texts: Identifying the model of LCD for replacement for temperature sensor

texts:
I want to replace a broken LCD with a rubber zebra connector in a "cheap" temperature sensor. There is no model or any data on the screen nor on the PCB. I'm looking for a replacement part. How can I identify it?
UPDATE
So my initial question was beginner and optimistic. I should have asked (myself) if the LCD is custom-made or not. Cuz custom-made is unlikely to be sold. I received two answered, both indicating that such a screen is custom made (the emoji was the best clue for that). So I would like to accept one of the answers.
I attached photos of the broken and working one too:
Broken display:

Operational display:


texts: Can I use a TP4056 to solar charge a lithium ion battery

texts: This is kind of a continuation of an already existing question. I'm wondering if its possible to use a TP4056 based charger like this one to charge a 3.7 volt lithium ion battery with a 4.5 volt  45 ma solar panel. According to some specs and a post. it appears it's possible to get the charging current down to 50ma if you replace the resistor with a different value. Does this mean that its possible to get it down even lower like 40 ma if the value were tweaked to something like 40k. in particular I'm looking for a low cost already existing board to do the job.


texts: How does a negative power factor look when it is graphed? How will this impact apparent power versus true power versus reactive power? And how do we interpret this as per power dissipated versus power absorbed/returned to the system?


texts:
Can someone suggest an IC or Circuit to charge a single high-capacity Li-Po Cell?

I need some design that can charge powerful Li-Po batteries (think ~6000mah 1S 65~130C) at a reasonable rate (say 5hrs for full charge). An example battery would be this one.

I've found several parts such as the MAX8934A and BQ24230 but these are meant for portable applications and charge at low currents ~100mA which will take forever with a large cell. The available supply would be any common wall wart 1000mA supply (ie 5V, 6V, 12V ect.). Heat dissipation is not an big issue as space and airflow is available. This is part of a solution that is not a one-off so I can't just buy a Chinese $30 hobby Li-Po charger and use that.

I am looking for a solution for a 1 cell battery, however solutions for multi-cell might also work and are appreciated.


texts: Easiest way to short 50 pairs of wires together

texts:
I have a serial keyboard that has 24 pins and works via one of the top 11 pins shorting to one of the bottom 13 pins when you press a button (top and bottom membranes touch) and this is picked up by an interface board. I would like to simulate this with an Arduino. There are potentially 143 different combinations but I only need to simulate 50. Normally I would use a relay to act as a switch (i.e. pin 1 and 12 are connected to relay, arduino renergizes relay and these pins get connected) but I don't want to buy/connect 50 different relays along with diodes, transistors, etc. to control them. Is there another way to do this?

I have tried shorting both pins to ground and this is not read by the interface board and I have tried just using a regular transistor but since these pins aren't energized the transistor doesn't conduct.


texts: Stack up question...return current when signal layers sandwitched between planes

texts:
I have stack up like this:

My question is, when any signal layer is having GND plane on one side (above/below) and Signal Plane on other side (above/below). whether high speed return current will couple into signal layer also equally as like in surrounding GND plane. (In some sources I read that return current will split between layers based on their distance from routing layer.)

For example: S02 layer is 4.2mil from GND and 5mil from S03 layer, when the any signal is routed in S02 whether some return signal will couple to S03 also?

One more... I read return current can couple any PCB trace (may be like cross talk).

Whether return current can couple other signal traces also, even though they don't have any path to GND?


texts: Current flow due to capacitor in a basic power supply circuit

texts:
In a basic power supply like this one below, for a positive half-cycle the capacitor is charged up along with the rectified load current.

For negative half-cycle diode is "off", so no conduction from the input, but now the charged capacitor will supply current into load.

Now comes my question(confusion). When the capacitor is supplying current, doesn't it complete a path like this and turn diode "on" during negative half cycle?


texts:
I'm a beginner at electronics, and I'm wondering slightly...

I've bought electrolytic capacitors, and I'm attempting to charge them with a 9v battery. They seem to be running quite hot, too hot to touch.

Am I just overloading them with current? I didn't see any max current listed.

Also, I'm having trouble using the electrolytic capacitor afterwards. Does charge run from the positive or negative lead once I use it to, say, make LEDs shine?


texts:
I am curious how ESC's read a pwm signal. I previously thought they interpret the average voltage of the signal, and determine their AC output rate based on that.

However an ESC's output is based on pulswidth in between 1-2 ms, regardless of the period (assuming it is in 50-500 hz for my ESC's). So clearly it can't be only looking at avg. voltage, since 1.5 ms duty cycle corresponds to different average voltage for different periods.

So if not avg. voltage then what? Are they able to exactly pinpoint rising/falling edges?


texts: Not sure if this circuit will work, did I overlook anything?

texts: I plan to purchase a DS18b20 water temperature probe, and hook up the data line to an arduino. I would then connect the arduino to ten 5VDC 6A relays , and each relay would be connected to a 120VAC power source and a 300W heater. The resulting circuit will be able to control the temperature of a curing tank I've built, when temp hits 73degF, the arduino will send a LOW signal to all the relays, shutting off the heaters. When temp drops, the arduino will send a H signal, turning them back on. What do you all think? Opinions are much appreciated. The picture included is one heater to one relay.


texts: Frequency of TL084-based oscillator producing a triangular wave

texts: I used TL084 as the op-amp for this oscillator to generate a triangular wave. I thought the equation of the frequency was f0 = (R2/R3)/(4RC), but it's not true. What is it?


texts: isolation between lcd 20*4 lcd and tm4c123

texts:
power suply required for my launchpad is 3.3 v and that required for lcd is 5 v. I want to isolate lcd and launchpad. What should I do?
do i need to put optoisolator between each pin of lcd and controller?


texts:
Could I get an explanation for these datasheet definitions for a varistor?
 1) Max. applied voltage.
 2) Min varistor peak volts.
 3) Max varistor peak volts.
 4) The clamping voltage is known to be the maximum voltage can pass before it restricts.

This diagram is iv characteristic curve for varistor.


texts: in AVR, if i use .ORG 0 with the main program , where is the interrupt vector table and .INCLUDE file data go?

texts:
I am studying AVR from the book "the AVR microcontroller and Embedded system by Mohamed mazidi" and "atmega32A data sheet"

in the book, it puts samples of cade which start like this

.include "M32DEF.INC"

;...some macros...

;main program

.ORG 0
;some codes

if main program code starts at address 0x0000 where is the include file code starts at and even though shouldn't the address from 0x0000 to 0x003A are reserved for the interrupt vector table ?!


texts: Is it safe to swap a fused IEC cable to non-fused when in another country?

texts:
I have recently moved from Singapore to New Zealand and have brought a number of eletrical applicances with me e.g. computer, ricecooker, router, etc.

Since the voltages are the same (currently using travel adaptors with a power board), I was assuming that as long as the applicance doesn't draw over 10A, then I could just swap out the fused Brittish IEC C8 & C14 cables with local non-fused ones. However I noticed that the rice cooker (C13/14 with a 10A fuse) has a sticker on it warning: do not use power cord from other applicances, so it got me wondering if it was infact safe or if they were just being overly cautious (or wanting you to pay for their expensive replacement cord).

Can I safely swap these IEC cables over?


texts:
A basic question, how does the P-Mosfet reduce the inrush current.

simulate this circuit – Schematic created using CircuitLab
Old image link

Can the P-Mosfet's drain and source orientation be swapped along with the diode and would that cause any changes to the protection.

Please help.

http://archive.eetasia.com/www.eetasia.com/ARTICLES/2001JUL/2001JUL03_AMD_POW_TAC.PDF%3FSOURCES%3DDOWNLOAD


texts: Second-Order RLC Circuit and Short Circuits

texts:
I was given this circuit to analyze.

The first thing is I know that \$5u(t) = 5\$ for \$t>0\$ and \$5u(t) = 0\$ for \$t < 0\$. My book suggests to solve for initial conditions first (solve for \$v(0)\$ in the capacitor and solve for \$i(0)\$ in the inductor).
Here is where I got totally confused. For \$t < 0\$, the voltage source is short-circuited, giving me this circuit:

Which I argue that \$v(0^-)\$ = 0 because it is parallel to the short circuit. But, for \$t > 0\$, I drew this circuit:

Which I argue that \$v(0^+)\$ = 5 because it is parallel to the short circuit.
I know that for capacitors, the voltage cannot suddenly drop or increase, proving my analysis to be totally wrong. I checked using LTSPice,

which shows that the correct value for \$v(0^-) = v(0^+) = v(0) = 5V\$. However, I cannot derive what seemingly to be a linear function for \$v(t)\$ when \$t < 0\$.
How do I obtain the general equation for \$v(t)\$ for the capacitor or \$i(t)\$ for the inductor?
EDIT: I think I got my LTSpice wrong. The graph should look like this:

which shows a discontinuity at \$t = 0\$. I don't understand why this happens.


texts:
Before I solder very small electronic parts on PCB board, I want to find some needle point sized injector to inject tiny glue fix the parts, then do the soldering.
Some manufacturers used that, but I can not find what it is. Can anybody help?


texts: How to find the sketch energy of the capacitor (let's say versus time) with the q-v plot shown below?

texts:
I wonder what is the plot of the energy of the so-called capacitor,it's will be 0 except in 2 and 3 that is a delta function but when we want to calculate it's energy we don't know the exact value of voltage in the time 2 ,3.Is it correct to simply integrate the q-v plot from V=2 to V=0?
enter image description here


texts: Effect on signal bandwidth due to multiplication?

texts:
Recently I came across an statement which says,
If signal m(t) has bandwidth B then pow(m(t),n) will have bandwith nB.
To prove it mathematically I startted with,

Let n=2,
y(t)= m(t)xm(t)

y(t)=Convolution(M(f),M(f))    :: where M(f) is the fourier transform of M(t)

After that the book states that y(t) has bandwidth 2B.
Can someone point out to what I am missing here?


texts: Vibrating mesh transducer not nebulizing

texts:
Currently, I am trying to use a vibrating mesh transducer that's regulated using a high-voltage driver (100±5kHz, 65±5V), that's Grove Water Atomizer board.

Two problems have been arising, which I've been trying to address. Either the transducer heats up enormously (overheats) or it has difficulty atomizing (the liquid basically seeps through the holes and puddles on the "output side" of the transducer). Would anyone have any ideas as to what is causing this?


texts:
I am working on a project where a LED strip is placed at the bottom of a pool which will send patterns of light along the bottom of the pool. I have looked into some LED strips and found a 5V APA-102 32leds/meter IP68 (submersible waterproofing) LED strip that could be controlled using an Arduino Due and using the FASTLED library. The LED strip would go the length of the pool (25 meters) but I would only be powering 28 LEDs at a time so I figured I'll only need a 5V 2A power supply (since each LED would use 60mA full brightness) to power the system. I plan to power the LED strip every 5m to avoid voltage drop as well.

Do you think this would be safe to install in a pool? I am worried about the wiring becoming exposed and creating a short and having someone in the pool get hurt (or worse). And are there any suggestions to make this system safer?


texts: Automated Approaches for Measuring Audio Amplifier Frequency Response

texts:
I'm looking for a DIY or professional method for easily measuring frequency response of an audio system from 10Hz to 10kHz. It is for a guitar amplifier, and I would like a better way to characterize my changes without playing actual guitar through it all the time as I'm tweaking. Note this is a tube amplifier, so not easy to model.

In the RF world I would use a Vector Analyzer... I was trying to come up with an easy way using a scope and a sweep generator, but have yet to think of a good method.
The best I have so far:

Create a DDS system with an Arduino platform and take ADC measurements of the input and output peaks, but that involves a whole project on its own...
Using a DMM on AC mode, but it gets inaccurate above 1kHz it seems. (Faster then reading scope lines)
Some sort of Audacity plugin or program using my PCs audio card? (Nice automated plot or data export?)

I should note my scope does not have auto measure capability, it is from 1978... Otherwise, yes a modern scope I could at least use peak measure as I change the frequency generator.

Currently I occasionally take a pile of hand measurements with a generator and scope. Manually changing the frequency, and writing down the measurements.


texts:
I've recently had my first pcb made, to my surprise, everything was working, at least it did at first.
It's a simple board that lets me control some ledstrips with an ESP32 through wifi. Everything worked great, including the transistor circuit.
However, after a couple hours, the mcu became unresponsive, and after replugging the power supply, it seems as though the mcu is completely dead (no uart output on boot, not programmable with jtag). I know that the board did not short, I also measured the correct voltages on the MCU itself, as well as on the chip_enable pin (which is required for the ESP32 to boot) so I am quite confident that the only thing broken on the boards, is the MCU itself. I soldered together a second board, which had the exact same result.
In my initial design I did not have resistors on the data lines of the ledstrip and I did not have a resistor on the gate of the transistor.
Because the GPIOs of the ESP32 can only provide 12mAmps (according to the datasheet), I suspect that the lack of resistor on the gate of the transistor might be the cause.
Included I have the original schematic that was failing, and the new schematic with precautions in place.
Is there anything else that could cause the MCU to die?


texts:
I have a question regarding the ADCs ADS58B19 inputclock, this ADC can be clocked with LVDS.
The data sheet says that Vpp = 700mV, which is +-350mV. The ADCs Vcm = 1.7V, is this the in and output Vcm?
Is it possible to clock the ADC with a Vpp = 700mV and Vcm = 1V?
Datasheet: https://www.ti.com/lit/ds/symlink/ads58b19.pdf?ts=1602577981307&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FADS58B19
Clock Specifications on page 3.
Thanks


texts: distance detection and prevention methods

texts: Assume we have a security camera in front door attached to door itself and students trying block it by any possible object (solid/liquid/small/big). we want a proximity-sensor to Alert manager if any particle reach its distance limit area (for example we set 10cm distance limit and if anything try pass through this border, sensor must Alert). What is the cheapest sensor which for example use radiowave/infrared to detect any type of coming particles with any size and how much is false positive ratio ?


texts:
I am having problems with the MPLAB X debugger (although the release build works fine). It behaves very weirdly with my PIC16LF1937-based PICKIT3. Specifically:

It gets caught in random infinite loops
The step over function doesn't work most of the time
It only seems to debug the first few instructions
Setting a breakpoint on a late instruction will cause the PIC to freeze early

What could I be doing wrong? What things should I check?


texts:
I have seen different schemes in the three phase motor inverter design when people try to protect gate-source from high voltage as shown in the picture.

I understand the usage of zener diode to limit Vgs, and the usage of R to prevent unwanted switch-on when gate is floating (Am I correct in the understanding?). Here are my questions.

why are zener and R used together as the 3rd picture shows? Are
those different config related with inverter power ratings?
what's the difference between using zener diode and TVS diode as in 4th picture?
How to choose zener diode in term of breakdown voltage Vc? Vc higher
than Vth but lower than Vgsmax?

Edited

One more question, is it common to use zener and R in parallel between gate and source to both limit Vgs and avoid unwanted switch-on?


texts:
I want to make a circuit to do something that is relatively simple but I need to find the optimal way to do it in order to take as little current as possible. Here is what I want to do:

When a trigger is activated, it launches a cycle. A cycle is:

1 second "on" (let's say it closes a relay)
1.5 second "off" (opens the relay)
1 second "on" (closes the relay)
Turn "off" and then wait for the event to initiated the circuit to happen again. (relay is open).

The time "on" for step 1 and 3  needs to be the same but they are not necessarily the same as in step 2. The trigger that activates the circuit will probably be a short pulse. I thought about using one or two 555 timers and counters but I am not sure exactly how and not sure if that is the best way.. What would be the best way to do something like that to use as little current as possible? The circuit will run with batteries(4*AA or one 9V)...


texts: Why does this 8 step sequencer schematic need two resistors for each output pin?

texts:
I've found a schematic online for an 8 step sequencer and built it on a breadboard. Before I start experimenting with it and adding features, I'd like to find out if both 10k resistors are needed for each NPN transistor pair.
Here is the schematic:

As you can see, each output pin of the 4017 decade counter is split to two 10k resistors, each driving one NPN transistor (one for the tone output, one for an LED indicator).
My thought is that I could use a single 10k resistor connected to the output pin, after which the connection would split to the tone and the indicator.
Am I correct? If not, then I would really like to know the reason for the additional resistors.
Thanks!


texts: Can I use 2 exact same switching power supplies in parallel?

texts: I would like to achieve 6 amps with those, is it possible?


texts: Holes in RF shield, what frequencies can escape?

texts:
So this is part of a theoretical design problem that I've come across not too long ago, and still can't find a satisfactory answer for it.
Assume a large (infinite) metal plane with a round hole in it of size \$d\$.
Further assume an RF transmitter one side of the hole, and a receiver on the other, some distance away from that hole. In case the diameter is zero (no hole) the attenuation of the screen is 100%, and if the screen is gone, the attenuation is only dependent on the distance between the transmitter and the receiver (I'm assuming omnidirectional transmitter elements and receivers here).
Now, to my understanding, how much of the RF energy is passed through the hole is dependent on how large the hole is in relation to the wavelength. In my mind, the hole will act like a screen, but it will also cause the wave pattern to refract. However, as I understand it, the hole needs to be at least \$\dfrac{\lambda}{2}\$ in diameter, otherwise the attenuation will be extremely high. Am I right in this assumption? And what is the general correlation with screens like this, for instance, depending on the polarity, a square hole might let some RF through in one orientation and not in the other, but what about CW and CCW polarized RF?
I'm perfectly happy with a bunch of pointers to resource material I can read myself up on.
Thanks!


texts:
I am working to create a portable educational element display (about 2 meters wide) along the lines of this one at Griffith Observatory:
http://www.griffithobservatory.org/exhibits/hallofthesky_elements.html

I wish to be able to use a tablet app (which I will write) to allow one to select any of about 90 elements, have the corresponding display box light up with a couple of LEDs (one to illuminate the sample, one to light up the symbol) while the app displays detailed information about the element and samples.

The original uses about 90 push buttons directly wired to each display box. I want to use a wireless connection (or a single Ethernet cable).

I an not a hardware person and do not have a good idea about how to go about this. Commercial wireless switches I find are completely unsuitable, intended for high power control of one or a few circuits, expensive (when you need to buy 90) and far too bulky and impractical to control.

It seems that something like this is on the right track:
https://makezine.com/projects/construct-giant-led-video-screen/
using controllers for LED strips to make a sign -- except that LED strips don't work here as each box is individually wired not part of a strip.


texts:
I have been working on an application which must read

32 analog channels
at least 200kS per second.
0 to +3.3V
12 bit resolution
1% accuracy

I've come up with 2 potential solutions:

32 ADC independent channels in STM32F303-familly MCU
an analog multiplexer ADG732.

I'm aware that the implementation using a MCU would be way harder. What are potential problems in both methods.

Which solution looks better in your opinion?


texts:
I would like to know your opinion what are existing solutions for building a small (<5W) UHF TV transmitter. The problem is every circuit or schematics I find already uses separate audio/video input, whereas I already have modulated RF signal coming from a TV modulator like this: https://www.ebay.com/itm/PAL-B-G-Composite-RCA-Video-Audio-To-PAL-B-G-RF-UHF-VHF-CATV-Modulator-/192160908653, so in the end I have 75 Ohm compatible signal already.
So the questions are:

Can I just hook up something like this
https://www.ebay.com/p/533392191 just to transmit signal
aerial?
Do I need to use a wideband amplifier because I also want
to use a stereo sound (MTS/NICAM/A2)?
Wouldn't it be simpler to
design RF modulator + amplifier from scratch to overcome
aforementioned issues?

Thanks a lot!


texts: Question about Non-isolated Buck Converter

texts:
I have a tutorial problem about buck converter with MOSFET, anyone can help?

During the test of the non-isolated buck converter (see the circuit below), when we measure the gate signal, there is an output current from the power supply even without applying the gate voltage to the MOSFET ? Please explain the reason and give one solution.

I suggest the problem is the Zener diode or reverse current, but have no ideas at the moment.


texts: branch address computation single-cycle vs multi-cycle vs pipeline risc-v

texts:
I'm not sure about at which stage do the address computation take place at each of the versions of the risc-v?

I just wanted to make sure i got that right-
Single-cycle risc-v: Branch target address computation happens at Execute stage
multi-cycle risc-v: Branch target address computation happens at Decode stage
Pipeline risc-v: Branch target address computation happens at Execute stage

Thank you!


texts: 74HC08 Quad 2 input and gate Not working

texts:
I am absolute beginner and I purchased SN74HC08 Quad 2 input AND gate . Hoping it will work as expected I connected it to the breadboard and used the 1A and 1B inputs connected to a push button and the 1Y output connected to a LED with a 220ohm resistor to the ground. The Vcc and GND are connected properly using Arduino 5V and GND pins.
But when I power the circuit the LED is always high. it doesn't seem to care about the inputs. When I read the datasheet and some articles, they say that all unused pins must be either Vcc or GND. I did as per the instructions but still the gate wont work. I finally decided to post this question on SO.

If you see the attached image the Vcc on the IC is not connected and neither are the 1A and 1B inputs. all other pins are connected to Vcc and GND pin to ground. but the LED is still on.

Please help me I confused as to why this doesn't work. Did I damage the IC??


texts: In STM32, How to check the UART Serial Buffer If They Are Available using HAL Library

texts:
I am using STM32F429 in my project which connects to an ATmega2560 thru UART. In arduino, there is a function Serial.Available() to check if the serial buffer is empty or not.
Is there a function in STM32 that is similar to Serial.Available() in Arduino?
BTW, I am using HAL libraries in STM32CubeIDE and HAL_UART_Receive(huart, pData, Size, Timeout) to read the contents of UART buffer.
Please help. Thanks!
PS. I've read the documentation in HAL library but I'm not sure if there is one. I've looked into HAL_UART_GetState but Im not sure.


texts: Circuits for Multiplying two Analogue Signals - AM Modulation

texts:
I've recently been learning about various communication topics and modulation schemes. One of the most basic is Amplitude Modulation and DSB-SC. Both of these modulation schemes (in addition to numerous others) require the use of a multiplication block.

What sort of basic physical circuits can be used to multiply two analogue signals? For example in AM modulation.

I know Op-Amps can be used as weighted summers, integrators and differentiators  - can op-amps be used to implement an analogue multiplier? If so, are there any particular op-amp parameters which are particularly critical in multiplier design?


texts:
I want to know specification for CHADeMO standard,its a fast charging method for electric vehicle upto 400 kW preparing 900 kW on the map.I tried searching data for CHADeMO but just found above information.
Anyone can share their experience on how it works?


texts:
I'm a new learner in signal processing. I've got a problem in understanding impulse response.

For a LTI system, the output of the combination of impulses equals the combination of every individual output of each impulse. My question is that can I say for every specified LTI system, the impulse response function is fixed due to the nature of this system?

My understanding about this problem is that for input impulse delta[n-k] there is a corresponding h[n-k], which means when delta[n] is shifted by k, and the h[n] will also be shifted by k, and the h(n) function curve are the same but shifted, right?


texts: H bridge with a single I/O control and NPN at the top

texts:
I want to control a 4V motor to rotate both directions which draws 100mA and I was looking at the H-bridge schematics. The tutorial says that you should place NPN transistors at the bottom if you need >5V Power to the motor, which i dont need. This H-bridge also requires at least two inputs to switch direction. I also do not need to turn the motor off. It will run either or one direction, or the other.
I was wondering if I could put the NPN transistor at the top, so that I can control the motor with only one I/O pin (simplified schematic):

simulate this circuit – Schematic created using CircuitLab
Since I don't need >5V power for the motor, I don't need to put my NPN transistors at the bottom.
Using this schematic I can also control the direction of the motor with only one I/O, without more external components.
Of course, the complete schematic will also include a resistor to limit the Base current and the fly back diodes (fly back diodes and Base resistor added):

simulate this circuit
When I/O is 5V, both NPN transistors turn on.
When I/O is 0V, both PNP transistors turn on.
Do you think this will work? I have not seen any tutorial/schematic with this H-bridge configuration.


texts:
I'm trying to write a loop for two binary values that repeat periodically at a specific amount of time that goes indefinitely or until a certain condition is met.

Here is what I have wrote (below), but the error states that I should be using the 'wait' statement with 'until' but when I use that then it says that the Boolean expression is used incorrectly.

This leads me to believe I'm using the loop wrong or doing something else wrong that I can't figure out.

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity moove is
    port (clk : in std_logic;
        rst : in std_logic;
        count : out unsigned (7 downto 0));
end entity;

architecture moving of moove is
    constant period : time := 19.5 ms;
    constant cycles : integer := 120000;
begin
    forwrd: process (clk)
    begin
        if rising_edge(clk) then
            if rst = '1' then
                count <= "00000000";
            elsif rst = '0' then
                for i in 1 to cycles loop
                    count <= "01100100";
                    wait for period;
                    count <= "10010110";
                    wait for period;
                end loop;
            end if;
        end if;
    end process;
end architecture;


texts: LEDs in Parallel, each with its own resistor

texts:
I am currently planning a project to light up a model of a cruise ship. I've done this before with some success.

To keep things simple I want to wire in Parallel. (Assuming I've understood the difference correctly; Each LED will have a direct connection to the power source)

I will be using a mix of colours; White, Warm White, Blue, Red, Green. Every LED is pre-wired or will be fitted with a resistor (470) to allow them to be run from a 12v source.

Every online simulation I run and my own previous experience says this will work perfectly fine, but every article I read seems to scream "no don't do it" and even then, opinions seem to differ.

Above is an example of my wiring diagram, forgive the crudity. There will be a lot more LEDs used than this, but this gives you an idea of my plans.

Any thoughts?

Thanks

{{{}}}

EDIT:

This is the overall schematic that I have planned:

Sadly I cannot provide the direct link for this circuit as it is too long for browsers apparently.


texts: First metal detector by Alexander Graham Bell, how did it work?

texts:
Alexander Graham Bell developed a similar device (metal detector) to
  attempt to locate a bullet lodged in the chest of American President
  James Garfield in 1881; the metal detector worked correctly but the
  attempt was unsuccessful because the metal coil spring bed Garfield
  was lying on confused the detector.

From wikipedia.

But how did this early metal detector work? There was no vacuum tube or transistor available to build an oscillator or amplifier. I can't imagine such a detector using DC current only.

Did Bell use a mechanical DC/AC converter like an induction coil?


texts: Closing the loop and creating the current in antennas

texts:
I remember Feynman explained that raid waves are emitted by accelerated charged particles. So, the only the things that antenna transmitters do is just up-down oscillation of the current

simulate this circuit – Schematic created using CircuitLab

Since this wire vertical, oscillation should create the the photons flying away horizontally in all directions. But how do you close the loop? The wire cannot be infinitely long. Does it mean that you must emit the same amount of radiation in perpendicular direction? Probably it is good that you produce the bi-polarized signal, which is easier to detect. You have to wire the backward vertical current at the right distance (half wavelength) so that it is coherent and does not interfere negatively with first one at large distances. But donesn't its radiation affect the current in the first wire (and vice versa)? Can you ever have an electron oscillation in the wire without the loop? Since most antennas that I have seen are unclosed wires, I believe that you can. But, how is that ever possible?


texts: I made my first PCB with slots, and Altium is generation two .txt files...one for the drills, and one for the slots...how do I combine them to send it to the manufacture?


texts: Exclude certain module from optimization in Xilinx ISE 14.4

texts:
I'm synthesizing a quite large design in Xilinx ISE 14.4 and would like to exclude certain modules from optimization. Is that possible?

The design I'm synthesizing is the LEON3 microprocessor. I have modified the Integer Unit pipeline to implement triple modular redundancy. The problem is that the additional registers I have added, are being removed again by the optimization.

There seems to be a global synthesis option "remove-equivalent-registers". I have tried to turn this off and it worked for the module I have modified. But maybe this might lead to some strange behavior in other modules. So I actually would like to activate this options just for the module I modified myself.


texts: Why would I use 2N3904 instead of 2N4401?

texts: 2N3904 and 2N4401 appear to be very comparable parts in all specs. 2N4401 has a higher current rating, but otherwise they look to be about the same in price and everything else. Obviously it's difficult to give a 100% universal answer since both parts are made by multiple manufacturers. But insofar as it is possible to say, is there any reason one would use a 2N3904 instead of a 2N4401?


texts: Half bridge voltage waveform not following PWM

texts:
I am making a 12 V battery charger getting power from 220V AC. The topology is half bridge with capacitor voltage divider, as shown in the SG3525 datasheet.
While initial testing on vero-board, the voltage at the midpoint of half bridge remains high after the pulse of the high MOSFET and remains low after the pulse of low MOSFET. This makes it a 50% square-wave regardless of the duty cycle from SG3525A. A similar square wave appears on the secondaries.
I want to have control on output voltage and current, so need to have duty cycle in my (SG3525A's) hand.
Can anyone figure out what's causing the problem?

The gate driver worked so perfectly, I was amazed myself. Only it had quite an overshoot at edges and lots of ringing. Both of these problems went away when I connected a 3.3k resistor between gate and source and a 33 Ohm in series with gate.
The specs I am working with are as follows.

Vin: 220 VAC, 50 Hz
Vout: 12-14 V
Iout: 0-4 A
Topology: Half bridge with forward converter
PWM controller: SG3525A
Frequency: 55 kHz
Switches: IRF840
Core: #40 EE Ferrite
Primary: 60 turns of SWG25 wire
Secondary: 10+10 turns center tapped of 6xSWG25 wires
Aux: 10 turns SWG25 wire
Voltage divider capacitors: 220 uF each, with 470 kOhm in parallel to each

When testing the circuit with resistive load on Aux, 24 V DC at input and about 40% duty cycle on the SG3525A, I get the following waveforms. The Aux has just a full-wave rectifier and a 100 uF filter capacitor.
Edit: I placed a resistor in series with the primary winding of T2, so now I have the current waveforms for the primary. The voltage and current waveforms for the primary and secondary of T2, when analyzed together, may give a better picture of what's happening in the transformer.
In the following, yellow is gate-source voltage of lower MOSFET, blue is voltage at half bridge mid point (probe at 10x). Aux is loaded with 100 mA.

In the following, yellow is gate-source voltage of lower MOSFET, blue is voltage at capacitors midpoint (probe at 10x). Aux is loaded with 100 mA.

In the following, yellow is gate-source voltage of lower MOSFET, blue is voltage at midpoint of half bridge (probe at 10x). No load is connected.

The following diagram shows primary current and voltage at different duty cycles under moderate load. The voltage probe is at 10x setting.

The following diagram shows primary and secondary voltage at different duty cycles under moderate load. A resistive load is connected to the secondary, so the current is same as the  voltage. The secondary voltage probe is at 10x setting.


texts: Basic Theory - finding voltage between two points

texts:
I'm a neophyte here trying to learn using "Practical Electronics for Inventors, 4th Edition" (which received almost a 5 star review with over 500 reviews on Amazon).  The preface of the book states "little to no experience" in electronics needed to understand the concepts in the book.

Alas, I'm struggling on the Theory chapter less than 20 pages in.  When asked to solve the below questions.  The book presents a few sentences which are relevant, but not enough for me to understand and solve the questions posed after.

The book states (and I believe I understand) the idea that Voltage is the measurement between two points usually provided by an absolute scale which is often set at 0 on the negative terminal (ground reference).  This is at least true for the DC circuits discussed.  The illustrations show (with enough clarity) an example of the V between the positive and negative of a single 1.5V battery, two batteries in series (3V), and finally an example of a split supply with a common return - a ground reference between the positive and negative leads of the two batteries.  While I don't understand all the ramifications of this yet, I understand the basic explanation.

Several pages later the following questions are posed, along with the answers which I am having a lot of trouble following.  I understand they are trying to show some examples that don't have a ground reference and/or that the ground reference is either at the positive or negative end, but lack of a walkthrough of prior examples is leaving me stumped.  Furthermore there is a possibility based on this question that the book may be incorrect - which would be very disappointing as it is hard enough for me as it is.

Any insight into how to help me interpret these answers or clarification on the basic theory being illustrated below is appreciated:


texts: I have a project where I want to be able to cook food (very similar to a crock pot).  What would anybody here recommend to use to convert AC to useable DC and what should I use to heat the food?  Should I use cartridge heaters?  How many watts would be OK?  Also, I would need to turn on/off the heating element so what should I watch out for?


texts: Output voltage at transistor of given figure

texts:
Can anyone give me hint of this question. I know this is homework question. I know correct answer is 10 v.

But if I tried to solve it like this way:

(1) Z1 and Z2 limit output 5 V and Z3 and  Z4 will give output 5 V. So total output is 10 v. And it will be subtracted from 15 v so output should be wrong.


texts: DTV Data from IEEE 802.22 Meeting in May 2006

texts:
I am currently working on some signal sensing algorithms. In various papers I have come across the reference to DTV signal data that they used for their simulations, amongst others: Reference number 21
They led me to this web page, which seems to be an official repository with all meeting documents of the IEEE 802.22 working group.
Going into the May 2006 directory leads me to this page, where the top entry is probably what I am looking for.
There should be a FTP link to some DTV data. However, the only link present there takes me to this page, where only graphical plots and some meta information about the DTV data is available, but no signal data files.
The guy who allegedly took these samples seems to be called Victor Tawil and used to work for a company called MSTV. A powerpoint with more info about the signal data but no data or link is here.
If any of you know where I can find that signal data (it is most likely going to be IQ-data stored as stereo channels inside a WAV file) or have any idea what to do next, please let me know.
Thank you
PS: I have already tried emailing Victor


texts: Procedure for experimentally determining decoupling capability?

texts:
I'm looking for a bullet-point list of a technique to experimentally determine a design's decoupling capability.

I have a design that I'm working on that seems to be susceptible to ESD events in the field. I can't change the PCB layout - but I'm thinking of doing a BOM change and replacing some decoupling capacitors with TVS diodes on the power rails.

I'd like to remove the capacitors and verify in the lab that the design still has sufficient decoupling.

The design has:

Altera Cyclone FPGA (32.768MHz)
Microchip PIC (Internal OSC - 8MHz)
Marvell Ethernet PHY (25MHz)

I have a 200MHz DSO 'scope in my lab.  Do I just put a probe on a supply rail and trigger on large spikes, and if it never triggers after running through worst-case tests, it will be OK?


texts:
I recently bought a tubescreamer PCB from Tonelab and soldered it together yesterday. I decided to go for Ts-9 model which requires (Ra=470ohm, Rb = 100kohm, Ca = unused) I tried to match all parts as close as possible .. some of the capacitors and resistors are a tad off (eg: 47pf  instead of 51pf) but I figure it won't matter too much.
All solder joints seem fine to me, no short circuits etc.

So anyway I power the circuit up and there's absolutely no output. I tried trouble shooting with the limited equipment I have (multimeter only)..

Checked all obvious things like battery, jacks, leads etc and they all seem fine.
So I took a piece of wire and shorted the input and output together and I obviously got a clean signal coming through. I then followed on from the input  going from 1st cap straight to output(still a signal) to 1st resistor (still a signal) but when get to transistor no output whatsoever so matter what terminal is used.

The voltmeter shows voltages at these points so I'm slightly confused.
Also voltmeter shows no voltage across Ra but shows approximately 2 volts across 10k to left of it.

Can somebody please direct me in right area so I can fix this?


texts: Running 4.5v LED string from 12v leisure battery

texts:
I have a string of 20 LEDs designed to run from 3x AA batteries in series.
I plan to hook these up to a 12v leisure battery.
Until recently I had always concentrated on getting the voltage right (supply voltage = sum of forward voltage of components) but understand there is the issue of current to consider, which is the part that confuses me slightly.
I purchased a L7805vc voltage regulator and hooked it up, the LEDs work fine but I want to ensure my maths are correct.
The problem is I have no idea what the LEDs are rated.
If I read the multimeter correctly I get 5v and 170ma which is only 8.5ma per LED?
For comparison to the 3x AA, I get 3.9v and 110ma (though they may not be brand new).
Is this fine or do I need to add a resistor somewhere, or do I need to know the LED rating to be sure?
I did try reading other questions but can't seem to find a similar enough answer to my situation.
Thanks


texts: How to choose R and C to reduce noise on analog input of arduino?

texts:
I'm not terribly proficient when it comes to hardware, so please bear with me.

I've tried to google around to figure out how to choose values for a low pass filter to reduce noise on a potentiometer. Most of the articles I have read explain how to choose values based on frequency characteristics. That is a reasonable approach when you have that information.

In this situation, my digital input on an arduino is modulated by a potentiometer and I am seeing the values bouncing around a lot between 1 and zero when it's around the threshold. I would like to implement a low pass filter, but I am not sure how to choose my values since it's not clear to me what the frequency band I want to filter is (I do not have an oscilloscope).

This problem feels fairly simple, and so far i've seen a bunch of arduino tutorials to 'just implement a low pass filter'. But what I'm looking for is, how would an electric engineer approach choosing the right values for R and C given they are seeing a noisy analog input?

Also, this is not a question about any specific circuit I've built, this is more a general question about how to build low pass filters in practice.

Edit: Here is a bit more information.

I'm using an LM35 sensor, which operated in the \${mV}\$ range. The temperature from the sensor is \$\frac{output(mV)}{10mV}\$ so 400mV would be 40.0 degrees C. I wanted to use the potentiometer to modulate a 0-450 mV value to feed to a comparator (LM393) to determine whether the temperature is greater than some adjustable threshold. In order to set the Vcc pin of the potentiometer, I used a voltage divider \$\frac{10kΩ}{100kΩ + 10kΩ} * 5V = .454V = 454mV\$

The circuit looks like this, and \${V_{out}}\$ is going into one of the arduino digital inputs. I also feed the inputs of the comparators to analog inputs for inspection, and the potentiometer input bounces around quite a bit.


texts:
I've searched Google and couldn't find a simple answer to this question. I'm guessing the only limiting factor is the solder's melting temperature? I don't think I should have a problem with < 20A, but now I'm just curious about this. I know the resistance of solder is calculated from its total area, but that isn't exactly easy to calculate. So I guess I'm going for more anecdotal evidence.

Anyone have experience using solder joints for high currents?

edit: Sorry, I meant for longer tracks of solder (oops)


texts: How to drive a 20mA LED From a 4mA max GPIO Pin

texts:
I have an IC that has an GPIO with which I would like to drive a LED.

Since the device will be running off battery, keeping the power use low (Zero maybe) while the LED is off as a priority.

The GPIO supplies 3.3V when turned on and 0.0V votes when turned off.

It also has a limit of a maximum of 4mA.

The LED has a forward current of 20mA and a desired forward voltage of 2.0V.

When the LED is turned on it will most likely be blinking (using PWM) in the low kilohertz range.

After poking around I believe this may be the type of circuit I need.

Question 1: Am I even close to being on the right track.

Question 2: What is the correct component to use for item (5), (Transistor or  Mosfet), and how do I go about finding one (at the local Frys, RadioShack, Online) and how are they identified(specified)?

Question 3: Will the choice of item (5) have any effect on the ohm value of the resistor item (3)?  Apart from the normal Ohms law for the 3.0V power source and the 2.0V LED.

Question 4: What would be the ohm value of the resistor item (2), if any is required.


texts:
I am new to PCB design, and especially on Altium. I am trying out it and have no clue of the best way to fix the following error:

I am trying to build a PCB for a Li-Ion charging circuit based on BQ24072. I have downloaded the symbol, footprint and 3D model from Texas Instrument's website. My manufacturer says they need a minimum of 0.08mm clearance between 2 pads mask. Here is the snapshot of 2D and 3D view of my PCB. What is the best way to overcome this issue?


texts:
I was discussing with a friend about maximum output power of a (class A/B power) amplifier (for example if the device following the PA can only tolerate a certain amount of power).

If the input power is much smaller than the output power, all the output power will come from the power supply and and maximum possible output is given by drain current times supply voltage (DC power).

However, when it comes to efficiency, there is a figure "Power Added Efficiency" which subtracts the input power (as compared to the drain efficiency). In a similar manner, can the input power be transferred to the output (in addition to the power coming from the supply) under all conditions or is the input power always dissipated into heat?

Example: Class AB amplifier, Vsupply=5V, IDmax=100mA, P1dB=23dBm, Pinmax(no,damage)=25dBm. Is the maximum possible output power 0.5W (27dBm) under all conditions or can it be higher?


texts: How to design circuits to work under -55 Celsius degree?

texts:
Possible related post:Warming PCB in a low temperature environment

I am trying to design a circuit which should work properly under -55 degree. There are two options in front of me: to choose specific components and carefully design the circuits to fulfill the environment requirements, or to heat the circuit up.

After searching the internet for a while, I decide to choose the second one, due to the complexity of our circuit. It would be easier just to heat the system up.

Here comes some of my initial thoughts, which are contributed by the mentioned post.

The circuit shall be divided into two parts: heating part and the functional part. The heating part is to create a suitable environment for the functional part. The functional part can only work properly, say, above +10 degree.
The functional part shall not work when the temperature is below +10 degree. It shall wait until the heater heat up the environment.
An analog temperature sensor like this one will be used to measure the environment. It will control a 1*2 switch: one end system power, the other end heat up circuit OR the functional circuit.

My questions:

Could I get some comments? Or any better designs?
How should I calculate the number of heat-up resistors?
How to calculate the heat-up power needed?
Some sort of heat-isolation material shall be used. How to find them?


texts: What are the major sources of noise in a system

texts:
This question is a follow up on the question about the inductor choice for power supply noise filtering. One of the inductor's parameters was frequency response curve. To use this, I would need to have information about potential noise sources in the system and their magnitude.
In general, what are the major "noise makers" in a system, based on which I should select choking inductors (uCs, ADCs, DACs, DSPs, CPLDs, FPGAs, clock oscillators, etc.). How to estimate the noise in the system?


texts:
[EDITED] I ALSO ADDED THE LAMP TO MY DESIGN WHICH I FORGOT
I am trying to use a MIC29712 in constant current mode to draw 4A for my lamp. The power supply is 15V and can give up to 8A.
Here is the MIC29712 datasheet.
What I think I can do is this:
Since the ADJ Reference is to GND, I will tie the Vout to ADJ, so the Vout will be 1.240V (Vref), hence the V1 will be 1.240.

simulate this circuit – Schematic created using CircuitLab
Does this look correct? I ordered the parts and waiting for them to arrive.
I am asking becouse I could not find any constant current schematic for this regulator. I am mainly worried about the ADJ pin. Is it really referenced to GND (I think this is the case,) or is it referenced to Vout?


texts:
I want to make a simple USB device consisting of a webcam and some LEDs. The webcam will detect a human face using some software I've glued together (thanks, predator algorithm), and it will send a signal to the microcontroller to smoothly transition the LEDs from red to blue. I know how to do it with Arduino Uno and a webcam, but I want to find some good, cheap parts to substitute in.

For instance, what kind of micrcontroller do I need (a good, cheap one)? Do I need a USB hub to split between the microcontroller and webcam or is some other method preferable? What kind of webcam do I need? It should be small and cheap - high resolution or great picture quality isn't important.

Please help a software engineer who's an electronics n00b!


texts: How to interface Touch module with ESP 01

texts:
I am trying to interface a touch module with the ESP WiFi module on GPIO0 pin. When I turn ON ESP it needs GPIO0 to be pulled up but if I directly connect the Touch module, its output is low at start up and hence ESP goes into boot mode. To circumvent this I put a simple transistor inverter in between so that I invert the touch module output. That way GPIO0 is always high during start up.
Now this solution works fine except in practical place where this needs installation. When I installed it within the housing of mains switch board, the touch module gets triggered when I switch ON other switches in the same housing. The relay turning ON or OFF also triggers the touch input. I think this is because the base of the transistor is very sensitive in this configuration and hence captures any stray signal. The whole set up works fine if the circuit is away from the mains switch board. I have even removed the connection to the touch module, it still gets triggered which indicates that it is happening because of the transistor.
Can somebody suggest to me how can I modify this circuit to avoid this false triggering.


texts: How do precision differential levels achieve such high accuracy

texts:
As you do, I was watching a video about levelling granite surface plates used in precision machine shops and labs. They're ground and lapped to a high level of flatness (I think AA plates are flat to within around 0.005mm) and a key tool for this process is a set of electronic differential levels like these.
These devices are used to measure the relative inclination of different parts of the plate and the paths are integrated to give a map of global roughness across the plate. The manufacturers of these levels claim that they can measure .1 arcseconds repeatably. If I did the maths right, across a 1m surface plate that corresponds to vertical displacement of 4.8e-7m.
My question is, how do these things work? I'm not electronic engineer but I assume each unit contains a (hinged or flexible) pendulum ~0.1m in length with capacitive plates on both sides charged from an AC source. As the pendulum flexes or rotates around the hinge, the relative change in capacitance between the plates on either side would result in a voltage difference between the two capacitors that you could then feed into an amplifier to measure the change in pendulum displacement and thus the change in the orientation of the level. Combine this with another level as shown in the video and you can measure the relative change in orientation between the units.
I've left some of the maths in here for you lot to enjoy working out for yourselves but if anyone has an idea of what the circuitry looks like inside these things, I'd like to know whether my assumption was even close. I've been playing around with a circuit sim to try and build something that can measure very small changes in relative capacitance but alas, I've got nothing that really works.


texts: Do analog circuits exist that are essentially mathematical functions in DC?

texts:
I am curious if a class of analog circuits exist that would take say a 0-5 V input signal and output a mathematical function like a sine function mapping 0-5 V to 0-2pi, or a log, exponent, polynomial? I could see the associated coefficients also being DC analog inputs, say

V_out = V1 * V_in ^ 2 + V2 * V_in + V3

I know op-amps can be configured as differentiators, integrators, adders, multipliers, so one way might be to have a high frequency oscillator working with these components to do a DC-AC-DC type conversion, but this seems overcomplicated.


texts: How to calculate the maximum voltage of square signal from Erms?

texts: How do you calculate the maximum  oltage from Erms when you have dc and ac component?


texts: I am new to PCB design and need help in the battery management part. I am currently designing a PCB which is to be powered by a battery and this battery can be recharged by a micro-USB via a linear charge management controller, MCP73811/2. Can this component also control the flow of current when the microcontroller is being powered by this battery and be charged at the same time or do I need another component for that? Please let me know if I am not clear enough and I thank you in advance.


texts:
While looking into some custom built CPUs I've noticed the frequencies at which they operate are relatively low compared to modern CPUs (in the order of several MHz). Is there an electronics engineering reason for that limitation, e.g. for breadboards?
If yes, how to determine the max frequency that is possible to achieve with your design?


texts:
I have a simple circuit shown in the diagram; the capacitor shown in red across the power supply terminals is not in the circuit at this time.

The momentary toggle sw at the top connects to both, either the set of the reset coil of a latching relay as well as a solenoid in the model railroad switch (turnout).  The turnouts require a momentary pulse to switch and I am using the latching relay to drive either of two LEDs to indicate the turnout direction.
Now, the problem is that the turnouts switch without fail, but the latching relay does not always flop.  I'm wondering if the turnout solenoid is drawing too much current for the DC supply to keep its voltage up and thus denying the latching relay the opportunity to react.
My question is:  Would the addition of the capacitor help?


texts: Difference between MOSFET cascode and MOSFET in series

texts:
When using two MOSFETs in the cascode configuration the output resistance is approximated as gm × ro1 × ro2 where gm is the transconductance of the top device, ro1 the drain source resistance of the top device and ro2 is the drain source resistance of the bottom device. This increases the output resistance of the combination.
However MOSFETs are also used in series while holding Vgs of both the same  so that effectively the channel length is doubled and the current in the combination is halved. This would be similar to saying that the output resistance has doubled.
I'm not able to understand this. Does the output resistance increase by a factor of 2 or ro2?
Please help.


texts: My school is a technical school that used to make ham radio communications (AM, I think). The thing is, we have a huge antenna that isn't being used. So, could we use it as a WiFi antenna?


texts: What is the use of CLK125 on Ethernet PHY?

texts:
We are working on a KSZ9031 Ethernet PHY with a Zynq 7020.
I don't know where connect the CLK125 signal on a Zynq 7020.
What is the use of this signal ?

Thanks,
Jeff


texts:
I'm tasked with finding the unity gain frequency of an op-amp using the datasheet specs provided to me (just a homework exercise, not a real op-amp). There is no direct spec given for "Unity Gain Frequency" or "Unity Gain Bandwidth" or "Gain Bandwidth Product", but it does provide a spec for "rise-time" (0.3 uS typical) as well as "slew rate at unity-gain" (0.5 V/uS typical).

I know there is a formula that shows that the bandwidth can be approximated by 0.35/tr, but I guess I'm not really understanding which rise time to use. In my mind, isn't rise-time and slew rate almost the same thing? If the rise time is defined as the time it takes to go from 10% to 90%, shouldn't the slew rate give me the same result? If I had a waveform move from 0V to 1V, it would take 1uS per the slew rate. 80% of that would give 0.8uS

Can someone help to determine which to use (rise time or slew rate)?? And maybe explain why there is a difference


texts: How is register access done in case of X86 architecture when there is only In and OUT command for ports?

texts: In ARM architecture the registers of a peripheral are mapped to the RAM so we can access the register using the RAM.


texts: KCL and KVL with Laplace incorrect result

texts:
For t > 0 find v0(t)

Using nodal analysis I was found v1 and v2, take difference and find correct result

But I can’t make same with direct KCL, KVL approach

May anyone help with that?


texts:
I have a situation where my polygon looks like the teeth of a comb. I don't want to have multiple polygons and I don't want to manually route the shapes.
I'd like to make one "tooth" and then just duplicate it across and where the polygons overlap, merge them into one.

I can't seem to find an option where I can merge polygons together and I would think that this would be built into the software.


texts:
I want to construct a matrix of smart boards that receive ethernet packets, decode them, and place the decoded results onto a memory "matrix" for other boards to process and re-transmit. Given the available technologies, I suspect PCIe is the way to go. I have a couple of questions for you all:

1) Who controls the PCIe bus? I suspect its the (PC) motherboard processor at a high level, and the PCIe controller at a lower level, but its not clear.

2) Is PCIe designed for lots of small transfers, or a fewer number or larger transfers? I suspect the latter, as the former would kill the motherboard cpu...

What do you think?


texts:
As im learning about Computer Architecture im trying to understand it from the ground up (Transistors in CMOS in particular)

I came across the simple 6T schematic for SRAM (2 inverters)

Mostly makes sense, but I have a few questions. What exactly is being done with whatever is stored here? Is it being sent to the CPU? a Decoder?....etc...? I'd assume we use some sort of decoder/encoder to write to specific cells?

And while I understand how the Memory Cell works (Keeps it's data from feedback) are we reading the Cells contents with the Word lines or Bit Lines? what about writing to them? Is the ~Bit Line (~BL) completely useless to us?

Like how would I go about reading and writing to an array like this?


texts: Can you use a the vout of a regulator as the cathode and your full voltage as anode?

texts: I have a servo from an rc car with 6 wires, it turns out the servo controller is built into the RC Car with a bad board. I have a motor, a gear box and a 10k pot attached to it. I'm trying to build a modified H-Bridge with an opamp. For my circuit I need negative voltage. My question is if I use the output of a 5V Regulator as Gnd, the source anode as + Voltage, would the source anode then be usable as - voltage. My idea is that I could take my battery source of 10v, use a 5v regulator and have postive 5v, negative 5v and gnd. Feed the negative and positive into a pwm controlled opamp, connected to a half h bridge and finally powering the tiny dc motor. I also think maybe I should add a diode to the motor to prevent negative voltage coming back across the circuit.


texts: I have got a a2212/13t 1000kv brush less motor in a quadcopter which is running the propeller. I have to use that then how can I know that those motors are working?


texts: Bit overrun and framing errors when receiving from PIC18F4680 EUSART

texts:
I'm trying to receive data from PIC18F4680's EUSART (using C18 compiler) module and if I type characters in my terminal emulator slow enough, like one or two characters per second, reception works fine. If I try to transmit several characters quickly it seems that reception stops and only device reset solves the problem. Transmission works fine.

The serial port is running at 115200 b/s and   and is set-up using following code (clock is 40 MHz):

OpenUSART (USART_TX_INT_OFF & USART_RX_INT_OFF & USART_ASYNCH_MODE &
            USART_EIGHT_BIT & USART_CONT_RX & USART_BRGH_HIGH, f_usart);
//f_usart=86 for 40 MHz, 115200, or 1040 for 9600 (but it doesn't work at 9600)
    baudUSART(BAUD_16_BIT_RATE&BAUD_WAKEUP_OFF&BAUD_AUTO_OFF);

Here's the code I'm using to read from the port:

  if(DataRdyUSART())
  {
      temp=ReadUSART();
      WriteUSART(temp);

  }

This code is in a main loop which does some other processing too and sends out data over serial port. I don't expect this piece of code to work too good (I'm just testing to see if loopback works fine), since there's chance that it will miss some characters (or at least I think so, since a new character may be received before there's a chance for old one to be processed), but I didn't expect it to not work at all.

Interesting thing is that if I enable the Rx interrupt and put the exact same code in the ISR, the data can be received at much greater speed. I need to paste text into terminal window in order to cause the problem.

So any ideas what could be happening?

UPDATE

Looks like I'm getting a mix of framing errors and bit overrun errors. I don't think that I can make the data processing in this case much faster to get rid of the overrun errors, so I'll probably slow down the serial port, but I'm not sure what to do about framing errors.

UPDATE 2

At 9600 b/s, I get much less errors, but still if I copy a wall of text into the terminal, I get errors.

UPDATE 3

Looks like my laptop's USB to serial adapter is transmitting at 9900 b/s. Could that be the cause of the problem? If yes, is there anything I can do on the PIC side to help solve the problem other than setting the data rate at 9900 b/s?


texts: Linux (OS) on Custom Hardware (Custom Motherboard)

texts:
We are designing and producing our custom high-speed boards consisting of FPGA and gigabit ethernet signals. Hence, we are not professional for high-speed motherboard design but know some issues like signal integrity and other PCB design staff.

We have a new control application and this time we are planning to design our own motherboard. The first prototype is made by using a raspberry pi and an Arduino mega boards. We programmed both devices in order to control some slave devices. We used the well known Raspbian OS based on Debian and wrote scripts for it.

We have never designed a motherboard before, but fortunately, there are many fully open-source motherboard PCB designs (including Raspberry except firmware).

I guess we may not be able to use the same Debian (like Raspbian) and kernel on our custom hardware since kernel must be changed because of the GPIO and other registers, instructions etc.. We will not clone any of the board designs, we will modify maybe the microprocessor brand or indeed the core architecture (like not A53 but A9) or using NXP brand relying on the base design.

Question is, (I am not a software guy, hence I connect the wires, calculate impedances, lengths etc but not load anything on those devices), might generic distributions of Linux and the related kernel and bootloaders be used for our custom motherboard (like Ubuntu or Debian?)? I searched and heard something about Yocto Project, which says have no dependency on the embedded system. I am still searching for this.

Could anybody explain in some more details and concepts on this issue?

Kind regards.


texts: Charge indicator with comparator - very sensitive to noise

texts:
I need an indicator when the current from my charger is larger than 100mA. I tried the below circuit but this seems very sensitivity to noise. Probably I am getting some ripple in the mV range from the charger.
Is there a more robust, less sensitive way to set this up?


texts:
I am trying to simulate a JK latch in a circuit builder. What I have come up with thus far is the following:

I don't have control of the wiring (the application automatically does these wirings, often convoluted or hard to read), and so I'm having a bit of trouble debugging the circuit to see what is wrong. Additionally, the app doesn't support a three input AND gate, so I'm using 2 AND gates to simulate that, for example:

Regardless of what logic input I change, the output does not ever change. What seems to be wrong with my circuit here?

Additionally, here's an example using Logicly where I get something very similar: https://gyazo.com/6d594c52b21e2c4208dc6872ca1a9e8d.


texts: How to connect a fast recovery diode with 3 pins?

texts:
I have a fast recovery diode, part number D30FD60K, I would like to know how I have to connect it. The diode will be used as the return path in parallel with a fuse. Like shown in the diagram.

Pin 3 will go to the switch, but I don't know how to connect 1 and 2. And why is a NC on pin 1? Is that normally closed, how does it open?

simulate this circuit – Schematic created using CircuitLab


texts: How can the signal strength of an RF signal be measured?

texts: I am a graduating ECE student and we are currently making our project study. Our group would like to make a proximity indicator. Initially, we planned to use Radio Frequency for this. The idea was to measure the signal strength of the output signal in terms of voltage. We were to use AD8313 to be able to convert the db output signal to voltage. Unfortunately, our component has not yet arrived and we are forced to look for alternative ways. Could you please suggest other ways on how to accomplish this?


texts: Can this Fritzing diagram be simplified to share a single hole?

texts:
I'm playing with my first circuit for my home automation.  I am following this circuit diagram.  It seems to me that I can just combine all 4 legs into the same hole? (the + side of the capacitor, 1 leg of both resistors, the 1 screw terminal)?  I am re-creating this using a perfboard where none of the holes are electrically connected.

Am I wrong in this?  I watched a youtube video on them building this circuit and they indeed did different holes and bridged them together with solder.  Sorry if this is a dumb question, this was a hard one to google.

Row H is the red GPIO36 port of the esp32.
Spot F-10 is +3.3volts
I combined D4 legs all together but didn't have room for the clamp leg too so I bonded it on the other side via C4-D4.
D1 is ground


texts: How to generate Duty Cycle from DC without 555

texts:
I am currently working on a simple circuit which includes creating duty cycle from DC. Also, I need to change it's pulse width with time. I have decided to use op-amp relaxation oscillator to produce square waves but I have no idea how to chance it's width. I am allowed to use resistors, capacitors, inductors, diodes, OPAPs, transistors and relays.

My question is how can I create a circuit which produces duty cycle and it's pulse width is changing with time as shown at the picture above.


texts: Can a NOT gate be used to achieve 180 degree phase shift?

texts:
I have seen from various sources which say that a NOT gate cannot be used to achieve an 180-degree phase shift. Is this claim true?

Edit: The question is definitely sounding unclear because that is how it was worded, but one thing I missed was it was asked in the context related to FPGA's. So I assume we are dealing with digital signals here. Anyways giving a sine wave as an input to the NOT gate would change the shape of the output itself so I guess there would be no question of comparing/calculating the phase difference.
The solution given was to use a DCM in an FPGA and it was explicitly mentioned not to use a NOT gate, but I don't understand why it won't work because inverting a wave is definitely an 180-degree phase change right? Please correct me if I'm wrong!


texts: Confused with electrostatic pickup and capacitive coupling terms

texts:
I can understand the meaning of capacitive coupling of the signal line to GND or Earth or nearby earthed objects. Below line section illustrates that:

But there is also a term called “electrostatic pickup”. I guess it means the same thing with above.(?)

And texts tell us if the signal is low, to prevent electrostatic pickup coaxial cables are used.

I don’t really understand why it is called electrostatic pickup. What is static here? Capacitors do not pass static current as well. Why does the coaxial cable prevent electric field but not magnetic field?

Im completely confused about the distinction even though I know what electric field and magnetic field means.

Some even claims that “Hi, to answer to you question, you must know that coaxial cable is not able to protect against low frequency EM disturbance, whatever its kind (magnetic/electric)”


texts: Make a forward from one UART to another UART

texts:
I am working with the TI TM4C MCU. Connected to one UART of this MCU, I have a GSM module or a GPS Module (let's say UART1). I need to establish communication between the MCU and the module by sending some "AT commands" and receiving some replies to verify what the module is doing.

Therefore I need to see what AT commands are sent by the MCU to the module and I need to see what the module replies to the MCU. Of course those commands are defined via C files, but I need to check what is sent when and how and what is received when and how.

I suppose that I can not use CCS to visualize those data flow, correct?

Therefore to achieve this, I am thinking to use MCU UART0 and connect that to my computer, where I use "Tera Term" software to receive a copy of what is sent and received by the MCU on UART1.

I am not an expert in C but I have some notion of it. I found some example of UART use in the TI lab workshop for TM4C, but I am not sure fully about how to implement this "forwarding" (copy like). I think I need to copy the value in the FIFO/ buffer of the UART1 to UART0 and then sent them to UART0.

I am a bit confused about how to operate it.

I would appreciate if someone got experience about it to explain how you usually process to analyze sending and receiving of data via UART, which are not directly linked to a computer terminal.


texts:
I want to use Power over Ethernet (48V, 30W best case) to power something that's going to require up to 15W at 10V. That means I need to step down the PoE voltage but step UP the max current. As I understand it, a buck converter will have the input current off part of the time, so I would lose potential power. A linear supply obviously would not do.

I need efficiency in the usual sense, that the supply will not waste too much power. But with the input limited in current, I need the thing putting out current nearly full-time. Would a large capacitor on the input of my step-down converter do the trick?


texts: Measure indcutor ripple current in a SMPS

texts: I need to measure the ripple current in a buck converter. In general, I add leads to the inductor and use a current probe. My issue now is that the inductor I am using has such a low inductance that the leads are almost doubling the total inductance. If I can't use a current probe, I would prefer to make the measurement with only one voltage probe. The only way I can think to do this is add a high precision resistor between my output capacitor and ground. I'm concerned though that in order to get an acceptable resolution from my oscilloscope, the resistor will be large enough that it adds substantial voltage ripple at the output. Are there any other methods anyone has had success with?


texts: using ultrasonic sonar and mist maker together

texts: I have made a cold steam bucket (ultrasonic mist maker). now i want to add automatic water level indication system for it using ultrasonic sonar module. i want to know if both mist maker ultrasonic and sonar are working at the same time, would the mist maker affect the sonar precision? I mean they both make ultrasound waves right? is it possible that when sonar is waiting for response, the mist maker affect it before the sent wave came back to sonar?


texts: How to use level-triggered interrupts with STM32F1xx?

texts:
I'm getting conflicting info on whether I can use level-triggered (as opposed to edge-triggered) interrupts with the STM32F1xx microcontroller.

In ST's CMSIS-compliant Standard Peripheral Libraries, the trigger options
are defined in enum EXTITrigger_TypeDef, which only includes EXTI_Trigger_Rising, EXTI_Trigger_Falling, and EXTI_Trigger_Rising_Falling. (no mention of level-triggered interrupts)

According to ST's help forums here and here, one well-known user says that ST only does edge-triggered interrupts.

Also, ST's RM0008 Reference Manual doesn't make mention of level-triggered interrupts.

On the other hand:

ST's PM0056 Programming Manual, Section 4.3, states that:

The NVIC supports (...) Level and pulse detection of interrupt signals

The same document, Section 4.3.9, gives more detail about level-triggered and edge-triggered interrupts.

And the official ARM documentation, Section 4.2.9 says:

A Cortex-M3 device can support both level-sensitive and pulse interrupts.
Pulse interrupts are also described as edge-triggered interrupts.
(...) A level-sensitive interrupt is held asserted until the peripheral
deasserts the interrupt signal.

However, I cannot find any way to actually set this up.  I don't mind bypassing the Standard Peripheral Libraries, but I don't even see any appropriate registers to use...

I'm my specific case, I'm interfacing to another IC via SPI. It is a complex SOC, and it drives an output pin to signal that it needs attention. It communicates with it's "driver", which is hosted on the STM32. The SOC and driver want edge-triggering.

How can I configure the STM32F1xx to use level-triggered interrupts?


texts: how to obtain the parameters of the step response within matlab in open loop?

texts:
I have step response in open loop of my model that i stored in workspace and I want to use Matlab to obtain the: T time constant, L dead time and  A (see figure below).is there a command for that like the stepinfo?

 I have used it and as I am using a plant, I simulated the plant with step input and I did save the output Vout in timeseries as you showed me previously and made this script:

time=Vout.Time;  % x
Y=Vout.Data;   % y
For K, use the final value of Y
K = Y(end);
L_index = find(Y>=.05*K,1);
L = time(L_index);
T_index = find(Y>=(1-exp(-1))*K,1);
T = time(T_index);
D = diff(Y)./diff(time);
inflex = find(diff(D)./diff(time(1:end-1))<0,1);
A = D(inflex)*time(inflex)-Y(inflex);

tangent = D(inflex)*time - A;
plot(time,Y), hold on, plot(time,tangent), plot(L,Y(L_index),'*'),
plot(T,Y(T_index),'*')

it calculated every parameters (L,T and A) but the result look like:  description here does the modification i included are right despite not seeing the tangent?


texts: Possible source of a 120Hz noise on ADC?

texts:
I have a photodiode connected to an ADC through a current to voltage converter (opa376 opamp).

I'm getting this 120Hz noise/interference. I would expect 60Hz main noise and maybe some 2nd harmonic at 120Hz but not 120Hz Only.

What could be the source of this signal?

 16bit, Sample rate ~15kHz.


texts: Problems with programming STM32L mcu with stm32cubeIDE (failed to erase memory)

texts:
I am trying to program a STM32L152R8 MCU with stm32cubeIDE v1.4. The MCU is not brand-new and is soldered on a board. I want to change its firmware.
While debugging with ST-Link Debugger I encounter the following error:
Memory Programming ...

Opening and parsing file: ST-LINK_GDB_server_a07132.srec

 File         : ST-LINK_GDB_server_a07132.srec

 Size         : 9052 Bytes

 Address      : 0x08000000

Erasing memory corresponding to segment 0:

Error: Flash loader cannot be loaded

Error: failed to erase memory

Encountered Error when opening E:\ST\STM32CubeIDE_1.3.0\STM32CubeIDE\plugins\com.st.stm32cube.ide.mcu.externaltools.cubeprogrammer.win32_1.3.0.202002181050\tools\bin\STM32_Programmer_CLI.exe

Error in STM32CubeProgrammer

Debugger connection lost.

Shutting down...

Notes:

The reset pin is connected,
I've tried to mass erase the chip using st-link utility,
OpenOCD works but the live expression is disabled,
Keil uVision and ST-Link Utility work fine without any problems

Any ideas?


texts: What is the equivalent resistance of the circuit below?

texts: I want to use a method to simplify this circuit to reach it's equivalent resistance.Do you have any idea?I don't want to use directly mesh and node method.


texts: Are there any types of DC motors that self-lock themselves?

texts: I have a small DC gear motor which spools a plastic line. Once I've engaged the motor to tighten the line, I want to lock it in place so that the line doesn't unspool. I would then like it to remain in this position mechanically so that I do not have to apply holding current. When I'm ready to release the line, I'd then like to be able to electrically reverse the process and disengage the lock. Is there a standard design that fits this requirement?


texts: Monitor coin cell voltage without loading it when power is off

texts:
Is there a good way to monitor a CR2032 coin cell's voltage, that does not load it down when other power is off?

We are using a CR2032 coin cell for a battery-backed real-time clock.  When main power is on, I want the (ARM) processor to measure the coin cell voltage to within 100mV or better to detect a 'coin cell failure' condition.  ADC channels are available.

When main power is off, the average measurement circuit loading must not exceed 1uA to avoid discharging the coin cell, and the measurement circuit must not charge the cell.

Desired coin cell lifetime is 10 years.  Typical draw is currently 1.2uA, which uses 105mAh of the 240mAh capacity.  Aging eats another 10%.  Component variations, higher temperature and humidity, any board contamination may cause earlier failure.

Hoping for something fairly compact and inexpensive.

Edit:  there is not enough room for a relay.


texts:
I connected 10x Lithium Ion batteries in series (3.7V, 2100mAh), I looked into the datasheet and the charging voltage is 4.2V with a current of 1A.
Can I simply solder this battery management system to the battery string and connect it to a 42V 2A charger to safely charge it or will it blow up?


texts:
How worried should I be if I route wider than 10 mil trace to 0805 pad?

Would 16, 20 or 24 mil trace cause soldering problems without making 10 mil neck?


texts:
While fixing another problem, Im noticing that some of traces are broken. The board was 90% routed, and now some of those completed traces are incomplete, like as if there was a small break in them.

What can cause that ? And how do I stop it ?

edit
I attached this image to show what I meant. I couldn't wait for an answer, so I had to manually connect the broken traces again, so for this image, I broke the connection to show what it looked it.

The trace was routed in full before, and then after some "change", a few of my traces looked like the image below.


texts: frequency response -- for linear regulator

texts:
In a linear regulator on input side digital voltage enters (say DC 60V ) & on the o/p side digital voltage(let say DC 15V) is produced.

What exactly do we mean by the frequency response of the Linear Regulator in this link.
http://www.onmyphd.com/?p=voltage.regulators.linear.series&ckattempt=1

Device which take a DC voltage as input and a DC voltage as output, then why this factor Frequency is in frequency response. What i know is frequency is related to time varing AC signals, but here linear regulator is dealing with DC voltage ?


texts:
Hi,
This is an extract from MT-021 from Analog Devices about SAR ADCs. In particular, it shows a circuit in which the Track(Sample) and Hold block of the SAR architecture AND the DAC of the SAR architecture are implemented as one.

My question is : The description/circuit is explaining about the operation of the DAC but if you read the highlighted sentance, it says "The comparator then makes the MSB bit decision". If this is operating as DAC, why do we need to make an MSB bit decision, shouldn't we already know the bits if it's a digital to analog converter?

https://www.analog.com/media/en/training-seminars/tutorials/MT-021.pdf


texts: Pulldown for transistor + digital pullup?

texts:
I'm just created this circuit:

With this I first regulate the voltage from +12VDC down to +3.3 VDC [1), purple]. Then I have two parts:
Blue [2)]:
ESP01_01 controls transitor U4 which inverts the signal from GPIO2 (=J3 pin 2) and GPIO0 (=J3 pin 3) and U5 toggles the L296 motor driver power supply. This inverting is necessary because GPIO2 and GPIO0 need to be HIGH while booting. Also the signals from ESP01_01 (GPIO2, GPIO0) are used to send a signal to the motor driver for controlling the rotation direction of the motor. This signal is inverted by Q1 and Q2.
All this works properly - my question is: Do I need to set a pulldown resistor for Q1 and Q2 to have LOW signal by default? The collectors are not connected to anything because I didn't find a L296 for fritzing.
The third part, light blue [3)] is not mounted yet. This is a second ESP8266 (ESP01_02) which receives signals from two reed-switches (S1, S2). Since GPIO2 and GPIO0 need to be HIGH while booting I thought I use a pullup resistor for each switch - my question is: Can I substitute these resistors by setting the GPIOs as INPUT_PULLUP?
If something is wrong with this circuit, please let me know - I'm very new to electronics and so I'm glad to get improvement suggestions!


texts:
I'm trying to dim a light fixture with the DALI protocol. It functions quite fine but when the dimming gets low two thirds of the LED:s turn of.
Why is this?

Is it because the voltage forward gets to low to support all the LED:s? The driver that is used is constant current so it should be able to supply the voltage?


texts: Hybrid \$\pi\$ Model vs. T-Model Input Resistance (MOSFET)

texts: If the hybrid-\$\pi\$ model and T-Model are equivalent models, why does the hybrid-\$\pi\$ model have an infinite input impedance and the T model has an input impedance of \$1/g_m\$ assuming \$\alpha=1\$.


texts: Phototransistor with virtual ground opamp design

texts:
I am setting up a high sensitivity light detection circuit and came across this thread just a bit ago:

Phototransistor transimpedance amplifier

Within it was a response with this image:

My question is this:
Should the phototransistor in the diagram above be connected to the true ground coming from the power supply or to the virtual ground?

Thank you and I know this may seem like a newbie question and perhaps similarly asked in other threads, but it doesnt seem to have been explaind in my opinion.


texts: Considerations for transmitting the signal from a MEMS microphone over a short cable?

texts:
In my application I have the signals from 6 analog MEMS microphones (CUI Devices CMM-3729AT-42108-TR), each amplified by a pair of op-amps in a voltage follower -> inverting amp configuration. The microphones are on tiny PCBs buried deep within a chemical analysis cavity, and the only way to get the signals out is through a short cable (150mm, conductors are +3V3, SIGNAL, and GND). After amplification, it's off to an ADC to be digitized, and then I'm demodulating the signal to sniff out the amplitude of a ~1500 Hz signal.

Due to the stupidly small space I have to deal with (can't change the geometry of the analysis cavity), I'm prototyping with the Molex PicoBlade system. DigiKey sells pre-fabricated cable assemblies, but they're all unshielded. Many of the cables are touching each other.

Should I be considering a way to shield the cables? The DC blocking capacitor is near the op-amp end of things, so the signal on the SIGNAL wire will be biased around +550 mV. This can be changed, I can move the DC blocking cap closer to the microphone if recommended. If I should be shielding, what're some recommendations for that?

Did I miss anything else in the circuit? The microphones each have power supply bypass caps very close to them (though not shown in the circuit I've included). The output impedance of the microphones is 300 ohms at 1 kHz. How does that interact with the input impedance of the op-amp?


texts:
Folks, Hopefully this is the right place to ask this. I'm a software engineer with VERY limited EE experience and am trying to learn. At the moment, I've got a project that I'm trying to power using a 6v 6w solar panel, a load sharing solar battery charger, and a battery - though for this issue the battery is not in the loop. I'm also using a low drop out linear voltage regulator since based on the sun, voltages from the panel could vary.

Solar Charger

LDO (3.3v)

When I plug the solar panel into the charger and take a voltmeter to the output leads, I get something nice and consistent around 5v (the panel is not in full sun at the moment). However as soon as I attach the voltage regulator (without any load) the voltage output from the charger goes pretty haywire jumping from 0 to 5. The output from the voltage regulator is around 1.8 or so. This definitely doesn't power my project since it needs 3.3v.

I'm using all purchased parts - didn't really design any circuit myself. The part list is above. Anybody know what is happening or how to get a consistent output? Thanks


texts: How would one design a circuit to swtich between external power source and a battery?

texts:
I have a circuit that normally runs off of a 12V power brick that I want to make somewhat mobile. As such, I plan to use a 12V battery to power the circuit but, when the battery depletes, I would like the ability to plug the circuit to a 12V DC power supply that would not only charge the battery but would also supply the circuit with power.

The circuit that I want to power is actually a 4 meter long LED strip that I used to make a lighting panel. I intend to make this panel more mobile for whenever I need it to be so I can easily move it around without worrying about the cable. However, in case the battery runs out, I still want to be able to run the panel from a wall plug and, in the mean time, also charge up the battery.

To sum it up, these are the 2 use cases for what I am after:

If the external power supply is unplugged, the lighting panel will run solely off of the battery.
If the external power supply is plugged, the lighting panel will run (ideally) solely off of the external power supply which would also charge up the battery in parallel.
When I don't need the panel to be mobile I would like to keep it plugged in so the battery won't discharge but still use the external supply to power the strip.

Currently, I have not looked into any specific type of battery / charger. This is all still in the design phase and I first want to have a plan set up before I think of the specifications of the parts I will be using. For now, the only specific characteristic will be the 12V for the supply and battery and also the LED strip. I am not sure how much current the 12V supply will need to provide or how much the charger and the strip will draw when running simultaneously. Once I have an appropriate circuit, I will look for the parts that suit my needs. I should mention that I will want a battery and charger combo.

Here is the first circuit that I came up with:

I tried to keep it simple and not use any transistor, just a couple of diodes.

First off, the charger will have 4 terminals and is represented by the 4 pin header. The inner 2 pins represent the power in for the charger and the outer 2 pins represent the terminals of the charger that connect to the terminals of the battery.

The D3 diode prevents the current flow from the external supply to the battery, and the second diode, D2, is used when disconnecting the power supply from the circuit to prevent any current flow from the battery to the charger. I don't think it is really necessary, especially if the charger is any good, but it's there just for good measure.

My concerns are regarding the common ground that the battery, charger and external supply share as I'm not entirely sure how it would all work, and also I'm unsure if the circuit will draw current from the battery once the external supply is connected. While it is charging, the battery will probably provide a lower voltage than the external supply so the strip will probably draw its current from the external supply but what about when the battery is fully charged? Will the strip also draw current from the battery? How will that affect the charger / battery?

I am not yet sure as to what battery I will be using but I will probably go with a LiPo battery pack and the appropriate charger (I will probably buy a combo from the same manufacturer). In the case of a LiPo there may be a third terminal between the battery and the charger.

What are your suggestions regarding my design or perhaps there is a better alternative that I have not thought of that you might be able to suggest?

Are there any safe practices that I have overlooked or is there any standard circuit that would accomplish what it is I am trying to achieve?

EDIT: I would also like to get at least 2 hours of full brightness use out of the LEDs.


texts:
I have a circuit that controls a fan linearly. I have a PWM output going through a low pass filter and into an NPN transistor for low side control.

It worked well with at first, however when I switched to a different fan there was a lot of pulsing a lower PWM.  The fan starts spinning, and then a some point it turns off and then starts spinning right away. When I look at the collector voltage (Node A) with a scope it looks like the signal in image 2.

Because I don't want the fan at full speed I expect the voltage across the transistor to be high, and get to 0 when the fan is fully on. What is happening instead though, as the fan starts spinning the voltage across the transistor gradually increases (and so does fan speed) and then when it hits the peak it turns off and starts again. The higher the PWM the slower the pulsing interval. At some point though when the PWM is high enough the fans spins normally, but I would like it to spin at a lower PWM than that as well.

The solution that I have for this at the moment is kind of ugly. I added a capacitor across the fan and it seems to fix the problem. Not exactly, but it allows me to get to low enough PWM that I can use it.

It only masks the issue and it's also a massive capacitor. The capacitor stops the pulsing and keeps the voltage across the transistor constant.
I have tried adding a diode instead of the capacitor but the issue still persists.
This is what the signal looks with the capacitor added.

My primary goal is to understand what exactly is happening, and then obviously how to fix it.

The fan itself is a 12V, 3 wire, brushless fan, 0.33A rated current. It has auto restart and polarity protection. I tested with a power supply by ramping up the voltage to make sure it's not the fan and it works fine.


texts:
I came across this image of an induction

Does anyone have any idea, on how to select the big Coil in the middle, and where can I buy it.


texts:
I am trying to design a microstrip Wilkinson power divider in ADS for 2.4GHz. My schematic is shown below:

The calculations all check out but I am not getting the best RL at 2.4GHz:

If anyone could help figure out what is going on that would be great


texts: What was the communication protocol used on board the Apollo moon lander?

texts:
It seems that the development of TTL was contemporary ~1961 the maiden moon landing of the Apollo vehicle, while the development of one of the oldest digital signalling standards RS232 using the UART hardware was crystallized later, and that of the advent of the USB hardware, transmission standard and related communication protocols occurred much later.

What was the communication protocol used on the controllers and processers on board the Apollo lander vehicle?


texts:
I have an Atmel ATmega328P using a 14-Bit MAXIM MAX544 DAC.

I have the ADC configured and running at 38kHz in running mode while the SPI is clocked at 4 MHz. I feel this should be more than equate for a 4 kHz + signal.

Is my DAC bottle necking here?
Why is my signal looking at that as its under sampling?  And:
why isn't the 4.3 kHz signal not looking like the 50Hz one?

Figure 1: Sin Wave: 50Hz

Figure 2: Sin Wave: 4.4kHz

Figure 3: SinWave: 20kHz
   EDIT: The positive cycle is only present due to no biasing being implemented.

#include <SPI.h>;

unsigned short x;

void setup() {
  DDRD |= 0x08;
  DDRB |= 0x04;
  DDRC |= 0x00;
  PORTD |= 0x08;

  ADMUX = 0x00;
  ADCSRA = 0xAD;
  ADCSRB = 0x00;
  ADCSRA |= 0x40;

  SPI.begin();
  SPI.setBitOrder (MSBFIRST);
  PORTB = 0x04;
}

ISR(ADC_vect) {
   x = ADCL | (ADCH << 8);
   PORTB = 0x00;
   SPI.transfer(x);
   PORTB = 0x04;
}

void loop() {}


texts: Can I use masking tape for 12V max insulation?

texts: Hello. Would it work if I put masking tape over a solder joint as insulation which would carry 12V max? I'm connecting a general-purpose 3-12V AC adapter to some wires. Any help would be appreciated. Thanks.


texts: Power Supply Design w/Transformer - Not Enough Current

texts:
I am testing the following power supply which steps down from 230VAC to 12VDC.

When testing without T1 and supplying 39VDC instead of the rectifier, the switch-mode power supply (TPS5401) outputs 12V and 50mA can be drawn continuously. When testing with T1 and the bridge rectifier, the bridge rectifier outputs 39VDC and unloaded the switch-mode output is 12V but upon trying to draw 50mA from the 12V, the output drops to around 2V with the bridge rectifier remaining at 39VDC. How can I ensure that the transformer is suitable for my current draws?
Transformer Specifications:

230V-15V AC, 1.8VA. Measured (unloaded) : 28.2V AC
For 230VAC, no load peak voltage, Vsec peak = 35.5V
For 230VAC, full load peak voltage, Vsec peak = 19V at 70 degrees Celsius

Thanks


texts:
I made a custom Footprint, whenever I try to link to a schematic library, Altium refuse and just pop a random footprint instead.

What are the reasons that could lead altium to refuse to load a footprint?

Here the image of the footprint:


texts: Why is BER higher for binary modulation compared to quaternary?

texts: I came across this image in my notes and I fail to understand why BER seems to decrease as the modulation order increases and I was hoping for an answer


texts: Noise with TPA3110D2 amplifier on the same power supply as an USB HUB

texts:
I have a TPA3110D2-based, XH-A232 amplifier board powered by a 12V switching supply (S-120W-12V). The input is the headphone output of a monitor connected to a PC.

I would like to power an USB HUB from the same power supply. However, when the HUB is powered and I connect it to any of the USB ports of the PC, a high-pitched noise appears on the speakers.

If I power the USB HUB from its own power supply, the noise goes away. If I apply a capacitor of 1uF..100uF on the input, the noise also goes away, but the sound becomes much quiter and treble is lost as well.

What could be the cause of this noise? What could be done to eliminate the noise, but still be able to power the amplifier and the HUB from the same power source.


texts: How does a servo amplifier with Step/Dir Interface calculate feed-forward terms?

texts:
My Question is related only to servo systems that still use step/dir as input.

Consider a typical advanced servo loop of an amplifier in  the figure below:

(source: "Mechatronics system Control and logic" book by Robert Bishop)

A motion Card (not showen here) will generate a profile based on selected acc , dec , speed etc.. then this profile will be translated into a series of pulses with varing frequency.

The Amplifier can easily count the number of pulses to feed the position loop using for example internal quadrature decoder / or counter.

Now for the question : How does the amplifier caluculate the Required Acceleration and Velocity feedforward from the pulse train input ? or is this only possible with field bus amplifiers ?

Thanks!