texts:
I have developed an application layer software which transmit 2560 bytes using UDP through Ethernet. I realise that the MTU of the Ethernet is 1500 bytes therefore I have reconfigured both MTU of sending/receiving end to 5102 as shown in the picture below:

The data is transmitted from a FPGA to the PC.
However, this is what I capture through Wireshark:

I receive the correct data I am sending but it gives the error that: BAD UDP LENGTH 2568 > IP PAYLOAD LENGTH Len=2560. The data that I am sending from the FPGA is 2560bytes.

May I know how can I reconfigure the IP PAYLOAD LENGTH?


texts: Low-pass filter on microcontroller output

texts:
I'm producing a signal which contains 7 frequencies using a microcontroller with a DAC. the frequencies are 16.5kHz 16.7kHz 16.9kHz 17.2kHz 17.4kHz 17.6kHz 17.8kHz. and sampling frequency (at the output) is 86kHz.
The signal from the mc is at is then decreased by two resistors (600R/2600R)and fed into
LM-386 (which increases the signal by 20) and then into a 4ohm Speaker.

Because of the generation method I get harmonics, aliasing and some parasitic low frequency of which I wish to get rid off.
I've calculated that for RC-LPF with Fc=20kHz I need 220nF and 34ohm however, when I put them just before the the (600R/2600R) resistors the whole signal seems to be attenuated significantly!

Am I doing something wrong here?
Thanks for the help!

EDIT:
The microcontroller is pic16F1783

here's the schematic:


texts: Does anyone have an STM32F example for opamp PGA mode (ideally STM32F3 Discovery)?

texts:
Ive used STM32cubemx to set input pin and output pin of OPAMP1.

Then open project in Keil and I can see the OPAMP functions are loaded and compile OK.

But when I load code into MCU (STM32F303 on Discovery Board) and feed small signal into the input pin (30mVAC sine on top of 100mVDC) the "output pin" on the MCU is floating, ie not operating like an opamp.

Do I have to enable something else? Thanks!


texts: Easiest project ever, but I still need straight answers. AA 1.5v x2 to RGB LED (trying to make white)

texts:
Ok so I pulled out some old electronics stuff I have laying around. I have two AA batteries in a holder, in series. I have common cathode RGB LEDs where you can find all their specs here.

So I plugged in the cathode in and started touching the other pins with a wire. Red works, blue works, and green works, rubbing blue and green is making teal, cool so how about white? all three connected just gives me red. After trying white green stopped working.. and eventually tapping blue does nothing or is very dim. I'm thinking maybe I did something wrong maybe too rough with the pins or something I pull out another and all are working again and eventually red's all thats lighting up. I start to think maybe I have the positive and negative thing backwards and switching them does the same thing. Is it normal that the red will work both ways? rubbing or tapping green or blue on and off will turn the color on for a millisecond. Seems to be a brighter flash of color when the electricity is jumping from the wire to the leg, but holding it on it wont do it. So holding it just far enough that the shock is constantly jumping seems to make blue/green flicker. Maybe too much information but I just think it's weird that it's doing that and doesnt seem to be burnt out or anything and that it works fine until I try to get white out of it. I was hoping that if I burnt something out it would be more obvious or instant instead of really having no sign of damage. So I'm thinking I'll need a resistor, I have a few in this box here. Batteries put 3.0v since in series, right? They're new from the store, Duracell MN1500 batteries. I'm now looking at the chart and it looks like I might need 3.2-3.5 volts to power green/blue? but it was working for a moment. If I'm trying to power white, do I need to add up the volts for each one or can I get all three up with the same voltage?

So my simple question is what circuit do I need to create here to get this thing to work for one night? I'm starting to think I need another battery in series with a resistor. If I jump up to 9v battery and resistor, will I achieve longer battery life?

Noob


texts: Output voltage of AT28C64B into HC CMOS IC

texts:
I am trying to load the output of a AT28C64B parallel EEPROM into a 74HC194 shift register. The datasheet for the AT28C64B states that the minimum high level output is 2.4V, which I believe is not enough to drive the input pins of the HC type shift register.

Therefor, I considered running the 74HC194 on 3.3V, and using a level shifter for the    other input. Then 2.4V should be enough.
But when doing measurement, I found that the actual output voltage from the AT28C64B was 4.8V, which is too much for the 74HC194 running on 3.3V.

The AT28C64B is powered with 5V.

So what should I expect the output voltage of the AT28C64B to be, and how can I ensure that the output voltage of the AT28C64B and the input voltage of the 74HC194 matches.


texts: How to solve this. Multiple op amps circuits in series

texts:
The question is. What value for R1 is correct if we want the total power amplification to become 30 dB

My calculations. 30dB is amplification of 1000 times.
Last circuit got amp of 15/1,5=10 times. 1000/10=100

We therefor need amp of first circuit to be 100 times.

10/R1=100

R1=0.1kohm

We could tick in 100 ohm but according to solutions manual the correct answer is 3.2kohm and I do not understand why.


texts: What is the real amount of reproducible colors on CRT display?

texts: Let's say, a generic consumer-level CRT. How much colors can it reproduce?


texts: I'd like to control a few input pins (say 5) and a few output pins (at least 2) from a computer. The computer has no parallel port. What is the best way to do this? USB-to-parallel adapter (anybody have one to recommend which works on Linux)? Or perhaps there is some other general purpose USB "control board" where I can use read input from some pins and write output to others? I don't even know what to google for, so any pointers are appreciated!


texts: What is this type of radio fm antenna connector called?

texts:
I'm looking for an antenna replacement for my dad's busted radio (iHome IH8) and I'm having some trouble finding the name of this type of plug. The only things I find when searching online are coaxial cables and more professional looking cables and nothing relevant for my needs.

The male connector is 6mm and the female is 8mm.

Here are some pictures.

Thanks for your help!


texts: Building an Immediate generator for my RISC-V cpu

texts:
I'm working on a simulation of an RISC-V cpu (in Logisim-Evolution, not the best, I know). But now, I have almost finished designing it (and so far it works like a charm), and now it is time to build it. (I have build and tested about 80% of my project so far) The issue I'm facing now, is how to design and build the Immediate Generator . This is my Immediate generator in Logisim-Evolution:

It works just fine, decoding every type of instruction in RISC-V (RV32I). But the problem is from which parts i should build it. The immediate encodings in RISC-V are sometimes tangled (like the UJ type or SB type), but I understand why. What they wanted to achieve is to use as few wires as possible, thus saving space. But, in my situation, I don't know how this could help me. My idea was that I would use 74HCT245 in TSSOP20 package (i have about 70 of them around me) to just simply wire each encoding type and then use the buffers (74HCT245) to act like an MUX (as shown in first picture). This leads to 5 * 4 = 20 ICs. This isn't a very lot, but this would be large on a 2 layer PCB. Can we optimize it a little more? Maybe how they intended? Should i use different ICs?

EDIT 1:
My design constrains:

build it using commonly found ICs (gates, plexers, etc..) not FPGAs, PlAs.
build it as small as possible :) (It needs to fit on 2 layer PCB 10*10cm MAX)


texts:
I am currently building a simple gain stage with an op-amp (MAX414CPD+-ND) following this circuit diagram

simulate this circuit – Schematic created using CircuitLab

By adjusting the 10K pot, I am able to amplify the input signal coming out as expected. This is good, however, there are some strange issues I've noticed:

If I increase the gain to a high value, the output signal gets amplified accordingly. However, if I power down my circuit and power it up again, the output signal is zero. (measuring with respect to ground).
In order to fix the above issue, I have to power down the circuit, re-adjust the 10K pot to a lower gain value (ie: x2 or x1.5) and power it up again. Afterwards, I see the voltage output is non-zero and amplified accordingly. I can then re-adjust the gain to a higher value.
I sometimes notice that if I power cycle with a few seconds of delay, the high-gain settings work again at start-up, but the longer I wait in between power cycles the more likely it is that it will not amplify and i'm forced to re-adjust the POT to a lower gain value.
To summarize: The main issue i'm seeing is that the op-amp cant startup with a "high" gain, I have to start at a lower setting. I took some measurements, it seems like when R2 is set to around 800 ohms this issue occurs (which i believe yields a gain of 5 = R2/R1 +1). Anything lower than this (ie: 400 ohms) then the circuit is able to startup fine and outputting a non-zero signal.

Is there a way to address this or is this a limitation I have to work with? Thoughts/comments appreciated.

Thanks


texts: To what extent can you mix button cell batteries?

texts:
I have a lot of different devices that are powered with batteries such as CR2032, CR2450N, CR3032... All of them are marked as 3V but they have different mAH values.

The local shops don't always have the appropriate battery so I have to purchase them online which I don't fancy doing. Can I use similar batteries as long as they are Lithium 3V and of equal size?


texts: VHDL: A function to determine array length

texts:
SOLVED!!! I'll leeave the questions, see below for the solution.

In a VHDL project, I want to initialized an array that have a certain dimension, and I want this dimension is derived by a function. Here is a minimal implementation that show what I want to do:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

use work.arrayout_type.all;

entity minimal is
  Port (
        a : in std_logic;
        b : out std_logic
         );
end minimal;

architecture Behavioral of minimal is
variable dimension : integer;
dimension := calc_adder_length(M);
type array_intern is array (dimension-1 downto 0) of std_logic_vector(M+N-1 downto 0);

begin

end Behavioral;

Here is the package (I edited the message and I included the two separate package in a unique package) :

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

package arrayout_type is
    constant N : integer := 8; -- first member is N bit long
    constant M : integer :=4; -- second member is M bit long
-- declaration of a TYPE of an array of M element, each element is a signal that is the output of the M shifters and the M-1 adders
    type array_out is array (M-1 downto 0) of std_logic_vector(M+N-1 downto 0);

end arrayout_type;

package body arrayout_type is
    -- calcluate the number of internal signal for the adders. Function body.
        function calc_adder_length (x : integer) return integer is
        variable number : integer;
        variable accumulator : integer;
        begin
        number := x;
        accumulator :=x;
        while(number > 1) loop
            if(number mod 2 /= 0) then
                number := number/2+1;
            else
                number := number/2;
            end if;
            accumulator := accumulator + number;
        end loop;
        accumulator := accumulator +1; -- finalization.
        return accumulator;
        end calc_adder_length;

end arrayout_type;

The problem is, of course, that I cannot call the program in the architecture body before the "begin". But at the same time I cannot declare the array_intern in the architeture after the "begin". So I don't know how to do.


texts: Help to understand/ explore small sized 3G and GPS Antenna Design

texts:
I recently came across an exciting device called Automile, from Sweden and what caught my eye is this -

I am really impressed by the packaging and overall quality of hardware integration they have done, and especially the 3G and GPS antennas that they have used.

I personally am a complete beginner for antenna design. Can someone please help me understand more about these antennas?
1) What are these Antennas called
2) What types of antennas are available for 3G
3) What is the fundamental theory behind it
4) How complex it is to make such an antenna

Hope to have an interesting discussion with you guys :)


texts:
I'm a bit confused about the concept of ground, and perhaps voltage as well, particularly when trying to analyze a circuit. When I learned about Ohm's law in grade school, I learned how to apply the law to calculate current, voltage, and resistance of simple circuits.

For instance, if we were given the following circuit:

We would be could be asked to calculate the current passing through the circuit. At the time, I'd simply compute (based on the rules given) 1.5V/1Ohms=1.5A.

Later on, however, I learned that the reason the voltage of the resistor would be 1.5V is because voltage is really the difference in potential between two points, and that the difference of the voltage across the battery would be the same as that of the resistor (correct me if I'm mistaken), or 1.5V. I got confused, however, after the introduction of the concept of ground.

The first time I tried to do the current calculation for a circuit similar to the previous circuit on a simulator, the program complained about not having a ground and "floating voltage sources". After a bit of searching, I learned that circuits need ground as a reference point or for safety reasons. It was mentioned in one explanation that one can pick any node for ground, although it's customary to design circuits so there is a "easy place" to pick ground.

Thus for this circuit

I picked ground at the bottom, but would it be okay to pick ground between the 7 ohm and 2 ohm resistor - or any other place? And what would be the difference when analyzing the circuit?

I've read that there are 3 typical ground symbols with different meanings - chassis ground, earth ground, and signal ground. A lot of circuits I've seen used in exercises either use earth ground or signal ground. What purpose is there in using earth ground? What is the signal ground connected to?

Another question: since the ground is at unknown potential, wouldn't there be current flowing to or from ground to the circuit? From what I've read we treat the ground as 0V, but wouldn't there be some sort of effect because of a difference in potential of the circuit and ground? Would the effect be different depending on what ground was used?

Finally: In nodal analysis, one customarily picks a ground at the negative terminal of the battery. However, when there are multiple voltage sources, some of them are "floating". What meaning does the voltage of a floating voltage source have?


texts: small sine wave with dc bias - translate to logic time signal

texts:
I have a time varying pressure sensor output signal from which I would like to obtain the cyclic frequency.  The signal originates from a reciprocating gas compressor therefore the voltage signal is a smooth and slightly distorted sine wave, frequency varies slowly from 0-10Hz, but is generally in a steady-state.

The sensor signal is 0-10Vdc, the amplitude is around 0.5V and the dc offset can be anywhere from 0.5 to 9.5v.

I would like to translate the small sine signal into a logic level square wave signal to be received by a microprocessor board (Arduino Uno) for frequency counting.

The approach that I'm thinking of is to shift the ac signal mean to 2.5Vdc, amplify the wave and feed through a Schmitt trigger (I have SN74HC14N)comparator.

I'm sure that this is a very common situation but I haven't found a book chapter to spell it out for the electronics novice.


texts: control 2 outputs with a single input and pid

texts:
Overview

I'm trying to levitate a constrained permanent magnet with 2 electromagnets. I'm having trouble conceptualizing the control system for such an operation.

Setup

The permanent magnet is fixed onto a horizontal arm and is repelled by an electromagnet above and repelled by an electromagnet below. The pendulum is attached to a rotary encoder that provides the absolute angle of the pendulum with respect to the horizontal.

Goal

Given a desired angle (relative to the horizontal), I need to change change the voltage going to each electromagnet. For example, if I want the pendulum to be at +X degrees, the control system would increase voltage to the electromagnet below the pendulum and decrease voltage to the electromagnet above the pendulum, resulting in a net upwards force.

Problem

I was advised to use a PID controller. I'd heard of, but never used, a PID controller, so I researched them a bit online, and I understand the general idea--it's just like somebody adjusting water temperature before showering. However, my intuition tells me that I cannot use a single PID loop to control the two electromagnets because I'd be using a single input to solve two outputs. It'd be like saying $$f(x) = y_{1}$$ and $$f(x) = y_{2}$$ where f is a linear function. Since that's not possible for a linear function--and PIDs are linear control systems--then I cannot control 2 motors with a single PID controller.

Am I right? If so, could you point me towards how people have solved similar problems? I feel like this is a common problem with control systems.

If I'm wrong, could you provide an example?

Many thanks!


texts:
At first I searched this problem and could not find anything with this specific.
I am using NE555 to generate frequencies. I'm using the calculations of this website. I am using 10nf as it says. My problem is I can't generate frequencies above the 100kHz.
I am using 0.1uF as C, 47ohm for both R1 and R2. According to the website, it should give 102kHz but NE555 does not give that. I measured it with an oscilloscope and it just shows noise. I searched [datasheet][3] and find out that NE555 should reach almost 1mHz.
What do you think my problem is? How can I solve it and reach the signals above 100kHz?


texts: arduino: turn on-off a 12V cpu fan with optocoupler

texts:
I wish to use a simple way to turn on-off a 4 wire cpu fan using a digital output of the Arduino board. Since even with PWM=0 the fan works at 30% of the full speed, i have to find a way to cut off the power of the fan.

I came across some tutorials describing the optocoupler 4N25, so I decided to give it a try. For that purpose I didn't use the Arduino itself, but two separate powers of 5V and 12V.

The schematic shows exactly what I did first, and it worked fine. The LED was turning on and off accordingly to the switching of the left hand cirquit.

simulate this circuit – Schematic created using CircuitLab

After that I tried to connect the two wires of the fan (ground and power) in the (4) and (5) pins of the optocoupler, but the fan failed to respond to the commands of the switch, actually it didn't start at all. I guess that I miss something there.

I also tried to ground pin 6 (ground) with no success.

This is the type of the fan I am using: http://www.formfactors.org/developer/specs/REV1_2_Public.pdf

Any suggestions would be appreciated

Thank you in advance


texts: How would one classify a ring oscillator?

texts: This may be obvious to some, but how would one classify a ring oscillator (see figure below of a ring oscillator)? For example, the Wikipedia page, https://en.wikipedia.org/wiki/Electronic_oscillator, has the ring oscillator under the relaxation oscillator heading. I would have thought a ring oscillator is more like a simple feedback oscillator where two of the gates can be merged and considered the amplifier and the third gate the feedback component. For a relaxation oscillator, I thought one needed a component that could be charged and repeatedly discharged by feedback? Any comments on this?


texts: Package on package and Flip chip what is the difference?

texts: I am confuse with Package on package and Flip chip. Are they classified as multi-chip modules (MCM)?


texts: Rather basic, but I can't figure out what exactly backup fuses are! I was studying a Weidmuller PRO ECO 120W 24V 5A power supply's datasheet (accessible via the catalogue page). It has recommended three types of backup fuse for input, but I can't find out what backup fuses are and why to connect them. I searched for it but it didn't help me that much!


texts: Modbus raw data COM capture file example?

texts:
I'm attempting to use a RS232 tap to sniff a serial connection between two devices that are communicating using Modbus RTU.

I'm looking for any capture files taken from sniffing a COM connection or port that contain Modbus RTU (or Modbus ASCII). I would like to compare the data files that I am capturing to other similar data files. Does anyone have any example Modbus capture files, or could point me to a website that hosts these?

Note that I am not interested in Modbus/TCP.


texts: How does a stm32f chip set its GPIO speed? (hardware, not register setting)

texts:
The speed of GPIO of a stm32 chip is set by register of OSPEEDR. It shows:

00: Low speed
01: Medium speed
10: Fast speed  (50MHz in library)
11: High speed  (100MHz in library)

My guess is that the speed is not related with the system clocks(AHB1) at all. It is just the physical property of the GPIO pin itself. Am I correct? Is it done by varying the output resistance of the pin or something?

The datasheet could be found here: http://www.st.com/stonline/stappl/resourceSelector/app?page=fullResourceSelector&doctype=datasheet&LineID=11


texts: How do I calculate the power output of a 12 unit trickle charger for mobile phones?

texts:
I'm trying to do some analysis on the power consumption of mobile phones, charged through a trickle charging unit. My scenario is as follows:

12x smartphones on a smartphone bay (wall).
1x Mains power point providing 230 V, 13 A
1x InVue security device with 12 micro USB charging points (note: this
system secures the handsets to the smartphone wall and is alarmed,
thus providing power for the alarm) This device provides a trickle
charge to connected handsets.

The InVue device reads that it has 5 V and 6 A on the back. Is it safe to assume that this generates 30 W or uses 30 W?

Therefore, I am trying to find out if this device is fit for purpose. The 12 handsets should all be on, with full brightness, connected to Wi-Fi (no GSM usage) and run rolling video content. However, this is not the case as at least 1/3 handsets have no power.

I am making the assumption that the device is not fit for purpose, but I would like to understand how i calculate the output of the InVue device. Can anyone help?


texts: Reading Array of Phototransistors With Raspberry Pi

texts:
For a project I'm working on, I need to read the values from a matrix of phototransistors (8x16) into the Raspberry Pi.

I'm not exactly sure how to go about doing this, since I know I need to include an ADC somewhere in there. If I use shift registers to read the values from the phototransistors, how can I incorporate the ADC in there?

The problem is the ADC interface. I'm looking at the MCP3008, which apparently uses an SPI style interface. If it was just a simple analog in -> digital out style interface, it wouldn't be a problem.


texts: Controlling which transistor turns on first in a multivibrator

texts:
I've managed to adapt a basic multivibrator circuit to contain 3 LEDs that blink in sequence, but I want to be able to control which LED lights first when it's turned on, so the same LED lights first every time.

Is it possible to bias which transistor turns on first by tweaking the values of the resistors or capacitor slightly on that part of the circuit?

Update 1

As requested, here is a crudely drawn circuit diagram:

R = 4.7k, r = 1k, C = 100uF, NPN Transistors

Update 2

So I downloaded LTSpice and figured out how to use it, but the 3 LED multivibrator doesn't work in it.  Here's the 2 LED version, which works as expected:

But when I extend it to add in the 3rd LED, it stops working:

However, I've built this on a breadboard and it works perfectly.


texts: Is CAN bus communications enough to update firmware?

texts:
I am going to control a few microcontroller-based units (approximately 30) from a master computer.
They are going to be connected using a CAN bus
The furthest lying unit may be approximately 10 meters away.
I need to update the microcontroller's firmware from the master computer.

Above are my requirements of the system. Now come my questions:

Is CAN bus communcations alone enough to update the firmware?
How long can CAN bus communications run?
Do I require a CAN transceiver or is the inbuilt thing is enough?
If not, what other options are there to update the microcontrollers from the master? (other ways than by a use of a CAN bus)

(I do not have a strong base in microcontrollers (though an Electronics and communication engineer)).


texts: Building a High Voltage Rectifier with a continuous negative output

texts:
simulate this circuit – Schematic created using CircuitLab

In the past, I have worked with high voltage projects, but seldom with HV rectifiers. Thus, I was curious how I could build a rectifier that could take 70 kV AC and 10 mA to put out a continuous, negative DC voltage with minimal ripples. The frequency for the input is 60 Hz and is provided by a X-ray transformer that provides adjustable voltage from 0-70 kV AC.

Note on image below: There was not an option for a variable transformer image, so I used a non-center tapped transformer to depict it.


texts: Practical implementation of state observer

texts: The state observer uses the measurements of the input and the output to provide an estimated of the system states. Let us assume that we have a controlled plant. Now, the output of the controller is a control signal. The control signal will go to the plant, as well as it will go to the state observer, so that the states of the system can be estimated. My question is: How can the same control signal go to the plant also and state observer also? Wont, it be divided into two parts , as it is going to two different places (plant and observer)? How can the same signal go to both the places?


texts: Color problems when turning a CRT TV set into an oscilloscope

texts:
I found an old CRT TV set in the garbage. It didn't work, always showing the "snow effect", even when I connected it to another device via the SCART port.

So I followed an online tutorial to make it into an oscilloscope. However, I encountered some problems. I'd like to know if they are likely to be resolvable or not, since I'm not an expert in this field.

There are four connections for the CRT that should control horizontal and vertical deflection. I disconnected the wires that control horizontal deflection and connected in their place those that previously controlled vertical deflection, in order to have a horizontal line at a scanning frequency of 60 Hz. Then I connected two wires for controlling the vertical deflection (at the other end of these wires I can put an audio output or just a battery). When these two wires are not connected to anything I should see a horizontal line.

What happens is that the horizontal line that should appear like a solid bright white line appears instead as a weak reddish line, as you can see in this picture:

horizontal line http://img259.imageshack.us/img259/6536/foto1yjz.jpg

The strange thing is that I tried with a friend to connect and disconnect the four wires to the CRT when it was powered on and, apart from the sparks, the process of connecting and disconnecting those wires resulted in a white bright line as it should be.

Even when all the wires for horizontal and vertical deflection are disconnected a weak red point appears and only with active manipulation performed when the device is on I manage to see a bright white dot instead.

I'd like to know if this behavior is due to the TV set being defective and is not easy to repair, or if it is somehow my fault and it is easily solvable.


texts:
I have a bandpass filter with tunable central frequency but the problem with this filter is that as I tune the central frequency its gain for different central frequencies is different. Is there a way to design a inverse filter for nullifying the effect of non uniform filter. I plan to pass the output of the bandpass filter trough this inverse filer.

Thanks :)


texts:
I want to check my Li-ion Charger( Microchip MCP73833 ) status with nRF52832.

So i will connect Stat 1,2 and PG to nRF
But MCP73833 have an open-drain output

If i connect pins to nRF without Pull-UP resistor and use nRF's internal pull-up is it ok ?


texts:
I built a monostable multivibrator circuit with a 7555 chip.
It has 1MΩ and 4.7μF components for timing, giving a pulse width of 5.17 seconds. It also has an RC on the trigger with 10kΩ and 0.33μF for a time constant of 3.3ms, allowing it to trigger at power on. Power is provided by a 5V signal.
Everything looks happy and as expected, for the most part, except there is a weird situation that I can't seem to get a handle on.
For example, here I'm using a pulse function generator on the input. This input is a single power input for the VCC and trigger/timer RC filters. When I bring the 5V signal high for ~2 seconds, then bring it low for 50ms, it retriggers and starts over, just as I would want it to.
BUT! When I bring that signal high for ~2 seconds and then low for just 10ms, something happens where the timer is not restarted. If I keep that input going, it only functions every other cycle.
If it was the trigger signal not having time to get low enough, that wouldn't trigger every other time. It can't be the timing capacitor not discharging fast enough because we see it is getting right down to 0. Scope traces are trigger signal in purple, threshold/discharge signal in yellow.
Why in the world could this be happening?


texts: Spatial Locality in Cache - Which addresses are loaded?

texts:
I don't understand quite well the concept of spatial locality in cache. I understand that when there is a miss in the cache, not only the specific address we write is loaded into the cache, but also "near by addresses'' are loaded too.

However, I can't understand WHICH addresses are loaded. I have an assignment with the following question:

The cache consists of 16 words (4 bytes per word). It is arranged in blocks of 2 words.
The following addresses are in BYTES in decimal base. The cache is initially empty.
12,8,24,28,36,44,48,52,60,64,68,76,136,140,144,148,152,220,224,228,220,224,228
Determine what are the addresses which are a MISS (determine if valid/tag miss).

What is hard for me is to understand which addresses are loaded, when, for example, the address 12 is reached. Is 13 loaded into the cache? 14? 15? or maybe 11? How do I know that?

I think that if understand this fundamental question, I could answer this question with ease.

Thank you.


texts: How to find critical resistance in parallel damped circuit

texts:
As the topic suggest, how to find this value? After some research i found a formula but for series crciuts .

$$R=2\sqrt{\frac {L}{C}}$$


texts: Is this memory card circuit designed properly

texts:
I'm looking to build a reusable memory card for my SRAM as the cost of the chips can get up there. I'd like to be able to plug this into other projects (mainly with a W65C816S as I work with it) both with a breadboard and other PCBs.

Before I go about laying this down on a PCB I'm wondering if there is anything wrong or if there are any other suggestions. I can't really breadboard this as the memory is all surface mounted.

I've updated the circuit to add in buffers and bypass caps. For the data buffer to work I needed to add the direction signal to the header so there are some extra pins now. Are there any additional suggestions or comments?

Current circuit. I've changed the multiplexer chip to be low active. It's much faster propagation time is nice. The connector has been updates as well, so hopefully it's handling power and ground a little better. Additionally this has CE line suggestion @PeterSmith


texts: Instrumentation amplifier output stuck high

texts:
I tried to design an inamp for a K-type thermocouple. In theory the gain of this amp should be 250 (close enough to 10 mV/K), and if my understanding of instrumentation amplifiers is correct the output voltage should be the difference in voltage multiplied by the gain of the amplifier(s). My problem is that no matter how I connect the tcl, or if I leave the input floating, the output is stuck high (Vsupply = +5 V, Vtcl = 7 mV (doesn't really matter since Vout does not change), Vout = 4.2 V pinned). Could it be because I'm not supplying my op with +-Vsupply, or is my multimeter not a big enough load and the output is floating or is my design outright flawed, if it is where did I go wrong and how can I fix my issue?

UPDATE 1: Tried with a +-12V supply. TCL hooked up with the correct polarity, the output is ~11V the other way the output is ~-9V. The Non inverting amplifier at the end works fine, but the inamp seems to be stuck at 0.42V on the output. I'll get a precision(or more precise) op and try again.


texts: Arduino AnalogWrite and its frequency and effectiveness

texts:
Reading about the arduino analogWrite function I have come to understand that it uses PWM for the variable DC voltage. (by controlling the width of the pulse)

However how do we control the frequency of the pulse? I came across a few articles about the same but couldn't get them. Any help is appreciated.

Moreover how effective is it to use that analogWrite voltage as say a biasing voltage? Or maybe as a variable Vcc itself. Does the fact that DC is obtained via PWM will effect underlying circuitry expected working (where the underlying circuitry is anything one can do with a transistor)


texts: Is a resistive coil the most effective heating method for a cylinder in terms of power consumption?

texts:
I am trying to find the most power efficient method for heating a metal tube in order to heat up the airflow within it. I came across the Minco mica heater but when I talked to another engineer they said it would be just as effective to simply wrap the cylinder in heater wire and then put ceramic tape over the top. Is there a good way to determine which route is better without buying and trying?

I am trying to maximize airflow through the tube, hence heating the tube itself, and not heating the air directly inside.

I am not stuck on a cylinder, necessarily, but from a mechanical standpoint, it seemed like the most effective shape to take advantage of the heat, but that was possibly a terrible assumption.


texts:
I'm new to online forum. I want to interface 74HC541(Buffer) to 74HC574(D-f/f). The thing is 100's of D-f/f parallel interface as shown in figure(Fig.1).
Input and load capacitance limits it to 10 to 15 fanout. Fanout of buffer current wants to charge input capacitance of D-f/f. So increasing D-f/f increases charge time of input capacitance.
My question is this can be overcome by giving more current to increase charge current to input capacitance by adding pullup resistor to input of D-f/f(Fig.2) or BJT emitter follower(Fig.3).
This would correct or not...

Thanks in advance...


texts:
I'd like to mount a small (2.5") graphic LCD or OLED display on a PCB.  I believe it should look something like this:

I've seen this done (links to pics) on my LM3S6965 development kit, on my TI Evalbot, and on this Sparkfun breakout board. All of those images show a pane of glass, the screen itself, an FFC folded underneath the board, and very little information about the mounting technique.  The LM3S6965 and Evalbot have a bit of foam visible underneath. (I can't speak to the Sparkfun board as I don't own it).

I suspect that the display is adhered to the PCB with double sided tape or an epoxy.

 Am I correct in my suspicions, or is there another method of doing this?  I've considered cutting a relief out of some clear acrylic and screwing that to the PCB as an alternative.
 Is it removable?  I've considered using a solvent or some force.  I'm interested in trying out the screens I already own on other PCBs, and I'm also interested in replacing the screen on my new PCB if I break it or doing edits to the PCB beneath the display.
 Is it easy to do?  I'd like to distribute the PCB with the components (including the display) as a kit to other engineering students, and I don't want them to have to deal with complex epoxy mixing ratios or risk damaging the LCD in the process.
 Is replicating this technique the right thing to do for a development board or in-house tool? I expect users to abuse or break this board, and I expect it to need rework.


texts: Dual DC output voltage power supply made from two power supplies?

texts:
I need replacements for power supplies which output two voltages. For example, a Nintendo 64 needs 3.3V DC 2.7A and 12V DC 0.8A. There are readymade options but they seem to be of questionable quality. Can I combine two single output power supplies? Do I connect the output GNDs? What are the disadvantages to this approach; apart from maybe being overkill, cost- and space-inefficient? The advantage I see is that 100-240V AC to 3.3V, 5V, 12V, ...  DC power supplies are readily available from reputable sources.

As an alternative, I could probably use an ATX power supply and just use some of the output voltages. Is that a better idea?


texts: Incorrect drill diameter for Molex 5569 Mini-Fit Header library in Cadsoft Eagle?

texts:
I have been working on a simple 2-layer PCB primarily intended for routing various power connections (essentially acting as a power distribution junction) to clean up the cabling in my enclosure.

I wasn't able to find an official Eagle library for Molex's 5569 Mini-Fit Headers, so I downloaded Robert Starr's version: con-molex-mini-fit.lbr

Great! So I checked the part I wanted (PN: 39-30-1040), verified that the pin pitch and outer dimensions matched and added it to my design. One small issue I noticed before I was about to generate Gerbers... apparently the drill diameter for the pads is wrong?!

From the layout, the drill diameter of the pad is 1.42mm.

Going to the part's CAD drawing, the pin is 1.07mm x 1.07mm (length x width) and the hole layout says 1.80 ± 0.05mm DIA. So is this 'DIA' referring to the actual drill diameter, or the pad diameter? Either way, the pin diagonal is ~1.513mm so would I have been totally screwed had I sent the original for fabrication? What should I do from here to fix this problem?

Yes, I know it's always better to make your own parts for this exact reason... but please bear with me. This is my first board where I haven't had the wonderful support of CAD engineers to make all the footprints and symbols and check this stuff for me :( I'm trying to be a good engineer, though, and make sure I've done the due diligence to the best of my ability.

Also, to piggyback off a related question, is there an official Molex 5569 library?? I would have commented to ask in that question directly but I'm a sad panda who doesn't have enough reputation to comment yet. D:

Thanks for your help!


texts: pic32 maximum external frequency while running from internal 8MHz RC oscillator

texts:
I am completely new to PICs and I have never worked with a part as complex as this.  In particular, I'm wondering if it is possible to generate a reference clock (REFCLKO in the datasheet) at 11.2896 MHz while running on the internal 8MHz oscillator (the 8MHz is boosted by a PLL up to 40 MHz which is the core clock).  I tried doing this and I looked on the scope only to find that this synthesized waveform had very apparent jitter (measured 25 ns = 1/40MHz jitter) and the frequency didn't look correct.  Slowing REFCLKO down to speeds lower than 8MHz resulted in a nice waveform.

It seems logical to me that you could use the provided registers to derive a 11.2896 MHz clock on REFCLKO from the 40 MHz core frequency. Why does this not work correctly?  Will I need an external crystal oscillator with frequency greater than 11.2896 MHz to make this work?

I saw a blog post on eev blog that said something to the effect of: even though the core frequency is boosted up to 40 MHz from 8 MHz, the maximum possible external frequency is 8 MHz, but there was no explanation as to why.  Please help!!!

EDIT:

It appears that the frequency of REFCLK is not limited to 8 MHz, but rather the frequency is unstable if the ROTRIM register is nonzero.  the ROTRIM sets the fractional part of the divider.  This way I can get a stable 10 MHz (40 MHz divided by 4.0) clock for example, but fine tuning with a fractional divider results in a bad waveform.


texts:
I am using the STLINK from a Nucleo board in order to flash and debug a STM32F7 MCU on a custom board.

Everything works fine except when STLINK is connected to my custom board AND unpowered. Indeed, in this case the MCU on my custom board doesn't seem to start.

After some investigation, I realise that it is the NRST pin (CMOS technology) from the STLINK which is shorted to GND when unpowered, shorting to GND NRST on my custom board.

A simple workaround is to disconnect the NRST pin from STLINK when it is unpowered but I would like to know if there is a way prevent NRST from being shorted to GND without having to disconnect this cable.

I tried a 10K pull-up resistor to VDD of my custom board but of course it doesn't change anything as it seems to be a real short to GND and not through a pull-down resistor.

Does anybody have knowledge of the exact architecture of the CMOS driver of NRST pin ? The piece of information provided by datasheet (p.67) is not really helpful as there are no exact characteristics of the CMOS themselves.


texts: Isolation Voltage rating of Ethernet Magnetics

texts:
I am at the front end of a project that, in part, measures Industrial Voltage levels: 208 Vac through 600 Vac, 3 phase.  This device needs wired Ethernet connectivity.

I've got lots of options for voltage isolation, ranging from using Potential Transformers (step down transformers) for sampling the input voltage or using linear opto-couplers or even placing the A/D converters at the line side and using digital isolators to get the signals to the micro that does the Ethernet stuff.

But I was wondering if it is worth considering having all of the electronics sitting at Line Potential and simply relying upon the Ethernet magnetics as the Isolation Barrier.  Worst case scenario is that the electronics is sitting at phase voltage, which can be 347 Vac (600 Vac phase-to-phase).

My gut is telling me that this is a bad idea but I wanted to get opinions from other people before dropping the idea.

I'm also not sure if I can even find Ethernet magnetic components with a suitable isolation voltage rating.  Somewhere between 2500 Vac through 3750 Vac withstand voltage should be appropriate.  Haven't found any Ethernet magnetics that even show Isolation Voltage in the specifications but that was after only a few minutes searching.


texts: Arduino resetting while reconnecting the serial terminal

texts:
I wrote this code for the Arduino Uno. It will count a variable every second and send that count to the serial terminal. The problem is when I close the terminal and reopen it, the count will start from 0 again. I am confused with this behavior. Please tell me why this is happening.

Here is the code:

#include "Arduino.h"

#include <avr/io.h>
#include <avr/interrupt.h>

#define setbit(x,y) x |= 1<<y

unsigned long newmillis(void);
void newdelay(int x);
void toggle_led(void);

unsigned long volatile _count = 0;
volatile char state = 1;
int count = 0;

ISR(TIMER0_COMPA_vect) {

    _count++;

}

unsigned long newmillis(void) {
    //toggle_led();
    return _count;

}

void newdelay(int x) {
    unsigned volatile long y = (unsigned long)x + newmillis() - 1;
    while (y>newmillis());
}

int main(void) {

    init();
    TCCR0B = 0b11;
    OCR0A = 249;
    TIMSK0 |= 0b10;
    sei();

    Serial.begin(9600);
    DDRB |= 1<<5;

    //int count = 0;

    for (;;) {

        Serial.println(count++);
        newdelay(1000);
        toggle_led();

    }
}

void toggle_led(void) {

    if (state==0) {
        state = 1;
        PORTB |= 1<<5;
    }
    else {
        state = 0;
        PORTB &= ~(1<<5);
    }
}


texts:
I have n mosfet gate connected to 4043 logic and Id is about 100mA. Both 4043 and mosfet has +5v. I have plan to use 2N7000 mosfet

Questions are:
How large gate resistor i need between 4043 and mosfet? Logic output is sometimes put on rapidly. How fast? Motherboard hdd led controls that.
Do i need to place pull down resistor from logic to -0v, between 4043 and mosfet?


texts: How to control the voltage coming off an AC source?

texts:
I need a way to reduce the voltage coming off a ±25 volt square wave AC source. Hopefully, I can interface this with an arduino.

I'm thinking a simple voltage divider, controlled by a digital potentiometer.  Maybe something like this?

I have two questions:

Will this design work? That is, can I feed it a ±25v square wave, and convert that to a ±10v, or ±3.2v square wave? My concern is that the digital potetiometer requires voltage rails as large as the max VAC of my signal.
Is there some better way to reduce a square wave with a micro-controller? One problem with my "design" is that it seems like it requires all the power to be consumed inside one of the voltage divider resistors.


texts: NPN transistor switch wireless charger module

texts:
I am using this module for wireless charging, as a receiver, and i want to switch it on and off, because firstly it consumes about 5mA when idle and secondly i want to power it off when the battery is fully charged. So i decide to use this NPN transistor. I build the following schematic

in order to control the wireless charger receiver. The problem i am facing now is that the charging procedure takes much longer.
Any clue why is this happening?
I dont think the the circuit is wrong, maybe a diode in Vbat in parallel with the collector pin, but i am not sure that this has anything to do with charging procedure.
                        ------------EDITED-----------

I am using a lipo battery and i am starting charging at 3v and i should stop it around 4.1v. The capacity of the battery is 400mAh and the charger receives 300mA maximum. Therefore, when i am not using the transistor the charging procedure takes less than 50 minutes, but when i am using the transistor the charging procedure is about 6 hours(and i am guesing the battery is broken after that).
To control the transistor i am using and arduino uno gpio, therefore 5V/40mA maximum. During the charging procedure usinng the transistor the current floating from collector to emiter is only about 32.5, measured with a multimeter.
So, am i "opening" the transistor enough?
I removed the base resistor and the I_CE current increased to 118.2mA and the charging procedure is more faster now. It's much better know, but still there is about 100mA kind of "lost".
Moreover, when base is set to low, there is a 15mA current floating from collector to emmiter.


texts: "Invalid expression" error when compiling PIC C code

texts:
I am working in a project using a Nokia 5110 LCD, a PIC16F84A, and code in mikroC. When compiling the code, I get an "Invalid expression" error in line 16. This code comes from an example in the library docs. Any idea what I can do to fix it?

const char erste_Bild504; // Use the mikroC PRO for PIC integrated Glcd Bitmap Editor 3310 to
//convert image to a constant array
// Nokia 3310 or 5110 LCD pinout settings
sbit Nokia_3310_SCLK at RB0_bit;
sbit Nokia_3310_SDA at RB1_bit;
sbit Nokia_3310_DC at RB2_bit;
sbit Nokia_3310_CS at RB3_bit;
sbit Nokia_3310_REST at RB4_bit;
// Pin direction
sbit Nokia_3310_SCLK_dir at TRISB0_bit;
sbit Nokia_3310_SDA_dir at TRISB1_bit;
sbit Nokia_3310_DC_dir at TRISB2_bit;
sbit Nokia_3310_CS_dir at TRISB3_bit;
sbit Nokia_3310_REST_dir at TRISB4_bit;
unsigned short i=0;
char * txt=”000”;
void short_to_String(unsigned short j){
txt[0]=j/100;
txt[1]=(j/10)%10;
txt[2]=j%10;
}
void main() {
Nokia_3310_LCD_Init();// initialize the Nokia 3310 or 5110 LCD
Nokia_3310_LCD_Clear();// Clear the Nokia 3310 or 5110 LCD
Nokia_3310 _Write_Text(“willkommen”,5,1); // write text
Delay_ms(2000);
Nokia_3310_LCD_Clear();// Clear the Nokia 3310 or 5110 LCD
Nokia_3310 _Image (erste_Bild);// Draw picture
Delay_ms(3000);
Nokia_3310_LCD_Clear();// Clear the Nokia 3310 or 5110 LCD
 for(;;){
  short_to_String(i); // convert short to string
  Nokia_3310 _Write_Text(txt,40,3);//write text
  i++;
 Delay_ms(1500);
}
 }


texts: Measuring barrier potential of a pn junction using a voltmeter

texts: The image above is from the book "The Electronics companion". Can someone please explain why the barrier potential of a pn junction cannot be measured due to the presence of the contact potential?


texts: Design an AND gate using 2:1 multiplexor

texts: I just started my computer architecture course and I'm trying to figure out universal logic, using multiplexors to represent logic blocks. I found this one example how to use a 2:1 multiplexor to represent a AND, but I could use a bit more clarification. I have truth tables from both a 2:1 multiplexor and a AND block in front of me, but can't connect the dots.


texts:
In STM32 Standard Peripheral library, we need to configure the GPIO.

But there are 3 functions which I not sure how to configure them;

GPIO_InitStructure.GPIO_Speed
GPIO_InitStructure.GPIO_OType
GPIO_InitStructure.GPIO_PuPd

In the GPIO_Speed, there are 4 settings to pick from

GPIO_Speed_2MHz  /*!< Low speed */
GPIO_Speed_25MHz /*!< Medium speed */
GPIO_Speed_50MHz /*!< Fast speed */
GPIO_Speed_100MHz

How do I know which speed do I choose from? Is there any advantage or disadvantages using high speed or low speed? (eg: power consumption?)

In the GPIO_OType, there are 2 settings to pick from

GPIO_OType_PP // Push pull
GPIO_OType_OD // Open drain

How to know which to choose from? and what is open drain and push pull?

In the GPIO_PuPd, there are 3 settings to pick from

GPIO_PuPd_NOPULL // No pull
GPIO_PuPd_UP     // Pull up
GPIO_PuPd_DOWN   // Pull down

I think this settings is related to initial setting of push pull.


texts: Where are small-signal differential amplifiers used?

texts:
I am teaching students about the differential pair (see circuit below).  I addressed many issues like the difference between differential and common mode gain, taking arbitrary vb1 and vb2 signals and expressing them with common mode + differential components, and finally using current mirrors for single-ended conversion.
One thing I have not addressed is that the differential pair is easy to saturate.  Very seldom does the differential pair operate as a linear amplifier, but rather the outputs usually are pushed to their limit (to their rails).  In fact, the range of differential inputs that produce linear outputs is very small (perhaps +/- two thermal voltages as seen below).  What I would like to know from you is if there are any applications of the differential pair that depend on using the linear region only? Telecom antenna preamps?  Wheatstone bridges?
Thanks for your help - (this is my first stackexchange post)


texts: HAL Library CAN Bus interrupt sources and callback functions

texts:
Im using STM32F407 Discovery board and HAL library in CAN bus(CAN1)
Some receive interrupts used with callbacks
(for example receive interruptCAN_IT_RX_FIFO0_MSG_PENDING  can be used
HAL_CAN_RX_FIFO0_MSG_PENDING_CALLBACK_CB_ID.  CAN_IT_RX_FIFO0_FULL can be used HAL_CAN_RX_FIFO0_FULL_CALLBACK_CB_ID)

1) if i want to trigger callback with this CAN_IT_RX_FIFO0_OVERRUN interrupt. what i need to do? There is no callback function related to this interrupt

2) Can i implement own callback function? Is there a restriction with number of callback functions?

3)When i run the project. the special event occurs (more than 2 Rx message received). Callback is worked. But last if statement didn't work? Why?

uint8_t can1_RxFIFOFullCblk[] = "HAL_CAN_RxFifo0FullCallback\r\n";

void HAL_CAN_RxFifo0FullCallback(CAN_HandleTypeDef *CanHandle)
{
    TxMessage.RTR = CAN_RTR_DATA;
    TxMessage.IDE = CAN_ID_STD;
    TxMessage.DLC = 4;

    HAL_CAN_GetRxMessage(&hcan1,can1_sRxMailBox,&RxMessage,can1_Received );
    TxMessage.StdId = RxMessage.StdId; //Send received message with received message ID

    HAL_CAN_AddTxMessage(&hcan1, &TxMessage, &can1_Received[0], (uint32_t *)can1_sRxMailBox);

    if(__HAL_CAN_GET_FLAG(&hcan1,CAN_FLAG_FF0) == true) //if RX FIFO 0 Full flag is set
    {
        HAL_UART_Transmit(&huart3, (uint8_t*)&can1_RxFIFOFullCblk, sizeof(can1_RxFIFOFullCblk), 5000);
    }

}


texts:
Liquid helium has a  boiling point of around -269°C and is used by overclockers. It has led to various world records (e.g. see here and here). What cooling technology can beat liquid helium for the purposes of cooling an overclocked CPU?

(I know dilution refrigerators are routinely used for quantum circuits but I don't know if they can be used for larger circuits like CPUs.)


texts: KiCAD - Arduino shield - matching Arduino pins and schematic

texts:
I am trying to make an Arduino Mega shield using the KiCAD template.
The only pins connected to the Arduino are pins 3,4,5,6,22.
Here is a picture:

I am drawing a schematic, and I am trying to connect the pins to the appropriate pins.
The problem is I don't know where to hook the pins, to correspond to the analogous Arduino pins.
For example, I want to connect my circuit to the Arduino pin 3.
But if you see the template, there are many pins 3, and one of them is hooked to the reset as well.
Here is the picture of the template, with the Arduino pins:

Where should the schematic connect to, if I want to hook up Arduino pins 3,4,5,6,22 like the Arduino picture I attached earlier?


texts: quick question about AC SPST rocker switch

texts:
I'm replacing the motor control switch in this toaster and wanted to be certain about how it should be installed.  It's a normal SPST neon rocker switch with A, B and C for terminals, and B-C being for the neon. It would simply be 1-A, 2-B, 3-C, correct?

Hopefully I wasn't too vague and I can provide more details if needed. Thank you for your help!


texts: LM337 voltage regulator outputs different voltage than calculated

texts:
I am using an LM337 to keep voltage stable at 3V from a battery supply (4x AAA). I've calculated R1 and R2 from the formula to be 100 Ohms and 140 Ohms respectively:

Vo = -1.25*(1+R2/R1)
Vo = -1.25*(1+140/100)
Vo = -1.25*(1+1.4)
Vo = -3

And I used 1uF solid tantulum and 10uF electrolytic capacitors.

Yet it gives me about 4.5V output. Did I screw up something?


texts:
The PICKit 3 user guide tells me that it can source up to 30mA when in "Debugger Powered" mode, and that this mode can be used for independent programming in some cases. It also tells me the PICKit 3 has "software overcurrent and overcurrent protection".

I intend to use the debugger powered mode to program my boards. However, while my circuit draws way less than 30mA (around 5mA), the presence of decoupling capacitors in the power rails of the board means that, for some time, the 30mA limit will be exceeded.

My question is, can I be sure this brief overcurrent won't cause trouble? Should I add something to limit the current draw on the PICKit?


texts: How can I get extra power for USB 2.0 device?

texts: I have a raspberry pi and a WiFi module, unfortunately I can't get enough power from the raspberry to power up the WiFi module. Can I power up the device if I cut an USB cable, I'm letting the data wires untouched and I connect the power from an external power supply?


texts:
As we already know that for an intrinsic semiconductor, the relation between recombination rate (r) and intrinsic carrier concentration (n) is given as the following:

  $$r = a \cdot n^2$$

where a: recombination coefficient.

My question is will recombination rate (r) increase or decrease or remain same with doping.


texts: IEC 61000-4-5 1000V Surge protection for high-side MOSFET output

texts:
I have following schematic, which must withstand 1000V Surge, applied on output OUT according to IEC61000-4-5.
As it is signal output the series resistance of IEC Generator is 42 Ohm and I want to use SMAJ26A TVS to clamp this voltage to about 45V, which should be OK. The problem is that my High-side Switch has a parasitic diode, which allows reverse current to flow into Capacitor C1. The rating of this diode seems to be relatively low - just 0.2A, so most likely it's going to be damaged. Or not?
How to resolve this problem? One solution would be to use external reverse diode of appropriate rating together with some current-limiting resistor. But then TVS seems to be redundant. How this is resolved typically?

simulate this circuit – Schematic created using CircuitLab


texts: Why do active and passive filters have such fundamentally different responses?

texts:
I'm a first-year electrical engineering student and we have an exam coming up on active filters. Before studying engineering, I had played around with active filters, even designing and building a guitar pedal once that was essentially just a filter in a box.

My coming exam got me thinking, though: what is it about active filters that makes their response so fundamentally different to passive filters'?

For instance, the Chebyshev topology has passband ripple. Why? Why don't passive filters ever have passband ripple?

Nothing in my textbook explains this.


texts:
For the 2nd figure for the MAX11169, it tells you to have a c̅s̅ pin for each device and share a conversation line.  Why wouldn't one just have two conversation lines, and load DIN as high meaning its waiting for conversation to go high?

To me, this is just essentially duplicating the first method, which is all around better.  Obviously I'm wrong, as they don't have that advised in the datasheet, I just don't know why.

--


texts: I am not able to instantiate sub modules inside always block

texts: I am designing a floating point unit in verilog. I have designed separate adder, shifter and multiplier modules in verilog. I want to call all these modules and make a single main module. I am not able to instantiate these modules inside always block, but I also need clock in my main module. How do I overcome this problem?


texts: Is there an IR receiver with external IR diode?

texts:
I need an IR receiver that can directly be used with a microprocessor - the TSOP series from Vishay seems to fit well and there are enough tutorials and software libraries to make use of it. Unfortunately in my design I only have space for a normal 3mm (preferably) or 5mm LED receiver diode. Is there a simple IR driver chip that works like the TSOP receivers but with an external IR diode? So it should have 4 pins (Vs, OUT, GND, LED-INPUT) instead of 3 pins, three of them (Vs, OUT, GND) to be used as IR receivers with build-in IR diode and the fourth to connect the diode to (and to GND, of course).

P.S: Maybe a bit more background about my actual project: I want to put an IR receivers into a LEGO® and/or DUPLO® bricks, such as shown in this project. The bricks shall receive signals such as "brick number 12, switch on", "brick number 7, send temperature" etc. from a TV remote control, from an IR keyboard and/or from a custom IR sender at the ceiling. There is enough space at least in a DUPLO brick for one or two additional microprocessors (e.g. ATtiny 13/45/85) and a few wires and resistors. The only possible solution I found so far is using transparent bricks.


texts:
I recently purchased a S111733PI Voltage Regulator. I'm trying to step down 12VDC to 3.3VDC, however the data sheet suggests the use of R1 and R2. They can be selected once I know Vadj and Iadj, how do I get the value of Vadj and Iadj? The circuit diagram with formula is shown below. In the data sheet they've tested it only till 7V input, but it also suggests that the IC can handle 16V input max.

Link To The Datasheet


texts: Measure high impedance with low internal impedance device

texts:
I was given this thought by one of my co-workers (we're both still novices when it comes to electronics). Background: we have a device with a small internal impedance and have to measure a high impedance device. Would an op amp acting as a voltage follower followed by a voltage divider to measure the high input impedance work with the small output impedance device?

Hopefully that's not too confusing. Thanks for your help in advance!


texts: Limiting the short circuit current of a power supply

texts:
I'm using a repurposed ATX power supply for my hobby projects since it's got 3.3/±5/±12 outputs, all of which are really convenient. But one thing I didn't really think about until I slipped my probes across the pins of an opamp, since I've always dealt with commercial/proper lab power supplies in my school labs, was that an ATX power supply will gladly deliver lots of current if that 12V line (or any other) is shorted to ground. The poor LM318 didn't stand a chance. My meter and supply survived, but in the interest of not killing anything in the future, myself included, I was wondering what the best option was for short/overcurrent protection?

I was thinking of sticking some high wattage resistors at the output of the supply before connecting them to the rails of my project breadboard (I use a separate breadboard with terminal blocks for power, which the ATX supply connects to). The problem is if I'm drawing a lot of current (LEDs etc) this will sag the voltage on the line. And, for example, if I use a 1W 200ohm resistor on the 12V line, it limits my current to only 60mA - if I want more, I need some really beefy wattage resistors. I can probably work around the voltage sagging by using a voltage regulator (eg at 10V), but this all doesn't seem like the best way to go about doing things.

I'd appreciate some input from someone more experienced than I am.


texts:
I have troubles understanding the role of C1 capacitor in the oscillating circuit from the schematic below:

Schematic http://img823.imageshack.us/img823/7683/c1role.jpg

My question is: what is the role of C1 in this circuit?

Is it to ensure that the circuit will not latch? So that oscillation will continue?


texts: High precision trilateration in a small space and without ultrasound

texts:
I need my robot to be able to find its position in a room with ±10cm accuracy. For that I have decided to place two radios right at where the door is and the third radio on the robot. The room is small, about 8x4 meters, and as I understand, on small distances the delay between radio signals, which is used for calculating our position using trilateration, would be very small. Signals from one radio will be received by another so fast, that Raspberry PI wouldn't be able to measure the delay accurate enough with its system clock to calculate an accurate position.

Can someone suggest how can I measure the position more accurately with the same set up -- two radios at the door and one on the robot and using trilateration. Maybe using some specific radios, or using something else instead of the Raspberry PI, or covering radios with something to slow down the signals, or something else.

Note: can't use ultrasound.


texts: Is there any relation of ADC's conversion rate with its current/power requirement?

texts:
I'm working on a ADC-AD9266 which gives output at a reference of Data Clock Output (DCO) whose frequency is same as that of ADC conversion rate which also the frequency of Clock. f(clock) = f(DCO) = ADC conversion rate.

I have used FXO Oscillator to clock the ADC. before I was using FXO-16MHz & I was getting DCO (16 MHz) which was correct. But due to some reason I needed to move down to lower data collection rate. So I used FXO-10 MHz IC but now the DCO signal has disappeared.

This was happening even before when I was using FXO-25 & FXO-16 but slightly change(7V-8V) in power supply gave me proper DCO signal.

The problem is, I'm not not getting DCO signal with FXO-10 IC (which was there when I used FXO-16). I'm not able to figure out the problem. connection are proper & no pins are short. I'm having doubt in current that is supplied to FXO or ADC. could there be any other reason because I have just replaced FXO-16 by FXO-10 IC.

ADC-AD9266 Datasheet

BLM21PG221SN1D Datasheet

FXO Oscillator Datasheet


texts: What does the tolerance mean for the 0 ohm resistor

texts: What actually is the percentage tolerance if resistor is 0 ohm?


texts:
For a small lab project I was asked to measure the propagation delay of a SN7400N NAND-Gate. In order to do this i connected one input pin to 5V and the other one to a clock running at 1 kHz. I connected an oscilloscope to the output and plotted it (top signal) together with the clock signal (bottom signal). As far as I know the delay is measured from 50% voltage to 50% voltage which would be about 1.5 squares, which is about 375 ns.
This is far longer than the one in the specification (22ns).

Question: Where does this difference come from? Is it due to the input capacitance of the oscilloscope?
Is it related to the frequency of the clock?


texts: Turn a mains AC load off when another one is ON

texts:
What would be a way to turn OFF load A (10 amps) as soon as load B (10 amps as well) is turned ON, faster than the time it takes for a circuit breaker to trip (~15 ms)?
Something like a voltage activated switch or relay?


texts: How can this 3-phase PM Synchronous AC servo motor operate with single-phase?

texts:
There is a AC synchronous servo motor which can work both as 3-phase and single-phase. Here is a general datasheet.

These can work both with 3-phase and single phase.

I couldn't find what would be the advantage to use it as 3-phase instead of single phase for an application.

Edit:

I made some simulations to clarify my question.
Here is what happens to the output DC link of the "same 3-phase rectifier" with 3, 2 and 1 phase inputs:

3-phase inputs:

2-phase inputs:

1-phase and neutral input:

As you see above, the DC link's average and ripple changes at all of the above variants.

But the AC servo motor's driver can take all of these three combinations as input.

How can we interpret these results?


texts: How do you create a subcircuit in LTspice which is in a txt file?

texts:
I've used LTspice for a long time but I've never made a subckt. When I google "create a LTspice subckt from a txt file", there are no clear steps showing how to do it.
One post said to first change the .txt extension to .subckt then click on some pull-down menu which is in an old version of LTspice and no longer there.
Is there a simple 1,2,3 steps in how to do this?
What I have is a .txt file of a subckt. It's a 4 pin device with several MODELs and SUBCKTs within.


texts: Frequency response of state variable filters

texts:
Could someone explain the difference between the following responses of a state variable filter? It looks as though the band pass response is approximately 3dB lower in the second image.

Assuming a state variable filter:

I have seen frequency responses like this:

and like this:

Are they both correct?
Can they be achieved from the same state variable filter?


texts: How can you change the precision of the pole zero ouput in HSpice?

texts: I'm extracting the poles and zeroes of a circuit using HSpice, but I need it to be as accurate as possible. HSpice is only giving me 6 decimal places, and I'm wondering if it would be possible to increase the number of decimal places outputted.


texts: Battery connected to TP4056 will not operate load

texts:
I have a simple circuit with an Arduino board (load in the diagram) that I want to power using a solar cell via a TP4056 board. The 18560 Lipo battery is for powering the Arduino during night time. It seems if I disconnect the solar cell, the output terminals of the TP4056 goes to zero. I saw a similar thread on this issue and one answer said, the TP4056 is not designed to run a load.

If that's true, then what would the purpose of the battery be?
Does anyone have any idea why the output goes to zero when the input to the TP4056 (solar cell) is disconnected (or there is no light on the cell)?


texts: Slow clock speed with Atmega328P AVR microcontroller on breadboard

texts:
I have a small breadboard with an Atmega328p 28 pin microcontroller with a 16 MHz crystal and two 20 pF capacitors on it (similar to this demo: https://www.arduino.cc/en/Tutorial/ArduinoToBreadboard).

The difference with that demo is I am using a USBasp ISCP programmer to program the chip instead of an Arduino, and I was able to successfully program the infamous 'blink' program to my MCU and I couldn't be more happy.

However, instead of delaying for 1000 ms (1 second), I needed to change the parameter of my wait function to "20 ms" to achieve an on/off time of 1 actual second.

Is there something I'm missing here? Do I need to add anything to my circuit or perhaps change the capacitor values in order to fix the clock speed? Thank you.


texts:
I have the FT232RLMG device and a device that uses the RS-485 connection standard.
I would like to know if I can connect the TX and RX pins of the FT232RLMG to the device that uses RS-485 directly or do I need some more components?

I have looked for information in the datasheet and found that it specifies in the section typical applications:

USB to RS232 / RS422 / RS485 Converters

In the and in technical characteristics says:

Data transfer rates from 300 baud to 3 Mbaud (RS422, RS485, RS232) at
TTL levels.

Link to datasheet: FT232R

Thank you very much.


texts:
I can't understand why the answer is like in the picture and not R = [ ( 4 + 6 ) // 8 ] + 2.
Isn't 4 in series with 6 and parallel to 8 ?


texts: What are the most common causes for a surface mount MLCC to crack?  I just want to learn everything there is to know about the HOT MLCC problem


texts: Can LiMn02 Lithium Manganese Dioxide batteries like CR123a be used in parallel?

texts:
I'd like to use multiple Lithium Manganese Dioxide cells in parallel in increase capacity. Using a single larger cell wouldn't fit the shape requirements for our ID.

LiMn02 are a primary cell and don't support charging.

Is it okay to connect them in parallel if they are fresh or is this likely to cause problems?


texts: I am Making a Power Supply, There is a 40v rail that needs a 10000uf cap, I was wondering if it is safe to use a 50v rated cap, Should i be worried that it is close to the Limit? The Brand of the capacitor is Elna.


texts: 2N7000 level shifter doesn't work under a certain voltage

texts:
I need to convert a 1.8V UART line to 3.4V.

I don't have the 1.8V voltage reference available, but I have the 3.4V reference, so I'm using a voltage divider to get about 1.8V.

This is my circuit:

However, it doesn't work for Vcc = 3.4V. In fact, it only works for Vcc > ~5V.
Why's that?


texts: Convert 320VDC to 220VAC or 48VDC voltage using 220VAC (UK) UPS?

texts:
I've got access to 12 flexible Solar Panels - 320VDC each

Main voltage is 220VAC (here in the UK) and also might buy an electric engine running at 48VDC.

Would a 220VAC Uninterruptable Power Supply (UPS) be able to step down the 320VDC to either 220VAC or 48VDC for use on a boat?

I'm thinking of connecting 12 panels in parallel and use either:

Double-conversion UPS to deliver 48V by bypassing the conversion from the battery back to 220V
Line-interactive UPS to deliver 220V directly from the 320VDC.

The question is would the UPS's surge protection be able to deal with the high voltages? (Keeping in mind the sun isn't real bright in the UK).

Also with regard efficiency will there be a lot of power loss in the system?

I don't really know how surge protection from overvoltage works in UPS's and assume it uses some kind of buck conversion...is it true?

I'm guessing that the surge protection circuits might struggle with continued voltage overload. Does anyone know if this would be the case?

The question is: Will the UPS's be able to reliably deliver either 220VAC or 48VDC?

Here are the specs for each individual panel:

Open circuit voltage(Voc): 429V

Optimum power voltage(VMP):319 V

Short circuit current(Isc): 0.39A

Max operating current(IMP): 0.288A

torrence:+_5%

Maximum system voltage: 1000V

THERMAL CHARACTERISTICS: (-25 ° C to +90 ° C)

Temperature coefficient ɑIsc +0.08%/ ° C

Temperature coefficient ɑVoc -0.35%/ ° C.

Temperature coefficient ɑPmax -0.15% / ° C.

Over-current Protection 30mA


texts: Choosing decoupling capacitors and ferrite beads for a given switching regulator

texts:
I am trying to pick decoupling caps and ferrite beads to use in analog circuits powered by a DC/DC converter. The converter is a PDQE10-Q24-D9, which I am using because it can create a dual supply from a single supply input. The split supply is necessary for the sake of powering the analog circuits. When I look at the waveform of the noise coming from the switching regulator, I see a waveform like this:

For my decoupling caps and ferrite beads I need a noise frequency to choose components. Should the noise frequency I use be given by the distance between closely spaced peaks, or by the vaguely AM-looking nature of this waveform. The following pictures of my scope and the cursor placement show what I mean.


texts:
I am going to be connecting a 9 Volt battery to a bunch of LEDs (14 specifically in a row) I plan to oscillate them on and off, half, and half.  The shape of the LEDS, is a heart so like that I get half a heart lighting up, and the other half lighting up, because I have to recite a love poem written by Shakespeare for my English class; anyway, I have several resistors of various capacitors but I have this one capacitor I have that was in a robot that oscillated turning its eyes(LEDs) on and off its a 2N3904.

My Inventory

2N2222, 2N3906, 8050, MC7812CT transistor

Capacitors

Resistors

Decade Counter/Divider with 10 Decoded Outputs
Divide-by-8 Counter/Divider with 8 Decoded Outputs

AND,OR, XOR,NAND, NOR gates

1 Extra 9 Volt Battery

Several 1.5 Volt Battery

What modifications do I need to make to this circuit to make a blinking heart with 7 diodes being on each side, adding up to a total of 14 RED LEDs?

##NOTE##
I am sorry but I do not know how to get dielectric capacitors on circuit lab, but the capacitors are dielectric.

simulate this circuit – Schematic created using CircuitLab


texts: PDLC Electrochromatic Film / Switchable Glass

texts:
I'm looking to power one of these bits of film with a 12v DC battery.

PDLC Electrochromic Film / Switchable Glass

https://www.ebay.com.au/itm/200-x-300mm-PDLC-Electrochromic-Film-Smart-Film-Starter-Kit-Switchable-Glass/322846672969?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

I believe they operate at 60vac.

I guess it'll involve a dc-ac inverter that will output something like 240vac or 110vac. then gettting an adjustable voltage regulator to step down the voltage to 60v.

I haven't done a lot of work with AC so I don't know the terminology for the components.

What's the easiest and cheapest way to get 60vac from 12vdc?
is there such a thing as an all-in-one DC to adjustable AC inverter? or will I need at least two components.

bonus round:

what would happen if I just put dc in to this film?
can you use PWM for dimming with AC circuits?

thanks heaps


texts:
I'm learning the DDR4 technology and I don't understand how the DIMM/component can change its CL automatically.
FPGAs/ASICs can basically choose the frequency to apply to the DIMM/component.

Why do we stick with the standard's ones? (2400/2666/2933/3200)

DIMM/component can be downgraded to use a lower frequency. Let's say even though the DIMM supports 3200, it still can run at 2666. Nevertheless, in the datasheet, lots of timings and especially the CAS latency/CL change with the frequency (or MT/s).

Why? How does the DDR4 module knows which CL to apply?

For the Xilinx's ddr4 controller, we need to provide lots of timings, why does it need these? How does a motherboard know about all these timings for all the specific DIMM modules?
(tCKE,tFAW,tMRD,tRAS,tRCD,tREFI,tRFC,tRP,tRRD_S,tRRD_L,tRTP,tWR,tWTR_S,tWTR_L,tXPR,tZQCS,tZQINIT,cas latency,cas write latency)


texts: Scaling voltage to meet two conditions at once

texts:
I am using an IC (STM6600) which, among other functions that I need, is also capable of Undervoltage Monitoring. It works like this:

The IC monitors VCC in comparison to two thresholds, V_Low and V_High (which is just V_Low+V_Hysteresis).

When VCC < 3.10V (V_Low), then its status output = LOW (undervoltage condition)
When VCC > 3.30V (V_High), then its status output = HIGH (normal condition)
(Thus V_Hysteresis = 0.20V.)

The problem is:

I'd like the status LOW condition at VCC < 3.45 V
I'd like the status HIGH condition at VCC > 3.55 V
(Thus, I'd like V_Hysteresis = 0.10V.)

Since I obviously can't change the IC's operation itself, I am therefore trying to instead find a way to add some voltage-scaling circuitry in between my original supply (V_battery) and VCC of this IC. What are some ways I can accomplish this?

Note:
I considered a resistive divider as well as a diode-based drop, but I couldn't solve it with either of those because the necessity above is not a proportional scaling. One other way might be to use a low-power microcontroller w/ ADC in between, read the voltage, and PWM-output the mapped/scaled voltage. But I was wondering if there are simpler options.


texts: High and Low times for 555 oscilator are inverted

texts:
I’m new to electrical engineering and this is my first time working with an oscillator.  I'm trying to setup a 555 timer ic as an oscillator with a low time of 1s and a high time of 0.5s.  I've been using the following wire diagram, with the exception I am currently not using D2, though the results are the same with it as without it.

I'm using the following:
C1 = 10uf
R1 = 150kohm
R2 = 75kohm
A TLC555CP IC.

Every thing works except the LOW and HIGH times are the reverse of what I had expected from all the reading I have done.  I got a result of 1s on and 0.5s off.  If I reversed R1 and R2 then I got what I wanted 1s off and 0.5s on.

This seems counter to everything I've read that said R2 had to be less than R1 to get a less than 50% duty cycle. If anyone can tell me why this is I would be most appreciated.

I’ve also noticed that when power is first applied to the ic I get an instant ON that is longer than desired.  All successive ON cycles are okay.  Any suggestions for dealing with this are much appreciated.


texts:
So I built the Wien bridge oscillator without automatic gain control and I am using a preset to tune the circuit instead.

My question is this, so when I reduce the gain of the op-amp to something smaller than 3, I can see the oscillations die out slowly on my oscilloscope. When I turn the preset and increase the gain to maybe 3.2 I still get stable oscillations, but larger Vpp and no clipping. Considering the Barkhausen criterion shouldn't the circuit render unstable, and the oscillations begin to clip?

This only happens when I increase the gain to larger values than 3.4. For a gain approximately equal to 3.3 I get a very weird sine wave almost about to clip. I'm curious to why this behaviour is incremental, I thought for a gain greater than 3, it should automatically clip.

For reference I am using the UA741 and my circuit is configured the same as the picture I included.

Values of capacitors are 10nF and resistors are 1060 ohm to obtain 15kHz oscillations. R4 is equivalent to my preset (20k) and R3 is composed of two resistors in serioes of 20k each.


texts: How am I able to automate AVR ISP programming?

texts:
I have this AVR programmer, which I set up as STK500 in Atmel Studio.

All this works fine until I need to do mass programming with different EEPROM contents.

So if I do no changes to the toolchain that I have, I will need to:

Edit EEPROM hex file (taking care of the checksum and the data consistency)
Pick this file with the Atmel Studio programming dialog
Do the EEPROM burn

And all this for each device (which amount is hundreds or even thousands).

All this will be very time consuming and potentially error vulnerable. So I thought of a software which I will be able to create and communicate with the programmer directly (not through Atmel Studio).

Probably I can use a command line interface (found this here) but I wasn's able to find STK500.exe file on my computer.

I'd even think about making a programmer by my self (at the AVR pin level the interface looks pretty simple) and communicate through the COM-port.

Please share some of your thoughts on the subject.


texts:
i have had some trouble in my kitchen recently about some tingling stingy feeling while touching the kitchen sink. and stove metal.

my toughts is that here is some ground problems but I could not quite locate the problems.

recently I purchased some new LED light to use under the kitchen ventilator, so a few nights I can se these LED's very dim... when I investigated further, this ventilator is entirely off, but I can still change the position of the fan speed.

it was now set to 0, this is when the LED shows as very dim, if I change it to position 1 - 2 or 3 the LED light dissappears, however in between the steps (middle of 1 - 2 and or 2 - 3) this LED shows as dim again until i push it over to either 1 - 2 or 3.

if I again set it to position 0 (off)  the lights dim again

is the ventilator defective or is the problem more severe ?

would also like to know how to use a multimeter to check this


texts: How to compute acceleration from accelerometer raw data

texts:
I'm working on a project based on NXP accelerometer MMA8653.

This is a I2C, 3-axial accelerometer with 10-bit resolution.

Actually I can read the accelerometer registers and I'm able to configure it.
I configured the accelerometer with full scale equal to 2G and the sensitivity associated to this full scale is 256 conts/g

Reading the register I obtain three 16bit signed variables that correspond to each axis.

Which is the formula to compute the acceleration on the three axis?

My MCU has not a floating point unit, so I want to avoid divisions. It's possible to obtain acceleration in mg (millig - 1^10-3 g)?

Thanks for the help!


texts: Simple Yes or No Source Transformation questions

texts:
I know I can compute source transformations using the method shown here in the blue index card here https://imgur.com/a/RXwJT3r.
I used both of these methods, in an exercise here https://imgur.com/a/LHiRIjL
My solution is here https://imgur.com/a/0AuJNJ3
Now, I have some questions about this sample circuit here https://imgur.com/a/rO5HozN

I know if I remove Va, R1, and R3 from the circuit, I can source transform Is and R4.

If I remove R3 from the circuit, can I source transform Is and R4? I understand that the possible answers are "No, Va and R1 affect the circuit... don't allow this...", and "Yes, Va and R1 are both strictly parallel to Is and R4 so you can source transform."

Sorry for the links. I tried to directly upload the images in-line but they were too large.


texts: My oscilloscope has 100 MHz -3dB bandwidth. -3dB is 0.707 units (sqrt(2) / 2). What does this mean, why 70.7% attenuation? Is there any particular reason for this attenuation level?


texts: Why AD834+AD811 voltage controlled amplifier does not accept around ground signals?

texts:
I have setup a circuit according to page 15 of AD811 Op-Amp datasheet . The design receives 0.5-1.2 vpp sine wave between 1Hz-50MHz from AD9850 DDS and it also has around +0.7 to +1 v offset voltage.

According to the schematic below, I have set VG- to Ground, VG+ to 0-1.3v ( the clipping voltage of AD834) and the signal goes to VIN. When I directly connect the signal with the DC offset voltage, everything goes well but no output is seen when I put a coupling capacitor = 100nF between the VIN and the signal to remove the DC part (Cin in the design).

As I read in AD834 datasheet , its output is set by (X1-X2)(Y1-Y2)x4mA and I have not seen limitations for AC signals around the ground.

In fact I want to have a pre-amplification phase with gain=x2 before this design and I need to send its signal without the DC part to this schematic to get rid of clipping to upper voltage region (VS+).

Why this design does not accept signals without offset?

EDITION: the pre-amp:

EDITION2: Inverting:


texts: Will HD44780 display be hurt with 20mA on contrast pin? (pin 3)

texts:
I'm driving an LCD HD44780 display using my Raspberry Pi B+.

Using a GPIO pin I'm managing the contrast adjustment (pin n. 3) on my LCD display with PWM.

In the display datasheet, I tried to search something that talks about minimium resistor between the GPIO out pin, and the contrast adjustment pin on the display, unsuccessfully.

This is the HD44780 datasheet.

So I connect the display and I measured the current flow first without any resistor and then with a 1kOhm one. Here my result.

  Resistor  |   Current
------------|------------
    0ohm    |   20mA
------------|------------
   1000ohm  |   12mA

My questions are:

Can my display/raspberry be hurt using the contrast adjustment without any resistor?
Is 20mA a dangerous current for my display/raspberry?


texts:
Is it possible to "stack" the outputs of 2 or more buck converters?
The buck converter circuit in question I am considering is the 48v to 5v typical example circuit from page 20 of the datasheet PDF for the "LT1339ISW#PBF" part found on mouser here.
LT1339ISW datasheet
I am posting from mobile, but if I can figure out how to directly post the datasheet circuit I will edit it in here later.
I wondered if it was possible to get the outputs of 2 of these buck converters to "stack" their output voltages by connecting the 48v inputs in series to a 96v voltage source and floating the grounds on the second buck converter.
I am thinking that if done correctly the 2 buck converters would share the 96v input source just like 2 equal valued resistors in series will equally share a voltage across them. And as long as you connect the load correctly, the outputs of the 2 buck converters would then act as if they were 5v voltage sources adding to an output of 10V at the up to 50A max rated output current.
For the sake of simplifying the question I am assuming it is possible to balance the inductance and capacitance of the the "stacked" buck converter circuits such that they function the same as the values in the single example circuit mentioned above.
I do realize that even if it is possible, this would not be the most practical circuit since real world components have varying tolerances and any significant imbalance or failure would likely cause cascading failures several other places in the combined circuit. At these voltages and currents it would make for a great risk of fire and injury to nearby people and objects.


texts:
I recently opened my headphone jack because one side of headphones wasn't working
There are 6 wires basically
Dark green, dark blue, yellow, red and two copper wires
Please help which wire should I connect to which side in the head phone jack
I am uploading the picture of headphone jack and wires enter image description here


texts: A DIY Power supply system for a 150w high power led engine

texts:
I have this SST-300 High-power LED which requires 10A and 12-14V as described in the product characteristics. The product is suggesting with its own power supply as well as its own constant current led driver which comes as a separate unit from the supply. however, i would like to make my own power supply system for this one, for budget porpuses.
So im thinking of buying one of those ‘led strip supply’ of 10A and 12V which gives a 120w (lesser than the maximum led power which is 150w) and make the current that comes from the supply even more stable and free of harmful spikes, using this “600w 8-16V 12V 24V to 12-60V 48V boost converter”, even for the price of losing some few watts.
Should it work that way? there are any calculations i need to take in account?
It will be nice to get your help. Thank you!


texts: Serial protocol and connector choice for tethered firmware distribution project

texts:
I am designing a system in which a central host controller that has a cellular internet connection is going to be used to query/control/flash intermittently tethered (wired) nodes.

The central host controller is a Particle Electron and that is set in stone (already have dozens of units deployed and working well for 1+ years).

The intermittently connected nodes are smart batteries that will be connected to the host control/charging interface.

The smart batteries will have an ATtiny MCU (flexible on choice of specific MCU) in them that logs charging data, queries a UUID chip and communicates historical data saved in EEPROM to the host controller.

Part of the design goal is to be able to update firmware on the ATtiny seamlessly after connecting it to the charging harness.  This implies that the charging harness will need to be able to carry 4 additional wires on top of the 2 charging wires to facilitate programming of the MCU via its SPI interface: (SCK, MISO, MOSI) plus a reset wire.

This poses a challenge because if I have 12 smart batteries all connected to the same SPI bus, I will likely have a crappy SPI bus that probably will have a lot of capacitance/slew/noise issues, especially considering that the cable run from host controller to each smart battery will be up to 2 m.  That quickly adds up to 24 m of copper at 12 channels.

My idea to counteract this right now is to multiplex each SPI signal to the 12 channels such that the "activated" portion of the SPI bus stays at 2m.  This would also take care of "addressing" specific channels/smart batteries, which makes me think that I could probably just tie all the ATtiny slave select pins to ground... (though I know that a high to low transition on SS pin of ATtiny results in resetting of the SPI peripheral... which could be important).

The other part of the calzone is the wiring harness/connector.  The charging power wires will be 16 gauge.  There will be minimum 4 additional comms wires (assuming I'm married to the firmware update idea), but ideally 5 (to provide for the slave select pins).

A quick search for 6-8 pin connectors reveals that they will likely cost almost as much as an ATtiny, which makes me want to just add a secondary ATtiny as an external programmer and have both ATtiny operate on a two-wire (or 1-wire) searchable/addressable comm protocol.  This approach has the downside of increased development work that would likely need to be sourced out to an independent developer.

Smart battery production affected by this decision long-term could be in the millions easily.

So, questions are:

What seems saner:  6-8 pin connectors/wiring harness (times 12) running on multiplexed SPI peripheral or a farmed-out ATtiny programmer project running on a 1 or 2 wire interface?
Is multiplexing a 24-foot copper SPI bus down to ("manageable") 2 foot buses doable, advisable, appropriate?


texts: How to check if pin is floating or connected to ground?

texts:
I am using a DC jack which has 3 pins. 2 for power and one pin which is connected to ground when there is nothing plugged into the jack and disconnected from the ground when the jack is plugged in.

I need a way to know wheater the jack is plugged or floating(ie. is this pin connected to ground or floating).
I was thinking about large pull-up resistor from that pin to the positive voltage, but still unsure about that. It would create small current flowing from gnd through a resistor to positive voltage. Is that okay stuff to do in a system?

I am using LM393 to detect this voltage. Can't figure out what resistor value to choose. Positive voltage is at 17V, so 47K resistor would result in 0.36mA leak - not little and still unsure if LM393 would detect it.

(jack input is not only power input, there are batteries inside, so current would flow through this resistor on all times when jack is not plugged - draining the battery).

Are there any better ideas than pull-up resistor?


texts:
I am using an STM32 microcontroller.
I need to have a GPIO output which needs an external pulldown so some relays stay in the right state when the MCU is not running yet. It seems the open drain mode is only for external pull ups as the only possible outputs are open drain and GND.
What can I do to solve my problem? I don't see a configuration that outputs either open-drain or VCC
The output of the MCU (BRAKE_PWR_CTRL) is driving a MOSFET which then drives the relay as shown:

Thanks.


texts: Sensor that identifies if it has a object right in front of it

texts:
I have a small machine that uses a 1 cm wide conveyor belt to transport small rocks. I am looking for a sensor that will identify if there is a rock at the end of the conveyor. This sensor will need to have a minimum range of 1 mm and does not need a max range of more than about 1 cm.

Am I looking for a IR sensor?

Do there exist IR sensors with that small minimum range?


texts:
Quartus has settings to export/import database under the project drop-down box.
The project directory contains two folders named db and incremental_db.
What is this "database" and what does it contain?


texts: Is it possible for (W/L) of 0.18nm PMOS to become 989100?

texts: Is it possible for (W/L) of 0.18nm PMOS to become 989100 ? If not,i wonder what the range is for (W/L) of TSMC 0.18nm PMOS and NMOS.Thanks a lot.


texts: How to measure High-Frequency inductance of inductor using an LCR meter?

texts:
I have a High-Frequency inductor available and I want to measure the inductance using the Rohde&Schwarz HM8118 LCR meter. If I change the frequency to 100kHz and voltage level to 1.5V (max) I get a value of 0.5 Henry which is way too high.

User manual of the LCR meter:

https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_common_library/dl_manuals/gb_1/h/hm8118_1/HM8118_UserManual_de_en_06.pdf

The inductor is made of two ferrite cores as shown in for example here:

https://www.picclickimg.com/d/l400/pict/112230606209_/Ferrite-E-Core.jpg

How can I correctly measure the inductance (should get a value in microhenries) ?

EDIT:

Square wave signal of 100kHz is applied across the inductor (having no DC component). The measured inductance value also has a negative sign in front of it.


texts: Connecting home elliptical trainer to TV power

texts:
I'm attempting to use a TV addiction to help motivate an exercise routine. To do this, I am going to connect an elliptical trainer to the power of a television set (flatscreen). Here is my plan:

I measured the power out to the fan on the elliptical at 6.6V (the fan only runs when the elliptical is being actively used) I am hoping to replace the fan with a cable to the television connected to a relay that I'll embed in the television which will switch power from the standard power input, thus allowing the elliptical to "authenticate" power, but will not actually provide power. The power to the television will still come in through the standard 110 plug.

Assuming that the relay is rated well above 110, and assuming that it is rated for 6.6 V switching, are there additional considerations?  Should the relay run in series with the fan to provide the same load?  Is the relay the right choice?  Should I add an opto-isolator to the circuit?  What kind of load does a fan typically have compared to a relay?  Would too little load likely be a problem? I didn't measure current through the fan while it was running because it was a pain to keep the elliptical going (via walking) while measuring, but maybe I should just give it 6.6 V and measure it.

Thanks!


texts: I am trying to place a keepout region, however when I go to the Place menu, the options are greyed out and I cannot click on them.


texts: Does black anti-static FR4 PCB affect circuit performance?

texts:
I want to make a PCB using black ESD FR4 substrate, purely for aesthetic reasons.

The circuit function will be analog audio.

I presume this material has a small amount of conductivity in order to suppress static. What conductivity level should I avoid, in order that the circuit performance is not affected?

I can ask the PCB manufacturer the resistivity or conductivity of the material.

Below is a photo of the kind of PCB I'm talking about.


texts: So I bought a few push buttons that came with lugs but I'm not sure what tool I am supposed to use crimp them to wire. Advice is appreciated.


texts: Output of the 555 pin 3 high when power on

texts: When I turn on power of 5V of 555 timer, the pin3 is always goes high in the very first power apply. Can we fix this issue? I need the pin3 not goes high when power on, until I make the pin2 goes low. Does anyone have this same issue? How to fix it?


texts: Impedance matching using transformer vs other circuits, what is the difference

texts:
We can use transformers to carry out impedance matching. However, using various configurations of  BJT circuit can achieve the same effect. Here I am talking about common collector, common base and common emmiter configurations. In different configurations we get different input output impedances that can be controlled to much extent.

When do we use a transformer to match impedances and when do we use other circuitry. I understand that if we have very high power applications than transofmer can provide isolation, but what about other not so high voltage applications?


texts: What is with the popularity of the 8051 Core?

texts: I keep seeing the old 8051 architecture around a lot. But I can't see why people would want to use this old architecture in their products when there seem better alternatives around, such as ARM cores, and if you're not designing your own MSP430s, AVRs, PICs offer a good feature set and are low cost. So why are they still so popular?