texts: Help with finding the value of current through a resistor in an RL circuit at a specific point in time

texts: This is a homework problem for my circuit analysis class.  I can't figure out what the heck I did wrong.  I know the solution to the relevant ODE is of the form I(t)=k1+k2*e^(-t/(R/L)), so I just need the values of the constants.  Since the switch is being opened, I(infinity)=0 which means that K1=0 and K2=I(0+).  Since this is an RL circuit, we should have that I_L(0-)=I_L(0+), right?  I found I_L(0-) by drawing the circuit with the switched closed and the inductor as a short circuit, then I used loop analysis to get I.  I know that part is right, because I plugged that version of the circuit into a simulator and got the same answer.  Unless I'm misunderstanding when I(0-)=I(0+) (and if I am, please tell me), that's the value of K2.  K1 is zero because the current will quickly go to zero after the switch is opened, making I(infinity)=0. L is given as 2H and I found R_th by drawing the circuit for t=infinity, removing the sources, and getting the equivalent resistance, which is how you get the Thevenin resistance value when there are only independent sources present, yes?  I tried it with R_th=4, 12, and 4||12=3 as well as 4+12=16, but all of those answers were marked wrong as well.  Can someone please help?


texts: Are there any opitions to soldering on a pinheader if you only want to use it once?

texts:
I have bought sonoff, it's a really nice electric switch with wifi. I want to flash it with a new firmware, using an FTDI adapter. In the tutorials I have found, they recommend that you solder on a pinheader onto the circuitboard (there are 5 small holes where it would fit).

I don't have the equipment and I really suck at soldering, so I wonder if there is any other options for connectig the FTDI to the board, I only need to do it once per sonoff, ever.

This is what it's suppose to look like, my sonoff is another version, so it's a lot trickier positioned.

Here is the sonoff if that matters
https://www.itead.cc/smart-home/sonoff-wifi-wireless-switch.html


texts: Problem isolating vias. Solder mask offset

texts:
I detected a shortcircuit between two vias in one of our PCBs. The shortcircuit was caused because an offset on the solder mask leaves part of the via's ring "half opened". When the PCB was assembled, a little amount of tin produced an electrical contact between the vias. The PCB has PTH and SMT components.

I think there should not be any offset on the solder mask at all. I will contact the PCB manufacturer. But I have some questions regarding this issue.

Is this offset error on the solder mask a remarkable manufacturing mistake?

In other PCBs without offset on the solder mask, it is still possible to have electrical contact on the vias, because the via's hole is open. But I have seen some PCBs with the vias completely hidden, filled with solder mask.

In case filling the vias were desired is there a special manufacturing process for it, or that depends only on the diameter of the via's hole?

Thanks!


texts: Can supplying DC power into an AC device break the device?

texts:
I have an AC device that takes 12 volts 47-63Hz AC. It is a water softner that is essentially an electromagnet. I lost the original plug and supplied it with 11.2V DC, it came on for a few minutes and no longer turns on.

Did the DC current break my AC device or is the DC power source broken?


texts: How does connecting different solar panels in parallel affect total current?

texts:
I've done a lot of research but only found info about batteries in parallel, which says higher voltage will charge lower voltage, which is unwanted, and that their currents add up.

So how is it different in the case of solar panels? Basically I hooked up a 12V panel to my battery charger, but wouldn't charge, turns out current is almost zero. (Is that normal?) It was part of a package to charge batteries built into a light- and motion-sensitive LED light. Not sure what batteries are in that one, panel is probably low-amp on purpose so it doesn't overcharge as it's always connected. I have another one of the same panel, but not worried about that as the double of almost zero will still be almost zero. However I have 2 of the small 5V panels with a bit better current, so I figured, can I hook them to the 12V to add amp?

Basically my main question is, would the amps add up? Also, would it still result in 12V? Would there be a side-effect similar to stronger batteries charging weaker? There doesn't seem to be a battery inside the 12V panel itself, just a panel, not sure about the small ones, I guess there must be as they still supply voltage for a while even when covered from light, they are the emergency chargers. So would the 12V blow them up? Or any other side-effects that I need to know about?

And if it's doable, how do I connect them? Originally I thought weaving the 3 + wires into one, same for -, and treat them as the 2 poles. Then I saw a diagram, where the + is connected to the + of another battery, and from there with another wire on to load, same for -. Or are these two the same? Only asking, because did an experiment with an electronics experiment "toy", and unified the 2 cables into one, and I got half the individual currents instead of the double, or the same, so I was baffled, maybe using the multimeter wrong? Could do videos if necessary but I'm still only trying to understand the very basics. Not progressing well while being confused by contradictory experiences.

Back to the panels though, if my idea is no good, is there another way to use my 4 panels to operate the charger? Additional info: large panels supply 10V actual voltage, small ones do 5.5V. Not sure about exact currents. Also charger runs on 12V 600mA when on mains.

Thanks for help.


texts: How to detect low RTC battery with low extra battery load?

texts:
I want to detect low battery in typical DS1307 circuit with microcontroller.

My first idea is to connect one of low cost comparator inputs to Vbat, another input to 2.0V from some voltage divider powered from 5V and (comparator) output directly to GPIO.

My second idea is to connect microcontroller ADC, maybe thru some voltage follower made with low cost op-amp.

If these ideas are good: should I pick comparator or operational amplifier with low input bias current instead of regular comparator / op amp?
How this is made in computer motherboards where BIOS can detect low battery and batteries last for few years?


texts: solar cell + capacitor + led : blinks delay proportional to light intensity

texts:
I'd like to build a batteryless circuit to blink an led.  I would like a solar cell to charge a capacitor until there is enough power to flash the led.  The led flashes and the cap goes back to charging.  This way the led will blink faster or slower depending on the light intensity.

From what I've read it seems a neon bulb might be required ?

Would this work ? The simulator charges the cap but the cap won't discharge through the led.


texts:
I've becomes a bit confused with the average power formulas.  These formulas can be found on Wikipedia here and here.  Let's suppose V(t) = 1V (DC) and we have a square wave for the current that switches from -1A to 1A.  If I look at the first equation, I'd get that \$P_\mathrm{ave}=0\$W because the average value of a square wave is 0; however, if I look at the second equation, I'd find that \$P_\mathrm{ave}=1\$W because the RMS voltage is 1V and the RMS current is 1A.

I don't understand which equation is correct.  They seem to be calculating different averages.  If someone asks for the average power, which do they mean?  What am I missing?

$$
P_\mathrm{ave} = \frac{1}{T_2 - T_1} \int_{T_1}^{T_2} V(t) I(t) \, \mathrm{d}t
$$
$$
P_\mathrm{ave} = V_\mathrm{rms} I_\mathrm{rms} = \sqrt{\frac{1}{T_2 - T_1} \int_{T_1}^{T_2} V^2(t) \, \mathrm{d}t} \sqrt{\frac{1}{T_2 - T_1} \int_{T_1}^{T_2} I^2(t) \, \mathrm{d}t}
$$


texts:
I'm working on a power distribution board for a couple of low voltage PCBs (mainly seperate microcontrollers on individual PCBs).
The idea of the power distribution board is to regulate the input voltage to it (12V) down to 5V and connect it to the microcontroller PCBs. Each microcontroller PCB will be connected to it's own header on the power distribution board and will have it's own regulator and fuse on the power distribution board.

My idea was to put the glass visible standard fuses on the power distribution board for each header so that at a glance I can see which ones were blown or not. Then I also thought for an added layer of protection, I should add PTC fuses on the input at the microcontroller boards.

The microcontroller boards may be unreachable in some cases, hence why I'm choosing PTC for them.

Is it worth double fusing? Am I not taking into account some side-affect of this?


texts: Why use or implement a DC/stepper motor controller? Is it not possible to connect the motor directly to an MCU output pin without the driver?


texts: Lines transferred from main memory to Cache

texts:
I'm studying Cache memories and I would like to know exactly how the lines are transferred from memory to cache.
Supposing I have a 32-bit machine with a 16kB directly mapped cache and 8 words per line. If the cache still is empty, if I run:
volatile int* b= NULL;
for (register int=0; i<5; *a+=512)
  *b=*a;

Exactly how many lines are being transferred to the cache? 5 lines (5 iterations of the cycle)? Only 1 line (last iteration of the cycle)?
Can someone please clarify me this?
Thank you!


texts: Correct procedure to identify a component and obtain the datasheet

texts:
I'm not sure what should be the correct procedure to obtain a component's datasheet starting from the component's package code.

I searched in the other questions, but I found mostly people asking what is a certain component, while I'd be interested in knowing the general procedure to follow to identify an unknown component.

In some cases, for complex components as ICs, a google search of the code shown on the package is sufficient to obtain the relevant datasheet, but I had less success with components as transistors, mosfets and so on.

An example: this component is identified as Q1 in the board, leading to think it is a mosfet. BTW, the terminals are identified as "B, C, E", as it was a transistor, and not "G, S, D" as I was expecting.
In this case I would try some google searches with the following strings:

GS H 2053 F 01 datasheet
2053 Transistor datasheet
2053 Mosfet datasheet

but none of them would show relevant results.
Is there any coding convention for this kind of component that can be useful to know for a better search?


texts: Generating two signals with small difference in frequency using one oscillator

texts:
I am building a data transmitter for which I chose FSK modulation. The frequencies should be around 27 MHz. I have single crystal with 27 MHz frequency and I need to get two separate frequencies that will be different.

I thought about amplifying the signal to generate harmonics, from which I will then filter out the frequencies I need. However this doesn't seem like the most elegant idea. I am not sure that this way I will get the frequencies to be close to each other. How is it done conventionally? Do they use two separate oscillators?


texts: How to calculate properties of voltage regulation circuits

texts:
I have a few options of adding voltage regulation to my pcb circuit (the regulation is from 12V to 5V). The options are stataed in the figures below.
My question is:

  How do I calculate the quiescent current and time lag for each of the designs?

Thanks!


texts:
I'm trying to find a "same or better" equivalent replacement for the 747 opamp. The footprint / pinout can be different, I don't mind.

Using the parametric search on Arrow, while reading the datasheet for the 747 I found that an LT1355 might do as a replacement. However, they are quite expensive; $16.89 for one single IC (DIP package). Searching for LT1355 on Octopart shows that Arrow are the cheapest for this one, but the price is too steep for me. I'm fine around $8/pc.

What other dual opamps can serve as a replacement for 747?


texts: Details about Total Access Communication System (TACS)

texts:
I'm not sure if this is the right place to ask.
I am trying to build a base station for a TACS (Total Access Communication System) phone, but I have not found any detailed document about it. The most I have found is a channel table and frequencies, but I would need all the details about channel negotiation, signalling and protocols.
It seems that any info about this old technology has been buried. I hope there is someone here that knows something more about it.
Update:
3GPP has told me they have no documentation since it was a pre-ETSI standard.


texts: I've salvaged  from audio system. Both have two contacts. Under , on the PCB plate there was "L704" and one loop symbol, which makes thing this is an inductor - what are it's properties then? It has two red dots on top and one black on the side.   has " 303j" written on it's top - I guess it's a 30nf (though meter showed nothing - it's blown) cap, but what type is it? It also has a bracket on top which indicates the negative electrode. Or the positive one.


texts:
I have been asked to improve the high end accuracy of a pressure sensor (Without modifying hardware). I have collected data from 30 samples and found a trend to the error. My question now is if it is possible using only this data to come up with a compensation equation that I can apply to real time measurements to remove the high end inaccuracy.
My first thought was to find a curve fit of the average error and apply that to new measurements but I didn't see as much improvement as I had expected.
Other ideas or recommendations would be appreciated.


texts: 12V Stepper Motor not working - vibrates but doesnt spin

texts:
I'm working on a project and unfortunately my DC motor is not working. I wired it like this, am using a brand-new motor (SP BN2A in this document, I scavenged it from a bidet I had at home), powering the whole system with a DC power supply so I can control the voltage exactly, using Raspberry Pi as the controller and using the following code:

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)

enable_pin = 5
coil_A_1_pin = 26
coil_A_2_pin = 19
coil_B_1_pin = 6
coil_B_2_pin = 13

GPIO.setup(enable_pin, GPIO.OUT)
GPIO.setup(coil_A_1_pin, GPIO.OUT)
GPIO.setup(coil_A_2_pin, GPIO.OUT)
GPIO.setup(coil_B_1_pin, GPIO.OUT)
GPIO.setup(coil_B_2_pin, GPIO.OUT)

GPIO.output(enable_pin, 1)

def forward(delay, steps):
  for i in range(0, steps):
    setStep(1, 0, 1, 0)
    time.sleep(delay)
    setStep(0, 1, 1, 0)
    time.sleep(delay)
    setStep(0, 1, 0, 1)
    time.sleep(delay)
    setStep(1, 0, 0, 1)
    time.sleep(delay)

def backwards(delay, steps):
  for i in range(0, steps):
    setStep(1, 0, 0, 1)
    time.sleep(delay)
    setStep(0, 1, 0, 1)
    time.sleep(delay)
    setStep(0, 1, 1, 0)
    time.sleep(delay)
    setStep(1, 0, 1, 0)
    time.sleep(delay)

def setStep(w1, w2, w3, w4):
  GPIO.output(coil_A_1_pin, w1)
  GPIO.output(coil_A_2_pin, w2)
  GPIO.output(coil_B_1_pin, w3)
  GPIO.output(coil_B_2_pin, w4)

while True:
  delay = raw_input("Delay between steps (milliseconds)?")
  steps = raw_input("How many steps forward? ")
  forward(int(delay) / 1000.0, int(steps))
  steps = raw_input("How many steps backwards? ")
  backwards(int(delay) / 1000.0, int(steps))

The motor vibrates and heats up when I power the system and run the code, but doesn't spin. What part of my system is wrong? Is it the hardware of the motor, the wiring, the code, the power supply, or something else?

Thanks, all help is appreciated.


texts: Capacitor selection from Linear Technology generated design

texts:
I'll preface this by saying I'm a SW Engineer. I've used the Linear Technologies Software to design a step down DC power supply from 12V to 6V. The package has given me a design but I'm a tad confused by the output capacitors given by the design.

The first output cap is a ceramic but is illustrated on the design as polarised. I thought ceramic caps weren't bothered with positive and negative connections. On top of that the spec for the cap is 10uF, ESR = 5M, and ESL = 0.3nH.

The second "Output Bulk Cap" is polarised, but I assume it can be electrolytic, and has values of 100uF, ESR = 15M and ESL = 1nH.

I normally do my shopping at Farnell's UK site and can't figure out what I need as there's nothing that comes close to 5 Mega Ohm ESR. Am I looking for a special type of cap which I'm not familiar with? I'd be very grateful for any pointers.

EDIT - this is the circuit: -


texts: How does this circuit do current limiting

texts:
Problem:

my photo diode recieves pulses of width 10ns-150ns and repeating at rate of 1Hz-50KHz

the current from photo diode depending on incident light can go from 10nA-100mA, so i have two photo diodes to cover the dynamic range, what i want to do is limit the current from a photo diode to 5mA lets say in one channel

My application needs me to do current limiting, so for this i found a hope with this patent

which has the basic circuit as below

typically i want to replace the I1 with my photo diode and in the question here even i tried to realize the circuit with suggestions in answers and even got few decent results

but the problem is i am not able to make out  this circuit in my mind in terms of current, when i observed in simulation the diode connected FET 52 does the job of discharging the excess current and current sources 30 and 40 are the saturation currents

fully realized circuit:


texts: What is this type of jack with contacts and light emitting diode called (from schematic symbol)?

texts:
I'm very very very new for electronics design. I have a basic electronics knowledge but I know there 's many things I don't know in electronics symbol universe. I searched for reference circuit of CM103AH and I found it but I don't know what this jack is, Is it jack with LED ? I only know that 1 - 5 is a jack.
Anyone can bring light to me what are 6, 7 and 8 ? or what is this type of jack called ?


texts:
I have been working on a project that is supplied by 8.4v battery.
I then used the 7805  voltage regulator to get 5v and supply the electronics.

Later, I figured out that I need to have 3.3v along with with 5v to supply a different module in the project that operates on 3.3v.
I looked for the LD1117V33 and a smiliar voltage regulators but I couldn't find any in my country.

I then decided to make a voltage divider as follows:

simulate this circuit – Schematic created using CircuitLab

Now, I've tested the output voltage and it was a perfect 3.3v.

Next, when I loaded the module.. it didn't power on!

I measured the voltage and it was around 1.5v.
I came to realize that the voltage drop was due to the parallel resistance that was inserted with the 2Kohms which decreased the overall resistance and caused a voltage drop.

What solutions are there?
Take in note that I do have the (Op amp 741), but I couldn't know for the sack of me to know the exact connection.
I saw few schematics, but I was not certain and didn't want to take the chance and blow up the expensive module I have.

Could you help in giving the right way to make a buffer in parallel with the 2Kohms?

Edit:
Is is possible to reverse engineer the R2 such that the overall parallel resistance = 2Kohms. Whihc will make the output voltage = 3.3v.

I know that after connecting my module the voltage drops to 1.5v!
So I can know the exact resistance of the module, or I can simply find it using an ohm meter.

Edit:
Based on a quick Matlab run with the following code:

close all
clear all
clc

RL = 544; %This was calculated. Because the Vout = 1.5v after adding load.
%Then Rparallel = 428ohms Therefore Rl was found to be 544.

R1=[1:10:10000]'; %Vareying values for R1

for i=1:1:1000
    Rp(i,1) =  (33/17)*R1(i,1);
    R2(i,1) = -(Rp(i,1)*RL)/(Rp(i,1)-RL);

end
solution=[R1,R2];

for i=1:1:1000
if(solution(i,1) <0 || solution(i,2) <0)
    solution(i,:) = 0;
end
end

Now when finding the solutions, The best as far as I see is at R1 = 271ohms and R2 = 15951 ohms.

Will this configuration work, or will it have any further effects or complications as voltage is linearly probational with current?


texts: Why can't the PIC18 perform a divide operation accurately?

texts:
I just noticed that when I am converting coordinates from N/S E/W format to decimal format it getting wrong product. I tested 1256/3600 which should be 0.3488888888889 but my pic gives me 0.3488922 and 7/60 which should be 0.11666666666 and pic gives me 0.116666794. When adding those products and the number 23 I get 23.46582 but it should be 23.4655555556. As I am building a laptimer I do not want this much error.
According to http://www.sunearthtools.com/dp/tools/conversion.php I need 0.00001 precision which is 1.11 meters. I could tolarate a bit more but not much more. I could give a guess that this is because of the processor but I really think it should be a way around it.

The formula I am using is: x + y / 60 + z/3600 where x,y,z are integers.


texts: How to lay out Gerber files for flex-rigid pcbs

texts:
I want to move to flex-rigid PCB design for our product, to eliminate need for the FFC cables we currently use.
I have found vendors providing this service but I cannot find any information on how to lay out gerber files.
My application had 3 rigid boards.  The "mother" board has 4 layers, with 2 x 2 layer  "daughter" boards, and single-layer interconnects which should be flexible.
Is there a standard for how to define this sort of design, i.e. which areas are rigid, and which are flexy?


texts: I'm new to this concept and parts of it are a little confusing. I understood the part when a 5V signal is applied as input, a channel is formed in the NMOS device, as the positive voltage attracts electrons, thus output is connected to the ground via the NMOS and hence 0 output. But when 0 volts is applies to the gates of both the devices how does the PMOS conduct for the output to be high? Since both are enhancement mode devices a channel does not exist beforehand and is brought about by introduction of a gate voltage. When 0 gate voltage is applied how does a conducting path get formed in the PMOS for the output to connect to VDD?


texts: Is there a method to find how to combine resistors in order to get a specific resistance?

texts:
I was working on this homework:

  Using only 1k resistors, synthesize a  resistor of 3/5k and a
  resistor of 5/3k. Use no more than four 1k resistors in each case.

I found how to do it but I'm not sure I used the efficient method. Indeed, I listed all the different ways to combine four resistors and computed the total resistance of each of them.

Does it exist a fastest method to find the good combination? Or does it exist some tables where the work is already done?


texts: Varistor + Inductor + TVS transient protection

texts:
I am struggling to understand how this circuit should work:

I understand that inductor in this case is going to reduce the rate of changing current flowing through it, but I do not understand what is going to happen during the transient. Which device should react first?


texts:
I'm currently a junior in highschool, and I've been interested in computer/electrical engineering, specifically microprocessor design. I've read Code by Charles Petzold, , and have begun reading the Microprocessor Design Wikibook (which seems to be incomplete.) Through reading Code, I understand the basic logic behind a CPU, and have begun building one in LogiSim. Chapter 17 in Code details the CPU I want to build, but the circuits lack key components -- clock signals, and instruction decoding. Some of the clock signals seem to be pretty obvious (the PC seems to need a steady clock signal) but others (like how to latch RAM values) I have had to think through and try to get working.

I can build a working accumulator (it can't be accurately called an ALU, I think, because it lacks the L part) that switches between addition and subtraction with a single input, and I understand this is all I need for the arithmetic part -- once I get jump opcodes working, I can implement multiplication and division in code. The part I'm struggling with is the instruction decoding. Through some google searches, I see that each opcode needs to be interpreted as multiple microinstructions, but I'm lost as to how I need this to work. Currently, my instruction decoder is just a combinational analysis circuit with a single binary output for each opcode -- 13 in all.

The way the code works is it has one 8 bit code value (I only use the low-end byte), and then two separate 8 bit address values that I then combine to be the 16 bit address input to the RAM. In order to latch the values, I have a separate counter that counts up to 10b and then resets to 00b. It is the clock input for each latch in turn (for the three latches, there's a, b, and c. the second clocks have a be 1 while b & c are 0, then b is 1 and 1 & c are 0, then c is one and 1 & b are 0, then it resets). But on instructions such as ADD 000Ah, the PC jumps to 000AH...which is supposed to be added into the accumulator, but actually gets latched into the code latch, and is then interpreted as the next opcode, which makes the whole thing go crazy.

I feel like I'm missing some big information regarding instruction decoding and how I need to do clock signals...

Here are the LogiSim .circ files:
https://dl.dropboxusercontent.com/u/61676438/PetzoldMk5/8BitAdder.circ
https://dl.dropboxusercontent.com/u/61676438/PetzoldMk5/8BitAdderSubtractor.circ
https://dl.dropboxusercontent.com/u/61676438/PetzoldMk5/8BitInverter.circ
https://dl.dropboxusercontent.com/u/61676438/PetzoldMk5/8BitLatch.circ
https://dl.dropboxusercontent.com/u/61676438/PetzoldMk5/ID.circ
https://dl.dropboxusercontent.com/u/61676438/PetzoldMk5/PetzoldMk5.circ

PetzoldMk5 is the main CPU, relying on the other files to be imported as libraries.

Here's a list of opcodes (all binary):

Load                 0001
Add                  0010
Add w/ Carry         0011
Sub                  0100
Sub w/ Borrow        0101
Jump                 0110
Jump w/ Carry        0111
Jump W/ 0            1000
Jump w/o C           1001
Jump W/o 0           1010
Store                1011
Halt                 1100
Reset                1101


texts:
How do these electronic calipers work?:

I know they work by measuring the capacitance of the running track, somehow. But how do they use capacitance to measure distances - is it a linear relationship of capacitance to distance, or is there something else going on? These are really accurate - specification of ±0.02mm from 0-100mm, and the resolution is down to 0.01mm. I'm also surprised at how these can meet the specifications at the very low price point - I picked up mine for £8 and tried it against a few common objects I knew the dimensions of, and it checks out.


texts: What is the meaning (definition) of "current-starving"?

texts:
In several circuit descriptions we can find the term „current-starved“, „current-starving“ or „voltage-starved“.

Example

In chapter 4 (Current-starved voltage-controlled oscillator) we can read:

  This VCO is designed using ring oscillator and its operation is also
  similar to that. From the schematic circuit shown in the Fig.(3), it
  is observed that MOSFETs M2 and M3 operate as an inverter, while
  MOSFETs M1 and M4 operate as current sources. The current sources, M1
  and M4, limit the current available to the inverter, M2 and M3; in
  other words, the inverter is starved for the current.

From this, I derive that „current-starved“ is similar (or even identical?) to current-limiting. Is this correct? Does anybody know the definition of „starving“ in this context?


texts: Altium: how to explode an imported 3D model

texts: I've imported a 3D model of an enclosure and I want to check if my PCB will fit inside the box but I can't "open" the box inside Altium. How can I explode or take a 3D model apart in Altium?


texts:
Hi I am a novice at using stepper motors, and I am learning as I go on.

However, I was wondering if there was a way to delay the steps between each step in my stepper motor without using the delay, because I understand that using the delay puts the whole program on hold. In the future, I would like to be able for the user to input different number of steps for the each stepper. Or have ps2 thumbstick hooked up so that the steppers can simultaneously move in the x and y axis (since I am making a cnc), resulting in a diagonal line.

Even though with the delay the steppers do run at the same time, they vibrate really badly. However, indivdually they are smooth, so I suspect it may be because of the delay.

So, any thoughts? Here is the code.

     int IN1 = 5;
     int IN2 = 4;
     int IN3 = 3;
     int IN4 = 2;
     int IN1_1 = 9;
     int IN2_1 = 8;
     int IN3_1 = 7;
     int IN4_1 = 6;
     int delay_time= 5;
     int count = 0;
     int i = 1;
     void setup(){
     pinMode(IN1, OUTPUT);
     pinMode(IN2, OUTPUT);
     pinMode(IN3, OUTPUT);
     pinMode(IN4,OUTPUT);
     pinMode(IN1_1, OUTPUT);
     pinMode(IN2_1, OUTPUT);
     pinMode(IN3_1, OUTPUT);
     pinMode(IN4_1,OUTPUT);
     Serial.begin(9600);
   }
   void loop(){
   int s = 200;
   int x = 0;
   //Function that rotates the first stepper motor
   step_one();
  // Fucntion that rotates the second stepper motor
   step_two();
   }

 //definition of these functions
 void step_one(){
 digitalWrite(IN1, LOW);
 digitalWrite(IN2, HIGH);
 digitalWrite(IN3, HIGH);
 digitalWrite(IN4, LOW);
 delay(delay_time);
 digitalWrite(IN1, LOW);
 digitalWrite(IN2, HIGH);
 digitalWrite(IN3, LOW);
 digitalWrite(IN4, HIGH);
 delay(delay_time);
 //I want something else to be able to replace these delays
 digitalWrite(IN1, HIGH);
 digitalWrite(IN2, LOW);
 digitalWrite(IN3, LOW);
 digitalWrite(IN4, HIGH);
 delay(delay_time);
 digitalWrite(IN1, HIGH);
 digitalWrite(IN2, LOW);
digitalWrite(IN3, HIGH);
digitalWrite(IN4, LOW);
delay(delay_time);
}

void step_two(){
digitalWrite(IN1_1, LOW);
digitalWrite(IN2_1, HIGH);
digitalWrite(IN3_1, HIGH);
digitalWrite(IN4_1, LOW);
delay(delay_time);
digitalWrite(IN1_1, LOW);
digitalWrite(IN2_1, HIGH);
digitalWrite(IN3_1, LOW);
digitalWrite(IN4_1, HIGH);
delay(delay_time);
digitalWrite(IN1_1, HIGH);
digitalWrite(IN2_1, LOW);
digitalWrite(IN3_1, LOW);
digitalWrite(IN4_1, HIGH);
delay(delay_time);
digitalWrite(IN1_1, HIGH);
digitalWrite(IN2_1, LOW);
digitalWrite(IN3_1, HIGH);
digitalWrite(IN4_1, LOW);
delay(delay_time);
}


texts: Problem in simulation results in PSPICE using LM3880 sequencer

texts:
When simulating this simple sequencer circuit in PSPICE, I obtained these results which are not the wanted ones:

I was supposed to have sequences but here I don't know what it is. The right sequence is this one:

The value of C1 is designed according the datasheet information, for 56µF EN pin will be power-up after 10ms then the power-up sequence will be generated. But as you can see, the EN pin isn't pulled after 10ms neither the sequences are released.


texts: I'm batch making pcbs that have fpc connecters with high pin count (50) and fine pitch (0.5). I'm soldering these by hand and was wondering how I could batch test continuity? at the moment I am going through each pin with a multimeter and it's too time consuming. I'm thinking of making a test board of some sorts? any advice is welcome, I'm pretty much a noob with electronics beyond the very basics


texts:
So, they're insulators or poor/non-conductors of electricity.
Yet somehow they are also capable of holding and/or transmitting an electrical charge.
Does that not seem like a crazy paradox, contradiction, or oxymoron?


texts: Is there a possibility of repairing this garden solar led lamp?

texts:
I bought several solar lamps that look like this:

They have a flame effect.
Like all other such solar garden lamps the solar panel is too weak. When there is little sun in two days they are empty.
Since I already had one solar panel at home, I came up with the idea to connect all the solar lamps with that solar panel to additionally charge the batteries during the day.
At first I did it with only one garden lamp, purely for testing, and everything worked just fine until yesterday.
The lamp has stopped working even though the battery is full.
Now I'm afraid my solar panel fried something in the garden lamp.
The output voltage of the additional solar panel goes up to 12V depending on the intensity of the sun, and the built-in solar panel gives maximum 2V.
Since I don't want to fry other garden lamps, I ordered this:
Converter Step Down Module LM2596
With this I will adjust the additional solar panel gives maximum 2V, and in that way I will additionally charge the other garden lamps, everything will work fine regardless of whether there is enough sun.
Now I'm wondering for this one, which I fried in some way, can it be saved and what can I check?
Look at the pictures:

When I connect the AAA battery to that faulty garden lamp, just for a second, the two LEDs turn on and off immediately - the others LEDs don't work at all.
I don't know if the LEDs are damaged or if something else is wrong.
What can I check? What can I do ?
I'm not a professional, so if you can mark the pictures and explain it will be a little easier.
It's a shame to throw it away if it can be fixed


texts:
I try to connect an EVAL-ADXL345Z-M (Data sheet) to an adafruit-feather-m0-adalogger (Data sheet).
4 wire SPI is desired.
Is it correct to connect it like:
Adafruit Feather M0 to ADXL345;
GND to GND;
MISO to SDO;
MOSI to SDA;
3V to VS;
3V to VIO;
Port 10 (depends on code) to CS

Thanks!


texts: MOSFET: When can we not assume that the gate current is 0?

texts: A common rule of thumb you hear when learning Electrical Engineering is that the gate current of a MOSFET is always approximately 0. When is it not safe to assume that it is 0?


texts:
I've designed several PCB boards for different experimental products for the small company i work for.

Now it's time we move from experimental to actual production. So far the boards i've designed where sent to a manufacturer, and then i soldered every component myself (yeap, really small company).

I'm aiming for the next pcb to be sent for assembly with a pick & place machine, and i've never designed any board for this purpose, so i really don't know what considerations i have to keep in mind with such a design.

I need a detailed answer as to how to design boards for production with pick & place machine, and what are the most important facts to keep in mind.
(I've searched the forum and couldn't find a "general" set of rules or tips, all answers are for particular questions and overlook general design criteria)

As a comment, right now if i placed components too close to each other or the design is too crowded of components, i can figure it out myself when soldering, or use some "tricks" all because i know every detail of the board, the intention here is that with the files i create anyone could send this board to manufacture and assembly, with no prior knowledge of the circuit. I hope i was clear as to what i'm asking, else comment and i'll elaborate a bit more.

Edit: All resistors and IC's are surface components, caps are of both types, there are some terminals and connectors, but 90% of the board is surface mount, so probably the through hole components could be soldered by hand.

Edit 2: I understand the answer to this might have to be too broad, maybe recommend a book regarding this topic?

I haven't decided the manufacturer, should i ask to all manufacturers in regards of their limitations? Surely there has to be some standards, or at the very least typical pick&place machine dimensions or default values as how many different component sizes allowed and the like.

Sidenote: I'm familiar with Altium Designer and Kicad, but if there's need of an extra software i have no problems in learning.


texts: How to Prevent Current Drain from an Android Phone's USB Connector?

texts:
Noob alert - I'm very much a hobbyist not a professional so doubtless fall into the 'little knowledge is a dangerous thing' category.

So... I have a project which requires simultaneous charging of an Android phone and a power bank. Pretty straightforward - essentially I have a Y cable whereby a micro B USB socket at the base of the Y connects to 2 micro B plugs, one plugs into the phone, the other to the power bank. Power applied to the socket flows to both devices and charges them. Works fine.

However when I unplug the external power to stop charging, the phone loses approx 10% power per hour compared to 4% if the phone is unplugged from the Y cable. I assumed that the power bank's charging input was draining current from the phone so tried the obvious solution (to me, at least) of inserting a rectifier diode into the +V line supplying the phone. However the phone wouldn't charge, presumably due to the voltage drop across the diode. So I then added a step up converter (1-5V input to 5V output) between the diode and the phone. This seems to work, in that the phone charges OK and the power loss when not charging is reduced to around 4%. However,

I'm sure this is terrible engineering practice and
the diode and step-up converter run extremely (dangerously?) hot when charging, even with a heatsink.

So all advice and better solutions for preventing the current drain would be much appreciated, thanks.


texts: BLDC motor current sensing for load torque

texts:
I would like to control 14V BLDC motor of battery powered drill. What I want to do remake the drill to nut runner (torque wrench), so I need to sense a motor current which is proportional to motor torque. My controller will include microcontroller. Here are some questions:

How battery voltage discharge can affect motor current measurement depending
on the same load (for example I would like to wrench the same nut
ant the same torque Nm)? Does it will affect my current reading and
the current will increase?
Could I sense the BLDC motor current directly on the battery high side or do I need to sense it on all three the motor phases?
Is it enough to sense only current to create closed loop torque control, or do I need some additional parameter for torque control based on the different battery discharge levels?

UPDATE:

Okay, for now this is more clear. Please correct me if I am wrong: I do not need to sense voltage of the battery for any calculations or compensation. The only thing I have to sense is motor current, because the current is proportional to the torque. The battery discharge will not have any impact for the current measurement, depending on the same load torque. So shortly, I will get the same current readings when the battery is fully charged and the same current readings when the battery is discharged let say to 60% of full voltage.

What I plan to do is to create relationship table between current readings and torque (Nm) of a load, and save these values in a microcontroller memory. So when the torque wrencher reaches knowing current value, controller will know that the bolt or nut is wrenched with a fixed known torque and motor stops.

UPDATE 2:

The things with current and voltage sensing seems ok. But I forgot another thing - temperature of motor. What impact to the torque (current) will have temperature changes in motor? What is the relationship between temperaute and current of BLDC motor?

Thank you for your answers.


texts: How to make IR proximity detector immune to the daylight?

texts:
I am trying to make an infrared proximity measurement device.

I want it to be in the range of 10cm or 4" (maybe 15 cm?). The frequency I use is 10 KHz. Here is the circuit I used, except that I have used 1 nF capacitors and resistors that suits them for band-passing 10 KHz. I have used LM358A for the OP-AMP and I don't know the part ID of my IR diode.

To increase the sensitivity and remove the offset, I added a difference amplifier with a gain of 10 using the other OP-AMP inside the LM358A. I've used a potentiometer to set the voltage to be subtracted from the out of below circuit.

It works! With a reasonable linearity. However, the voltage levels change with the day light intensity.

Is there any way to make this device immune to the daylight using an LDR? I've tried to connect the LDR in parallel with the offset removing potentiometer, however, as obvious, that didn't give good, logical results. I do not have any IR filters and it is really expensive to get them from Farnell or such in Turkey.

From here.

Edit:

Here is my schematic:


texts: Reason for using this resistor network at I/p and O/P

texts: I am designing a board using CDCLVC1108. I referred to the EVM and found a resistor divider kind of Network at output and input. What might be the need for these?


texts: Bipolar output from DAC with unipolar supplies

texts:
I want to use a unipolar 12-bit DAC (MCP4725) as a function generator with bipolar output (from -2.5 to +2.5V). Problem is, I only have two supplies of +5V and +12V referenced to the same ground, so most opamp based solutions go out the window since I am unable to give a negative power supply to the opamp. I need to get a bipolar output from this circuit, where the 'ground' (reference) of the circuit using this bipolar output is the same as the ground of the power supplies.

I have given this some thought and arrived at a conclusion that logically it would not be possible to get bipolar output from unipolar output. However, the wise people here have proven me wrong earlier and I wanted to try my luck.

TL;DR: Get bipolar output from unipolar DAC, only positive power supplies, same ground everywhere.


texts: The benefit to make or use a surface mount 4-terminal current sensing resistor

texts:
I find some precision SMD resistors are 4-terminal, like vishay's CSM3637P. It's constructed as below:

It seems it only make a slot on each pad, then get two extra pad to do the voltage measurement.

If using a normal two terminals chip resistor, I can route it as below, then what's the benefit using the 4-terminal one?


texts: Eagle polygon fill overlaps pad on edited component

texts: I am using Eagle version 8.4.0 and I am having a problem with a component that I edited where my ground fill is overlapping the pads. The component is an LM78xx from the Sparkfun library. I changed the shape of the pads from round to long and rotated them 90°. When I updated my schematic/board the changes show up but the polygon fill for the ground plane did not change. I saved everything, closed and reopen the project and even deleted and recreated the polygon. It still has the overlap. I have made similar edits to other components on the same board, just changing the size of the pad--not the shape, and they work fine. Someone please tell me what I am missing... and thank you.


texts:
I purchased a WS2812B 5050 RGB LED Strip from ebay (http://www.ebay.com/itm/121979001999?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT) and I'm trying to light it up to test and make sure it works.  To do this I attached the red and green wires (which should be power and data) each to a 5v power supply and the black wire to ground.  I attached them to the side with the arrow facing away from the plug since I think that's where I have to plug it in.

Since this is an individually addressable LED strip I assumed this would turn all the lights up white, but what happened is all the LEDS flashed for a fraction of a second the first time I plugged it in and then turned off.  Since then I can't get the LEDS to turn back on.  I'm wondering if I blew the strip, but it says it can support 5v so I don't know how.   How would I go about just lighting up all the LEDS white(or just any color it doesn't really matter) on this individually addressable LED strip?


texts: Why is this capacitive circuit not working in both multisim and LTspice

texts:
The voltage at the top most node of this circuit should be the average of the input voltages.

Vtop*CT = C1*V1 +C2*V2 +C3*V3  where CT = C1+C2+C3

I get 0V instead.

UPDATE

Thanks for the help. I managed to make it work by adding resistances in parallel with the capacitors.

CT = (20uF+10uF+10uF) = 40uF

4Vtot = 15V*2 +3V + 4V

Vtot=9.25V as seen in the graph

Here's what i was trying to simulate:
http://sci-hub.tw/https://www.sciencedirect.com/science/article/pii/S1434841116308524


texts: Need good and thin heat conductor without electrical conduction

texts:
I have a 3D printer with magnetic hot plate and steel sheets. One side of the sheet is uncovered (bare metal) and with the usage the sheet scraped some parts of the heatbed PCB mask resulting in exposed copper traces. The sheet started to touch those traces and short-circuit everything so more mask got burned and exposed. The base is still usable and works fine with full covered sheets but the problem continues.

I also tried to repair and apply green solder mask but once a sheet is touched it got scraped. Sheets are thin and sharp... Magnets are too powerful to apply or take sheet vertically so as a sheet is inserted at an angle it scrapes the PCB.

My question is, what's the best material I can use to fix this and apply a electrical isolator between bed and sheet? It must be thin so that the magnet still grabs the sheet and a good heat conductor but without electrical conduction. I'm OK with tape if that will do.

PS: I most use mostly 60°C and 90°C at heat bed, but 115°C is occasionally used, so material must survive that temperature.

In home i have krypton tape and blue painters type, don't know if that will do for what i need.


texts: Problem with waveform output .tr0 of hspice

texts:
I'm trying to see my project output waveform through CosMosScope but I get the error "The file format is not understood", while it gets job concluded in .lis file and simulate as well in avan waves.
I'm using HSPICE 2008 and CSCOPE 2015.
can anyone help me with this error or an app as well as cSCOPE(Freeware if possible)?
Best Regards


texts:
I am using a resistor divider to an analog pin on Arduino to sense the voltage of  a battery. I've recently been going through my IC's and found a device that can be used as a voltage buffer. I am aware that a voltage buffer spits out what it gets in, so 5V in is 5V out. However, I am unclear on:

  A voltage buffer amplifier is used to transfer a voltage from a first
  circuit, having a high output impedance level, to a second circuit
  with a low input impedance level.

Further, will this benefit my resistor divider given that their might be fluctuations in load on the circuit due to devices drawing more or less power causing inaccurate measurements?

Please explain as if I am a layman, I'm just starting to get into more advanced electronics aside from connecting pins together.


texts: Impedance of 4 conductor system spaced horizontally apart

texts:
I have 4 cylindrical conductors spaced equally and horizontally apart. How can I calculate the magnitude of Impedance (Z) using the Skin effect and Proximity effect?

I'm looking for an equation that will output Z given things such as the cross sectional area, length, frequency, and physical constants.


texts:
Let's consider a device such as a game controller or a standard remote control, but which is not controlled by "standard" keys. Instead, the idea is to minimize finger movement, such as in a keyer. What would be the best way to detect rather small finger movements - things like these come to my mind:

TPA511GLFS

JS1300AQ

Some notes on what I'm thinking about:

Doesn't necessary need to be a mechanical device
It would be good to support more then 4 / 5 directions - e.g. 9-way (i.e. w, nw, n, ne, e, se, s, sw + down) would be much better
While I'd like to hear experiences about these types, it would be better to have a way to either prevent or at least detect accidental "typing"
Obviosly, finger movement is the variable to minimize - I'd say 1/2" would be the threshold here
Let me know if I'm thinking in the wrong direction (too hard? better in some other way? etc.)

I'm mostly looking at your past experience in this area:

Did you ever have to build / maintain anything remotely similar?
Why would or would not you use the same component / process?
How did the final product turn out (e.g. in terms of ease of use)?


texts:
I've cobbled together a solar panel charger that outputs 10V @1.5Ah.

The manual for the Samsung S8+ recommends charging at 9V 1.67A or 5V 2A. I ended up contacting Samsung Support to see if they knew more details on the voltage input range and whether there is any leeway in that 9V recommendation.

I wasn't too shocked to hear the support fellow reading out the manual verbatim that it should be charged at 9V only.

My understanding is that almost every smartphone contains a charging circuits to regulate overcharging, overdischarging, etc.

Could anyone clarify or confirm what range of voltages from a DC power supply to a modern smartphone is fine before you start causing damage to the device?


texts:
Possible Duplicate:
  Resistors with ends of the same colour

I know the values of resistors if they are gold-colored at the end. When both ends are the same, such as brown-r-bk-bk-brown, I am in problem. How to know which side has the last color and which side is the starting end? Does thickness of band matter?


texts:
When using an H bridge IC such as L293 which has enable inputs, is it possible to tie outputs together such that an 'enabled' output is joined to a 'disabled' output without ill effect? In the system I am thinking of (to do with DCC Train control) there would never be a time when both tied outputs would be enabled but could be a time when neither was enabled. Is this possible? (or harmfull to the IC?)

I am very new to this website so don't know how to add schematic.
However, what I want to do is to use this device to power a point (turnout) section of track in a model railway using DCC. In one position of the turnout I want to power the frog with one output(say the A side) with the other tied output (B side) disabled and then in the other position of the turnout the power comes from the B side with the A side disabled.


texts: What is the purpose of these capacitors in this State Variable Filter schematic?

texts:
I need some help understanding this schematic. It's a state variable filter based parametric equalizer. What are the capacitors C4, C5 and C6 for? Are those coupling capacitors like C1 and C7? Are they necessary? Because, if I simulate the schematic without them, I still get the same function.

Thanks for your help.


texts: is it possible to obtain the intensity of reflected laser light from a DVD or CD-Drive?

texts: I would like to play around with my old CD Drive and stumbled upon the idea of using the CD drive as optical detector for depth or light absorbance. Is is somehow or with some devices possible to obtain the raw data e.g. voltage drop from the detector ?


texts: Calculating lengths of single-stub transmission line when all 3 characteristic impedances differ

texts:
Consider a transmission line circuit like the following but where \$Z_{o2}\$ was also unique (say \$Z_{o2}=7\,\Omega\$):

I know how I would find \$l_1\$ and \$l_2\$ using smith charts:
$$Re\left\{Y_n(z=-l_1)\right\}=\frac{Z_{o1}}{Z_o}=0.5\rightarrow l_1=\left(0.106\lambda,\,0.394\lambda\right)$$
$$Y(z=-l_1)=Y_n(z=-l_1)\cdot Y_{o1}$$
$$Y_n(z=-l_2)=\frac{-Im\left\{Y(z=-l_1)\right\}}{Y_{o2}}=0.161j\rightarrow l_2=(0.161\lambda,\,0.349\lambda)$$
but, since I would like to write a program for calculating this, I need to be able to solve this from the governing equations.
Starting on page 230 in this book, the author describes the equations used for matching a circuit where \$Z_o=Z_{o1}=Z_{o2}\$ but how would I solve this problem in the more general case?


texts: STM32 Blue Pill connected with both USB and SWD at the same time?

texts:
I would like to write some code for the STM32 Blue Pill to use the USB as a serial link. Because I use an ST-Link debugger to program the board, I will need to connect the following:

Programming: laptop - ST-Link - STM32
Testing: laptop - USB - STM32

I can connect them one at a time, but it would really hamper the test process, going back and forward repeatedly. It would be nice if I could have them connected at the same time.
I read the following at https://stm32-base.org/boards/STM32F103C8T6-Blue-Pill.html:

Warning: The +5V pins on this board are directly connected to the +5V
pin of the USB connector. There is no protection in place. Do not
power this board through USB and an external power supply at the same
time.

I'm not sure what this means. Will I damage anything by having both of the above mentioned connections at the same time?


texts: Using a behavioral voltage source as a zero crossing detector for inductance current in LTSpice

texts:
I'm trying to simulate a buck converter IC in LTSpice (MP4569) based on the functional block diagram from the datasheet using behavioral voltage sources to represent the logic from the block diagram.

I have 2 switches in place of the high and low side mosfets and the switches are driven by behavioral voltage sources.
I'm trying to implement the zero current detection block (ZCD block on the diagram) with a behavioral voltage source with the condition comparing the current to a threshold (V=(I(L1)>1m), the number is arbitrary, just a small near-zero value, could be zero.
The LTSpice model is available here.

I end up having the output of the ZCD voltage source in the simulation to be always 0 (after the initial 1 in the very beginning), BUT the current in the inductance is oscillating (very small amplitude) just above the limit in the ZCD voltage source (whatever I set it to). Also the simulation slows down to a crawl at this point and never completes, I have to stop it.

It appears that it does trigger the voltage source, but very briefly and it's not visible on the output when plotted in the simulation, but it does affect the behavior of the switch.
Maybe some kind of hysteresis is needed around the zero current for this ZCD voltage source, but I cannot figure out how to add it. I tried adding a flip-flop with 2 behavioral voltage sources connected to Set and Reset but it didn't help and I'm still getting similar behavior


texts: Combining two exact USB battery packs in parallel to increase current in a simple fashion?

texts:
I am wondering how I could put two USB battery packs in parallel together in order to increase their amperage/current.

I do not want to tamper with the Battery packs, as breaking them apart and soldering a new connector is out of the picture for the scope of the project, so I was wondering if I could do the following to accomplish the task:

Attach USB cables to each of the two exactly same battery packs, cut off the positive and negative ends of the USB exposed cable and solder positive to positive, negative to negative. I would then solder the input red/black wires of the item I want to power to the now negative-negative positive-positive ends of their respective USB wires.

Would this work? Can a quality USB cable be able to transfer 4.8 amps?


texts:
I have a PDF of a PCB I want to etch using toner transfer (photo inkjet paper in a laser printer). The design is fairly small, but I have 8.5x11 paper.

What I'd like to do is print a grid of the design on one sheet. How do I do this?

To make things complicated, the pdf is a secure pdf.


texts:
I'm studying this kind of CMOS switch:

I have some doubts about some sentences of my book.

1)

"For many analog applications, a switch is used merely to
transfer a charge from one node to another and to set a voltage on a high
impedance point."

What does it mean "high impedance point"? In our switch I just see a capacitor at the output node, but the impedance of a capacitor is not necessarily high

2)

"With the switch in Fig. 2.17 in the on state, after a transient, we have Vout=Vin hence the drain to source voltage of M1 goes to zero. The MOS
enters the linear region and its on-resistance is approximated by

[...] We assume an exponential response of the circuit (we neglect any operation in the saturation region)"

The concept that, after a transient, the drain to source voltage goes (ideally) to zero is clear: indeed, assuming the capacitor initially discharged, the current which flows through the capacitor charges the capacitor and the output voltage increases, thus reducing the drain to source voltage. Moreover, if Vds is very small, the author replaces M1 with a resistor, thus obtaining an RC circuit. What is then the meaning of the sentence "we neglect any operation in the saturation region"?

3)

"The value of the source voltage is equal to the input signal. When the input approaches the gate control, the overdrive diminishes and, at a given level, vanishes. At this point, the on-resistance goes to infinity and the switch no longer operates properly."

Why does the author assume that the source is the left terminal of the mosfet (indeed he neglects Rin, thus the input voltage is equal to the source voltage)? Assuming M1 to be an NMOS, theoretically I don't know which terminal the source is: in an NMOS the drain is at a higher potential than the source, but who knows here which terminal is at higher potential? Indeed, if Vin suddenly increases, the output will be a little lower than Vin, thus the left terminal of M1 should be the drain.

4)

It seems that the author of my book assumes a constant input signal. Can the input be, in general, a variable signal (e.g. a sinusoidal signal)?

Thank you


texts: Small, low power electrically driven mechanical latch?

texts:
I am trying to design a mechanical system which will allow ~2mm of movement (against only its own friction of movement) when an electrical signal from logic circuit is given. Think: a coin suspended from the ceiling by wire, dropped when an arduino drives logic high.

A simple solution would be to have a small solenoid with the wire looped over the core set up so that when the voltage is applied the core retracts into a housing forcing the wire off the core and to fall. The problem with this is that most solenoids require fairly high currents (I have a 'small' 5V solenoid which requires ~1.1A to retract) and are quite bulky.

Another solution I've considered is to use muscle wire, which contracts ~3% upon electric heating. You could have a spring loaded bolt that is pulled back but the datasheet suggests that 320mA would need to be applied for ~1s to a 66mm wire to gain 2mm of travel — this is viable but I'm wondering if there's something better?

I don't need any particular speed to drop my coin (a second's lag would be fine) but the lower power and the smaller the better. Generating mechanical movement from electrical impulse is generally not a low-power endeavour, but am I missing anything simple?

Thanks!


texts: Help identifying component in digital thermometer

texts:
I am a High School Junior doing a product breakdown for a school project, and I was wondering if one of you could help me identify a component or just tell me that it is a type of Chip On Board (which is what I suspect)? It is a digital thermometer (a really cheap one, about $10). The component that I need help identifying is the little black one that sticks out of the top of the circuit-board (next to the white wires and crystal oscillator).

Thanks in advance!

Oskar

EDIT: added the following to clarify that I know what the big black blob is and the location of the component: "(next to the white wires and crystal oscillator)"


texts:
Up to now i have been able to determine the values of resistors. But i can't seem to understand how to find the value of the capacitor (Cb).

Question: Calculate Cb to let pass frequency starting from 100 Hz. How do i find the impedance of the capacitor Cb, so i can find the actual value of capacitor to be used in this case.

We have,

R1 = 390 KOhm
R2 = 82 KOhm
Rc = 5.5 KOhm
Re = 1 KOhm

E12 series is used to determine the value of the resistors.


texts:
I am helping a friend with enhancing his camper van. Situation is as follows: He may go camping for a 2weeks and want to use car grid to power lights, charge cameras, phones etc. But don't want to risk discharging battery too much(he need to start big diesel)

My idea is to wire second(utility) battery(in the back of the car) parallel to main battery. But not directly. I plan on using switches or relays to disconnect the utility battery when voltage gets below certain point. That will enable him to use remaining power in utility and ensures he can start a car. Then comes the charging/balancing the batteries. To limit balancing currents resistor(beefy one) will be placed between batteries until difference is low enough to connect them directly again.

With help of simple arduino whole system can be totally "set it and forget it". Is it really that simple or did I miss something important?

EDIT: According to responses I probably badly described what worries me. Its connecting batteries in different state of charge. I am not very familiar with lead-acid, but from my knowledge of LiPo you cannot simple connect them and let them balance on their own because you will damage more discharged battery by charging it too quickly. It also generate lot of heat in the proces and currents are tremendous. Hence the resistor between utility and main bat after discharging one bat more than the other.


texts: Star quad cable: Why does the white wire have noticeably less resistance?

texts:
I ordered the star quad Canare microphone cable, but I do have a question: why is the resistance of the white wire noticeably less than the resistance of the blue and shield? (The blue and shield are roughly the same resistance.)

I have made 25 ft. XLR cables and pin 2 (white wire) is noticeable less than the other two. The other two are roughly .50 Ohm and the white wire pair is .35 Ohm. This holds true for each cable I made.

Very curious. Would like to quickly pick an expert's brain. Thanks

http://www.canare.com/ProductItemDisplay.aspx?productItemID=53

As far as I can see the strands are all same gauge. I would have thought the shield would have the least resistance.


texts: What electrical anomaly can cause RCBOs to trip in apartments in several buildings at the same time?

texts:
Once I had a weird electrical event in an apartment building I live in. Suddenly the Residual Current Circuit Breaker with Overload protection (I'm sure it's exactly this kind of device) in the main panel serving my apartment tripped. When I opened the panel it turned out that RCBOs for all the apartments on the same floor also tripped. That looked suspicious and so the next day I inquired with the utility company and they said that dozens of people in several buildings served by the same power substation had the same issue at the same time and the company hotline had an inrush of phone calls.

I don't get it. RCBO should trip when either there's an overload or if there's an imbalance between the phase and the neutral behind the RCBO (between the RCBO and the load). Clearly it's extremely unlikely that dozens of people had either of those at the same time, so I assume that was some external event.

What electrical event could have caused such effect?


texts: I need the most basic circuit diagram for wireless energy transfer please

texts:
I have been all over the net looking for the most basic circuit diagram or instructions to put together a small project on wireless energy transfer. If anyone knows of a good schematic that is super simple and geared towards noobs could you please share, or leave instructions. The simplest one I've found so far is this one off of some Hungarian guy's youtube channel.
 His website is here:

It's kinda hard for me to decipher and I when it comes to the capacitors I have no idea where to find these components. Found a few at the ol' radio shaq but some I can't find anywhere so I'd like a simpler circuit if there is one. If you know of an even simpler one to get me started with experimenting with w.e.t. please share or point me in the right direction. Thanks!


texts: ATMega2560 timer not increasing again after overflow

texts:
I want to generate waveform with f = 196 Hz using only normal mode.
Here is the code I use. Whenever the timer overflows TOV1 is set and PIND0 will toggle. TOV1 is cleared after that and I wait for another overflown to happen so PIND0 will toggle again.

I tried my code, with PIND0 connected to the LED. On power up, the LED turned on and off a short time after that but it didn't turn on again. Because it had turned off means that the overflown happened so PIND is toggled but I don't know why it didn't turn on again. I even tried to not clear TOV1 but get the same result as TOV1 is cleared.

#include <avr/io.h>
#define F_CPU 25690112UL
int main(void)
{
    TIFR1 |= (1<<TOV1); // clear timer 1 overflown flag
    DDRD = 0xFF; // set port D as output
    TCCR1B = 0b00000001; // using internal I/O clock with prescaler 1
    while(1){
        while(TIFR1 & (1<<TOV1)){
            PIND ^= (1<<PD0); // toggle bit 0 on port D
            TIFR1 |= (1<<TOV1); // clear TOV1 by adding 1 to TOV1
        }
    }
}

Can anyone see an error in my code?


texts: Confusion about the Injection of electrons and electron holes in a BJT

texts:
On page 354 of the 6th edition of Microelectronic Circuits by Sedra & Smith under Current flow, the following statement is made;

  Current will consist of two components: electrons injected from the
  emitter into the base, and holes injected from the base into the
  emitter.

According to
wikipedia,

  an electron hole is a conceptual and mathematical opposite of an
  electron.

Moreover,

  If an electron is excited into a higher state it leaves a hole in its
  old state.

This is where it get confusing. Does the injection of holes from the base into the emitter imply a loss of electrons, i.e electrons injected from the emitter into the base or something else altogether?


texts: Propagation delay and its measurement in datasheet

texts:
I am referring to Gate driver LM5102

Here the terms are bit misleading

1] Lower turn off propagation delay

2] Turn on delay

But application curves uses different measurements symbols(tp/tdl)/names,
I am now assuming turn on delay is  50% of VI to 10% output

Propagation delay is 50% of input to 50% of output
Is this right but application curves speaks differently

How is it measured ?


texts: help understanding ba5954fp sled motor driver application circuit from datasheet

texts:
i'm trying to drive a sled motor (bipolar, 4 wires) using the IC BA595FP
i found in the datasheet this application circuit:

i'm not very familiar with the terminologie of datasheets, so i have the following questions:

1- My stepper motor is 4 wires but there is only two pins in this ship for the sled motor, it's PIN 11 and 12 ? where should i connect the other two wires of the motor ?

2- What does μ-COM in the left upper rectangle mean ? StandBy, LOADING ?

3- Concerning the first rectangle, does DSP mean the source of PWM signal used to control the sled motor ?

*any sources are welcome,
Thank you

datasheet : BA595FP


texts: Direct contact to infrared receiver from microcontroller

texts:
I have posted this question also on arduino forum but can't get more answers there.

So basically I have an old DVD player that has an IR (infra red) receiver and I would like to automate it with a NodeMCU micro controller. I can do it the easy way: record IR receiver signal and then replay it from IR transmitter using MCU. However, I don't want to do it this way, maybe because I want a different / more difficult solution or i'm just dumb. I would like to drive the IR receiver without using IR transmitter, using some sort of direct connection from MCU to IR receiver.

What has been done so far:
Original plan was to use transistor that would control the signal (make signal go LOW/HIGH with MCU, so i can simulate IR output) that the DVD player receives like this:

However I got a lot of noise and so another user suggested that I use optocoupler like this:

And I still got noise, I was suggested that MCU probably can't output enough miliamps (MCU gave 10mA) to optocoupler (max operating with 60mA) so I changed the scheme to use external power that controls the optocoupler:

Credits to 6v6gt from forum.arduino.cc

Heres the latest result im at using transistor together with optocoupler:

You can see that it sort of looks like IR NEC protocol.
This now ALMOST gives what I wish to achieve, but still has a lot of noise. I don't have the right equipment or knowledge to understand what is causing it and would really appreciate suggestions and help.
Thank you for reading this.


texts: Large capacitors "producing more I²R heating"?

texts:
On page 35 of The art of Electronics Third Edition, when describing the disadvantages of reducing ripple by choosing large capacitors, the author writes:

  The very short interval of current flow during each cycle(only very
  near the top of the sinusoidal waveform) produces more I²R heating.

However, isn't Q = I²Rt? So a shorter interval should result in less heat - why is more heat produced?


texts: Pausing a clock signal generated by 555 timer

texts:
I am planning to make a simple integer adder/multiplier which needs a variable frequency, comparatively slow clock (around 1 to 200 Hz) for demonstration purposes. I used the following generic 555 timer circuit to generate the required clock signal.

simulate this circuit – Schematic created using CircuitLab

(Add more D flip-flops if more bits needed)

I want to pause the clock when the circuit detects a data overflow (sending a 3V logic signal) to stop the calculation process and hold its states. Not being the most familiar with electronics, I tinkered around in Falstad and noticed if you interrupt the connection between output and the "feedback" rail (Trigger, Threshold, and C1) , the timer will be stuck in its current state. The circuit will then be like such:

simulate this circuit

So, let me divide my question into two parts:

1. Can I simply use a switch (say, a BJT or a relay) to interrupt the the feeback rail to pause the clock?

2. Can I simply use BJTs or MOSFETs as the switch here? If not, can I use BJT-based octocouplers? The simulation from Falstad shows that BJTs/MOSFETs interfere with the clock signal.

Falstad schematics, using a relay controlled by a BJT


texts:
I'm recently trying to design a flex PCB. I haven't been able to find any specific tutorials on how to do this in Altium. But I did find Altium blogs detailing some of the best design practices for rigid-flex PCBs.

One thing that I haven't been able to replicate is the hexagonal hatch that they say enhances flexibility. I've trying to do this through polygon pour without any luck.

I would like to know if anyone has managed to achieve this type of hatch! Thanks!


texts: High current usage from LDO when not hooked up to VIN

texts:
I built a circuit powering an ESP8266 MCU from an MCP1811 LDO so I can use a 5V logic level. The MCP puts out 3.3V as desired by the ESP. The circuit looks as in the data sheet example:

Assuming the ESP is constantly in deep sleep mode, it is supposed to use around 20uA. When I actually power the whole circuit with 5V through the MCP and monitor the current with my power analyzer device, my actual current draw is 18uA, which is great! I verified that the ESP is in proper working condition as well. Now I hook up a 3.3V supply directly to the VOUT of the MCP and let the VIN floating, by not hooking anything up to it, I measure a current draw of around 400uA! I am wondering how this happens, I would have assumed that the current draw would be the same and the MCP would just not operate... Any solution is appreciated!


texts:
I am using Xilinx's PCIe Core, which in its latest version duplicates the AXI valid signal 22 times.
This means writing something like {22{1'b1}} every time I try to drive the valid bit. (http://www.xilinx.com/support/answers/50579.html)

I am wondering if I can do some magic, so that I have an interface that has a vector with 22 duplicated bits on the Xilinx PCIe Core side, but just one bit on the side I connect to.

While I can simply assign to a wire which I duplicate in my module I would love to know if I can achieve the same inside the interface.

Is it legal to have modports that do not include all wires of an interface (That way I could have one valid pin for the userside modport and the Vector for the core side)? Can one have assignments in an interface?
Or could I do some magic to cause a write to a member in a union to result in updates of other members of the union that do not share bits?


texts: How can i stop DC motors from dropping out my arduino?

texts:
I am using a MX1508 DC motor driver module to power a couple of motors with an arduino pro mini as the controller. when i connect the circuit as per the schematic, the arduino resets every so often when changing the motor direction.i can rectify this problem by giving the arduino its own separate battery. my question is; is there any other way of 'isolating' the arduino from whatever problem is being caused by the motors or is a completely separate power source the only answer? i have created similar circuits with servos in the past and not had any problems...
Thanks.

update:

I have just found a solution to my problem; i briefly stop the motors (bring all pins low) before changing their directions. this seems to have worked. Any ideas what is going on 'under the hood' ?
Thanks


texts: Most of the literature on building radios from scratch implies the use of single-layer air core coils. Yet, most of the coils I see in old radios are multi-layer coils. Is there any advantage or disadvantage to using multiple layers? Why aren't more homebrewed radios built with multi-layer coils?


texts: Should I wear a grounded ESD strap when probing/debugging my raw boards?

texts:
Manufacturing and handling the unpowered boards, the assembly workers often use strict ESD control: dissipative mats, smocks, and grounded wrist bands.

As an embedded engineer, I am always powering and probing up my raw boards (without the plastics enclosures) at my cubicle... JTAG debugging them without any sort of ESD safety.

What is the recommended guidance on this? Should I be worried about ESD? Do I need to be wearing any ESD gloves/strap?

note: the humidity in my office is around 40-50%


texts: What is referred to as CMOS sensor rolling shutter width?

texts:
I know what a rolling shutter is. But what is referred to as the "rolling shutter width"?

Wikipedia:
CMOS sensor: Active pixel sensor
Rolling Shutter

I don't think Focal Plane Shutter is related because I don't think a mechanical shutter is used. I am not 100% sure though. If somebody tells me that "rolling shutter width" is a term used with mechanical rolling shutter, that is fine. - Wikipedia Focal Plane Shutter


texts: Lead Acid AGM battery testing - Why am I testing it this way?

texts:
OK, so maybe it's not fair asking YOU why WE test something the way we do.  ;)
Here's the thing -- Our company uses AGM Lead acid batteries in some products.  The testing methods are ancient (but so is lead-acid technology).  There's nobody left in the company to ask these questions of.  We have "what" well documented, but rarely is "why" written down.
Our application is most similar to a golf cart or fork lift.  "Traction batteries" I believe these would be called.
I've asked the battery manufacturers but I can't get a straight answer.  I suspect this may be a case of Llama Dung
For a 12V battery (example) we do 150 cycles of the following:

Discharge battery at 13A until voltage reaches 8V
Rest 3 minutes (during this time, the battery voltage will recover)
Discharge at 5A until voltage reaches 10V
Perform slow charge (about 8 hours) until battery is fully charged
Repeat ad nauseum

The part nobody can explain is why we do a 2nd, lower current drain of the battery before recharging.
This may be a chemistry question (in which case I'm not qualified to really understand the answer I'm sure).
Anybody know something about this that I've failed to be able to Google??  (Believe me, I tried!!!)
Heck I even read the relevant sections of Lindens "Handbook of Batteries".  All I could find was this one sentence..
" Intermittent discharge, which allows time for the electrolyte to recirculate, or forced circulation of the electrolyte will improve high-rate performance. "


texts:
I am new at this. I am trying to interfacing 1602A LCD display with MSP430G2553 via PCF8574. When I run the code, nothing happens:
#include <msp430.h>

unsigned int *ptxData;
unsigned int count = 0;
// [0..3] -> power on, [4..5] -> function set, [6..7] -> display off, cursor off, blink off
// [8..9] -> clear screen, [10..11] -> right, do not shift, [12..13] -> display on, cursor on
// [14..15] -> write char 'B'
unsigned int txData[] = {0x03, 0x03, 0x03, 0x02, 0x02, 0x00, 0x00, 0x08, 0x00, 0x01, 0x00, 0x06, 0x00, 0x0F, 0x24, 0x22};

void main() {
    WDTCTL = WDTPW | WDTHOLD;

    // for i2c pins
    P1SEL = 0xC0;
    P1SEL2 = 0xC0;

    // i2c config
    UCB0CTL1 |= UCSWRST;
    UCB0CTL0 = UCMST | UCMODE_3 | UCSYNC;
    UCB0CTL1 = UCSSEL_3;
    UCB0BR0 = 12;
    UCB0BR1 = 0;
    UCB0I2CSA = 0x27;   // slave address
    UCB0CTL1 &= ~UCSWRST;

    // enable tx interrupt
    IE2 |= UCB0TXIE;
    _enable_interrupts();

    // start to transmit data
    ptxData = txData;
    UCB0CTL1 |= UCTR + UCTXSTT;

    while (1);
}

#pragma vector = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void){
    // send txData elements one by one
    UCB0TXBUF = *ptxData;
    count++;
    *ptxData++;

    // if txData ends, start from beginning
    if (count == 16) {
        count = 0;
        ptxData -= 16;
    }
}

What am I missing, can you help me?


texts:
I have a programmer and it works fine with PICKit2v2. As you see in the below images, I read my PIC16F877A memory and write to it successfully :

But the problem appears when I want to use my programmer in MPLAB-X-IDE :

As you see above, It say that The programmer could not be started : Failed to program the Device!
Why?

Contents of Project loading warning tab :

Warning: Project "FirstProject-FlashingLight" refers to file "C:\Users\Amir Ebrahim\MPLABXProjects\FirstProject-FlashingLight.X/myMain.c" that contains spaces or odd characters in its name or its path.
Some of the files in this Project "FirstProject-FlashingLight" contain spaces or odd characters in their name or their path. This could potentially cause issues during the build process. This is a limitation of GNU Make tool that we use as part of our build process. Removing spaces from all file and folder names included in this project will eliminate this potential issue.

Contents of PIC Kit2 tab :

Found PICkit 2 - Operating System Version 2.32.0
Target power detected ( 4.99V)
2015-01-01 20:40:36
PK2Error103: Unexpected device ID: Aborting as requested
PK2Error103: Unexpected device ID: Aborting as requested
Found PICkit 2 - Operating System Version 2.32.0
Target power detected ( 4.99V)
2015-01-01 20:40:57
PIC16F877A found (rev = 0x8)
Erasing Target
Programming Program Memory (0x0 - 0x7)
Programming Program Memory (0x7f8 - 0x7ff)
Verifying Program Memory (0x0 - 0x7)
Verifying Program Memory (0x7f8 - 0x7ff)
PK2Error0027: Failed verify (Address = 0x7f8 - Expected Value 0x3fff - Value Read 0xbf2)
PK2Error0027: Failed verify (Address = 0x7f8 - Expected Value 0x3fff - Value Read 0xbf2)
Found PICkit 2 - Operating System Version 2.32.0
Target power detected ( 4.99V)
2015-01-01 20:41:19
PIC16F877A found (rev = 0x8)
Erasing Target
Programming Program Memory (0x0 - 0x7)
Programming Program Memory (0x7f8 - 0x7ff)
Verifying Program Memory (0x0 - 0x7)
Verifying Program Memory (0x7f8 - 0x7ff)
PK2Error0027: Failed verify (Address = 0x7f8 - Expected Value 0x3fff - Value Read 0xbf2)
PK2Error0027: Failed verify (Address = 0x7f8 - Expected Value 0x3fff - Value Read 0xbf2)
Found PICkit 2 - Operating System Version 2.32.0
Target power detected ( 4.99V)
2015-01-01 20:43:35
PIC16F877A found (rev = 0x8)
Erasing Target
Programming Program Memory (0x0 - 0x7)
Programming Program Memory (0x7f8 - 0x7ff)
Verifying Program Memory (0x0 - 0x7)
Verifying Program Memory (0x7f8 - 0x7ff)
PK2Error0027: Failed verify (Address = 0x7f8 - Expected Value 0x3fff - Value Read 0xbf2)
PK2Error0027: Failed verify (Address = 0x7f8 - Expected Value 0x3fff - Value Read 0xbf2)
Found PICkit 2 - Operating System Version 2.32.0
Target power detected ( 4.99V)
2015-01-01 20:56:45
PIC16F877A found (rev = 0x8)
Erasing Target
Programming Program Memory (0x0 - 0x7)
Programming Program Memory (0x7f8 - 0x7ff)
Verifying Program Memory (0x0 - 0x7)
Verifying Program Memory (0x7f8 - 0x7ff)
PK2Error0027: Failed verify (Address = 0x7f8 - Expected Value 0x3fff - Value Read 0xbf2)
PK2Error0027: Failed verify (Address = 0x7f8 - Expected Value 0x3fff - Value Read 0xbf2)
Found PICkit 2 - Operating System Version 2.32.0
Target power detected ( 4.99V)
2015-01-01 20:57:42
PIC16F877A found (rev = 0x8)
Erasing Target
Programming Program Memory (0x0 - 0x7)
Programming Program Memory (0x7f8 - 0x7ff)
Verifying Program Memory (0x0 - 0x7)
Verifying Program Memory (0x7f8 - 0x7ff)
PK2Error0027: Failed verify (Address = 0x7f8 - Expected Value 0x3fff - Value Read 0xbf2)
PK2Error0027: Failed verify (Address = 0x7f8 - Expected Value 0x3fff - Value Read 0xbf2)

Note that the project that I tried to program it to my MCU, is an empty project (I mean it has only an empty main() and nothing else- I just did the primary steps to create a project as mentioned in Quick start section of MPLAB X IDE). I also tried another project that was worked fine in another computer with another reader, But I received the same error (So there is no problem with the project.)

I appreciate your time and your consideration.


texts: Connecting to a ground pour in a multi-layer pcb in eagle

texts:
I need help to understand how to connect Vias properly on multi-layer PCBs.
I created a 4 layer PCB (Top - GND - V3.3 - Bottom)
Then I created a cutout area in the copper on all 4 layers around the crystal. Then created a copper fill area for a local ground on Layer 2 (GND plane). Now I want to connect on layer 1 to the local ground plane below the crystal with a via.
The copper pour on layer 2 is named GND:

But I don't get it done properly. I tried:

Adding a via on top layer, and naming it GND, but then it connects to the ground pour on the top layer.
Adding a via on the second layer, and tried to route a wire to that via, but also this does not work as the via is then circumvented.

The grey outline is the polygon I created as a local copper fill, for the ground plane below the crystal on Layer 2. As there is no connection made yet, it does not fill.
How do I connect from the load capacitor C17 to the local ground plan on Layer 2?

I also tried starting with a trace, adding via and switching trace to layer 2 (GND) but it still does not fill the pour when hitting the ratsnest button.


texts: How do I know how many dies are contained in a certain package?

texts: For example, an IL485E that has a 16 SO(W) package -- how many dies are in the device?


texts: Find the average power dissipation of the load

texts:
I have given the following voltage and current waveforms.

I am required to find the average power dissipation of the load.

I know \$ P_{avg} = \frac {\int_0^T \mathrm{v}\mathrm{i}\,\mathrm{d}t}{T} \$

I have trouble finding the equations for the waveforms.
Please anyone help.
(Is there any other that is easier to find the average power ?)


texts:
So I watched this extremely fundamental video about voltage measurement and how it's measured. The one thing that confuses me is what people use a reference for zero potential.

The two diagrams shown below have the exact configuration and order of batteries. The values don't change either. But I get two different values of net voltage based on where I assume the zero potential to be and this assumption is arbitrary. So if I choose the zero potential to be in the middle and if my friend chooses it to be at the end, we get two different voltages and we would both be right. So what does one do to avoid such ambiguity? Is there some pre set standard on how to measure voltage? And what does a manufacturer mean when he says a supply gives a 12V or 15V output? What would the manufacturer have used as a reference? For if I change the reference point, my voltage reading for the same supply would be different and this would have consequences, right?

Edit: So what I'm doing in the first diagram is, I first connect the red lead at the top to measure 12V. I then connect the red lead to the bottom to measure -12V, getting a net voltage of 0v.


texts:
I'm trying to build a piece of hardware with an accelerometer that could track the approximate 3D position of an object. The accelerometer would not be rotating, so a gyroscope shouldn't need to be accounted for. I would like to know if anyone has any suggestions for a specific accelerometer. Does anybody have suggestions for a quality accelerometer?

Also, does the project sound doable? Could an accelerometer accurately detect the position of an object? This would all be on a small scale; specifically the tracking of one's finger. A GPS wouldn't work in this situation, as the movement would only be moved about in around a 2'x2'x2' field.

Thanks.


texts:
When I connect two USB2.0 devices to a USB3.0 HUB and that HUB to a USB3.0 capable Host computer, will link to the host computer be USB3 and thus support ~300 MBit? This would be my intuitive understanding. Or does the HUB, because it is USB2.0, somehow logically make the uplink also 2.0? Or does it depend on the hub?

I am having trouble using several USB 2.0 cameras at the same time, but I don't have USB 3.0 on the host side yet. So I'm wondering if a USB 3.0 HUB could help avoiding the bottleneck, if I have USB 3.0 on the host.


texts: What does it mean to have a pole or zero at infinity?

texts: what does it signify ? At pole/zero frequencies the response of a system goes to infinity/zero, so I think same is the case with poles/zeros at infinity, but how do these poles/zeros affect the design of system ?


texts: Background Debug Module (BDM) recommendation for HCS08 controllers wanted

texts:
I have a number of Freescale MC9S08GT32 devices I plan to use in some projects if I can find the right toolchain. Code development would be Codewarrior, which is free for up to 32K of C code.
Programmer/debugger is Background Debug Module (BDM), but this doesn't seem to be standardized; at least I couldn't find one on the Freescale website. I found the following, with varying prices:

  CNCgeeker
      PEmicro
      Softec microsystems
      Witztronics

I guess there are others. I would like to know if you have experience with certain BDMs and which type you can recommend.


texts: So i know that these following things will affect the strength of an electromagnet: Amperage going through the wire, the amount of coils of wire, and the ferromagnetic core. I also know the poles of an electromagnet are as follows: on the coil of wire the side that connects with positive is south pole, and the side that connects with negative is north pole. But can this happen, for example i take a long round piece of iron as my ferromagnetic core, and i loop some copper wire all the way to the end of the piece of iron, then i continue the loop from the start of the piece of iron to the end, and back again, and again. Will this affect the strength of the electromagnet positively or negatively as apposed to looping the wire thickly only one time but thickly?


texts:
I am reading this paper and I see that characteristic impedance does not take frequency into account. I am surprised by this as I figured different rise time signals would have different frequency content and see different impedances. Z0 is proportional to sqrt(L/C) and I figured those values change at different frequencies.
Are these characteristic impedance equations only valid for certain frequency range or am I wrong in assuming that characteristic impedance will have a frequency dependency?
https://www.polarinstruments.com/support/cits/IPC1999.pdf


texts: Symbol for SAW filter - DEA142450BT-3028A1

texts:
I wanted to create a symbol for the SAW filter to use for my project in PADS Professional Designer, but when I try to download the part through "PartQuest" it has no symbol or footprint. In the documentation I am using there is no functional diagram given, only shapes and dimensions. I need to create a symbol for this SAW filter, so I can connect it to the HMC414 amplifier, but I don't know what outputs or inputs it has, so I don't know how to do it. Could someone help me with what this symbol should look like, or how to generate it and upload it to PADS Professional Designer?
Here is the documentation for this filter:
https://product.tdk.com/info/en/documents/data_sheet/rf_bpf_dea142450bt-3028a1_en.pdf
Here is a preview of the creation of the symbol in PartQuest (since I can't choose a default one, e.g. SamacSys, because one doesn't show up):


texts:
Let's say I have two sine waves that are both DC offset to have no negative values, the measurement I want is the phase difference between these waves. When researching I've only seen detectors that give the phase difference up to 180 degrees, saying that if you want a 360 degree range you just need to figure out the quadrant. What I mean is that if the difference is outputted as 180 degree max difference, I can get a 360 range simply by telling if I am in the negative or positive range of the signal (speaking abstractly considering it's a DC biased AC waveform). However, I am at a loss as to how to do this, any help would be greatly appreciated.

This is for a laser range finding application. I am utilizing multi-frequency phase shift measurements to determine the distance. That is, I am modulating the laser by a sine wave (varying frequencies depending on the distance, all in the MHz range) and then measuring the phase difference between my modulating waveform and the waveform received by the photodiode. I have a phase comparator now that gives a 0-180 range. I can work with a 0-180 degree range except for it limits my max distance calculation to half the modulating frequency wavelength (and less precision).

Also, I am aware a 2*pi shifted waveform is indistinguishable from the original, to clarify I suppose, I just need to know the full range of phase shift within a 360 degree range.

EDIT: After some research it seems my answer is a double balanced mixer operating as a phase comparator in saturated mode (limiter). This seems to indicate that an imbalance in the dB levels of the two signals are not as important (within reason). However, the output of such a setup is still a DC output ranging from 0-180 degrees. So, hopefully the answer lies in figuring out if it is possible to adapt or add to such a mixer setup that gives me further info as to which quadrant the phase is in so I can tell if it's -180 to 0 or 0 to +180.


texts: Do datasheet specs for a dual diode refer to both diodes in series or to the individual diodes themself?

texts:
The question: With a dual diode such as the MMBD3004S (datasheet here), are the ratings such as reverse breakdown voltage specified for each diode individually, or for both the diodes combined? There don't appear to be any notes in the datasheet specifying either way although, at a guess, I'd lean towards the former. Hopefully, someone can clarify one way or the other for me.

The context: I'm designing a high-voltage flyback power supply using the LT3420, VOUT of 190V, VBAT of 5V and N of 16. As a result, the peak reverse voltage for the rectifying diode is approximately 450V by my calculation (using the equation on page 12 of the datasheet here).


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I wanna interface an old Motorola 68000-based system with an ESP32, and I was thinking of doing that through SRAM. However I can't seem to find any SRAM that I could put between them. What other options do I have?

The idea was to stick this hypothetical dual-port SRAM straight on the 68k bus and on the ESP32's external RAM interface (QSPI/OSPI).


texts: Choice of wire diameter for doll's house?

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I'm constructing a 1:12 scale doll's house and I'd like to use enamelled wire run within the walls for lighting. Each room would have its own circuit controlled through a switch and then to a common 12V supply.

Some of the lamps will be LED and some will use filament type bulbs (depending on what's available). Maximum number of lights per circuit would be something like 6 eg. 2 wall lamps, 2 ceiling lamps and perhaps a table lamp or two. They'll all be wired in parallel.

I chose solderable enamelled wire as it's single core and easy to solder to miniature fittings. There also won't be a problem with insulation shrinking back when soldering. The conductors will be lightly twisted, run in a 3mm channel cut into the MDF walls and 'back filled' with plaster.

Each circuit would be fused, perhaps 750mA? Maximum length of run might be 1 metre.

Could I get some ideas on what might be a suitable conductor size for this project? I already have some 24B&S 0.5mm dia. wire handy but can't seem to find consistent data regarding the current capacity (with information varying between 1.4A and 300mA). Something with a comfortable capacity of 1A or 1.5A maybe?

Thanks so much for your advice.


texts: Laptop failure due to constant fluctuation of AC frequency and voltage

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I spend most of time on a boat (not on holiday :/ ) where a huge generator provides electricity. The potential problem is that the output is very dependent of the "mood" of the engine. Sometimes the frequency of the AC that goes to the sockets of the cabins is 48 Hz, sometimes 52 Hz. Anyway, generally between 48-52. (EU norm 50 Hz)

My question is regarding the safety of my equipment such as notebook/laptop. My theory is that this fluctuation of frequency only harms the PSU/Charger that converts AC to DC for my laptop, therefore that will die first, before everything else. What do you guys think? Can the internal components be harmed as well, or is my theory correct? Can this harm other appliances?

Also, I am curious what kind of UPS can regulate such fluctuations into 'flat' 50 Hz (EU) and stable voltage and current?


texts: Battery power supply for Intel Compute Stick

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I have an update. It seems there are multiple posts on Intel's forum by people reporting bricked Compute Sticks even though they were using the factory power supply. I followed the recommendation to reset BIOS by holding the power button for 3 seconds and... it came back to life! That is the third Compute Stick, the one for which I was using the setup with the electronic switch. The previous two are still dead. So, it seems that these computers have some issues with power supply. And the voltage spikes damaged permanently the first two, while after fixing the voltage spike, the last one suffered from corrupted BIOS but it was possible to recover it.

I am using Intel Compute Stick, which basically is a single board computer, and I am experiencing problems powering it from a battery.

The computer is powered via a Micro USB port. It comes with a wall power supply which has 5V 3A output. I measured the actual output to be 5.16V. The maximum power consumption I measured to be 1A in my application.

Here is what my initial setup was for powering from a battery:

[16V battery] -> [5V 3A out buck converter] -> [Intel Compute Stick]

Using this setup resulted in bricking two computers. Each time, it happened while reconnecting the power supply. I hooked up an oscilloscope and observed voltage spikes when connecting the battery. To cope with this, I decided to add an electronic switch between the buck converter and the computer (Mini MOSFET Slide Switch with Reverse Voltage Protection SV from Pololu) and to make sure it is always open when connecting the battery.

So, my second setup was:

[16V battery] -> [5V 3A out buck converter] -> [MOSFET switch] -> [Intel Compute Stick]

Below are pictures from the oscilloscope, the first two are for the first setup without the switch and the rest is for the second setup. So, it all seemed to look just fine. The actual converter output is around 5.28V which is just slightly more than 5.15V and there are no voltage spikes. At this point I decided to make the final test by connecting the battery and switching the switch on until the initial welcome screen was displayed and then switching back off. I planned to try 200 such cycles, and after 130 cycles Compute Stick died...

So, I still must be doing something wrong, but have no idea what this could be at this point. As far as I can tell, all I have at this point is constant 5V power supply from the converter and I am just opening and closing the switch.

Any ideas?


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Not sure this is the place for this question, but…
I have an interest in the history of very early radio technology.  There are plenty of sources on who did what when and where, but very little on what technologies (capacitors, wire etc) Marconi,for example, had available to him.  I found some Marconi schematics in a rather obscure paper, but nothing else.  Any help out there?


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I've got a cheapo 5mW red laser module (datasheet), it looks like its got an internal regulator, probably a thermal cutoff too. I've been having problems driving it.

First thing I tried is I connected it to 5V via a resistor of varying value, (1k down to something like 200r) and the results are plain weird.

The module starts to lase at about 470r, but would be very erratic and would go off at some point. Driving it with a 200r i get a bright enough spot, but the current measures between 17mA and 21mA, voltage across the laser is 2.7v, but after a while it just cuts off like its been blown. The resistance of the laser module drops to couple of Ohms, regardless of polarity. Leaving it to "cool down" also does nothing.

Fooling around I then just tapped it on the 5V rail with no resistor, and it blinked with bright light, and started working with 470r and 200r resistors again.

Am I hitting some sort of a thermal cutoff or does the module need that minimum current/voltage to just lase, and could probably take higher voltage/current combination?

I'd like to drive it so its at its brightest point, within its rated spec.


texts: Relationship between depth of discharge and energy efficiency for a Li-Ion battery

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Consider a lithium ion battery that is continuously cycled at different depths of discharge (say, 20% vs. 40% vs. 80%) and at a constant c-rate:

It is well known that the larger depth of discharge will correspond to a faster rate of degradation for the battery. However, I wonder what the relationship is between the depth of discharge and the energy efficiency (kWh discharged divided by kWh consumed in charging). Is this expected to depend on depth of discharge? If so, are there any good references characterizing this relationship?