I use a boost converter, but all boost converters have a minimum input voltage of about 0.9V. But the capacitor still has a lot of energy, about 40%.

It is frustrating because I'm not able to use this energy so my real useful capacity of capacitor is only 60%.

Does anyone have some idea how to fully discharge a supercapacitor?


texts: How could I create two separate ground areas with Proteus?

texts: I need to design a PCB layout to a system using an isolated communication with optocouplers, what means that I need separated ground areas, each one on one side of the communication that I want to isolate. So, is that possible to do it? How could I do it in a simple way?


texts: Is it possible to make a weak analog low-pass filter with less than 20 dB/decade roll-off?

texts:
Part of Respawned Fluff's answer to this recent question on headphones got me thinking about low-pass filters:

  It seems they actually invert the transfer function of the dummy head/ears via software because they say right before that that "Theoretically, this graph should be a flat line at 0dB."... but I'm not entirely sure what they do... because after that they say "A “natural sounding” headphone should be slightly higher in the bass (about 3 or 4 dB) between 40Hz and 500Hz." and "Headphones also need to be rolled-off in the highs to compensate for the drivers being so close to the ear; a gently sloping flat line from 1kHz to about 8-10dB down at 20kHz is about right." Which doesn't quite compile for me in relation to their previous statement about inverting/removing the HRTF.

This is talking about headphones, not circuits, but it made me wonder if it's possible to create such a transfer function with an analog circuit. First-order filters have a slope of -20 dB/decade. Is there anything weaker? I suppose the transfer function would be something like this:

$$H(s) = \frac 1 {1 + \sqrt{s / \omega_c}}$$


texts:
I want to check an IGBT FGA25N120ANTD whether it is broken or not. I have a good multimeter.

I followed some online videos I cannot figure out the right way.
Could you please help?


texts:
This LTspice model

produces this netlist:
V2 N001 0 AC 1
R6 out1 0 10k
R32 N003 out1 50k
R31 N002 out1 50k
R1 N003 N001 R1
R2 N002 0 R2
C1 N003 0 C1
C2 N002 N001 C2
.ac oct 100 60 6000
.param R1=39k R2=47k C1=22n C2=10n
.backanno
.end

But produces these errors:
Error on line 6 : r1 n003 n001 r1
     Unable to find definition of model "r1"
Error on line 7 : r2 n002 0 r2
     Unable to find definition of model "r2"
Error on line 8 : c1 n003 0 c1
     Unable to find definition of model "c1"
Error on line 9 : c2 n002 n001 c2
     Unable to find definition of model "c2"
Fatal Error: Missing capacitance value for "C2"

Does anyone know:

Why can it not find the capacitance value for "C2"?
And what so the errors Unable to find definition of model "r1" mean.

Thanks


texts: How to connect 3-wire spi with an arduino to the Maxim DS1801 digital resistor?

texts:
I just picked up an Arduino Due with the SAM3x 3.3v chip. I am attempting to communicate with a Digital potentiometer to control an amplifier's volume level but I have no clue how to go about hooking up the 3 wire SPI connection. If I am correct doesn't the Arduino use a 4 wire set up??

I have seen that it is possible from links like this but to be honest with you I don't understand it. Can someone break it down for me and tell me exactly where to plug in the pins for D, RESET(bar), and CLK on the DS1801 into the Arduino Due??


texts: Does a Center-Tapped RF Balun Perform Better than Untapped Baluns?

texts:
To my knowledge, a conventional transformer is a balun - you simply connect a single-ended signal at the primary side, you get the balanced signal at the secondary side - magnetic coupling doesn't care where the ground is. It also automatically offers DC isolation.

But I see broadband RF mixers and amplifiers have a center-tap at the balanced side as well, for example Mini-Circuit offers a lot of baluns with center-tap. I often see the tap is grounded (or sometimes AC-coupled to ground), and seems to serve no purpose (*).

I found an application note from Mini-Circuit, AN-20-002: Application Note on Transformers, it says,

  For Balun applications, choose a balun with center tap on balanced side as it provides excellent amplitude and phase balance.

In other words, a balun with an unconnected center-tap (or without one), has worse amplitude and phase balance than a center-tapped balun? Why? So a connection to ground can force the center to be at common ground potential, thus making the balanced side to have better balance?

(*) I know in double balanced diode mixers, a center-tap is needed to extract IF signal. I also read that a grounded center-tap can remove excessive common-mode voltage at the balanced side, that may degrade the performance of a differential amplifier. But I'm asking about the balun device, not its applications.


texts:
What is a good way to log(sample) current draw over a period of time, from e.g a RaspberryPi with some equipment connected to it (100 mA +).

A datalogger like the EasyLog | EL-USB-4 have a measurement range of 4-20mA d.c. Is there a smart way to use it to log higher currents?


texts: Can I have 0.03V in the input of an OpAmp? If can, what type of OpAmp can I use?

texts:
I want use OpAmp as amplifier to increase my voltage. I have as input voltage 0,03VDC.

I want increase it to become 5VDC in output.

If I cannot use the OpAmp what type of circuit I should use to increase my voltage?

I tried to use voltage doubler, but it doesn't is not worked.


texts:
I need to connect two boards using UART of AVR. I wanted to know how much can be the maximum length of the cable between two baords if VCC is 3.3V. I dont want to use rs232 here.

This question didnt help


texts:
Beginner here, please bear with me. I'm following instructions to modify a popcorn popper for coffee roasting: http://popperyii.blogspot.com/

It looks like it requires a 25.2 VCT 2A transformer (schematic). However, Radio Shack no longer sells these. Are there any alternatives? Would a 12v 2A "cellphone charger" transformer work in place of that?


texts: Measure 220V alternating current with a multimeter in DC mode

texts:
What happens if we measure  220V AC from wall socket with a multimeter in DC mode (instead of AC)?

If I remember correctly, it should show the average value of this sinusoidal 220V, i.e. 0V.

Is this true with nearly all multimeters?


texts: Over-current-protecting a single-ended solid-state switch

texts:
A previous circuit used a ULN2003 Darlington pair as a single-ended (N-side) solid-state switch with a maximum current capacity of about 500mA.

http://www.st.com/resource/en/datasheet/uln2001.pdf

However, it has no over-current protection, so I'm researching either a replacement or a surrounding circuit to do so. Protection would ideally apply to the channels individually, but a simple solution for the entire circuit would also do. I've found these options:

Add a PPTC self-resetting fuse on the output of each of the channels. Cheap, simple, but I'm not thrilled with the prospect of waiting >2s for it to trip. The switch can easily be destroyed in that time - especially since the ULN200x datasheet does not specify a max time for the peak current, only a duty cycle, and the duty cycle in this application will be 100%.
Add a 1R res to the output channels, and then either an ADC or a comparator with further shut-off circuitry. More complex and expensive, but faster and more precise.
Rely on the Vcesat parameter of the ULN2003. If Vce exceeds about 1.4 V, infer that the current exceeds 500mA and then add the same circuitry as #2.
Replace with a switch that has current protection built-in. Haven't been able to find something nearly as affordable as the ULN200x.

I'm leaning toward #3. Something like:

simulate this circuit – Schematic created using CircuitLab

Questions:

Is the above circuit safe, stable, and an appropriate way to implement current protection?
Among my other listed alternatives (or not), is there a better way? I usually lean toward simplicity.


texts: Why does my LM311 comparator's output seem to be inverted?

texts: From what I understand, the potential difference between its output pin (COL OUT) and GND is equal to the voltage of source when the potential of IN+ (pin 2) is greater than IN- (pin3). The opposite seems to be happening with my circuit.


texts: LTspice (XVII) Use user defined parameter in component instance name and net name

texts:
I'm trying to simulate a lumped transmission line using the bussed wire and array component notation:

For a hardcoded array length everything works fine but I want to control the number of lumped segments using a parameter which unfortunately doesn't work, neither for component names nor for net names. In net names without colon notation, LTspice doesn't even allow curly braces.
When hardcoding the length into the component name, the message window (appears when changing the name) says:

Is there a workaround to this problem? Thanks in advance!


texts: What is the charge of linear and non-linear capacitors with same current

texts:
The following simple circuit has \$V1\$ as a \$DC \$ voltage supply and \$C1\$ is a linear capacitor and \$C2\$ is non-lineaer capacitor.

It is known that:

\$q_1 = C_1\cdot V_{c1} \$ , hence a linear capacitor

\$q_2 = \alpha\cdot \sqrt{V_{c2}} \$ , non-linear capacitor

Since both capacitors are in series, thus the same current flows through them, is it correct to clime they has the same amount of charge (i.e. \$q_1 = q_2\$) after some \$t \to \infty\$?

simulate this circuit – Schematic created using CircuitLab


texts: can i use dual supply op amp in single supply mode?

texts:
Can i use dual supply op amp in single supply mode?
Is it okay to convert a bipolar voltage to uni polar and then feed it to a single supply op amp(amplifier)?


texts: LPc11u68 Recognized as an USB mass storage device even when programmed in HID class

texts:
When I connected a newbie LPC11u68 to USB port,it recognized in windows as an USB mass storage device.When I  programmed LPCOPEN HID example by Flash magic to it,after resetting the board,my PC can't recognized it.Only when I pulled down PIO0_1(ISP selection pin)it still recognized as a Mass storage device.???
LPC11u68's Datasheet.
I'm using a simple header board with USB port(As i said PC successfully recognized 11u68 as mass storage devices ,then I think there are no hardware fault). Also I'm using LPCXPRESSO IDE v8.0.0,I tried all of the USBD examples in the LPCXPRESSO boards LPCOPEN examples, and they programmed successfully to the chip,also I config a LED to blink. In all of them LED blinked which means MCU is running , but when I connect board to the USB port of my PC,I cant see it in the USB or HID section of my PC's device manager. I don't checked SWD, is LPC11u68 support it? WBR.
EDIT:know when I compiled LPC11u68 lpcopen HID examples for the manley 11u68 board ,devices appear in the devices manager but after a second it disappear while I don't disconnect it.


texts:
I am having difficulty analyzing the following circuit:

Schematic from: eleccircuit.com - 5 Channels 2 Octave Graphic Equaliser by 4558 (copy from Wayback Machine)
I can see what the circuit does after running an AC sweep simulation. However, I would like to work out how the capacitor values were chosen.
Specifically, I get stuck with the analysis of the individual stages due to the 10k resistor across the input pins. The normal rules of ideal op-amp circuit analysis seem to be violated here. Vn does not equal Vp or there is current flowing into the input terminals of the op-amp. What's going on here, and how can I proceed?


texts: Why and How does Power Plant generate Watts?

texts:
I know my question is stupid, it is stupid because I am not understanding it correctly.

I thought two of following is required to calculate watts. Voltage, Current or Resistance/(Impedance in AC) is required.

The only way to get current is when we have a load. How does power plant generate in unit of watts when where is no load.


texts:
I'm trying to build simple fsk transmitter and receiver, the transmitter is just an FPGA with a wire, the logic is quite simple, I mix (with a XOR) the transmission frequency with a lower frequency, thats create some distortions which can be picked up with a simple FM receiver.

The receiver is based on the TDA7000 (yes I know that's obsolete) with a fixed tuning frequency. Here is the received spectrum for two different case, the peak at 1.1 KHz should indicate logic LOW and the peak at 1.6 KHz should indicate HIGH, the peaks are about 300mV, but I guess it may vary

Note that there are distrotions at 2.1 Khz and and 3 Khz.

How can I feed the signal to an FPGA, which should count and identify the frequency, with a minimal number of parts, I guess LM741 is too much for that kind of task.
How do I deal with the distortions?
Any other suggestions?


texts: Best way to transform multiple digital signals from 12V to 3.3V

texts:
I am looking for the best way to transform multiple (more than 10) 12V digital signals down to 3.3V

I know some ways to do it, such as voltage dividers, make use of BJT or MOSFETs, or even Operational Amplifiers. However, such methods would require more than one component per signal, making the PCB more complex

Is there any simpler way to achieve this? Is there any commercial IC which manages the transform?

EDIT: The goal of this step down is simply to read such signals from a microcontroller (which LOW level is -0.3÷0.8V and HIGH level is 2.0÷3.45V). Hence, very small amount of current


texts: Adding breakouts for external components in Eagle PCB

texts:
I have an external actuator which is connected to a component on the PCB board. This connection will be through wiring.

However, I cant seem to find the breakout component which will allow me to solder wires onto the PCB. Does anyone know how to do this on eagle PCB?


texts: Does the ratio of the mechanical degrees of a generator to 360 degrees have a specific term and symbol?

texts:
When it comes to DC generators, the ratio of the mechanical degrees of a generator between two brushes to the total mechanical degrees which is always 360 is used in different quantities such as demagnetizing turns per pole. This ratio can also be expressed through other means, such as stating the number of commutator segments or through the length of an arc and the circumference. I just want to know if this quantity has a formal symbol and name.

For reference, this was taken from Page 941 of Electrical Technology by Theraja. It shows one usage of the ratio I was mentioning.


texts:
I have a custom made solenoid that is required to work at 60V to actuate with enough force.

I have tried two circuits shown in the figure below but both don't work. In the first circuit, the voltage across the coils is just 3V whereas in the second one, the voltage across the coil is zero although the opto isolator does work.

I can't figure out what is going wrong. I used IRFZ44N for mosfets at 30V source-drain voltage for testing.


texts:
I want to build a simple device to check if the light is on or off. I found some schematics but I need to be sure that it is safe.

Source : How to detect 220 VAC voltage using an opto-isolator

My problem is that I do not understand this very well. I found that PS2501 have a chance of working up to 80V so how can I safely connect it to 220 VAC? Which resistors make a limit for the voltage here? Why do we need to add a capacitor and diode (D1,C1)?

I'm a beginner in this field so please be patient.


texts: Failure accessing ST LIS3DSH accelerometer CTRL_REG_4

texts:
I'm writing to ask if someone has ever encountered a quite weird behaviour of LIS3DSH.

to properly use such sensor, a number of registers must be configured via the spi bus. I implemented a routine to do so, which writes the registers in sequence and reads them back to check the operation result. The function gets stuck on the very first register it tries to configure, which determines the active channels and the data rate: CTRL_REG_4. This register, as others, is declared R/W; but, whatever I send into it, I read a 'zero' back (which according to the documentation is not even the default value anyway).

After spending long looking for a bug in my spi R/W functions, I skipped that register and noticed that others work just as expected, so I tend to believe there's something wrong with that specific memory location.

Can anybody read from it?


texts: Connecting two power supplies with same voltage rating to increase current output?

texts: My h bridge requires 5v 1 amp. I have a 5v 500mA and another 5v 850mA power supply lying around. Can I join the +ve of both and send that signal to the h brdige so that it can have enough current of 1 A ?


texts: Why is the CMRR of an op-amp defined in such a way?

texts:
Why is the CMRR of an op-amp defined as \$20\log(A_d/A_c)\$?

I know that the value of \$A_d\$ is far greater than \$A_c\$, so we take the log, but why are we multiplying 20 with it?


texts: Why are handheld devices always backlighted nowadays?

texts:
...And mostly, why is it unable to turn this backlight off?

Gaming Consoles (and Mobile Phones, PDA's and other handheld devices) are always backlighted nowadays.
Older devices, such as the GameBoy Color I still have, do not need backlight. The great thing of those backlight-less devices is that you can play them while sitting outside in the sun or near another bright light source.
But with backlighted devices, while being able to use the device in a completely dark room, you will see absolutely nothing while in a bright area.

Is there a technical reason for the need of backlight? Or is it just the new standard?


texts: What type of FLASH (NAND or NOR) is used on microcontoller?

texts:
I am doing a study on file systems for mcirocontollers (MCU), using internal flash only. I find my self asking this questions: What type of FLASH memory is used most commonly in MCU ? NAND or NOR?

This can be useful to know when designing or selecting a file system.

I have been looking at datasheet from various MCU (STM32, MSP430, Atmel), but I was not able to find this information. They just says "FLASH memory". Anybody know what is generally used ?

(I know that some use FRAM, but I asking only about FLASH memory technology)


texts:
I'm implementing a Step-Down Switching Voltage Regulator with Vin = 12V, Vout = 5 V 300mA and I followed the application which is in the page 13.

I have no doubts in choosing all the components around the regulator but how do I choose the right inductor for this application?

I have selected this inductor (SDR0604- 331KL) but I don't know if it will work perfectly for my requirements. What is the influence of the frequency in the inductor for this type of regulators.

Many thanks!


texts: Trying to cut down to one power switch in a circuit with two power sources

texts:
I'm working on a project for a small treasure chest that will open/close, light up, and play sound effects when you walk close to it.

I've prototyped a bit wiring up each of the components one at a time. This is definitely still a work in progress and I'm still a newbie when it comes to electrical engineering so I wouldn't be surprised if I'm doing some stuff wrong.

So one of the things I'm trying to figure out is how to get down to one power switch. At the moment I have one power switch right at the positive terminal out of each battery.

I thought I could add a NPN transistor to the 9v power line in place of the physical slide switch and then place a jumper on the 6v positive terminal right after it's slide switch. The idea being that when I turn on the 5v, the gate pin on the transistor would activate and allow the 9v power through.

I tried wiring this up and found that my voltage on the outer legs of the transistor dropped from ~9v to ~4v. I know there's typically a voltage drop as the higher voltage goes across the transistor, but from what I read that's typically a 0.7v drop, not half the voltage.

Is there something I'm missing or misunderstanding?

UPDATE

Before I hit each of the suggestion bullet points I wanted to post an updated version of the wiring diagram with the theoretic NPN transistor and resistor in it for reference of what I tried before.

Answers to Questions and response to suggestions

Thanks for all of the input so far. Here are responses to each of the suggestions or questions so far:

  Why not just use a double pole switch

  ...you can also use a double pole single throw (DPST) switch...

I didn't actually know those those existed. After that helpful exploration into types of switches I am definitely considering adding one in, but I want to try to go without it for a specific reason that I realize I didn't post earlier. I'm planning on using (still trying to use) a potentiometer that doubles as an on off switch so I have power and volume controlled by one component. Specifically, I'd like to use this:

If the transistor power switch or some other alternative that allows me to use this component doesn't work I'll definitely fall back on a single throw double pole switch. Thanks for that suggestion!

  use a DC-DC converter to boost the 6V up to 9V then you only need to switch the 6V.

  If you want you can just use one battery and something like this to efficiently provide the other voltage...

I was avoiding using a boost converter because I've read that I should separate power for microcontrollers from motors like servos to avoid the current draw that happens when the motor first kicks on. Is that a concern for servos?

In addition to that, I'm hoping to use this same approach for a slightly larger treasure chest, swapping out the servo for a stepper motor. I know there's going to be more complexity in that circuit (adding in a motor driver at the very least) so I'm starting with this step as a functional prototype.

Hopefully that adds some context on why I wanted to go the transistor route. Does this change any of your answers or suggestions?


texts:
I want to charge my 9V NiMH cell with a LM7809. The problem is that I want to limit the current output to 20mA or 30mA. How can I limit the current output from that voltage regulator with simple components? What other components do I need? The input voltage to the LM7809 will be from a 12V source.

I know that this is not the best method to charge NiMH cells and that negative delta V along with temperature monitoring is required but what I'm building is a simple charger to be used in case of a one time emergency situation and I will stop charging it after a specific amount of time like 12 hours.


texts:
I don't understand the explanation. Doesn't the assembler have to calculate 3 * 4 + 5 so it takes longer to execute? Also since 3 * 4 +5 has more characters why does it not take more storage?
From problem 2 of:https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-004-computation-structures-spring-2017/c9/c9s3/isa_answers.pdf


texts:
Is it possible to use a 32.768kHz square wave, such as the output from the DS3231 RTC, as an input for something like the SAMD21 microcontroller? I would rather not have to add a crystal to my design if I've already got a super accurate, temperature compensated and age compensated crystal built into my design.
My go-to idea is to disconnect the crystal output pin and connect the crystal input pin to the square-wave output of the RTC chip. Thoughts? I've only seen other questions about PICs.


texts: What's wrong with my basic light/dark detection circuit

texts:
I've just started playing with electronics, and wanted to make a light/dark detection circuit without using a transistor (they are too advanced for me at this moment.)
I decided to use these components:

LED
10k Resister
9V battery
LDR

I want my LED to turn off when I shine a light on the LDR. I also want my LED to turn on when I cover the LDR. But this does not happen. I'm not sure what is wrong.

simulate this circuit – Schematic created using CircuitLab


texts: My circuit and its conducted emission test result are in the attachment. The circuit is smps circuit for three phase energy meter. As you see it fails conducted emission test. What would you suggest to improve circuit to pass the test. Notice that I cannot add any more component because its pcb is manufactured. I can change only values of components.


texts: How likely is it for a small Li-ion battery to catch fire on it's own?

texts:
Today, I have lost a very small e-cigarette with 260mAh battery probably in an area with a lot of chaff and other flamable stuff,
I'm really scared, tried searching everywhere but didn't find it!
How likely is it, for this device to catch fire on it's own? it had like 60% charge left I believe.
Here is an screenshot of the battery I found on youtube:

Any help/comment is appreciated.


texts: How to get the same output signal but with an increased capacitive load?

texts:
I'm designing a CMOS circuit of a VCO and it works perfectly fine when tested independently. Now when I cascade an other block like a divider to it, the output isn't the same as before. Rather its frequency and amplitude have fallen down. I suspect it's because of the gate capacitances of the transistors in the divider.
Are there any modifications or additions which I can make to achieve the same output as before?


texts: How to reduce noise causing by MOSFET driver?

texts:
I am trying to get +/- 12V and +/- 5V voltage in my board. I am getting lot of noise on the primary side itself as well it is carrying to the secondary side. I am driving the MOSFET with 100KHz PWM signal from microcontroller. I am thinking the source of noise is MOSFET switching. The schematic is as shown below

I have 3.3V PWM signal from controller but at the MOSFET gate I have a voltage -0.8 to 2.5V, thinking which is not sufficient to open completely. If I remove the capacitor C96 and added 50ohm resistor then I can see 0 to 3.3V signal at gate. still I have noise on primary side as well I increased capacitor C98, C99 to 1nF.

Noise is appearing on ground as well and same noise is effecting PWM signal at microcontroller. I am out of ideas on how to remove that noise. Any suggestions can be appreciated.

I tried to add some oscilloscope shots since I don't have reputation in this site so I can't update.

switching is like one MOSFET is switched OFF while another is ON, both MOSFETs never ON at a time.

Some oscilloscope shots

I have added a 250 ohm resistance between MOSFET gate and IC31 NAND gate by removing capacitor C96, C97 and diode resistance network. it means i gave direct PWM signal after NAND gate.
I got less noise but still noise is there, below are the scope shots.

I have a noise on signal as well on ground so can it be some curret floating on the board which is causing noise?


texts:
I am using the PIC18F2680 built-in CAN module along with CAN MCP2551 transceivers, and I am using the plib library for CAN2510 functions.
My question are:

Should we use twisted pair wires (like take CAN-Low and CAN-High wires and twist them)?
The second is more related to the CAN protocol - If two transmitters start transmitting at the same time and are assigned the same low valued ID as mask then who will win the arbitration and if not resolved, how to win the arbitration supposedly if I could write a code for it?
The third being: CAN works on CSMA/CD, so how is carrier sensing done?
How can we use MCP2551 in the Proteus ISIS simulation tool?
I am using the plib/CAN2510 library which is actually defined for PIC18Cxxx series. Can it be used for the PIC18F series or must I write my own functions for init, mask, filter, read, write, etc.?


texts:
We've just started learn about FIR filters in my DSP class. The homework question is:

A particular FIR filter has coefficients {b(k)} = {3, 4, -4, -3} for k = 0, 1, 2, 3. Give the output y[n] when the input is x[n] = δ[n].

Am I correct that the outputs should be:

y[0] = 3
y[1] = 0
y[2] = 0
y[3] = 0?


texts: How to design batteryless circuits with power harvesting

texts:
I'm designing a PCB with
- Micro-controller
- Accelerometer
- WiFi/Bluetooth
- NFC

Is it possible to run this board without any external batteries. I was looking at power harvesting modules, assuming the chips are ultra-low power. From my understanding, NXP offers NFC chips with embedded power harvesting capabilities capable of powering low power MCU.

Appreciate any suggestions.


texts: An RL circuit excited by an impulse voltage source

texts: According to my textbook when an impulse voltage source is connected in series to a resistor and an inductor the impulsive voltage appears directly across the inductor and there is no voltage drop across the resistor. I don't understand why?


texts: How hot can MOSFETs get before blowing up?

texts:
This is different from a lot of other stuff here, but I have a motherboard that has no MOSFET cooling, and when I touch them they burn my hands; they are probably 70-80C.

I just want to know how long can the MOSFETs last under these conditions?

Mobo: Gigabyte 990FXA-D3


texts: Calculate the intensities of the following circuit, using the node voltage method

texts:
Is2=3A;
E1=27V;
E3=18V;
E4=36V;
R3=R4=R5=3 Ohms.

Let 0 be the grounded node.

I tried applying the equations:

G1: 1/R3= 1/3 S

G2: 1/R5+ 1/R4 = 2/3 S

G12: Infinite

The resistance of the wire with the E1 voltage source is 0 (ideal wire) , so its conductance is infinite. How can I apply the method ?


texts: Which thing/component does increase the current on same volt in the charger

texts:
What causes a mobile phone charger or any adapter to increase the current on same voltage. I saw that chargers are rated with different amp on same volt ( 5v.1A 5v,500ma 5v,250ma).

Ohm law says (V=IR)
I am confused....!!!


texts:
I have done a bit of searching and haven't found a solution so I am going to ask here.

Does anyone know how to get Altium to print out a spreadsheet of all components in a schematic library including their user defined parameters?

I know I can place all the components in a library onto a schematic and create a BOM but I would think that there would be an easier and cleaner solution. My goal here is to create a spreadsheet containing all the parts of a library so I can sort them by their part number parameter.


texts: Porting a different variant (STM32F429ZITx) to STM32F429VITx

texts:
I have an FreeRTOS example running on STM32F429I-DISCOVERY / NUCLEO-F429ZI, which has the  STM32F429ZITx MCU inside. But I wish to port this to a new MCU (STM32F429VITx). How do I do it?

The main difference between the two MCUs is:

ZITx version has more IOs (LQFP144). VITx is LQFT100

I understand the HAL libraries will be the same (won't they?). Just the pin configs will change. Am I right?


texts: What are the units when solving Transmission Line iterativelly?

texts:
I would like to know the conductancee,\$C\$, and capacitance,\$G\$, of my lossy transmission line which is configured as an open circuit.

In such a case, I know that the expression that defines the input impedance of the line, \$  Z_{in}\$ is given by the following expression

$$\ Z_L = \infty \Rightarrow Z_{in} = Z_{o}*coth \left( \gamma*l \right)  = $$
$$\ = Z_{o}*coth \left( \ \left( \alpha+j\beta \right)*l \right) \tag 1$$

where

$$\ \gamma = \sqrt{ \left( R+j\omega L \right)* \left( G+j\omega C \right) } = $$
$$\ = \sqrt{  \left( RG-\omega^2LC \right)+ j\omega* \left(RC+LG \right) } = \alpha + j\beta $$
$$\ Z_o = \sqrt{ \frac{R+j\omega L}{G+j\omega C} } = \frac{\sqrt{ \gamma}}{G+j\omega C}$$

I can use a non-linear method to solve \$(1)\$ since I know \$ Z_{in}, L, R\$ and \$ \omega\$

My question is related to the units of \$C\$ and \$G\$ obtained when solving, are these units per length, \$\left[C\right]= \frac{F}{m}\$ and \$\left[G \right]=\frac{S}{m}\$, or the total of the line \$\left[C\right]= F\$ and \$\left[G\right]= S \$?


texts: How does a level shifter shift the DC level of a multi-stage amplifier output to the ground (or zero)?

texts:
As we can see that input fed to this amplifier is the output of final stage of a multistage amplifier and if we apply KVL to base-emitter loop then

Vbb is the DC level acquired from the previous stage.
Now, It is clear that the output of Q1 (emitter-follower) is less than (Vbb-Vbe1) here.I want to know What the importance and function of the Q2 constant current source are here. Further, it is also not clear to me that how the DC level of the previous stage gets shifted upwards and why we are trying to pull that down with the help of this level shifter circuit.

Please help me with the functioning of DC level shifters.


texts: LiFePO4 solar charging problems (amateur question)

texts:
My application is primarily portable ham radio operation. I chose a self-balancing, 4.5 Ah, 12.8V, 4s3p LiFePO4 battery pack, a 28W panel and an MPPT solar charge controller with extremely limited knowledge of batteries and solar charging. My choices were based on power requirements (of course), my desire for MPPT and my need for small, lightweight, highly portable components (my controller weighs only a couple of ounces). I had hoped that in sunlight, the controller would distribute power between the battery and the load. However three factors make this impossible:

The battery pack's on-board PCM disconnects the battery when charging rate reaches 0.02C.
The charge controller passes panel Voc to the battery and load terminals when no battery is present.
My load is not rated to handle panel Voc.

As a work around, I keep the load isolated from panel Voc via a DPDT switch with which I manually connect either the panel or the load to the controller. So, instead of a system in which the controller optimally distributes power, I'm forced to alternately charge and and discharge the battery.

I recently conversed with someone who has been using a DIY LiFePO4 battery pack successfully with my controller model, with none of the problems that I described above.  It seems to me that the difference between his setup and mine must be that his battery's PCM doesn't disconnect near the end of CC charging.

My questions are:

Can someone recommend a commercially available, self-balancing LiFePO4 4.5 to 6 Ah battery pack
whose PCM has no low charge rate threshold?
Can someone recommend an MPPT charge controller that has load
terminals, is super small and lightweight, and that handles a
disconnected battery gracefully?
I'm considering building a 4s2p battery pack from 26650, 3.2V, 3300
mAh, 2C LFP cells (1C max charge rate, 2C max discharge rate). Can
someone recommend a PCM board that would meet my needs?
If I were to stay with my current controller and battery, would it make sense to place a voltage regulator or some other circuit between the controller and the load to protect the load when the battery disconnects? If so, it should ideally consume little power and only drop the voltage when it exceeds 14.6V. (I'm out of my league with this question.)
What is the likely reason for the battery's disconnect at 0.02C?  Wouldn't it make more sense to remain connected and allow the controller to go into CV mode at it's programmed CV voltage of 14.6V?
I realize that I haven't provided much detail and that some of my terminology and concepts might be wrong. What additional
information would make my quesions meaningful and
answerable?


texts: What's the most efficient way to obtain two different DC voltages?

texts:
The plan is to have a RTD (Resistance  Temperature  Detector) measurement circuit, ATTiny85 for temperature reading plus few buttons and an LCD display on the same PCB.

The RTD circuit I've chosen is this one provided by Microchip, which will need 2.5V.
ATtiny's operating voltage is 1.8-5.5V and LCD's 3.3V.

I'm thinking of using 3.3V for LCD and ATtiny85, and a voltage regulator like LM1117T-2.5/NOPB to convert 3.3V -> 2.5V.

Is this liniar voltage regulator overkill for a low-power current excitation circuit?

Can i use a simple voltage divider for this task?

Right now I have a 3.3V PCB power supply from Mean Well which I plan to use for everything in my circuit (ATtiny85, LCD, RTD circuit, buttons + 4x50mA leds)

Thank you

EDIT

Ok, from what i understand, the voltage divider ratio can change because is directly proportional with the load so it's a big no-no for a RTD circuit that needs a stable power supply.

Here's the plan B:

220V -> 9V or 12V wall wart

4.75...36V -> 3.3V for ATtiny, LEDs and LCD display (DC/DC 1A converter)

3.3V -> 2.5V for the RTD circuit (DC/DC 500mA converter)


texts: NRF24L01+ Longer wires or add antenna cable?

texts:
I am using a network of simple 2.4 ghz Nordic NRF24L01 radios (with the stubby SMA antennas) together with pro mini Arduinos. I have to place one radio and sensor inside a metal tube about 6 to 9 inches from the end. I want the antenna to be as close to the end of the tube as possible in order that it stays in range of its base unit.

Am I better having longer wires connecting the pro mini to the nrf24, or am I better off using a small piece of antenna cable?

I ask this question because I do not want to risk diminishing radio signal. i.e.

------------------------------------
Arduino================Nrf24+Antenna ))) ) )
------------------------------------

Or

------------------------------------
Arduino+Nrf24================Antenna ))) ) )
------------------------------------

What would you do, does such a short distance make any difference?


texts: Effects of PWM the source voltage for DC & BLDC motor?

texts:
In DC or BLDC motor control..
The standard is to PWM the H-Bridge switches to control the motor current ..
Why not to PWM the source voltage (V-Motor) and just switch the H-Bridge switches (in lower frequency domain) as needed ..
I know .. it may be not economical due to an extra switching element ..
I just wanna know the effects of this way regardless the economics ..


texts: Flux Transfer of Current also involved in Autotransformer?

texts:
In Isolated Transformer, the primary and secondary are separated yet when there is a demand for current in the secondary, the primary can produce current and transfer it via fluxes. I understood this a bit although I'd appreciate it if someone can share a youtube video of the principle because of this finding I had where when I used gaussmeter to measure the magnetic field, there was no difference between no load and with load as if the magnetic field was already maximum at the start.

Does this also occur in Autotransformer? I'm asking this because when I used a gaussmeter to measure magnetic field of an autotransformer, the no load and load magnetic field was the same. I was expecting the magnetic field to increase with load because there is more current and in an autotransformer, the secondary is just tap of different point of the continuous wire.. unless it's the same principle as the nonlocal flux transfer in isolated transformer? How?


texts:
I'm currently working on a project that's intended for getting old electronics that access networks through the use of a phone line to access the internet. To do this, I'm emulating a simple phone system, but I will need a modem (single chip modem if possible) that will answer at the end of the line.

Hopefully, any modems I'd like to use would have these features:

Up to 56k speeds (V.92 performance - degrades gracefully down to about 1200 baud)
Single chip (not required, but it'd be best if that were possible)

I'd like to interface the modem with an ARM through a serial port, although it'd be fine if the modem just had an 8/16 bit I/O that can be used with older microprocessors. Wouldn't be too bad if I designed this around one of those CPUs, anyways..

I've done some looking on the internet, and really the only modem I could find was the CMX869B. I found no modems so far that have the V.92 performance I would like.

Thanks if anyone has any responses.


texts:
I have a DC motor (I=10A,V=12V.) I want to drive this motor with an H-bridge and want to have speed control with votage (2-12V.)
I think I need a regulator with high current. How can I make a high current regulator?


texts:
I've got a device with STM32F439 microcontroller on it. I flashed the firmware using the J-Flash utitilty (flashed and read back data is same). Then started the application from J-flash: everyting works fine. But when I restart the application without connected J-link the device is not booting.

P.S.: I think it should work if I would perform hardware reset, but device should start automatically on power on.

Update #1: I found a test board with STM32F417 on it and repeated the same action. The same result. Not starting without connected J-Link. But when I push "reset" button - it starts immediately. May be I should perform some internal resets before start?

Update #2: controller boots when there is permanent high voltage level on NRST pin.


texts:
Does anyone know the typical frequency response of a cartridge heater? Normally they work from 120/230 Vac 50/60 Hz, but I would like to know:

If it is possible to use a DC source (120/230 Vdc).
What would happen if the supply is 120/230 Vac, but higher frequency (50-100 kHz).

I imagine that the first case would work fine but, what about the second one? Would the cartridge be properly supplied? Could this reduce its lifetime?
Thanks!


texts: Not enough pins, looking for a "demultiplexer" that keeps state

texts:
I want to control a simple display with a microcontroller. The display has 8 input pins, the microcontroller only 6.

Is there an IC that I can interpose that

lets me set the state of each of its output pins and keeps it that way
requires the least amount of input pins necessary

Something with a serial bus maybe?

I know that typically display controllers are used, but are there general purpose devices?


texts:
I'd like to build a device that can detect a weak electrical connection, likely in the domain of tens of megaohms up through low gigaohms, so that a circle of people holding hands can trigger the continuity signal. There is a commercially available product that does this: the Energy Stick.

After searching, I've found no useful guidance on first steps towards building a device like this. I suspect it is designed to measure tiny currents; the back of my envelope says that if it sends out a test voltage of 5V through a 1 gigaohm circle of humans in series, only 5 nA will flow, which ain't a lot. I don't know how to measure such a low current, nor do I know how to discern it from the noise which I imagine would exceed that signal.

(An idea: perhaps sending an AC test voltage, it could also be detecting an AC current in that same phase on its other pole, and reject noise that way? I don't know if this is heading in the right direction or irrelevant.)

Any/all advice appreciated.


texts: Capacitor bank to smooth out current surges

texts: I am thinking about building a capacitor bank between the PSU and load to smooth out current surges from electric motors. However, if the capacitors are discharging rapidly during a current surge, does that mean the PSU also experiences a current surge in order to recharge the caps, thus negating the point of a capacitor bank?