texts: Two power supplies for an Arduino Mega - How to handle Vin pin?

texts:
I'm using an Arduino Mega to drive 7 servos (only 3 shown in my schematic), and I'm having some problems with the power management. Worst case scenario, the servos will draw about 4 amps, so I got a 7.5V @ 4A power source that I can connect to an independent DC jack on my custom shield.
Now the problem is that since I command the servos through USB, the arduino has to be connected to the USB, which puts a voltage of 4.3V on the Vin pin.
The circuit you see above is what I originally thought. The diode was supposed to keep the servos from pulling current from the arduino when both of them are connected. However, an obvious problem now is that if both sources are connected (USB to the arduino, and my external power source to the DC jack), then you are asking for a ~2.8V drop across that diode.
While I could disconnect Vin entirely, I want the capability of just having the DC jack connected, and still power the arduino so I can control the servos with a pre-programmed routine. But it still has to work when the arduino is connected to the USB.
Putting an extra resistor in series with the diode seems like a very ugly an inefficient solution. Any ideas on how to make this work?
Thanks in advance for your answers!


texts: VHDL multiplication for std_logic_vector

texts:
When simulating I get a run time error, so I'm trying to run a RTL analysis in Vivado to see if the schematic of the component can be created at least. The code is the following

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;

entity multiplicator_test is
    generic(
            WORD_SIZE: natural := 8;
            EXP_SIZE: natural := 3
        );
        port(
            input_1: in std_logic_vector(WORD_SIZE-1 downto 0);
            input_2: in std_logic_vector(WORD_SIZE-1 downto 0);
            result: out std_logic_vector(WORD_SIZE-1 downto 0)
        );
end entity multiplicator_test;

architecture multiplicator_test_arch of multiplicator_test is
    constant SIGNIFICAND_SIZE: natural := WORD_SIZE - EXP_SIZE - 1;

    signal significand: std_logic_vector(SIGNIFICAND_SIZE-1 downto 0) := (others => '0');
    signal exponent: std_logic_vector(EXP_SIZE-1 downto 0) := (others => '0');
    signal sign: std_logic := '0';
    signal aux: std_logic_vector((2*SIGNIFICAND_SIZE)-1 downto 0) := (others => '0');
begin
        aux <= std_logic_vector(signed(input_1(SIGNIFICAND_SIZE-1 downto 0))*signed(input_2(SIGNIFICAND_SIZE - 1 downto 0)));
        significand <= aux(SIGNIFICAND_SIZE - 1 downto 0);
        exponent <= std_logic_vector(unsigned(input_1(WORD_SIZE-2 downto WORD_SIZE-EXP_SIZE-2))+unsigned(input_2(WORD_SIZE-2 downto WORD_SIZE-EXP_SIZE-2)));
        sign <= input_1(WORD_SIZE-1) or input_2(WORD_SIZE-1);
        result <= sign & exponent & significand;
end architecture multiplicator_test_arch;

When running the analysis, I get

ERROR: [Synth 8-690] width mismatch in assignment; target has 3 bits, source has 4 bits [(...)/multiplicador.vhd:27]

The line with the error is 27,

aux <= std_logic_vector(signed(input_1(SIGNIFICAND_SIZE-1 downto 0))*signed(input_2(SIGNIFICAND_SIZE - 1 downto 0)));

Apparently the target (aux) is 3 bits, but really it should be 8.


texts:
This is a conceptual question. Imagine I have the end of a signal chain at a BNC connector and when I hook it up to a scope I observe noise. Signal chain and everything is single-ended. Imagine a DC signal is the actual signal from a single-ended temperature transducer and there is significant noise observed on it.

1-) How can I check quickly and verify whether the noise is common mode or not? I was thinking to use a LP filter to verify it. For example if there is 1kHz noise and 10Hz filter does not filter it I would say it is common mode noise. But Im not sure if this is a method or correct.

2-) If the noise is 50Hz and its harmonics is it big possibility that the noise is common mode noise? if it is common mode noise can it be filter by a passive or active filter? Or a choke should be used?


texts: Confusion with amplifying differential outputs with an op-amp

texts:
A three wire source has differential output but uni-polar(only one signal wire varies wrt AGND). Ground wire is AGND, the the other two is signal SG and the reference SGref. I'm trying to amplify the transducer signal with a gain of ten by using a non-inverting amplifier.

Since the transducer is not single ended output I'm bit confused. Which topology is correct?

simulate this circuit – Schematic created using CircuitLab

At page 41 here shows the differential wiring of channels and at page 37 it says:

  The transducer outputs are designed to work with a differential input
  to the DAQ system for best performance. Transducer outputs are
  ground-referenced differential signals. The output impedance of each
  DAQ signal is 100Ω

(I checked the output and only SG moves wrt to AGND but not SEGref so I think it is unipolar even though differential ended)


texts:
Why does everyone use PLCs in industrial environments, instead of a microcontroller based solution?

For a longer task, the PLC program is as complicated as a microcontroller program.

A microcontroller based solution may be more customisable, and of lower price.


texts: What is the current capacity of this cable?

texts:
This is a 8 wire 0.5mm2 cable (insulator is PVC), there's 17 strings of copper in each wire.

I couldn't find the current capacity of this specific wire on their website but their 1.5mm2 x 8 cables are capable of handling 27A when distance is about 10 meter (reduces to 5A when distance is 150 meter).

I'm going to pass a maximum of 7-8A through two of this wires (other wires gonna carry about 1A) and the distance is about 1.5-2 meter.

Can this wire handle 8 amperes of current?

wires current:
1. LEDs       12V  30W  2.5A
2. Waterpump 220V  40W ~200mA
3. Airpump   220V  20W ~100mA
4. Heater    220V 300W  1.5A
5. MCU*        5V ----  500mA

*there's some relays connected to MCU that's why it's using 500mA.
and two wires gonna be 220V INPUT which gonna carry ~5A in total.


texts:
I have been trying to get a 40-year-old turntable back to life, with relative success until now.
Everything works fine but for an intermittent issue with the motor.

The motor has two modes (for 33 1/3 and 45 rpm playbacks) which work fine most of the time.

Unfortunately, the motor sometimes jump to "full speed" for a period of time. It also happens on startup regularly. After a while (sometimes several minutes) it gets back to normal speed. When it goes wacky like this, it disregards completely any change to the switch or variable resistors that are meant to tweak speed.

I have checked the resistors and variables resistors along the way, which all give correct readings.

My questions:

What is the purpose of the D947 transistor in front of the FG servo motor ? Can it be the culprit ?
Is this a common problem for old servo motors ? Can it be caused by anything mechanical in the frequency generator / tachometer internal parts of the motor ?

Thanks !

Service manual schematics. Unfortunately not many details on the motor:

Actual motor and its control circuit:


texts: How to calculate losses from a DC-DC converter and their effects on battery life

texts:
I have a project that requires an odd voltage of 15VDC. The power pack that I plan to build will be two 12VDC 7AH SLA batteries with a DC-DC converter.

So I know that my starting conditions will be:

Input volts: 24V
Input capacity: 7Ah
DC-DC converter (LM2596): 24VDC to 15VDC
Load: intermittent (6-12 times/day) 15VDC,  ~1 amp, ~30 second duration

How does the DC-DC converter factor into the load calculations to figure out estimated battery life?

How do I figure in losses from the converter?

Supplemental information:

I know that running the same system at a reduced 12VDC results in about a 48 hour runtime on a 12V SLA 1.3Ah battery.


texts: DC motors run slow and weak. Can the culprit be the motor controller?

texts:
I’m working on an Arduino car project. Here’s a diagram:
I am using an OSEPP motor shield to control 4 TT DC Gearbox Motors.
I am powering the motors using 4 AAs batteries, total 4.8V
The problem: the motors run slow and weak.
I believe the OSEPP shield uses L293D motor drivers and I understand these are inefficient.
Will using an Adafruit motorshield with TB6612 MOSFET drivers improve the speed and strength of the motors?
Thanks in advance!


texts: Checking Phase sequence in a 3Ph. supply with uC

texts:
I am measuring the phase to neutral voltage in a 3 Ph. system. The ADC measures each of the phases in turn.
All the voltages are scaled down and offset to center around 2.5V. The voltages are averaged at 500uS
intervals and displayed. This works satisfactorily.
Is there any fast algorithm to check the sequence of the phases in a setup like this.
I can take an arbitrary phase connection as the 'R' phase and get the other phase voltages with an offset of about 25uS(due to the ADC sampling rate). I am unable to add any zero crossing detection, so would it be possible to do this in the firmware only ?
I have to do this check only once during power up.
I did get some prompts, but could not find an applicable solution.
Edits & Clarifications
1)This is a 50Hz mains sinus system.
2)The algorithm is implemented as follows : There are 6 parameters being measured viz. Rin,Yin,Bin; Rout,Yout,Bout ; RIout,YIout,BIout. In one measurement cycle all the parameters are measured in turn, with an interval of 25uS (ADC sampling rate). This cycle is repeated every 500uS, after which the average value of each parameter is computed and converted to RMS.

The measurement of the Voltages , are P-N.

TIA


texts: I am trying to wire up 24 - 3W LEDs ((VF): 2.2V~2.6V (IF): 800mA).  I was thinking about wiring up two sets of 12 LEDs in series and connecting both of those sets in parallel to an LED driver rated at 1300mA.  I was thinking about running them at around 600mA.  Wired this way the current would be 1200mA wouldn't it?  A 1300mA driver would be enough to power it wouldn't it?


texts:
I'm planning to replace an MLCC capacitor (250 VAC voltage rate) with a capacitor MLCC (650 VDC voltage rate).
Regarding the two datasheet of component I'm facing to this curve below :

Can any one help me to understand the meaning of such curve. My capacitor is 100 nF (650 VDC).
I thank you for your support.


texts: How does SPICE calculate Drain current of a MOSFET model?

texts:
I am trying to use a MOSFET model for constructing transistor level circuits in ADS. (For instance, an amplifier). I saw that we could import transistor libraries from various locations (https://www.ece.ucsb.edu/~long/ece594a/ece594a.htm) or from a library (https://ece.umd.edu/~newcomb/pub/spicedsk/bicmosis/bsim3.lib) to ADS/SPICE schematic.

I see that the descriptions of the MOSFET model are available as PDF (http://cmosedu.com/cmos1/BSIM4_manual.pdf) where they describe the equations for MOSFET and values of the parameters (LL,LLN,etc...) are available in the library file (*.lib). This could differ for each model (Equations/parameters).

Now, when we include this model in SPICE or ADS and plot the drain current or transconductance, how do we know that SPICE/ADS uses the particular equations for that particular model? Because the equations are not defined in the model file as well.

I am happy to declare a separate equation for the current equation in ADS for that model, but how its plotting without it? Is it plotting with basic LEVEL-1 equations (square law)?


texts: Chinese FrSky radio receiver, what is this component?

texts:
I have one of these cheap chinese RC receivers mounted on a quadcopter. After one too many hard landings this component broke into pieces. I would like to try repairing the board by replacing it, but I have no idea what this component was, or what was it's value.

I have looked online for a schematic but as it is an unofficial chinese knock-off, I couldn't find any.


texts: Purpose of series resistors in this bipolar rectifier circuit?

texts: The following circuit uses two series resistors, one for each polarity of the supply. I understand function of smoothing caps and overvoltage zener diodes, but the resistors I do not. I would like to understand the function of these resistors and how to calculate what wattage these parts should be. Also, how critical is their resistance value?


texts:
I've been thinking about this issue for a while now and came here for your guided assistance.
Situation:
Ik have 4 resistors (12V/1.25W heater pads). I need to power them with either a 12 or 24V battery.
The problem rises when I've physically placed the resistors. I cannot change the placement nor connections of the resistors on the PCB after physically placing them. However the input voltage can and will continuously change and be EITHER 12 or 24 volt. nothing in between.
So my thought process was basically:
Option1: When powering the resistors with a 12V battery I simply put all the resistors in parallel.
Option2: When powering the resistors with a 24V battery I configure it as 2x 4 resistors in parallel.
With some help on other forums and some finetuning afterwards I came up with the following Mosfet circuit:

Issue:
I'm having trouble and a hard time finding the values for the 3 mosfets. I came up with the following thought process but now I'm stuck.
-Q1 should have a VGSth of around -20V, so that when powered by a 12V battery the resistors are all in parallel.
-Q2 should have a Vgsth of around 20V. This so the current can flow to ground when 2 resistors are in series and powered by a 24V source.
Q3 should have a Vgsth of around -20V.
Keeping in mind that the battery is a Lead-Acid Battery which means that the maximum precision of the configuation will be the charged and decharged value of that battery, so about +/- delta 2V.
My problem is that If I lookup digikey I just cant find mosfet's with these parameters, where I'm I going wrong here? And is there a better way to do this with mosfets? I know one can use a relay but I want a mosfet solution.
Thank you for your time!


texts: Recharge AA batteries in device(skips taking batteries out)

texts:
In principle is it possible to recharge AA/AAA/9v batteries in the device they are currently plugged in?

There are numerous smart chargers for AA/AAA and 9V batteries. The process requires taking all batteries out charging then putting back in. When you are potentially dealing with multiple such devices the experience can only be bettered by carefully modding any device to recharge batteries and skip on the in out routine.

Specifics to test this in my case is a 3V - 2xAA device(vacuum dust collector) and an "Intelligent" battery charger with 12V input and 4x AA/AAA charging slots.

So I am happy with modifications of any sort with the ultimate outcome of :
1)Allowing in device recharge
2)Allowing greater distance between where the device is resting and where  the charger unit is. Think of USB charger + cable as a guide
3) Make the principle generic so it can be used on any device and any charger

Extras : If possible use a high capacity battery bank(26800mAh for examples sake) to power as many battery slots on the AA/AAA charger.
Battery bank used in this example is a 3x USB with output DC 5V/5.5A(max) total and 2.4A individual USB total.

Please check photos for more clarity

The challenges I am aware of :
1) In the device AA/AAA batteries are connected in series with a simple metal piece spanning over both battery terminals.
The 4x AA/AAA  charger connects to each batteries +/- poles individually.
So this might be a problem as the charger needs to adjust output to each individual battery's condition ...

How do you temporarily (
mechanically or electronically ) gain individual access to each battery given they are all connected in parallel inside the device? Modding/Reworking the insides of the device is fine... should be generic solution as most devices use the same Spring to metal plate hardware to raise input voltage from multiple AA/AAA batteries.

2) USB Cable length effect on the AA/AAA charger output. The charger expects batteries to be in the slot and not 1-2m away. Even if the charger might be capable of delivering whatever voltage is needed to offset the length etc.
Being an "intelligent" charger means it may interpret the new circumstances wrong ...


texts:
I purchased an AC adapter for a nintendo wii. It hasn't worked and every fuse I put in to it appears to blow.

The seller has offered to refund me and send me a new one if I send him a photo of the destroyed AC adapter. He's suggested submerging it in water which I feel uncomfortable with for obvious reasons.

What is the safest way I can visibly destroy my AC adapter?


texts: I am working with a 433 Mhz transmitter for an arduino project. I found a Manchester encoding library on github(https://github.com/mchr3k/arduino-libs-manchester). It has checksums built in but the data rate for successfully received packets is very low because a lot of packets have errors. If I implemented a forward error correction scheme would that help the overall data rate. More specifically what is the math to determine if the added overhead is worth it? Thanks for your help.


texts: Why do we want to have an ohmic contact on a substrate terminal of mosfet? What would happen if we used schottky contact instead?


texts: Current Feedback from PWM controlled Motor

texts:
I am looking at two different ways of controlling motor speed and torque of a simple small DC motor. The circuit on the right is the analogue circuit with the current provided by the power bjt. Here, by connecting a very small resistance, we can provide a feedback signal proportional to the current going through the motor.

The circuit on the left uses a PWM signal to control the motor speed. My question is how would you provide the same current feedback in this circuit as was done on the analogue circuit? Would the motor be enough of a low pass filter that you could simply place the small feedback resistor is series with the motor like it was done on the right (but still within the diode)?

Many thanks in advance.


texts: Small (SPST?) Switch to connect two independent circuits

texts:
I am looking for a small push button switch (similar to: https://www.radioshack.com/collections/switches/products/rect-pushbutton) but with the capability to connect two independent circuits (without a common connection). I am using this for a Lionel model train setup.

For example, when the button is pressed, wire A is connected to wire B, and wire C is connected to wire D. However, there is no connection between circuit AB and circuit BC.  Then when the button is released, the circuits are no longer connected.

Do switches like this exist? If so, where would I be able to buy one (either in store or online)

I am new to electrical engineering so please let me know if more information is needed. Thank you in advance!


texts: When talking about antenna gain (dBi), is the largest gain implied?

texts: Since shouldn't dBi gain vary depending on radial location?


texts: How to convert T matrix to Z matrix in two port network?

texts:
How can I transform a T matrix to become a Z matrix for a two-port network?

I found the following conversion to get the T matrix from Z matrix from here :
https://www.tutorialspoint.com/network_theory/network_theory_twoport_parameter_conversions.htm

But I would like to get the opposite of this. To go from T matrix to Z matrix


texts: Can AC and DC be converted and compared?

texts:
This is coming from an IT scenario;

An example server may have a power draw rating of 1.5A at 230V. When connected to a UPS and the mains power supply goes out, the UPS batteries are now providing DC power. Is there a way to calculate the DC draw of the server now, knowing its AC draw (I mean mathematically, not via server management tools)?

As another example to clarify, a router in a data centre is currently giving the following readout;

>show power
system power total =     2771.16 Watts (65.98 Amps @ 42V)
system power used =      1450.26 Watts (34.53 Amps @ 42V)
system power available = 1320.90 Watts (31.45 Amps @ 42V)

This is presumably using 34.53A at 42V, DC. Is a there a calculation or formulae to calculate how much power that is in AC power, and vice verse if a have an AC value to produce a DC value. Or, have I miss-understood and these two power values can not be compared in any way? Or, third option, should I compared their values in Watts?


texts: Is it safe to solder headphone's cable that connected a pc by 3.5mm jack

texts: While I fixing headphone, I wore headphone on my ear and plugged in headphone wire to my computer. Then I was soldering the broken cable of headphone. When solder tip touch the cable, it was listened noisy from headphone. When suddenly I realized that is wrong idea. After this action I removed headphone my computer immediately and other worked headphone plugged in. When I listened worked headphone (play music), it is listened noisy music. I removed the wire of worked headphones from my computer and plugged in my computer again. Then it was become normal. One question:   Are my computer mainboard, cpu, gpu damaged?


texts: Op-amp homework question using potentiometer with my attempt at solving it

texts:
I nearly understood that when Rpot is 0, Vo is highest and when Rpot is 0, Vo is lowest.
So I tried KCL to get Vo when Rpot is 0 (0 turns).

I couldn't get Vo but just 0 volts. What mistake did I make?


texts: Low-pass digital filter for 0-10 V, 4-20 mA input

texts:
I'm looking for a little direction or recommendations in how to select and implement a low-pass filter in software as my background in signals and systems is quite weak. In particular, I'm interfacing to an analog input that accepts either a standard 0-10 V or 4-20 mA signal (circuit can be physically switched) and am concerned about noise that can be expected from running the signal wires over 100 ft adjacent to wiring for lighting systems and other power electronics. The initial idea was to simply have an adjustable window size for averaging samples, but it appears that the time period needed to effectively combat noise in some scenarios also introduces significant lag as well.

Ideally, I would simulate the scenario above with a physical setup and take extensive measurements before starting this, but time constraints make it difficult. I did a quick search for a web tool that generates coefficients and the first thing that Google brings up is http://t-filter.engineerjs.com/. Is this a good place to start or is guess and test a waste of my time without doing more research? Is there a particular type of digital filtering topic that I should direct efforts to researching?


texts: dsPIC30F - How to configure max performance crystal?

texts:
I was looking at Table 20-1, Oscillator Operating Modes, in the Microchip dsPIC30F datasheet, but I'm not sure which configuration will give me the best performance. I want to do an FFT and I need the best performance. I use PIC CSS C Compiler.

Which configuration do I need, and what crystal and capacitors should I use?


texts: Ground plane on dual layer PCB, Is plating needed?

texts:
I am doing my first PCB on Eagle by using dual layer PCB (top and bottom). I route all the through hole components on the bottom and used the top part of the board to provide ground plane. I am going to send the layout to PCB manufacturing and they are providing a free plating for all the holes (all holes are plated by default). My question here is does it effect the circuit when the bottom traces holes are plated? Since the whole top part of the PCB is a ground plane. Do I need to tell them that the holes does not need to be plated?

I know that the ground holes needs to be plated to be connected to the top part but if the whole bottom traces holes are plated, will the whole circuit be grounded? (No signals).

Thank you for helping, Excuse my bad english explanation.


texts:
I'm working in a laboratory environment, where we need to change the state of a few toggle-switches from time to time. As we want more and more remote control in our lab, these toggle-switches need to be operated from remote via USB/LAN or something similar.
The toggle-switches are part of sensitive electronic hardware where I do not want to make any direct changes by soldering.
Has anyone seen an add-on solution or any other idea, how to address this problem?


texts:
I found out, that PMSM motor with large electrical time constant (Tau = L/R) are more difficult to control with FOC. What is the reason? From my experience in control system theory, a system with slow dynamics is more easy to control.

What can I do to increase the performance for large time constant PMSM motors? Higher Voltage? Or are there better methods?


texts: Isolated gate driver for the Class D amplifer

texts: I am trying to simulate the gate driver part for driving the MOSFETs in the class D amplifier with 4N25 optocoupler, not too sure if the connection between 4N25 and MOSFETs is correct.


texts: Can a reed switch be used instead of a flyback diode?

texts:
Just wondering, a flyback diode is typically used to protect the circuit.

Could the magnetic field generated by the flyback be captured to drive a reed switch and protect the circuit the same way a flyback diode does?


texts: What is the best way to measure currents in the range of 50-60 amps?

texts:
I’m working on a single phase inverter which drives a single phase AC motor.
I want to measure the load current which I guess is in the range of 50 to 60 amps. which way do you suggest me to do ; shunt resistor, Hall effect transducer,current transformer or ... .
price and accuracy is important .
thanks


texts: MPPT solar charger for Lead Acid Battery

texts:
I've seen plenty of good MPPT (or similar to MPPT) chargers for solar panels, but they all seem to be made for lithium based batteries. Here's an example of what I've seen: https://www.adafruit.com/product/390.

I have a project where I'm planning on using a 12v 1.3Ah lead acid battery, and I was wondering if there was a good charger like the ones I've seen that will work with lead acid chemistry (I'm assuming that the Lipo/L-ion ones won't work with lead acid). Do you have any suggestions?

Thank you!


texts:
I understand that band pass filters are used in some circuits to filter out the desired frequencies. I also understand that an antenna picks up radio waves in the air and converts it into electrical power for the circuit its attached to, but I am not sure exactly how it picks up on a specified frequency.

I was just wondering if someone would be able to explain to me (or draw) a circuit that contains an antenna and can be tuned to a specific frequency using either band-pass method or some other type of tuning circuit method which will then turn on a LED to signify the presence of that specific frequency.

P.S. Very new to this :(


texts: Optimum number of CANopen nodes in a CAN bus for motor control

texts:
I am studying about the CANopen implementation in a motion control work.

CANopen is a protocol over tha CANbus. It is seen that, in the CANopen specification, theoretically at most 127 nodes could be connected to the a CANopen implementation.

But under what conditions? (i.e at what CANbus data rate and control loop speed).

For example, if my position control loop work @ 5kHz, How can I calculate the "optimum" number of nodes (i.e at most how many motor drives) in terms of reliable CANbus-loading?

If I am not wrong, CANbus loading should not be larger than 30% in event-driven mode, and not be larger than 50% in cyclic synchronous mode. I think that the best way a simulation. I am searching some simulations that calculate the CAN bus loading. There are some MATLAB and Simulink "CAN" bus simulations. But they don't include CANopen protocol implementation.

I want to see a point that after how many nodes (i.e motor drive) connected to the CANbus (in the CANopen implementation), CANbus will start to be insufficient, unreliable and fail. Please consider the control loop speed. I can not find any explanation or even a rule of thumb about this case.


texts:
I want to use the bluradios BLE module. Here is what I am talking about,

Another link for the material available on the site.

Now, I would like to use AT command set to program the module. The site says that there are AT command sets available, but I do not see them on the site.
I am a rookie, so I would prefer using the AT command set, can you tell me what all I need to buy to get this going?
Last time I used rn-42 bluetooth module, and to program that, all I had to do was send AT commands over serial via arduino, Can I do the same with the blueradios module?


texts: Does SRAM need PCB track length/impedance matching

texts:
Well, for educational purposes I've decided to make an FPGA-based board with PCIe, HDMI and other high-speed stuff.

I've usually used relatively slow (35-45 ns) SRAM and having traces routed in 'hit or miss' style works just fine. Now I've decided to use a few IS61WV204816BLL-10TLI 10 ns SRAM chips.

Also, I want to use AS6C6416-55BIN SRAM as they are relatively compatible in pin-out. I have never routed fast parallel busses myself. In my head, I had a rule that everything above 50 MHz must be routed in some smart way.

I've had a read of various articles and got out few things:

Length and impedance matching are two very different things
Length matching has meaning when you have fast rise/fall times
Documentation must somewhere state need of length/impedance matching
Each bus (data, address, control) should preferably be routed on its own layer. As I understand it, this is for better impedance.

As far as I can see, the documentation of the chips I plan to use doesn't state the need for these techniques. But, out of interest, I did this:

(power planes are omitted)

All traces are matched within 1 mm.
Furthermore, I found out that using 90 deg or 45 deg bends may cause reflections and it is better to use arcs. Does this look okay?

So I have a bunch of questions:

Have I made things worse? Should I just run straight lines?
When exactly (overall frequency or edge time) do I need to start length matching?
Is impedance matching necessary in my case?


texts: What happens if the windings of a transformer are connected to each other?

texts:
What happens if one of the poles of the primary winding of a transformer is connected to one of the poles of the secondary winding of said transformer, such that electricity

leaves the power source,
enters one of the poles of the primary winding,
passes through the primary winding,
exits the primary winding at its other pole,
passes through the connecting wire to one pole of the secondary winding,
passes through the secondary winding,
exits the secondary winding at its other pole,
passes through a resistor of some sort (to keep this from just being a short circuit),
returns to the power source?

Yes, I have read this question.  That one describes an isolation transformer shorted at each end, so that electricity can simply bypass the transformer; my question is about a transformer wired in such a way that electricity is forced to pass through both windings, one after the other.


texts: How to converting an alarm to ultrasound emitter?

texts:
I've heard that it's much more cost effective to convert alarms to ultrasonic emitters vs outright buying ultrasound transducers.

How would you go about tackling such a project?


texts: EFM32ZG110F32 Timer PWM with DMA - slow to update

texts:
I have a project where I am trying to drive some Addressable RGB LEDs which require a high-frequency PWM signal (800kHz) with a duty cycle of either 33% or 67%.
I have started from the following project: https://github.com/SiliconLabs/peripheral_examples/blob/master/series0/timer/timer_pwm_dma/src/main_hg_zg_tg.c
I have replaced the duty cycle table with only 33% and 67% as these are the only states that I need and the PWM frequency to 800kHz. The rest of the code is identical to the GitHub example.

#define PWM_FREQ 800000
static const uint16_t dutyCyclePercentages[BUFFER_SIZE] =   {33, 67,
33, 67, 33, 67, 33, 67, 33, 67};

It works beautifully for a PWM of 1kHz and upto 400kHz. The problem is when I try a higher PWM frequency such as 800kHz, the duty cycle (through the CCVB timer registers) is not updated fast enough by the DMA and the PWM keeps its previous duty cycle for one more period, so the value is updated on the next cycle. (Therefore my output is 33% - 33% - 67% - 67% - etc instead of 33% - 67% - 33% - 67%).
Any ideas on how to fix this? I am already using the maximum clock frequency (21MHz - HFRCO) and can confirm the timer used by the timer is at the same frequency. Any ideas if this is just a hardware limitation on how quick the CCV register is updated through the CCVB register buffer or if there is a setting that I have missed.
Microcontroller is EFM32ZG110F32


texts:
This is ATmega2560
http://www.atmel.com/devices/atmega2560.aspx

How can you program this?
Using Arduino as ISP?
USBasp?

Also, since this chip in a QFN (I think this is what it's called), then how do you make the connections?

Is there something like an adaptor where you put in in?


texts:
My electrical knowledge is limiting to say the least. I'm trying to build something, DIY style, to teach myself. It's very simple, let's say I have a circuit and an LED. As long as the circuit is complete, the LED should be off. But as soon as the circuit breaks, the LED should flash.

What components am I looking at to get something like this to work?

I was thinking you have a battery powering the circuit. Since power flows through the path with the least resistance, you put the LED in serial over the switch (that will break the circuit), then as soon as the switch is hit, the LED will flash.

I hope I'm making sense.


texts: How do I make a circuit that charges two 3.7 Li-Ion batteries (in series) with a 5v input?

texts:
I want to make an Arduino wristwatch that can be wirelessly charged by inductive charging. The two 3.7v Lithium Ion button cells are hooked up in series (to make around 7.4v) which powers my Arduino Nano (requiring at least 5v input).

I found out how to transfer 12v through a coil to another coil which receives the voltage and converts it to 5v. The first coil will be inside a "dock" I made for the wristwatch. The second coil should be inside the wristwatch itself. This means that when the wristwatch is placed on the dock, I receive a steady 5v @ 500mA.

What would I have to do in order to get the two 3.7v Li-Ion button cells (in series) to be charged by the 5v received from the wireless induction module?

If you think 5v is not enough, how should I alter the coil to increase the voltage wirelessly transferred? How much voltage is needed for this? Any circuits for a better wireless charging module?

Is there any other way of powering the Arduino with a small rechargeable battery that can be recharged by wireless inductive charging?


texts: How to recover from a brown out on STM32L0

texts:
I'm using STM32L0. My firmware operates at 2V. These are stepped down from 24V. If I have a short of the 24V for a short period of time this causes a brown out on my 2V the voltage begins to oscillate from my step down.

I want to solve this with software.

If seen that I don't get this problem without a load ( while(1), all peripherals turned off. )

I added a for-loop at the start of the program, that held for a few seconds, that didn't help. To me this means the program does not actually reset. Its somehow latches up unless the voltage drops bellow a threshold.

Can I use under voltage detection or brown out detection of STM to prevent this?

I need to force a reset as soon as the voltage drops bellow around 1.8V. I need to react, if I don't want an oscillation, within around 3ms.


texts:
In my design I have a controller which is interfaced to the processor (or SoC) using I2C. The processor has internal pull ups for I2C lines so I don't need to put external pull ups.
The voltage rail for controller is on regardless of the state of processor (on or off).
The voltage rail for the processor is on when the system is on.

The issue is when the system is off the I2C lines of controller are in undefined state and it consumes more power. This issue is not observed when the system is on and the I2C lines are in a valid state.

If I put pull ups outside powered by an always on rail then I see a leakage on the pull up resistors to the processor I2C pins - possibly leakage through clamping diodes for the processor pins.
How can I isolate the I2C lines of processor and controller without causing leakage and undefined state?

I2C lines for controller and processor work at 1.8 V.


texts: 555 Timer Monostable Mode Self Triggering

texts:
I'm working on a simple project with 555 timer. I'm trying to generate a high-state output for 10s when Vcc is applied to the circuit(It is initially off). However, I have not managed to operate the timer correctly due to self-triggering problems.

simulate this circuit – Schematic created using CircuitLab

It was my first attempt to self-trigger problem according to some examples I found on the internet. Trigger is oscillating between 4V-8V in this configuration which leads to repeated negative-edge transition on the trigger pin; therefore, output never falls off zero volt. Secondly, I've tried a zener in parallel with 470uF capacitor to regulate voltage at trigger pin to prevent another hi-lo transition; but, it has failed again. After 3-4 hours of research, I haven't found a solution yet. In short, the problem is to generate a self-trigger mechanism to 555 timer without any external interventions except turning on/off Vcc. Any idea or explanation will be very helpful.

Thanks.

edit: As Dave suggested, I connected an RC network for triggering purpose and got output as I desire. Following graph is the transient response of that configuration.

Blue: Out
Green: Trigger
Red: Threshold

I didn't get a point here. As I know, 555 timer set its output high in monostable mode when trigger has a hi-lo transition. What am I missing?


texts: Does polarity of scope probe matter when measuring ripple of the power supply module?

texts:
Measuring ripple of 28V/12V power supply module across +/- output pins. Does the probe tip have to be placed at +pin and probe gnd to -pin, or it can be reversed?

Having inverted readings when polarity is inverted is fine, but is there a possibility to damage the module or the scope?


texts: ETSI EN 300 220-2 vs ERC 70-03 Limitations

texts:
I’m trying to understand discrepancies between EN 300 220 and ERC regarding the use of 865 - 868 MHz spectrum for SDR. Current ERC 70-03, page 8, says:

Frequency Band: h1.2 Maximum Occupied Bandwidth: Not specified (Note: DSSS and other wideband techniques other than FHSS)
Frequency Band: h1.3 Maximum Occupied Bandwidth: ≤ 100 kHz, for 1 or more channels modulation bandwidth ≤ 300 kHz (Note: Narrowband/wideband modulation)

Both are 863 - 870 MHz.
While in current EN 300 220-2 V3.1.1 Annex B (harmonised) no bandwidth limitations are imposed for 865 - 868 MHz spectrum, except for 100kHz FHSS and “audio & video applications limited to 300 kHz” which obviously has nothing to do with data transmission.
Also, ERC 70-03 describes LBT+AFA as the proper mitigation technique to replace duty cycle limit, while ETSI requires only "polite spectrum access", which it defines as:

Techniques to access spectrum and mitigate interference that employ CCA

So, only CCA (LBT) is required.
The revelant questions are:

My understanding is that ERC is only a recommendation, while EN 300 220 is the obligatory and binding standard. Is this correct?
Can AFA system be considered a “wideband technique” (provided that it divides 865-868 MHz spectrum into many non-overlapping channels each wider than 100kHz)?
How to explain LBT/AFA discrepancy? Previous EN300-220 V2.1.1 did indeed call for LBT+AFA, while current standard seems more relaxed.


texts: How to use MOSFET thermal data for simulating in software

texts:
I have a MOSFET (irfb7434pbf) acting as load switch in a circuit.

The usual operation is well within the SOA region, but, on situations where the load would short circuit, the MOSFET is set to limit the current to a certain value. The ambient temperature is 20˚C and the MOSFET is allowed to cool down before the next short.

During the time the MOSFET is in current limitation I have a MCU integrating the current and the drop over the MOSFET to find out the MOSFETs current thermal status.
And yes, you guessed right, the MOSFET dies. Not always, not the first time around, but it does die.

Now, checking the MOSFET's data sheet the SOA looks like this:

I set the MOSFET to limit at 45A, which produces a voltage drop of 8.7V, which is outside of the SOA area.

And then it is when it gets tricky. In order to simulate the MOSFET's behaviour I run software, which uses the RthJC of the MOSFET for calculations.

At 10ms (which is the short duration), I have a ZthJC of about 0.33.

If I do the math in software, 45A@8.7V gives me 391W, times ZthJC = 391*0.33 =129˚C. That is not a lot of margin but it seems that it would stay within the device's limitations for a carefully measured 10ms pulse.

Maybe I am not interpreting things right. Does it make sense that the MOSFET dies?

In the same datasheet there's a "maximum" power dissipation of 294W, which is lower than the power in one of my shorts. Is that the limit I am hitting?


texts: Switching Supply Noise Filter for Audio Circuit

texts:
I want to make an external power supply for various pieces of "vintage" audio gear that run on +-18V, +48V, -9V and so on.

So the plan is to put several off-the-shelf AC/DC switchers (like Meanwell LPC-35-1050) into an external enclosure with some filtering. Then there would be a CPC connector with a length of multi-conductor cable to each piece of gear which would have 2-3 regulators to make the desired voltages.

But I'm not familiar with the noise characteristics of SMPS. The following circuit is my first attempt at a post-switcher filter / shutdown control. It consists a ballast cap, common mode choke LC filter and remote control power switch that doubles as a capacitance multiplier filter.

So the main question is whether or not the filter needs to get low frequencies. Currently this circuit assumes the switching noise will be in the 50 kHz + range. But is that really true? Can SMPS generate low-frequency noise?

More generally, does anyone see a problem with this design? Again this is for pro-audio gear using convential analog designs like for op amps and discrete "vintage" circuits so the supply needs to be very low noise.


texts: Diode to keep from shorting a battery, would it work?

texts:
I want to set up this circuit to allow instant uninterrupted power boosting of 6 volts. The chargers will only be connected at home when the circuit is disconnected from the motor. I only have 6amp 400V diodes so I have to put them in parallel.

The alternate circuit below would cause a voltage dip while switching and I want to try and avoid that.

The motor is 500 watts. The 6volt is half the Ah as the 36 volt so it is to be used sparingly thus I cannot regulate both as one.

The first schematic should work but am I missing some better way?

simulate this circuit – Schematic created using CircuitLab

[EDIT] Placed the diodes in the correct direction.


texts: Is there an industry-wide name for anti-parallel diodes across an IGBT module's collector and emitter?

texts:
For example, this datasheet refers to a 'freewheeling' diode and a 'boost' diode. The upper diode is the freewheeling diode, right?

If you wanted to switch an inductive load with a single such module, the upper diode would act as the flyback (freewheeling?) diode in parallel with your inductance, and the anti-parallel diode would not be doing much.

I'm curious because I recently saw a failure analysis report of an IGBT module in which the the terms 'freewheeling' and 'flyback' we use -not- interchangeably. I've also seen the term 'body diode' used for the anti-parallel diode.

Are these terms contextual? Is there a preferred name for the lower diode?


texts: How to power several gate drivers with as few power supplies as possible?

texts:
I am designing a 3-phase three-level NPC converter (same type as: https://trinhquocnam.files.wordpress.com/2015/12/t-npc.png?w=767&h=434).

The box this converter will be placed into is fed with 48V (for the control signals). I would like to take this 48V, step it down to 12V (with a DC-DC converter, probably), and power all 12 of the gate drivers that are necessary for this 3-phase setup.

Currently, our design uses 12 dedicated DC-DC converters, but they are pricey ($35/piece) and this solution doesn't seem "clean" to me.

Is there a way to take this 48V, step it down (preferably only once), and send it to all of the gate drivers? I was thinking using pulse transformers may work, but I would like to see the opinions here.

Thanks a lot!


texts: Attempt to build DIY high current power supply from car alternator?

texts:
Recently I had posted about a thread related to a bench DIY high current transformer 12VDC supply that I'm trying to built. But due to some transformer and diode rectifier limitations that project may take a little more time to be completed until I get my hands on a much beefier transformer or two transformers combined enough to do the job. Meanwhile I have a used spare 100 or 120A alternator (I don't remember the exact current rating) in my possession. I was thinking that if I mounted the alternator with an AC induction or a brushed DC motor like from a treadmill I can use it to generate the max current capability of the alternator to run high current 12VDC motors that pulls close to 80-90Amps for a brief testing like under 10 seconds. I've a treadmill motor in my possession, which I think its rated for 90 or 100VDC that is rated for 3150rpm I guess. I can use a pulley system to run it to obtain higher rpms at the alternator. The voltage output of the alternator doesn't really matter too much for me as long as its more than 12VDC, since my goal is not to charge a battery.

What do you guys think about this project? Is it a good idea? Also what is the RPM range required to obtain that max. current capability of an alternator? If you need a specific alternator model I can look it up and let you guys know later.

Edit: I'm aware that I'll need a 12V supply to excite the field windings. Planning to use a 12V transformer with rectifier for that job.


texts:
In "High-speed Digital Design - A handbook of black magic" p. 2,

  The knee frequency for any digital signal is related to the rise (and
  fall) time of its digital edges, but not to its clock rate:

  $$ F_{knee}=\frac{0.5}{T_{r}} $$

  where

  \$F_{knee}\$ = frequency below which most energy in digital pulses
  concentrates

  \$T_{r}\$ = pulse rise time

What's the math and theory behind this equation? I know the max. frequency in a clocked circuit must greater than the clock rate, but why 0.5?


texts: The manufacturing and grading of families of microprocessors

texts:
Intel produces families of seemingly similar microprocessors.  For example,

the Core i5-3320M (2.6 GHz, 3 MB cache),
the Core i5-3360M (2.8 GHz, 3 MB cache), and
the Core i7-3520M (2.9 GHz, 4 MB cache).

Does (or likely would) Intel produce processors like these three

on separate manufacturing lines;
on the same manufacturing line, but in separate runs on different days;
on the same line all in one, indiscriminate run, and only later -- at a test stage -- grade the processors, sort them by grade, and assign them model numbers accordingly; or
in some other way I do not understand?

All of these seem plausible to me except maybe option 1, but what seems plausible to me may have little to do with how a firm like Intel actually manufactures parts.
Please feel free to construe the question broadly.  I am most curious to learn the basics of how such manufacturing is organized in modern practice.
UPDATE
@Shantam gives a better word to use with the search engine:  binning, rather than grading.  Searching with @Shantam's word, one finds @nik's interesting comments three years ago on Superuser.com:

Actually, manufacturers are a smart lot. They 'bin' their produces into different levels of failures. A partly failed cache in a processor instance could become the 'lesser cache, cheaper version' instead of going into the trash bin. Works quite well with the amount of failures seen in fabrication and the surface area of such memory modules (entire cores are 'wired down to sell the instance as a lower range processor -- the Phenom X3?). Nothing wrong in this, and the overclockers are happy to know such things.
The overclocker angle goes this way, if a processor cannot run (heats up) beyond certain frequencies, it is binned to a lower freq target. You get a E6300 C2D (which an overclocker can push up to a higher one with better cooling and maybe good luck on the manufacturers strict 'binning' policies that might have erred towards the lower frequency bin.


texts: How to solve this task that relates to power in circuit?

texts:
The task says:

  Two impedance's are added together in parallel. \$ Z_{1} = 2 - j5 (Ω) \$  ,\$ Z_{2} = 1 + j (Ω)\$ Power on \$ Z_1 = 20 W\$. Determine the reactive power.

I tried this \$P = U * I\$ => \$ P = \frac{U^2}{Z_1} \$ and that would give me the absolute value of U = 10.38 V ,after that using voltage I would find the current that goes through both Impedance's. Following that logic I would then find the current of the source and multiply that with Impedance's
 ( \$ 6.82\angle{-29.91} *
 1.52\angle{29.93} = 61.33 - 35.25j \$ )  and that would give me the wrong answer.

Is there any tip, I think my understanding of this whole concept of power in a circuit is a bit loose, so help about what I did wrong is greatly appreciated.


texts: Does the system COM port baud setting matter for Arduino?

texts:
I have a custom arduino board that is basically like any ATMega328P based setup. I'm using the FTDI friend from Adafruit to communicate with it and when the drivers for it are installed you can see in Device Manager (Windows 7 SP1) that the baud rate is set to 9600.

However, in my Arduino sketch, I have the baud rate set to 115200 and I can communicate with it at that speed from a python script.

So, does the setting on the driver properties actually matter?

Main reason I'm trying to figure this out is that this is for a kit that will be sold and I want a setup that will work for anyone with the default driver install. I'm quite happy if it just works by whatever you set in software, but just wanted to be sure that this was the case.


texts: How to represent K = -A -B in complement 2 in a curcuit

texts:
I know how to represent a number K for example when K = A - B in a curcuit, it's pretty straight forward.
complement all signals from B and trun the carry signal into 1.
Just like the picture below.

My question is if I want to rerpesent K = -A -B + 1 in a curcuit.
If I complement all signals of A and B I still have to add 1 + 1 + 1, the first 1 is for completion of A's complement 2, the second one is for completion of B's complement 2, and the last 1 is simply from the equation K = -A -B +1.
How do I make that happen with using the same FA?


texts: As we know in normal p-n junctions is formed by doping on a single semiconductor so that material continuity is maintained which facilitates the movement of charge carriers between two regions. But in case of metal-semiconductor junction, there wont be any material continuity as metal is deposited over the silicon substrate. Then how electrons movement takes place??


texts: Unable to identify symbol in stop/start/retain relay

texts:
I've been doing some research on stop/start/retain relay circuits. Here is one circuit I found online:

I'm having a hard time identifying the component(s) between L1, L2 and L3 and the motor. My thought was that it is some kind of thermal switch, but it doesn't match any of the symbols I have found online. Or it is a relay contactor, but again it doesn't match any of the symbols I have found.

Could someone please help me to identify this component(s)?


texts: Unshown compile error in Altium Designer 13.1

texts:
I have a schematic sheet in Altium Designer 13.1 and I made an unconnected label (in the red rectangle) on purpose.

My problem is: when I compile this sheet, there is no error shown in the Compile Errors tab but I definitely have one, a "Floating Net Label" type.

Do I miss some settings here and that's why I can't see the error(s)?


texts: How to simulate immobilizer (RC remote control anti theft device) signals using a motor controller and sensors?

texts:
We are working on an electric scooter (moped) project. We have added a PCB to it.
The scooter has a remote functionality anti theft system (radio controlled like most cars). We would like to retain the immobilizing and theft alarm functions but remove the radio controlled lock/unlock function.
Can anyone help us understanding this? We want to simulate those functions (beeping while someone is trying to steal the scooter) with some sensors without using the existing system that the scooter came with.
Many thanks! Much appreciated.


texts: Should a soldering iron have a grounded plug?

texts:
I'm talking about the plug--not the tip so it's not a duplicate question.

I'm interested in buying the folowing soldering iron (https://www.amazon.de/VicTsing-einstellbarer-Temperatur-Entlötpumpe-verschieden/dp/B01HTIY61E/), however I noticed it's using a Europlug without ground (only 2 pins). Would that be fine or dangerous?

Thanks for the info!


texts: Can't charge a cell phone with a power bank I built

texts:
I built a power bank using a 6 V, 4.5 Ah battery.

When I connect a cellphone for charging, my phone shows that it is charging, but the phone's battery level is not increasing. Instead, if I run some online games while charging with it, the phone's battery level is decreasing.

I used the 7805 IC and two capacitors to establish a 5 volt, 1 A current.

When I measure the output voltage and current, it is fine - but when I measure it while charging a mobile phone it shows the output voltage as 4.1 V.

What should I do to fix it now?


texts: switch a PN2222 transistor at 18 volts, with variable 0 to 30 volts input

texts:
Level: transistor beginner (sorry for that)
Question: is a resistance R1 110 Kohms the good one to put before the b branche of a PN2222 transistor, if we want this transistor being in switching mode when the 0 to 30 volts variable voltage coming into the circuit is above 18 volts, and make the LED lighting above 18 volts ?
Image of the circuit:

I put a green led in the circuit
Data:
PN2222 transistor data: beta=300; Vce_sat 1=1; Vbe_sat=2; Vce_max=30
LED: Ic=Iled=0,025 A; Uled=2V (green led)
R led= 600 ohms (Vcc-Vce_sat-Uled, with Vcc at 18 volts)
Source of tension: from 0 to 30 volts
Tension where the transistor should light the LED and let the electricity running (contact between c and e): 18 volts
calcul done
As:
Vcc = Vce + Urel,
Vce = Vce_sat,
Urel = Rrel x Ic,
Vcc = Vce_sat + Rrel x Ic <=> Ic = (Vcc - Vce_sat) / Rrel
Then, for Vcc = 18 volts: Ic = (18-1)/600=0,0283 A
And as:
Ib_min = Ic / ß
Then, for Vcc = 18 volts, and beta = 300,
Ib_min = 0,0283 / 300 = 0,000094 A
Lets apply a 1.5 security coefficient to get ib_sat
Ib_sat = Ib_min x 1.5 = 0,000094 x 1,5 = 0,00015 A
Then, as:
Ve = Ur + Vbe,
Vbe = Vbe_sat,
Ve = R x Ib_sat + Vbe_sat,
so R = (Ve - Vbe_sat) / Ib_sat
which gives for Vcc = 18 volts:
R = (18 – 2 ) / 0,00015 = 110212 Ohms
Is it the correct value for R to light the LED when the variable tension reach 18 volts ?


texts:
I'm working on a high school project were i need to make a score board using 420 LEDs controlled by an Arduino.

I can see that the 74HC4105 demultiplexer will let us turn three pins into 8, but if we select pin 000 will the output stay on?  If not, do we have to keep turning all the LEDs on over and over, and will they be dim?

Even if we turn 3 pins into 8, we would need more pins than we have.  How can we control 420 pins with only 20 (or maybe 56 on the Mega?)

We want some kind of circuit that will remember whether each LED should be on or off.


texts:
I want to PWM-switch neon bulbs.

The power supply delivers about 220V DC. And I have to switch the bulbs in the "positive" section, so this means PNP, I can't switch them NPN because a NPN Transistor is used to switch on and off specific bulbs, the PWM is for regulating the overall brightness.

So I'm looking for a solution to switch the voltage PNP.  Device should be able to switch 220V DC and 50mA at least.

The PWM control signal is  800Hz, level 5V DC out of an ATMEGA328. If there is a SMD solution that would be great, but doesn't need to be.

What could I try to use here?

What I tried to search for:

1) Optocoupler :  Sadly no PNP Optocoupler found

2) Relais:        Not Possible, too slow


texts: Parallel connected LED and current problem

texts:
First of all, I don't have much electronic knowledge.
I am having trouble connecting the LEDs in parallel.I have two types of LEDs which have different power.Here are some current measurements:

The red LED draws 1A when driven alone.

The blue LED draws 0.5A when driven alone.

When connecting two red LEDs in parallel:

When connecting two red LEDs and 1 blue LED in parallel:

(1) Why did the 2 red LEDs not draw 2A?

(2) Why 2 red and 1 blue led did not draw 2.5A?

Note:My power supply is 30 volts and 50 amps.


texts:
Hello electronics experts,
I am basically a computer engineer but because of a robotics project i am in a need of designing small ups for few seconds backup ( Approximately 8-10 seconds ) but facing following problems  -

Capacitor not charging up to 5 volt even if connected to power bank without using any resistor and without any load at the output.
Is a resistor is always needed if we wants to use a capacitor?
Is a load is always needed and then only capacitor will start conducting?

I am just a beginner in electronics, so please Help.
Thank you all in advanced


texts: Reason behind loss of low frequencies in square waveforms

texts:
I was reading this page of a textbook and I noticed following sentence. I was wondering if someone could elaborate more on following for me please?

  AC coupling may cause voltage droop due to the loss of low frequencies

Unfortunately I couldn't find the rationale behind above statement and find out why voltage droop may happen in low frequencies.


texts: 74HC/HCT: What to do with unused inputs and why?

texts:
If I'm using an IC in the 74HC or 74HCT family, and I'm not using all the input pins, I understand that I should not leave them unconnected because they will float. But what exactly should I do with them, and what are the pros and cons of the different options?

For example, if I'm using the 74HCT08, which has four AND gates, and I'm only using two of the gates, what should I do with the inputs of the other two gates?

I've seen various recommendations in various places, such as...

connect them directly to Vcc
connect them directly to GND
connect them to Vcc through a pull-up resistor
connect them to GND through a pull-down resistor

What are the pros and cons of each of these options? Which option is best for stability and low power consumption?


texts: BJT problem. Are my calculations correct?


texts: How to design a unit that outputs 1 on the first rising edge and 0 on the second rising edge in the design of a multiplier?

texts: I want to use this unit to control the shift register in a multiplier. The shift register should load then shift and load... until it stops. When the LSB of the multiplier is 0 it should simply shift and not load. The easiest way to do  that is an AND gate. But, I need a signal that doesn't align exactly with the rising edge of the clock, in order to avoid any reading conflicts. I have a feeling that there might be an easier solution, I would appreciate any ideas.


texts:
Ihave a problem. i need to solve is as fast as possible.  Maybe someone here has an idea what to do.
I have WS2812 LEDs.
Beetween each pixel is 30cm cable.
I have to drive about 150 pixels of them with one controller.
The Problem there now is that there is a flickering and random color change sometimes.  But we have only connected 8 pixels yet. And the issue appears after 2 to 3 pixels.
I think its problem with Data but i dont know how to solve it.
Im using an ESP32.
Is there anybody here who can help?
I hope to find the solution asap. Thanks in advance

Here a picture of the wiring. Its an old picture. Ive rewired it a bit better, but same pricipal.


texts:
I have been trying to find a non-isolated buck converter (12 Vdc input to 5 Vdc, 2A output) with the CE certification.  This is similar to a USB charger that fits in the cigarette lighter of a car but with wires or screw terminals for input/output instead of the USB and cigarette connectors.

I know these converters are very popular and are used in cars/boats, solar, lots of battery powered devices.  I don't think it's a coincidence that none of them are CE certified.  How are these imported and sold in Europe without the CE marking?  Is there an exception for very low DC voltage devices?


texts: Order of Components in an LC Circuit (Network)

texts:
If I have a source free LC circuit with two capacitors and two inductors, will the order in which they are placed in the loop effect the current and voltage characteristics?

There is an initial voltage in the circuit.

So for example, are these two circuits equivalent?


texts: Implementing a circuit that takes a 3-bit number and multiplies it by 8 using only 1 4-bit adder

texts:
I was solving a past exam and this question popped up and nobody seemed to agree on an answer.

Someone suggested this solution which is just hacking your way to the required result.

That suggested solution:

My suggested solution:
I thought of a 3-bit counter that re-uses the same 4-bit adder 8 times to add the number to itself 8 times. (since 8X = X + X + X + X + X + X + X + X)
It should add the bit to its corresponding sum 8 times but I am having some issues formulating it, especially that I know the output is going to be X2X1X0000 assuming input is X2X1X0 and I don't really understand how I am going this counter-adder thing do this job.

I did some Googling and I ran into the "shift and add" algorithm but that was never explained to us in any course, not as an algorithm nor as a circuit so I figured it wasn't the solution the examiner was looking for.


texts:
As shown in the picture below, thermal impedances of an IGBT device depends on the temperature. However, there is a strange phenomenon as follows. While with increasing the temperature, steady-state impedances will increase, but you can see  that at a low time some low-temperature impedances become larger than high-temperature ones. Why?
Note: We can model such impedances by resistor-capacitor circuits. Do we have the aforementioned phenomenon in RC circuits, namely lower value at a low time but higher value at a high time. How can justify this?


texts:
Given is fundamental frequency \$50\,\text{MHz}\$, \$50\%\$ Duty Cycle, Rise and fall time is \$5\,\text{ns}\$, wire length is \$30\, \text m\$, \$R_i=50\,\Omega\$ and \$c\$.

How do I calculate wavelength?

I'm confused which formula I should use.

Should I simply use
$$\lambda=\frac{c}{f}$$

or

$$f_{sig}=\frac{1}{t_r\pi}$$

$$\lambda_{sig}=\frac{c}{f_{sig}}$$

\$t_r\$ is rising/fall time

How should I calculate it?


texts: Bin Sensor that tells when something has been placed in it

texts: I’m planning a bin project, essentially before anything can be placed in a bin, it has to be scanned. Any suggestions on a sensor that can be placed inside the bin that will ensure that the scanned item has been placed and bin and nothing other than the scanned item has been placed in the bin.Preferably more environment sensing than machine vision.


texts: This is a circuit I am reviewing to generate 12V DC to 220V DC (output). At what component configuration can this circuit generate such output. The goal is to be able to at least supply 70 Watts of power, to be usable for common devices like laptops to be plugged into it.


texts: How does this capacitive soil moisture sensor work?

texts:
I’m trying to figure out how the following soil moisture sensor works.

It’s obviously a capacitive sensor where the capacitance changes when the soil moisture varies.

However, as you can see, the sensor is ENCLOSED, so how does the capacitor get contact with the soil moisture to sense it?


texts: What is the infrared controller in Nook Simple touch?

texts:
I got an old Nook Simple Touch from my brother and it worked before. But it has been covered with mold so I removed the plastic case and it still boots, but cannot respond to any of my touch.
I found some kind of infrared grid touchscreen on the front of the motherboard, like this (I got the image from here):

I think it needs the case or something to control the light direction. But I have already thrown the case away in the trash!
So my question is: How can I make it worked again, and if I can't, what is the infrared controller IC and how can I use it to emulate a touch or at least its datasheet?
I thought of somehow simulating the touch by connecting peers of IR transmitter and receiver together by a wire, but it didn't work.
I think this question is more suitable for the Electronic StackExchange than Ebook StackExchange, so sorry if not.
Thanks for any help!


texts: Questions about Inductive Kickback and what causes an inductor to discharge?

texts:
This is most likely a dumb question, just for some reason I have just forgotten the fundamentals about how charging and discharging work.
Essentially my question is for this simple circuit:

When the switch is closed the inductor keeps charging and when it is opened it discharges through the diode. Now here is my question. Why doesn't the inductor keep charging as the current is entering back through the inductor? This is the fundamental knowledge I have forgotten.
Is it due to the diode voltage drop? Hence charge out is always less than charge in? (I know its a bit of a dumb question but I would like to just clear  my confusion).
Also if the diode wasn't there and say the inductor had charge in it already (the switch is open at this time) and say the diode shorted completely, no charge will be lost will it?
****In short what causes an inductor to discharge again and how does it discharge through itself (when the switch is open). Does it discharge through itself due to internal resistance or no? ****


texts: Arduino - Controlling multiple 12v motors

texts:
I have seen this thread but it wasn't helpful.

Is it possible to connect four 12v/4a motors to one Arduino and control them independently? I'm a beginner to circuits and such - that's the part that's worrying me,
not the Arduino code. The Arduino has only one 12v output. How should I go about this?

Edit: Whoops sorry. It has only one 5v output, noob error :/

Also, what if I need to control three of these instead? 12v 500ma Solenoid valves.... should I still be using relays?
http://www.ebay.in/itm/1-4-Electric-Solenoid-Valve-12-volt-Air-Water-BBTF-/290578532901


texts: Question on superheterodyne FM receiver to find the range of local oscillator and the image station ...?

texts:
Consider a superheterodyne receiver designed to receive the frequency band of 1 to 30 MHz with IF frequency 8 MHz.

  a) What is the range of frequencies generated by the local oscillator for this receiver?

  b) An incoming signal with carrier frequency 10 MHz is received at the 10 MHz setting. At this setting of the receiver we also get interference from a signal with some other carrier frequency if the receiver RF stage bandpass filter has poor selectivity. What is the carrier frequency of the interfering signal?

My solution:

part a)

        1M+8M     < f(local oscillator) <   30M+8M
           9M Hz  < f(local oscillator) <   38M Hz

part b)

The image station will be at = fc+  2f(intermediate)
                             = 10M+2(8M)
                             = 26M Hz

Please look at my answer and correct me if something is wrong.

This is one of the problems in chapter 5 of Modern Digital and Analog Communication Systems, 4th edition. I couldn't find the solution manual for this edition, only for 3rd edition which did not include this question.


texts: Antenna gain improvement by increasing directivity but not with radiation efficiency

texts: My antenna gain got increased with directivity but not with radiation efficiency. I mean the radiation efficiency remained same. Speaking of remaining radiation efficiency, this improvement on the gain will not mean that antenna will transmit its power at longer distance than it used to. Can we call it right?


texts:
I am using EAGLE and have a 2layer pcb design. I have signals on both sides and ground on both sides of the board.
I am not able to connect my THS4509 opamps thermal pad (which is the opamps ground) to my pcbs ground. The thermal pad has its own isle.
I can't route the thermal pad to ground because the pins are too close to each other.
The thermal pad is pad17 I need to somehow connect it to the ground polygon. But there is no room.

How can I solve this problem?


texts: ATtiny25 PWM LED driver with brightness control

texts:
I'll be building a piece of RGB LED jewelry for a gift. It's basically a pair of earphones with one or two RGB LEDs on each, with a small ATtiny25-based PWM driver in a small enclosure.

I'll probably be able to devise the firmware myself; however, since I'm going to have a good few inches of wire going to each phone, I need some sort of LED drivers, and that's where I'm not sure how to proceed.

The basic idea is for all the LEDs to be displaying the same color at a given point. The MCU will fade through all colors in sequence using software PWM. However, I would also like to implement a control for the overall brightness of the LEDs (once ambient noise goes above a certain level, it starts pulsating along with it, kinda like a VU meter). I'm thinking about one PWM-driven 'brightness' MOSFET to control the, um, source voltage (?) to the other three 'color' MOSFETs. Is this the way to go?

I have a lot of BS170s and not much else in the way of FETs (BF245, 2N5457 JFETs), so that's probably what I'm gonna be using. I'm thinking of going all-out SMD on this... I only have the tiny25 in SOIC, anyway.


texts: What is the procedure for going from discovery board to a deployable solution?

texts:
Just to clarify with some context:

This voice based keyword detection requires an mbed discovery board; and I am sure some min flash size.

Even for a hobby project, i.e. personal home automation, putting several discovery boards in various rooms is costly and not ideal.

When answering the question, please consider the following two use cases:

1) What do business do for going from PoC to production?

2) What would hobbyists do that is similar to a business but on a smaller scale of course?


texts: MULTICOMP MCAK304NBWB KEYPAD: What are the pins 8 and 9 connected to?

texts: According to the datasheet, the 7 pins are from the 4 rows and 3 columns. What are the other 2 pins connected to ? The image shows 9 pin outs.


texts: RGB LED Strip - several question from newbie

texts:
I've just bought 5 meters long 12V analog RGB LED strip and I'd like to turn it on!
There're 60 LEDs per meter so, totally 300 LEDs and each LED consumes 20mA.

Here're my questions.

From internet guide like this(https://learn.adafruit.com/rgb-led-strips/usage), power is directly connected to white line then where is ground? (single LED have 4 legs - Red, Green, Blue and Ground, isn't it?)
If I have 12V DC Adapter and it throws more than 6A current, can I use it without resistors?
If the adapter throws more than 6A current, what happen to remained current? just gone away to somewhere?
Can I use higher voltage adapter if I use proper resisters?

thanks in advance and sorry for my bad English! :(


texts:
I want to see a signal (5-25 microvolts  | 1-35HZ) on my computer.but I dont know electronics so I just have one question:

I need to amplify THE signal to reach 0-5 V for ADC.Does serialing two instrumentation amp like AD620 or AD8429 to get like 1M gain have any side effects?

or is there a better way to convert 5-25microvolts  to 0-5 V ?


texts:
I'm getting ready to print up a board for a project using a dsPIC33FJ256GP710A.  I've currently got it running on a EasyPic Fusion devboard.

I see that there are a bunch of pairs of PGED's and PGEC's available to choose from for layout convenience.  I also see that there are config bits that need to be set for which ones you pick.

So, lets say I plan to program the dsPIC on board, using PCED3 and PGEC3.  Until I set the config bits, how will the chip know that that's where the programmer will live?  How can I set the config bits until the chip knows where to look for the programmer?  I suspect that the chip will program from any programming port pair, but will only debug from the configured pair.  That said, I've been searching data sheet which sent me to the Family programming reference, http://ww1.microchip.com/downloads/en/DeviceDoc/70152c.pdf, and I can't satisfy myself that if I try to get the answer by setting the programming ports to something other than what the built-in programmer is tied to that I won't brick my $25 daughterboard with the PIC on it!


texts:
I wanted to know if it would be physically possible to run LEDs off of some sort of transmitting device, wirelessly? It's important I be able to use extremely small LEDs and have the smallest possible parts connected to the LEDs to use them in the spaces I would like.

I would like to be able to operate the LED up to a few feet away so it's not limited to being within just an inch or two of the transmitter.

The other thing I've noticed on some of the online videos is the coil that is connected to the LED is quite large. Ideally, I'm trying to get both the LED and whatever is necessary for the receiver component to fit within a 5mm W x 7mm H cylinder. Obviously, quite small.

Can this be done?


texts: Combining CMOS and TTL with drivers and Leds with relay driver

texts:
I need some practical advice on how to combine different component types.
I designed a circuit with at the heart an up/down counter (74f269) The outputs of the counter are connect to via 330  ohm resistors and leds to ground level. They also need to drive a relay-driver. Furthermore these outputs are connected to a 74ALS11N (3 triple OR-gate) and 74HC4075 (3 triple AND gate). The OR gate yield Q0 v Q1 v Q2 v Q3 v Q4 v Q5. The And Gate Q0 & Q1 & Q2 & Q3 & Q4 & Q5. The outputs of the OR's and AND's are each fed to 74HC00 (NAND).
The NAND gates do an AND operation with the value and that of an NE555 that is used as debounce for a switch.
All components are fed from a 5V voltage source.
I read about combing different logic families and am a bit confused about when to use resistors and how many:

I read connecting TTL to CMOS I need a pull up resistor. The 74ALS11N output connected through
a load to ground (pull down). Can I still connect the AND and OR gates to the outputs of this counter?
Am I correct to assume that I do not need a resistor when an output of a gate is connected to an input of a gate of the same logic family, both for gates in the same chip and in another chip. Nor do I need resistor when CMOS of one type is connected to CMOS of another.
One NAND drives both U/D of the counter an input of an XOR-Gate (HEF4075BP) do I need resisors and if so pull up or down? Also: can the 74HC00 drive both the input of the counter and XOR gate?
Do I need a resistor for the output of the NE555 to the NAND-gate?

=========================
As requested in the comments below, I added the schema of the circuit. It's a DIY project so bear with me if the schema is not up to par with industry standards. The strange looking GND and 5V connections on each chip and the bridge were introduced, because Eagle could not route a single sided PCB.
I'll place the soldering pads around the circuits an then connect the GND and 5V of the chips with wires.
The functional purpose of the circuit is to count down and up (6 bits) upon button pushes and have underflow and overflow protection.


texts: Help me with a 4S1P for vacuum cleaner please

texts:
I'm new here, and this is my first time trying to fix my Ilife V7S pro vacuum cleaner battery.

The original battery is this:

I want to replace the 4 18650 with my INR18650-25R daweikala
I have seen several videos of how to solder, risks of 18650 and other stuff, but after disassembly the pack (4S1P), i found this module, I'm not sure if it's a BMS or just a balancer or just a charger or a mix of everything.

This is the module:

As you can see, it has: V1, V2, V3, V4, P+, P- and B-

but I dont see B+

Could you please guide me how to make the connections? I see just one plug to discharge and to charge.

Thanks infinitely

Thanks Bruce. However I have another doubt. I included an image of what I understood the squematic is, but even after I joined all the wires, in the output of the module (P- and P+), i'm not getting the 14.8v only about 5v Do I have to connect the (-) and (+) (from the cells in serie that gives 14.8v) to the P- and P+? The terminals from the module P- and P+ should be 14.8. The one with thick wires i have from the battery in the image. BTW, is there a module that not only protects the batteries, but also balance the charge / discharge two in one. How should I look for it? Thanks.


texts:
Short question: Would it be possible to use a series inductor to limit the inrush current when switching on (or briefly loading) a DC motor?

Longer question: I have a battery-powered motorized toy which for convenience I'd like to run from a power socket instead (to avoid having to recharge and replace batteries).  Currently it uses 4 1.5v batteries and if I measure it in steady state it draws about 0.8A at about 6V.  The way that the toy works is that the motor is usually running continuously with very low load, and occasionally it briefly gets some load on the motor.  I don't know exactly what kind of motor is used, but assume it's cheap and simple.

I bought a (cheap) 6V power supply which is allegedly capable of delivering 1.2A, but its current protection cuts in when switching on the motor.  As I understand it (please forgive my very basic knowledge here!) the motor presents an extremely low resistance when it's starting up, and so tries to draw a lot more than its usual 0.8A.  When running from batteries, I guess they have a maximum current that they're able to provide, so everything gets automatically limited.  When the motor is up to speed, its "effective" resistance rises due to its motion, and it reaches its steady state of drawing 0.8A.  I expect that when the motor experiences some mechanical load, then the drawn current also temporarily rises, but again the batteries can only provide what they can provide.

When it's connected to the mains power supply, the motor tries to draw much more than 0.8A (I'm not sure exactly how much more), trips the power supply's protection and the power supply cuts out.  The motor slows down again, the power supply recovers and switches back on, but then the motor tries to draw too much again and it cuts out again.

I've read about "motor inrush current" and "current limiting" but for this simple toy I'm hoping it won't be necessary to build a custom driving circuit with transistors or mosfets and I can't believe that a temperature-based thermistor solution is ideal (partly because of wasted heat, partly because my intermittent load is not temperature-related).  From what (very) little I know about inductors, it seems that one of those in series would "fight against" the sudden change in current and develop a voltage across itself at startup.  So I'm hoping this would temporarily limit the current to say 1A.  In the steady state this voltage across the inductor would drop to zero and it would then act as a pure low resistance, which is exactly what I think I want.

It doesn't need to be super-precise or to have a perfectly-flat 1A current limit, it would be fine to curve around 0.9A or 1.1A, but I don't know of an easy way to measure what's going on with a simple DC amp-meter.

Could this be the right way to go, or is it too simplistic?  And how would I calculate what kind of inductor would be suitable?


texts: Force voltage to 5V or 0V from solar panel

texts:
How can I ensure that a circuit powered with a solar panel will always receive 5V or 0V, but not something in between that would damage the circuit ?
I have a linear voltage regulator that ensures the voltage is not more than 5V, but it doesn't protect against undervoltage when the solar panel outputs a voltage lower than 5V + regulator dropout voltage.
Would a Zener diode with a 5V breakdown voltage after the regulator work ?
Are there solar panels that always output a voltage that is 0 or above some voltage (5V + regulator dropout voltage in that case) ?
Edit:
This is a hobby project. What I want to power is an Arduino MKR Wifi 1010. The arduino can already charge a LiPo battery when it is powered via USB. It will never draw more than 150mA.
The solar panel I have is described as 10W 12V, but it seems it can output less than 12V, hence the question about handling lower voltages.
Ideally, this circuit is always on. It will be "asleep" most of the time, only sending sensor data through wifi once an hour. Asleep meaning that it  uses the low-power mode of its cpu, disabling everything except RTC.


texts:
What is the maximum wattage (and maximum recommended wattage) for a single ribbon cable wire.

I believe the wire size is 28 AWG (maybe 26, but let's call it 28 to be safe), stranded copper.  The length of the cable will be no more than 3', and it will either be 40 conductor or 50 conductor ribbon cable (don't worry, I will not be using any 80 conductor IDE cables or anything silly).

Anyway, while googling, I keep finding amp ratings and "Ampacity" charts, but they don't contain any references to the voltage those amps pertain to, and I think they might be AC specific, so it's not super helpful to me.  Also, I keep finding completely conflicting information.

More Info:

I intend to run 12V DC on the cable and am trying to determine how many threads of cable I will need for particular amperages @ 12V DC.

Clarification:

It's my understanding that wattage (V * A) is what matters with wiring -- (i.e. because if the insulators melt at 5A @ 10V then it will also melt at 50A @ 1V, or 1A @ 50V, etc.)

If I know the wattage, I can determine the safe amperage at any DC voltage within the 300V rating.

Other Thoughts:

What is a reliable resource for finding out this kind of information? (Teach a man to fish...)

Is there a difference between "amps" and "Ampacity"?  Wikipedia is kind of vague on the subject.

Thanks!


texts:
I'm working on a problem that involves a Ćuk converter. The question asks "find k_c (a gain for a controller) such that the system is marginally stable".

So I got the properly space-state model with matrices A and B. Then, I set the real part of the eigenvalues of A equal to zero and try to solve for the unknown k_c. After that I got that kc must be equal to -1.8 approximately. That is, a negative gain.

Is it physically feasible to implement in real life?
Does it make a difference to use a positive gain or a negative gain?


texts:
I'm trying to figure out how to VHDL, and am having some difficulties writing a simple flip flop. I want a T flip flop that runs strictly off of the clock, changing state every time it receives a rising edge.

The syntax errors are somewhat cryptic and I'm having difficulty figuring out what is wrong.

library lattice;
use lattice.components.all;
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity blinker is
    port(
            clk     :   IN  STD_LOGIC;
            ledout  :   OUT STD_LOGIC
    );
end blinker;

architecture Behavioral of blinker is
    signal ledState: STD_LOGIC;
begin
    process(clk)
    begin
        if(rising_edge(clk)) then
        --if clk'event and clk='1' then
            if ledState = '1' then
                ledout <= '0';
            elsif ledState = '0' then
                ledout <= '1';
            endif;
        endif;
    end process;

    ledout <= led_state;

end Behavioral;

I attempted two methods of running on a rising edge, neither seemed to make a difference. This is what the output looks like:

I'm completely lost at this point. What am I doing wrong here?

Thanks!


texts: A deterministic way to determine states of ideal diodes

texts:
How can the states of ideal diodes be determined in simple circuits with only DC sources and resistors without a trial and error approach?

I have been told to use a technique known as analysis by assumed states of ideal diodes which assumes a set of of states of the diodes (ON/OFF), then we proceed by checking if there is an inconsistency with our assumptions (like current flowing from a reverse biased diode or having a higher potential at anode than cathode in forward biased diode). I dislike this technique due to the following reasons:

Counter examples can disprove a result but there is no such thing as proof by example. I don't see a justification of the current moving in assumed directions at all.
This technique does not show the uniqueness of solution.
This is exhaustive enumeration, with \$n\$ diodes we may have to check \$2^n\$ cases in the worst case scenario (worst still if you come to the conclusion that no solution exists!).

So, is there a better way (preferably deterministic) to solve such circuits?


texts: Can't reflash esp8266 - 12E after many attemptions

texts: I have the following circuit for updating custom firmware to my esp8266-12e module. I've tried many variations for GPIO0, GPIO2, but none of them works. I use the Arduino IDE to make hex files, and then I upload the binary using esptool.py with the following command: python esptool.py --baud 115200 -p /dev/cu.SLAB_USBtoUART write_flash 0x00 /Users/blahblah/Documents/ArduinoBinary/WiFiWebServer.cpp.bin


texts: How to fix dc 12 led lights that burn out due to excess voltage or current

texts:
How to limit the output DC voltage to dc 12V if the input voltage is greater than DC 12v,  and it outputs same voltage if voltage is below 12 V like 11.5 V or 10.5 V?

Scenario:

I have solar setup at home in which pwm 12 V solar charge controller is installed and 180 amp tall tubular battery is installed. I am running this setup to power my 12 V led lights and 12 V DC fans.

Problem is during the day time when sun is present my led lights burns out and that is probably due to excess voltage if i'm not wrong. Sometimes led lights flicker and they burn out.

So I am thinking to add 7812 IC to limit output voltage at 12 V, but I am afraid if my battery is drained out and it provide less than dc 12V, will this 7812 IC work properly?

Or, what should I add to limit the output voltage to DC 12 V if the input voltage is greater than that and it outputs same voltage if voltage is below 12 V?

Edit:
Dc fan probably consumes 3 to 4amps
and dc lights vary from 1amp to 2amp


texts:
I've built a custom board with an Atmega32u4, like the Arduino Pro Micro from Sparkfun.

The circuit seems ok, but when I plug the board to a pc, the usb device isn't recognize (doesn't even pop the "Installing device driver software" bubble).

I'm missing something?
Doesn't the Atmega32 ship with a base firmware installed?

update:

The problem is: using only the internal oscillator, should the MCU be recognized as an USB device when plugged to a computer? If not, what is needed to do that?


texts: Implement boolean function with given components

texts:
I have to implement these functions using the following components only
$$F_1(A,B,C) = AC + BC'$$
$$F_2(A,B,C) = AC + B'C'$$
$$F_3(A,B,C) = A'B + AB'$$
Components given:

1:4 DeMux with active high enable - 1 No.
2:4 Decoder with active low enable - 1 No.
8:3 Encoder with active low enable - 1 No.

I thought of using DeMux as another decoder and use Encoder for taking OR of product terms, but I can't seem to get it.
It would be great if someone could help.
UPD My work:


texts: Pre-biased transistor, what is infinite resistance pull-down resistor

texts:
I am trying to select a pre-biased transistor, and I noticed some of them have a what is listed as an infinite resistance base pull-down resistor.

I do not understand how or why an infinite resistance base pull-down resistor works, and if this has an advantage or disadvantage over lets say a normal 10K pull-down resistor.

Thank you for the help.

Screenshot from a datasheet:


texts: Reading Multiple ADC channels with a PIC18F24K22

texts:
I am having issues with reading 2 ADC channels in my code running in a PIC18F24K22.
One channel is used to read a potentiometer to control the speed of a motor ( PWM) and the other is reading a temperature sensor. They work fine individually but when I try to read both it does not seem to be working properly.  As I increase the duty cycle with the Pot something goes wrong, my motor starts making funny noises, however if I only use one ADC channel the motor is fine. Here is my code in brief:
while (1){
   unsigned char store = ADCRead();  // first function call (PWM)
   CCPR5L= store;
   float temperature= ADCRead1();     // second function call
   if (temperature>30)
   {
     LATC=0;
   }
   else
   {
     ;;
   }
 }

//Functions
unsigned char ADCRead()
{
  ADCON0&=0b00000011;   // clear channel
  ADCON2bits.ADFM=0;  // left justified
  ADCON0bits.CHS=0b00100;// select channel
  ADCON2bits.ACQT=0b100;//Acquisition time to charge hold capacitor 8Tad
  ADCON0bits.GO=1; // Start conversion
  while (ADCON0bits.GO_nDONE)
  {
  }
  return ADRESH;
}

float ADCRead1()
{
  ADCON0&=0b00000011; // clear channel
  ADCON2bits.ADFM=1;  // right justified
  ADCON0bits.CHS=0b10000;// select channel
  ADCON2bits.ACQT=0b100;//Acquisition time to charge hold capacitor 8Tad
  ADCON0bits.GO=1; // Start conversion
  while (ADCON0bits.GO_nDONE)
  {
  }
  uint16_t value = (ADRESH<<8)+ADRESL;
  float vo= value*0.00488;
  float temp = vo/0.01;
  return temp;
}


texts: Is this matrix-vector multiplication function in VHDL parallelized?

texts:
I have the following VHDL function that multiples a given mxn matrix a by a nx1 vector b:

function matrix_multiply_by_vector(a: integer_matrix; b: integer_vector; m: integer; n: integer)
return integer_vector is variable c : integer_vector(m-1 downto 0) := (others => 0);
begin
    for i in 0 to m-1 loop
        for j in 0 to n-1 loop
            c(i) := c(i) + (a(i,j) * b(j));
        end loop;
    end loop;
    return c;
end matrix_multiply_by_vector;

It works well but what does this actually implement in hardware? Specifically, what I want to know is if it is smart enough to realize that it can parallelize the inner for loop, essentially computing a dot product for each row of the matrix. If not, what is the simplest (i.e. nice syntax) way to parallelize matrix-vector multiplication?


texts: voltage to current converter using op-amp and MOS

texts:
I came across voltage to current (V2I) converter circuit. and I found Iout=Vin/R1. I have a few questions about it:

I believe the op-amp is in the negative configuration because v(3) & v(2) both increase or decrease at the same time to make it negative stable feedback. If Vin increases, temporarily v(3) >v(2), thus output v(1) increases and lets NMOS to conduct more current, having higher I1 current than initial current across it, thus V(R1) increases and hence v(2) increases making it stable.

Intuitive, what is the output voltage of op-amp v(1)? if we have given LF sine wave at Vin? (I believe it'll be sine).

In which region does MOS operate? Is it linear? because we want Current to linearly follow Vgs. What I see is v(1) ~ v(R1) implies Vgs is almost 0, how does MOS even conduct and provide the required Iout=Vin/R1

If a capacitor C1 is placed in parallel with R1, we get a kind of LPF with a resistive divider(Ignore the name R1,R2 in the figure)

where phase angle lags by 90 degrees at Higher frequencies, thus creating a possibility of instability(considering non-ideal op-amp also lags the phase), so we add a compensation circuit. How can I add a compensation network? How about attaching a phase lead compensator at v(1)? I think it won't be helpful since gate voltage would decrease in LF operation. But if it is so, how NMOS will allow the Iout amount of current?


texts:
I have the following circuit:

simulate this circuit – Schematic created using CircuitLab

If I choose clockwise current direction then KVL gives me:
$$10\text{V}+5\text{k}\Omega \times I-0.7=0 \rightarrow I=-1.86\text{mA}$$
If I choose counter clockwise current direction KVL gives me:
$$-10\text{V}+5\text{k}\Omega \times I+0.7=0 \rightarrow I=+1.86\text{mA}$$

I want to ask if I am doing something wrong or the negative current in the first case is because the assumed current direction is backwards to the actual flow?


texts: How do I properly clean oscilloscope BNC connectors?

texts:
Over time with use BNC connectors on test equipment will attract contaminants . Since BNC is usually used for relatively high frequencies, I suspect that contaminants will have negatively affect performance of the system.

I also suspect that type of cleaning agent can affect performance of the system.

So my question is: How to properly clean a BNC connector without affecting its performance in a negative way?


texts: The fields and waves associated with a transformer

texts:
Induction in a transformer happens via a fluctuating magnetic field in coil A inducing a voltage and hence current in coil B.

An electric field is associated with a fluctuating magnetic field. Is the electric field at right angles to the magnetic flux lines?
Is this magnetic field actually an electromagnetic wave? What part, if any, do electromagnetic waves/fields have in the operation of a transformer? Do electromagnetic waves travel down the wire?


texts: What were gate length of early SSI circuits?

texts: Just curious about early IC history. Wikipedia tells about IC nodes starting with 10 micron, but I'm curious what people produced before that, in 1960s.


texts: How to calcuate base resistance from BJT circuit?

texts:
How do I approach this question?

My attempt:

$$I_{C} = 1mA$$

$$I_{B} = \frac {I_{C}} {\beta} $$

$$10 - I_{B}R_{B} - 0.7 = 0 $$

$$R_{B} = \frac{\beta (10 - 0.7)}{I_{C}}$$

$$R_{B} = 930 k\Omega$$

The answer should be \$R_{B} = 186.3 k\Omega\$


texts: How to get started with battery replacement in a bluetooth speaker?

texts:
I have a bluetooth speaker with a faulty battery (this model). I'd like to replace it but I have very limited experience with this kind of repair work. To get started, I'd like to

identify what type of replacement I need,
identify what kind of tools I'll need to use.

As for point 1. my issue is that I'm not sure what to look for when replacing a battery. What specs are important here?

As for point 2. I intend to get an antistatic wristband and a mat to make sure I don't zap anything in the speaker, but I'm not totally sure I need it. Do I need antistatic protection in this case? Also, I'm not sure whether soldering might be required. Is it likely that I'll need to solder stuff?


texts: Is 3 bytes a min to address a register in a 256K EEPROM?

texts:
I am really new to electronics and embeds and I am struggling with some probably basic notions. (I have a software background.)

I have an EEPROM (24LC256) connected to an MBED microcontroller and I want to write to it. The EEPROM device uses the I2C protocol. I have a working example that I got here.

However I am puzzled about many things and the first one is about registers/memory and minimum bytes needed to send for an operation.

My reasoning

This device is 256K == 256000 bits. This implies that to access a single register in the memory we need 18 bits since the first register is 00000000 00000000 00000000 and the last is 11111111 11111111 11111111.

My questions

First of all, is my reasoning correct?
Does all this mean that every time I want to read or write I have to send a minimum of 3 bytes?
Is this a thing that applies generally to all devices?


texts:
I'm designing a battery charger PCB using a LTM8062 2A battery charger IC. I'm going to use it to charge a 14.4v battery and I would like to have an indicator LED to let you know when it's done charging. The IC has an active low CHG pin for this purpose. However, the datasheet says:    "Open-Collector Charger Status Output: typically pulled up through a resistor to a reference voltage. This status pin can be pulled up to voltages as high as Vin and can sink currents up to 10mA. During a battery charge cycle, this pin is pulled low. When the charge current falls below C/10, the pin becomes high impedance."

My question is, how can I hook up an LED that only turns on when the pin goes to high-impedance? (I'm assuming high-impedance means the pin is left floating) I'm thinking of using a PNP transistor, with the base hooked to the CHG pin, which also gets pulled to ground. The LED is hooked up to the collector end, and the emitter is just hooked up to the voltage source. Is this the correct way to do this?


texts: How does range affect Xbee's power consumption?

texts:
I am using Xbee ZB SMT in a module, with a microcontroler and sensor, all powered by a battery.
Are there any studies on how range affects the power consumption of the Xbee module?
And as I would very much like to do some tests myself, I would appreciate any tips.

Thanks in advance


texts: Can You Drive Back-To-Back MOSFETs (aka a Solid State Relay) Without Using An Optocoupler?

texts:
I was wondering if there was any way of driving back-to-back MOSFETs (with their sources and gates tied together as shown in the following image) without using an optocoupler?

The reason is that optocouplers are slow, I want to use a SSR to short out a ultrasound transducer after sending a transmit pulse-train to shorten the ring time (to get the receiver set-up quicker to measure shorter distances).

Assuming N-Channel MOSFETs, I can't think of a way of biasing the gate to say +5V relative to the source (which is changing all the time), without using an isolation technique like optocouplers or a transformer.

Is there a simple way to do this if you don't require isolation?

I intend to drive the transducer with something like shown below, where Cp and Rl models the piezo-electric transducer, and Cl/transformer is to make the load purely "resistive" and then match the impedance.