texts: Speed limiter - turn off a motor if a fixed speed limit is exceeded

texts:
I want the cheapest, most basic method of turning off the motor while an electronically assisted vehicle is moving at over a certain fixed speed.

I don't need to measure the speed other than it being 'slower or faster' than a fixed rate. As the motor runs via gears to the wheels, I need something linked to RPM of the wheel.

For the sake of wiring I am thinking about a magnet on the wheel spokes and a sensor on the frame - and a hall switch linked to resetting some kind of countdown timer - while the timer is at zero, the switch stays open for a fixed period (enough time for an other revolution and the timer to hit zero again), if the timer doesn't get to zero in a fixed period then the wheel must be doing a revolution in less than the timer value, so the sensor switches off the power until the time does start getting back to zero (the wheel is now moving more slowly).

Is there a better way? If not, what sort of circuit should I be looking at for my timers?

Thanks!


texts: Given a microstrip line with the following parameters, the two parallel stubs are shorted. I'm not sure how to find the ABCD Matrix from port 1 to port 2.


texts:
I'm having trouble with a BJT question. How can we do ac analysis of this circuit?

My attempted solution is this:


texts: Input protection for instrumentation amplifier

texts:
There were a few concepts mentioned in the Input Protection Basics from A Designer's Guide to Instrumentation Amplifiers, page 5-5 that I don't quite understand:

Why direct transient to power supply with diode?
The internal diodes (D1-D4) are there to raise the DC overload and to protect the input of Q1 or Q2 from transient (or ESD). But wouldn't a positive (or negative) transient direct a large current to \$ +V_S \$ (or \$ -V_S \$) and damage the power supply? Shouldn't they have decoupling capacitors to direct these transients to ground instead of going through \$ +V_S \$ or \$ -V_S \$?

Do the internal input resistors reduce the input impedance?
The +IN and -IN inputs to an IA should see a very large input impedance in the \$ M\Omega \$ range (i.e. the non-inverting input of an op-amp buffer). But the input circuitry implies each input sees an impedance of \$ 400\Omega + r_\pi\$. Even at 6mA max input current, \$ r_\pi = {V_T \over I_B} = {0.026V \over 6mA} = 4.33\Omega\$. There are no resistor on either emitter side to get multiplied by \$ (\beta +1) \$. Total input impedance would just be \$ 404.33 *2 = 808.66 \Omega \$!
I'm confused ... IA should have high \$ M\Omega \$ input impedance, but the input circuitry indicates a mere \$ 800\Omega \$ input resistance. (I'm not sure if it has to do with Q1 and Q2 being biased by constant current source at the collector, and that somehow fixes the current into the base at a constant value? If so, the 400\$ \Omega \$ would be pointless...)

DC Overload calculation
If \$ 6mA * 400\Omega \$ raise the voltage by 2.4V, then shouldn't a 1k\$ \Omega \$ raise the voltage by 6V? But the book states 22.5V. I'm not sure if that's a typo or if I've mistaken something here...


texts: VHDL 4-bit shift register "can't resolve multiple constant drivers"

texts:
I'm trying to code the following in VHDL using a behavioural style. The system is a 4-bit right shift register. Re-setting the register should give it an initial seed value of “1010” and clearing the register should force the Q3 to Q0 to all zeros. All the Q outputs need to go an output port as well and the s_out is the out of the shift register. The shift register must have synchronous set and reset functionality.

I set about coding the register like this:

library ieee;

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

entity question1 is

port(
    -- inputs should be called s_in, clr_bar, set_bar, clk
    s_in,clr_bar,set_bar,clk: in std_logic;
    -- outputs should be called s_out and a vector q_out
    s_out: out std_logic;
    q_out: out std_logic_vector(3 downto 0));

end question1;

architecture behaviour of question1 is

    -- declare a signal q that is a standard logic vector
    -- implement the sequential logic in a process and using an if statement
    -- the setting and clearing/re-setting of the regiter should synchronous
    -- the register should shift right with the input to shift regiter as s_in
    -- assign the shift regiter output to s_out and the Q output the output vector q_out

    signal q: std_logic_vector(3 downto 0);
    begin
        shift_process: process(clk) is
        begin
            if(rising_edge(clk)) then
             if clr_bar = '0' then
                q_out <= "0000";
             elsif set_bar = '1' then
                q <= "1010";
             else
                q(0) <= q(1);
                q(1) <= q(2);
                q(2) <= q(3);
                q(3) <= s_in;
             end if;
           end if;

        end process shift_process;

        q_out <= q;
        s_out <= q(0);
end behaviour;

I notice that when placing the q_out <= q outside the process reults in an error

  Can't resolve multiple constant drivers for net "q_out[x]"

In some others posts where people had the same problem they had multiple processes and were trying to assign a signal from both processes. I only have one process here. I'd like to know what I am doing wrong and in short where I need to assign the process signal q to the output q_out.


texts:
I have a problem with my amplifier circuit (LA4597).

I tested it (12V). It turns on and the speakers and fine and silent.

But when I try to add an audio source (RCA) within the circuit, the speakers begin buzzing. And when music is played, the output comes out very loud and distorted and is being mixed with the buzz.

I followed the diagram on the datasheet to the letter. I wanted this to play music from a phone or a PC. What am I missing?


texts: Why does the multimeter need to be set to AC voltage to measure the voltage on secondary winding when driven by a square wave on the primary?

texts: I have a transformer being driven by a square wave at about 9 kHz with a 10/11 duty cycle. In order to measure the voltage on the secondary I have to set my meter to AC. Why is it so? The primary voltage is not AC so why is the secondary AC? and is it a sinusoidal wave? or alternating square wave? My theory is that it has to do with the way to magnetic field on the primary is constantly increasing and decreasing which would induce an alternating current on the secondary.


texts: Hot TL783 - is the diode shorting the regulator?

texts:
So.
I'm assembling a power supply kit from one of the DIY kit retailers. It works well, but the TL783 regulator providing 48V gets really hot with no load attached.
I think that it might be the diode which is for some reason connected across the Vi and Vo pins of TL783. I cannot find it on any schematic in the application note and it looks like it shorts the in and out (Vi to ground should be 15V but now I measure it at about 100V).
Is that it?


texts: Best method to determine current in ESR meter

texts:
I've recently found the need for a ESR meter(My daughter and her boyfriend brought me 8 broken LED/LCD TVs and 6 have power problems).

I also decided to go all out and build a full blown ESR meter.  The foundation for the meter is going to be the STM32F373 which has 3 16bit Sigma Delta ADC which are capable of simultaneous differential conversion.  It also has DSP capabilities so I was going to use a DFT to determine impedance and go from there.

So I'll measure voltage across a test resistor, across the Cap under test and current.  I want to use both variable voltage and frequency.  I thought to use .2V to 1V for voltage and 100Hz to 25Khz for frequency.  The test signal will be generated using one of the internal DACs filtered to a sine wave and buffered(for voltage and current control, including constant current(Edit to make it obvious)).  I think I'll just output all this info via serial port and use a program to display and control.  I can always add a interface later.

Sorry for all the leading information but I wanted make sure the question could be answered.  With my brain though I've most likely forgotten something.

My question is under these circumstances which method of measuring current is better, using a shunt resistor or a current transformer.   I've looked at a large assortment of various types of meters and just can't make up my mind.

I have a couple of IN Amps, a large assortment of op-amps and passive components available to me.


texts: How can this Parallel LC circuit act as a filter?

texts:
How can the network that is shown in the image in any way alter the voltage being supplied to the output?
i.e no matter what the response of the LC system, the input voltage is directly transferred to the output load resistance R since it is connected in parallel to the input. How can the network then be a band-pass filter ? I've referred numerous articles on analysis of parallel RLC networks but none have answered this simple question.Please help!


texts: Android to arduino- best board option for wireless

texts:
I'm a novice arduino hacker. I need to connect a hacked Android to an arduino wirelessly but unclear as to which option is best. I've read about the Mega ADK and it is my understanding that a regular board (uno?) can be used with a wireless bluetooth dongle.

What is the best and easiest way to connect to an arduino wirelessly?


texts:
I am using Altium v20.2.4 and i have a Multi-board Assembly project from Altium v18.
I am trying to open this document (*.MbaDoc). As it is for an older Altium version i get the info to convert it for the new 3D viewer under Design -> Import.

After clicking OK i have a grey editor. Then i go in the nav bar to Design and there is no Import, just "Import Changes from *.PrjMbd".

Can anyone further assist me how and where i can convert the old Multi-board Assembly project?
Am i missing something in the documentation?


texts: Is this circuit design for multi-function button box good?

texts:
I'm building a button box with many momentary push buttons to control several raspberry pi zeros via gpio input. I'd like to be able to have each button have two functions by using a selection button. The schematic shows the selection button at the top and two function buttons below it but the final product will have at least 10 function buttons. A high 3.3v input would be connected to each transistor to the left and right of each function button. When the selection button gate is open the function button completes the path to the +5v, activating the NPN transistor on the left and pulling that input to ground. When the selection button gate is closed and the function button is pressed, the shortest path is to ground, so the NPN deactivates and the PNP activates, pulling the other input to ground.
I have built this on a breadboard and it seems to work mostly as expected. Tested it with a few different pieces of hardware, including one with 5v logic and everything seemed fine. I'm here wondering if I'm missing anything important or if there are any issues with this design that I've missed.
Edit: changed schematic image for clarity.. again


texts: Share battery pack with Arduino and DC motors

texts: I used 6 rechargeable AA batteries (total 7.2V) to power my Arduino (UNO R3) Car's two DC Motors (using L293D IC as motor driver). I used separate 9V battery to power Arduino itself. But I want to share same 6 battery pack to power my Arduino via barrel jack. Please suggest me how can I do this? What precautions should I take? Like decoupling capacitors or any other?


texts: Multiple Big Stepper Motors on Raspberry Pi

texts:
I am fairly new to the world of stepper motors, drivers and RPis, so I might have some potentially naive questions.
Firstly, I am using two NEMA 34 stepper motors and planning to connect them with DM860T drivers. However, I am unsure if I am able to connect these two, big drivers to a single RPi, or will I need two Rpis. Is this possible? Can a RPi work with this setup? Are the drivers too high voltage for the RPis?
I have seen many tutorials for small, single motors, but little resources for big stepper motors.
Any other assistance or advice will be greatly appreciated.
Thank you most kindly for your help.


texts:
I probably need to use an SSR for a design. I have never used SSRs, I just know things that have read on data sheets and the internet. I am planning on using the following spice circuit for a model...

Instead of using an Roff resistance i have 1uA of leakage going in which ever direction has the lowest potential. Also I have 5mA input current required to turn on the switch.

Do you think this a good approximation of an SSR?


texts: Why doesn't my CMOS inverter drive its output to ground?

texts:
I have created an inverter using cmos logic (see image)

However, when I simulate the circuit model, even without a load I get an output voltage that remains fairly high rather than going low (see image).

Any insight that anyone can provide with regards to my issue will be very much appreciated.


texts: Transistors are hard to wrap my head around with laws

texts:
When I was younger I played with micro controllers and moved on over to programming. I decided to play around with circuits again, and a few things are not clicking.

Specifically, I am not quite sure how exactly transistors effect circuits in regards to voltage and current. When I try to figure it out, I think of it through the lens of how a resistor effects the nature of the circuit, is this a faulty perspective?

For example, when I use a NPN transistor as a switch for another circuit with a LED. The base of this transistor is switched from a separate power source than that of the LED. The LED is from a 9V source, and the transistors base is from a 1V power source. The transistor has a 1k Ohm resistor, however it appears I do not need any resistance for the LED, despite it coming from a 9V source? The LED has a max voltage of 2V and a max current of 20mA.

I am unsure how the LED is not blowing, and I am also unsure how the current is only 18.6 mA.

Here is a schematic of the scenario in which I am describing:

Perhaps I have missed something basic,, which makes this hard to understand. If that is the case I would appreciate being pointed in the right direction. Since I am relatively new, it is hard to think of what search terms to use in order to get accurate results.

Thank you.

Edit: Wow, all very good answers. I wish I could mark them all correct. I'll mark the simplest answer because it helped with the initial grasp, but to anyone stumbling upon this question, the other answers help give you a deeper direction.


texts: How to correctly wire LEDs and minifans into my greenhouse cabinet

texts:
I am building a small 4-shelf vertical indoor greenhouse. Each shelf has a 3-port USB hub-splitter which powers 1 USB minifan (5V, 1A) and 2 strips of 50cm USB LED lights (5V, 1.8A (30 * 0.06)). Then each shelf is plugged into a 4-port USB splitter which is powered by a 5V, 1A charger.
Basically, when everything is switched-on the LEDs produce almost no light. My question would be do I need a charger with more amps? In this case 11.2A? Can someone maybe help me to understand this issue?


texts: Driver load order for multiple pcie functions

texts:
I've a pcie device with 4 functions and i want to load the same driver on all 4 functions. However, i need a specific load order such that f0 driver should be loaded first, followed by f1, f2 and f3. is there a way to control the load order? Or do i get this naturally in windows 10 kernel?
Thanks!


texts:
The task is to design a amplifier for maximum gain, which means conjugate matching. The S-parameters at different frequencies are as follows

Now for 1GHz $$K<1 \text{ and } \left|\Delta\right|<1$$ so the amplifier is not unconditionally stable. Here is a plot of the Load and Source stability circles

Using the simultaneous match equations, my value for \$Γ_L = 1∠124.39^\circ\$. Now this is obviously inside the Load stability circle. My question is then, how is the amplifier stable? The solution gives the answer as that the amplifier is stable.


texts: Need to check ON or OFF state of a wire using non-invasive method

texts:
We have a GSM SMS alert system (mod bus) that needs a signal that a wire (any wire from 3-phase) has current (maximum 15 amperes in ON state) or not, so we can know if the system is  ON or OFF.
There are non-invasive CT products but need guidance on how to use it so that we get signal +5V or 0V to differentiate ON or OFF.
problem statement : we want to know if the appliance connected to the main power is tripped or not remotely (SMS alert device), for this purpose the current in the live wire drops to ~0amps when the appliance is tripped, and when its working the current is ~15 amps, we need a non-invasive clamp on one of the 3-wires, not all 3 as it would give zero reading, so that make a simple circuit to get input to SMS device (5V-on, 0V-off) signal

simulate this circuit – Schematic created using CircuitLab


texts: BJT: Equation of Vce for Saturation Region

texts:
In Sedra and Smith: Microelectronics Circuits (6E), it is mentioned, on page 185:

  Recalling that the CBJ is much larger than the EBJ, the forward-voltage drop \$v_{BC}\$ will be smaller than \$v_{BE}\$ resulting in a collector-emitter voltage, \$v_{CE}\$, of 0.1 V to 0.3 V.

Why does a difference in junction area causes a change in the forward-voltage drop? A similar question was asked on the site, however, it did not help.

So, I tried using Ebers-Moll model and that is where I am actually getting stuck. So, my question is this:

How should I apply Ebers-Moll method for a transistor working in a saturation region, to get the equation for \$V_{ce}\$?

So far, I know that there are three major Ebers-Moll models, here. I also read that the \$I_{s}\$ is a property of the emitter-base junction.
Additionally, \$i_{c} \leq \beta i_{b}\$.

Thank you for your time. Please inform me if some additional information is needed.


texts: What does an NMOS transistor with the gate connected to the drain do?

texts:
I'm studying about PLAs and I came across this simple PLA design.
What is the purpose of the highlighted transistors?


texts: Determining The Parameters Of A Wheatstone Bridge

texts:
Good day,

I am trying to use a Wheatstone bridge to condition a thermistor. The arrangement i have is shown in below.

I need the following specifications.

10V output max from the bridge at maximum temperature (50 degrees celcius)
0V output max from the bridge at minimum temperature (0 degrees celcius)

I have determined the resistance of the thermistor at the minimum and maximum temperature to be as follows

At max temperature R = 174
At min temperature R = 1.1K

I know that for the wheatstone bridge to be balanced i need the following for my arrangement

R1/R3 = R2/Rt

So i have set R3 = 1.1K and Chose R1=R2=1500k (arbitrary value)

With this i do get 0V output at 0 degrees.

My problem is now, how do i ensure that the output voltage i get is 10V at 50 degree celcius, as i currently get 8.7V output with the source voltage set to 24V.

Any help would be appreciated, Thanks.


texts: Possible to use both CS1 and CS2 for SPI1 on Beaglebone?

texts:
I need to connect two SPI devices to Beaglebone. According to the documentation both SPI1_CS0 and SPI1_CS1 are available on the extension header:

SPI1_D0, SPI1_D1 and SPI1_SCLK are available on P9[29], P9[30] and P9[31].

SPI1_CS0 is available on P9[20] and P9[28].

SPI1_CS1 is available on P9[19] and P9[42].

I've traced these through the schematics and found they are connected to the following pins on the CPU (AM335x):

SPI1_D0 -> B13
SPI1_D1 -> D12
SPI1_SCLK -> A13
SPI1_CS0 -> C12 / D18
SPI1_CS1 -> C18 / D17

However, there seems to be no combination that enables both CS0 and CS1. I've tried to make a working pinmux using the TI pinmux tool, but no matter what combination I use for CS0 and CS1 i get "pin conflict" and error message that one or the other is not available in the IO-set.

Is there really no way to enable both CS0 and CS1 on the Beaglebone?

(I'm using Beaglebone Green Wireless, which should be compatible with Beaglebone Black)


texts:
I'm experimenting with PIC programming controlled by an Arduino Uno, and I'm using the PIC12F675. I actually got the PIC to enter programming/verify mode yesterday and was able to read out the device ID, but before that happened I actually burned off a PIC, but I'm not sure exactly what I did wrong.

The problem was related to the MCLR/VPP. In order to enter program/verify mode, this has to be driven to a high voltage (at least 3.5V higher than the power source) as part of a sequence of initialization events. So I connected the Arduino to a 12V power supply and used 5V to feed the Vdd on the PIC and the 12V to the MCLR (max is rated at 13.5V). At that point I thought that since the MCLR was the first signal to be driven high, I could simply tie it permanently to a high voltage source (12V). But after turning the board on, the PIC quickly became very hot and (as it turned out later) was burned out. The reason why I connected it directly without a resistor was that the programming specification (http://ww1.microchip.com/downloads/en/DeviceDoc/41191D.pdf
) said:

  In the PIC12F629/675/PIC16F630/676, the programming high voltage is
  internally generated. To activate the Programming mode, high voltage
  needs to be applied to the MCLR input. Since the MCLR is used for a
  level source, the MCLR does not draw any significant current.

In other words, the high voltage input is not used as an actual power supply, it is just a way of signaling you want to enter programming mode. So I read the above (especially the "the MCLR does not draw any significant current") in the way that the PIC's MCLR PIN would have a high internal impedance and would thus not draw any significant current, hence it should not be necessary to provide any resistors etc. Also there's no note in the datasheet saying how much current you are allowed to transfer through any of the PIN's. But clearly that's not how it actually worked. Also earlier in the experimentation I was working with smaller voltages (8.5V) where I also connected direclty, and this didn't cause it to heat up so it can't just be a plain short circuit since then 8.5V should burn it out too.

Another question along the same lines: When connecting the analog PIN's of the arduino to the GP0/GP1 PIN's on the PIC, is it necessary to use resistors? Again, when the GP0/GP1 on the PIC are in input mode they should have high impedance, so I don't see why I could simply connect it directly to the Arduino. Now in this particular case, the data PIN (GP0) actually changes between input/output at specific points during programming and the Arduino has to do the same, so I guess one needs to be careful about changing at the same time so they are not both in the output state simultaneously (since that doesn't have high impedance). But to be sure I added some small resistors (470R) to limit how bad things can go. But it would be nice to know if this is really necessary, since again the datasheet doesn't say how much current you can transfer through the PIN's.

(in the new circuit I made that actually works I have 15K ohm between the 12V and the MCLR and I also control the MCLR through a transistor so I can turn it on at the right point in the sequence)


texts: LCD driver board M.NT68676.2 issue: Screen compressed, fills only part of display

texts:
I am trying to build a portable Raspberry Pi/Retropie system with an LCD screen I got from my old laptop (the idea is to have a portable gaming console to be used in a car). To drive the screen, I am using a M.NT68676.2 monitor control board (datasheet) i got from ebay.

When I connect board and screen to my computer, the desktop shows up but the picture is compressed and fills only about three fourths of the screen horizontally from the left (the rest is black). Vertically, there is no compression and the lower end of the desktop falls outside the screen. When I access the on-screen menu provided by the board, it gives me the correct resolution I have set although that obviously isn't the case.

I have been googling for days now but found not even a description of the problem. The issue remains irrespective of machine used (Pi, two laptops), connection used (HDMI and VGA), operating system (Windows, Ubuntu) and all other settings I know of (e.g. framebuffer in Linux). Connections have been checked about a hundred times. I am therefore totally at a loss.

According to the sticker on the back, the LCD I am using is an LG/Philips LP154W01(TL)(AE) and the M.NT68676.2 has been flashed accordingly by the retailer (who suspects a fail in the LCD although from his mails I think he just doesn't know what to do).

Has anyone had similar experiences? Are there any ideas what could cause the issue? The only possible hint that I have found so far is that the screen board itself states "Desc: LP154W01-TLA8-E22" which to me seems to refer to a different model number than given on the back of the LCD itsef.


texts: Part number Molex 4 pin wire-to-board connector and 2 pin wire-to-board like Corsair CommanderPro

texts:
I'm having a really hard time finding the correct PN for a 4 pin header, used with PWM fans.

The header I'm looking for is a 4 pin one, similar to the Molex 47053-1000, but a right angle one.

I've already spent a couple of hours on Digikey and the Molex website, but I can't find this. I'm only finding a 4 pin connector that has a bigger plastic tab, that won't take the 4 pin PWM fan connectors.

Has anyone worked with this type of connector before that could provide me the PN?

I also wanted to find 2 pin thermistor connectors

Here is an image of the type of connectors:

It is in the opposite direction.


texts: Equipment for analyzing large DC distribution system

texts:
I'd like obtain the transfer function of a large DC power distribution system. My question is whether there's equipment (like vector network analyzers) designed to
assist with modeling these type of applications. Most equipment seems to be for analyzing power converter PCBs.
Here are some details about the system:

The system is a large telecom DC distribution system consisting of lead-acid batteries, rectifiers, buswork, and load equipment (essentially constant-power loads).
The load is approximately 250kW.
System voltage is 52V under normal conditions. The voltage falls to 48V during battery discharge.
The load is not in the same room as the rectifiers/batteries. The separation is about 200ft.
I'm most interested in the network impedance at relative low frequencies (<100Hz).


texts: What will happen if light is shown on IR LED (emitter) when it's in reverse bias condition?


texts: Why my low pass digital filter amplifies in the passband?

texts:
I'm trying to implement a 10th-order Butterworth Low Pass digital filter on my MCU.

To find the coefficients I used Matlab's Filter Design & Analisys Tool. So I create two little scripts: in the first of them I used the Filter Object created by the tool and it seems to works perfectly, but in the second one I tryed to implement the general code based to the Biquad Direct-Form-II using only the coefficients generated by the tool and, in this case, the filter works good except for a signal amplification of about 5E+7!

My code in matlab is the following:

input = AmplitudeF8.';

delayline_lp = [0,0,0,0,0,0,0,0,0,0];
coeff_lp = [-1.7582972612745587, 0.89109671836321969, 2, 1, -1.5932765493727838, 0.71361243648860972, 2, 1, -1.4754804435926461, 0.58691950806119031, 2, 1, -1.4002643388507841, 0.50602253348347193, 2, 1, -1.3637162169443289, 0.46671403035270148, 2, 1];

for k=1:length(output1)
    y = output1(k);

    for j=1:5 %the biquad sections (order 10 = num_sections = 5)
        w = y;
        for i=1:2
            w = w - (coeff_lp(((j - 1) * 4) + i) * delayline_lp(((j - 1) * 2) + i));
        end

        y = w;
        for i=1:2
            y = y + (coeff_lp(((j - 1) * 4) + i + 2) * delayline_lp(((j - 1) * 2) + i));
        end

        delayline_lp(j * 2) = delayline_lp((j * 2) - 1);
        delayline_lp((j * 2) - 1) = w;
    end

    output2(k) = y;
end

Consider that in the coeff_lp array there are a1,a2,b1,b2,.... since a0=b0=1 for every biquad section.

Why in this case the filtered signal is amplified by a 5E+7 factor? Where I'm wrong?


texts:
Schematics:

I'm working on improvement of my CCIR->OIRT downconverter based on LA1185 IC. Previously I've faced strange problem that on certain frequencies I'm getting just a loud silence and sometimes (depending on temperature changes, I think) it just doesn't work at all. I suspect that this can be related to the quartz crystals which I use - they are working on their 3rd harmonic. I've decided to change them to fundamental ones.
I discovered, however, that the most of the crystals from Mouser (22 MHz, 30 MHz and 36 MHz, for example) have load capacitance. If I understand this right this is the capacitance which I should match by adding two caps of that value in parallel to the both pins of my crystals (as I usually do with AVRs) to the ground so the crystal itself is designed for parallel use. However it's clearly seen from schematics that Y1-Y3 crystals are just in series between ground and OSC pin of LA1185.
There are few crystals on Mouser which are labeled as "Series" so I can't actually get full set of them. And I doubt if I can use crystals with Load Capacitance in such a way according to the schematics.
My questions are:

Can I just use any crystal of right frequency but with Load Capacitance without any modifications to the current schematics/PCB?
If no, is it possible to use them anyway but with, for example, adding some caps between crystal pins and ground (-5V in this schematics)?
If previous is true, what will be the proper way to add such a caps to my crystals?

Thank you!
EDIT 1 Regarding question 1, let's consider that Y1 crystal have stated Load Capacitance of 10 pF (I assume it's designed to be used in parallel), what is the proper way of connecting it?
Series:
Parallel with one cap:
Parallel with two caps:
I understand that frequency will vary a bit but as I said down in the comments I don't think that this change will matter a lot because even an error of a few kilohertz should be ok for downconverting the whole CCIR into OIRT (that's why I use three crystals selectable - just to be able to select necessary subrange). More interesting question is how it will impact on the stability? What are the potential pitfalls of using improper connection such as no oscillation at all, temperature dependence etc?
EDIT 2
I've found this useful AN. According to the chapter 5 I should select C1 and C2 in that way so their series combination will be close to the Load Capacitance: (C1 * C2) / (C1 + C2) = C_load. For AVRs it's around 11 pF (22 * 22 / (22 + 22)).


texts: Is it possible to do an FFT on the output of a 4 bit ADC?

texts: I made a simple 4 bit flash ADC on a breadboard, and I want to run an fft on the output. Is it possible to do an FFT on data that is only 4 bits in resolution.


texts:
I'm building a small board that uses the MMA8453Q Freescale Accelerometer.

The datasheet requires a 4.7μF decouple capacitor on the \$V_{dd}\$ pin. I only have 3.3μF or 6.8μF capacitors on hand. Could I use them instead? What's the risk of using a different value decoupling capacitor?


texts: Designing a circuit that calculates Hamming distance?

texts:
I came across this question and I couldn't find it in textbooks or the internet. Seems pretty unique.

I guess there would be some comparators and adders involved, but I have no clue where to start. I'd appreciate if someone could explain in very simple, newbie proof terms.


texts: How to achieve analog zero-drift sample and hold for hours?

texts:
This so-called "zero drift" opamp droops .001V/sec, at temp 85C with a 1 uF cap. If I'm reading the spec correctly, that's 3.6V/hour!

http://www.ti.com/lit/ds/symlink/lf398-n.pdf

Is there a method to store a low current V for up to about 5 hours with drift or droop within my desired resolution of approx 250 ppm, or equivalent 12 bits?

"Low current" meaning mA or uA scale.

The sample rate is between once per second and once per 5 hours.

Prefer to stay in analog domain, because I want to explore and expand my analog knowledge.

The solution should be practical, and use commonly-available components

Digital solutions are ok, but should be code-free, so it's accessible to non coders, and not require a computer to implement, so it's accessible to people who don't own a computer (such as the economically-disadvantaged teens i mentor).

Not asking for specific part numbers, just the basic method.

update:
The manufacturer confirmed that my estimate droop-per-hour is correct. According to the manufacturer, droop is largely influenced by the input bias current of the buffer amplifier and whatever leakage may occur through the switch - not just normal capacitor leakage.
https://e2e.ti.com/support/amplifiers/precision_amplifiers/f/14/p/641041/2365384#2365384


texts: I am reading through "Practical Electronics for Inventors" and I came upon a chapter about deenergizing inductor. I understand the concept that when you cut the current going into inductor, it will generate high voltage drop, since dI/dt goes to infinity. How come this is not an issue when the inductor "starts"? The voltage drop should be the same, right? Why this isn't an issue with capacitor? When we "turn" it on/off, there should be infinite current (minus internal resistance) according to laws. Shouldn't high current be a bigger problem than high voltage? What am I missing?


texts: Using impulse response to control the system

texts:
This post by Olin Lathrop is rather inspiring.

  The system response is the convolution of the control input with this
  impulse response, computed every control sample, which is every 500 ms
  in this example. To make control system out of this you work it
  backwards to determine the control input that results in the desired
  system output.

How is this done exactly - this "work it backwards to determine the control input"? I'm not expecting a full systems control course here, just a general description and some pointers to start looking for. Some pseudocode would be a bonus.


texts:
I am currently reading value from ADC and displaying on LCD screen. The ADC is supported by DMA. Now my system has 5 menus seen on LCD (Voltage, Current, Resistance, Settings). 3 of them should display ADC value with ~ 1fps.

What are the best practices to refresh the LCD frames?

Shall I implement a timer and refresh the whole LCD screen on every overflow?
Or should I just refresh that number?

Or shomehow else?

What are the best pracitces of building menus?


texts: What to choose hFE or beta from the plot of transistor's datasheet

texts:
Suppose I have this BC635 transistor, if I look at hFE then I'd say that the lowest value is 25 from that table in the Electrical Characteristics category, but if I look at the Figure 3. Base-Emitter Saturation Voltage from where I get the beta characteristic, on the right side of the plot beta is 10.

Now I only learned about the beta characteristic in school, not about hFE, but I read online that they are the same thing, although this is not true judging from the datasheet I linked.

The question is:
What should I use in my calculations for the base current if I want to use a transistor as a simple DC switch, beta from the plot or hFE?

What's more troubling is that some datasheets do not have those plots, what should I do there?


texts: I'm trying to build a smart frisbee for use in Ultimate. I'd like to be able to track the position of the frisbee in a playing field with pretty good accuracy (within ~2ft). GPS is a possibility, but I'm not sure if it is accurate enough. Are there any other technologies that would help, such as some system where I set up transmitters on the four corners of the field and place a receiver on a frisbee?


texts: Magnitude of a function with inductor and capacitor

texts:
I have a homework problem with the following circuit:

I have solved the transistor biasing part and then drawn the AC-circuit of it.
Then I need to find the transfer function.

These are the calculations I did:

This is the drawing which I drew by hand of what I think the transfer function will be:

I am not sure how we ended up getting infinite for the third case. Would really appreciate some help regarding this.

Similar problems like this I want to be able to solve in just some piece of paper.


texts: Why is DC offset from LO feedthrough less problematic in the second mixer stage of a dual conversion receiver?

texts:
A dual conversion receiver has two frequency translation stages. The first mixer translates from RF to IF; the second (IF) mixer translates from IF to baseband.

This architecture is supposed to help avoid the problem of DC offset, caused by LO leakage to the mixer input followed by self-mixing of the leakage down to baseband.

Direct conversion receivers, which have only one frequency translation stage, suffer from DC offset because the LO leakage energy is immediately translated to baseband. The dual conversion architecture takes care of the LO leakage from the first mixer by ensuring that it appears at an offset of IF from the signal of interest.

But the LO leakage of the IF mixer, if any, is translated directly to baseband when it self-mixes. Why isn't the LO leakage from the second (IF) mixer equally as problematic as the LO leakage in the single mixer of a direct conversion receiver?

I've read one answer in this book:

  DC offset due to self mixing is introduced when the IF LO signal leaks to the input of the IF mixer and then self mixes to produce a DC output in the analog baseband. This on-chip IF leakage is more deterministic than its direct conversion counterpart in which the LO can leak off-chip to the antenna and be amplified by the low noise amplifier (LNA) before self mixing occurs. Unlike a direct conversion receiver, RF LO self mixing in a dual conversion architecture creates a DC offset at IF and does not introduce any impairment in the analog baseband.

but it's not clear to me why the two mixers are different in this respect. Why does the first (or only) mixer suffer from off-chip leakage, but the second mixer does not?


texts: High Speed PWM Module on dsPIC33 not switching

texts:
I'm trying to get the High Speed PWM Module from a dsPIC33EP64GS502 to work. I previously got working the same module for a dsPIC33FJ16GS402 but I can't get this one to work. The PIC is running at 70 MIPS with internal oscillator, the PWM frequency is 300KHz with a 50% duty, this is my code:

// ACLK setup
ACLKCONbits.FRCSEL = 1;
ACLKCONbits.SELACLK = 1;
ACLKCONbits.APSTSCLR = 7;
ACLKCONbits.ENAPLL = 1;
while(ACLKCONbits.APLLCK != 1);

// PWM setup
PTCONbits.PTEN = 0;
PTCONbits.PTSIDL = 0;
PTCONbits.SEIEN = 0;
PTCONbits.EIPU = 0;
PTCONbits.SYNCPOL = 0;
PTCONbits.SYNCOEN = 0;
PTCONbits.SYNCEN = 0;
PTCON2bits.PCLKDIV = 0;

PWMH_TRIS = PWML_TRIS = 1;

PWMCON1bits.FLTIEN = 0;
PWMCON1bits.CLIEN = 1;
PWMCON1bits.TRGIEN = 0;
PWMCON1bits.ITB = 1;
PWMCON1bits.MDCS = 0;
PWMCON1bits.DTC = 0;
PWMCON1bits.CAM = 0;
PWMCON1bits.XPRES = 0;
PWMCON1bits.IUE = 0;

TRIG1 = 1568;
TRGCON1bits.DTM = 0;
TRGCON1bits.TRGSTRT = 0;
TRGCON1bits.TRGDIV = 5;

IOCON1bits.PENH = 0;
IOCON1bits.PENL = 0;
IOCON1bits.POLH = 0;
IOCON1bits.POLL = 0;
IOCON1bits.PMOD = 0;
IOCON1bits.SWAP = 0;
IOCON1bits.OSYNC = 0;

PHASE1 = 3136; // 300KHz
PDC1 = SDC1 = 1568; // 50%
DTR1 = 157;
ALTDTR1 = 157;

// Override
IOCON1bits.OVRDAT = 0;
IOCON2bits.OVRDAT = 0;
IOCON1bits.OVRENH = 1; IOCON1bits.OVRENL = 1;

PTCONbits.PTEN = 1;
IOCON1bits.OVRENH = 0; IOCON1bits.OVRENL = 0;

__delay_us(100);

IOCON1bits.PENH = 1;
IOCON1bits.PENL = 1;

I get absolutely nothing on PWM1H and PWM1L pins. I just don't know what else to change to make it work. This is intended to work in a synchronous buck converter so the signals are complementary.


texts:
I'm trying to design a feedbcak loop compensator and I'm following the instructions on power supply cookbook.

Book has calculations for DC gain like equations below:

in my situation Vin: 40V-60V and Vout:350V, Nsec/Npri:10 (full-bridge)

DC gain becomes 350V/40V: 8.75 and that means peak to peak output voltage of the error amplifier is: 45.7V

question is what is this peak to peak output voltage of the error amplifier? what do we use it for?

bonus question: I'm using sg3525 and I can't find the ramp voltage of it, is there a calculation for it? Here is the datasheet: https://www.st.com/resource/en/datasheet/sg3525.pdf

thank you.


texts:
Consider the following circuit:

It is required to calculate the small signal voltage gain (i.e \$\frac{v_o}{v_i}\$) based on \$R_s, R_c, I_c, V_A\$ and β.

So I draw the small signal model as below:

simulate this circuit – Schematic created using CircuitLab

So, for \$A_v\$ we have:

\$v_o = g_m v_{be} (r_o || R_c)\$

\$v_{be} = v_i \frac{rπ}{(rπ + Rs)}\$

so:

\$A_v = \frac{v_o}{v_i} = g_m \frac{r_π}{R_s + r_π} (r_o || R_c)\$

I think everything is okay so far! Am I right?

In the next part of question, I have been asked to find the value of \$I_c\$
which we have maximum \$A_v\$ for it. I have been stuck in this point.

Would you please give me some hints?


texts: Using a microcontroller ADC to measure a 4-20mA sensor

texts:
Question from a SW Engineer again.

I've got a device which is mains powered and outputs a 4-20mA current depending on the flow rate in a pipe. I'd like to measure that flow rate with a microcontroller.

On the face of it it's easy. My microcontroller is 3v3 so max current should produce max voltage of 3v3. So R = 3v3/20mA = 165 Ohm. If I pass the current through  165R and measure the voltage across the resistor it's all good.

My problem is I'm unsure if I can actually do that. The uC will measure a voltage relative to it's ground connection so I have to connect the uC Gnd to the negative side of the 165 ohm Resistor. Is that safe?

I was then looking at current mirror circuits but they all share a Gnd plane between the two sides of the mirror so it's no better then the simple 165R.

Is there a "correct" way to isolate this sensor or is it a case of just connecting the ground. My uC will be powered by a Mains - 12v DC power converter so maybe ground will be the same on both sides?


texts: Easy resource to learn solving counter problems?

texts:
Could anybody please point me some direction on where I can learn to solve simple counter problems like counting in a given sequence using a given flip-flop? For example:

  Create a counter counting in a sequence 3-1-4-7-2 and again from the
  beginning using the D-type flip-flops

I'm not asking for help in this particular problem - rather, it'd be great to know how to solve this class of problems. I know how to design counters in a series to count from n to n+k or the reverse but how to do this thing?


texts: Insulation Voltage of Aluminum PCB - With and Without Electronic Components

texts:
We are working on a product that contains an LED module consists of 66 LEDs (33s x 2p - 100VDC load voltage).

We'll use aluminum PCB due to the thermal requirements but the customer requirement claims that the insulation voltage for the aluminum PCB should be at least 1kV.

The PCB company manufactured the PCBs for us according to the requirement above then we tested it in our lab. Here's the test procedure:

Short the supply terminals of the LED module.
Apply increasing AC voltage gradually between the back side (i.e. aluminum) and the front side (the shorted terminals) until the generator stops (The generator beeps then stops automatically under a faulty condition -e.g. short- so we can determine the insulation voltage).

The results are quite interesting:

The insulation voltage is lower than 100Vac for an unused, empty PCB.
The insulation voltage is around 1.2kV for a final LED module (i.e. LEDs placed on the same PCB).

The image below shows an empty PCB (top) and final LED module (bottom):

Is this normal? Where can this difference come from?


texts: Can multiple different vendor FPGAs exist on the same JTAG chain and be programmed?

texts:
During development work, JTAG is used to configure FPGAs. For the final version of the system there would be a few different options that will carry out automatic configuration of the FPGA actively or passively.
When using JTAG there are different programmers from different vendors that are to be used to program the device. I am curios how would one go about programming a board that has multiple FPGAs from different vendors e.g 1 Intel FPGA, 1 Xlinx, 1 Microsemi and 1 Lattice Semiconductor. Having different JTAG ports on the PCB may be too much inconvenient, if we combine them all through a single "JTAG chain" then, we can't program them all in one go since they need different type of programmers.
Since the JTAG itself is a standard interface and any FPGA that supports it can be communicated in a similar way, I assume that we should be able to use a single device to download the configuration bitstream of the different FPGAs in one go once they are chained together in a JTAG chain. Is this true?


texts: Can the primary coil of a Tesla coil be inside the secondary coil?

texts:
I'm building a Tesla coil and the secondary coil (about 800 turns of 0.85 mm diameter enameled copper wire) is wrapped around a cardboard tube (about 8 cm diameter and about 1 m long).

I was planning to wrap the primary coil (about 10 turns of >= 1 mm diameter insulated copper wire) around a smaller cardboard tube (about 4.5 cm diameter and about 40 cm long) that will fit inside the larger tube with the secondary windings, however, most Tesla coils I have seen have the primary coil on the outside of the secondary coil and I could not find any information regarding this.

(Not to scale) I hope this rough diagram helps with understanding.

Will the Tesla coil work with the secondary windings (red) on the outside of the primary windings (yellow)?

If not, what is the reason for this, but if so, will I have to reverse the polarity or direction of the windings since the magnetic field is going in the opposite direction on the outside of the coil to the inside?

And finally, would the inner tube's diameter be large enough for the primary coil to work?


texts: Replace a 500Kohm potentiometer with a digital one

texts:
In layman's terms, I want to replace a Commodore 64 Paddle controller with a programable one.

I thought that the best approach is to replace the manual ~500k ohm pot used by the paddle with a digitial one, which will be controlled by a microcontroller.
But I noticed that digi-pots, at least the common ones, are no bigger than 100k ohm.

So, what should I do in order to have a programmable pot that supports up to 500k ohms?

I know that I could put five 100k ohm digi-pots in series, but I would prefer to use just one digi-pot if possible.

Can I amplify the output of the digi-pot by 5? How can I achieve that ? By using an op-amp? or something else? or should I take a different approach ?

Thanks!

update: Since it was asked, I'm adding more information about this:

what I'm doing is a remote controller for the c64. I'm using a esp8266 to control the joystick. And I'm sending the joystick movements from a smartphone. Basically a remote virtual d-pad. At that is working Ok.
But now I want to add paddle (and mouse) support to it. That's why I want to control the value the pots programatically.
(BTW: I'm building this device: UniJoystiCle )


texts: How to troubleshoot serial communication?

texts:
I connected my computer to a RM-BR300 controller to read its data, to try and mimic its functionality in the future.

I'm using RealTerm and a USB to RS422 converter for the job - here's the result:

Sony's VISCA protocol says packets should start with an address like 0x80 and end with 0xFF.

Why there are no visible packets in that sample?

What does the "UART receiver framing error" represent?

Here is the list of commands that could be sent by this controller.

This image shows some info on the USB to Serial converter:


texts:
I am trying to use the timers on the microcontroller in order to count up to 10us then add 1 to the int timer. I intend to use this in a project I am doing where I count the time between pulses from a circuit I have built. The code is as flows:

#include <msp430fr4133.h>
#include <driverlib.h>

unsigned int count = 0;
unsigned int button1 = 0;
unsigned int button2 = 0;

#pragma vector=TIMER0_A0_VECTOR
__interrupt void TimerA0_ISR0(void)
{
  count++;
}

void main(void)
{
  WDTCTL = WDTPW | WDTHOLD;               // Stop watchdog timer

    // Disable the GPIO power-on default high-impedance mode
    // to activate previously configured port settings
    PMM_unlockLPM5();
    //Setting up buttons
    GPIO_selectInterruptEdge(GPIO_PORT_P1, GPIO_PIN3,GPIO_LOW_TO_HIGH_TRANSITION);
    GPIO_setAsInputPinWithPullUpResistor(GPIO_PORT_P1, GPIO_PIN3);
    GPIO_clearInterrupt(GPIO_PORT_P1, GPIO_PIN3);
    GPIO_enableInterrupt(GPIO_PORT_P1, GPIO_PIN3);

    GPIO_selectInterruptEdge(GPIO_PORT_P1, GPIO_PIN4, GPIO_LOW_TO_HIGH_TRANSITION);
    GPIO_setAsInputPinWithPullUpResistor(GPIO_PORT_P1, GPIO_PIN4);
    GPIO_clearInterrupt(GPIO_PORT_P1, GPIO_PIN4);
    GPIO_enableInterrupt(GPIO_PORT_P1, GPIO_PIN4);

    //Setting up timer to count to 10us
    TA0CTL = TACLR;
    TA0CTL = TASSEL_2|ID_0|MC_1|TACLR;   //SMCLK, divider 1, up mode, clear timer, interrupt enable, interrupt pending
    TA0CCTL0 = CM_1|CCIS_2|OUTMOD_2|CCIFG;
    TA0CCR0 = 10000;      //count to 10us = 10/1MHz/1

    while(1)
    {
      button1 = GPIO_getInputPinValue(GPIO_PORT_P1, GPIO_PIN3);
     if(button1==0)
      {
        TA0CCTL0 &= ~ CCIE;              //disable interrupt if button 1 pressed
        timer = 0;
      }
      button2 = GPIO_getInputPinValue(GPIO_PORT_P1, GPIO_PIN4);
      if(button2==0)
      {
        TA0CCTL0 |= CCIE;                //enable interrupt if button 2 pressed
      }
    }
}

The way the code should work is when the second button is pressed the interrupt will enable and the counting will begin. Then when the first button is pressed the interrupt will disable and reset the timer.

The problem I am having is that when the interrupt is enabled, it will never enter the interrupt and increase int timer. I have set up the timer using the user guide and datasheet but I am unsure if I have set it up correctly. If anyone could shed some light on this problem it would be much appreciated!

UPDATE

The code has been changed slightly to fix suggested problems but still does not work.


texts: Why do compass chips in cellphones require frequent calibration?

texts:
Most cell phones offer digital compass functionality which uses a 3-axis magnetometer chip for data. Phones (some more than others?) frequently require the user to "recalibrate", which involves rotating the phone in a "swirly" or other pattern to populate readings over some fraction of a sphere representing the various orientation with respect to the local field.

The discussion in this answer as well as the 3D plots of data give an excellent overview of what is happening mathematically.  Roughly speaking, six parameters - a gain and an offset for each of the three axes - are fit to a dataset collected over a cloud of data points that at cover at least a chunk of that sphere.

I've done this myself with a magnetometer attached to an Arduino and fitting offline. The low cost chip I used seemed to drift a lot (being careful to do this outdoors and away from more obvious sources of error or gradients like nearby ferrous materials or other possible fields). I noticed that the offsets seemed to be contributing as much to the drift as the gains, if not more.

Question: What exactly is drifting within the magnetometer sensors in newer, high-end cell phones that still requires frequent recalibration? Is it simply temperature? If so, why wouldn't the magnetometers be internally temperature stabilized? Is it too hard to do in analog and the magnetometers don't have any ability to calculate offsets?

above: After paying a zillion dollars for a very nice phone, I feel like an idiot doing this (from here) while balancing on a bicycle on a busy street corner, or enjoying some beautiful view on a hike. My iPhone makes me go through a much longer, silly video-game-like task before it will even begin to tell me anything useful. I cary a normal compass sometimes because it just simply works.

above: Screen shot from this nice discussion of the principles and mathematics behind magnetometer based compass calibrations.  Here is another.


texts: 50ms Power Interrupt in DCDC Power Supply (18-32v)

texts:
I am a student doing a project and I have an interesting dilemma and I was wondering if anyone had experience solving this kind of issue.

I am designing the input protection / line filtering for a power supply module with aerospace applications.

I want the power supply to remain functional despite a 50ms power interrupt (input power goes to 0V for 50ms), so I am trying to determine a topology that can achieve this without massive capacitor banks.

Here are a few specs. for my system:
Input Voltage: 18-32V
Current Draw: 200mA
Temp. : -40C to 125C ambient

So far I have looked at the following options:

Capacitor bank on the output of the filter circuitry
Capacitor bank + boost driver on the output of the filter circuitry
Integrated Chip Solutions

Options 1 and 2 are quite expensive and require lots of space, so I would like to determine if there are good integrated chip solutions. I found the following in a design magazine but it was intended for a 12V input power supply.

Does anyone have experience with this type of problem? What was your solution? Most of the IC solutions I have found are intended for lower voltage applications, I need an IC output of 24V (ideal) or 18V (minimum).

Any advice / ideas / guidance would be greatly appreciated! Not necessarily looking for answers; general wise advice would be appreciated.


texts: Signal-driven 3 output logic gate decoder or switch?

texts:
I need to build a simple logic gate circuit such that when a single input signal or switch goes low it alternately activates one of three outputs as high. That is, every time it goes low the currently high output goes low and the next in the series goes high - cycling which output goes high between the three.

Years ago when I took an electronics class we used a program similar to CircuitLab. And I designed a very similar circuit. But I've lost that design and it was so long ago that I've gotten very rusty.

However, I can think of one way to build a circuit that would -almost- do what I want:

I could use a binary counter in combination with a 2-to-4 line single-bit decoder. (See the illustration on Wikipedia's decoder page.) The problem with that solution is it cycles between FOUR outputs. And my design requires that it cycles between only three.

As I said, I designed a circuit almost exactly like this years ago. And while the details are very foggy, I seem to recall that it was so simple that it only required one or more flip-flops (or latches) and a few other gates besides.


texts: Selection of External Current Transformer

texts:
simulate this circuit – Schematic created using CircuitLab

I am designing a product for motor protection circuit. where I want to use customized external CT for application which gives me better accuracy in current reading

Below list are power ranges of motor and their measuring current range. Based on current range I would like to choose  my external CT

My questions are, as per CT image attached

Calculation of burden resistor

How is burden VA calculated?
How to calculate burden resistor if I want to interface with PIC16F886?
How CT size can be reduced? What parameter do I need to change to make as per size 2 to meet accuracy requirements?
If I select this CT, what will be max current I can supply above without it going to saturation?
What is effect on burden VA if the current exceeds 100A?
How to calculate r1, r2, r3 for this circuit?

Considering AC1030 data sheet.
AC1030 datasheet
Ip=30A I max=75A
turns ratio: 1000:1
supply voltage = 220VAC
min power continuous CT can sense = 220X30 = 6.6 kW
Max power sense for short period=220*75=16.5 kW
Irms=1.4*30A=42A

burden resistor= 2.5/(42/1000)=59.5ohm
R1=R2=100kohm resistor.

Is it correct? What are other care I need to consider while taking hardware design?

In this type application we need to use normal CT or protection class CT 5p10/5p20 series?
How burden VA calculated?
How can I judge max voltage limit giving to Arduino Board?

CT measurement


texts:
I am using this pre-made PCB in order to bring my 12V power supply to 6V. On the datasheet, it is claimed that the efficiency is about 90% (hence I expected low heat dissipation). With great surprise when I plugged everything together, I've noticed that the PCB heats up quite a bit. I haven't much experience with these things and therefore I would like to know if you'd expect it to heat a lot or not.
I am scared that something is wrong.


texts:
I have a relay with following contact rating:

Since the maximum switching voltage is 250VAC/25A, can I use this relay to switch 380VAC/1A load? What is the consequences?


texts: Why is the negative contact in a battery bay always the side with some sort of spring?

texts: Is this just purely convention, or is there some kind of technical reason behind it?


texts: Dual polarity (+-12v) from a bench power supply?

texts:
I have an adjustable power supply (TENMA - two channels 30V-3A and one 5V-3A I think) and I want to get a +-12V rail from it.
By putting the supply into series it says that it has internal relays so I assume I don't need to bridge something (right??).
When in series mode I can seem to understand how to get positive and negative 12V potential in respect to the ground...
What am I doing wrong?


texts: My capacitor charger LT3751 does not charge

texts:
I built the below LT3751 capacitor charger, but unfortunately it is not working.
The capacitors are not charging and I don't see any dynamic signal at any of the chip pins.

The FAULT pin is in high state - 5V.
The DONE pin is also in high state.
No switching pulses on HVgate, nor on RBG.


texts: Is it possible to use an electrical motor with a constant torque while simultaneously turning against it?

texts:
I've been thinking about whether it is possible to have an electrical motor output a constant torque against which one can then apply a force without breaking the motor?
I guess the best example would be barbells or some other weight. The motor would pull a certain amount, and at the same time, a force pulls against the torque.
Another example would be a heavy door that is supposed to close when let go, but not as forceful to avoid noise, so the motor would pull against the weight of the door, but the door is still closing, albeit slower.
I have no experience with motors whatsoever, but I would think that one best takes a brushless torque motor. The question now is, is it possible to turn against the torque without breaking the motor?
Thanks!


texts: Altium Differential Pairs, nets not found

texts:
Question is similar to Differential pair in altium but different (not a duplicate)

Hi !
When about to ECO the schematic to PCB (Design > Update PCB), errors shows up showing that "net(s) not found in differential pair" for my nets.

Even though, the nets are named properly (same name, only _N and _P changes) and both nets have the DIFFPAIR. Still getting the error.

Example screenshot :

note that _ (underscore) shows as space because lines are above text.

Gives me this :


texts:
I have bought an ELCB and a mini DB board for a small solar/inverter project. My understanding is that an ELCB trips when there is a potential difference between earth and neutral. The diagrams I've seen online all show an earth connection to the ELCB, for example:

However, when I try to connect up my ELCB, I can only see the four main connections (live and neutral, in and out). Here, pics:

There are no other connections apart from those four. How is the ELCB earthed?

The only way I can think of is through the connection to the metal rail on which all the breakers are installed. However, the backing of the breaker does not seem to be conductive.


texts: capacative vs optical fingerprint sensor

texts:
I bought this fingerprint sensor (only the fingerprint sensor):
http://www.zjgrow.com/grow-k216r502-fingerprint-recognition-access-control-systemr502-capacitive-fingerprint-sensor-p1957700.html
R502 Capacitive fingerprint sensor
Now I tried to connect it to my arduino uno - unfortunately I only find documentations about how to do it only for the optical fingerprint sensor.
I now found this:
https://www.element14.com/community/community/design-challenges/designforacause/blog/2018/08/16/fingerprint-skeleton-key-capacitive-fingerprint-module-design-for-a-cause-challenge-blog-post-4
I connected it like he did and used the same code except changing my pins to 2,3 as suggested in the example code.
I get: Did not find fingerprint sensor :(
I checked the wiring - it is as it should be ( i also switched RX and TX just for check)
Any good documentation how to connect a capacitive sensor to an arduino uno?


texts:
I am trying to implement a non-linear inductor in LTSpice and to get it to saturate.

I am using the following directive between N1 and N2 as advised in the help files:

L1 N1 N2 Hc=12 Br=0.2 Bs=0.4 A=4u Lm=0.4 Lg=0.01u N=100

With a DC voltage supplied the circuit behaves as if it is purely resistive regardless of the voltage.

This is the circuit I am using.

Plot.

Is there something else that needs to be added here??

Thanks.


texts: Striking electronics facts, stories or puzzles

texts:
Say you are at a dinner table with like-minded, curious people, and you want to share your enthusiasm for electronics.

How would you entertain your audience? Would it be a Steve Jobs story, a summary of a recent breakthrough, some sort of puzzle, etc.?

P.S. I'm hoping the Electronics StackExchange community will enjoy this more lighthearted topic and not close the question off. :)


texts: Is it safe to drive multiple 'strings' of LEDs in parallel?

texts:
I am thinking of driving COB LEDs (rated at 10 W normal power) at 3 W.

I want to drive 32 LEDs from one 100 W constant current driver. The driver has a maximum voltage of 144 V. The LEDs are 35 V.

I can drive a string of 4 LEDs maximum in series.

Is it safe to drive 8 of these strings in parallel?


texts:
I have a small piezoelectric ultrasonic microphone (receiving signals of around 40 kHz). But the voltages it generates are too small to be read by my micro-controller's ADC. So I want to amplify the voltage created by the microphone.

I'd like a solution with a low part count, if possible. I've been trying to use an op-amp + some resistors, but I can't figure it out.
So, how can I amplify the voltage from the microphone?


texts: Are there ways to determine whether or not a fuse will blow if placed into a circuit?

texts: Industrial fuses are quite expensive when compared to the typical fuses found inside your automobile. While trying to locate a fault in a piece of industrial equipment, quite a few fuses were blown trying to use a trial and error method. Is there a way to test the account of current that will flow through a circuit without harming the equipment? Is there a way to tell whether or not a fuse will blow if placed into a circuit? At $30.00 dollars a fuse, I'd like to find a way to test whether or not the fault has been corrected, or if I will still blow another fuse if placed inline. Thanks in advance!


texts:
I have a RAID card where someone in their infinite wisdom decided that only the cathode side of the individual drives' fault/activity LEDs would be provided on the board, and the other side of the header unconnected; the "global" activity LED works normally.

My idea at this point was to simply connect all the anodes to the supply from the "global" LED; this works to some extent, but when the "global" LED lights up, all the others turn off.

Any idea what might be causing this?


texts: 8-bits synchronous up counter with arbitrary sequence

texts:
My question is about logic design, that's a subject that I'm studying now, especifically counters and registers. I designed a 8-bit counter using 2 4-bit counters (with load, count and enable signal) as base, but I wonder how to make it count this sequence: 24, 25, ..., 90, 24, 25 never passing through 0-23. How is it possible to making using this two 4-bits counters and some combinational circuits? Can someone help me with that?

P.S I've already tried to do it, but something definitely is wrong, and I didn't figure out what is :/
Thanks in advance for any help :)
KEY[0]=CLOCK
KEY1=LOAD
SW[0 - 3] = Parallel Load as well as SW [4 - 7]
KEY[2] = Count
KEY[3] = Synchronous Reset Button
LED[0 - 7] = Outputs, and 7 is the MSB

Schematic PDF: https://docdro.id/BiC4q3T


texts: Converting 400 to 500 mV signal to 0 to 10 V PWM signal

texts: I want to make a driver board for piezo mist maker which requires 10V 1.7MHz signal. So far I have created a signal of 1.7MHz and 0.4 to 0.5V (picture link added) with a crystal oscillator and 2 PNP transistors and bunch of resistors and ceramic caps (picture link added), now I'm trying to pump up voltage on this signal to make something like PWM signal out of this. I have tried comparator on several op-amps but I guess I have chosen them wrong because none of them works. I would be so thankful if you help me or tell me what I'm doing wrong or maybe introduce an op-amp that could work a comparator for me.


texts: Gain of Integrator Amplifier With Square Wave Input

texts:
Using basic circuit analysis techniques we can find the voltage gain of this basic integrator as follows:

\$i_1=\frac{v_I}{R_I}\quad\text{and}\quad i_2=-C(\frac{dv_O}{dt})\\\text{since:}\quad i_1=i_2 \ \rightarrow \ \frac{v_I}{R_I}=-C(\frac{dv_O}{dt})\$

From this we can derive the output voltage to be:\$-\frac{1}{RC}\int_{0}^{t}v_Idt+v_O(0)\$

If we look at it in the s domain, we can easily find the voltage gain of the circuit to be:

\$G_v=\frac{v_O}{v_I}=-\frac{1}{sRC}\$

This was easy enough. The only problem is, this is only valid if the input signal is a sine wave. Granted, the gain will approximate this value if the input signal is a square wave and it will be even closer if the input is a triangle wave, but it will not be 100% correct.

So my question: how can we modify this relationship to solve for the output voltage or gain of the circuit if the input signal is a square wave? I would think that since a square wave is composed of a sine wave at the primary frequency and a number of odd order harmonic frequencies, there must be a way to add to this and solve it more accurately.


texts: How do I know that a capacitor is real or ideal given admittance value?

texts:
I stumbled upon this exercise in my course and I was wondering how to do it.

I know that in:

-REAL capacitors: P ≠ 0 , and φ  ≠ -pi/2

-IDEAL capacitors: C = constant, and R = 0.

My admittance is given like this:

Y = 1 + j2 [S]

I also know that Y = G -jB. That would mean in my case that G = 1 and B = -2. Any ideas on how to continue this?


texts:
In order top prevent my seldom used deep well pump (3 Phase, 400V) I plan to daily spin it up for a few seconds.

Where the pump is located, the is no power supply (I operate the pump using a generator), but I can place there a 12V car battery and a solar panel for constant charging.

Is there a way to convert 12V to 3 Phase 400V power? Power is needed just for a few seconds.

The pump motor is rated 2.4A


texts:
I want to know the performance difference between AXI and Intel's quick path interconnect which has been replaced by Ultra path interconnect(interms of latency). This is for very low latency(25 microseconds per sample) motion controller application.

Thanks in advance!
Nivetha


texts: vellum and spray for toner darkening for PCB production

texts:
I understand that the best way to make a PCB the photo-resist way is to print a super-dark mask on a transparency put it on a circuit board, expose it and develop. The problem is that is expensive and my printer doesn't print 100% dark.

I currently use vellum (translucent paper) as my paper for PCB masks and even then when I try to do the PCB, some tracks go missing after using the developer yet the rest of the circuit is well intact.

I was researching and noticed from https://smrsoftware.com/vellumtips.php that one could use a spray called "Krylon tm  Artist's Matte finish spray #1311" to spray the artwork side of the paper to make the toner appear darker.

I'm wondering, is this a good idea, or are there chemicals in this particular spray that may negatively affect the PCB development process? And if I shouldn't use this spray, then what else can I do to darken the toner on the paper without trying to print on top of the artwork over and over again? Is there a better chemical out there? I'm looking for something that's for sale in canada. Maybe I need a chemical that has a certain ingredient? I don't know.

Please advise.


texts: This is my first design of a asynchronous buck converter, Vin 36V, Vout 24V, Iout 1A, Frequency switch 100KHz, based on "Basic Calculation of a Buck Converter's Power Stage" - slva477b Texas Instruments. It works as intended, while 1A load connected, without load outputs 29V. From other posts I understand that for this type of buck, duty cycle MUST be adjusted properly for different loads. How can this be accomplished, if possible, without feedback? Does the circuit need a minimum load ? Thank you


texts: continuous DC voltage across output pin of an IC (DAC output)

texts:
I would like to ask you one question.

Actually in the automotive there is chance of 20v or 5v continues output come across output of my IC (PGA400)i.e output of DAC.

I would like to know in general how would be the behavior of IC when we feed the output with power supply.

So I need to protect my IC output from this continues analog output. I very glad if you guys could give some inputs to me in designing protection circuitry on output pin.

I can use just a simple zenar with some resistor but I am not allowed to add any series resistance. As far as I know TVS diodes handle transients but not continuous voltages, so I can't use those also. I tryed using opamp buffer with some feedback resistor but it is becoming complex circuit.

I would like to know is there any simple way to handle my IC from this analog voltages.

In the below figure you can see ...

normally 20v not connected but user might connect it to the 20v instead of ECU input.So I need to protect my IC when 20v is connected.


texts: Can I get a 200mH inductor off the shelf that I can connect across AC mains?

texts: I am designing an automatic power factor correction system, for testing I want an inductive load. I want to use a pure inductor placed in series with a resistor, I have read of inductive load banks but they are just too expensive for my project.


texts: Is there possibility to "short" and lock a BLDC motor as on the DC brush motor

texts:
As we know, you can mechanically lock a DC brush motor by short the two terminals with relative strength. Now, in my design I wanted to use BLDC for reduced noise, but can I do something similar for the locking? What is the approximate strength.

This has to go bi-direction, so a Ratchet is not possible.


texts:
I draw a schematic which uses LM741 and IRF830.
The main function of the schematic is to light up a few leds (which consumes about 100mA in total) when the night comes.
Please have a look at the schematic and tell me if it is correct.
I am a beginner and I am trying to draw a schematic to see if I understood some things about electronics.

View post on imgur.com


texts: Equivalent ciruit parameters of a 1kVA transformer

texts:
I would like to conduct some simulations in Matlab/Simulink and I need to know the equivalent circuit parameters of a transformer with power rating around of 1kVA (regardless the primary and secondary voltage)

I did some research and I couldn't find all the parameters that I need. Is there anyone who has the parameters of a transformer similar to mine?


texts:
Doing some practice questions for exam and came across this.

I have done circuits like this but they have always had a Vcc and Rb on the base side. Thus I have no idea what equations to use and google is not being my friend today.

so yeh if anyone can point me in the direction of the equations to use for this circuit ill be very happy


texts:
We are facing issue with relay PCN-112D3MHZ. We are switching a FAN of 80 Watt at 220V AC with this relay. we are operating relay with transistor MPSA42. Micro controller is driving this transistor through 1K resistance at base. Coil voltage is 12V DC. Diode is also connected parallel to relay coil in reverse direction.

Some times relay get stuck at on position. when we send off signal from micro controller, transistor becomes off, but relay contacts are not released to make FAN off. when we switch off the complete supply(both AC & coil DC) for some time and switch it on again, relay still is in on position.

As per specification relay is of 3A. Any hints?


texts: USB charger with power bank charged from solar panel and peltiers

texts:
I would like to charge some batteries (maybe 1 lipo?) from either a 12V solar panel (about 300mA) or 2 peltiers (also about 200-300mA) in series (about 4V, but it’s really unstable and voltage changes every second) and get stable 5V for USB charging from that battery or battery pack.
What is the best approach? Can you please recommend me some circuits, buck/boost IC or anything?


texts: Three Phase Power. Phase Currents to Power and KVA calculations

texts:
I'm trying to learn a little bit more about three phase current, power and KVA.
We currently have some hi-tech UPS power systems at work and I'm trying to ensure that they are adequately provisioned to cope with a power outage.
The UPS's are rated to about 200KVA.

For simplicity imagine that two distribution boards are connected to the UPS. Each distribution board is capable of recording the current of each of the three phases.

Switch Board 1
I1=62.62 Amps
I2=67.4 Amps
I3=53.74 Amps

Switch Board 2
I1=60.52 Amps
I2=69.2 Amps
I3=54.44 Amps

We are in Aus where the devices typically run at 230-240V. Take the higher voltage please 240.

How do I use the known currents of each phase and switchboard to calculate:
A) The KVA of Each switchboard
B) The Power of each switchboard in KW

Please show any calculations in the solution.
If I'm missing any vital information please ask and I'll attempt to find out more.


texts: Bypass touch switch on humidifier circuit board

texts:
i have a simple humidifier that only powers on by a touch sensitive switch.
I need to bypass it because when the power is off after that the device doesnt start automatically.
I tried some things but i only know the basic on circuit boards.
Can you help me please?
Thank you in advance.


texts:
Many RS485 transceiver chips have a thermal shutdown when the junction exceeds 150C. Typically they switch back on once the junction temperature drops 15 degrees.

How long does that typically take?

Since the power is dropping to near zero, and junction to case thermal resistance is typically 50C/watt, does that mean it can potentially drop temp very quickly and recover within microseconds?


texts: How to safely discharge a lead-acid battery?

texts:
How can I safely discharge a large lead-acid battery, like a car battery or UPS battery?

I assume I use a thick copper cord (I have that in the form of washing machine electrical supply lines, about a 1/4" thick) and then put a resistor in line. The problems I see with this approach:

How do I size the resistor so I am assured I am not discharging too fast and risking an explosion?
My experience is that large resistors are sick-o expensive. How can I get an appropriate resistor without spending a lot of money? Can I use graphite rod? (I can potentially get those cheaply) If so, how do I size the rod correctly?
How do I know when the battery is fully 100% discharged and completely safe?


texts:
I’m trying to build a 5V output @ 200mA. I have a full wave bridge rectifier attached to a transformer with a capacitor reservoir of 100uF, using a LM7805 voltage regulator and with a 0.1uF cap as well. To get the 200mA that I needed I used ohms law to find I needed 25ohms (5V/0.2A=25ohms.) But that power will burn out my resistor so I thought that I should use 4x 1/4W 100ohm resistors in parallel to achieve the same result. When I turned on my circuit, my voltage regulator became super hot and the voltage I recorded was lower then 5V (3.8V).

I've attached the schematic I drew to show how I wired it. Can you tell me what I have done wrong ? Sorry for the crappy drawing in advance.


texts: difference between optocoupler and buffer

texts:
I am making a inverter (DC to 3 phase 2 level inverter) using IRF640 mosfets. I get my triggering pulses form a dspace kit (with matlab). I want to make drive circuit for my mosfets. I have seen a model circuit given by my teacher and it has both buffer (hcf4010be) and opto-coupler (TLP250) for pulses before giving to gate. From what I know opto-coupler can both isolate and boost the pulses whereas buffer only helps in providing load current without loading DSP pins (which I think opto-coupler does automatically).

My question is do we need both? I think opto-coupler alone is enough.

And one more, do we need to have separate DC supplies for each opto-coupler? I mean can't we use same dc supply circuit for all opto-couplers? (I will be using 6 opto-couplers)


texts:
I need to build a pressure plate to go on the front of a prop to be used in Airsoft.

The idea is this plate is both an target to be shot at and a visual representation of "health".

My initial thinking is along the lines of a translucent perspex circle mounted on springs in front of micro switches. It could have RGB LEDs behind it that can be changed from Green to Red. The electronics behind all of this are already handled as part of a larger project by an Arduino.

The problem for me lies in the physical design of this plate. Specifically, how to mount the plate in such a way that the pressure will reliably be detected and the plate will return to "off" position. Also, which types of switches to use. I was thinking maybe micro switches with long arms for leverage?

Maybe rather than micro switches some kind of membrane would be better? But would that be able to withstand getting shot at by airsoft weapons? Impact force on the plate will be <= 1 Joule from a 6mm plastic BB.

Any help gladly appreciated!


texts:
I am facing new problems everyday at embedded system. I have designed D-SMPS  and put an stm32f103 to drive mosfets.I have tested micro controller and it works well while giving outputs as GPIO.It is seen at image.

I have given 1ms delay to see square wave.

But when it comes to use TIMER PWM , logic level is not correct.

It is reducing to 1V. I have no idea why same pin gives different reaction at same point.

Do you guys have any idea how it may happen?


texts: Conductive magnet to read resistor value?

texts:
I want to know if I can hook-up a resistor to one part of a Magnet Snap (carried by SparkFun), then another magnet snap to analog-pin on Arduino and still be able to read resistance value? Is this possible with these Magnetic Snaps? Can anyone recommend other alternatives?

Is this a bad idea? How much would the magnets interfere with resistor value/resistance?

I understand that Neodymium magnets are coated in nickel, which is highly conductive, so this could be an alternative.


texts: Can I connect a "J1708" port to my computer?

texts:
This question is related to another question I posted here on the new Reverse Engineering site.

I'm working with a small public transit agency on a neat open-source project that will help us to offer realtime data to local developers. A key piece of data we need is the current bus route a given vehicle is on. Currently, there is only a single electronic system that knows this information: the vehicle logic unit (VLU) that each vehicle is equipped with.

When a bus driver begins a route, they type its ID number into the keypad on the operator control unit (OCU). This ID number is sent to the VLU, which then displays the appropriate text on the LED signs on the bus.

On the OCU, there are two DB9F ports. In the manual, they are described as "J1708 PORTS". One of them is connected to the VLU, and the other one is available for me to plug in to. Connecting to it gets me some data that you can read about in my other question.

Essentially, I'm questioning whether my computer is even properly hooked up to the OCU. Currently, I'm just running a plain old 6ft Straight Through Serial Cable (DB9 M/F) between my computer's serial port and either of the "J1708 PORTS". I can consistently get the same data this way, but I'm beginning to doubt that the data is being properly... transmitted?

I am now fairly certain that I'm using the wrong cable or something. Here's a diagram of the cable that is running between the OCU and the VLU: J1708.png

Do I need a similar cable to connect the OCU to my computer? If so, why is it still sending me non-random data when I use a plain old straight through DB9 cable?


texts:
I'm struggling to understand the diference between a Latch and a SR Flip Flop, I know that a latch is level activated, and the SR Flip Flop is edge activated but if the circuit is the same, why is the behavior diferent?

I watched this video from Neso Academy, I really don't know why the latch becomes edge active if I use a clock.

If i send a 1 the latch is active, so why isn't the SR flip flop active when the clock is 1?

Am I missing something or is there an error in the video?


texts:
I'm following a basic tutorial for AVR.

All seems fine but the speed? The problem is that if I leave the speed of the xtal commented the code works, but if I place it in 8 MHz or 16 MHhz [I'm using an Arduino board with a 328p], the led stays on a long time and unresponsive, so why if I leave the speed commented it works?

I checked the speed in the fuses and change it to 8 internal, 16 MHz external and same problem, what is this noob trap?

Here the code from link:

//#define F_CPU 16000000UL         /* 8MHz crystal oscillator */

    #define BUTTON_PORT PORTB       /* PORTx - register for button output?? PULL UP? */
    #define BUTTON_PIN PINB         /* PINx - register for button input */
    #define BUTTON_BIT PB3          /* bit for button input/output */

    #define LED_PORT PORTD          /* PORTx - register for LED output */
    #define LED_BIT PD4             /* bit for button input/output */
    #define LED_DDR DDRD            /* LED data direction register */

    #define DEBOUNCE_TIME 25        /* time to wait while "de-bouncing" button */
    #define LOCK_INPUT_TIME 250     /* time to wait after a button press */

#include <avr/io.h>
#include <inttypes.h>
#include <util/delay.h>

/* function prototypes */

void delay_ms(uint16_t ms);
void init_io();
int button_is_pressed();
void toggle_led();

int main(void)
{

    init_io();

    while(1)
    {
        if (button_is_pressed())
        {
            toggle_led();
            _delay_ms(LOCK_INPUT_TIME);
        }
    }
}

void init_io()
{
    /* set LED pin as digital output */
    LED_DDR = _BV (LED_BIT);

    /* led is OFF initially (set pin high) */
    LED_PORT |= _BV(LED_BIT);

    /* turn on internal pull-up resistor for the switch */
    BUTTON_PORT |= _BV(BUTTON_BIT);
}

int button_is_pressed()
{
    /* the button is pressed when BUTTON_BIT is clear */
    if (bit_is_clear(BUTTON_PIN, BUTTON_BIT))
    {
        _delay_ms(DEBOUNCE_TIME);
        if (bit_is_clear(BUTTON_PIN, BUTTON_BIT)) return 1;
    }

    return 0;
}

void toggle_led()
{
    LED_PORT ^= _BV(LED_BIT);
}


texts: Maximum error of nominal resistor combinations

texts:
Suppose you have resistors which have nominal values of \$R_0\$ or \$2R_0\$ but can vary to be anywhere between \$(1 ± .03)R_0\$ or  \$(2 ± .06)R_0\$, respectively, so each can have about 3% error.

Is it correct to calculate the maximum error of two possible combinations of these resistors as follows? (These are the only two combinations I care about.)

Parallel connection of two \$2R_0\$ resistors: \$2.06R_0||2.06R_0 = 1.03R_0,\$ correct value is \$1R_0\$, so overall 3% error. Alternatively, \$1.94R_0||1.94R_0 = .97R_0,\$ so still 3% error.

Series connection of two \$R_0\$ resistors: \$1.03R_0 + 1.03R_0 = 2.06R_0,\$ correct value is \$2R_0\$, so overall 3% error. Alternatively, \$0.97R_0 + 0.97R_0 = 1.94R_0,\$ so still 3% error.

A text I'm reading suggests that the second case of two \$R_0\$ resistors in series should have a maximum error of 6% and not 3% but I don't understand how.


texts:
If we are powering our PIC32 with a USB, why do we also need Vcc from an external power supply to provide to PIN8.
In my circuit I am powering the PIC32 with a USB, but when I check the value of voltage at the pin 8, it shows 0V. Shouldn't it show 3.3V ?


texts: define operation of a specific 555 circuit

texts:
I'm considering purchasing a pre-made circuit assembly with the following associated schematic:

Having looked at a typical 555 device datasheet, I'm unable to confirm the operating mode as the datasheet modes show the Discharge pin connected in some fashion.
What I would like the circuit to do is upon application of 5VDC as Vcc, the relay pulses once for the set time controlled by R1, and that nothing further happens. Can someone confirm that this is the operation of the relay or otherwise define what the operation would be?


texts: analog circuit to convert one resistance to another

texts:
I plan to have a thermistor attached to a CPU heatsink control the speed of a computer case fan.

For temperatures below 30c (room temp) I want to stop the fan, and for temperatures at or above 60c, I want the fan to run at full.

I've heard someone tell me it's better to use PWM to control the speed since I won't be dissipating so much heat, but it feels silly to use a whole arduino to control a computer case fan.  So unless you try to convince me that's a better approach, what I would like is to scale the response of the thermistor to a range of resistances that more closely approximates what the fan needs to reach those goals.

I know I can add to the resistance of a black box with a resistor in series, but I don't know how to scale the output resistance of the termistor.  (note: I'm leaning towards this one)

Any advice?

(PS - this is an educational hobby project; I know I could get a simpler premade solution off the shelf)

(PPS - I'd be open to using the 3-pin "fan 2" output from my motherboard (asrock A75M mini-itx), which is already controlled by a temperature, but I don't know how to apply the pinouts to a simple DC case fan)


texts: How do Dualshock 4 pressure sensitive buttons work?

texts:
I'm doing a reverse engineering research about the PlayStation 4 controller. I want to know how do the analog buttons work (the triggers in the bottom, not the analog sticks). I've found a nice teardown album and, there, I've seen this image:

I know from this page that the flexible film pins for each analog trigger are these:

Common: Oscillating between 0 and 3.3V.
Sig: Voltage divider output, active low.

I want to know if it is:

A capacitive sensor.
A piezoelectric film.
A force-sensitive resistor
Other

And, by the way, how does the circuit attached work? I suppose it will have some kind of Analog Digital Converter, filtering, amplification...


texts: How to test for ground loop using multimeter?

texts:
I am experiencing a hum in my audio line from my computer. I suspect it's from a ground loop. My monitor (which house the speakers) is a 2 prong plug is plugged into a separate outlet from the power strip of which the PC is plugged into. I thought this prevents a ground loop but I would still like to test.

I just got a multimeter, and I have no idea how to use it. All the examples I see on ground loop testing are not for PC/Monitor jacks.

Can anyone give me a step by step. I have this multimeter: Amazon Link


texts:
I have an understanding of DDR rank which I think is incorrect. If someone could join the dots then there would be more clarity.
Here is what I know

A DDR rank is a 64bit interface consisting of x8 or x16 devices
Each rank is controlled by an individual CS. So two ranks means 2 CS signals to control them
A CA bus is shared among devices of different ranks. Two devices in the same rank don't share the CA bus.
All of the confusion started when I saw the following images based on which I have few questions

In the above image as the CA bus is not shared, both the devices are on the same rank.

So does that mean external to the package the CS pins have to be shorted i.e CS0_A and CS0_B should be controlled by 1 CS pin from the controller?
If we keep the CS pins separate and don't short them, doesn't that make the operation dual rank?
Is an x32 bit interface from a package enough to constitute a rank?

Here is a dual-rank package from which I concluded that CA buses must be shared among devices of different ranks.

So in the dual-rank package should we have only 2 bit CS to control the two ranks or can we have a separate CS control for each device in the 2 rank config?

The rank concept is highly confusing hence the questions.


texts:
I'm using a 555 timer to drive the clock of my circuit.
However, even with capacitors from VCC to GND, and from Pin 5 to ground, I'm still getting this "bump" when the timer transitions from HIGH to LOW (and a smaller bump from LOW to HIGH).
This (I'm guessing) causes my other IC's to sometimes trigger on the falling edge even though the documentation specifies a rising edge trigger. They sometimes also trigger twice on the rising edge. I've tried putting 10uF capacitors from VCC to GND on the other IC's, which alleviates the issue a bit, but after some time I'm noticing they still triggering erroneously.
I've found the error depends on the number of other chips, amount of LED's, their resistances etc. Sometimes if I hook up the oscilloscope or just put my finger somewhere it works for a bit.
I'm struggling to figure out if this is considered normal, if I've hooked the 555 up incorrectly, or if the problem is located somewhere else. Any tips/help is greatly appreciated!
Here's how I've hooked up the 555 timer.

Heres the falling edge when connecting to Pin 3 and GND on the 555 timer.

(The Oscilloscope reads ~400mV even though I use a 5V USB power supply. Not sure why that's the case, but my multimeter reads 5V.)
Rising edge

And here's the entire setup.

Here are the edges without a capacitor from VCC to GND. The other IC's trigger very erroneously without it.


texts: What is a ‘dense integrated circuit’ or ‘integrated function’ and how does it relates to Area in Moore’s law?

texts:
I am very comfortable with the usage of the Moore's law and its impact on microelectronics. However I had always associated Moore's law to the gate length scaling as a factor of square root of 2 every two year. (This then leads to a related performance increase which is of our interest)

Only recently I came to realize Moore's law is about number of transistor per area which, I known, was very tightly linked but not anymore (For instance the 14nm technology does not have devices with 14 nm gate length but rather 14nm width finfets).

Still in most official definitions they do not use the term ‘number of transistor per area’ they would rather use the terms:

"number of transistor per dense integrated circuit" (Wikipedia)
"Number of component per integrated function" (Original graph from the paper 1965)
“components per chip” (IEEE, IEDM 1975 paper)

And thus my question:

What is the definition of a ‘dense integrated circuit’ or ‘integrated function’ and how does it relates to Area in Moore’s law?


texts:
What would I search for to find some information about this sort of switch and/or a replacement?

It's just two copper strips embedded in an insulator that get mashed together by a button.  It says 'JX-10' on it but that doesn't seem to help my search.

It sits in the base of an electrical heater resting on a plastic peg.  The peg rests on the floor and the weight of the heater pushes down on it closing the contacts.  If the heater falls over, the contacts separate automatically.


texts: Can I operate a 12vdc valve using a capacitor and AA batteries?

texts:
First, I need to specify I'm very noob, so maybe in my situation a vague awnser is better than something very specific, I don't know.

I want to make an airbow (airgun that shoots arrows) like the one Joerg Sprave made on his YouTube channel. Except, he powered it with a 12 dc battery, whitch is very straight-forward, but also quite expensive and heavy, compared to AA or maybe higher batteries, boosted with a capacitor. The thing is I know nothing of what to expect about the output of the capacitor. I know it can be quite high, because once I made fun of shocking myself with one made for a flash, with friends, and it gave quite a jolt. Anyway.

I want to have a switch button, once pressed it would give power to the valve just long enough to deliver the compressed air and shoot the arrow, so it doesnt need long, once the arrow it shot, any excess air is futile. If it's simple to install, I would like a LED to signal when the valve/gun is ready to fire, but it's optional.

I can go a bit with trial and error, but I wouldn't fry my valve in the process since it's the most expensive part of the project yet. I dont mind a schematic for the circuit if you can provide, but (ok I know I sound very helpless) if there was at least some clear note (e.g.: your valve, power source:aa battery), it would help me a lot to understand the big picture. I'm sure I can, but the last time I worked with electronics was more than 20 years ago, and I'm 37.

I hope my question is not too boring or too easy or too vague, thanks for any help.


texts: 2.4" LCD TFT backlight current limit resistor

texts:
I have some doubts regarding 2.4 LCD TFT ( NHD-2.4-240320CF-CSXN ) backlight current limit resistor value.
Datasheet note is not clear
6. Backlight: White LED / 3.1V / 100 mA ( Typ )
3.1V means:
a) backlight LEDs forward voltage ?
or
b) expected backlight source voltage  ?
I assume this means LED forward voltage.
Then, when powering backlight from 5V source the current limiting resistor should be (5V-3.1V) / 100mA = 19 ohms
Is that right ?
Thank you


texts: Building a 77GHz Band FMCW Radar with 0.25 Degree Angular Resolution

texts:
First some context. My group recently acquired some hardware for a radar related project, specifically a Texas Instrument AWR1843Boost (https://www.ti.com/tool/AWR1843BOOST) and a Texas Instruments DCA1000 EVM Capture Card (https://www.ti.com/tool/DCA1000EVM). Unfortunately, the AWR1843 does not have the angular resolution required for our application (we need about 0.25 degrees in the 77GHz band). Our original plan was to connect 2 AWR1843 modules together separated by some distance (basically a cascade system) and so increase the angular resolution. When asked, TI told us the AWR1843 doesn't support this functionality since multiple boards cannot be synchronized, and we should instead use a TIDEP-01012 (https://www.ti.com/tool/TIDEP-01012). The issue is that the TIDEP-01012 is significantly more expensive and still wouldn't offer the resolution we need, also given the extensive configurability of the AWR1843 it seems odd that it has no support for external triggering or synchronisation.
What radar system can we use that has an angular resolution of 0.25 degrees in the mm-wave band?
The more prebuilt the system the better, but pointers to suppliers or resources that could be used to build our own system would be greatly appreciated.


texts: What does the T symbol signify in electrical diagrams?

texts:
I'm trying to connect to my atmega1284rfr2 using the basic application circuit in their datasheet.  The red lines and letters are my own annotations.

I'm having trouble understanding what all the  mean.  Do they mean hook them up to positive supply?  Ground?  Dangling?

I get the impression that some should be dangling, but others should be bridged to ground, and others to the positive supply rail.

What do the T's mean?


texts: How to fix Arduino optocoupler + LED that doesn't light up?

texts:
I'm having a hard time understanding how an optocoupler works. I made a circuit based on example 15 if the Arduino projects book. Instead of trying to hack a button, I'm trying to just light an LED on either side of the optocoupler. I'm misunderstanding how this should work because the LED I'm trying to light doesn't light.

My youtube video shows my circuit. You can see the blue LED which runs from pin 2 of the optocoupler into ground lights up, but the red LED (which works, I verified) which runs from pins 4 to pin 5 of the optocoupler does not. I was under the impression that if I emitted high from the arduino to the pin 1 of the optocoupler through a 220 resistor (mine is 270 actually) and provided a path to ground that the optocoupler would be switched on and I would get current and ground from the pins on the other side.

Any suggestions - what am I missing?


texts:
I just purchased a lot of 40 solar cells each with 1.8 W, 0.5 V, and 3.6 A. This gives a total of 72 W. Ideally, I would like to connect the cells in a manner to yield 12 V. I know I can connect two sets of 20 cells (series) in parallel for 10 V and 7.2 A, or all 40 in series for 20 V, 3.6 A. I'm fairly certain there is no possible way to yield 12 V with factors of 40. I know I can use 24 cells in series to get 12 V, but then I won't be able to use the 16 other solar cells. I considered a DC-DC "buck" converter to convert from 20 V to 12 V, but I couldn't find any with a high enough current output.

I think I may have a way to connect the cells to get 12 V, but I'm not sure it would work. This circuit is going beyond what we are currently (pun intended) learning in my high school physics class. So would this work: One group of 23 cells in series. This gives a voltage of 11.5, an amperage of 3.6, and a power output of 41.4 Watts. Another group of 17 cells in parallel, 0.5 V, 61.2 A, 30.6 W. Then both groups would be connected in series. From what I understand (which could be completely wrong), the voltages would add to 12 V and the power would be 72 Watts. What I don't understand is what happens to the amps. I can calculate from P=VA that the amperage would be 6. I'm just confused as to how 61.2 A and 3.6 A could combine somehow and make 6 A (which makes me think that this might not work).

So does anyone think that this might work? If it won't, can I please be pointed in the right direction?