texts:
Like many, I'm trying to design small circuits to do things.  One objective is a device to report home power use.  Such a device is relatively easy.  Powering such a device for the very long term is hard.  Batteries die, solar panels advertise that there's something in the meter box worth stealing, etc.

On the other hand, why can't I just connect a current clamp (http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/Current/ECS1030-L72-SPEC.pdf) to the mains supply and run the monitor from the leached power?

Use a blocking diode and a fairly large(?) capacitor across the terminals of the clamp and add a 3.3V voltage regulator, with ground and supply to the respective sides of the capacitor.

The capacitor won't be "perfect" and should add enough resistance to limit the voltage, I'd have thought.

Anyone tried anything like this?  Would it work?  Suggestions, comments and crazy to add?  (Note that I wouldn't take it amiss if you said "Go home, you're drunk".  This would, right now, be good advice!)

Thanks

Edit to add:  I can't plug in an adapter.  I have the mains cables, but this is at the meter box outside.  No sockets are present.

Edit 2: Target power "generation" would be ~1ma at >5V, feeding a 3.3V LDO regulator.  Power use to be ~0.1mA, with a  <1s pulse at ~40ma every ~2 minutes.  Capacitor to support pulse.


texts:
ModelSim Version INTEL FPGA STARTER EDITION 10.5b
# Fatal error in Process line__45 at
 C:/Users/Desktop/FPGA/division /division.vhd line 59

So I am trying to implement the division by odd number and in my case 3 which is represented in 0.010101 and I took only the first 04 digit after comma.
input*2^-a + input*2^-b + input*2^-c ...

I wrote this small code but each time I multiply the shifted result by constant one or zero I get fatal error in modelSim(during running the compiled module)
website of the question  https://stackoverflow.com/questions/33006842/easy-way-of-dividing-an-integer-by-3
library IEEE;
use ieee.std_logic_1164.all;
use ieee.Numeric_std.all;

entity division is
port (--clock and reset signal
    reset_i     :in std_logic;
    clk_i       :in std_logic;

    sample_i    :in signed(7 downto 0);
      --output signal
    sample_o    :out signed(7 downto 0)
    );
  end division;

 architecture rtl of division is

    signal result_r : signed(7 downto 0);
    signal result_r1 : signed(7 downto 0);
    signal result_r2 : signed(7 downto 0);
    signal result_r3 : signed(7 downto 0);
    signal result_r4 : signed(7 downto 0);
    constant one     : signed(7 downto 0):="00000001";
    constant zero    : signed(7 downto 0):="00000000";

begin

process(clk_i, reset_i)
begin
if reset_i = '0' then
    sample_o <= (others => '0');

    result_r <= (others => '0');

elsif rising_edge(clk_i) then

    sample_o <= to_signed(sample_i, sample_o'length);
    result_r1 <=     shift_right(sample_i,1);--*one;
    result_r2 <=     shift_right(sample_i,2);--*zero;
    result_r3 <=     shift_right(sample_i,3);--*one;
    result_r4 <=     shift_right(sample_i,4);--*zero;
    result_r  <=      result_r1*zero+result_r2*one+result_r3*zero+result_r4*one;
  end if;
  end process;

end rtl;


texts:
I'm try to build a cheap pressure transducer to use with my cheap Hantek 1008c scope for automotive measurements.  When I started taking measurements and testing it, I saw a 40mv peak to peak, approximately 1kHz sine wave riding on the output signal.  I think this is just noise from a cheap transducer, but I got curious as to how I might eliminate this noise.

I'm using this 30psi transducer ( and a 200 psi one ), plus a Drok 2203 buck converter for power.  The transducer has three wires, power, ground and signal.  It expects 5v, and linearly outputs from 0.5v at 0 psi up to 4.5v at 30 psi.  It's ground, and that of the BNC connector which goes to the scope are both hooked up to the Drok's ground.

I've already checked the power supply and it's giving a clean 5v.  I decided to try shunting the AC component to ground using a capacitor between the signal wire and 0v ref, and after experimenting found that a 0.1uF mylar cap worked best, although "best" only reduced the amplitude of the sine wave noise by about 40%.

So I'm curious how one could completely eliminate noise like this?

Here are a before and after.  I tried inserting images, but couldn't so just linked to a 50 sec vid.

EDIT

Here is what it looks like at 5us, without the cap

and with the cap:

I guess there was some kind of aliasing going on at the higher timebases.

So is this 400 kHz sine wave just a defect in the transducer as I suspect, and is there anything I can do to get rid of it completely without affecting the rest of the signal?

EDIT 27/04/2018

First off, the 400 kHz 35 mv p-p noise was indeed coming from the buck converter.  But, I also found that the transducer itself was producing it's own noise.  I replaced the buck converter with a 4.5 volt battery and saw the following:

I got the same result when I inserted the RC LPF right on the output of the buck converter.  The best LPF results were with a 47 Ohm resistor and 1uF cap.  It reduced the amplitude of the buck converter noise to only 3mv, without noticeably reducing the signal voltage, which is completely acceptable.

I may use the 4.5 volt battery, or the buck converter with the LPF, either way I'll need to get a better quality pressure transducer.


texts:
simulate this circuit – Schematic created using CircuitLab

For this AC circuit it is known that $$\omega=10^4 \text{rad}/\text{s},L=0.1\text{H}$$ Find capacity of a capacitor, so that the effective value of current \$I\$ doesn't depend on resistance \$R\$. (Phase displacement doesn't change on \$R\$, we already know that).

My reasoning:
For as long as there is a \$U_{ab}\$ voltage, \$R\$ is going to affect current \$I\$, by Kirchhoff's law. If there is no a-b branch it's still going to affect it because \$U\$ is already fixed. So the only way is if there is no resistance on ab branch, that is if \$X_C=0\$, \$C=\infty\$.

Am I missing something?


texts: Op-Amp output voltage exceeds the power rail voltage (in simulation)

texts:
I'm designing a RIAA pre-amplifier based on the 2 op-amps from an NE5532 package. It seems that something is wrong, because the output of the 2nd stage is giving a 400V output which is way above the power rail voltage. Is it correct?

The 1st voltmeter, XM1, is measuring the input voltage; the 2nd voltmeter, XM2, is measuring the output voltage of the 1st stage; and the 3rd voltmeter, XM3, is measuring the output voltage of the second op-amp, across 100k R7.


texts: How to find the modulation index of an amplitude modulated signal from the spectrum analyser?

texts:
My aim to is compute the modulation index(u) of a amplitude modulated waveform but I only have access to its power spectrum from the spectrum analyser.
I attached an image from the spectrum analyser.

(Note: The spectrum analyser has an input impedance of 50 ohms).
The carrier has a power of -26.6 dBm and the two sidebands have power of -38.5 dBm each.
Quite obviously we know the modulation index must be less than 1 because the carrier has more power - but how do I find the exact modulation index?
My thought process:

First I converted the dBm to watts.
Then I found the voltage using P=(V^2)/R, for carrier and sidebands and we know R would be like 50.
Then I just did modulation index= mp/Ac where mp is the voltage in the message signal and Ac is the voltage in the carrier signal which is computed in step 2.

After doing all this I get a u of 0.25. This sounds kind of correct but what do you guys think?

***clear;clearvars;clc;clearAllMemoizedCaches

m_db= -38.5 ; % message power dBm

mpow= (10^(m_db/10))/1000 % message power in watts

c_db= -26.6;  % carrier power dBm

cpow=(10^(c_db/10))/1000  % carrier power in watts

mv= sqrt(mpow*50) % message voltage

cv= sqrt(cpow*50) % carrier voltage

mu= mv/cv % modulation index= message/carrier


texts:
I have a loudspeaker for my car and I've added an aux cord to the system so that I can play music over it. There is also a microphone attached to it and what I've done is add a 3 way switch between the two so I can either use the microphone or the aux cable. I don't really like this setup and I want to be able to use both at the same time but I'm a software engineer, not electrical, so I'm not sure if tying the voltage of the aux and microphone to the same input is safe.

Here is a diagram with what I currently have:

simulate this circuit – Schematic created using CircuitLab

And I want to remove the switch:

simulate this circuit

My roommate suggested adding diode to ensure the signal only goes one way but said that would lose about .7 volts. I don't like that as the input isn't that strong already and I have to manually amplify music in audacity so that you can hear it. While I'm asking a question, does anyone know how I would go about amplifying these signals through hardware because the microphone you really have to scream into and the aux is generally pretty soft compared to the tones/sirens it can generate. Unfortunately I don't have the schematics to the circuit board which is probably needed for something like that.

Here are some pictures of the circuit board/system:
Circuit http://zyphox.com/misc/pa1.jpg

Front Panel http://zyphox.com/misc/pa2.jpg


texts: How to use Radix UP501 gps module with arduino

texts: I bought Radix UP501 module . but i don't know how to use it with my arduino to output the location data on serial monitor .. How to make it working ???


texts: What is the meaning of || symbol in circuit analysis equations?

texts:
I cannot figure out the meaning of the logical OR ( || )  in this context.
Rin = R1 +R2||R4

in this circuit

This was taken from this video https://www.youtube.com/watch?v=uir9Js1l_r8
*at around 6:00 of the video


texts:
I'm slightly confused about the processor directive in MPASM. Is it essentially the same thing as list? And what is the required value?

If I take an example from the template file, f88temp.asm:

list p=16f88

then this should do exactly the same thing:

processor 16f88

This seems correct but it seems I can do:

processor pic16f88

and that produces no errors. Is this just flexibility from mpasmx or is there a right and a wrong way.

If I put "16f84" in there with the processor set in MPLABX to PIC16F88, that produces a warning: "Processor superseded by command line.  Verify processor symbol." Which is fine but I'd rather that be an error!


texts: Safe amount of current going into my device?

texts:
I am trying to send a signal from an Altera DE2 FPGA to a detector so that I can gate it on and off. The FPGA uses 3.3V logic while the detector uses 5V logic, so I need to increase the voltage on the signal. I am thinking I should use a logic level converter, like this one from SparkFun: (https://www.sparkfun.com/products/12009)

However, I am concerned about the amount of current that will be going into the detector. In the datasheet for the detector (picture below) on the bottom row, it mentions the sink current being < 1.6mA and the source current being < 5.5mA.

Will using this LLC push too much current into the detector? If so, what other method should I use to increase the voltage of the signal without putting too much current into the device? I was also thinking of using an op amp to increase the voltage, one that has a low output current. Which method would be better?


texts: Is it feasible to create computer-like hardware designed to execute a specific algorithm?

texts:
Computers take a set of instructions, and execute them sequentially really really fast.
The number of sets of instructions they could be given is vast.  However my rudimentary understanding of processors and FPGA's makes me wonder if...
1.) many algorithms could be implemented at a hardware level?
2.) these implementations would run those algorithms, dollar for dollar, faster than CPU?
If this is possible, why is it not being done and what are the barriers?


texts: Missing Channel Offset in Sequence 0 Source Room:X Target Room:Y in altium

texts:
I just followed this Page for a simple project but I get

  Missing Channel Offset in Sequence 0 Source Room:X Target Room:Y in Altium

error. I have set/checked all the components channel offsets, but everything seems correct.

Here is my projet:
enter link description here

I will be thankful if you could help me.


texts: What did common mode input voltage do for a fully differential opamp?

texts:
I just want to know, what does the common mode input voltage in a fully differential op -amp do?

e.g. for a Op-amp,

$$V_1 = \dfrac{V_1 + V_2}{2}  + \dfrac{V_1 - V_2}{2}$$

$$V_2 = \dfrac{V_1 + V_2}{2}  + \dfrac{-(V_1 - V_2)}{2}$$

thus, \$\dfrac{V_1 + V_2}{2}\$ is the common part and \$\dfrac{V_1 - V_2}{2}\$ is the differential part of the signal.

There are three inputs, two are the differential voltage inputs. One is the common mode voltage input. I do not know what this pin means? Is it supply an offset?

for the Op Amp that i use is available under the link
THS4524


texts: How are through-hole boards mass-produced?

texts:
I'm familiar with the manufacturing process of surface mount boards. Chips come on reels (very high volume smaller parts), trays, or tubes. They are loaded into pick-n-place machines. The PCB, with solder paste applied, is put into the machine as well, and the pick-n-place (PnP) will populate the board.

I was wondering how this used to be done/is still done with through hole components. Our classic ¼W resistors and such come with their leads sticking out on a form of tape. How are these put on PCBs in a mass production environment? Is this all manual labour, or are there machines for this as well? I've never seen or heard of machines for this, and I can see their round shape causing headaches for the suction cups on the PnP.

We like to say that "through-hole is dead" and "everything is SMT nowadays", but open up most cheap power supplies or even many audio amplifiers (which often have a handful higher power resistors, transistors, ...) and you have plenty of through-hole parts! Hence I was wondering, just how are these populated in high-volume production?


texts: What stats to look for in a surge protector, how to compare them and what are recommended some European surge protector brands (and models)?

texts:
I read that joule rating is more like the lifespan of a surge protector, some don't even list them, for an example the german brand Brennenstuhl only lists their surge protectors with leak through amp rating.

So I am not sure how to choose and pick one, what is good and what is not, there isn't many threads talking about them for Europeans and reviewing them. Here are some stats an APC model (PMF83VT-GR) provides:

But then there is this model (PL8VT3-DE), a more expensive (in MSRP terms) one and it seems only worse, I am not sure why:

The most useful thing found is this link. Along this I hear that the ts_nm surge protection response is a important one, and that the TVSS and let-through voltage is also important, but I cannot find that info on the brennensthul models, so how do I calculate it or it is not possible?

I see very few models of APC has this UL1449 rating and on amazon.de brennenstuhl has good ratings, but I cannot find actual stat numbers for their products, does anyone have experience with them, I want to know if they actually perform well, for example how does this model performs compared to the APC, I kinda don't see a way to calculate that as there is lack of info, or am I wrong?


texts:
I'm looking for simplest possible solution to power a load via USB to male bullet connector.

Requirements:

+5V input voltage
15V output voltage
1,5A output current on the bullet connector
very low cost
low part count
simple and accessible parts (no specialized ICs)

Low noise and ripple would be nice, but isn't obligatory.

The piece is to charge a portable music box via USB.
I have sufficient skills for the assembly but don't quite trust my second-semester EE knowledge. This is my first analog project.
Thank you for your advice.


texts:
I got this Relay: Link

It's a 3V 3.3V Relay "Active LOW" and I want to use it with an Arduino Micro. So far I only had experiences with Box/Printrelais.

I want to power the relay via the 3V Pin of the Arduino and toggle between NC and NO via Pin 12.

I tried it and and worked. Setting Pin 12 to LOW activates the Relay on the NC position.

I am not sure however if this setup is safe for the Arduino and the relay? I think setting Pin 12 from LOW to HIGH puts out more then 3 Volts.

Does the 3V 3.3V Relay description only refer to the coil voltage and is it ok to toggle it via a Digital Out pin without additional resistors?


texts:
I'm trying to get .5 A of current from a mobile phone's DC adapter, which is within its rated specifications.  I am able to detect a voltage of ~5 V DC between the power and ground wires, so it seems like the adapter's working.  However, when I apply a load between the two wires, I can't detect any current flowing with my multimeter (it's set to mA, and the terminals are in the correct sockets).  I've tried putting a rheostat in between (from 0-1 megaohms) the two wires, as well as a very fine nichrome (resistance) wire - no current flows in either case.  Am I doing something wrong, or does the cell phone charger have some sort of safety mechanism built in that prevents it from supplying current to only the phone?

thanks


texts: Difference in Metal Film and Carbon Film

texts:
Hey all I have a WS2812B RGB LED strip that I am wanting to use with an Arduino. The directions HERE state that it's best to use a Capacitor and register in order to have smooth operation.

So I went on eBay and bought a 600pcs 30Value 20pcs Each 1% 1/4W Metal Film Resistor Assortment Kit not knowing that the directions pointed to a kit that was titled Resistor Kit - 1/4W (500 total) Carbon Film 5%.

So, I hooked up the 1000µF Capacitor to the power line and grounded the other end (which works just fine) and also added a 470Ω resistor to the digital pin on the Arduino.

I added the needed code and uploaded it to the Arduino... and nothing happened. I fiddled around with it until I found the cause of the issue - its the resistor I was using. So I tried the 220Ω and it also would not allow the led strip to light up.

So I decided to take out the resistor all together and bingo, it worked just fine after doing so. Now my question to you all is - What is the equivalent of a 470Ω in the Metal Film 1% side since it seems they are using the carbon resistor for this project I am looking at? I really do not want to have to purchase another bag of resistors just so I can have some carbon film resistors - I'd rather use this if I can.

So any information/knowledge would be great! Thanks!


texts: How to wire line out on a record player?

texts:
I found an old record player in a dump, and I'm trying to fix it up, though I only have a passing knowledge of electronics and audio. There are two shielded cables coming out of the internal pre-amp, with the shielding of one of the cables also connected to a pin on the pre-amp, but the plugs have been cut off the ends of these cables. It also has no ground cable.

How should I connect RCA plugs on to these cables: what connects to the ring, and what to the tip?

Do I need a ground cable? What do I connect it to?


texts:
I recently came across a pcb.
This is the picture of the aforementioned PCB.

As you can see, some solder points seem burnt. The copper trace has been removed.

Does this mean the PCB is dead? If I solder the component on the solder points, will it work?

Maybe I should do prework, like remove pieces of solder with solder wick?


texts: Measuring thrust of an ion thruster using a fan?

texts:
I'm currently working on a project and trying to sense the thrust being output by an ion thruster.

Right now I am using a faraday cup to measure the Ion count and figuring out the thrust by this reading, but I'd like to have another sensor to check and verify the faraday cup. I was thinking to use some sort of small fan and using the rotation of the fan to figure out the thrust. It's a low amount of thrust so I don't know how practical this idea would be but I did think of two potential options:

Use a small computer fan and remove the electronics from inside of it with the exception of the stepper motor. That way as the fan turns it generates a current from the moving fan and thus I can measure the current to get the speed then go from there to get the thrust.
Just use a fan with nothing inside and use an external encoder/laser and just count the amount of times a marked blade passes by the laser each second.

Any option seem reasonable, or are there better ways of approaching this?


texts: How to calculate electrical energy consumed?

texts:
I have a wattmeter and motor.
I want to know how much this motor consuming the energy(in kWh) by measuring the power (Watt) every minute.

If the wattmeter shows 500 W for 13minutes and then 0 W (it goes off) for the next 47 minutes. Does it means my motor consumes 0.1083 kWh in 1 hour?


texts: Serial Peripheral Interface - multi slave question

texts:
When implementing SPI communication between a master and multiple slaves, there's basically two topologies to choose from: either resend the same data to each slave, or clocking data through all slaves in chain mode.

My question is this: suppose the master needs to continuously shift the contents of a single register into 16 identical slave microcontrollers at the highest possible speed, so not wasting time in resending the same data or clocking bits through all slaves?

Would it be possible to tie all SS (so select all slaves at the same time) and MOSI lines together and completely disregard (or disconnect) all MISO lines if you are not interrested in any data coming back from slave controllers?

Is there a way to achieve this?


texts: Cheap way of temperature testing my boards

texts: I want to make sure my product will work over a large temperature range of -40C to +75C. I can verify on the low end down to about -18C using a household freezer (which is probably good enough) but I'm not sure how to test it on the high end. Any tips?


texts: Low power Wi-Fi embedded modules recommendation?

texts:
I am evaluating my options for low power embedded wifi modules for an upcoming project, and I was wondering whether the hivemind has had any experience with any of the commercially available ones? The main requirements for me are that it be as low power as possible, and that it has a serial interface (UART/SPI/I2C). I am not considering standalone radio modules.

I am considering:

Gainspan GS1500M
Microchip MRF24WB0Mx
Redpine Signals RS9110-N-11-02
Taiyo Yuden WYSBMVGX4
connectBlue OWL211a

If you have used any of these modules, I would welcome your impressions of them. Also, I would greatly appreciate suggestions for other chipsets or any other related advice.

Thank you!


texts: Flat Keypad or Membrane Keypads are cheap and beautiful Keyboad that can be used in systems. but the question is how can they be mounted in a box or panel?


texts: Why does my ATtiny13 report wrong device ID?

texts:
I am using an Arduino (with ATmega168) as an ISP programmer to program ATtiny13. When I try to do this, avrdude reports:

avrdude: Device signature = 0x1e9406
avrdude: Expected signature for ATtiny13 is 1E 90 07

The -F flag to force programming does not override the ID in this case.

I know I can reset the ID with a high voltage programmer, but why did is the device wrongly reporting its ID in the first place? And why is it an intermittent problem? Every now and then the programmer works fine, but when it doesn't it always pops the exact same erratic ID.

Full avrdude output:

avrdude: Version 5.11.1, compiled on Oct 30 2011 at 10:37:28
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2009 Joerg Wunsch

         System wide configuration file is "/etc/avrdude.conf"
         User configuration file is "/home/jhendrix/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : /dev/ttyUSB003
         Using Programmer              : stk500v1
         Overriding Baud Rate          : 19200
         AVR Part                      : ATtiny13
         Chip Erase delay              : 4000 us
         PAGEL                         : P00
         BS2                           : P00
         RESET disposition             : dedicated
         RETRY pulse                   : SCK
         serial program mode           : yes
         parallel program mode         : yes
         Timeout                       : 200
         StabDelay                     : 100
         CmdexeDelay                   : 25
         SyncLoops                     : 32
         ByteDelay                     : 0
         PollIndex                     : 3
         PollValue                     : 0x53
         Memory Detail                 :

                                  Block Poll               Page                       Polled
           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
           eeprom        65     5     4    0 no         64    4      0  4000  4000 0xff 0xff
           flash         65     6    32    0 yes      1024   32     32  4500  4500 0xff 0xff
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00
           lock           0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           calibration    0     0     0    0 no          2    0      0     0     0 0x00 0x00
           lfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00

         Programmer Type : STK500
         Description     : Atmel STK500 Version 1.x firmware
         Hardware Version: 2
         Firmware Version: 1.16
         Vtarget         : 0.0 V
         Varef           : 0.0 V
         Oscillator      : Off
         SCK period      : 0.1 us

avrdude: please define PAGEL and BS2 signals in the configuration file for part ATtiny13
avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.02s

avrdude: Device signature = 0x1e9406
avrdude: Expected signature for ATtiny13 is 1E 90 07
         Double check chip, or use -F to override this check.

avrdude done.  Thank you.


texts: What does a triangle with a slashed zero in it represent?

texts:
In the block diagram for an RF component, there is a triangle with a slashed zero in it as below:

What is it meant to represent?


texts: I'm getting this error over and over and I don't know how to fix it . Error (12002): Port "S[0]" does not exist in macrofunction "inst8"

texts: I'm working in Quartus 2, trying to use a busmux to select the what to do, but when I click compile I just get this error:


texts: Narrowing line of differential pair for DVI connector

texts:
Is this a big problem with reflections (caused by missing impedance) if I'll trace differential pairs like it showed on picture?
I'm designing DVI driving on freq not more than 640 MHz.
How you can see, I narrowed TMDS_D1+ and TMDS_D0+ signal lines from 0,3mm to 0,150 mm, to pass they into the connector. I need it, because my PCB vendor cannot make gaps less then 0,125 mm. But for compliance with impedance I must do line with/gap 0,3/0,2 mm (distance to reference plane 0,4 mm)


texts: Variable oscillator circuit breaking at certain resistances

texts:
I'm trying to build an oscillator circuit using a schmitt inverter (74HC14). I've got the following schematic:

The plan is to control the frequency by varying the resistance using a 10k pot. I figure using the resistor/capacitor values listed I should be able to get a frequency range between 1.2 and ~200hz.

I've simulated the circuit using circuits.io, and everything goes well until I drop the pot to its lowest setting. At this point the sim shows the IC will exceed its current draw. It's running too fast for me to see by how much (the nature of the circuit means the break is intermittent), but I think it's around 53 mW at the time of death.

I presume this is due to the pot reaching 0 or near-0 resistance, but I'm not sure how to prevent it from shorting the circuit. If i hook up the third terminal to ground on the pot, I then see a break at either extreme of the resistance value.

How should I be limiting the current here?

Thanks,


texts: Problem in DC offset with a summer op-amp

texts:
I've used this circuit as an input stage for a digital oscilloscope. From left to right, the first op-amp provides high input impedance, the second op-amp is used to add DC offset to the signal (which should have no offset), the third op-amp is used to amplify/attenuate the signal.

The problem is when I put a voltage source of 1V on the bottom input of the summer op-amp (the second one) to add a DC offset of 1V to the signal, a DC offset of 2V is added instead. Why does this happen and how can I fix it?

You can view and edit the circuit simulated here.


texts: What's up with the operating voltages 5 V, 3.3 V, 2.5 V, 1.8 V, etc.?

texts:
Integrated circuits seem to have standard voltages of 5 V, 3.3 V, 2.5 V, 1.8 V, etc.

Who decides these voltages?
Why do smaller devices require lower voltages?


texts:
I’m new to Proteus and deciding wether to use it for my current project.
There are a few EPROM chips in my design that do not exist in the Proteus library:

M27C1024 (64Kx16)
M27C322 (2Mx16)

Is it possible to add them to the Proteus library with support for simulation?

Or is there maybe a generic ROM component that I can configure to behave like my EPROM (like set no of address lines, data lines and propagation delays)?


texts:
I have a subckt def:

.subckt test_L1.2u_W0.14u x y
  . . . . . .
.ends test_L1.2u_W0.14u

I define another subckt which calls the above subckt test_L1.2u_W0.14u

.subckt top
Xt1 x1 y1 test_L1.2u_W0.14u
Xt2 x2 y2 test_L1.2u_W0.14u
.ends top

The error notifies that test_L1.2u_W0.14u did not exist.

I create a testbench in which remove the . In the subckt definition, and it runs without error.
So does hspice care about . In naming convention of subckt. If so, could you provide me some docs relating to this?


texts: An adapter for disconnecting the current after a particular period of time

texts:
I want to prepare an adapter which will discontinue the power supply after a particular period of time. The time period will be provided manually using a switch. The time periods are: continuous supply, 1 hour, 2 hours, 3 hours.

So, what will be a good way to disconnect the power after the given time?


texts: TTL NAND gate (totem pole) current and voltage analysis

texts:
I am working on a few practice problems for my course and I am unsure about my working throughout.

hoping for some feedback and guidance from the community as it's not my strongest topic.

Here is what I'm trying to do.

I am trying to analyses the operation of a TTL NAND gate with totem pole output configuration. Therefore I want to find all the relevant currents for both high and low output states.

For output low state

For output high state

Thanks in advance for any help and guidance given :)

Tony


texts: Can I use a reed relay instead of a reed switch with an Arduino to detect when a magnet is close?

texts:
I'm using this device:
http://www.radioshack.com/product/index.jsp?productId=2062478

I found this on how to wire it to an Arduino:
http://gncarduino.blogspot.com/2013/04/reed-relays-why-would-i-want-to-use-one.html

Could I somehow utilize this just to test when a magnet was next to the reed relay? Or will an external magnetic field not trigger a reed relay? (is it magnetically shielded perhaps?)

If this is possible, I'm not sure how I'd alter the wiring in place of device I want to control because I just want to use the magnetic field detection with no device to control


texts: Buck converter inductor calculation doesn't agree with typical application schematic

texts:
Im trying to play around with some buck converters and have found one that I might want to make a circuit with. The IC I want to use is the the TPS53125 in QFN package. It's a dual output buck converter IC which takes between 4.5 V and 24 V.

Data sheet

When I use equation 3 from the datasheet to find the suggested inductor value for regulating 1.8 V with a max input of 24V and a output correct of 4 A I end up with the value of 4 uH for the inductor.

Working:

4uH is somewhere in the range that I would expect and sounds correct.

My problem is that in the example circuit above they use a 1.5 uH inductor although they try to regulate 1.8 V at a max of 4 A which should use a 4 uH inductor if you follow equation 3, but instead they use 1.5 uH:

So now I'm very unsure who is wrong? Is the diagram using an inductor value which doesn't conform to the equation or is my calculation faulty?


texts: Random errors in communication via RFM12B

texts: I am using RFM12B as communication modem with PIC18F4550 on one board as Master board and RFM12B with PIC18F25K50 on two Slave boards. My communication is working but some day when I continue working I cannot receive data on Master board. I was monitoring communication via logic analyzer and Master board receives trash data. Communication is based on periodical sending same packet from Slave to Master. Did anyone had this problem? Suddenly it starts working and next day there is problem again. I tried to change modules, too.


texts: PIC12F simulator: Why isn't the oscillator running?

texts:
I have written firmware for a PIC12LF1572 that I am testing in the MPLAB X simulator.  The program runs and correctly responds to stimuli, except when it needs to wait for a timer interrupt.

After a bit of debugging, it seems that the timer is not counting at all.  That is, TMR1 does not increment.  I have set the timer clock to the low-frequency internal oscillator (LFINTOSC), which runs at 31kHz.  It appears that LFINTOSC is not running; furthermore, examining the oscillator status (OSCSTAT) register shows that no oscillators are running!  This can't be right, as the program is definitely running.  Furthermore, the watchdog timer is enabled, ensuring that LFINTOSC will not be shut off.

Does the simulator accurately simulate the oscillators and use them to drive execution?  If not, then how do I get my timers to run in the simulator?  Or, is this a case of pilot error?  The code that configures the timer is as follows:

// Set up the timer and its interrupt
T1CONbits.TMR1CS = 3; // LFINTOSC @ 31kHz
T1CON |= 0x08; // Turn on timer's oscillator; pin not named by the library (!?)
PIR1bits.TMR1IF = 0;
PIE1bits.TMR1IE = 1;
INTCONbits.PEIE = 1;
ei();

// Interrupt in 1/10 second (31kHz clock).
TMR1 = -3100;
T1CONbits.TMR1ON = 1;


texts:
I have to calculate Vo in this circuit. Unfortunately I am very confuse how to do that.
I know the current pass I(2ohm)= 0 and ix=0.

I choose 5Vx as a super node and because ix=0 then the whole current flows through 1ohm then v(x)=5v. but still I cant get the right answer.

simulate this circuit – Schematic created using CircuitLab

This is my solution of the problem:

$$V_X = 5 (1) = 5 V $$

...


texts: Electromagnet with iron core seems to attract strong neodymium magnet when I want to repel

texts:
I purchased suction electric solenoid cylinder electro-magnet from Amazon
and I purchased neodymium magnets as well.

I connect the magnet to a 12V supply and give it ~560mA. I then put the small neodymium magnet (on the end of a plastic stick) close to the field of the electromagnet such that they repel. I am able to feel the field, but when the neodymium magnet gets somewhat close to the iron core it is drawn to it and sticks to it.

My confusion is, shouldn't the field of the electromagnet be strongest closer to the core and repel with even greater force? Why would it be drawn to it? Did the strong neodymium field realign the domains in the iron core when it got too close, and the get stuck to it?

Please let me know if my question doesn't make sense. I am an engineering student trying to understand the behavior I am seeing. My goal is to control the current of the electromagnet to crudely control the repulsion.


texts:
I'm making a fermentation chamber using a Peltier element (TEC1-12706). As recommended by the data-sheet (\$V_{max} = 14.4 V, I_{max} = 6.4 A\$), I'm using a 12V/3A 4 kHz PWM power supply.

I want to smooth/filter PWM output (e.g., RC circuit) so as to increase the lifetime of the Peltier element. The problem is that I also need to reverse the current direction (for fast heating & fast cooling).

How can this be done?


texts: Which is the best way to connect broken pieces of solar cell to equal 1 solar cell? Below are 3 configurations of how I might use solder to build a cell. Does the configuration make a difference?


texts: Okay so I'm new to all of this and I only have some basic knowledge. My problem is that I have an Amplifier board TDA7492P that outputs 2x25W with a minimum of 4ohm impedance. But I only have one speaker that is 130W max and 35nom with 4ohm impedance. So my first question here is can I even run it? and the second one is how can I connect it to both channels at the same time so I get all the sound.


texts: What do the labels in this documentation mean?

texts: I am looking on page 9 of the TI CC8520 Documentation and I see that there are some capacitors and inductors around the antenna with labels such as C306.  What does that mean?  How can I know the values of these components?


texts:
I need to mix 4 analog inputs with different weights into 4 analog outputs with audio application in mind. This can simply be made using potentiometers and opamps for buffering, like shown on the first pic for 3x3 matrix; I do understand that this schematic is not perfect in many ways (for example, you can't cut off any input completely), but it's good enough to demonstrate what am I trying to achieve.

However, I need to control the matrix digitally, say, using the I2C interface. This can be done using I2C digital resistors, but the schematic will just get huge and costly, as for a 4x4 matrix I will need 16 digital pots. And with even more I/O it just gets ridiculous.

So, my question is: Is there a way to make such a 4x4 controlled matrix (without D/A and A/D conversion!) more compact and cheap? Say, are there any ICs made specifically for this purpose? I could not find any.

EDIT: I've just realised that these digital pots are very rarely logarithmic, and that is kind of what I am looking for also.


texts: I'm organizing a lot of components and don't know what this is.  Hooked up to PS at low voltage and nothing happened.  I can't tell the anode from the cathode.  What is it?


texts: Limits to use an off-the-shelf grounded AC-DC power supply with a two-prong cable

texts:
We are selling a product using an AC-DC power supply manufactured by CUI INC (SDI24-5-U-P5 datasheet). We sold the product in a few European countries but we are currently talking with a new distributor in Japan.
The distributor recommends us to use a cable with a type A plug (cable which could be used) because most power outlets in Japan do not seem to have Earth ground.
The device which is powered by this external power supply does not have any metal parts (if that matters), it is independent (no other devices can connect to it), there is no chassis ground on the PCB either. The PCB can only be connected to the outside world with the power supply DC output.
Even though I believe that this AC-DC power supply is still supposed to work without Earth ground since some houses have terrible Earth grounding (if not inexistent), I have a few questions:

Without Earth ground, does that only mean that the DC output of the power supply will be floating? Or do some filters or other things require the Earth ground to be effective for the power supply to work properly?
Is there any safety concerns using such type A cables (with only two prongs) on a grounded AC-DC power supply?

I think that we could change this power supply to an ungrounded one in the future, such as SDI24-5-UD-P5 datasheet, but we would like to stick a bit with the first one since it was used for CE marking and that we have stocks. But obviously, safety concerns go first !
Thank you!


texts: Will multiple SPI slaves lower data transmission?

texts:
I'm working on a project that requires rather high data transmission to a larger number of SPI slaves.
Will connecting multiple SPI slaves to the same master lower the througput alot? The master wont be able to communicate with all SPI slaves at the same time, so I'm guessing there will be a drop. But how do you determine the drop?
Thanks
Edit: Each slave has a data bit rate up to 8 Mbps. I need 12 slaves connected and have 6 masters matching this.. However, I was thinking of reservering a number of master's for later addition of slaves, should it be needed, and thereby having 3 slaves per master. I understand the point, that each master can only communicate with one slave at a time, meaning that they will share the throughput. This was the reason for my initial question.


texts: Simple Fire Alarm Circuit using transistor not simulating correctly

texts:
there am student of BSSE but we studied Applied physics, our teacher give us project.

Am working on it but when i simulate it, this gives me error at Transistor and Speaker.

here is my circuit
https://crcit.net/c/738382510e074fd987eb47e2a8859541

Thanks, help me to resolve this matter.

here i found article about it!
https://www.electronicshub.org/simple-fire-alarm-circuit/#:~:text=Fire%20Alarm%20Circuit%20is%20a,damage%20to%20people%20or%20property


texts:
I'm a novice to CAN; however, I've hooked things up before via a CAN bus.  From my point of view, it's all just fields of data. I'm trying to move away from my pure-C upbringing and embrace (however awkwardly) Microchip's Harmony framework for a project.

For a CAN interface, there exists a series of "channels". I've seen reference to CAN channels on Google, but they are never described. Can anyone point me to a reference for CAN "channels" or explain how they fit into the Extended Frame Format as I do not see any obvious channel bits.


texts: Why do we have "live" and "neutral" wires?

texts: Our house wiring is AC. I thought that AC means we have current flowing from Wire 1 to Wire 2, after 1s/Frequency it flips and current flows from wire 2 to wire 1 and this goes on and on. I heard something like "Neutral has a 0V potential and only live varies between 240V and -240V" But if that's true shouldn't we have current flowing from neutral to live every 1/30 of a second?


texts:
I'm currently redesigning a delay line circuit. It is implemented on a Xilinx CPLD IC. Minimum delay is about 200 ns and maximum 600 µs, which is enough range for my project. What I want to do is increase delay resolution from about 10 ns resolution to 2 ns or better. Do you know any digital delay ICs to replace Xilinx CPLD? Please consider that as a distance simulator. At the input there is a photodiode and at the output LED. So every nano second counts.
Now there is 100MHz clock, and I know that the simplest way is to replace it to 200MHz or more, but unfortunately this CPLD doesn't have PLL so I think that 200Mhz will be the limit. And in case of replacing it for different CPLD I thought about adding for ex MC10EP195 to increase resolution (MC10EP195 has 10ps step). What do you think about that?


texts:
I'm new to modelsim and Verilog and I have got an error in it:

#         Region: /seqdectorTB
# Error loading design

1.3.v:

module myseqdetector(x,clk,reset,y);
  input x,clk,reset;
  output reg y;
  reg[2:0] ps,ns;
  always@(posedge clk)
  begin
    if(reset)begin
      ps<=2'b00;
    end
    else begin
     ps<=ns;
    end
  end
  always@(ps or x)
  begin
    case(ps)
      3'b000 : ns = x? 3'b000 : 3'b001;
      3'b001 : ns = x? 3'b010 : 3'b001;
      3'b010 : ns = x? 3'b000 : 3'b011;
      3'b011 : ns = x? 3'b100 : 3'b001;
      3'b100 : ns = x? 3'b000 : 3'b101;
      3'b101 : ns = x? 3'b100 : 3'b110;
      3'b110 : ns = x? 3'b010 : 3'b001;
    endcase
  end
  always@(ps or x)
  begin
    case(ps)
      3'b000 :y = 1'b0;
      3'b001 :y = 1'b0;
      3'b010 :y = 1'b0;
      3'b011 :y = 1'b0;
      3'b100 :y = 1'b0;
      3'b101 :y = 1'b0;
      3'b110 :y = 1'b1;
    endcase
  end
endmodule

my testbench 1.3tb.v:
module seqdectorTB();
  parameter clkperiod=100;
  reg x,clk,reset;
  wire y;
  myseqdetector(x,clk,reset,y);

  initial begin
   clk = 0;
   forever #100 clk = ~clk;
  end
  initial begin
    reset=1;
    #101 x=1;
    #201 x=0;
    #301 x=1;
    #401 x=0;
    #501 x=1;
    #601 x=1;
    #701 x=0;
    #801 x=1;
    #901 x=0;
    #1010 x=1;
    #1101 x=0;
  end
endmodule

thanks all


texts:
I am looking into the best practices for EEPROM and Flash memory testing. We are talking about end of line product testing by an ATE. The goal is to identify defect chip before writing memory content.

I have some trouble identifying what tests should be done and what failure mode it would target.  RAM tests usually are more documented, but I am unsure if an EEPROM/Flash may fail the same way as a RAM.

For example, I noticed in the past that one EEPROM that was tested by writing all FF then all 00 had an undetected failure that corrupted a single byte. I know for a RAM chip that if the bus address is defect, we could see that behaviour. My questions : Would it be true for EEPROM and/or Flash?

I believe that doing these test should cover most case, but I can't tell if I might miss a significant type of failure :

Write all FF and read back
Write all 00 and read back
write all 55 and read back
Write all AA and read back
Write random sequence and read back

I would appreciate any good reference that treat the subject (in a concise manner :) )

EDIT : Since I got few close vote, I feel like I need to clarify my toughts. I am looking for information with this level of details and hopefully, some dos and don't from experienced manufacturing expert.

Thank you


texts: How to shift the register while using SIPO shift register?

texts:
I have used this SIPO shift register and I've displayed the pattern that I wanted which is 01011000 but I don't know how to shift it now? How can I make the LEDs move?
I've been told to insert a load to make it shift, but I have no clue how to make a load with this


texts: Which current should I use to determine the Watt?

texts:
I am making a heated blanket and I have some troubles to determine the heat that will be generated.

Resistance:
Let say, I use this heated cable with a resistance of 0.3 Ohms/m*.
If I am using 10m of this cable the resistance will be 3 ohms.

Voltage: I will use a AC adaptator with a voltage of 19V.

Current: So the current that will be drawed is 19/3 = 6.3A

But my adaptator delivers a current of 3.16A, so which current should I use to determine the Watts that my blanket will output? 3.16A or 6.3A?

My guess is that it will be limited to 3.16A but that's where I get confuse because it seems that the length of the cable doesn't count anynore (if it's below 20m) :

a 1 m cable should draw 63.3A (at 19v and 0.3 ohms/m) but with a input current of 3.16A, it should only draw 3.16A.
a 15 m cable should draw 4.22A (at 19v and 0.3 ohms/m) but with a input current of 3.16A, it should only draw 3.16A.
a 20 m cable should draw 3.16A (at 19v and 0.3 ohms/m) but with a input current of 3.16A, it should only draw 3.16A.
a 30 m cable should draw 2.11A (at 19v and 0.3 ohms/m) but with a input current of 3.16A, it should only draw 2.11A.

This seems to mean that A 1m cable or a 20m cable will generate the exact same heat but a cable longer than 20m will start to generate less heat.

Could that be correct because it doesn't make sense to me and I can't find where is my reasoning mistake.

Thanks a lot for shedding some light on this!

*I could only find the resistance per m of this cable on a forum. But for all the other cables I looked for, I've never found the resistance/m. Why the sellers never give this info? It is a specification too obvious to notify?


texts:
I am using the ACS758KCB Hall Effect sensor for a project.  On the front page of the Datasheet it list a .1uF capacitor between Vcc and GND, in addition it lists a capacitor, Cf, between GND and VIOUT.  It says that CF is for optimal noise management, with values that depend on the application.  I am very new to electronics, so I do not know how to calculate the value for optimal noise reduction.  Is there a specific formula?  In addition it specifies Rf, what determines that value?

Thanks for any help, I really appreciate it,
Joel


texts: What are the drawbacks to a Vcc (positive voltage) plane?

texts:
I'm familiar with using ground planes when designing circuit boards.  I've started used power planes for the predominant voltage in a couple of my designs, and I'm wondering if that's a bad idea.  I'm only working with 2-layer boards, and I've found that putting a ground plane on one layer and a power plane on the other layer makes placing components much simpler.  I've been building low-density boards with only low-frequency digital signals, and very few (if any) analog signals.

What are the pros and cons?


texts: What is the best way to sense if a climbing hold is being used by a climber?

texts: I am designing a climbing wall game that gets what holds are being used as inputs. I'm currently planning on using a Kinect sensor to tell where hands are relative to holds and capacitive touch sensors embedded in the hold to verify that the climbing hold is actually in use. But I'm worried that I'll get too many false negatives if someone grabs a climbing hold in an unexpected way. Any thoughts on other solutions? maybe a pressure sensor?


texts: Part numbers on Johnson motors don't match their catalogures

texts:
I've bought three motors which look like cordless drill parts, DC. I intend to use motors 1 & 2 to drive the left and right sides of a robot, and the third will probably be useful for a future iteration. All I have at present is this photo, ...

... but it clearly shows the following markings:

Motor 1 (black plastic gear)

70001
JOHNSON
3D2212

Motor 2 (same as motor 1)

70001
JOHNSON
3D3341

Motor 3 (slightly larger, metal gear, shaft does not extend beyond the gear)

1070033
JOHNSON
3E3731

Johnson Electric's part numbers have the format AA000AAA, which matches none of these markings. Are these older models, or am I using the wrong search terms?


texts: How do I know the resistance of a logic level MOSFET transistor?

texts:
I have recently gotten into the microcontroller scene, and I have been stumped with a question all day. My microcontroller's GPIO pins cannot handle more than 20ma; I want to connect a MOSFET transistor https://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_783455_-1
to my microcontroller, so I can control a larger circuit. How can I tell how much resistance the transistor adds to the circuit? I feel like I need to know this so I can use V=IR to calculate the resistor I need to make the circuit safe for the microcontroller.


texts: Ethernet, RS485, CanOpen how to choose the right for robotic Arm

texts:
I have a question regarding the communication protocol and physical layer of how to connect the motors of a robotic arm.

I have 4 servomotors, Brushless. I need to select a motor drive for each one. The motors are: M1 shoulder- M2 elbow- M3 wrist- M4 thumb
in a daisy chain. I've seen that for similar configurations, people either choose RS485, or Ethernet or Ethercat or CanOpen, or even RS232.

How can I decide about this, which one to choose? Could someone summarize the drawbacks and advantages for these above?
I don't have very high requirements for the speed of the motors, I will use them for simple and slow rotations, and expect a power of 30W for each motor. Of course I would prefer the simplest option with minimum number of wires and I would try to avoid to much heating. I really need robust cables because the arm is moving.

Also considering that I will also embed a camera, is it better to consider Ethernet?

I am asking the above, because I see that sometimes people support RS485 over Ethernet, ie. Robotiq, but I also see solutions for Ethernet and even RS232 in some cases.

Thank you so much in advance ! If you need more details, I will comment back, but this is a rough idea I have right now.

thank you for your reply. I think that from these three, CAN is less expensive, Ethercat is the most expensive but also more robust, and RS485 is somewhere in the middle? Can you tell a price comparison more or less?

Then the issue is whether I need full or half duplex. In full I would opt for Ethercat or RS485. But which one of the two is easier to implement?

CAN would be also more simplified in terms of wires, and considering the fact that most microcontrollers have more often Can ports than RS485. But CAN is half duplex, and I think it would be important to have the simultaneous send and receive at the same line, for the motors in daisy chain, no?

Thank you in advance !


texts:
I'm building a power supply, and I'm trying to see if the LM2679 will fit my needs. I like how it's similar to the LM2596 as well as the fact that it has a pin to limit the switch current. However, I have a question regarding the relationship switch current limit and the max output current.

For reference, my test schematic is below. It outputs 5 volts ideally, and it is set to give out 1 A. I adjust the current to the load with switches and resistors, incrementing the current to the load in 0.25 increments until it hits 1A or goes over it. Looking at the waveforms, as it hit 1A, the output voltage lowers in order to adjust for the increasing load, which is what I expect. However, what I'm confused about is the relationship between the switch current and the output current going to the load.

The datasheet states that the peak switch current is equal to a factor of 37,125 divided by the adjustment resistor, Radj. It recommends that for the full temperature range, this limit must be greater than 50% of the max load current. So, assuming my max load is 1 amp, that means the max switch current is 1.5A. Using that value, Radj = 24.75kOhms. I would think that ideally, the load current would be able to tolerate that limit, but as you can see, the voltage is dropping as the load is reaching 1 amp, perhaps even before that. As the load goes past 1 amp, it peaks but the current goes down and kind of settles. I understand that the peak switch current is not the max current limit that can go to the load, but is there a general rule-of-thumb of sorts with regards to the relationship between max load current and the switch mode current?


texts: Designing a senvitive frequency to voltage converter

texts:
I need to make a battery powered frequency to voltage converter that will monitor very minor frequency changes, around 100Hz with base frequency of 3-5MHz (may vary during operation); something like a very wide band FM demodulator. I found this circuit and modified the current sensor for adjustable gain and positive F-V dependence and got pretty high sensitivity, 270μV/Hz:

I can't figure out how to remove the DC component from the output signal because I need only small frequency changes, not its absolute value, so I need some kind of AC coupling and I can't just place a capacitor at the op-amp output because with such sensitivity 5MHz base frequency will require 1350V of op-amp supply voltage.

Maybe you can suggest me some other sensitive F-V circuits? Tried FM to PWM circuit using monostable multivibrator; D flip-flop + XOR gate quadrature detector, they have too low sensitivity due to very small duty cycle changes.


texts: Best sensor for measuring rotation angle?

texts:
I've come into an existing design that uses a 2D accelerometer chip to measure a board's rotation angle around a shaft.  The board is attached to a motor that drives a gearbox that rotates the shaft, so the motor and board rotate with the shaft.  Deriving the angle and calibration of this device is quite complex, is there a simple part out there that say has a high level serial interface that can just tell me the rotation angle?  Desired accuracy would be < 1 degree.  It's for a solar tracking application so angles are between -85 and 85 degrees, speed of rotation is quite slow.

Thanks if anyone can help,
Fred


texts: Can MCP16251/2 DC-DC step-up converter tolerate higher input voltage than the set output voltage?

texts:
I am trying to figure out the best possible circuit for MCP16251/2 feeding from 2 AA batteries in series with an output of 3.3v. MCP is extremely efficient boost converter with very low quiescent current which is ideal for my low-power battery application, however my problem is that two fresh AA batteries in series can potentially output higher voltage at the beginning of their lifespan than the Output setting of 3.3v used in my MCP16251/2 set-up. What are the potential consequences of having this overvoltage on the input pin? Unfortunately the datasheet does not mention anything for such scenario except for:
"Output Quiescent Current: < 4 µA typical,
device is not switching (VOUT > VIN,
excluding feedback divider current)
For VIN > VOUT, VOUT will not remain in regulation."
...and I am not exactly sure how to interpret that. Will the chip just act as a pass-through or act funky in any way?
I suspect that the converter just won't regulate any voltage and act as pass-through, but just curious if this set up can damage the boost converter in any way? Any suggestions - theoretical or based on experience would be highly appreciated!
Attached is my current schematics based on somewhat improved reference design:


texts: FFT Frequency Bin - Impact on Energy Totals

texts: If I reduce the number of samples used for an FFT (increasing the width of the frequency bins), is it correct to say that the energy in two bins with smaller frequency bins (eg. 10kHz-20kHz and 20kHz-30kHz) is equivalent to the energy in a single, larger bin (e.g. 10kHz-30kHz)?


texts: Ceramic Capacitors vs DC Bias - Derating rule of thumb misleading?

texts:
Premise

Ceramic capacitors with Class 2 dielectrics (such as X5R and X7R) usually show a reduction of its capacitance value as the applied bias voltage increases. This behavior is more prominent in higher density capacitors that feature high values in small packages.

How to deal with this behavior has been incidentally discussed in some questions on how to choose the Voltage Rating of the part. Of course, reading the datasheet and asking the manufacturer is the ultimate solution. However, I think the common rule of thumb "derate ceramic capacitors by 50%" is misleading and does not help for this behavior.

Analysis

Here is what I've found by playing with the tools from Murata and KEMET manufacturers and in some application notes/posts:

The most common behavior is that the Voltage Rating does not affect the Capacitance Change curve at all. In other words, a ceramic 100nF 0603 loses the same percentage of its value at 10V (e.g. 30%) regardless of being rated for 25V, 50V or 100V. See this Maxim application note.
In other cases, increasing the Voltage Rating reduces the percentage loss (see this question).
In some rare cases, I have found 100V capacitors losing more than lower rated equivalents.

Discussion and questions

Back to the "derating rule of thumb", choosing a "Voltage Rating (DC)" about twice the value of the maximum expected operating voltage is a good guideline to reduce part failure, but generally does not seem to help with the capacitor not holding to its nominal value.

Of course, when the capacitance value is critical, careful analysis of the datasheet is the way to go.

How do you approach this kind of design choice? Senior designers will have their own rule of thumb based on their experience: I'm interested in those!

What about less critical components such as the very common 100nF (decoupling) and 10uF (bulk) capacitors? If the package is small, they could be well below their nominal value.

Do you care?
Do you select a higher value capacitor (with the same package and possibly a lower voltage rating) that will lose more in percentage but will end up with a higher capacitance value?


texts:
I am an avid Digikey-goer and I was looking for a push button that I needed for a project. I am unsure whether the phenomena I want in this part is explicitly marked on the product, or searchable on Digikey, or what the feature would even be called.

I am not looking for a product recommendation, I am looking for the knowledge of how to search for and find this kind of device. This means either terminology, tips, or "you can't select a device off of this feature"

I need a push button (NO), but it has to operate in a way where the internal contact has a sort of 'hysteresis'. I want this action specifically and only for this action; the user knows exactly when the circuit closes and opens, by the clicks inside the switch

I've noticed this mechanism in microwave interlock switches, of which I will describe further:

As the user goes to push this interlock switch, the switch doesn't close until there is enough force to overcome the entire spring action. When this force is achieved, the contact inside the device snaps closed in an instant, making a clicking sound, and definitively closing the switch.

When the user releases their finger, the force on the button decreases, but the switch still remains closed until enough force is let off, and then the internal contact immediately fully opens up again.

Basically, I need a switch that clicks when it switches into the on position, and clicks again when it switches into the off position, with each click being directly from the internal contact making the connection.

^ The cheap little black momentary buttons do not have this feature, as they are meant to switch things with their rising edge; Being pushed in. The release of this button is not useful to me, as the click happens at a different time than the disconnect of the switch:

How may I find a push button switch that exhibits the aforementioned hysteretic click feature?


texts: PWM commutation strategy for Sensorless BLDC

texts:
For brushless DC motor, we use 6 step commutation.
For voltage control, in each phase, PWM is used to drive the Bridge MOSFETs.
And for the sensorless algorithm, Back EMF of non-energised phase is measured.

I have found 2 basic PWM strategy, Can you explain which one better and why?


texts: Basic circuit to turn on LED when input detects signal (for guitar)

texts:
I'm looking for a basic circuit snipping which can either turn on an LED or give a positive voltage when input signal from a guitar is detected. Basically, I have an existing circuit where an effect (volume swell) is activated with a momentary switch. As long as you hold down the switch, the effect is on. When you release, it is gone.

I'd like to be able to accomplish this without the use of a switch and instead use the presence of a signal to operate this switch.

The switch simply connects a transistor emitter to ground, giving me several options of how to complete this circuit. My first thought was some sort of op amp based comparator which could be connected to the base of another transistor, with the collector connected to the emitter of the previously mentioned transistor, and the emitter to ground, so that when an input signal is detected, the comparator goes high and feeds the base, completing the circuit. But I don't know how accurate an idea this is.

I also thought about using a logic chip to feed the transistor, I have a lot of CMOS 4xxx chips so one of those might come in useful.

I wasn't sure exactly what to google to get this to function though, the closest thing I could think of is a noise gate, which is used to only allow the signal to pass if it is above a certain amplitude, such as this one. Is there any way to implement this?

The original schematic I'm working from is here - the switch labelled S1 is the one in question.


texts: Voltage measure problem in charge controller

texts:
1: I not understand the procedure of measuring SOLAR and BATTERY voltages. The time the MOSFET Q1 ON, the voltage will be nearly the same on solar and Battery side even if we start to charge the battery from low voltage level...so how could we measure the battery and solar voltage separately while MOSFET is ON???
I thought that we might measure the voltage of battery in zero period of the input PWM signal but is this time enough for adc and to make battery return to its actual voltage level.?? my pwm frequency is 700KHZ and Clock Speed is 4MHZ..
2: And one more thing If PV negative pass through the MOSFET, during the MOSFET OFF period PV ground and BAT ground disconnect. Will the microcontroller read PV-ADC accurately …??


texts:
I am asked to design AND gate using transistors on Multisim simulator
AND Logic Gate: Design and implement AND Logic Gate, which gives high output voltage if and only if its two inputs are at a high voltage level.
should be implemented using BJT transistors.
High voltage level: 3-5 Volts
Low voltage level: 0-0.7 Volts
Vcc= 5V
I should analyse the circuit and get all the resistors value. Can someone help me doing it please ?


texts: Computer power supplies usually have higher efficiency on 230V than on 115V. Why?

texts:
As seen here in the example, this particular power supply (and most others too) has higher efficiency when running on 230V. Given that computer power supplies are usually required to output a combination of 12V, 5V, and 3.3V DC, why is it that stepping down from a higher AC voltage is more efficient? It seems counter-intuitive.

Also is this a result intrinsic to the process of converting AC to DC, or is it a compromise that manufactures settle with for compatibility? In other words, if someone is to build a power supply that only works on 115V, is it more difficult to achieve the same efficiency as one built only for 230V?


texts: How does this circuit light an LED simply by heating a coil?

texts:
I've been watching a YouTube video and wondered how the circuit lit an LED just by heating up a coil with a lighter.

Here's the circuit diagram. "Copper wire" is the coil I'm referring to.

(from https://youtu.be/ZoCRG1vK_38?t=7m5s)

Here's the photo of the coil being heated and an LED lit.

My guess is,

the coil was heated up.
electrons in the coil were released by thermionic emission, creating a positive electric potential in the coil.
a very tiny current flew from the coil to one of the transistors.
the current was amplified by the two transistors and drove the LED.

But I'm not sure about the thermionic emission. The most famous example would be a vacuum tube but that is vacuum. This one is in the atmosphere.

Am I correct? If not, how does this work?


texts: How to get rid of static electricity on a plastic slide

texts:
I've got a indoor spiral slide which appears have a large amount of static building. It frequently gives little shocks to people going down the slide. I've also got WS1825 addressable light strips on the outside of the slight which go haywire when someone goes down the slide. I believe this is because of the static charge.

As I understand it, I need to ground the slide to provide a way for the static electricity to reach earth. But since this is inside, that's easier said then done.

Is there a good way to get a ground to earth in this situation? Do I have any alternatives?


texts: What determines the phase difference between two voltages at an AC bus?

texts:
At an AC bus, the power flow is given by the following equation :

In normal operation, the voltages (V1, V2), as well as the inductive resistance (x), are constants. So the parameter δ defines the power flow.

I would like to ask if the value of δ is constant. If not, what are the parameters that determine its value?


texts: Sound measurement in arduino - error when decreasing the sample window

texts:
So I found this code already available and works fine but when I decrease the sampling window to 0.25ms, the serial monitor is not able to identify any sound and keeps showing the same value always. I have tried changing the millis() to micros() and have also tried quite a few values of signalmin but it does not help. Any idea what has to be done for this small sampling window ? The microphone I am using is czn-15e.

const int sampleWindow = 10; // Sample window width in mS (50 mS = 20Hz)
unsigned int sample;

void setup()
{
   Serial.begin(9600);
}

void loop()
{
   unsigned long startMillis= millis();  // Start of sample window
   unsigned int peakToPeak = 0;   // peak-to-peak level

   unsigned int signalMax = 0;
   unsigned int signalMin = 1024;

   // collect data for 1000 mS
   while (millis() - startMillis < sampleWindow)
   {
      sample = analogRead(0);
      if (sample < 1024)  // toss out spurious readings
      {
         if (sample > signalMax)
         {
            signalMax = sample;  // save just the max levels
         }
         else if (sample < signalMin)
         {
            signalMin = sample;  // save just the min levels
         }
      }
   }
   peakToPeak = signalMax - signalMin;  // max - min = peak-peak amplitude
   double volts = (peakToPeak * 5.0) / 1024;  // convert to volts

   Serial.println(volts);
}

`


texts: How to continuously vary inductance in the range \$[-A, A]\$, A>0?

texts:
I require an inductor whose inductance varies continuously as a function of some parameter \$p\$, like a bias voltage or something else that is easily user-controllable (not frequency as I require it for something else). It may look like \$f(p) = a\,p\$ for a certain range \$p \in [-b, b]\$. Also, \$f(p)\$ needs to be negative for some range of \$p\$ and positive for another range. I have an idea about this but if anybody can suggest something better and less complex, that would be great.
Let say we can vary the inductance of some component \$Z_1\$ by varying \$p\$. I came across something called Negative Impedance Converter (NICs) which can be used to get an effective negative impedance (hence an effective negative inductance) in the circuit. I thought of using \$Z_1\$ in NIC and then another \$Z_1\$ in series with the NIC to get total impedance \$f(p)\$:
$$
f(p) = f(p_2-p_1) = Z_{NIC}(p_1) + Z_1(p_2)
$$
Here, \$p_1, p_2 \in [0, b]\$ can be varied independently and can be set to 0 appropriately to get \$p \in [-b, b]\$. So, if you can think of some component \$Z_1\$ whose inductance can vary continuously wrt some parameter, I think this can work.
I'm not much familiar with electronics so I don't know if something like this even exists. We can vary inductance by varying the core of the inductor, but I don't think that will work in my case.
EDIT 1: Background
I adding some details on the problem that I am trying to solve, as the comments suggest this might help. This is actually a physics problem. I am using electrical circuits of inductors and capacitors to model some properties of graphene. The equations that I get for the circuits the similar to Hamiltonian of graphene. Here, the inductances and capacitances act like some parameters in the Hamiltonian and I want to vary these parameters to see how the behavior of the system changes. These parameters can also have negative values, this is why I'm trying to use NIC so that I can get an effective -ve value in the equations. What I want is a way to continuously vary these the inductances and capacitances (such that they can also have negative values) wrt a parameter. For varying capacitances, I think use of varicap diodes might help (but not sure about it). But I couldn't find something similar for inductances.


texts: Wall-warts and power supply current capacity

texts:
How are some of these power supplies in consumer electronics (wall warts) able to achieve output ratings of 9V @ 3000mA with such a small footprint? I know surface mount components can help with this but what makes the difference? Is it the type of transformer, or is this just one of the advantages of switchmode power supplies?

Most transformers I find at the local electronics store have current ratings of around 12-18V @ 300-1000mA.  And even to achieve 1amp the transformers get pretty beefy. I want to make a power supply with the current capacity of one of these wall warts so I'm curious.


texts: Power-up Initialization of HD44780 LCD Module

texts:
I'm using an HD44780 clone LCD module a KS0066U. Everything works ok on the module except when I rapidly power cycle the device (on->off->on). For some reason a very short interruption in the power causes the display module to improperly initialize as a 1-line LCD instead of a 2-line LCD display. What would cause this behavior? Is there any way to prevent it in software?

EDIT: I'm using the display controller in 4-bit mode not 8-bit mode.


texts: Is the Raspberry Pi Pico pinout compatible with the Arduino Nano?

texts:
I could not see any Information regarding the pinout compatibility in the documentation:
https://www.raspberrypi.org/documentation/pico/getting-started/
To what extent is the  Raspberry Pi Pico pinout compatible with the Arduino Nano?
The footprint of both boards looks very similar. Many Thanks!


texts: writing Keysight Binary Arbitrary (.barb) waveforms

texts:
Keysight 33600 waveform generators load waveforms in either .arb (ASCII) or .barb (binary) formats. For large waveforms with more than ~10M samples .barb load much faster.

How can I create .barb files from my computer? (excluding the Keysight Benchlink software).
I am looking something similar to this Tektronix .tfw creating code.

I can create .csv waveforms and import them as .barb using the device (this is very slow).
When looking the contents of the created .barb in hex, I see for example:

0000000: 0100 0000 0000 0000 0000 0000 0000 f87f
0000010: cdcc 8c3f 9a99 993e 0000 80bf 0100 0000
0000020: 64b8 0b41 b415 ea40 0000 0000 0200 0000
0000030: 4c2f e540 00f9 1500 31ff ffff 0180 67e6
0000040: 67e6 67e6 67e6 67e6 67e6 67e6 0180 0180
0000050: 0180 0180 0180 0180 0180 0180 0180 0180
0000060: 0180 0180 0180 0180 0180 0180 0180 0180
0000070: 0180 0180 0180 0180 0180 0180 0180 0180
0000080: 0180 0180 0180 0180 0180 0180 0180 6626

I recognize how the data are encoded, and I recognize the bytes that contain the number of samples (00f9 1500 = 144000 in the example).

So my question is where can I find how the header of the .barb files is encoded?


texts: Multiple MCP41010 Digital Potentiometers Work From One CS Signal

texts: tell me please, for example, I control for example any parameter of the sound path of the guitar pedal with the help of MCP41010 and I need to make a dual potentiometer of two single-channel chips for the right and left channel, probably it does not make sense to send the same CS signal from different digital pins arduino and I’m can combine two CS inputs MCP41010.


texts: How does current flow in this circuit, and why?

texts: I'm new to EE. I know this is a simple question, but I would like to know how the current flow in this circuit. My textbook says that the current does not pass through the capacitor, but I don't know why. Any help is appreciated, thanks!


texts: How do I find the maximum "discharge C rating" of a battery?

texts:
I've been experimenting running my 3A LED strips off battery power and the results are disappointing. I'm only getting a few minutes (< 10) out of a YSD-168 1800mAh lithium ion. How can I find the "C rating" of this battery? Is it something mainly dependent on battery chemistry (as this Dan's Data article I just remembered implies, search for "[space]C[space]" on the page) or something mainly dependent on manufacturing quality/technique? Macho RC battery packs always quote C-ratings, other battery types not so much. And it's difficult to google.

Also, what are typical maximum "discharge C ratings" of AA and AAA NiMH batteries?


texts:
I look at different cpu datasheets and a question keep coming back.

On a SoC, and in the case of a PCB design, if I want the maximum throughput between a dumb wifi/BLE chip and my processor (cortex A53), should I look for CPU support of Ethernet MAC (which it has) or is there something else to look at?

What if I want the fastest throughput for both Ethernet (1Gbit/s) and Wifi/BLE on that same SoC?

Thanks


texts: Uab marking of voltage difference betwen two nodes?

texts:
If I say \$U_{AB}\$, point \$A\$ will be point on higher potential, right?
Because \$U_{AB}=U_A-U_B\$?


texts: Question: How is this possible to get 1:1000 electric potential scale while primary/secondary loop scale is only about 1:100?


texts: What burden resistor value to use for current transformer?

texts:
I'm building a current measuring circuit. The circuit im using is seen below,

How do I choose the burden resistor for the CT ?

If say im measuring 8A max, then with a 1:1000 CT, thats 8 mA on the secondary. If I want the voltage to be 3.5 V full scale, then R = V/I = 3.5/8mA = 438 ohms ?


texts: PWM charging of inductor and expected current profile

texts:
This question largely covers the question I have, however the answer is unsatisfying, making the current output a function of an otherwise undescribed 'current control loop'.
I see by studying my own PWM controlled motor a similar phenomenon - a high-frequency PWM switching on all phases, where the current variation is on a much lower frequency and much nearer to an ideal current profile for the magnetic fields passing coils etc.
The linked question draws the distinction between going open-circuit and being always linked to one of the power lines either positive or neutral. As I write this question the answer begins to crystallise, so now I ask if my understanding is correct:

simulate this circuit – Schematic created using CircuitLab
In the pictured circuit, SW1 is in one of two positions:

Attached to the positive terminal, increasing the current in the inductor
Attached to the ground terminal, creating a circuit for the developed current to exist

It would be clear in this case that switching time is critical, as without some kind of buffer, the switching IC would have to accommodate the 'spark' and loss of energy the linked answer refers to. Further, any ambiguity in switching could feasibly see the battery terminals being shorted, wasting energy or damaging switching equipment. Is this simply handled with precise timing or are the switching ICs handling this in a much more graceful or intelligent way? At very least a well positioned capacitor might accommodate the current flow while the switch state is ambiguous.
I think if the proposed mode of operation is correct, that being connected to the battery ground is actually irrelevant, and that closing the inductor's own circuit is the critical factor. Is this an accurate statement?
Finally then, a circuit is sensing the developed current in the inductor, and making high-speed adjustments to the PWM output to keep current to that prescribed by the controller. Where in the control circuit would this current measurement take place and in practice what electronic device is making that measurement? (Example part numbers would be of interest)
Ultimately, I see a high-frequency voltage applied to the terminals, but no equivalent high-frequency current being absorbed by the motor phases. There appear to be good physical reasons why the current does not follow the somewhat violent voltage variations, and I would like to confirm here that the observed current vs voltage profile is as expected and I should not be looking for errors or issues in my sensing equipment.


texts:
I've got a board with two Altera CPLDs on it with a bit of a programming problem. Programming it via JTAG fails. If I do a JTAG address check
The JTAG lines run through the first board, through a flex and a few emerge on the other board underneath some other components. The rest seem to emerge under the CPLDs, which are on top of each other, or back to back for want of a better way of explaining it.
I don't know whether JTAG lines run parallel all the way, nor do I know what order the tracks are in inside the board - hopefully TDO is away from TCK... The board has at least 4 layers from what I can tell.
When I go to program the device, I can run the "Detect JTAG chain info" utility in MAX+plus II. It returns a message saying "JTAG chain information confirmed by hardware check", which is good.
Then, I can run a blank check, which fails.
If I disconnect TDO at the JTAG header and run a piece of wire to the JTAG pins on one of the CPLDs, it works. The data looks mostly fine on the oscilloscope with pretty sharp edges and minimal ringing. However, I get some spurious oscillations at certain points when I probe it:

The traces are as follows:
Yellow: TDO
Cyan: TCK
Magenta: TMS
Green: TDI
You will notice that TCK never quite makes it to rail occasionally... When it does, it is very sinusoidal and not at all square.
TDO only oscillates when TDI is high, but not every time TDI is high.
TCK seems to oscillate when TMS rises with TCK or when TDI rises with TCK.
I'm using a Bitblaster and have fitted a 1k resistor between TCK and ground and the remaining three lines have a 1k resistor to Vcc.
The scope screenshots were taken with TDO routed through a piece of wire straight to the CPLD. I've tried doing this with TCK and the waveforms still have this noise on them. If I try doing the blank check again without changing anything, the noisy bits move around.
Does anyone have any ideas as to why TCK seems to not make it up to rail, or why TCK and TDO seem to oscillate?
Thanks in advance.


texts: Caculating baud rate of Ethernet per wire

texts:
I'm trying to find the answer to what should be a simple question. How do I calculate the physical rate bits are transmitted on an individual Ethernet wire?

I am interested specifically in 100 Mbps and 1,000 Mbps links. These Ethernet links use 8 wires as 4 separate twisted pairs and each pair therefore transmits 25 Mbps. A bit of reading (heh) tells me  I am actually interested in the baud rate in which case I need to know the efficiency of the physical encoding schemes used for both of these links. I was also unsure if the quoted bit rates for Ethernet include overhead.

At this point I dived into the 802.3 standards on Ethernet which quite frankly for my purposes contain vastly too much information. I'm sure this is of interest to many people here but I found no instance of it posted before.


texts: Using Xilinx ISE tools, "does not have a port named" error

texts:
I'm a verilog Beginner.

I created a design using straight-up Verilog then tested it using the ISE design tools.  Works great.

I would like to synthesize this to see the resources that will be consumed but to do so seems to require a schematic file.  So I created a symbol for the Verilog cicruit and then created a new schematic, plopping my symbol onto the schematic and attaching some I/O markers.

When I tried to compile the schematic (AKA 'Implement the Design'), I got errors on every I/O. Here's an example:

  ERROR:HDLCompilers:91 - "mm.vf" line 35 Module 'method2_MUSER_mm' does
  not have a port named 'LL1'

The other errors are identical except the line number and port name changes.

My Verilog symbol is indeed called 'method2'.  The schematic has a I/O definition for LL1.  mm.vf is a file being generated by ISE.

I have no idea what it is looking for or how to fix it.


texts: What exactly is a "Bill of Materials" (BoM)?

texts:
My understanding of a BoM is that it's essentially a list of the various components required for an electronic product or module. Does this mean it could be as simple as a spreadsheet?

Are there any formal standards/templates for BoM's citing required/mandatory fields/data that it must contain? Any good samples/templates that can be referenced?


texts: ultra low noise reference and supply voltage with multiple ldo's in parallel

texts:
I need a very low noise power supply and ADC reference voltage for an 24 bit ADC measurement (I need noise level less than 5 uV peak to peak on both power supply and the ADC reference voltage. Supply current can be around 100mA)

I would like the ask the method mentioned in this link

Shortly it says adding 3 LDO output with an op-amp then dividing by 3, it reduces the effective noise on the final output. Will it work in your opinion?

What other methods do you advice?


texts: I made a diy guitar amplifier with two seperate amplifiers. When potentiometer is raised something strange and annoying begins - various whispers, noises and reacts really strange.  HOWEVER this never happens when any input device is connected.  I don't intend to search for the problem in the schematic as it is really quite messy between the cables and if something would go wrong I would be in trouble to find it.  So - how to 'simulate' a device input?  Of course the main input connection must function as it is.  Any suggestions will be helpful :)


texts: Simulating charge-discharge of a capacitor in TINKERCAD

texts:
I have been using TINKERCAD circuits for a while now, and I have been able to simulate almost every basic thing in circuits. But when it comes to simulating the charging and discharging times of a capacitor with the oscilloscope, then I can not show the charge-discharge phases... Any help here?
Is it true TINKERCAD is not good simulating capacitors?
Thanks


texts:
I understand the concept of a multiplexer and I can understand how n-1 multiplexers function. Your just sending a select signal to tell the multiplexer which of the inputs at the input pins to let through on the other side.

But what does an 8-4 multiplexer work? I'm specifically talking about the 74LS257. I tried looking at the datasheets, but I still don't get it.


texts: Is there any specific reasoning why C13/C14 power cord is used in almost all UPS devices as output?

texts:
Just bought another UPS for office and making wiring for it - cutting of standard plugs and installing C13 on extension cords.

Logical question arose - Why there are C14 on UPS output? Is there any reason for it?

Edit:

Reason for cutting power cords is simple - on each desk there are several things that need to be UPSed - PC, VoIP phone and basic desktop network switch. Later two use negligible amount of power and use standard power supplies, that cannot be plugged into UPS C14 socket. Besides it is easier to manage 4 cables for 4 desks instead of 12.


texts: Analog filter resistors and capacitor tradeoffs

texts:
I am designing a filter to obtain a dc reference from a signal, and I am thinking about using the schematic below for a cutting frequency of 1 Hz:

simulate this circuit – Schematic created using CircuitLab

The question is: how much can I increase R1 and C1 to lower the cutoff frequency?
Theoretically I could put there a resistance of 1 MΩ, but what are the drawbacks  (apart from the settling time) in increasing R1 (or C1) indefinitely?


texts: Is Power consumed by a motor under various load conditions constant?

texts:
Does a motor (dc /Induction/Synchronous ) consumes more power when operating at higher load than when operating at some lower load? Or power consumption remains constant/same in both cases?

What I think is that, Power drawn by motor should increase as we increase the load on motor.

But, someone told me that Power drawn remains constant.For example a 10 kW motor will always consume 10 kW irrespective of load on it.He said power consumed is P=3 VIpf (pf=power factor) for a 3 phase induction motor.As load increases current I increases but Power consumption remains constant as V ,pf change to compensate the increase in I in order to make power remain constant.

Please explain this.


texts: Can I start a new uart1 interrupt function inside a previous uart1 interrupt complete callback function?

texts:
I am using STM32F46ZG NUCLEO discovery board. My code is like:

int main(){
  HAL_UART_Transmit_IT(&huart1, buff, 5);

  while(1)
  {
    do something;
  }
}

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart){
  HAL_UART_Transmit_IT(&huart1, buff, 5);
}

My code has no RTOS, and I want to continuously transmit the 5 bytes. Once the previous interrupt transmit finishes, I want to transmit 5 bytes right away. So can I just call HAL_UART_Transmit_IT() in its own call back function?


texts: Measure power supply ripple with Rigol DS1052E

texts:
I recently received (as a birthday gift) a Rigol DS1052E oscilloscope. I read about oscilloscopes but I never really used one.

So my question is:

How can I measure the ripple voltage of a floating linear power supply, using this oscilloscope?

Can this be done with this oscilloscope (or the common mode noise will be too high, since the ground clip of the probe is tied to earth)? To get a fairly accurate reading would I need differential probes? Or can I use the two channels of the scope and add them together?


texts: Why do RCDs / GFCIs sense differentially rather than directly?

texts:
As far as I know, all RCDs / GFCIs sense leakage current by differential measurement between active and neutral with a current transformer. Both the active and neutral wires will pass through the transformer.

I have tried without success to find references on why we cannot simply pass the earth wire through the current transformer instead. Is this because some other kind of leakage or noise can occur on this wire that does not represent a fault condition?


texts: Unusual behaviour between two seperate electrical circuits in a race-car

texts:
simulate this circuit – Schematic created using CircuitLab

I have designed and created two systems that are currently present in a small race-car.

The first one is a circuit to control the fans of the car. The topology of the system is the following:
Battery -> Master switch ->Fuse box -> Relay -> 3-way switch
When using the switch, the first mode is to let the ECU (DTA s80) control the fans and the other is to turn the fans on constantly (through the relay).

The second circuit is the electro-pneumatic system that controls the two double 3/2 pneumatic valves responsible for the gear changes. There are two parts in this system. First there is there is the pneumatic part. I am using two valves (one for upshift/downshift and one for the clutch). These valves are controlled by the second part of the system which is the electrical. They are connected via individual cables to a PCB that has as an input two buttons coming from paddles from the steering wheel.The principal of operation is that both pads to whom the cables are connected have always +12V and when an input is detected, the micro-controller (STM32F103) outputs a signal to an analog circuit that grounds one of two pads so that the valve can "see" 12V. Between the fuse box and the PCB there is an on-off switch.

Now there comes a problem. Both circuits work fine except one critical moment. When I have the switch for the PCB to the on position and the 3-way one is either on mode 1 or 2 and I turn the fans off, the upshift valve fires to the piston.
Note: These two system are not crossing each other in no point (in fact there are on separate sides of the vehicle).

So far I have disconnected the steering wheel (still problematic) and I have external harness in order to see if there is a wire cut somewhere (still problematic) as well as disconnecting some or all the fans to not have any power draw from them (guess what, the problem is still there).

Does anyone have any idea why there is such a weird behavior ?


texts: I am trying to learn the space vector modulation but I am wondering how is the bias voltage in a 3-phase system regarded by the space vector?


texts: Does an IC package type have same dimensions regardless of who manufactures it?

texts:
There are numerous IC package types, popular ones being DIP, QFP, SOIC e.t.c and they have variations depending on how many pins they have

I am designing my Eagle library and have a question. Is it always safe that e.g I need a SOIC8 package that I can copy the package from any other library containing SOIC8 or is it possible that a SOIC8 chip from one manufacturer shall be slightly different from SOIC8 from another manufacturer making the library parts incomptible?


texts: How to make power supply to 434MHz receiver module more stable on RC car?

texts:
Following the recommendations I got on my last question about troubleshooting communications in my RC car, I probed the +5V power pin of my RF 434MHz receiver module with my oscilloscope. Below is a snapshot of it.

The periods marked in red (1 & 2) are the exact moments the receiver lost connection with the transmitter. Period 1 happen right after I applied full throttle (when the voltage raised) and then let it come to a full stop. Right after that, the voltage drops and the receiver output pin goes silent (LOW) during half second. On period 2, the car is sitting still and the voltage drops spontaneously below 5V and the receiver looses connection again.

So, it's clear to me that the receiver power supply is noisy. It's varying around 100mV when the car is stopped and shows up to 200mV pp. The receiver doesn't seem to like when the voltage drops below 5.0V.

My question is: how can I make the power supply more stable for the receiver module?

I can think of two solutions:

Add a filter to the receiver +5V pin. If so, what filter circuit should I use?
Add a buck/boost voltage regulator to feed the receiver. Would this remove the ripple on the supply?


texts: Suggestions for moldable ferromagnetic material?

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I'm trying to build a sort of three-axis stepper motor that consists of a sphere with a permanent bar magnet embedded in it surrounded by a cube (slightly smaller than the sphere, so that the sides of the sphere protrude) of ferromagnetic material. On each pair of opposite sides to the cube is a coil of wire, surrounding the hole in the cube through which the sphere protrudes.

By forcing current through a combination of the wire loops, the sphere can be magnetically induced to align itself along any axis. I've tried to build a prototype without using the ferromagnetic cube, but the field from loops of wire alone is too small to easily and safely cause the sphere to rotate.

My first few attempts have been to make a mold of the proper shape and fill it with iron filings, then pour some liquid that can dry or otherwise cure to a fixative (preferably non-conductive so eddy currents aren't a problem) to hold the filings in place- it is then easy to laminate the surfaces of the material so that corrosion of the iron, if not induced by the fixative itself, is not an issue. However, the only material I have on hand to make the mold out of is PLA plastic, which has a low tolerance for heat. I've tried a few different varieties of wax, but all that I've been able to lay hands on melt at too high a temperature for the PLA to stand or else are too cohesive and don't seep in between the iron filings, and I've had similar problems with various glues.

Can anyone suggest either a possible fixative or an alternative moldable ferromagnetic material to use?


texts: Why doesn't ua741cn operate correctly with a single supply?

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I'm learning OpAmp and i wanted to amplify .5v dc voltage to 5v dc output so i decided to use opAmp in the non-inverting configuration with a gain of 10. So I connected it as shown :

I set the potentiometer output voltage at .5v but the OpAmp's output was at the saturation level (about 11.5v). So i thought it might be the single supply i'm using and I used another OpAmp to split the 12v source into +6,-6 and ground and it worked well.

My question is why does it need dual supply to work proberly even i don't need any negative output voltages at the output?

My knowledge is that i can't have negative swings at the output if it's connected to a single supply (and that's fair) and this is my case, then why do I need a dual supply?


texts: Inductor Design - How do I know what value of Bmax and Current Density to choose?

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In order to decide what type of core I need, I need to calculate the Area Product Ap which is given as:

$$A_p \simeq \frac{LI^2}{JK_uB_{max}} $$

Where I is the current, L is the inductance, J is the current density, Ku is window utilization and Bmax is the max flux.

Now, given that it falls to me to decide what values of Bmax and J to pick from, are there certain rules of thumb that could help?
Thanks!


texts: Running high powered/current LEDs with high frequency

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firstly i would want to thank all who are willing to help me in this problem that i am facing.

So to begin, i am a high school student doing a final year project. Basically i have to create a circuit where by a 1000Hz frequency is an input that i have to alternate it so that my output will be toggling with half of the input frequency.
Therefore i am using a single J-K Flip Flop which has a Q & Q(bar) output. That i do not have a problem....

However the problem comes in here. from the 2 outputs of my J-K Flip Flop, i have to use each output to power up 20 LEDs in series, which has to be 1.7V each LED and 700mA, making it 34V with 700mA.

But the output of a J-K Flip Flop does not produce enough voltage and current.

i have tried using a BuckPuck after the output, and realise the rise and fall time is too slow for the high frequency.

i found out that a NPN Transistir ( BD137 ) has a very fast Rise and Fall time, however after configuring the circuit, the output measure was 34v But only 200mA....

please help me to get a 34V and 700mA, thank you.


texts: Loading question when dealing with 50 ohm impedance matching

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Above is an example of 50 ohm impedance matching when using a pulse generator. As you see, adding a small shunt resistor Rs here for a very big load resistor adjust the equivalent resistor around 50 Ohm, hence the impedance is matched.

My question is as follows:

I have a function generator and sometimes it is used to output sharp pulses with 10V amplitude.

In that case imagine the generator output is coupled to a load with a quite high resistor like 1GigaOhm. For impedance matching I can then set the Rs as 50 ohm. So far so good.

But now Rs will see around 10V/50Ohm = 200mA for a 99% duty cycle pulse.
This corresponds 0.2*0.2*50 = 2 Watt power dissipation.

Wouldn't a usual 50ohm resistor burn out in this case?

Moreover, how can one achieve impedance matching in this case?