texts:
I need some help with component instantiations (port maps) in VHDL. I have a 16 bit Full Adder which I want to import in my ALU, and it should trigger when the opcode turns "000". In the following code I have, Sum and Carry are going undefined after using the testbench. I took help from here to implement the port map. Maybe I'm not using the test bench correctly here.

FullAdder16Bit.vhd:

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.std_logic_arith.all;

entity FullAdder16Bit is
    port(A,B: in std_logic_vector(15 downto 0);
        Cin: in std_logic;
        Sum: out std_logic_vector(15 downto 0);
        Cout: out std_logic);
end FullAdder16Bit;

architecture behavior of FullAdder16Bit is

begin
    process(A,B,Cin)
    variable carry: std_logic;

    begin
    carry:=Cin;
        for i in 0 to 15 loop
        carry:=(A(i) and B(i)) or (carry and (A(i) or B(i)));
        end loop;
    sum<=A + B + Cin;
    Cout<=carry;
    end process;
end behavior;

ALU16Bit.vhd:

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
entity arith is
port(A,B: in std_logic_vector(15 downto 0);
    opcode: in std_logic_vector(2 downto 0);
    Sum: out std_logic_vector(15 downto 0);
    Carry: out std_logic;
    mult: buffer std_logic_vector(31 downto 0));
end arith;
architecture rtl of arith is
component FullAdder16Bit is
    port(A,B: in std_logic_vector(15 downto 0);
        Cin: in std_logic;
        Sum: out std_logic_vector(15 downto 0);
        Cout: out std_logic);
end component;
signal areg,breg,sreg:std_logic_vector(15 downto 0);
signal cinreg,coutreg:std_logic;
begin
Add: FullAdder16Bit port map(A=>A,B=>B,Cin=>'0',Sum=>Sum,Cout=>Carry);
process(A,B,opcode)
begin
Sum<=(others=>'0');
Carry<='0';
mult<=(others=>'0');
case opcode is
when "000" =>
areg<=A; breg<=b;cinreg<='0'; Sum<=sreg; Carry<=coutreg;
when others =>
Sum<=(others=>'Z');
Carry<='Z';
mult<=(others=>'Z');
end case;
end process;
end rtl;

tb_ALU16Bit.vhd:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
entity tb_arith is
end tb_arith;
architecture structure of tb_arith is
component arith is
port(A,B: in std_logic_vector(15 downto 0);
    opcode: in std_logic_vector(2 downto 0);
    Sum: out std_logic_vector(15 downto 0);
    Carry: out std_logic;
    mult: buffer std_logic_vector(31 downto 0));
end component;
signal A,B,Sum: std_logic_vector(15 downto 0);
signal Carry: std_logic;
signal opcode: std_logic_vector(2 downto 0);
signal mult: std_logic_vector(31 downto 0);
begin
DUT: arith port map(A,B,opcode,Sum,Carry,mult);
process
begin
wait for 0 ns;
opcode<="000";
A<="0000111111111111";
B<="1111111111111111";
wait for 10 ns;
opcode<="001";
A<="0000111111111111";
B<="1111111111111111";
wait;
end process;
end structure;
configuration tb_arith_con of tb_arith is
for structure
end for;
end tb_arith_con;


texts:
There  are two  type pwm signals, one pwm with 2.5khz 50% duty, second type 5khz 50% duty.  I am looking  solution  how to detect   2.5khz  as digital 1 and 5khz as 0, or  2.5khz-0, 5khz-1.   The signal will be detect using arduino, but I don't want to use pulsein  or other solution which detect length of signal.

incorrect sample deleted


texts:
In my circuit (picture below), ATMEGA32 output is connected to a RC filter (R=100K, C=10uF 63V) to non-inverting terminal of OpAmp (LT1006). OpAmp is configured as voltage follower (Buffer Amplifier). Voltage in non-inverting terminal varies (0 to 5 V) by changing values in OCR1 register of ATmega32.

Theoretically, in a buffer amplifier configuration, output will be the same with respect to input of an OpAmp but in this case the output go high rather than input (eg: input=1.45 V, output=2.68 V).

I connected different voltage from other source to non-inverting terminal output will be the same so the mistake is happening while connecting via RC filter.

Would anyone kindly give any solution for this?


texts: How to reconnect to potential of ripped off solder pad without visible circuit traces

texts:
I am trying to get a data backup from a broken LG/Google Nexus 5 smartphone. It was repeating in a boot loop, because the on-switch was stuck at always on.
I dismantled the mainboard. Here is a overview:

After desoldering the little push button (from the sport marked with the arrow) I soldered two wires to the contacts the switch was shorting, to make a provisory switch. Then I reassembled the phone partially, to get it started.

While doing so I unfortunately pulled to much on one wire and ripped it off the PCB with the solder pad. Annoyingly it was not one of the four pads which are connected to the ground plane, but the "signal contact" which probably only has a narrow connection path to some controller pin.

As I can see on this microscope images, there is no conductive track leaving my broken signal pad on the top layer of the PCB. It is isolated all-around against the ground plane. So it must be connected by a "via in pad". Is that correct?

I already tried to cover the broken pad with tin by making a solder bridge between the neighboring ground pads, without success. But after the heating it gave me a better view on the underground of the broken pad.

There seems to be an outer and an inner conductive plane, the inner one with an little golden point in it. Is that the via-in-pad?

I also tried to short the connection by a wire with an alligator clamp on ground on the one side and a multimeter probe on the other side. With the probe I tried to touch the via. I had no success in switching on the phone by this method.

Is the inner circular area with the golden point my target potential which I have to pull on ground?

With what technique can I expose that area? Scratching?
Are there some other spots on the PCB where I could search for my target potential?
Is there an other way to get a data backup of the flash memory?

Thank you in advance!

Edit: You can find some close up photographies of the switch here: http://runawaybrainz.blogspot.com/2015/05/google-nexus-5-power-button-woes.html


texts:
I want to protect a pin with an opto isolator to get an external signal from an electrical meter (35VDC max, 50mA max, 240ms pulse width). The purpose is to count the pulses.

Do you have some schematics examples for that ?

Thanks


texts: Can I use android phone for arm development?

texts:
Android phones are mostly run over ARM processors. In Pakistan purchasing an ARM development board is very difficult and almost not available. Importing from other country cost it a lot.
On the other hand Android phones are very cheap as for just 25$ to 30$ so I was wondering can we use android phones as ARM Development like? If so, then Is there any starting point available over web? I searched google but did not find any useful information. Any body have experienced it before? please share
thanks


texts: What can I do to get a stable bias on this current sink?

texts:
I am still working on trying to get a stable 60 Hz ramp generator with a down-slope, and I am trying to do it from first principles and as simple as possible to understand fully what I'm doing.
I got myself 2N7000 MOSFETs and found they are perfect to drive high currents fast with TTL input on the gate. Nice way to discharge, or charge the capacitor rapidly. So I combined that MOSFET as a rapid charger with a NPN current sink to slowly discharge the capacitor.

My problem is this only works in theory, because in practice the biasing of the base with the R2 = 10k and R3 = 1k is incredibly fickle. If I use R3 = 1.1k or R3 = 0.9k the behavior is vastly different. So I know already that I won't get a stable ramp in practice, and I am stuck on this for weeks now. I have a perfectly fine 150 kHz ramp, smooth and stable. But the 60 Hz ramp I cannot get clean for the life of me.
I noticed in this simulation that I need that base to be at about 0.5 V, so it's just too little to do with a diode. If it could do with 0.7 V, then I could replace the 1k with a diode and be more stable I think. But I need 0.5V. What can I do?
I also noticed that the R1 and R4 and also the C1 don't really help me all too much with the tweaking. And I don't want to make C1 much bigger in order to cut down on the charge time, I need that to complete in 6 microseconds, but ideally less.
How about this here, can't quite find my simple standard diodes in the LTspice repertoire but I grabbed the switching diode with the lowest voltage as one that should probably do it.

This approach looks like it is more graceful given the tolerance on R2 and R3 variations, but I am a bit surprised by these very high values of 5 and 2 mega-ohm. Does this make sense at all?
The simulation looks nice, and with 630 mA peak on the capacitor charge, it looks practically doable.

Did I just answer my own question again? In this second schematic, if I vary those resistor values, I still get the ramp fairly stable. So I suppose I will try this. But comments or better ideas are much appreciated.
Notably I tried to use a JFET as a current sink but there I had an even bigger problem biasing the gate. So I gave up.
PS: yes I know I throw in a 100 nF bypass capacitor also so that I can serve the momentary 630 mA current draw with ease.


texts: Comparison between the same signal from different sensors

texts:
If I have PPG (plethysmograph) signals from sensors that are positioned in different locations along with their corresponding power spectrums, how to determine systematically and accurately the best signal? 'Best': one that resembles the actual PPG signal and less noisy.
Thanks


texts: Negative differential resistance on current sink

texts:
Let's assume we have this circuit:

simulate this circuit – Schematic created using CircuitLab
I was looking in creating a costant current sink but I have found something very interesting. Assuming V1> Vzn(D1) if we increase V1 we increase the voltage at the base of the NPN and PNP transistor ( a little bit) ->Ie(NPN) is increased and Ie(PNP) is decreased. However the R6 resistor sees the current flowing through the collector of the NPN transistor and the current flowing through the emitter of the PNP transistor.However the emitter current current > collector current so it sees less current with increase of V1?Negative differential resistance or what?


texts:
I've routed plenty of through-hole boards, but I have no experience with SMD routing techniques, and even the look of the board feels a bit ‘alien’ to me.

Any tips for placing/routing prototype PCBs with SMD components, for someone who can already route with through-hole components? I'll be hand-soldering as well, so I'm sticking to SOIC, 1206, and the like.

Ideally, I'd like tips on how to place for reasonable density, whether to use one or both sides of the board for components, etc.


texts: Not understanding aspects of the LM386 amp

texts:
For the following LM386 amp i have a couple of questions.

Is C3 and R1 a low pass filter and if so how do i calculate the cutoff frequency for it? I.e. do i have to take the impedance of C2 into consideration?
What does the capacitor C2 do. When diagram one states that it removes the dc component, is this like it removing the bias? Also C2 with R1 and C3 make a high pass filter doesnt it? If so how do i calculate the cutoff frequency for it?
For the input voltage into the amp, say if it was a square wave from 0-5V, doesnt a high pass capacitor have to be used to remove the dc bias with a voltage divider so that Vin is 0.4 to -0.4v? If this high pass filter is used to remove the dc bias is C2 needed then? Diagram 3 shows this dc bias remover.
If the speaker has a max power of 0.25W and a resistance of 8ohms, does this mean i need a 1.41 V output from the amp (V=sqrt(PR))
If i need a lowpass filter that removes say 15Khz as the cutoff frequency can i just change the values of C3 and R1 to get this cutoff?

Thanks for helping in advance

Note 1st diagram is just something i found online stating what potentially each C2 etc is.

Datasheet for LM386: http://www.ti.com/lit/ds/symlink/lm386.pdf


texts: Is there any way to wind this 4 pole motor to behave as 2 or 8 poles properly?

texts:
I got an induction motor in a junkyard, a WEG motor made for an Electrolux washing machine.
It is a single-phase 1/2 hp 4 pole motor. It runs in 127 V and has a 40 uf capacitor feeding the auxiliary winding.
Here's a photo of an identical one I found on the internet (mine is currently disassembled):

Its winding can be divided into 2 sets of 4 units each: The set of inner windings (green in the picture below) and the set of outer windings (red in the picture below).

After several tests I could assure it was what It looked from visual inspection, a concentric winding scheme where each unit looks like this:

Furthermore, I found out the 4 outer units are wound with two wires in parallel, having the same number of turns and inductance of the inner ones, but half the DC resistance.
In each set (inner and outer) there are 2 units wound clockwise and 2 units wound counter-clockwise, interleaved.
The stator has 32 slots, so the overall winding looks like this:

It originally came with these connections:
A'—B ; B'—C ; C'—D ; D'—1 ; 1'—2 ; 2'—3 ; 3'—4
The capacitor was connected between A and 4', and the electrical network was connected between 1 and A or between 1 and 4' (for the two directions of rotation).
So, now that you know the motor,
My question is:
Is there a way to reconnect this to create a decent 2 pole or 8 pole motor?
Does the fact it's a concentric winding brings this any special properties?
I'm asking this because I couldn't manage to connect the units in any way that produces a viable 2 pole or 8 pole field.
The first thing I tried was undoing all the original connections, connecting only A'—C' and the electrical network to A and C. That should make an oscillating 2 pole field (not a rotating one), starting it manually should do.
But it didn't. Besides the immense current this draw (around 20 A), it would only accelerate to a rotation like 800 RPM and no further. It also sounded like it had a terribly uneven torque.
Remember those outer units were wound with two wires in parallel, so I changed that to series and tried again. Now I had less insane currents but no luck getting it to run at anything around 3600 rpm.
I tried several other configurations, also using the inner windings together to try to create a 2 pole field. I tried many possibilities but the closest I got was a very strange behavior, while using an auxiliary winding set fed with a 10 uf capacitor, where it would first accelerate to ~1800 rpm and then jump to ~3600 rpm by itself. All of that while drawing ridiculous currents, always over 15 A.
I had a different luck with 8 poles, cause it would actually run at ~ 800 rpm, but again presented ridiculous currents, didn't have a decent torque and I couldn't avoid ridiculous currents.
Anyway, I'm not understanding how it can be failing even to make a 2 pole oscillating field. It looks like it's somehow producing additional poles.
Could the radial motion of the current in the concentric winding (from the outer turns to the inner turns and vice-versa) play any role in this?
Thanks!


texts:
simulate this circuit – Schematic created using CircuitLab

I know at the output side of the buck converter there is a resistor which makes a path to flow current as capacitor doesn't pass current.My questions are:

Besides this is there is any other purpose of this output resistor?
What does actually power rating mean in buck converter? How output resistor contribute in power rating?
Besides this resistor what kind of load is used in buck converters output port? Can inductive load be used in the output port?


texts: Why overflows are omitted in the non-restoring hardware binary division algorithm?


texts: Is additional filter required for MCU analog domain when using DCDC and linear regulator?

texts:
I'm building a device using STM32F0 MCU.

The whole unit is powered with +24V DC delivered via pretty long cables.

This voltage is passed to the DCDC converter, based on RT8259:

In the next step 5V is lowered to 3.3V with simple linear regulator (AMS1117-3.3):

This voltage is used to power the MCU (with additional tantalum 4.7uF and ceramic 100nF per pin).

However the microcontroller has a dedicated "VDDA" pin, which according to datasheet is used as input for PLL, ADC etc.

Is it required to add additional filter for VDDA?
Is LC (10uH + 4.7uF) enough?
If the filter is not present, what would happen? Loss of ADC accuracy (how much?) Loss of clock stability?


texts: How to estimate derivative of state in state-space model?

texts:
I would like to know what would be the best way to estimate a derivative of state of state-space model. I one would like to estimate one of the state, then the Kalman filter should work just fine. However, if the state of interest is not one of the state, what could be done?
Let's say there is a A,B,C,D state-space model of a falling object with some vertical forces, F1, F2 and positional sensor y. Say F1 is known input and F2 is an unknown but significant disturbance. I guess the most common state-space model would be;
$$\begin{matrix} \dot{x} \\ \ddot{x} \end{matrix} = \begin{matrix} 0 & 1 \\ 0 & 0 \end{matrix} *\begin{matrix} x \\ \dot{x} \end{matrix} + \begin{matrix} 0 & 0 & 0\\ 1/m & 1/m & -1 \end{matrix}*\begin{matrix} F1 \\ F2 \\ g\end{matrix}$$
$$\begin{matrix} y \end{matrix} = \begin{matrix} 1& 0 \end{matrix}*\begin{matrix} x \\\dot{x} \end{matrix} + O *\begin{matrix} F1 \\ F2 \\ g\end{matrix}$$.
In this example, how could one estimate $$ \ddot{x} $$?
Should one expand the state vector so that the Kalman filter could be utilized? If so, what would be the A, B, C, D matrix? How about estimate first derivative with the Kalman filter and putting it thru a differentiator? If not, how could it be done?

Considering the other purpose of the controller not mention in the question, expanding the state vector is desirable, if possible.


texts: MOSFET choice for 12v LED Strip and 3.3v Logic

texts:
I'm currently planning a project on a low-cost WiFi-enabled RGB LED
controller and could use some help in looking over my parts list and
general concept.

What I'm wanting to do is a build a relatively low-cost, WiFi-enabled
RGB LED (strip) controller. In the end it should be controlled via an
Android App which is already being developed in my free time.
For the WiFi module I want to use the infamous ESP8266 board, namely an
ESP-07.

We are talking about normal, RGB, LED Strips (5050 SMD in my case) - nothing fancy.

The plan is to flash it with nodemcu firmware (can't provide a link, but googling "nodemcu" will show what it is about, but it doesn't really matter for the sake of the question),
write a simple TCP server implementation which allows to manipulate 3
GPIO pins' duty cycle over the network. I have no problems related to
the software or the programming of either the MCU, the App or anything
else. What I'm unsure about are the electronics involved here. I've come
to understand that I want to use transistors or MOSFETs to drive the LED
Strips 12v using the 3.3v logic of the ESP8266. From what I know, I
should choose a FET that can be switched fast (requirement for PWM) and
has a maximum gate threshold voltage below 3.3 Volts.
Based on these requirements and the availability at my supplier I've
chosen the IRFZ44N
and I want
to wire it directly to the three GPIO outputs of the Microcontroller.

Is
there any reason for this being a bad idea? Should I maybe add a diode?
I don't think so since LEDs are resistive load and not inductive (so
there shouldn't be voltage spikes or any of the likes, but I'm a layman
when it comes to electronics, far more involved in programming..)
Please tell me if there are any pitfalls to this plan and thank you for
taking the time to read through my plan.


texts:
I made a 170V step up converter using a 555 timer for my Nixi project.

At first I tried to run it using 5v but could not reach a 170v output, so I opted for a 12V supply and put in an LM7809 regulator. I put a heatsink on it although it probably does not need one.
I was able to get 170V but found that this would change if I varied the input voltage (bypassing the 9V regulator that is)
But the main issue is that the voltage drops if I connect a load.

No load: I/P = 12V @ 100mA; O/P = 170V @ 0mA

1 neon load: I/P = 12V @ 200mA; O/P = 148V @ 0.82mA

2 neon load: I/P = 12V @ 200mA; O/P = 133V @ 1.3mA

Testing with 1 neon load:
By adjusting the variable resistor I can reduce the voltage, but cannot get it above 148V. It is as if my circuit is reaching saturation.
I had triggering issues on my scope but noticed that the square wave did change from no load to 1 neon load, but adding the 2nd neon did not "seem" to make a difference.

I checked the electrolytics = ok.
Coil = 100uH.
The 1k & 2K2 resistors were swapped around, but that made no difference.
I even replaced the 555.
I may have used an IN4004 diode instead of a UF4004 - is there a difference?
Checked for shorts, parts placement,.......

I did order a ready made supply which is currently on a slow boat from China, but would prefer to use my own build anyway. Although I did get the schematic off the net.
Any ideas where I failed or what I else I could test for?
Any help would be appreciated.

Thank you

Thank you for the feedback.

I will try to answer as many quetions as I can.

Neon tubes don't use much current, so I should be ok with the 12V 2A supply I intend to use. (tetsted with 4A bench supply)

Why a 555? Probably because I'm a bit nostalgic about these and because I had quite a few lying around.

(@Finbarr) I originally put in a 9V regulator because the output voltage would vary with the input voltage and I wanted a stable output.
If this issue is resolved once I get the circuit going, then I will remove it. I want to protect my precious Nixi tubes just in case I (or someone else) plugs in the wrong power supply.  And then I read your next reply about the input voltage varying the frequency and duty cycle, so it looks like the 9v regualtor stays.

I used a 350V rated cap on the output.

I remember that component prfixes used to be manufacture specific, so TI would have a different prefix than Fairchild......

But I started to think about the diode more and more. Thank you for confirming this and I will pop off to the local elecronics supplier and pick up a UF4004. Fingers crossed!


texts: Hardware needs for minimal DVI processing with precise timing requirements

texts:
I'm looking to make something I can put between a video/audio source (DVI/DP) and a 240hz monitor that can, with precise timing, replace single frames with a solid color. (the application is around device testing and calibration and could be used with monitors that support other refresh rates)

So, say, every 100th (1/240)s long frames should display a solid red frame, but otherwise pass through the video/audio stream we're receiving during the rest of the time.

Are microprocessors sufficient for this application? An FPGA board feels overboard, but I'm unsure. Do you have any recommendations? What about if I wanted to modify the color of every pixel slightly in an independent way (increasing brightness, say), to help with calibration?

Thanks for pointing me in the right direction, most advice I've seen has been focused on more complicated processing requirements and I'm trying to avoid implementation complexity if possible.


texts:
I have never used an H-bridge before, but now I want to toy around. Reading this document the author uses IR2110 (Datasheet) with IRF840 (Datasheet IRF840), and these datasheets will be my starting point.

Questions for the driver:

Datasheets mentions Io as 2A, and defines as "Output short circuit pulsed current". Is this the maximum value for when there is an error in the H-bridge, for example if I accidentally open Q1/Q2 (left side) at the same time? If not, what is it?
Figure 26B (page 13) shows "Output source current vs. Voltage", and 3.5A typical at 2V. As a MOSFET-gate has a lot of resistance the current will not go into there, so where's this 3.5A of current going?
"Feature: undervoltage lockout for both channels". What does that mean? (The datasheet is incredibly scarce regarding information)
The datasheet does not mention any typical values, or anything, regarding the bootstrap capacitor and diode. How do I know what values I should use?

Questions for the MOSFETs:

Id (drain current) is set to 8A according to the datasheet. If my load, after the H-bridge, is supposed to sink 1A current continuously, is parameter Id the one I should in particular keep my eye on? (I know there's a lot of variables involved, but I want to keep it simple just to get the hang of it)
I'm having a struggle interpreting the charts. What I want to find out is how hot the MOSFETs will be in in the H-bridge, when supplying 9V / 1A to my load, so I know get a ballpark value for the heatsink. Which chart in the datasheet is the one I should look at?

General questions for driver + MOSFET:

There's a lot of MOSFETs and a lot of different drivers. Basically, what parameters do I need to lookup in the datasheets to find if driver + transistors are "compatible" (so to speak) in my future H-bridge?
Hypothetically, let's say my load would sink 15A current. Will these 15A come from the MOSFETs only, or will any of it come from the driver as well? Put in other words; if I in the future need to replace the MOSFETs to more tougher ones (more amps), do I also need to redesign the circuit and replace the driver as well?


texts: Why not always use DMA in favor of interrupts with UART on STM32?

texts:
I spend last month a lot of time getting UART (for MIDI) to work with an STM (STM32F103C8T6) using interrupts, without very much success.

However, this evening using DMA it worked quite fast.

Since as far as I read DMA is faster and relieves the CPU, why not always use DMA in favor of interrupts? Especially since on the STM32 there seem to be quite some problems.

I'm using STM32CubeMx/HAL.


texts:
I was doing this circuit which I found on the Internet. My question is what is the logic behind the functioning of this circuit?
Thanks!


texts: Why pulsed DC passes through a capacitor?

texts:
OK, the current flowing through a capacitor equals C*dV/dt, I'm aware of that. What I don't understand is the physics of the process: why does a capacitor pass pulsed DC (0-10V for example) when charge carriers don't change their direction?

Even if I use the "water analogy" it doesn't make sense: the flow moves in one direction, so the "diaphragm" will not be able to move back and forth.


texts: What would be the difference in using a 7-segment decoder with active-high outputs vs active-low outputs, to driver an LED display?


texts:
I am trying to send a signal from the Arduino to a relay to open a switch. My problem is that my Arduino will be near the AC power lines.

I searched for how to prevent the noise to ruin the signal but every site and article was talking about how to secure the input data to my Arduino BUT my case is different as I am trying to send the signal from the Arduino to a relay.

How do I prevent the noise if there is any judging by the location of the Arduino ?


texts: How to hook up an Arduino Uno to serial and ethernet

texts:
I've got an Arduino Uno and I'm relatively new to electronics / I'd like to connect it to a serial receipt printer and an ethernet switch. For all the research that I've done, I've found a number of serial and ethernet shields, but I'm not sure if I can use them both together.

Any help would be greatly appreciated.


texts: Must film capacitors be derated according to the voltage applied?

texts:
I know electrolytic capacitors must be derated according to the applied voltage, with some losing a significant part of their nominal value at high voltages.

Is it a similar case with film capacitors? I am using these TDK 1uF film capacitors . Will be applying 400Vdc on these.

I did try looking it up, I could not find a clear answer.


texts: Why are tv aerial cables so mysteriously sensitive to their positioning and the proximity of people?

texts:
Digital TV Reception is not great in our area and sometimes we lose reception when conditions aren't favourable.  Being UK Freeview, I'm pretty sure it uses the DVB-T2 standard.

Anyway, when reception is poor, varying the position in which the (RF Coaxial) cable running from the wall to the receiver is draped improves or worsens reception.  Also, when you set it in a working position, as you move away it may mysteriously then stop working.  Surely this defies science, but everybody else must have experienced the same thing?

Anyway, the socket has been replaced, the connections are certainly excellent, we've tried different cables, there are no stray strands within the wall box etc. so the only explanation I can come up with is that the earth or metal components of the wall box pick up signal from surrounding objects, or shielding of the cable is inadequate.  Is there an established wisdom why the setup is sensitive to cable position?

I should mention - not everybody has a cathedral directly between their aerial and the transmitter.  Perhaps this mysterious behaviour is down to some unknown property of his holy lordship.

Just to be clear, I'm not asking how to fix the problem, e.g. by amplifying the  signal at source, although sensible fixes would also be welcome.


texts:
I want to create my own light source using high power 1W LEDs. Can I solder high power 1W LEDS on aluminum with 60/40 solder?

Here's a picture of a potential heatsink


texts: I need help finding the equivalent resistance

texts: Hello guys , i'm new in the amazing world of electronics , and im very confused with this circuit . Im supposed to find the Req (equivalent resistance , but dont know how in this specific circuit),  plz help me out .


texts:
I'm trying to build a device that alerts me when I leave home without locking the door. I have a little space inside the door (width 8mm x height 130mm x depth 8mm) where I plan to install the microcontroller, a small button that gets pressed when the piece of metal of the door slides in (door locked), a battery and a rf transmitter.

The questions are:

push buttons can detect the pushed/unpushed state of the button, or they simply give me a single "one-time" signal when the button is pressed ?
do you think the space available is enough for this project ?


texts:
I am in first year of Engineering school and I was given an assignment which contains this circuit which drives pressure sensors in a pitot tube :

For training, I am trying to reproduce it using the gEDA free software, but I came accross those little beasts named A1 and A2 I can't reproduce.

What are they ?

[as an aside, does anyone have an idea about which piece of software could have produced this image ? ]


texts: KiCAD: addting a micro via to a footprint

texts: I need to make a footprint in KiCAD that has a micro via. Is this possible? The footprint will sit on a 4-layer board and I need a micro via from F.Cu to In1.Cu.


texts: I wonder which logic technology is STM32F407 MCU based on.. CMOS or TTL or HC or LVT etc? Although its mentioned in the datasheet that the GPIO's are CMOS and TTL compliant. I am concerned about this because I have to interface this 3.3V MCU with other logic circuitry and maybe the different logic families won't work well together.


texts: Do I need a flyback diode with an automotive relay?

texts:
I have two relays to convert +12 volt circuits to "ground" inputs into a fuel injection ECU.
If I connect the relay coil ground to the same ground as the "source" will I need to install a diode to prevent possible fly-back to the ECU?

Here is the diagram:


texts:
I am just wondering what the convention is for putting designators for tightly packed areas. It is best just to put arrows to the designators, make the designator smaller and put it inside the component etc
Here is an example, the R4-R12 are all the resisters below IC1.


texts: What is the white powdery stuff that leaks out of a battery if I accidentally submerge it in water?

texts:
Does it mean that the battery has exploded?

I often see the white powdery stuff when I see "battery disposal" boxes in public areas


texts: Saftey regulations of multiple 1mW lasers

texts: AFAIK devices containing exposed 5mW lasers are illegal without a license, but those containing 1mW lasers are. But how about a device with ten 1mW lasers? Is it still a safe and legal device? The beams could potentially be non-parallel and focus at a single point.


texts:
I am planning to switch the 5V line to a USB load.

I have being going around different suppliers looking for an optocoupler that can handle 3A at 5V. I have seen a few, but upon looking at the datasheet (e.g., FOD3182), they mentioned that the operating voltage should be at 15 to 30V.

If there aren't any such optocouplers, how can I solve my problem?


texts: Varistor - Place before or after the fuse?

texts:
What is safer? Before or after the fuse?
In my case the varistor is 10mm, 275Vrms, and it is currently placed after a 250Vac, 7A, 20mm glass fuse. Would the varistor blow the fuse easily if placed after? I will not say if the fuse is fast or slow action type, you should consider that in practice the fuse will be one of those are selled in any little electronics store, a standard/commom fuse... I don't know if those commom fuses that you find in any electronics store are slow or fast action type...
But anyway, there was a day that I asked myself if there would be any advantage of puting the varistor before the fuse, directly in parallel with the mains, I don't have an answer for that yet.

Regards


texts: Safely removing bonding glue from an IC in order to identify it?

texts: I have an IC, that has 5 visible bonds. The entire IC is covered with some sort of semi transparent bonding glue. I want to identify the IC and were thinking to remove the glue somehow. What chemical compound can be safetly used without damaging the IC or potentially erasing any markers from it?


texts: Multiplexing Inputs on a microcontroller

texts:
I have a 4 way DIL switch that I use to provide input to a microcontroller, and I need to free up a port to use for something else.

Is there a way to multiplex 4 inputs into 3 microcontroller ports? I'm thinking that there may be some way to have 2 pins as inputs, and a 3rd output pin that can be driven high to read switch 1 and 2, and low to read switch 3 and 4.

My current simple design is shown below, can I do this with just 3 pins?


texts: Controlling 12V water pump with NodeMCU – circuit design review

texts:
I'm a programmer who's recently become fascinated by electronics, specifically with microcontrollers and how I could use them for various IoT projects.

For a starting pet project, I'm planning to automate some of the watering in my garden. After a few days of learning, I've come up with the below circuit.

The board I'm using is NodeMCU v3, the image shows an Arduino Uno just because that's what my circuit design software had. I've tried to add notes to explain why I've used a component.

Questions:

Overall, I'd appreciate any feedback. I'd like to know whether I've done anything crazy and/or what I can do to improve/simplify the circuit.
I'm powering the moisture sensor via a digital output pin, so that I could only provide power when I want to take a reading, therefore prolonging the lifetime of the sensor. This is the sensor I'm using. Is that a good idea or is it even going to do that?
I'm powering the board and the pump with a single power supply. Is it okay if I connect the USB cable, to reprogram the controller, while it is all connected? otherwise, what could I do to safely reprogram it while disconnecting as little as possible?


texts:
1.Is this the correct way to control a DC motor using the PWM pins in the MCU?

2.How many PWM output pins do you need if you want to use a driver (ex: H-bridge) for each motor and control the duty cycles?

3.What are the schottky diodes in my schematic for?


texts: Problem with relay current requirement and how to increase current in DC circuit?

texts: What is the minimum current required to run a relay of 5 V (part: RWH-SH-105D). Will the relay run with 5V DC and 0.8mA current (my inputs)? If it does not work, then please suggest methods to run the relay by giving suggestions on increasing current.


texts: Purchasing a Switch - AC vs DC Current Specifications?

texts:
I'm trying to purchase several switches for a DC system with moderately low current (a few amps at 12V). When browsing for switches in parts catalogs (e.g. Mouser and Digikey) there are always separate voltage ratings for AC and DC applications. I understand that AC switches are less expensive because the switching time does not need to be as fast and arcing is less of a concern. There is only one current rating listed and I am not sure if it applies to AC switching, DC switching, or both.

Does this current rating apply to both the rated AC and DC voltages? Is there a good rule-of-thumb for converting between AC and DC voltage/current ratings? What is the highest current I could reasonably expect from a DC switch before moving to a relay?


texts: how to select and change board dimensions in eagle

texts:
I'm trying to edit the dimensions of a board, but I can't seem to select them. The only selected layer is the Dimension layer. It seems that some of the dimensions are locked. How would I unlock them for selection?

The board is from https://github.com/adafruit/Adafruit-Perma-Proto-HAT-PCB


texts:
Does anyone know what type of plug type this is? I am having no luck identifying it so far. The closest I have found are the Kycon KPPX-3P-SR7DI but it only comes in a 3 and 4 pole version and this plug only has two pins?
Any help would be greatly appreciated.


texts: MAX712 charging circuit - diode gets too hot

texts:
I've built a charger for my 7.2v 3000mAh battery using MAX712 IC.
Here is the datasheet:
http://pdfserv.maximintegrated.com/en/ds/1666.pdf
This is the schematic of my charger:

It's almost a schematic from datasheet.
Calculations were done with the help of this excellent article:
https://www.rcgroups.com/forums/showthread.php?527385-Building-the-Perfect-Nickel-Chemistry-Charger-Part-II
Here are my values:

Power source: 15V 3A
Rsense: 0.25Ohm - 4 1Ohm in parallel.

The IC tries to maintain 0.25V across Rsense(R7,R8,R9,R10 in my schematic), so 0.25R gives (0.25V/0.25R = 1A) of fast charge current.
When I plug the battery in and turn the thing on I get 1A flowing to the battery.
The problem I'm getting is that diode D1 (1N5404 rated 3A - schematic says 1N4004, but I've replaced it on the board) and 2N6107 are getting very hot (can't hold a finger on it for more than a few seconds) on both of them (Q1 even has a heatsink).
According to this formula Q1 should dissipate 9W:
(Q1 pwr dissipation) = [ (DC IN) - (min. battery voltage) ] * (max. charge current) = (15 - 6) * 1 = 9W
The article never mentioned that D1 should be very hot, not any other article I've found, which makes me think something is wrong even though battery gets the correct 1A current.
Any ideas why they might be getting too hot? Any other info I can provide?


texts: Which is better for resonant design in terms of capacitor and inductor?

texts:
For the values of resonant elements like  Lm (magnetizing inductance) and Cr (resonant capacitor ) is there a way to know which value is suitable with a specific Fr resonant frequency?
For example, are small values like (Lm= 50e-3, Cr= 840e-3)  normal?
I am interested in a resonance frequency in the area of 80 to 100kHz.


texts: What is the purpose of R1 in this circuit?

texts: By pressing the stop-button once the LED turns off and stays off. But if you remove R1 the LED only stays off if you are pressing the stop-button. Why does R1 affect this?


texts: False Triggering of when Intergration of TI SE555 with Maxim MAX6866 IC

texts:
I am using Maxim MAX 6866UK28D3L+T in my Design with TI SE555 Timer IC , and having some problem of Flase Triggering.

Circuit Explain:- WDI_IO is Drive from Micro controller , which Continuous toggle this pin, when by any reason this pin is not toggle form 200Sec (approx ) then Reset pin is go low for some micro second. this Reset is open Drain output and drive a 555 Timer IC.
So as in normal function Reset of U3 will be high , 555 will not trigger , and out of 555 will be low, that make Q3 off and Q2 On and Drive the SSR1 on.
and whenever WDI no toggle till Watch dog time defined in datasheet ( approx 200 S) then Reset of U3 go low, than trigger the 555 IC, and Out of U8 555 , goes High ( Width is calculated by R35 and C38), that make Q3 on and Q2 offm and make the SSR1 off for this time.

Issue:- Whenever I turn on the Power , 555 got Trigger by somehow.

Trial:- I isolate the both section by removing R36, that time during power on 555 never trigger. so I thought some glitch or noise coming form MAX 6866 IC.

Trial 2:- so Connect R36 and again , I tried to change value and never got success
 Change R34 to 1K
Change C42 to 0.1uf, also tried with 22pF
changeR36 to 1K, also tried with 82 ohms

Any suggestion to prevent power on false trigger.


texts: Stepper Motors that are connected to A4988 drivers shake and miss steps when MCU connected to galvanically isolated relay. What may cause this?

texts:
I have CNC machine that I built as a weekend project, it uses GRBL 1.1 and a custom Atmega328p board that I designed. It is based on the grbl Uno adapter plus the laser capabilities that I added. At the moment I need to turn on and off the Spindle manually. It is a 500W 110V DC motor. However I find it frustrating that I need to turn the motor off manually each time after a machining process is finished.At this point there is no connection between the board and the spindle. So I changed the GRBL skript a little bit according to the comments given  to be able to turn the Spindle_EN pin high and low with G3 and G5 commands. This works and I am able to control a Mechanical Relay with the given schematic as below. Which controls the spindle.

However after this addition the Stepper motors on the Y axis started skipping steps and shaking when the spindle is on, even when there is no load on the spindle. So there is obviously some parasitic effect caused by the addition of the relay. I am guessing some sort of parasitic inductance from the spindle current causes this, which is around 4,5A, but I dont know for sure. The reason for my thinking is beacuse this happens even stronger when the motors change direction, hence my parasitic inductance idea. Any recommendations on where to start testing and probing would be appriciated. If you have an idea on how to solve the issue without having to change the whole setup would be even better. Below is a link to the schematic of the grbl shield I based my board off of.
https://server4.eca.ir/eshop/000/DataSheet/arduino%20cnc%20shield.pdf


texts: Is it a good idea to ground a high voltage DC motor?

texts:
I have an all metal fully enclosed 120VDC motor with the standard red and black wires. The motor will be mounted using screws on a cast iron metal lathe. The motor is powered via a DC speed controller in a grounded metal housing also mounted to the lathe using screws.

For safety, I drilled and tapped the motor's end bell and fixed a ground cable connected to the controller's metal housing.

Is this a good idea, a bad one or an unnecessary one?  Also, I usually test my projects using a GCFI and I wonder if there is any possibility of inducing a current in the ground wire which can trip it. It shouldn't, as the ground is an incomplete circuit, but I thought I should ask anyway.


texts: How do power companies regulate power plant's voltage output?

texts:
Whether it be a thermal power station or nuclear power station or a hydroelectric damn its impossible to keep all the dynamos running at a fixed speed.

As such how do power companies regulate the voltage from wildly varying ones to near perfect 110/220 v for household use?

I'm also interested to know how was this done in older times like early 1900s and before.


texts: Part identification, 38 pins IC with HCT38540A marking

texts:
I saw this part on a local market categorized as "unknown parts".
out of curiosity I searched 74HC38540, HCT38540 and HCT38540A with no results. the marking in the first line beside TI logo reads 244 so I searched 74HCT244 which is a well known line driver with 20 pins. but this one has 38 pins.
there are 2 little metal edges around pin 11. so I thought this must be two 74HCT244 ICs connected together and the metal markings indicate pin 1 of the second IC, with common supply pins (pin 10 being GND).
any Ideas about this? and if it's two 74HC244 in one case (like NE556?), why with no datasheet and an obstructed marking ?


texts: LED Strip setup on stairs. Unsure which power supply will work for 1200 LEDs

texts:
EDIT: Added a solution that may work. Please see the bottom for update.

As you can see in the photo, (sorry for the bad schematic, I am new to this) I want to have sufficient power to all the LEDs but am not sure how strong a power supply I will need for this to work without burning the LEDs. I see I'll need 5v since everything is powered by 5v, but I'm not sure how to calculate the amperage.

This is going to be used on each stair for a total of about 18 steps. Each LED strip will be about 1m long with 1ft of wire connecting each strip. At the bottom step, I will be using about 2.5m of wire to reach the power source (the plug in the wall). Would any gauge wire be fine for this?

If anyone sees any flaws with my design, I would appreciate any help as I am new to this and am trying to set this up for my mother who seems very excited for it. I don't want to mess it up and cost her a lot of money. FYI i didn't include the negative side to not confuse people with my poorly drawn schematic, but it would follow the same path as positive, only backwards.

Parts from Amazon.ca

ESP8266 Wifi Controller
Could only post 2 links: amazon.ca/gp/product/B01F5ALLFM/ref=ox_sc_act_title_1?smid=AZP2XD12VOJLM&psc=1

Addressable LED Strip
https://www.amazon.ca/gp/product/B014R5PC42/ref=ox_sc_act_title_2?smid=AA0YO4F2UD50F&psc=1

PIR Motion Sensors
Could only post 2 links: amazon.ca/gp/product/B019SX6ZR6/ref=ox_sc_act_title_6?smid=A3BYPBV6CTUPBO&psc=1

So i have now found what might work but still want to make sure with everyone here that it is a good option as i know there are multiple ways of doing this now. I found this in an adafruit tutorial.

I would use a 5V 80A power supply with 3 power outs. As i am new i would appreciate any suggestions on which fuse and which bus bars to get. (Tried researching but i cant find one that looks like the schematic). I live in Canada by the way in case you send links to local shops.

I would use busbar 1 for PIR sensor 1(bottom of the stairs), Busbar 2 for ESP8266, and Busbar 3 for PIR sensor 2(top of the stairs)


texts: Meaning of "pulse duration" in transistor datasheets?

texts:
I have a somewhat basic question. Many transistor datasheets have something like this for the peak current:

pulse duration = 300 μs, duty cycle ≤ 1 %

What does pulse duration mean? Is it only the on time, or is it the time period (on + off time)?

so, for above, which is correct?

A) 3us on, 297us off

or

B) 300us on, 29.7ms off

I'm guessing B is more useful, but A might look better on paper (except if transistor is too slow). So I'm somewhat confused (not having any engineering background and all...)


texts: Effect of bandwidth of stator winding in induction motor

texts:
The stator in squirrel cage induction motors is an RL circuit with 3db attenuation
$$
\frac{R}{2\pi L}Hz
$$
Does that mean an IM designed for 60Hz should also have the stator bandwidth at least 60Hz? My argument is that if the stator winding bandwidth was only 0.1Hz (for an extreme example), then a 60Hz signal would be too quick for the circuit and the circuit cannot respond to the input. Also, the current would be too low to produce any torque in the machine at 60Hz.
I have an IM and estimated the 3db bandwidth to be only 20Hz. I wanted to run it at 60Hz using a low cost VFD.


texts: I have a basic flip switch that I want to use to control whether a DC power socket is providing energy (from a connected battery pack). The power socket has three prongs, the switch has three, and there are the normal two wires (red and black) coming from the battery pack. What I'm not sure about is how to wire the three together so that when the switch is in one position the socket provides power (from the battery pack) and when the switch is in the other position the socket does not. For both the switch and the socket one prong is obviously in the center and the other two are indistinguishable.


texts: Measure Power Consumption of Battery Charger?

texts:
I want to ask how to measure power consumption of battery (Li-On 18650) charger module (TP4056 and USB Boost) and the total power consumption, if i have this circuit:

I have already know the power drawn of my circuit, lets say its 0.5 Watt (5V * 0.1 A). But how about the charger module and USB boost? Since i couldn't find its datasheet.

References (from ebay):

TP4056 Module
USB Boost 5v

Thank You


texts: Help identifying a motor and how to control it with an Arduino

texts:
I'm experimenting with controlling the transport of an old super-8 film projector via Arduino. My current solution starts/stops the motor by simply switching the projector's pause button via relay, which gives me one-directional control and one speed.

But I want to control both the direction and speed of the motor.
The projector has buttons for forward/backward and a wheel connected to an adjustable resistor for speed, but the best thing would be if I could override these (late 1960s) controls entirely and drive the motor directly from the Arduino.

So I'm asking two things.

a) Help identify the type of motor, as I have no idea (my guess would be some  AC type..?)

It says 55W / 7000rpm on the motor, and it appears that it runs on mains voltage.
The big transformer to the right appears to be only connected to the lamp.

Here is a picture of the motor:

Beneath the motor is its switchboard, on the rear side of which are the user-buttons. The 4 leftmost wires connect to various locations on the motor (coils?).

This is hard to see in the pictures, but the two round capacitors are both connected to the motor's outer frame, one connects to the black wire towards the motor, the other is connected to the blue wire at the right side of the switchboard.

So there's 3 wires leading to the switchboard which are not connected directly to the motor. The rightmost (black) comes from that voltage switch beneath the power inlet. The blue one also comes from the voltage switch, after passing the speed control (adjustable resistor) first. The brown wire is connected to the rightmost pin of the power inlet.

Here is a closer look at the wiring:

b) What would a control circuit look like and what parts do I need?
I guess I need a special driver unit capable of handling the 240V mains voltage?


texts: Is it possible to program an STM32 with an Arduino?

texts:
I have one of these:
http://www.ebay.com/itm/111297094334?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

I know an USB-TLL dongle is usually used to program it, but I don't have one and I really don't want to wait 2 weeks until it arrives.

Is it possible to program it with an Arduino ? I have a Arduino Mega and Uno laying around. Thanks.


texts: Why does increasing the modulation index of GFSK reduces peak power, increases the range & robustness of a bluetooth connection?

texts:
I was going through a Bluetooth LE tutorial in which it was mentioned that by increasing the modulation index of GFSK scheme, the peak power was reduced & range & robustness was enhanced over Bluetooth Classic. I would like to know how has this been achieved?

Thanks ,


texts: What causes a brushless motor to heat up?

texts:
I have an RC airplane and I installed a motor on it. I want to guard against the motor burning up, and I have a few questions:

What causes waste heat in the motor? Is it purely proportional to the current used to drive it, or is it current and voltage? In other words, if I drive it at 10A/10V, will it get just as hot as if I drive it at 10A/20V?
Is there any way to estimate the maximum current/power the motor can safely take if this is not published by the manufacturer?

Thanks!


texts: I have a relay in my car that is constantly fed power through a fuse to terminal 30 and terminal 86, the wiring diagram shows the ignition does not need to be on. When I check positions 30 and 86 with the relay out, they have power. The relay is grounded by the  computer to terminal 85 when the ignition is turned on and as I understand it should close the relay 30 to 87. It isn't doing that. With the ignition off, and testing for continuity I put a voltmeter on the wire coming from 85 to the computer, with the relay in, it is showing 12v, nothing with the relay out, it is supposed to be a ground. If I disconnect the negative terminal from the battery and pull the relay out to check again, I get voltage at 87 as well as 30 and 86. The voltage at 87 is not present when the negative battery terminal is attached. I can't understand how position 87 can have power with the negative battery terminal disconnected or why power is going into 85 when the relay is in. Thanks in advance if you have any ideas.  Relay 229 in this picture https://saabwisonline.com/images/9440/img-ff/ffpv0406.jpg


texts:
I'm trying to couple multiple piezoelectric discs as parallel to get electrical energy through vibration. using LTC3588 rectifier , which way is correct:

wiring all piezo parallel,then connect output to a single ltc3588?

use discrete ltc3588 for each piezo, then after rectifying connect them all together as parallel to increase output current?
P.S: this circuit is going to be used as a charger for a 3.7 V rechargeable battery , and this is cause of focusing on parallel wiring(increase output current).


texts:
Now before you all call me a retard
Let me just state that I know nothing about the electrical world at all.
But I need someone help me answer my question

So I have a TV that says on the back 'Input; DC 12v 3000aH'
and I have a power supply that says 'Output; DC 12v 2A'

Will that work? Or burn down my house?
(I assume 'aH' and 'A' means the same thing) My common sense tells me that the power supply should say 'Output; DC 12v 3A'
(Fyi i lost the original power supply for the TV)
So I need to buy a new one

Much appreciate anyone who answers this


texts: My BeagleBone Black reboots periodically after some random time (> 5hours)? I am totally stucked with ideas, I have my app working for that some random time and system gets reset. BBB works on Debian Linux. Is there any solution for this, whether someone was in the same situation?


texts: AMS117 ADJ - Is it possible to control output voltage using DAC

texts: I have tried to answer this question myself but unfortunately analog electronics is not my strongest point. Just thinking if it is possible to control output voltage of the AMS117 ADJ using DAC output.


texts: Connect Android device to Arduino Uno via USB

texts:
I have an Arduino Uno and need to connect to an Android device:

Do I need a USB host shield?
Would I be better off in buying a board that has USB host functionality built-in?
Is the Android Open Accessory framework really the only software solution for communicating via USB?


texts: Why is the collector current I_c for a normal common emitter BJT circuit LARGER than that of the Darlington transistor circuit configuration?

texts:
I'm a noob to electronics and have been reading up on transistors.

I tried to simulate Darlington (NPN) and Sziklai transistor and compare them against a single common emitter NPN configuration, shown below:

All the transistors shown have the exact same gain (ß=100) and other stats, resistors etc are all the same.

However, the collector current in the single NPN transistor is 49.3mA, which is higher than those of the Darlington and Sziklai configurations (42.88, 43.02mA resp.).

I would have expected a ß2+2ß gain for the Darlington and Sziklai pairs, so why is their collector current lower?

For the Darlington, I do understand that there is a 0.6*2 VBE voltage drop, and so the base current, Ib, is lower. (Indeed it is -  -  according to the simulation). Hence, the final IC might be slightly lower.

However, this is NOT the case for the Sziklai pair. I checked the base current for both NPN and Sziklai, and they are the same at 4.3mA.

So, why is the IC for the NPN transistor configuration higher? Is the simulation faulty or am I missing something?


texts:
I am developing a driver for a Li-Poly battery. This is the first time I am dealing with such battery. Does these types of battery always rise to the maximum voltage of 4.1 (based on the datasheet and measurement) even after several charge discharge? i.e. after 500 times.

I know by experience it cannot hold the same amount of charge over time, but can it always rise to the max voltage specified?

Thx


texts: VHDL: Is it a good practice to fill in a design with assertions?

texts: I am not very familiar with how assertions work in SystemVerilog. However, is it a good technique to put assertions into VHDL RTL? This will only flag up invalid inputs and nothing more.


texts: Circuit for supporting, common anode AND cathode RGB LED Matrices

texts:
I'm designing a driver / controller board for 8x8 RGB LED Matrices that then can be daisy chained to e.g. make an 16x64 Matrix or so.

So I came up with a couple of designs that I've tested and so on,.. but as I wanted to purchase all the LEDs ( in packs of 1000 ), I realized that my designs all require either common anode or common cathode RGB LEDs...

I was wondering if there is a way to switch between two "modes".

One for using common anode LEDs and one for common cathode LEDs.

I've sketched this circuit that is using two opto-isolators and a pin strip ( 3 pin ) with a jumper as a switch.
( I could also use an on-on-switch instead )

If I bridge the top and the middle pin, I can use common anode RGB LEDs.
If I bridge the bottom and the middle pin I can use LEDs with common cathode.
Can't I ?

I am a Software engineer / developer, so bare with me if this is totally wrong and please tell me the correct / better way of achieving this functionality.

Thank you.

EDIT

Here's a second image that shows my idea in a better way.

Between the LEDs ( ! ) and that "mode switching circuit" there will be transistors that are switched via decoders and shift registers.

The Matrix "module" will only contain the transistors and the 3 to 8 decoder with an enable bit ( latch ? ) and all the other parts will be on the driver board, shared by all the other matrix modules...

Much shown, but I hope it helps to imagine / understand my original problem / question.

Thank you again.


texts: A confusion about a transfer function's Bode plot and s domain view

texts:
Recently I have been stuck with a simple Bode plot and H(s) comparison.

To begin with, here is the transfer function:

H(s) = 1/s

For Bode plots I write:

H(jw) = (jω)^-1 = 1/(jω)

For the magnitude and phase I use:

|H(jω)| = 20*log(abs(H)) versus log(ω) and here is the plot:

You see above at ω = 0 the dB is finite and in this case it is zero.

Now I 3D plot |H(s)| on the s-plane and try to see how it will show up along the imaginary axis. It is because the Bode plot should be the projection of |H(s)| on the imaginary axis.

Now below is the plot of |H(s)|:

As you see, for the same transfer function 1/s the projection of |H(s)| on the imaginary axis is not the same with the Bode plots I obtained at the beginning.
The Bode plot is logarithmic but the at ω = 0 projection of |H(s)| on the imaginary axis goes to infinity, on the other hand in the Bode plot it is zero.

What is wrong here?

Edit:

From the answer I found out the problem was I was blindly plotting versus log10(ω).

Actually when transfer function is in dB it becomes as:

But on the other hand look what happens below when you plot the Bode plot linearly
ω versus |H(jω)|:

MATLAB plots infinity as 1.


texts:
We want to implement current sharing from two supplies on our PCB. There are dedicated ICs to implement this functionality, but we could only find UCC39002 from TI. How come no other manufacturer carry a similar IC, or maybe we simply couldn't search properly? In summary, are there any alternatives to ucc39002 from TI?

Related link: http://focus.ti.com.cn/cn/lit/an/slua550/slua550.pdf


texts:
What is the number of GFlops per cpu cycle for IBM Power8?

Flops per cpu cycle is obtained as ( number of double precision floating point numbers fitting into one vector processing unit (if any) ) * (# Vector processing units) * 2 (if FMA is supported).

What is it for a Power8 processor? I read that Power* currently has one vector processing unit per core, and it is supporting 4 double precision numbers in it. so for instance for Power S822LC model 8355-GTA I find a peak performance of
(8 cores) * (3.32 GHz) * (4*2) = 212 GFlops per socket. Could someone confirm? In my calculation, 4*2 is the number of Flops per cpu cycle, 4 is the number of double precision number in register and the factor 2 is for FMA support.


texts: LP311 collector remains at ~11V when "low"

texts:
Okay,

I'm trying to monitor current going to a device, and in case current is drawn, light a led and provide a low signal (<5V) to a microcontroller.

The current goes through a half-ohm resistor and the voltage difference is amplified by AD8210. Output of the amplifier is compared to a reference value set by a potentiometer using a LP311. Reference value is set by hand so that the led illuminates when the load is active.

This far everything goes fine, but trying to read the status to a microcontroller won't work, as LP311's collector stays at ~11V even when active.

My only idea so far has been that the output transistor is not saturated. However, increasing the load current and therefore increasing the comparator input difference should then bring collector voltage lower, but this was not the case.

So, why is emitter-collector voltage so high? I was expecting it to be 1V or less.

simulate this circuit – Schematic created using CircuitLab


texts: Is a stage box with an iron grid safe using this way?

texts:
See also my previous question:

How should I bypass switches

Where I made a circuit directly by mains, and as proposal by very useful comments to use a separate 'control' circuit at 9 or 12V.

However, according to this video:

How to Build On-Stage Light Boxes for Your Band

the switch under the 'plateau' is directly connected to 220V.

However, in my case I want to make a very important change: I don't want to use plexi glass, but a metal grid (like this):

I assume it would not safe to make a switch directly under this iron grid that is connected to 220V? Or is it actually not really safe for the plexi glass solution as in the YouTube video neither?

(Btw, I think according to the related earlier question, I'm going for a transistor/relay/triac solution anyway).

And a side question: another band I seen, uses a foot switch instead of a switch under the grid. I'm almost sure that foot switch is connected directly to mains (meaning 220V goes through it). Now this is seen quite often with living room lamps etc... but I wonder if this is safe on a music stage (what if someone would drop beer over it, and the foot switch is not 100% 'closed' somehow) ?


texts: Actual amps vs. what is stated on the power supply

texts:
I'm not very knowledgable about EE so I apologize if some of my terminology is off. At work, I need to set-up a bunch of (100+) wireless routers for a test farm and I'm trying to figure out what kind of power strips to use to power them all up.

On the power supplies, I'd say the average amps is between 1 - 1.5. Most consumer-grade power strips for 120v top out at 15 amps. I'm trying to maximize how many routers I can power with each strip. Is there any way to guesstimate the amps vs. the figure that's stated on the power supply?

The routers will most likely have their wireless radio turned off and will be mostly doing general processing and read/write stuff.

Massive thanks!

edit: There are 20A power strips also, but it's still fairly restrictive.


texts: Voltage drop @24V2A using a MOSFET with Arduino

texts:
I'm not really good with electronics but i'm really trying to learn as much as i can, so please have mercy on my question :)

Hardware
So, i have an Arduino Uno, a 24V 150W power supply, a 24V 48W LED strip and an IRL540N (Datasheet) mosfet.

The goal
The idea is to turn on/off the LED strip using Arduino PWM.
So far i have achieved that (schematic below), however i have an issue.

The issue
I have partically achieved my goal, however i get voltage drop of 3.4V after the mosfert, which i dont understand. I assume that's not normal, but i cant figure out why it's occuring ?

What i've learned about the issue on my own
I've been reading a lot and i've stumbled upon posts for similar usage, where it has been explained that this is a high side usage for a mosfet and needs a P channel mosfet, however i still cant figure out why.
Can someone please explain why do i have that voltage drop and what am i missing ?

Notes
I have 5v at the gate, and i am within the voltage and current limits supported by the mosfet. Running the gate @5V runs the LED strip @20.5V at 2A and the fet doesnt even get hot, so everything except the voltage is great and as per my needs.

Schematic


texts: LCD backlight LED voltage. Insignia (Sharp) Model NS-32D20SNA14

texts:
I have a TV LED back light panel from Insignia (Sharp) Model NS-32D20SNA14

I have isolated the back frame with the LED panel. The power clip is intact. Everything else is removed.

Using a VOM to get the total R of the circuit, how do I figure out the lowest voltage to illuminate the panel. All other circuitry has been removed. The LCD screen was broken.

I am an amateur with the least bit of electronics training.

Thank you for anything that comes to (your) mind.


texts: Replacing a NTC in Meanwell Power Supply

texts:
I have a query regarding replacing a NTC on a Meanwell dual output power supply. I managed to blow a stepper motor driver and the power supply last night (accidentally swapped a plug to a different stepper driver which turns out was wired differently), and my initial investigation on the power supply shows the NTC isn't allowing mains voltage through.
Unfortunately I have a several day wait for an exact replacement to be sent, and the local electronics store only have generic products labeled 'Epoxy Dip NTC Thermistor'.
I have two questions:

assuming this is for inrush current limiting, will the different style (epoxy vs metal disk) impact the behaviour?
If the different style will work, would there be an impact if a 5 ohm metal disk version is replaced with a 15 ohm epoxy dip?

I suspect if this goes badly it'll blow the NTC or other components on the board before the fuse melts, but I feel it would be a good idea to check with the hive mind to get an opinion from someone smarter than me.
I should add, the characteristics between the original (marked 5D-11) are very similar to the new/expoxy one - the biggest difference is the resistance.


texts: What is the symbol for this very site? What type of diode?

texts: What specific type of diode (presumably) is the logo for Electrical Engineering Stack Exchange?


texts: What commands in assembly cast value from hexa to decimal when they are called?

texts:
how can I know if a command is treating an immediate as a decimal or as a hexadecimal? For e.g div casts the values into decimal before it makes the arithmetic division:

.data
x: .quad 0x16
y: .quad 0x7
z: .space 8

.text
.global main
main:
    xor %rax, %rax
    xor %rbx, %rbx
    xor %rdx, %rdx
    movq x, %rax
    movq y, %rbx
    div %rbx
    movq %rax, z
    ret

I'm getting those results:

and my guess is that div looks at the decimal value of the number inside a register (cast it from hex to dec) but is it always like that in all arithmetic commands? Are there commands from different type that also act like this? I've tried reading the manual, but it doesn't specified there, I found it out by accident when debugging in sasm.

Thank you very much for your time and attention.


texts: Audio Amplifier with Bootstrap connection

texts:
I started to study more these days about Audio Amplifiers in class AB and I came across about something called bootstrap connection.

As far as I know bootstrap is used to pull the signal higher than the supply voltage and lower than the ground (in this case) since this schematic is based on a single-ended power supply.

The book only mentions that R8,R9 and C5 is a bootstrap connection used for optimisation but I don't really get why is this so.

Could someone explain me how does it work?


texts: Building A Voltage Threshold Indicator with Wide Voltage Window (0-600V)

texts:
Background:

I'm from A Formula SAE Team designing a building a EV to Compete in an FSAE Competition.

Situation:

We construct an Accumulator that houses the batteries and related components.
This has to have an indicator that indicates when the Vehicle side of the Isolation Relays has a DC Voltage of above 60V.

That is to say when the exposed +/- terminals of the accumulator have a VDC of 60V or higher an indicator is lit.

Idea:

Basic 60V Zener Diode inline with appropriate resistor for current limit.

i.e 1N5264B-TP Zener Diode

Problem:

how do I deal with such a wide voltage window?

I'm having trouble working out from the diode datasheets whether or not applying up to 600V is possible, obviously the maximum voltage is not unlimited but it's hard to find out what the window actually is.

Note: the circuit may not see up to 600V, it's just that according to FSAE-EV Rules we are not allowed a tractive voltage above 600V, so any circuit that can work with 60V-600V will suit us regardless of what the end voltage may be.

We expect the actual voltage to be somewhere around the 450-500V +/- 50V


texts:
Me and my friends are starting work on a small robotics product.
We are just starting out in product creation, and were wondering how to transfer our programming to the bot's ssd.
We realize we can get the data over wifi, but we'd still require the basic infrastructure to handle the requests.
We thought we'd do a removable ssd that we could simply unplug from the bot's motherboard, and plug into a ssd to usb chip.
Notice we are looking for a small chip, the size you'd find on a stick of ram or smartphone, not a consumer pc sized drive.
My question is, does a removable ssd chip exist, and where might we find one?


texts: Alternatives to High Wattage Resistors? (Do multiple low-wattage resistors equal a single higher wattage resistor?)

texts:
I am a beginner, so I may have made a horrible mistake in my diagram, but I am trying to learn.

According as I have figured it, I am having an issue wherein I need a resistor rated for a minimum of about 1.07 Watts; this is well, however, I do not have any resistors rated that highly heat-wise. I figured that I could just use a group of five 1/4W resistors, similarly to how a pair of two different resistors adds to a higher resistance.

*That does say 20kΩ and 29.6kΩ in the schem.; I have no idea why I opted to not write the capital omega in those two places.


texts: Hi I'm new to electronics and I would like to know how to measure experimentally the input and output resistance of the following common emitter configuration. I have access to a voltmeter, signal generator, power supply and an oscilloscope as well.


texts: Is this a feasable method for using 12VDC LEDs as power indicators?

texts:
I've been looking for the answer, but everything I've found is assuming the LED is of a lesser voltage, or a fixed voltage.  More than anything, I'm trying to determine if the concept below is feasible before I begin blowing the poor little guys up.

I'm building a control panel for a railroad layout.  Below is a brief example of what I'm putting together.  My apologies for the poor schematic.  For reference, the screw terminals represent the power input and relay output (sans the center, unused terminal) on a Vellman Mk111.  Please note that the label "To ?V Lighing" is 12VDC (haven't changed that yet).

Starting from the left, the first and second are for two separate 12VDC lighting connections.  The extra to their right is representative of four Vellman MK111 Timers (to save space, only one is shown).  The SPDT switch shown there represents a NC momentary switch that will be added to each of these timers.  There will be one LED there to show power to those circuits.  The power supply is 12VDC, 1A.  Each Timer is rated at 100ma.

The separate diagram on the far right begins at the output of a MRC Railpower 1300, which has a variable output between 0-15VDC, up to 7A.  The datasheet I found does not specify if the 7A is supplied to the DC output, the A/C output (which I will not be using) or a combination of both.  Having tested each locomotive running with a voltmeter (to log the voltage needed to run at scale speeds), they will be running between 9 to 11VDC maximum.  The LED indicator has been added to indicate when the Timer is active to a small section of electrically isolated track, allowing the train to move forward onto the rest of the layout, which is powered constantly, only to stop once it reaches this track until the timer activates several minutes later.  The SPDT switch allows continuous operation in the event I need it.

The LEDs that will be used are supplied by All Electronics, part number LED-12B, 12V Blue Diffused LED, 5MM (T1 3/4).  Data from their website indicates "built-in resistors for 12Vdc, 12mA operation. No external resistor required. Works well on 4-12Vdc. Dimmer at lower voltages."  Not worried about the dimmer operation.

Again, I'm looking to verify the feasibility of using a 12V LED in such an application, and as to whether or not it is being applied properly.  My apologies for the long explanation, but I felt some may find it useful to help determine an answer and try to give as much info as possible to eliminate confusion.

Knowing my luck, I just created a lot more confusion.  I can be good at that!


texts: Embedded Linux project - finding supported peripherals

texts:
We're starting an embedded board project.  We're exploring using embedded Linux and would like to select peripherals with working Linux drivers.

My question - for different subsystems (ethernet, memory, storage, etc) how do I determine what chips are supported, or if I had a chip - the KSZ8463 for example (http://www.microchip.com/wwwproducts/en/KSZ8463) how do I determine if it has linux driver support?

I suppose that I could look in the device tree and grep for things, but would KSZ8463 be presented as KSZ84xx or some other variant.  Things start getting more complicated quickly with the compatible driver support mechanism

I did see the Linux Kernel Device Database (LKDDb at https://cateee.net/lkddb/) but it doesn't seem to have been updated since 2007.

Is it possible to either get a complete list of supported chips for a given subsystem, or see if a given chip (the KSZ8463 for example) has an explicit driver or is supported via a compatible driver?

configuring a kernel for my arch with make menuconfig as suggested by @IgnacioVazquez-Abrams provides a lot of information, but there's not always a list of specific devices or families.

As an example, this is the configuration for ethernet phy device support

Does that mean all microchip ethernet chips are supported, but TI only supports the DP83848?  Is there a way to find the actual known supported microchip ethernet chips (or any other chip where the description is as vague or "most devices supported"


texts:
I'd really like to make a calculator which outputs the width of a conductor given the following inputs:  resistivity, trace thickness, trace length, applied power (or current and voltage), not to exceed dT of 10C.

Or in other words, I'd really like a trace width calculator which could be used for any material, not just copper, at any thickness (not just 1/2oz, 1oz, etc).

Any idea on which equation(s) to use?


texts: What is the purpose of a capacitor placed between the Base and Emitter of NPN Transistor & Zener Diode placed between Gate Source of MOSFET

texts:
Schematic (Current Limiter Circuit):

Question 1 :
I just want to understand what is the purpose of the capacitor when it is placed between the Base and Emitter of NPN or PNP transistor? In some designs I have noticed the values is in uF range and in other places, I have noticed the value is in nF range. In the above schematic, there are 3 capacitors placed across the base emitter of the BJTs. C2201, C2202 and C2203. All capacitors are of different values. So, on what basis is the value of the capacitors selected ?
Can someone tell me what is the purpose of those capacitors and how the capacitance value is arrived? If the answer is based on miller capacitance, can you please explain that concept in simple terms and somewhat practical or intuitive value of understanding?
All I understand about the Miller capacitance from what I have read is that, Miller capacitance is an inherent and undesirable property of BJT or MOSFET which cannot be avoided. Other than this, I am not sure how the miller capacitance actually affects during switching of BJT. Any simple example could be really helpful to me.
Question 2 :
Not in all circuit designs. In some designs, I have noticed zener diodes placed between the gate and source of the MOSFETs. The zener diode breakdown voltage is less than the maximum gate source voltage. Can someone tell me the reasons for placing the Zener diode between the gate and source of the MOSFET?


texts:
I'm having some trouble understanding the effect that charge injection has on capacitors - more specifically, when there is unequal charge on a capacitor.

Consider the following circuit:

My understanding is as follows

Assume that Vin is at a constant 1V. Initially, the CK is high and the MOSFET is on with a channel present. Let's also assume that the Ron is neglidble and there is enough time for the capacitor to settle at a final voltage. The capacitor has a voltage of 1V across it and thus Vout = 1V
The CK goes low just as in the image. The free electrons present in the channel need to go somewhere now since the channel is no longer present as the MOSFET is off now. Some of these electrons go to the source Vin and are absorbed there by an ideal voltage source and some of these electrons go to the top plate of the capacitor.
Now, here comes the confusion. Most books say that the 1V on the capacitor will decrease slightly to let's say 0.96V and that can be proven by the Q=CV. I want a more intuitive understanding. My understanding is that these "injected" electrons come to the top plate of the capacitor which I assume is the + plate. These new electrons recombine with positve charges there resulting in a smaller number of positive charges on the top plate and hence the bottom negative plate loses some electrons too as there is not enough attraction for them. Thus capacitor voltage decreases.

Q1: Is my understanding correct?

I don't think it's correct (particularly the part about how the electron recombines - I feel that's only relevant to semiconductor physics) because of the following section in Razavi's book which suggests how to cancel this effect. Consider the following circuit:

Now, if we use my same logic of the electron cancelling the positive charge on the top plate. Then in this case, as soon as M1 goes low, charge q1 is injected to the top positive plate of capacitor, recombining with a "hole" and thus when M2 goes high, there is nothing for it to absorb since that initial charge injected by M1 has already decreased the capacitor voltage. What will M2 even do at this point?

Does my argument seem reasonable?


texts: STM32F0, stopping timer at the end of the counting period

texts: How to stop the STM32 MCU timer (general-purpose) at the end of the counting period (counter reaches TIMx_ARR value), not immediately e.g. in the middle of period of running counter. This is on stop request that might occur at any time.


texts: Apply positive and negative voltage to component using single power supply

texts:
I have an electromagnet and a 12V power supply.
I would like to apply +12V to the electromagnet at some times and -12V at other times.

My current thought is to use four transistors (two NPN, two PNP) in a matrix (see diagram).
I have two concerns:

When all four transistors are open, the "inside" leads will be floating. Is this a problem? If so, would a pulldown resistor on the "inside" sides mitigate it?
Using two transistors (one each side) would be cheaper and take up less space, but I can't figure out a way to do it (even with diodes) that doesn't short out the power supply. Is there an easy way to do this (besides adding a second -12V supply)?

Thanks!


texts: Can I safely run a 6V DC air pump using a 9V Car adapter

texts:
I have seen some general comments online about running a 6V DC motor on 9V Battery being OK.
I am looking to run an air mattress pump originally designed for 4x 1.5V D batteries (6V DC) from a universal car laptop adapter. The lowest output voltage on the car adapter is 9V.

Nothing on the air pump motor mentions input power specs specifically. The only markings I can see are the following 3 lines and I get no hits googling each string.
hb-138-101
rs-380ph-6016rb
630301

The alternative would be to use an AC inverter and an DC 6v 2A adapter. It sounds like overkill to go from 12v to 120v AC just to get 6VDC, but so is running a car engine.
Will I burn the motor if I ran it on 9V DC?


texts:
After getting some useful feedback from this question (BJT Common Emitter - Active Load Biasing) I've been trying to intuit how the output voltage presents itself. Through a bit of trial and error I've stumbled upon the following method of determining the value for \$Rf\$ to get a desired \$Vout\$:
$$Rf = \frac{Vout}{\frac{Ic}{\beta}}$$
Update: Perhaps another way to look at it is \$Rf=R_{E} \cdot \beta\$?
For example, given \$IC =1mA\$ and Q1 as BC847C with \$\beta \approx 525\$:
$$Rf = \frac{7.5}{\frac{1mA}{525}}=3,936,750 \Omega \approx 4M\Omega$$
And for Q1 as 2N2222 with \$\beta \approx 200\$:
$$Rf = \frac{7.5}{\frac{1mA}{200}}=1.5M\Omega$$
Having taken the \$\beta\$ values from LTSpice I was able to validate this:

My question(s) are:

Is this legitimate - I'm guessing if so it's a well known equation/technique known by some name? Perhaps this
Assuming a \$V_{BE}=750mV\$, does the circuit above imply \$V_{E} = GND\$ so \$V_{CE} = V_{CC} - V_{E} - V_{C} = 15V - 0V - 7.55V = 7.45V\$?
What is the mechanism/behavior taking place that is creating this voltage?

Many Thanks


texts: Register r1 or $at, is it's sole use in pseudoinstructions? If so, is this the sole solution to enable pseudoinstructions within the architecture?


texts: How can I construct an 8 x 1 multiplexer from two 4 x 1 multiplexers with enable inputs?

texts: I've thought about this problem for two days, and I can't figure out the trick. It would be easy with an inverter and an OR gate, but I was told not to use anything but muxes and wires. I figured out how to build a 6 x 1 multiplexer from two 4 x 1 muxes, but that's not sufficient. Can you give me a hint?


texts: Different chemistry of batteries in operation

texts:
I had an idea of using different chemistry of batteries as shown in the schematic figure
Is that possible to design a system in that way. According to the design, I am using all the evaluation boards.
Buck charge controller for charging the batteries
Boost converter for stepping up voltage
ORing controller to share the common load bus.
Can some one please guide me whether that can be done or it?
I am sure there will be lot of power loss and decrease in efficiency.
Can some help me in understanding it?
Thanks in advance.


texts:
I'm wondering what type of buffers/techniques are typically used for connecting a cpu register(flip flops?) to a cpu bus(data/address/control). Since there are many registers on a single bus, I know there has to be some kind of tristate mechanism but how do you specify which buffers should be floating?

Thinking logically, there should be some kind of register select bit along with a read/write bit that toggles which register is in use and what it is doing with the value.  Even though this makes sense to me, I don't think it is practical to AND every register input with a register select or r/w bit.

I've been searching the internet for schematics or documentation and I can't find any solid information.   Most cpu schematics are so complicated that I'm having a hard time making sense of them.  Any help is greatly appreciated.


texts:
Is there a place to compare ARM-MCUs of different manufacturers?

something like this but way bigger:

http://www.mikrocontroller.net/articles/ARM_Selektor


texts: I want to design a device which receives basic text wirelessly, and outputs this text on a display. Using Wi-Fi is not a option. I have an idea that it would be possible to do this using FM frequencies. Would it be possible to make the text into some sort of analoge format, send it via FM, and then decoding the information in to text-format again?


texts: How to mitigate an unavoidable ground loop in a vehicle?

texts:
We have a display and a sensor that are installed in vehicles. The sensor is in a metal TO Can, and the manufacturer shorts the ground pin to the TO Can body for shielding. We mount that can in a metal probe, which of course touches the TO Can and so is also grounded. The metal probe is mounted to a plastic cover in the vehicle. However we have found some vehicles have metal covers now, which have electrical continuity to the chassis. The result is a ground loop which can cause intermittent failures of communication:

I have seen circuits where they separate chassis and signal grounds using resistors and capacitors. Could that mitigate the ground loop in this case, if one or both of the PCBs isolated their digital grounds from the chassis ground with a resistor and capacitor in parallel? I have also heard that resistors/capacitors to isolate grounds is a bad practice, so I'm confused why I see it on some automotive circuits.
I also thought of using opto-isolators so that grounds need not be shared between sensor and display. However, the problem with that is that if the sensor gets mounted in a plastic cover, then it has no connection to the chassis ground anymore. In that case the sensor would need to use the display's ground as a return path.


texts: Is regenerative braking always suitable for an EV regardless of battery chemistry?

texts:
I've been doing a lot of reading on different motion control approaches both for hardwire industrial motion, as well as EV applications.
While I've skimmed a few IEEE papers that sought to study the effects of regen braking on lithium-ion batteries as it impact battery capacity retention (cycles) they seemed somewhat inconclusive. This also only examines the common LiIon chemistry but doesn't even address other popular lithium-containing chemistries like LiFePo4 or NMC. I'm no chemist.
At a much smaller scale, we see use of NiCad and SLA batteries that are robust to being charged in a "don't care" fashion. However, lithium cells tend to be a bit more picky when it comes to being charged. Negating the aspect about total cell cycle degradation for a moment--what about safety when it comes to regen braking lithium-based cells?
Assuming the cell is sitting behind some basic controller--what happens to back-EMF from a large (200W+) motor if the cell is "fully" charged and the BMS shuts off the back-EMF transient? We know it will generate heat..but does that heat stay in the motor? Or are we talking about dissipation into the motor's bus/wiring? Should high-power (EV) motors powered by lithium chemistry employ shunt regulators if extending battery life by regen braking is not necessary? (Thinking more about industrial robots rather than EVs).


texts: Does audio powered LED light with low tension require CE/FCC certificate?

texts:
I am building an LED light that plugs into the audio jack of a mobile device and is powered by the 3.5mm audio plug of the smartphone. The LED works at very low tension and with audio frequencies below 2kHz.

Does such a device require a CE and FCC mark if I want to market it in the US and Europe?

I read a little about FCC 47 CFR 15 and I am rather confused.


texts: How do I build a switch-on circuit triggered by small signals, which will supply voltage for another circuit?

texts: The thing is, I have a small signal ([-5mV,5mV] up to [-35mV,35mV]) which is filtered and amplified by a conditioning circuit. But it all runs continually, and I should be able to power on the conditioning circuit only if there's something to amplify, so I can save battery.


texts: Using FFmpeg or other libraries on an ARM SoC without OS layer?

texts:
I would like to use FFmpeg on an ARM SoC to perform some decoding. Now, as I understand conventionally everybody uses it within an OS environment. However, I was wondering whether it is possible to also use FFmpeg or any other library without an OS layer?

I mean, it is possible to, let's say write C code, which is compiled into executables, that can directly run on an ARM processor without OS. So, it should also be possible to statically bind any other library source code into the executable and run it without OS, right?


texts: Do you have to wind transformers the same as electromagnets?

texts: Do I have to wind transformers in the same direction, as in each layer the winding must go in the same direction, like an electromagnet. And does this change with flybacks? Are their windings any different?


texts: Need to branch USB data lines... what to do with unused ends?

texts:
I have a USB 2.0 low-speed connection design with an unusual constraint. On the host side the D+ and D- lines have a branch, a requirement of the connector and this cannot be changed. On the device side, there is the option of either using just one side of each branch (and creating an unterminated stub on the host side) or connecting both (and forming a loop). This option is indicated by the dashed line.

Which option is better in terms of signal integrity, and how can it be improved. For example, if only the solid line on the device side was used would some kind of termination of the other host branch be helpful?

Thanks for any responses!


texts: Negative slack while designing a feedback controller using Xilinx System Generator

texts: I'm transforming the design  of a feedback controller(PI controller) which was already in Simulink, to FPGA using Xilinx System Generator. The main design problem i'm facing is the negative slack time. I'm adding delay blocks in the logical path in such a way that the inputs to a particular block(say AND gate) has the same delay. Is this the reason for getting negative slack?. Since the logic is quite complex, i had to add many delays in different path to make it reach at the same time.  In the attached figure shows an example of how the basic design is. The delay encircled in yellow is the additional delay added to make the output stable.


texts:
I have a circuit with 2 switches and 2 LED's. I want to control one LED with 1 button (which is a simple circuit). But I also want to turn off one of them, when the other is On. Is there a simple way to do this?

Overall, I should be able to turn both of them off, and only one should be on at a time.

Both switches are latching push on/push off switches.


texts: Comparator, inverting/non-inverting terminal voltage is more than supply voltage

texts:
I am using Comparator (schematic shown below). I have connected output with Vcc via 2k ohm resistor, as it has open collector output.

In this configuration output of the opamp should be 3.3V. But the output is coming 0V.

But if I change the supply voltage to 5V, then the output is showing 5V. (schematic below)

Is there any rule "voltage at the terminal (inverting/non-inverting) of the comparator should not be higher than supply voltage of the opamp.

Regards,


texts:
I'm looking to calibrate an energy meter.
As a part of that process, I need to cheaply find a device that can create a power-factor of 0.5, in order to calculate the required phase correction.
The best, or worst, device that I can put my hands on has a power factor of 0.78.
Everything else appears to be much better than that and, not being an electrical engineer, I'd prefer it if there was a device that wouldn't be too involved electronically.
Can anyone suggest, perhaps an off-the-shelf device, that would perform this badly?


texts: How unstable can digital supply voltage be?

texts:
I'm trying to pick the best (cost-effective, small footprint, reliable) dc-dc converter, to convert 24V -> 5V for my device. In the future I'm planning to switch to 3.3V.

The device consists of microcontroller, some logic ICs, RS485 transceiver and a few leds.

I need at most 300mA at 5V.

So far I tested three setups:

LM2576, running at 57kHz. 680uH inductor, 330uF input capacitor, 1000uF output capacitor. However, this setup is pretty big. Big inductor, two very large capacitors, and D2PAK converter use too much space on the board. Original IC is pretty expensive and designed for much higher currents (3A) than my needs (300mA).

Mornsun B2405S-1W, integrated DC-DC, 100kHz, 220uF input and output capacitor. It's almost ideal, but the input voltage may not vary more than 10% from 24V. There is also no 3.3V version availible. It is isolated (what I don't need) and quite hard to buy. The datasheet recommends 22uF electrolytic capacitor at the output, which also consumes some space.

RT8259, this was my last try. It's designed to be quite cheap and efficient. It is elastic enough to provide 5V and 3.3V. The datasheet recommends 22uF output, 10uF input ceramic capacitors and 6.8uH inductor. I used 10uH inductor. No electrolytic capacitor was an advantage for me. It runs at 1.4MHz. I used small CD32 inductor and SS31 diode.

The problem is, that with RT8259, I'm getting really unstable output voltage:

To compare - from LM2576:

and from B2405S-1W:

What I tried to do:

I tried adding 100nF ceramic, 4.7uF tantalum caps at the output of RT8259, but there was NO change.

The layout is exactly as in the datasheet.

The questions:

How bad is such voltage for powering digital circuits, like my? How
can I improve the output voltage?
If I increase the inductance,
should it help?
What is going to happen when the inductance is to
high / to low?


texts: Making dpdt relays from 2 spdt relays. Possibility of short circuit?

texts:
I am designing a changeover circuit that switches the load from one grid station to another. I was thinking about wiring two spdt relays in anti-parallel to create a dpdt switch.

The schematic at the end although a different application, best captures the question that I am about to ask.

My question is that can this cause a short circuit/connect the two grids during the small time period when the relay is switching. Does it matter if I am using a mechanical or a solid state relay? Is there any way to avoid this?


texts: How much energy is lost between (solar panels+battery pack) & DC operated electronics due to conversion

texts:
For the sake of simplicty;

I have solar panels generating Xvolt, Yamperage.

All of the power will be used by Xvolt devices.

But all of the house and device adapters are designed to use AC grid. So i need to convert Xvolt DC to AC220/110 volt (i dont know if AC volt changes the result in this application) and back to DC Xvolt again.

What percentage of the solar panels are used just for the conversion?


texts: why does dc amperage change if I install the power supply up-side down

texts: I build electrical control panels. I received a set of prints with a note to install the 24vdc power supplies in the upright position, because in the inverted position, the power supplies would drop from 10A output to 6A and the life span of the units would be reduced. Can anyone explain this to me? In 25 years, I've never seen this note before.


texts: Why can't NAND flash memory be a random access memory?

texts: When I read any documents regarding NAND and NOR flashes. They say that NAND is sequential memory whereas NOR is random. I dont understand what stops NAND memory from being random too as the only difference in these two memories are being serial and parallel.


texts:
I am trying to understand the concept of 'Context switch' in reference to C-language and 32-bit MCUs.
For example if I am programming STM32F407 MCU in C-language using STM32CubeIDE and I want to demonstrate full context switch of the MCU then how could I do that?
Do I need to service an Interrupt request for example an interrupt from a periodic timer? So when I will go into the Timer ISR it would imply that the MCU has experienced a full-context switch while jumping to the ISR (Interrupt Handler).
Or Do I need to make a function call? So that when the MCU jumps into a new function that will mean that the MCU has experienced a full-context switch?
Can anyone explain how can I demonstrate a Context-Switch in C-language?


texts: How to wire this transformer? I am not clear on what these wire colors mean and where they go

texts:
I read several color coding guides but I am not sure which wire goes where... My guess is that the black is the L wire, which stands for Live, and the white wire is the N, which stands for Neutral, and that I should ignore the blue wire:

So Black on L, White on N, blue stays disconnected.

Is that correct?

Thank you!


texts:
I have constructed the following circuit on a breadboard and all functions as it should with no issues.

However, each time I solder this project onto a perf board, the same issue arises. The LED starts bright then goes dim upon powering up. Then I get no functionality. It is an cree 3 Watt LED that uses two buttons, a TIP31, a 5V supply and a digispark ATtiny85. The draw is 600 mA maximum as measured when connected to bread board.

What I've done:

Measured 5V at input pins from buttons. Both check.
Reprogrammed the ATtiny after assembly.
Checked continuity on perf board to input output pins and power.
Power the LED directly, works fine.

Perhaps the digispark is that sensitive to solder heat? The transistor is a bad selection?