texts: Circuit with four light bulbs and four batteries

texts:
The circuit has four identical batteries and four identical light bulbs. The current in each bulb is IL and the current provided by each battery is IB.

What is the relation between IB and IL and why?


texts: How to implement a function using just NAND or NOR logic gates

texts:
I am trying to understand the process of creating combinatorial circuits. I understand that first we document the inputs and outputs, then create minterms and max terms, then push them into a k-map and get a function as an output. This function can then be implemented using logic gates.

The problem I have is, I don't understand the logic behind converting the equation that we got, such that I can implement the same circuit using just NAND or nor logic gates.

The image is from my book for converting a half adder circuit. I understand the steps taken but don't understand the reason why they took them. Thanks for the help.


texts: Recommended Footprint width smaller than actual pad width

texts:
I was just about to create a footprint for a Kingbright LED from the KP-2012 series. From looking at the data sheet I am somewhat irritated:

As you can see, the package pad with is 1.25mm, while the actual solder pattern width is only 1.1mm.

Why would this be desired?


texts:
I have the following circuit :

That's basically everything, excepted a button on DC1 to turn on/off the motor, but shouldn't impact.

The problem is, I was prototyping with the DC Motor on the LM7805 and the other parts powered by the +5V of the arduino I was using to program the ATTiny45. I assume the DC Motor resistance at "full speed" is \$50\Omega\$. (Around 0.1A at 5V).

Now I've moved everything on the LM7805 and when I turn on the motors the ATTiny shutdown after few seconds. The time he stays up depend on the value of RV1 who manage the speed of the motor, controlled by the attiny with the BC337 transistor controlled with PWM.

So, I started to use bigger caps but I can't stabalize the circuit. I've tried with 4700uF on C1/C2/C3 and the improvement is not soo great, a bit better but still shutdown pretty quickly. They are placed as close as possible to "their pins".

So, what can I do to leave the motor at that place ? Put it on a separated LM7805 ? Add a capacitor somewhere ? (I really need to put it on a voltage regulator)


texts: Which wire is suitable for connecting runs of EL wire?

texts:
I've got a little EL wire project coming up. Unfortunately I'm not too savvy when it comes to electronics, but there's plenty of tutorials online to tell me what to do. I'm clear on most of what I'll need to have and know (inverter, sequencer, how to solder the EL wire...) but there's one small, silly detail I'm uncertain about.

I'll be wanting to connect a few runs of EL wire together, but not joined directly. They need to be connected with some regular wire to create some distance between them. I might also need to have some distance between some runs and the inverter/sequencer. Nothing too big, say 3 feet/1 metre at most. What wire is suitable for this? What sort of AWG? I've got some wire that I use for LED strips; would that be okay? Since EL wire draws low current, I'm guessing you can go pretty thin. The thinner the gauge, the better it would be since the wires should be as inconspicuous as possible.


texts: Why is inductance negative in this triphase mutual inductor?

texts:
Suppose I have a threephase circuit with a mutual inductor on the first and second phase (V2 and V3). One way of solving the circuit (ie finding the phase currents) would be the following: convert the mutual inductor in the corresponding Y inductor and then solve the threephase circuit as you normally would do. Suppose you are given the following parameters for the mutual inductor:

simulate this circuit – Schematic created using CircuitLab

$$L11 = 10mH$$
$$L22 = 20mH$$
$$Lm = 12mH$$

where Lm is the mutual inductance. By appling the suggested transform method:

simulate this circuit

$$\begin{pmatrix}
L1+L3 & L3\\
L3 & L2+L3
\end{pmatrix} = \begin{pmatrix}
L11&Lm\\
Lm&L22
\end{pmatrix}$$

I obtain the following. (Note the negative inductance, which in turn gives a negative reactance, not ok in my opinion).

simulate this circuit

Now, by solving the circuit everything looks fine, the results are EXACTLY as the solution states (that would suggest that my steps are correct), however it does not seems ok to me that the inductance L1 is negative! Why is this happening, what am I missing?


texts: The pros and cons of tantalum and ceramics in AMS1117

texts:
Task: Make a reliable power supply for sensors and an RFID card reader.

Specifications:

Total current consumption: up to 0.7A (700 mA.)
Elements supply voltage: 3.3V
Input voltage: 5V
Working temperature: from -30 to + 40

For these purposes, I found the AMS1117 voltage regulator.

The technical description indicates the use of tantalum capacitors.

I studied them, and I still had doubts about their reliability.

What I learned:

Tantalum minimally changes the capacitance with a change in voltage and temperature, unlike ceramic capacitors.
Tantalum does not age
Makes no sound
May explode in case of strong impulse or incorrect polarity.
It has a high parasitic inductance, unlike ceramics.

Many boards with this voltage regulator use ceramic capacitors, but I'm not sure about the reliability of this option.

I worry that tantalum may explode or fail.

Questions:

Is it dangerous to use tantalum and is it worth switching to ceramics?
Is it good to use electrolytic capacitors, given the negative operating temperatures?
I heard that special voltage regulators have appeared, designed to work with ceramic capacitors. What are some good options? The current must be up to 1A.

My main task is to provide reliable power to the sensors and reader.


texts: Simple LED Dimming from Analogue Voltage Control

texts:
I have a circuit which switches 12V to power a 12V, 20mA LED (Marl 512-997-21, RS: 310-6921). I need to modify this to add some simple dimming control. The current circuit doesn't have any resistors in-line, it just switches 12V directly so I assume this LED has a resistor built in.

I have a analogue control voltage available (0-10V), so could I simply feed this into a op amp with 15V supply (large enough to output 12V and suitable power drive capability to source 0.5W) to vary the output voltage? Looking online it seems constant current and PWM control is recommended but this seems a bit overkill for what I'm trying to do requiring additional complexity. I really need this to be as simple as possible with minimal component changes to the existing design whilst still being "good". Linear brightness control would be desirable. Any advise is greatly appreciated. I thought this would be simple looking online but there seems to be some very complex methods of doing this.


texts:
My last question brought up some discussion about application notes and (bad?) practice. See the comments under the various answers.

Until now I thought: "Ok these application notes are written by electrical engineers working at some big companies, who probably know what they are doing."

But after reading the comments from my last question, I dont know whom to trust.
If I had been studying electrical engeneering or had enough pratical experience, I probably would have enough knowledge to see bad practice / wrong application notes. But I am just a hobbyist.

So what should I do? Just go ahead and hope, that everything works fine, until something breaks. So I know the next time: dont do this. According to the comments in the linked question, this could be realy frustrating, because some faults come and go randomly.
Maybe I do not even realize, that the design I took from the application note was wrong. I would probably search for a mistake in my design, because I am the unexperienced guy...

One thing I have learned so far from the comments in the other question is, that I should always look through the datasheets and search for things that exceed the operation ratings of the devices (it is not safe to just stay within the maximum ratings).

Is there anything else I should check in an application note, so I could identify a probably bad design and ask someone (e.g. here), whether it is realy bad design?


texts:
I've set the PIC16f887 on both external crystal 20MHZ and internal oscillator 4MHZ, neither of them ever worked with the following code:

int main(void) {

    ANSELbits.ANS5 = 0;

    TRISEbits.TRISE0 = 0;
    PORTEbits.RE0 = 1;        // pin RE0 is high

    TRISDbits.TRISD1 = 0;    // pin RD1 is high
    PORTDbits.RD1 = 1;

    while(1);

    return 0;

}

But with the above two oscillator modes, I successfully worked out some UART functionality. So this might rule out the possibility of the PIC not working. At least I think so.

Just to be specific, my configuration bits for INTOSC are:

#pragma config FOSC = INTRC_CLKOUT
#pragma config WDTE = OFF
#pragma config PWRTE = OFF
#pragma config MCLRE = ON
#pragma config CP = OFF
#pragma config CPD = OFF
#pragma config BOREN = ON
#pragma config IESO = ON
#pragma config FCMEN = ON
#pragma config LVP = ON

// CONFIG2
#pragma config BOR4V = BOR40V
#pragma config WRT = OFF

And as for external crystal, I just changed:

 #pragma config FOSC = HS

As I've read the datasheet over and over (maybe I still left out something important), I know the first thing to use a pin as general purpose I/O pin is to clear all the peripherals.
So I did

ANSELbits.ANS5 = 0;

to make sure RE0 is on digital input/output mode.

And I set the corresponding bit in TRIS register to configure the bit as output.

But it never worked.

update

I checked that the volts between VDD/VSS and RE0 are both zero, which confuses me quite a lot.

Does anybody know what is going on here?
FYI, I tested both PIC16f887s. They all ended up the same.


texts: Can I use a standard SMA connector and cable to deliver high voltage to a PCB?

texts:
I'm designing a power circuit which I need to bring high voltage, ~3000V DC, into from an external power supply. Normally I would use an SHV connector, but they don't seem to offer these connectors in a form that can be mounted directly to a PCB.

Is it possible to just use a standard SMA cable/connector? I assume the connector would be fine as 3000V is not enough to arc from the sleeve to the pin, but I'm not sure about the cable itself.


texts:
I currently have an Arduino UNO, a stepper driver (the TMC2130 v3.0), and a Nema 17 stepper motor. I was trying to find the correct way to wire the driver and motor to the Arduino in order to simply run my motor at different speeds, however, I got a bit intimidated and confused by the sources I found online. Does anyone have a simple schematic and maybe an example code in order to do so?
Thanks very much


texts: Linear circuits and what components a network can posses to account for linearity

texts: I was studying circuit theory and electrical networks wherein I came across the theory of superposition and how superposition can be used to figure out voltages/currents in the network, provided the network/circuit is linear. What exactly is a linear circuit? What elements can I have in a linear circuit? Can I have resistors, capacitors(charged and empty), inductors(charged and empty), BJTs (biased and unbiased); diodes(biased and unbiased); any of the above I wish for in my circuit in any configuration and still maintain that my circuit is linear?


texts: Increase voltage output by connecting 2 PSU channels together

texts:
I have a 240W 24V switching power supply. It's a cheap chinese psu so there is no specification, only the info on the ebay page.

It has 3 dc output channels and they seem to be individual channels and not just same output via different terminal pins (meaning it can output 24V to 3 different devices at the same time). I need 32-34V to power an led (via constant current driver). Is it possible to connect 2 of the 24V outputs to achieve 48V (34V with voltage adjusted to minimum of 17V possible by the psu )? If so how? I can imagine how you would connect the outputs in series...


texts:
I have this circuit which looks like a current divider but with an extra capacitor.
I want to know how Ia , Ib, Ic change as the capacitor begin to charge, i do know one thing after a time of 5 RC the capacitor will be about 99.5% and the first branch ( the one with the capacitor ) will be considered open, and we can consider the whole branch not there.

( the source is  a current source)


texts: Need help understanding DALI circuit and 220 VAC protection

texts:
I am making a circuit to interface my MCU with a DALI bus. My basic circuit works and I am able to communicate on DALI bus. It looks like this:

I fully understand the above circuit.

After my base circuit was done, I found out that DALI bus should be protected against accidental 220 VAC connection on the DALI bus. I have no clue how to proceed on this. I found a document online which gives this circuit but doesn't explain anything about it:

Can you please help me understand how this circuit works in following conditions:

a) What happens when a data packet is received on the bus in working voltage range (16 V typical)?

b) What happens when the MCU tries to send a data packet in working voltage range (16 V typical)?

c) What changes when there is 220 VAC on DALI bus? How does this circuit work to prevent a failure in this situation?

Thanks


texts: FPGA Simple RAM Model - Why is the address delayed?

texts:
In the sample code below from Doulos that models RAM using an array, why is the address delayed?

Specifically, why did they bother to create a second signal read_address instead of using the input address throughout to access the array?

I suspect it has something to do with concurrent versus sequential, but I can't figure it out...

-- Simple generic RAM Model
--
-- +-----------------------------+
-- |    Copyright 2008 DOULOS    |
-- |   designer :  JK            |
-- +-----------------------------+

library IEEE;
use IEEE.STD_LOGIC_1164.all;
use IEEE.Numeric_Std.all;

entity sync_ram is
  port (
    clock   : in  std_logic;
    we      : in  std_logic;
    address : in  std_logic_vector;
    datain  : in  std_logic_vector;
    dataout : out std_logic_vector
  );
end entity sync_ram;

architecture RTL of sync_ram is

   type ram_type is array (0 to (2**address'length)-1) of std_logic_vector(datain'range);
   signal ram : ram_type;
   signal read_address : std_logic_vector(address'range);

begin

  RamProc: process(clock) is

  begin
    if rising_edge(clock) then
      if we = '1' then
        ram(to_integer(unsigned(address))) <= datain;
      end if;
      read_address <= address;
    end if;
  end process RamProc;

  dataout <= ram(to_integer(unsigned(read_address)));

end architecture RTL;


texts:
I have made my own version of the Leonardo, and I am having USB issues. Plugging it in to a windows computer - nothing happens! If I hold down reset, I get the "device not recognized error", but if I don't hold down reset, Windows acts like nothing is there.

Schematic: (http://i.imgur.com/V76C6GS.png)

Fuses
Extended: FB  (If I program it as CB, then press read again, it comes out as FB?)
High: D8
Low: FF

Using Caterina-Leonardo.hex, uploaded with AVR ISP MKII

The board itself is working, if I compile a blink sketch and flash it directly it works great. It's just that when I plug it into a computer, nothing happens.

Any ideas?


texts:
I was trying to convert the pressure values (in psi) into 4-20mA current. The range of pressure values I have chosen is between 0-10Psi. But according to the link given below the pressure from 3-15Psi is converted to 4-20mA. Does that mean that I cannot use the range 0-10Psi
https://instrumentationtools.com/example-of-3-15-psi-to-4-20ma-conversion/amp/


texts:
I'm new to Altium 17. Before that, i was using Altium 14 and things were pretty good. I have a problem about components on PCB.

In schematic, whenever i use "update PCB Document", components spread out everywhere of screen. Is there any solution to align them in order? Thanks.


texts: How to apply Ziegler–Nichols to a heater-termometer system?

texts:
This is not a production project (though I don't mind it having practical value), but an undergraduate thesis. I already have an onoff controller  with hysteresis and that works fine. I am hoping to compare results and show that a pid is "better".

The process I need to control is the temperature on the surface of a 50W heater. For this I am using an Atmel implementation of a parallel structure classical pid. The input and output type is int16_t i.e. signed.

Consequently, the power to the heater is controlled in this way (pseudocode):

if(pid_return < 0) set_heater(0%);
else               set_heater(100% * pid_return / INT16_MAX)

To apply Ziegler–Nichols, I need to try different P controllers and identify the one, which causes consistent oscillations, then measure amplitude and period. In the light of the limitation from the previous paragraph, how should this procedure be adjusted?


texts: System-level, mixed signal hardware description language (HDL) and software (editor, simulator)?

texts:
I am looking for devices (conceptual / software) to simplify and unify our current method of industrial control system planning and documentation, especially to help with debugging.
This is currently a collection of different systems and files, i.e. system-level graphics, signal spreadsheets for interfaces, schematics (system-level electrical planning, components), ...
Unfortunately, the complexity of the design cannot be reduced.

The solution should allow hierarchical capture of system (controllers, sensors, actuators, wire, connectors, ...) and component schematics (internals like switches, amplifiers) and ideally allow tracing of signals through elements (across nets).

Ideally this could reduce the number of manually created documents and generate the respective output "views".

I thought of an object-oriented approach (signals, pins, nodes, signal level modifiers, groups) that would allow building such system but that would be very likely reinventing the wheel, and also would be quite an undertaking, especially with regard to the graphical interface.

However, I did not find existing software for the task so far; I am probably not searching with the right keywords. HDL mostly returns logic/chip level design software. While SPICE is for simulation, it is too specialized for my task. EDA (Altium, Eagle, KiCad,  ..) or electrical planning software does not provide simulation features to my knowledge (it could be used to graphically create netlists to work with, though).

I've now discovered SystemC and Electronic system-level design and verification (ESL) which leads to EDA software firms which seem to focus on chip-level design software but also feature system level electrical planning (and apparently also simulation, but I'll have to research that further).

What are the proper terms or standards to search for?


texts: I want to do even-odd mode analysis, is representation of the circuit as shown below correct? Are these two circuits equivalent. Z is the characteristic impedances and theta are the electrical length of the TL.


texts: Which are more reliable, sensors with current varying output or voltage varying output?

texts:
A sensor is connected to a controller. The sensor output into the controller can be of two forms,current varying or voltage varying. which is more reliable(in terms of noise as well) and why?
My area of application is for an industrial use with lot of noise (electrical)


texts: Can we prove the difference of phase between the voltage of three alternating current is 120 degree with "math formula"?

texts:
In the three-phase electric power,we will assume the difference of phase  between the voltage of three alternating current is 120 degree

I want to ask why do we assume the 120 degree is the best option for the difference of three voltage phase?Can it be proved with math formula ?


texts:
I have various pieces of equipment that all need to be connected to GND (Chassis GND).  The issue I'm having is that I'm connecting an ADC card inside a computer through a metal box with custom electronics that connects into a cryostat (metal shield).

The problem is that if I just use my standard cables then the computer GND is connected to the metal box with the electronics in which is in turn connected to the metal of the cryostat. Now the computer is connected to GND via the plug and the cryostat is connected to GND via a big metal strap to the building GND.  This to me smells like a bad case of a ground loop.

So I'm thinking that I need to break the shield somewhere on one of the cables.  The questions is where?  The electronics are amplifying a rather small signal from the cryostat so I'm guessing that I want to try and keep that shield connection continuous.  I was going with breaking the shield at the box on the cable that runs to the computers ADC. Is this a good idea? Should I not worry if the Computer GND and cryostat GND are pretty much connected to the same power strip?

Note that the electronics GND should be floating from the Chassis/building GND.


texts: Why even when we increase the synchronous speed, the slip still remains it's value?

texts: This is an induction motor question: why even when we increase the synchronous speed, the slip still remains it's value?


texts:
I am interested in controlling an RC helicopter using a desktop/laptop computer. I see two possible approaches for such a project:

Wire the RF remote to a PC either directly or through some microcontroller.
Install a microcontroller directly on the helicopter and use Wi-Fi, Bluetooth, or Zigbee to communicate with the microcontroller.

My end goal is to use motion tracking data from a system of IR cameras piped into a feedback control system to develop algorithms to control flight paths. The motion data will come from a separate system, but what I am looking for here is a 'best practices' approach for physicality wiring (or wirelessly linking) the low-level control of the helicopter to a computer.

What would be the most efficient way to approach this problem?


texts: Spatial receive diversity and antenna coupling

texts:
Spatial Receive Diversity works best if the receive antennas are not correlated, i.e. if each antenna sees a different wireless channel.
MRC ensures that in case of 2 antennas for example , the 2 signals will be weighted and combined in phase (the data stream is the same in case of diversity)
What happens if there is mutual coupling between the antennas which results in an isolation that does not exceed the SNR required to detect the signal.
The signals at each antenna are not aligned (not yet) so they would contaminate each other, how is this dealt with in practice?


texts: How do they remote control the military drones?

texts: I am interested to remote control something (sorry for the vagueness) over a distance of several hundred kilometers to a place where there are no internet cables. Therefore, I am interested to know how the US Military remote controlls their drones. My best guess is via satelite communicatation, but wouldn't there be too much lag to make this a feasible option, at least when considering the speed these drones fly with? I also wonder whether such satelite communication is available for civil purposes at a reasonably affordable price?


texts: GND signals not connecting to Polygon in Eagle

texts:
I am designing a board layout in Eagle. Before manual/auto routing, I made a polygon around the corners and named it as GND. Then I used the autorouter for routing. After the routing is complete, there are few yellow wires left and these wires are of GND connections.

As you can see in the image, there is a yellow wire attached to the GND of the LED1 and the 3rd pin of the JP2. According to my understanding, this should not happen because I have made the Polygon of GND. What could be the problem. Am I doing something wrong. Please help. Thanks.!


texts: creating worst-case scenario test environment for wireless

texts:
I'm making a project which involves the use of two HM-TRP radio modules.

At this time, the only way I can test the strength of these modules is to go out on the street and travel with one unit for about 1km until I see signs of data disconnection (example, led on my board flashing).

What I want to do instead is to make the signal transmission weaker without actually configuring the on-board hardware. I mean if I had an elevator made of solid construction in my house or even a subway station with no service nearby, I'd probably be all setup because then I can put a module in one of those things and test my signal without walking 1km.

Since I have no access to either of those things, the only other things I could think of is to use a sheet of mesh wire or cover even one of my units almost completely with aluminum foil.

The point is, winter is approaching and I don't want to freeze my fingers off while running wireless tests. Am I on the right track with using aluminum foil and mesh or are there better things I can use to make a radio module transmission more difficult?

The modules are set to run at 915Mhz frequency.


texts: What is the output voltage of this 555 timer high voltage circuit?

texts:
I'm trying to calculate the theoritical output voltage of the following  555 timer high voltage circuit.
It claims to output up to 20kV, however results I get give only 12kV.

(source)

Here is how I did it:

According wikipedia, frequency in 'astable mode' is given by :

For this circuit :

\$f = \frac{1}{0,69 \cdot 0,00000001 F \cdot 33000\Omega} = 4391 Hz\$

I calculated the output of the transformer to be 125 times  (1000 / 8) higher than input. Since 12v is given as input, output should be 1500v (not sure about this)

Then I draw the circuit in circuit lab:

simulate this circuit – Schematic created using CircuitLab

And I ran a time domain simulation (Stop Time = 30m, Time Step = 20u)

The output stabilizes at 12kV:

What is wrong? Did I miss something or are the results given by this circuit a little too optimistic?


texts: Concurrency issues with circular buffer in embedded program

texts:
I am working on an embedded program on the TM4C123GH6PM microcontroller from the Texas Instruments Tiva C Series LaunchPad.

The program is supposed to sample an external ADC in a timer interrupt and push the converted values into a queue (in this case a array-based circular buffer).

The main loop is transferring the values (popping bytes out of the queue) to a PC through the UART.

Inside the timer interrupt, a check is done to ensure that space is available in the queue. If so, bytes are pushed onto the queue.
If not, it stops the timer. The main loop will transfer the remaining bytes and start the timer again once the queue is empty (all bytes have been transferred).

My problem is that the timer is not always stopped even if the queue is full.

Could this be a concurrency problem? If so, how do I solve it?

By the way, I have played around with locks but this causes deadlocks. I have also ensured that the queue and related variables accessed both by the main loop and the timer interrupt is declared volatile.

Thanks in advance :-)


texts: What is the max amps for the Adam 6050 module

texts:
I recently purchased an Adam 6050 module and need to power it up.  However the manual seems a little vague, other than mentioning that it has a 10-30 volt unregulated power range.  And that it consumes 2W at 24V.

Near the bottom of the manual I found a note saying to use the power module PWR-244 as an FCC approved power source.  That power module is listed as having an output of 24V and 4.2 A max.

I have a little AC/DC power adapter that I can plug into the wall that outputs 24V and 800 mA.  I don't think I will blow up the adam module with that, am I correct?  The worst case scenario I can come up with is that it won't work because the adam module might need more ampers to function.


texts: A general purpose way to connect cellphone line out to a microcontroller ADC

texts:
I have looked at many questions with similar titles but cone cover my query.
Question: How can I protect an STM32 Cortex M4 series ADC input when measuring the AUX output voltage from typical smartphones (eg Samsung Galaxy)

Here is a circuit I used to sample the mobile audio output through AUX jack, the measurement will be done by an ADC with maximum voltage input of 3V3 (may be 3.6V but I keep it lower.)
The ADC is part of an  STM32F446re  microcontroller.

simulate this circuit – Schematic created using CircuitLab
I am advised that this circuit can damage the ADC.
I (and many others) am looking for a safe way (safety is more important than quality of the signal) to sample audio from AUX jack (headphone output/line out/etc) where the solution is independent of the phone and is standard to most of them.


texts: How can I control 2 or more seven segments displays using a single microcontroller?

texts:
Is it possible to control say up to 4 seven segments displays using a single microcontroller and having some I/O ports left?

For example, say I would like to show a reading with 4 seven segments displays using a driver like MAX7219. Do I need a driver for each display? Can I control all the segments using just one driver and SPI communication with the microcontroller?

More generally, I'm asking what is the industry standard way of doing this which I guess uses the minimum number of components. I know it is possible to build an analogue circuit to drive each segment, use an EEPROM, use a driver for each display, etc... but I am looking for a way that uses the least number of components.


texts: What does Timestamping of GPIO pin means and how to achieve it?

texts:
I did my bachelor's in CS and I am pretty new to electronics and with embedded system as my specialization, I am not able to grab some of the concepts. I have made a program which toggles an led on and off using the gpio pins for the module LPC1769. This works fine.

However, now I am trying to understand the concept of timestamping of GPIO pins, so that I can transmit data from one mcu to other.

Can any one help me with the intuition for this ?

PS: Please pardon me for the bad tags.


texts: How does a comparator based crystal oscillator work?

texts:
I'm a newbie here.
Now I want to design an oscillator circuit to drive QCM-Sensor. Then I have found a circuit from the datasheet of comparator LT1671.

It looks just like a relaxation oscillator with a Crystal on it. What I can't understand is how the crystal helps the relaxation oscillator to produce a stable oscillation. Some articles simply says that, crystals have the ability to select frequencies, but I don't really understand.
All I can understand so far are:

how a relaxation oscillator (without crystal) works

A crystal can be described by an equivalent BVD model. At the series resonance frequency the crystal works like a Resistor and at the parallel-resonance likes an Inductor


texts:
I am trying to use the USART to make two PIC16F877A microcontrollers communicate. When I look with an oscilloscope at the output on the TX pin of the MCU that's transmitting , I see the normal NRZ waveform, with the correct baud rate and voltage levels. However, as soon as I connect the TX pin to the RX pin of the other MCU, the voltage drops to almost zero, exactly as if there was a pull-down resistor in the chip. When I remove the MCU from its socket, I measure an infinite resistance between the RX pin on the board and the ground, so the pull-down must be happening in the MCU and not elsewhere in the circuit. I assume I'm not setting up the USART properly, but I can't find anything in the datasheet that explains this behavior.

Here is the receiving PIC's code :

#include <stdint.h>
#include <xc.h>
#include "config.h"  //Configuration bits

uint8_t buffer;

void setupUSART(void)
{
    TXSTAbits.BRGH=0; //Set baud rate generator to 9600bps for 3.6864MHz xtal
    SPBRG=5;

    TXSTAbits.SYNC=0; //Async mode
    RCSTAbits.SPEN = 1; //Enable USART on pins RC6&RC7

    RCSTAbits.CREN = 1; //Enable continuous receive
}

void main(void)
{
    TRISB = 0; //output port, used to write to LCD
    TRISC = 0;
    PORTC = 0;
    setupUSART();

    LCDWriteCommand(0b00111000); //Function set : 8bits interface, 2lines display, 5*8 font
    LCDWriteCommand(0b00000110); //Entry mode set : increment cursor, no display shift
    LCDWriteCommand(0b00001100); //Display control : display on, cursor off, cursor blink off
    LCDWriteCommand(0b00000001); //Clear display & home cursor

    while(1)
    {
        if(PIR1bits.RCIF)
        {
            buffer = RCREG; //Store received data

            //Display the received char to the LCD
            LCDWriteCommand(1);
            LCDWriteASCII(buffer);

        }
    }

}

And the configurations bits :

// CONFIG
#pragma config FOSC = XT        // Oscillator Selection bits (XT oscillator)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = ON       // Power-up Timer Enable bit (PWRT enabled)
#pragma config BOREN = ON       // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = OFF        // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)
#pragma config CPD = OFF        // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF        // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)

Thank you.


texts:
I am trying to figure out how to calculate the sensitivity of a circuit, especially the sensitivity of a damping ratio (how much the damping ratio changes as each component value varies).

Expression for zeta is quite long and complicated, so I prefer not to take partial derivative. I would like to do something like:

calculate the value of zeta when R = 100 ohms.

calculate the value of zeta when R = 101 ohms.

then divide the change in zeta by the change in R.

In this case, how would I normalize this sensitivity value (x/y part)?


texts: How to increase the amplitude of a colpitts oscillator circuit?

texts: This oscillator works at 1.1 MHz frequency and its amplitude is 0.4 volt but I want to increase it to between 4 to 6 volts.


texts: Wiring Embedded Display Port (eDP) to a full-size Display port

texts:
In spare time, I repair laptop computers. Pretty much all of the screens in them now use this "eDP" Display Port technology and I thought "this could turn out to be great for troubleshooting" because now there is some standardization. If a laptop came in with a blank screen for example, maybe I could connect a full size Display Port cable to the motherboard, to see if there is a fault with the eDP circuit or if the screen itself is dead. After soldering 5 or 6 jumper wires, I could potentially know where the fault is, in just a few minutes.

Microsoldering is no issue for me, and although this is a long winded way to test things (I could just go and buy an eDP tester or buy a known good screen) I did find it interesting to have a go at the cable - but I have had mixed results and need some help in determining what I'm missing.

My research found that eDP requires the following:

Main Lane
AUX Lane
Hot Plug

...and ground lines.

I used a small 11 inch netbook motherboard that I know uses an eDP screen (I have the schematic "quanta_zhk_r3a_20140630_schematics.pdf"). I removed the eDP ribbon connector and soldered a terminal block with jumper wires to it. Then I connected the above lines to a standard Display Port cable, from which I had cut off the plug.

The external eDP cable was plugged into my Dell Display Port monitor, but it gave no image. I connected an HDMI monitor to the motherboard as well, so I could monitor what was going on (i.e. if a second screen was detected). I got as far as the motherboard detecting both monitors (they were both listed in Display Properties) but no matter what I did, I could not get any image on my external eDP screen. I tried all of the multi-monitor options and even booted without an HDMI monitor connected.

The Display Port monitor doesn't "wake" up at all, even though the computer is obviously able to read the displays information (which is apparently gathered via the AUX/Hotplug lines). So it would appear that these lines must be connected OK.

This motherboard only has one lane (lane 0). I tried connecting every lane (0-3) on the cable to lane 0 on the motherboard, but I still got no image and it would not wake up.

Could this be something to do with the motherboard only having a single lane? Or am I missing something?

I've got this far, I'd like to see it through! I have subsequently read of other people being successful in connecting, for example, iPad eDP screens to a PC etc. So why is this being so difficult?

Many thanks.


texts: Sinking 80 mA with a microcontroller without any driver circuit?

texts: I was wondering since a micro controller can sink 20 mA on each pin, if I can make 4 pin ports low by software, and just connect the positive side of the load to Vcc, is this a reliable methodology for driving larger loads? Would the only thing to worry and pray about is that the machine cycle is fast enough to handle the fluctuations of setting all the pins at the same time? Am I on the right track?


texts: Charging capacitor with a diode in parallel

texts:
Suppose we have this circuit:

simulate this circuit – Schematic created using CircuitLab
If we didnt have the diode , we could use source transformation to calculate the charging time of the capacitor just like this:

simulate this circuit
but now we have the diode I cannot do this.How is the charging time calculated?


texts: How much power is wasted with a light dimmer?

texts:
I have my rotational light dimmer and am wondering the logic behind it.
If it is a potentiometer, when fully off, it should be wasting lets say 50V of power if not using a transistor. By logical design:

1) Should it have an extremely low voltage with a resistor and control a transistor to limit large power loss?
2) Is the dimmer a rheostat or a potentiometer? If anybody has a answer, that would be great for my understanding. Thanks!


texts: When is it reasonable to ignore channel length modulation in MOSFETs?

texts:
It is known that for smaller technologies, the channel length modulation effect is more prominent. However, is there any condition (biasing,voltage levels, transistor sizing ..etc) from which we can decide to reasonably neglect the channel length modulation effect in MOSFETs?

In a simple common source amplifier, if ro is much larger than any parallel resistance, we ignore it.

I also read that when Vds of a transistor is much larger that VDS,sat it is important to consider ro (I am not sure why though)

In other words, under which conditions we may assume that the channel length modulation has minimal effect on the gain,drain current etc.?


texts: Altium: Polygon Pour Direct Connect on Vias, Relief Connect on Pads

texts:
I'm not even sure if this should go here on the EE StackExchange or if there's a CAD board, but I'm posting it here just in case. I am working on a 2-sided SMD PCB that has vias and SMD pads. On the pads (which I will be soldering) I need to have a relief connect for the polygon pour of the same net, but I need a direct connection on the Vias of the same net. I currently have all Relief connects:

But in the Design Rules I cannot find an option that would set Vias aside from component pads:

I considered adding all of the vias to a class, but I can't seem to be able to do that either. To make this even more difficult, I have two QFNs with thermal pads that use built-in vias to stitch through the board. These should NOT have a direct connection to the polygon as it will make it much more difficult to solder.

Is there a way to add, say, selected vias to a class? I just need to set a rule for the Polygon Connect to use direct connections over specific vias, and relief connections over the rest of the PCB. Thanks!


texts:
I have an outdoor arduino project I'd like to power with a battery + solar panel. I'm a bit of an EE n00b, so would like to make sure I've got the basics right.

I'm using a 3.7v 1800mAh LiPo battery, with the guts of a SparkFun LiPo charger:
https://www.sparkfun.com/products/8293

I'm using this solar panel rated for 8V open voltage and 310mA short circuit. I'm going to put in a 5.8v zener diode to limit the voltage coming off the solar panel to the charger.

Here's a (rough) schematic of how I intend to wire everything together. Ignore how the charger is wired in, it's there just to illustrate where the solar (vin) and battery (vbatt) go, nothing else.

simulate this circuit – Schematic created using CircuitLab

My question is - can i have the charger running to the battery and the battery going to the arduino off the same line, or do I need something in between?


texts: Is there relation between logic chip names and their internal structure

texts:
I know that for instance an ATMega328 is a 8 bit MCU with 32k of program space, the same can be said for most other MCUs and some other ICs with a direct relation between the name and internal specs. I might be asking an irrelevant question, but I want to know out of interest.

I know that there is the 7400 and 4000 series with there specific voltage or performance specifications, what I don't understand is how the suffix of each series came about, such as a Hex Inverter = 04, or take the 74HC595(8 bit shift register) does the number relate to the internal structure? I understand the 74HC238, 3-to-8 line decoder, its numbering makes sense as to its function.

A CMOS inverter uses two MOSFETs:

or a NAND gate with suffix '00

Were the numbers given to a chip in a consecutive order or in relation to there development or are they related to their internal design?


texts:
The pros and cons of triodes vs screen grid tubes like pentodes and tetrodes are well documented elsewhere.
When it comes to low and medium power tubes both triodes and screen grid tubes are readily available. At the really high power levels like kWs it seems to be an all triode show.

Are high power say pentodes difficult to manufacture?
Is it inconvenient to have more connections to the glass envelope when voltage clearances are considered?
Are screen grid tubes more likely to flashover?


texts: Arduino code - Why do we need to read the rising edge?

texts:
I'm having a difficult time figuring out why we need to read the rising edge instead of using both edges.

We are doing a school lab using interrupts in Arduino code, and I understand that we need the interrupt to read the rising edge, but why are we reading the rising edge?

The question that I am specifically trying to answer is part B of the following:

Write a paragraph explaining how you are measuring frequency.  Be sure to include:

a. why you must use an interrupt.

b. why you enabled the interrupt on the RISING edge, instead of both transitions.

c.  Comment on the accuracy of your Arduino's frequency measurements


texts: Best method for using a PA to drive a vibration table?

texts:
Being relatively new to the world of sound and vibration signal manipulation, I am attempting to drive a small vibe table in an open loop configuration. For preliminary trials (AKA learning how to use the darn thing) my planned method is to:

1.) Synthesize time history for my random vibration PSD

2.) Normalize this data in some way (centered about 0 and +/-1 amplitude..?)

3.) Write the data as analog voltage via NI 9263 + cDAQ

4.) Input into my DSI-1000 power amp

5.) ??

6.) Profit! (Successful acceleration response)

I'm still trying to wrap my head around the fundamentals of a power amplifier. Would I merely send my normalized data as voltages, then adjust the sensitivity dials on my PA until my accelerometer reads my desired level (and make note of that sensitivity setting)? Note, I do NOT have a controller, nor do I want to buy one. I believe that open loop control will be suitable for me.

I realize this is a vague thread, so I apologize. Is there someone who has experience with this that could shed light on what my process is missing?

PS: My power amp datasheet does NOT have this information included. It's pretty barebones


texts: I have a old motor which has no printing information outside. How to measure its input wattage. Its burning on 14v  3.0A source


texts: Implementation of Any Combinational Logic Circuit with a Decoder and some OR Gates

texts:
It is said that a decoder with n input has 2n outputs corresponding to the 2n minterms of the n input variables. An n-to-2n decoder and m OR gates can, therefore, implement any combinational logic circuit.

Can anyone explain more detail about why, therefore, it can implement any combinational logic circuit?


texts:
Im looking for a little help and advice on my code.

Im using C18 in the MPLab environment, PIC18f4520 with Fosc @ 4MHz, and usnig timer0 in 16 bit mode to count to overflow, set the overflow bit and interrupt flag, then jump to ISR and increment a variable 'count'. This is outputted to a port with LEDs attached so that I can get visualy confirmation of the program working.

However, the outputted count is always '1' (i.e. 0x01) and I believe that the ISR is only happening once, if at all.

Any help that you can offer would be most appreciated.

Here is my code:

void main (void)        /*                                                                                */
{
TRISA = 0;          /*                                                                                */
TRISC = 0;          /*                                                                                */
TRISB = 0;
TRISD = 0x00;
RTOS();
}
void low_interrupt (void)
    {
    _asm GOTO timer_isr _endasm
    }
    #pragma code
    #pragma interruptlow timer_isr

void timer_isr (void)
    {
    INTCONbits.TMR0IF = 0;
    count = count++;
    LATD = count;
    RTOS();
    }
void RTOS (void)
    {
    T0CONbits.T08BIT = 0;   // 16-bit timer
    T0CONbits.T0CS = 0;     // increment on instruction cycle input
    T0CONbits.T0SE = 0;     // increment on low--> high transition of clock
    T0CONbits.PSA = 1;      // T0 prescaler not assigned i.e. 1:1 prescaler.
    RCONbits.IPEN       = 1;    //Enable Interrupt Priorities
    INTCONbits.GIEL     = 1;    //Enable Low Priority Interrupt
    INTCONbits.GIE      = 1;    //Enable Global Interrupts
    INTCONbits.TMR0IE   = 1;    //Enable Timer0 Interrupt
    INTCON2bits.TMR0IP  = 0;    //TMR0 set to Low Priority Interrupt
    INTCONbits.TMR0IF = 0;  // T0 int flag bit cleared before starting
    T0CONbits.TMR0ON = 1;   // timer0 START
    while (1);
    }

Thanks in advance for any guidance you can offer.


texts: Power consumption measurement on the bench

texts:
I've been using the Atmel Power Debugger to sort out power consumption issues on some µController based circuits... and have been pretty pleased. Unfortunately, it's limited to a maximum of 5.5 volts and I need to work on some circuits which are a little above that range, up to 18 V.

Can someone recommend a method and or off the shelf hardware to help me get going on DC power measurements in the 0-18 V range?

What are some options for logging power consumption over several hours... maybe as long as 24 hours to evaluate circuit / firmware performance?

A different post (How to Measure Power Consumption on Extremely Low Power Devices?) mentioned the µCurrent Gold Multimeter adapter to utilize with a multimeter, but it's out of stock.

Any suggestions would be greatly appreciated!


texts: STM32F4: WWDG interrupt fires as soon as it's enabled

texts:
I'm doing some coding on an STM32F411 board, used the CubeMX & HAL Libraries for laziness.

I'm trying to get the windowed watchdog (WWDG) up & running, and doing the very basic version (non interrupting) works as expected using this sequence of setting up (straight from the HAL/CubeMX):

/* Reset of all peripherals, Initialises the Flash interface and the Systick. */
HAL_Init();

/* Configure the system clock */
SystemClock_Config();

/* Initialise all configured peripherals */
MX_GPIO_Init();
MX_ADC1_Init();
MX_I2C1_Init();
MX_IWDG_Init();
MX_TIM1_Init();
MX_USART6_UART_Init();
MX_USB_OTG_FS_USB_Init();

MX_WWDG_Init(); // Window == count == 0x7F
HAL_WWDG_Refresh(&hwwdg, 0x7F);
HAL_WWDG_Start(&hwwdg);

while(1)
{
    //main loop stuff
}

This works as expected (I will narrow the window later), but if I change the code to use the "early wakeup" interrupt function (EWIF) - again, all auto-generated from CubeMX - it instantly fires the interrupt:

/* Reset of all peripherals, Initialises the Flash interface and the Systick. */
HAL_Init();

/* Configure the system clock */
SystemClock_Config();

/* Initialise all configured peripherals */
MX_GPIO_Init();
MX_ADC1_Init();
MX_I2C1_Init();
MX_IWDG_Init();
MX_TIM1_Init();
MX_USART6_UART_Init();
MX_USB_OTG_FS_USB_Init();

MX_WWDG_Init(); // Window == count == 0x7F
HAL_WWDG_Refresh(&hwwdg, 0x7F);
HAL_WWDG_Start_IT(&hwwdg);

while(1)
{
    //main loop stuff
}

The MX_WWDG_Init(); call in this case includes the lines to set NVIC / enable IRQ but is otherwise identical:

void HAL_WWDG_MspInit(WWDG_HandleTypeDef* hwwdg)
{

  if(hwwdg->Instance==WWDG)
  {
  /* USER CODE BEGIN WWDG_MspInit 0 */

  /* USER CODE END WWDG_MspInit 0 */
    /* Peripheral clock enable */
    __HAL_RCC_WWDG_CLK_ENABLE();

    /* Peripheral interrupt init */
   HAL_NVIC_SetPriority(WWDG_IRQn, 0, 0);
   HAL_NVIC_EnableIRQ(WWDG_IRQn);
  /* USER CODE BEGIN WWDG_MspInit 1 */

  /* USER CODE END WWDG_MspInit 1 */
  }
}

I tried adding __HAL_WWDG_CLEAR_FLAG(hwwdg, WWDG_FLAG_EWIF); just before the __HAL_WWDG_ENABLE_IT(hwwdg, WWDG_IT_EWI); call in HAL_WWDG_Start_IT(&hwwdg); but it makes no difference.

What have I missed here?


texts: Stopping a DC motor using an H-bridge: forward+backward vs. 'brake'

texts:
Using an H-bridge, you can stop the DC motor at a certain position by applying a 0101 or 1010 signal to the 4 terminals.

You can also stop it at a certain position by driving it forward then backward at very high frequency which make the 'juggling' unnoticed and the motor looks like stationary.

Ignoring all other aspects and focusing on stopping the motor at a specific position...which of these two methods is better?


texts: Simualtion stops at time 0 after a real to real multiplication!

texts:
In my project, which compiles fine on ModelSim, when I try to simulate my code it gives me:

Here is my code for multiplier:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.MATH_REAL.ALL;

ENTITY mult IS
    PORT(
        a, b: IN REAL;
        dataOut: OUT REAL
    );
END mult;

ARCHITECTURE base OF mult IS
BEGIN
    dataOut <= a * b;
END base;

and this is my memory which derives a and b:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.MATH_REAL.ALL;

ENTITY memory IS
    GENERIC(
        memCapacity: INTEGER := 8
    );
    PORT(
      w, r: IN BIT;
      address: IN INTEGER;
      dataIn: IN REAL;
      dataOut: OUT REAL
    );
END memory;

ARCHITECTURE base OF memory IS
TYPE memBlock IS ARRAY (INTEGER RANGE <>) OF REAL;
SIGNAL mem: memBlock(memCapacity DOWNTO 0);
BEGIN
    PROCESS (w, r)
    BEGIN
        IF (w = '1') THEN
            mem(address) <= dataIn;
        ELSIF (r = '1') THEN
            dataOut <= mem(address);
        END IF;
    END PROCESS;
END base;


texts: Driving a motor backwards and forwards using mosfet and Arduino pin safety

texts:
So I want to drive a motor from a handheld drill/screwdriver. And I have managed to get it going using the first schematics, and using pwm to control the speed.
The Zener diode is there to protect the mosfet, and in turn the arduino (as I understand it). No problem so far (afaik) ;)

Now my question is how to "safely" drive this backwards. I am quite certain that the 2nd schematics will work safely, and the Zener diode will still protect the Mosfet. However this requires two relays:

Is it possible to do a protection circuit that would work with only one relay that switches between +12V and GND as per the third Schematics:

Schematics 2 and 3 would make it work similar to a HG7881/L9110 but managing larger loads.

As usual, thanks in advance :)


texts: Is there a minimum length for SATA cables?

texts:
Today I stumbled across a piece of information that surprised me. Apparently there is a minimum cable length for SATA. From Seagate, a reputable manufacturer of SATA devices:
Serial ATA (SATA) data cable lengths

Serial ATA cables are available in many lengths up to 1 meter. Minimum cable length is 12 inches, using shorter cables can cause timing, or noise interference on the cable.

That is all the information they offer, and I could not find much information elsewhere. It is obvious that a cable can be too long: Signals will arrive too late, and eventually become attenuated. This is the first time I hear about cables being too short.
Since they measure the minimum length in inches it makes me think that it is not in the official standard, and something that they have found by trial-and-error, but can someone explain why this would be a problem in a (presumably well designed) standardized high frequency serial protocol?


texts: How do I keep my LEDs from burning out in a magnetic induction coil?

texts:
I built a simple magnetic inductance coil using:

For transmitter:

28 awg magnet wire in a "pancake coil" (flat spiral)
npn transistor (TIP31C)

2 resistors in parallel

battery (tried a 3 volt battery, 2 3-volts hooked together, and 9-V. 9-V got too hot too quickly)

For receiver:

28 awg magnet wire in tight coil
LED

My question:

How can I stop my LED from burning out each time I get it too close to the 9-V battery?

The whole point of this project is to allow someone to basically "play" with the receiver coil and make the LED go to a maximum or minimum brightness at their leisure. If I use the 9-V battery, I get the distance I want, but heat build-up is terrible and the LED burns out if it gets too close to the transmitter.

So I guess a second question:

How do I keep the LED from burning out AND how do I keep my 4 inch minimum receiver distance (for decent light from LED, about half the possible brightness from about 3-4 inches away) and stop my transmitter from getting too hot? (I plan on the transmitter/receiver running for at least a few hours and be reuseable)

P.S. The receiver needs to be as simple as possible, (2 or 3 small parts maximum if possible). And the transmitter can be no larger than the back of the average person's hand. (I was thinking "stacking" the pancake coils together and using 2 6-V power sources to make the magnetic fields addative, but that would increase the weight of the transmitter and I'd like to keep that to a minimum).

If knowing what it is for would be helpful then:

I plan on putting the transmitter in the back of a leather glove, growing borax or alum crystals over the tranceiver, and making the crystals "glow" via magnetic induction for a few wizard/witch costumes for halloween (hence the weird size/weight restrictions).  Also I'm worried about people who may try to "play" with the gloves (with their hands not being in the gloves) and put the crystal with the LED too close to the transmitter, thus burning out the LED (and this would be a major issue as the LED is currently inside a crystal and cannot be replaced).

Anyway, thoughts/suggestions for my 2 problems would be helpful. Thank you.

Schematics that I found online, only difference is that I used the magnet wire for the transmitter pancake coil as well as the receiver.


texts: What is the antenna gain of a mobile phone?

texts:
I'm working on a GSM/3G Project and my team has a small doubt about antenna gain selection.

All along we were using a 3dB PCB Antenna connected via U.FL/IPEX connector.
The antenna does a good job for normal areas where there is cellular connectivity but in slightly far away areas it doesn't seem to latch on to the network.

I have a Moto G (XT1033) 1st gen which latches to the network in the same region. Just to rule out my phone I tested the same site with different phones and they didn't seem to have a problem latching to the EDGE network.

So we were wondering what would the signal gain on normal cellphone antenna be?


texts: Designing reverse and overvoltage protection at 3.3V

texts:
I have a barrel jack powered design that I'm making, but I would like to prevent damage in the case of reverse polarity (sleeve is positive instead of negative) and overvoltage (plugging in a 12V adapter into a device intended for 3.3V). My design will only consume 500 mA worst case, but to clarify, the wall wart I've chosen can provide up to 1.5 A of current at 3.3V.

I'm using a P-channel MOSFET in addition to a PTC fuse and zener diode.

Will this work? Will the zener diode blow in a high overvoltage case due to a slow PTC fuse? Is my selection for a MOSFET correct?


texts: Matched filter realization in voiceband modem?

texts: As far as I understand, Adsl modems perform the signal detection with DSP-made matched filters.  How was the same thing done in voiceband modems, for example the 56k modem?


texts: 1's complement of a number using logic gates

texts:
If I want to code a signed number into 2's complement I should use a XOR gate like this:
(Consider that A is an 8-bit input)

But if I want to code it in 1's complement how should I implement it in a logic circuit?


texts: I'm reverse engineering / hacking a Chinese board which has the footprint for this regulator which i want to replace. I am not quite sure what the package is though, I'm certain someone here does.


texts: RJ45 color code for cable with non-standard colors of T568D

texts: I have a UTP cable with the colors: white-yellow, white-black, white-red and white-purple. I would like to use this cable as an Ethernet cable. I know the color code to make straight through Ethernet cable, using the colors white-orange, white-blue, white-green and white-brown (T568B). Someone knows the RJ45 color code with the colors cable that I have?


texts: Turning off a controller in multi chip pcb

texts:
I have a design question:

How to safely turn off a  controller IC's (CC2533, RTC clock) while other (eg. Atmega8) are running ? Basically to program the atmega without pulling it out of PCB.
Is there any harm done if VCC is removed to a particular chip say DS1307 RTC when its I2C bus is still powered ?


texts: Can A 1-Bit Computer have more than 2 Registers?

texts: I was thinking about making my own minimalist TTL CPU for fun and knowledge, when this question came to mind. Basically, if a 1-Bit Computer can only recognize 2 numbers, 0 and 1, doesn't that mean that the computer could only have 2 registers or instructions? Then, I found the Motorola MC14500B, which is a 1-bit computer that has 16 instructions, with 4 pins for opcodes. Is the MC14500B considered a "true" 1-bit computer, since it has more than 2 instructions, and if so, could I apply the same concept to internel registers where there are more than just 2, but the actual logic going on in the CPU and the memory works on 1-bit? This is a simple question that I need some clarification on, so thank you for your help!


texts:
I was looking the ADP3338 LDO Regulator of Analog Devices and i'm wondering whats the output voltage of this LDO?
http://www.analog.com/static/imported-files/data_sheets/ADP3338.pdf

Is the output voltage same of input?


texts:
I want to use LM317 to make a current source circuit for driving high power LEDs (500-700mA). The schematic in it's datasheet has no capacitor, but in some schematics there are one or two capacitors like the one below

are they necessary? If I omit them can the possible ripples damage the high power LED?

I quote from a forum:

  "Don't use a capacitor on the output when you are using the LM317 as a constant current source.
  A theoretically ideal current source has an infinite output impedance, whereas a theoretically ideal voltage source has an output impedance of zero.

  If you use a capacitor on the output of your current source, then your "real world" current source is further away from the theoretically ideal current source, which is not a good thing."

Is it correct?


texts: LED strip power supply 12V 2A vs. 12V 25A

texts:
I am using a white light LED strip in my 3D printer enclosure. And I would like to use the power supply of my 3D printer to power this LED strip.

The original power supply of the LED strip is 12V/2A
The power supply of the printer outputs 12V/25A

Can I use the power supply of the 3D printer to power this LED strip, or will it overheat the LEDs?

Thanks


texts: Wattage in US vs AU/EU household appliances

texts: This oven is listed in both the US and Australia. You can see that it's the exact same model (BOV845). Yet if you open the specifications, the only difference is that the US model uses 1800 Watts whereas the Australian/European model uses 2400 Watts. Why might that be? Would it mean that the AU/EU version is capable of outputting more power?


texts: I have a question. I want to make 30V/4A hybrid power supply with stepdown regulator LM22679 as an preregulator and LM338 as an linear regulator to smooth voltage. LM22679 would be powered by Mean-Well power supply with output voltage of 36 V. When I want let's say 10V output voltage, from 36V input I make about 14V with buck regulator and then there would be lower voltage drop on LM338 when making 10V from 14V instead of making 10V from 36V. My question is how to simply control output voltage? If I can somehow use LM338 as Vin=Vout regulator, I can simply set only output voltage of preregulator with one potentiometer but I am afraid that i cannot do that. I hope you can understand what i mean. Thank you.


texts:
I need to find a Bluetooth 2.1 + EDR module that will allow a uC to communicate directly over an RFCOMM channel once it has been established.

The problem is I can only find modules which implement the full stack up to the Serial Port Profile (SPP), which is not supported by the device that will be pairing with the module.

Does anyone know of modules that can do this, what they are called, or what/where to search?

Edit: I know it's possible to just by the "raw" bluetooth controller, and then have the uC implement the full stack, and communicate using the HCI. But looking for a simpler solution. If this type of module doesn't exist I'm wondering if there are any Bluetooth stack implementations that would work well on the ARM Cortex-M3 family.


texts:
I'm assembling this addressable RGBW LED strip setup that is 3m long and 60 LEDs/m. I have found no answer to my two questions on other sites or youtube.

(This is the strip I'm using: https://www.adafruit.com/product/2842?length=3)
(5VDC, SK6812)

Every LED draws 80 mA on full brightness. Therefore (80*60*3) the maximum draw of the strip would be 14.4A. I'm definitely not gonna use that much as it has dedicated white LEDs, so let's say that I'll be using 10.8A (60*60*3).

1.) If I hooked everything up like this picture shows:

Wouldn't the roughly 11A from the power supply fry the arduino? And can the strip's leads really handle 11 amps?

2.) How would you suggest that someone set this up? I want to be able to run both the arduino and the strip off of the same power supply.


texts:
Transistor 2n3904
Homemade transformer with 10 turns
Power supply 1.5 v

Schematic:

I think the toroid winding shorts the power supply as it happens with my buck converter.

I think the toroid winding shorts the power supply as it happens with my buck converter.My multimeter shows the positive input and ground shorted,two of transformer are shorted and those are shorted with other outputs of transformer and one of them is connected to the ground


texts: how to convert the difference in voltages into a digital signal

texts: How can I convert the differences between two voltages into a digital signal? ie. if sensor 1 V > sensor 2 V there is a digital one, but if sensor 2 V >= Sensor 1 V, there is a digital 0. I understand that there are methods of converting a single analog signal into a digital signal, but my understanding of a digital signal is that it must always be either high or low. if you convert both into a digital signal, then wouldn't it be impossible to compare them. Or rather, so long as eithers analog voltage is always greater than zero, then wouldn't a converter always convert the voltages to digital 1s?


texts: How to write data to end of line of existing file (STM32CubeMX FATFS SDIO issue)?

texts:
I have successfully coded write data into a CSV file is an SD card using STM32 CubeMS FATFS SDIO interface 1-bit mode.

But I can't find the file append function in HAL FATFS driver to write data to existing file. Is there another way to do this using STM32CubeMX and HAL drivers?


texts: "Break-before-make" SPDT Relay out of 2 SPST Relays

texts:
I require a SPDT relay (changeover) that will switch up to 600Vdc, which presents some problems because on the major suppliers such as Digikey, such a product is not readily available at such a high voltage.

However, there are SPST relays available and I was thinking of using two of those. However, I am concerned because I need the contact to the first line to disengage before connecting to the second line (otherwise I might cause a short).

To make things a little more difficult, I have only one digital control signal available, and would like the switch to connect to either one line or the other based on whether I am outputting a logic 0 or logic 1.

Anyways, all this to ask: does anyone have any recommendations for introducing this switching delay via hardware components? I was looking around for a "break-before-make" design but wasn't finding much luck.

Any help or direction would be appreciated!

Edit: Based on the accepted answer here is the schematic I came up with, for reference. Thanks everyone!:

simulate this circuit – Schematic created using CircuitLab


texts:
I really wish if someone can help me in these three questions:
three -phase balanced load has a 10 ohm resistance in each of its phases. The load is supplied by a 230/400 V three-phase source.
a) Calculate the power absorbed by the load if it is connected in wye (Y)?
b) Calculate the power absorbed by the load if it is connected in delta?
c) What is the relation between these powers?

My attempt for these questions:
a) VLn,max = 230*sqrt(2) = 325.26
VLn= (325.26)/sqrt(3) = 187.79
IL= VLn/R = 187.79 / 10 = 18.77 A
Ieff= IL/sqrt(2) = 13.27
so P = sqrt(3)* VloadIeffcos()
P= sqrt(3)* 230 * 13.27 *cos (0) = 5286.39 W ?

b) the same steps and P = 15934.86 W ?


texts: Can an electric stovetop burner be damaged from prolonged use without cookware on it?

texts:
My partner, who does building maintenance, thinks that it may be possible to damage an electric stove top burner by extended use without a pot or pan because the heating element doesn’t have something to dissipate the heat into.

To me it seems like the heat would just be dissipated into the air, and the element wouldn’t get and hotter than its max setting.

I found some information about thermal regulators, but it’s not clear to me exactly how they work or if they work the same without cookware on the burner. We also have a very old stove and aren’t sure if the technology would be the same.

I have searched quite a bit but mostly found information about people leaving things on the burner unattended and then catching fire, or about faulty wiring, etc. I’m just wondering if a burner with nothing on it could overheat and burn out the element. Will the burner get hotter with nothing on it?

(The backstory is that I occasionally take the cookware off the burner between cooking ingredients so that I’m not damaging the cookware while there’s nothing in it, while I take a minute or two to prep the next ingredients for the pot.)

Edit: this is not a glass cook top, it's regular electric burners. I have viewed inside the oven that the model is J CS66 0W2AD. The serial number indicates it is from March of 1980. The maker is  General Electric.


texts:
I am planning to build a device that will help transfer data from one USB storage device to another.I am planning to incorporate a touch screen interface to provide the user with more control over data transfer.

Will this device need an OS?
What kind of parts are needed to implement an OS on such a device?
(I understand this sub-question may be too broad for this forum, so I'll be glad if you can even me point to relevant literature on and off the internet.


texts:
I'm trying to write verilog code for converting any digit decimal number to BCD number.
My logic: when i read decimal number, i'll extract decimal number digit by digit and I have written module to convert decimal digit (0 to 9) to BCD.
But I'm getting error in the line "dec_to_bcd_0_to_9 a(temp2, bcd_num [(3*i)+(i-1):4*(i-1)]);"
it is showing syntax error in icarus verilog simulator.
what is wrong in my code?

module dec_to_bcd_0_to_9(dec,bcd);
input integer dec;
output reg [3:0] bcd;

always@*
begin

case(dec)
1'd0:bcd=4'b0000;

1'd1:bcd=4'b0001;

1'd2:bcd=4'b0010;

1'd3:bcd=4'b0011;

1'd4:bcd=4'b0100;

1'd5:bcd=4'b0101;

1'd6:bcd=4'b0110;

1'd7:bcd=4'b0111;

1'd8:bcd=4'b1000;

default:bcd=4'b1001;
endcase

end

endmodule

module dec_to_bcd_any_number(dec_width,dec_num,bcd_num);
input integer  dec_width,dec_num;
output [4*dec_width-1:0] bcd_num;

reg integer temp1,temp2;

assign temp1=dec_num/10;
assign temp2=dec_num%10;

generate
genvar i;

for(i=1;i<=dec_width;i=i+1)
begin
dec_to_bcd_0_to_9 a(temp2, bcd_num [(3*i)+(i-1):4*(i-1)]);
assign temp2=temp1%10;
assign temp1=temp1/10;
end

endgenerate

endmodule


texts: Why is my adder giving me the wrong output?

texts:
So I made this circuit right from my professor's notes. It is a carry ripple adder. I've been testing it out and one of the problems it has is this:

When you turn on all three inputs, it does not give you three as an answer. Instead I get two.

Here's simplified output we used to make the circuit:


texts: Computer peripherals to immediately (<5ms) detect digital input state change in C# programs

texts:
The C# application I'm working on needs to be able to be able to call a function within 5 milliseconds of a digital input signal's state change (0V = off, 5V = on).

Rather than using software to repeatedly poll that input's state, I would like some hardware to simply call a software function when the hardware detects a state change (like how hardware interrupts work).

Does anyone know how to do this (what ports to use) on a standard PC tower? Or does anyone know of any hardware peripherals that allow this functionality?

Occasional latencies are fine. I need <5ms average.

I basically need to take as many samples as possible of the input digital waveform. (preferably in the C# program, rather than in a peripheral micro-controller, although I am open to suggestions).

For instance, I found out the Labjack U3 can poll its digital input in less than a millisecond. This is a valid answer to the question, but I am interesting in more answers, especially ones that don't use polling or poll faster than 1ms.

High input impedance would be nice (digital inputs).


texts:
My question is why is the M2 PMOS FET not turning on when Vchrg_ctrl is LOW? My problem is Vload never goes high to charge the Capacitor C1.

I think I am missing something very silly here. Thank you for your help.


texts: Setting up values of ROM in schematics in Xilinx ISE

texts: When I use ROM in schematics, how can I add the content of the memory? Is there a ROM file I can add to the directory?


texts: What electrical attributes determine if signals from a signal generator can penetrate objects?

texts: Lately, I've been reading about all kinds of signal generators (pulse generator, arbitrary function generators, arbitrary waveform generator, waveform generator, frequency sweep generator, PEMF signal generator, etc..).  How does an electrical engineer determine if a signal generator creates signals that go beyond the signal generator or beyond the wires/cords it's connected to?  How can an electrical engineer tell which waves and the specific criteria they must have to penetrate airwaves and objects and which waves/signals remain within a wire (conducting material)?  Take for example pulse waves.  There are several types of pulse waves--rectangular, Nyquist, Gaussian, etc..


texts: How do Software Defined Radios have such big bandwidth?

texts:
I've noticed that the majority of "amateur" SDRs have ADCs with a sampling rate not higher than 20 MSps, but still the HackRF One for example can scan it's whole frequency range (1MHz to 6GHz) in the same time.

How does that happen?

If a SDR were to have a ADC with a 20MSps sampling rate, it could safely sample a signal with a maximum frequency of 20MHz (if quadrature, 10MHz if else). So basically it could work with signals from 0Hz to 20MHz and that range is shifted with the help of a down converter, but it still remains the same width. Do they work with the Nyquist zones or something, somehow reconstructing the spectrum for frequencies higher than the Nyquist frequency?


texts: Making a [4-Pole TRRS to 3.5mm Stereo & Mic Adapter (Male to 2x Female)] from an iphone headphone splitter jack?

texts:
I want an adapter that merges the microphone and earphone 3.5 mm jacks into a single 3.5 mm jack ( basically I want to build the blue adapter thingy):

I have an earphone splitter for iphones that has a 3.5mm jack as shown below:

The problem is how do I connect the  microphone pins from the 3.5mm jack? That is how do I connect the two leads marked "?" (see the following picture for what I want to achieve.)

PS: I am not sure whether the microphone jack pinout is the same as drawn. Anybody can confirm whether this is right (the microphone jack from the headset is rose-colored and the earphone jack is green-colored)?


texts: How to build a three-phase common mode choke in Matlab simulink? Should I use the mutual inductor?


texts: Can I run a microcontroller on the power from a go-kart alternator?

texts: I've been asked to help someone design and build a cool go-kart tachometer, and I thought I'd use a cheap atmel AVR microcontroller to measure the RPM and drive an LED display. The guy I'm working with wants to avoid using batteries if possible, so I'm wondering if I can power the microcontroller and LEDs from the motor's alternator. Apparently it outputs anywhere from 12 to 50+ VAC depending on RPM. I tentatively thought I could use a rectifier with smoothing capacitor and a voltage regulator to provide stable 5V, but I'm not sure if that setup would work well or be reliable. Is there some way I could get stable power for the circuit from an alternator like this?


texts:
After purchasing a TC205 sponge and comparing it with the default sponge that came with my soldering station, I noticed that the TC205 sponge is very thin in comparison!

Is the thin sponge used for a different application? What are the slits on the sponges for?


texts:
I'm trying to design a simple circuit that is fail-safe. I have an infinite number of SPDT switches at my disposal and the situation I'm trying to avoid it having all lamps lit simultaneously.

With two lamps, the solution is quite trivial, and I've illustrated it below. In the circuit shown, it is physically impossible to have both lamps lit at the same time.

I now want to extend this to three lamps: any combination of zero, one or two lamps can be lit, but having three lamps lit at the same time should be impossible. Is this even possible?


texts: 74HCT14 schmitt trigger doesn't improve rise/fall times

texts:
I have a square wave signal whose rise and fall times are too big to feed into another 74xx-series logic chip, such as the 74HC175 flip-flop, which requires rise and fall times in the nanosecond range.

I've tried feeding the square wave signal through a 74HCT14 schmitt trigger inverter, like this:

I've built the circuit on a bread board with components that were just lying around - so it's a bit messy:

Now, rise and fall times doesn't seem to improve when i feed the signal through the schmitt trigger (yellow: input, blue: output):

As can be seen, rise and fall times are roughly the same.
Also, I find it a bit strange that in the two last pictures the output signal begins transitioning before the input signal has passed Vt+.

The data sheet can be found here: http://www.ti.com/lit/ds/symlink/sn74hc14.pdf


texts: Switch current flow from A to B based on C's status

texts:
simulate this circuit – Schematic created using CircuitLab

Hello everyone,
I want the current to flow from A to B if the switch is pressed. What can I do here?

Total newbie here.

Thank you.

EDIT 1: Can't move the switch.


texts: How is the impulse response related to pole/zero-plot?

texts:
I have trouble understanding how you can from a pole/zero-plot say something about the impulse response. For instance I have 2 poles in

  (-5 +/- 8 jw)

and a zero in 0.
How would I know, from just that, how the impulse response would look like?


texts:
I had this final gate that I made. but when I run it in terminal. it says my output is E instead of 0/1. I wanna know why my output is E instead of 0/1.

The circuit should have four inputs: A, B, C, and D.
The circuit should have two outputs: W and X.

You will need to modify it so that the following things are true:

The output W should be a 1 if and only if there aren't two adjacent 1s in the inputs (i.e. A and B, B and C, or C and D).
The output X should be a 1 if and only if there aren't two adjacent 0s in the inputs.

My question is why my output is 0000 E 0, which it should be 0000 1 0?


texts: How does the voltage division on this work?

texts: How does the voltage division of this work? I understanding other types using KVL, but this I am just lost. Im not comfortable blindly taking the answer and would like to know. Or is the answer just flat out wrong?


texts: How to calculate minimum zener current if it is not explicitly specified in the datasheet?

texts:
simulate this circuit – Schematic created using CircuitLab

I'm going to use 1N4740A as a voltage reference in a similar way you see in the schematics above. In textbooks, a zener property called "minimum zener current \$(I_{z,min})\$" is thought, but it is almost never mentioned in the actual datasheets of zener products.

How do I calculate minimum current of a zener diode so that I can calculate highest value of the pull-up resistor \$R\$?


texts: Connecting MIDI patch cable DIN connector shielding and pins 1, 5

texts:
I am building myself a MIDI patch cable. According to resources such as http://www.leadsdirect.co.uk/technical-library/pinouts-wiring-diagrams/din-midi-wiring/ the middle pin of the DIN connector (pin 3) should be connected to the 'shield/screen/earth'. I am assuming it means the cable's shield.

What about the DIN connector's shield? Should that be connected to the cable's shield or left unconnected?

What do you recommend regarding pins 1, 5? Connect them or leave unconnected? Are there any cons to connecting them?


texts: Can we know the limit of the number of times information can be stored/retrieved in computer chips - hard disks and RAM?

texts:
I was wondering whether the memory storage of a single memory area in computer semiconductors is limited in terms of the number of times it can be used. I'm also wondering what will happen to the data in memory when it is nearly spent - will it stop working (RAM) or destroy its data (HDD)?

What is the limit on the number of times data can be stored to digital memory? Can we know how much time is left before it is too late?


texts: How can I distinguish between a clone and a real Arduino?

texts: If I buy an Ardunio from a sketchy place such as a 3rd party seller on Amazon or eBay, how can I find out if it is an Arduino clone or a "real" Arduino board?


texts:
In the question, he told me from the begging that it is an ideal op amp .. so A(cm) =0 !!
How can I find the CMRR then !!

I tried to analyze the circuit to be sure!! And i got the same !


texts:
I have bought a shocking gum which gives a small electric shock when you pull a side, like this one : http://img.weiku.com/waterpicture/2011/10/31/20/Shock_Chewing_Gum_634577515693532881_3.jpg

I wanted to know how it works so i opened it and there are two components i can't identify.

Here is the picture :

It's the black component (maybe a capacitor ?) and the little circular one I can't identiy. Any ideas ?


texts: Arduino spuriously resets with power draw

texts:
I have a simple circuit, pictured below, that uses an Arduino to control two large bidirectional motors via 12V relays. Normally this works a treat, but sometimes the Arduino ends up resetting itself.
I think what's happening is that the motors eat up a lot of power when starting, causing the arduino to have a momentary loss of power wherein it resets. To remedy this, I added a 1000uF electrolytic capacitor, and a 22uF ceramic capacitor. Additionally, I "walled off" the arduino's power/ground planes with 1N4001 diodes so that the motors aren't able to steal charge from the arduino during a power drop.
Looking at the VIN/GND to the arduino, I still see the occasional power drop, but with the diodes/capacitors the spikes are very short and sharp. What's surprising is that these power drops don't always precede a restart as far as I can tell.
My current working theory is that the power drops are corrupting memory or just precipitating instability in the arduino, which is why power drops don't generally immediately cause a restart.
I've spent a few days struggling with this problem, and I'm still completely lost as to what I should do to fix it. I don't understand why there would be sudden loss of power on the arduino when it's walled off with diodes. Any and all help would be appreciated.

Edit 1
Here's the schematic for the motor control. Ambiently relays are on GND, only one is on during a movement. Looking at the scope, I do see some spikes on the gate. I added 10uF ceramic capacitors to the gate lines, but that did not completely fix the restart issue.

And here is the schematic for the power going to the Arduino. I have a diode on the high side and on the low side. The high side diode is to prevent the motors from stealing charge from the capacitors, and the low side capacitor is to prevent the motors from moving the ground plane. The issue persists with or without the low side diode in place.

I don't think that the issue is from the power side, I can unplug the power and the arduino continues to run for roughly two seconds. I've spent multiple days on this, and I have not found anything that makes this circuit reliable. I'm at a loss for what to try.
Edit 2
I think that the issue is that the relays sometimes arc, which causes EMI that interferes with the arduino. I need an RC snubber to eliminate that, but how do I properly connect such a snubber on my circuit?


texts:
I'm working on designing a 2nd order sallen key high pass filter in PSPICE for a school project, but in subthreshold with resistors replaced with OTAs (transamp). Schematics shown in figures below. The two transamps each have a bias current = 100 pA. I've connected it accordingly, but when I simulate, I get the following error:

"Voltage source and/or inductor loop involving V_transamp_2_V1. You may break the loop by adding a series resistance"

I'm not sure why I am getting this error as it is connected the way it should be theoretically


texts: Can I safely run a LED light bulb from a UPS?

texts:
I think I blew a capacitor (heard a pop sound) inside a UPS when I plugged in a 29 watt LED light bulb. It still works, but now the UPS is really slow to switch back to AC power after a brownout.

Model: Tripp Lite SMART750USB


texts:
I am currently working on controlling servo motors with an ATtiny85.
I have a hard time understanding how to achieve a fine granularity for the angles of the servo.

I am using a similar technique as the one stated by KyranF.

A servo angle is determined by the pulse width between 1-2ms of an 50Hz PWM.

I am using Timer 1 with a prescaler of 1 with a 8 Mhz clock. This means a timer overflow(tick) takes (1/8MHz) * 256 = 32 microseconds.

A 20ms period takes 625 overflows. This means my 1ms granularity is 625/20ms = 31,25 = ~31 ticks per ms.

Because a servo angle is controlled by setting the pulse width somewhere between 1-2ms, I can only have a precision of 31/180°= ~6 degrees.

Is there a way to achieve 1° precision ?


texts:
I am using an Omron G3MB-202P SSR to switch an AC outlet on and off as depicted in the below sketch.

This works fine. However, when connecting a phone charger to the "controlled" AC outlet while the relay is off, the charger goes on and off every 1-2 seconds. Why is that so?

I have tried the same out with a different SSR, namely the Fotek 25DA and found that it does not result in such a "reset loop".


texts: Debugging an ARM (STM32) Microcontroller using Qt Creator

texts:
I have been working with STM32 series ARM microcontrollers on IAR Embedded Workbench for a while. For some reasons, now I need to move my works to Qt-Creator (both on Windows and Linux). In IAR EWARM, things are simpler: I've never had to deal with linker scripts or startup files, just open an IAR EWARM project template from ST's Peripheral Library release and with some simple adjustments, it's ready. Anyway, I tried to create a new project for STM32F4 on Qt but I faced with various problems.

Is there anybody that can explain this process clearly, step-by-step? With the related makefile, linker script, startup and system files if possible.

Note: Actually, I have a bunch of specific questions about the issue, but since I think that an explanation of the whole process may be helpful for me as well as other embedded newbies, I decided to ask the question this way.


texts: Modify a 1629 magic eye tube circuit to a 6E5S tube?

texts:
I've an EICO 950B capacitance tester with me. It has an aging 1629 magic eye tube. I have a bunch of 6E5S tube with me. Can you guys guide me with the modification?

I know the first step to this is to reduce the filament voltage to 6.3V for the 6E5S. But something that bugs me is, can a simple resistor voltage drop get it done? I'm worried that this path might have issue which might kill the tubes very fast. Hoping to get some expert opinions here.

link to the service manual:

https://www.kevinchant.com/uploads/7/1/0/8/7108231/eico_model_950b_bridge.pdf

1629 datasheet:
http://www.r-type.org/pdfs/1629.pdf

6E5S data:
https://www.radiomuseum.org/tubes/tube_6e5s.html


texts: Build custom ac-dc power supply- ground wire

texts: I am building a ac-dc power supply and am wondering what I should do with the ground wire from the ac wall plug. Do I ground it to the casing on the transformer? Or should I just leave it unused? Should I tie all the dc grounds with the ac ground wire?


texts: Arduino + Ardumoto : External power source

texts:
I have an Arduino and an ArduMoto. I want to use that to power 8V motors with a 17V battery (using PWM).

It says for the Ardumoto that the VIN used to power the motors is the VIN of the Arduino (limited at 12V). But there is on the Ardumoto a VIN input, with written on the side : VIN Max 18V.

I wonder if I can plug in a 17V battery on this, without a risk for the Arduino ?


texts: Can I connect a MOSFET to an Arduino directly?

texts: I have the following electromagnet and plan on connecting it to the following MOSFET which will be controlled by an Arduino (I'm thinking analogue or PWM). Do I need any other parts (resistors etc.) I'm sorry about the vague question but I don't know much about electronics at all and am just starting. By the way, the aim is to be able to control the strength of the electromagnet (12v 300mA-1A) using the Arduino easily.


texts: Hot Swappable Pullup IC or Standard Circuit

texts:
I am designing a circuit that will interface to many different devices and sometimes the I/O line require a pullup resistor (1kohm) and sometimes not. There are also 7 I/I lines. I need this to be configurable, controlled by an on board MCU (STM32F4). The MCU I have has internal pullups but they are too high of a value.
Digging around the internet, I found this IC:
https://media.digikey.com/pdf/Data%20Sheets/Diodes%20PDFs/PI5L102.pdf
Its pretty close to what I want in an IC but I would like a stronger pullup. Before finding this, the initial idea was to connect a PMOSFET to my rail (where I will pullup to) and have the MCU control that to connect and disconnect pullup resistors as it makes to do. Aside from the IC I found, is there a more practical way to do this? Is there a standard way? Or is just using a PMOSFET for each resistor the best way to go?


texts: What is the correct name of this type of switch

texts:
new here so be kind. What or how do I make a toggle switch stay on as long as current is flowing through it and toggle to off once it stops. I did try all sorts of naming searches in google but came up with nothing.
So for example 24vdc --- turn switch on ----- load  24vdc stops switch toggles to off poistion.
I hope this is clear and thank you in advance


texts:
I need to control 2 DC motors (Maxon RE40) using an AVR (atmega328) through pwm.
I was wondering what is the right way to approach the situation.

Should I increment the duty-cycle at a specific time interval or I should just take care that the difference between two consecutive duty-cycle its not too large?

I want the system to be as responsive as possible but also take care of the motors.

I need to understand the way a soft start should be designed (in software) and what are the possible trade offs.

Thanks


texts: Why route air gaps for voltage isolation on PCBs?

texts:
Learning about PCB design for power supplies, I frequently see boards with routed gaps to separate low and high voltage sections of the layout.

Why go to the trouble of routing an air gap when etching the copper away should create the same level of isolation? Is the breakdown voltage of air much higher than FR4?

I assume that such gaps are used to avoid situations where copper may not be etched away perfectly.


texts:
I am trying to understand a Spice definition of a circuit and transient analysis on it. I have kind of "inherited" this and can't ask the original creator; my Spice memories from university are pretty rusty, and online manuals have not been of much help.

What I don't understand is the first segment here (snippet of whole file):

.define c1 6926.0 6233.4 7618.6
.define r1 0.16661 0.149949 0.183271
....
il   0 98 dc 0 ac 0 pwl (0s 1720.0a ... 6233s 1718.0a 6925s 1728.0a 7618s 1718.0a ....)
...
c01  1 0 [c1] ic= 89.974
r01  1 2 [r1]

In the third segment, I understand that capacitor c01 is defined as lying between nodes 1 and 0 and has initial conditions as given; resistor r01 is situated between nodes 1 and 2.
In the second segment, a piecewise linear current source is defined, with ampere values associated with timestamps.

What does the first segment define? The values next to the capacitor seem to be the timestamps from the current source, but why are they used for defining the capacitor/resistor?

I can provide other details as needed, but didn't want to clutter the post too much with useless information.

EDIT: The suggestion given below in comments is good, but my original question still stands. Is this not standard Spice, since no manual mentions it?


texts: Low Pass Filtered Noise Power Spectra, Showing Low Power @ Lowest Frequencies

texts:
White noise is being passed through a voltage follower, then filtered through a simple first order low pass RC circuit (C=0.5 micro Farad, varying resistance between 2k-10k, ohm depending on RC value tested). This is then recorded using an A2D device. I am then calculating the power spectra using the following python code applied to the acquired raw data:

def FFTF2(raw_data):
    result = abs(np.fft.fft(raw_data)*np.conj(np.fft.fft(raw_data)))
    return result[0:(len(result)/2)]

The result is the following:

This is at an RC of 1ms.  As you can see the very low frequencies are missing power.  Its as if the signal is going through a bandpass filter.  The effect is not as noticeable at higher RC values.

This is the unfiltered noise:

If I use a different op amp in the voltage follower circuit I get the following at different RC values:

RC of 5ms:

RC of 2.5ms:

RC of 1ms:

What could be causing this "cutting" at the lowest frequencies?  Does the power spectra of this filtered noise look "ok", or should the decay be smoother?


texts: How can I repair a Goot PX-201 soldering iron which was exposed to too high AC supply voltage?

texts:
I had a stupidity to plug 100V Japan version of Goot PX-201 soldering iron to 220V. It heated up for a second, but that was it, it no longer heats up.

I tried to disassemble it, hoping to find a simple fuse, but failed to find the failing / burned component.

Any chance it could be diagnosed and repaired at home using multimeter? Or shall I just give up, and look for a new one?

Here is how it looks like under the cover:


texts:
Currently the range for my 125khz RFID reader is about 4 centimeters. I have opened it like below:

Is there any way to increase the range to around 10 to 20 centimeters? For example, increasing the number of turns or something. And if so, how would I do it? Thanks.


texts:
I need to measure C value continuously over time, and save the value to some text file (csv for example). Note that C changes over time, since the system is dynamic.

C are small, varies between 50 to 250pF. I'm planning to use Arduino for logging (using the ADC). Which interfacing circuit would be the best for this situation (that could convert C to some linear corresponding voltage)?


texts: Is there any material that obstructs or resists capacitive sensing?

texts: For example, is there any material I can place over a capacitive sensor, or the finger or conductor approaching it, so that the sensor will no longer activate?


texts: Specifying & operating a TRIAC with a low voltage load

texts:
I am looking to do a circuit to switch a 12 VAC of a device to the ground.
I intend to use a microcontroller to drive the TRIAC.
The goal here is only to short the 12 VAC of a device to its ground.
What kind of TRIAC do I need to do that ?


texts: Measuring small movements of a needle and syringe

texts:
My question is how to measure very small movements of a needle and syringe when injecting. When doctors inject local anaesthetic, they always aspirate (suck back) first to make sure they are not in a blood vessel. My contention, particularly if the aspiration is done single-handed, is that the change in direction of forces on the needle/syringe combination whilst aspirating causes significant movement of the end of the needle - probably several mm - which negates the purpose of aspiration in the first place.

I want to do an in vitro study, in which I have a needle and syringe combination and inject into a piece of meat or similar - and then get volunteers to aspirate / inject under 3 circumstances:

stabilise with other hand and inject directly
stabilise with other hand, aspirate and then inject
aspirate with one hand and then inject

I have hit a block in terms of finding a method of measuring these movements of the needle tip down to maybe 0.1mm. I thought that an accelerometer might be the way but have not found anything small enough to be mounted on the needle tip.

The only other way I thought of doing it was to use a camera mounted side on to the tip of the needle which would be protruding through some sort of artificial 'skin' and then have a graticule calibrated to measure the distance moved.


texts:
-short answer: using an arduino does the Job- "Reading PWM Receiver Signal Using Arduino": https://www.youtube.com/watch?v=ncBDvcbY1l4

I have just started controlling electronic circuits with software, so I have very little experience.

I am searching for a way to get a PWM signal into my raspberry pi. (In particular form a RC receiver, so that I can modify the signal and pass it on to the servos, a bit like fly by wire used by modern airliners. I have already succeeded in sending PWM to the servos using the pca9685).

If there would be a similar device, that can to the exact opposite -reading incoming PWM signals and converting them to a signal I could get via I²C- it would be awesome. I have not found anything like that. If there is no such thing, do you have any idea how I could overcome the problem?

My PWM is around 50kHz with pulses between 900 and 2100 ns. I need at least +-25ns accuracy.


texts: Do I need to supply an op amp with more voltage than I need it to output?

texts: I have an op amp that accepts +/- 18 volts as the supply inputs, but I only intend it to output +/- 5 volts. Is it acceptable to feed in the minimum and maximum output voltages as the supply voltages in this case?


texts:
I have a 2 pin foot pedal that is an NO switch. When i press the pedal down, the circuit closes. I basically need it the other way round. This will be used to operate a switch on a DC motor speed controller which will shut it off. Basically a foot brake.
The way the motor controller is currently setup is the power switch is a potentiometer with a switch. when the potentiometer is in the NO position, the controller is off and visa versa.

I would like to connect the foot pedal instead of the potentiometer as it'll be used in a little car but currently i need to keep my foot on the brake pedal for the controller to stay on!

The way I'm thinking of wiring it is via a relay. 12v battery to pedal pin 1, pedal pin 2 to relay pin 86, relay pin 85 to ground, relay pin 87a to dc controller pin 1 and dc controller pin 2 to ground. does that sound right?

I've tested it with a multimeter and the results seem correct where the circuit is normally closed but once i click on the pedal, the circuit opens. I just want to check before breaking anything.

thanks for any feedback.

EDIT:
this is a crude picture of what I'm trying to do.
Not sure if i need to use pin 30 though?

EDIT 2:


texts: MKT capacitor with ohm value on case markings

texts: This MKT capacitor has an ohm value written on the case. Is it the equivalent series resistance (ESR?)


texts: What is this kind of toggle switch nut called?

texts:
Toggle switches are frequently attached to a mounting surface with a nut that has two indentations on opposite sides.

What is this kind of nut called?
What kind of tool is good for tightening and loosening this fastener?

I usually use needle nose pliers.  They work, but sometimes mar the fastener.