texts:
I was wondering which books on Cadence OrCAD (or Cadence products in general) are good for for reference use and/or have substantial focus on device modelling and simulation.

Currently I am using this book, Complete PCB Design Using OrCad Capture and Layout by Kraig Mitzner but would like to know other people's preferences.


texts: Accuracy in translating voltages to currents for shunt resistors

texts:
I apply a constant 4ma current I to a resistor R and I measure a voltage V across.
so the resistor \$ R = \dfrac{V}{I}\$.

But when I apply \$ I_2=20ma\$ to the same resistor R and I obtain the voltage \$V_2\$ then the resistor \$R= \dfrac{V_2}{I_2}\$ I expect the same.

but in first case for 4ma, I obtain 248.2 ohm and in 20ma case I obtain 248.7 ohm.

I can only measure the voltages with a daq box. If I have a device with a current loop output how can I then translate the voltages to currents, since I find different resistances for different currents? is there a way to obtain accuracy error? is there a standard for that?


texts:
I am trying to understand how to choose a suitable voltage supervisor IC for a given project. I have two questions:

if I have a digital IC, in its datasheet there is information about the minimum power supply voltage needed for proper behavior. From what the manufacturer obtained those numbers? Is it based on the statistical data to ICs made with the respective technologies? If the voltage has a lower value, what happens then - is the behavior of the IC undefined?
(related to the topic): suppose I have a digital circuit (e.g. microcontroller) for which the manufacturer specified the minimum supply voltage to be equal to 1.7V. I want to choose an external supervisor IC. The thing that I cannot understand is: how to choose the minimum voltage for which the supervisor's operation is defined? E.g. I found one for which the minimum supply voltage needed for proper behavior is 1.1V and the threshold voltage is 1.7V - I understand that within the range 1.1V - 1.7V that IC will put the microcontroller under RESET, but what if my supply falls lower than 1.1V?


texts: Boolean Network Simplification using Satisfiability Don't care Conditions

texts:
I couldn't really understand how SDC conditions are applied to minimize the following Boolean Network from Giovanni De Micheli's slide I am studying.

Given:

$$x=a'+b$$
$$y=abx + a'cx$$

Minimize \$fy\$ to obtain \$gy = ax + a'c\$


texts:
I have a USB to ethernet chip (USB 2.0 480 Mb/s)  and a microcontroller (MSP430F550x family, full-speed USB 12 Mb/s) that connects to a USB hub (USB 2.0 480 Mb/s).

How would I make these work together? Will the USB hub go at the slowest speed, which would be the microcontroller? Is there any way I can have everything work together at 480 Mb/s?

Thanks in advance for your help!


texts: How to determine the flip-flops input in truth table

texts: I've only one simple problem about JK flip-flops. The last columns in the following table (Flip-flop inputs). How were they genereted from the other parts on the left? Does this has a relationship with the equation: J Q!+K! Q?


texts: What causes my computer fan to stop briefly before resuming spinning?

texts:
I'm building a small fume extractor for soldering.

I have a leftover desktop fan I'll use. I was unsure about the voltage needed, so I hooked it up to my power supply and stepped up the voltage until it started spinning (around 6V but I think most of these fans are 9-12V nominal if I recall). It's drawing 30mA at 9V right now.

If I place my finger on it to arrest the movement the current draw drops to 0. When I release it the fan rotates quickly to some location which I assume is the armature aligning with the magnet. Now, though, it sits stationary for about 2 seconds before resuming spinning.

What's happening in those 2 seconds before it resumes spinning?


texts: SMPS with output adjustable from 0-100% - what topology?

texts:
I need a power supply with an output adjustable from 0 to 12Vcc-10A. I'm not sure if I make a 12Vcc fixed supply and then put it trought a PWM switch with a filter to adjust the amplitude,  or I try to make a supply with 110v/220vac input to 0-12Vcc (flyback or forward).

I am afraid  a single SMPS won't be able to generate an output which I can adjust from 0 to 100%.


texts: Difference between Quiescent Current & Shutdown current?

texts: What is the difference between Quiescent current & shut down current. I have searched a lot but didn't find valid answer. As per as my knowledge Quiescent current is the small current which flows when device is in inactive state. Both appears to be similar, but datasheet is provided with different set of values for both. Please let me know the difference.


texts: Why do we need zero voltage reference circuit for micro-controller?

texts:
I am designing a circuit for controlling triac firing angle. For controlling purpose i'll be needing a micro-controller. Now the confusion is why do i need zero voltage reference circuit for micro-controller? What its usage and how we can design this zero voltage reference circuit?

P.S: I am using Arduino Uno which consist of ATMEGA328P ic.
Pls answer in a layman language.
Thankyou.


texts: How do I determine the start and end of the wave?


texts: PIC16F628A Resetting after relay turned off

texts:
I am having problems with controlling a relay with load on it. I am using PIC16F628A. The problem is following: The relay has load. At first it is off. When the microcontroller's output is on, the relay turns on too. When the relay needs to be shut down, microcontroller's output is off. But when this happens, the microcontroller resets.

EDIT: The load is 220AC. Trying to control bell.

Please note that when there is no load, the relay command fully works, without resetting the microcontroller.

Here are the schematics and the PCB from the project.

P.S. The crystal footprint was changed to capacitor, because I need to draw footprint for crystal, but it has same hole dimensions as the capacitor.

EDIT2: PCB Design was updated as suggested.
The Updated Schematics & PCB:


texts:
I installed 1mm2 copper AC power cable across house for video surveillance (8 cameras, Power Consumption for each camera is Max 4W, 12V). For each camera has its own 220V->12V converter rated 3A. Total ac power cable length is about 150 meters. (In case that cameras are connected to APC Smart-UPS, I plan to plug 50" LED TV (190W) to that AC line too)

I am reading AWG specs in Wikipedia. I also read AWG Sizes and Current Limits table. Then I looked on my computer power cord.

So, 17 AWG area is 1mm2, AWG Sizes and Current Limits shows that max current is 2.9 amps. But my computer power cable is labeled that it is 0.75mm2 and max amperage is 16 amps.

So, questions:

How can it be, that a cable which is less than 1mm2 can handle
larger load than 17 AWG?
Or my computer cable has different measurement system used? Or listed 16A mean peak only?
And how can I actually calculate max cable load by cable area (mm2)?
Or AWG Sizes and Current Limits table is wrong?
General question - Will the installed 1mm2 cable be good enough for that load?


texts:
I am using 3 AA batteries of 1.5V each, to obtain a voltage of 4.5V which i am then reducing to 3.3V using a LDO. My current requirement is around 100mA.

I want a simple, low power dissipation circuit which would be connected to the arduino to monitor this battery level

Previously for one of my projects I have used a simple zener diode to monitor the battery level. However I didn't take into account the heat dissipation, reliability etc.

So, can I know what are the different types of options available?
My main constraints are:-
1)Circuit should be simple
2)Low power dissipation

I am attaching the pics of my entire circuit and the zener circuit which i used before.]2

To provide a bit of background of the zener circuit, I first calibrate it for my application, then I am able to view the percentage of battery at the display.


texts: Schematic shows two outputs for Vout. Why?

texts:
How do I interpret the fact that Vout has two output points? My guess is that the two Vout points represent where I would place the probes on a multimeter. Is this correct?

See this diagram:

The article I'm reading suggests that there is only one signal for Vout, which looks like this:

I'm really sorry for if this a basic question, I'm new.


texts: Write received character from PS/2 keyboard to LCD1602

texts:
I am trying to read a pressed key from a PS/2 keyboard and display it on a LCD1602 display. I wrote one entity and architecture which detects a pressed key. If it received the 11 bits (1 start bit, 8 data bits, 1 parity bit and 1 stop bit) then I write the received 11 bits to a signal. This is a code snippet that does that job

process(KCI)
    variable IDX : integer range 0 to 11;
begin
    if(falling_edge(KCI)) then
        if(IDLE = '1') then
            IDX := 0;
        else
            MSG_BFR(IDX) <= KDI;
            IDX := IDX + 1;
            if(IDX = 11) then
                IDX := 0;
                MSG_RCV <= MSG_BFR;
            end if;
        end if;
    end if;
end process;

On a Keyboard Clock Input (KCI) it reads the Keyboard Data in (KDI) and writes it in a Message Buffer (MSG_BFR). Once received all 11 bits it writes to that signal Message Received (MSG_RCV).

Another process in this keyboard architecture writes it to a signal which is port mapped to the 'main' VHDL code.

process(MSG_RCV)
begin
    KEY <= MSG_RCV(8 downto 1);
end process;

The 'main' VHDL code just passes this information via a port map to the LCD1602 code using a simple process

process(KEY_M)
begin
    CHAR_M <= KEY_M;
end process;

The LCD1602 writes the character in an array using this process

process(CHAR)
    variable ARRAY_IDX : integer range 7 to 14 := 7;
begin
    if(CHAR = "01000010") then
        LCD_CMD(ARRAY_IDX)(7 downto 0) <= CHAR;
        ARRAY_IDX := ARRAY_IDX + 1;
        if(ARRAY_IDX = 14) then
            ARRAY_IDX := 7;
        end if;
    end if;
end process;

This actually writes only the character K in array at a specific index.

Parallel to this function is the code also reading from this array and writing the bytes from this array to the LCD1602 screen.
Running this code actually writes just a character B in all the places in the array.

The code that writes the bytes to the LCD1602 can be seen below

    process(CLK1602)
    variable i : integer := 0;
    variable j : integer := 1;

begin
    if CLK1602'event and CLK1602 = '1' then

        if i <= 1000000 then
            i := i + 1;
            E1602 <= '1';
            DATA1602 <= LCD_CMD(j)(7 downto 0);
        elsif i > 1000000 and i < 2000000 then
            i := i + 1;
            E1602 <= '0';
        elsif i = 2000000 then
            j := j + 1;
            i := 0;
        end if;

        if j <= 5  then
            RS1602 <= '0';    --command signal
        elsif j > 5   then
            RS1602 <= '1';   --data signal
        end if;

        if j = 37 then  --repeated display of data
            j := 5;
        end if;

    end if;

end process;

I have been stuck on this problem for 3 days now. All I want is to write a pressed character to the LCD and increment the array index by one, so the next pressed character can be written to that location.
Can anyone point me to the source of the problem, which is why I do not get the desired behavior?


texts: Dual antiphase electret mic preamp topology

texts:
I am currently trying to make a preamp for an electret mic pair, which are placed physically in antiphase. The main idea is to subtract one mic's signal from another and therefore boost the signal amplitude while reducing the noise.

Caution: in the schematics below the nominals of resistors and capacitors are totally wrong, only the topology of preamp is what matters. The FETs in all schematics are just the FETs that are included in the electret mics.

A typical solution for this would be using a differential amp (number 4 on pic). However, I am not sure if this solution is good enough and if it is better to pre-amp the signal of each mic individually before subtraction. For a single-mic preamp I have found three solutions on the internet (see number 1-3 on pic): a simple non-inverting amp (1), a transimpedance amp (2) and a weird schematic which implies getting rid of the DC offset by precisely calibrating the R8 resistor, not by using a capacitor (3).

My question: should I subtract the microphones' signals immediately (using a differential preamp) or after some basic amplification and if the second option is preferable, which one of the preamp topologies (1-3) should I use? What are the pros and cons of each approach?


texts: My electric fence zap box surrounding my bee yard stopped working. When I took the box apart I noticed a burnt spot on this capacitor.  The only numbers I can see on this part is E 103M AKV. What does this label mean? Thanks for the help in advance.


texts:
Few days ago I had topic about issue with power inductor crashing circuit. I almost resolved issue without making new by 90%. However sometimes circuit crashes -> I did some updates based on replies.

Goal: Li-ion battery powered circuit that powers ESP32 & LED strip (total top 1,75A 5V). PCB are splitted into two parts - battery & battery protection circuit / chip & connectors. Part 1 with battery should work, anyway included. Can you give me some advices if I am still wrong? Definitely would like to say with same form factor :)

Components:

Li-Ion battery
Protection circuit
Step-up to 5V 2A (MT3608, power inductor)
ESP32
LED strip

Old layout

Battery scheme (do you need layout?)

Scheme main board

New layout


texts: Drift with Madgwick algorithm with fast movements

texts:
I am trying to correctly track orientation of a sensor with accelerometer and gyroscope using the open source Madgwick algorithm. The algorithm returns quaternions which represent the rotation between the internal and external frames and I use it to determine gravity vector to correct accelerometers.
The algorithm works well when movements are slow and static, but when I try to excite the sensors with fast and periodic movements the quaternions always end up drifting. You can see below the representative figure of this drift when a back and forth movement from top to bottom is performed, the drift is observed on gravity vectors calculated with the quaternions obtained by the fusion algorithm.
(Blue = X axis, Red = Y axis and Yellow = Z axis)

The IMU is a low-cost one : Invensense ICM20948, my sample rate is good (about 300 Hz 100 Hz), I have smooth quaternions, and set parameters algorithm to have good result with slow and static movements.
So my question is : Do you think it's possible to have good result with Madgwick algorithm when this kind of movements are performed? (fast and periodic).


texts: Delay on 12v sort of debouncing circuit?

texts: OK - - i have an opto sensor that runs on 12v (5-30 actually) and that is power by a battery/charge regulator/ 19v power supply and is used for counting how many times somebody goes past it on a site entrance ... HOWEVER .. the counter is sensitive ... and between the opto sensor and the counter you could flap your hand in fromt of it and count upto 20 in a heart beat ... SO  .. id like to limit the amount of inputs the counter receives to 1 every couple of seconds .. even a minute would do ... the pin on the counter ( an 7111hv ) just takes a high input ... the opto sensor (baumer i think) outputs an 11v high on one of its wires when the beam is broken ... but its all fairly low current and im trying not to use relays as i, trying to put the new circuit somewhere on the cable that supplies the opto sensor and id like to keep it from drawing too much current ... anyway ... the opto sensor has 3 wires ... 12v pos and neg plus signal wire ... so in my mind i need a delay on circuit that effectively 'debounces' multiple inputs into one single high so that the counter just sees one 11v signal of whatever length so that it just registers 1 not 2 million :) ... any thoughts ?


texts: Oscillating frequency of ring oscillator

texts:
I am a bit confused about the operating frequency calculation of ring oscillator.
Below is an excerpt from this PLL tutorial.

  Each stage provides pi/n phase shift and so it requires two passes
  through the ring to acquire the necessary 2pi radian phase shift.

Does this mean that DC phase shift (inversion) is not taken into account here?
At the oscillating frequency, each stage provides a phase of pi + pi/n. So after n stages the total phase shift will be n*pi + pi that is equivalent to zero phase shift if n is an odd number.
I don't see how the signal passes two times here. Could anyone explain more?


texts: IEEE 754 standard and C language float data type

texts: Is IEEE single precision floating point numbers equal to the float data type numbers in C language. Is there a way to check this


texts: Triac Circuit Won't Fire With Small Loads

texts:
I made a pcb with a number of optoisolated triac circuits to control various 120vac components, like pumps and valves. The circuits work, but not for 2 components. The circuit will fire for really low amperage valves (0.04 amps), and higher amperage components (> 0.6 amps), but it won't fire for valves that draw ~0.25 amps. After troubleshooting, I found that if I wire in another small load (0.04 amps) in parallel with the problem valve, the valve and second load both work.

What's happening? How can I fix this and just run the problem valve without a second load in parallel?


texts:
I need to find a op-amp that will handle the high input voltages that my circuit requires.  I'm not real familiar with them and not sure how to read their datasheets.  I do have a LM741 but it looks like it can only handle +/- 15v.  I need at least +/- 60v I think, but I have include the schematic that I used to test with.  U1 is just LTSpice's ideal single-pole op-amp.  Any suggestions on a particular op-amp or what I need to be looking for would be greatly appreciated.

Edit

I'm trying to use Vout to turn on the gate of a PMOS which is switching a variable voltage from a boost converter.  V2 will come from boost converter and V1 will be what I subtracting from V2 so that the PMOS will cut on.  The PMOS will be on when Source = Vout and off when Source = Source.  The second schematic is the boost converter and the current configuration which uses a voltage divider to control the gate voltage, but I'm concerned that PMOS will not turn all the way on when the voltage is lowered all the way to 12v.  I think that Vgs will just be to small using a voltage divider.

M2 is the PMOS
M3 is a NMOS used to control the voltage divider.
The two signals will be coming from Micro Controller.

http://imageshack.us/a/img22/4678/g16a.png


texts: Electrical noise resets & chattering in relay modules using ESP8266

texts:
I am trying to build my own SONOFF like device by using a Wemos D1 mini and associated circuitry. I am facing an issue with electrical noise where whenever switching of the relay causes chattering behavior in my circuit. The issue does not happen always but happens mostly. I have built several circuits with ESP 12E , ESP 01 , WEMOS D1 mini and all of them exhibit some kind of erratic behavior.
I may not be able to explain all kinds of noisy behaviors I have seen but it has mostly been that when switching a relay, it switches ON and OFF multiple times or the second switch is triggered by the first one.
I have done the following to either debug this or avoid this by:

I have put a low pass filter on the input pins if noise at those pins may be causing this. This has had no effect
I have replaced the 230V-5V module by a DC source to rule out interference from it - this has had no effect.
I am using pre-built active LOW relay modules which I drive via a PC817 optocoupler to isolate the WEMOS with the relay but it has no effect.
I have tried measuring the noise but I dont have a Oscilloscope to be able to see it. I have not been able to figure out if the noise is at the input or output PIN.
The issue has no relation to the firmware on the ESP. I have had my own code , TASMOTA & ESPURNA frameworks, I am able to get a varying level of erratic behavior with all of them. TASMOTA device reboots when that happens while ESPURNA device switches ON and OFF several times or triggers the other relay.
Also, if I disconnect the load form the relay and operate them the issue almost does not happen. The relay works just fine. So only when I connect the load (which is a fan or LED down lights) the chatter happens.

I have attached photos of the module I have built to enable somebody to point out some glaring issue but as I have made several modules in different configurations, I think that might not be an issue but open to hear if I am missing something there.
I have also attached a circuit diagram of the whole circuit which it is based upon.
Any ideas on how I can debug the issue more would be helpful. Thanks


texts: I’ve recently discovered the use of SLA batteries for my boat but know nothing about them. I have a full size 12 volt digital smart charger which I can set as low as 2 amp. It automatically shuts down and cycles when the battery is charged. It works great on my flooded 12 volt batteries. Can I use this charger on SLA 12 V, 9 Ah batteries?


texts: What limits length of wire connecting audio amplifier to speaker?

texts: Let's say I have LM386 or some other audio amplifier. What determines the length, resistance, capacitance and inductance (if L C parameters matter) of the conductor that carries the output of the audio amplifier to the speaker?


texts: Looking for a connector with only images to go on

texts:
I'm trying to find the connector used for my vehicle's accelerator pedal.

Are there any strategies for finding connectors like this?


texts: "104" caps testing as 50-60 nF and their use as decoupling caps

texts:
I have a bag of capacitors labeled "104." (I don't recall their origin; probably an old AliExpress order.) However, they all test, on both my multimeter (a UNI-T UT61E) and a little microcontroller-based tester, as between 50 and 65 nF. I have another (clearly different in both colour and shape) "104" cap from another source that does test at around 93 nF, which makes me believe that I am testing them properly. (I do short the leads for a moment before checking the value.) But perhaps I'm not; am I missing anything here?

In case it helps, here's a picture of the caps in question: the two brown ones on the left are the seemingly 56 nF caps (front and back), and the one on the right is the actually-100 nF cap.

If I am measuring the value right, are these caps damaged in some way or just mislabeled. If the latter, is this sort of mislabeling common when buying jellybean parts?

I no doubt bought these as decoupling caps for things like old 8-bit CPUs and their peripheral chips. What should I do with these?

Use a pair of them at each decoupling location to get the seemingly-standard 0.1 μf decoupling value.
Just use a single one because 50-60 nF will work fine? (They do seem effective at cleaning up, e.g. a 1 MHz waveforms when I check on my oscilloscope.)
Not use them at all because they're too dodgy?


texts: Generating plus and minus voltages for op amp

texts:
I have what is probably a simple question. I have googled it, but the answer doesn't make sense to me.

I am learning about op-amps and creating all sorts of circuits with my nice cheap 10cent op amps. I always power these from my lab supply using +/- 5V or 15V and it works great on the solderless breadboard. Creating simple things such as simple multivibrators and so forth which would only cost a few cents.

Now I start to wonder how to power such devices from a single DC power supply, such as a 5V wall wart of which I have many lying around.

Here is what I've found.

OPTION 1:

Use a "rail splitter" such as TLE2426. But the cheapest one I can find on digikey in thru-hole form is $1.83 (qty=1). Really? More than ten times the rest of my bill of materials (1 op-amp plus a few resistors and capacitors to make a multivibrator, for instance).

OPTION 2:

Use another op-amp as shown in "Virtual Ground" section of this page:
http://www.swarthmore.edu/NatSci/echeeve1/Ref/SingleSupply/SingleSupply.html

OPTION 3:

I read somewhere online that you can buy single-supply op-amps. I searched digikey but failed to find one. It has a column called "Vsupply single/dual" but all the ones I clicked on, when I went to the datasheet, the numbers quoted in that column were the dual +/- voltages.

Conclusion

Note that for small one-off circuits I don't care about paying $2 for a solution, but surely Option 2 is not the only other solution? If so, then from now on I will only buy dual-style (two-per-package) op-amps, since it seems you always need one to create the virtual ground for the other. Surely that is not the only solution?

Furthermore, Option 2 can't supply much current, I think -- does that mean it won't work in some instances? In which instances will I run in to problems with Option 2?


texts:
So I accidentally burnt a PCB trace and I'm trying to fix it with a wire + some solder. The PCB trace clearly connects two metal pins.

My question is, would it be better to completely bypass the trace and solder the wire from one pin to another?
Or to solder the wire from the good part of the trace, over the burnt part, to the other side of burnt part (so still using the good parts of the trace)?

I don't have that many materials, so I can't really do any fancy repairs.

Thanks!


texts: Difference between internal and external oscillator for a microcontroller?

texts:
I am a beginner with respect to microcontrollers, so I just want to ask is there two option for choosing the frequency of the microcontroller: to be internal or external?

If there is internal frequency available in the controller, then we don't need to use external crystal oscillator?


texts: A relay that can switch from one source to another - what's that called?

texts:
I want to be able to use a microcontroller to select the power source, from among two, for a 100A DC application.

All the relays I see are ON / OFF, rather than a selector.

So, I'm looking for something with 5 connections:

Signal input (say, 3.3v digital, which when activated causes it to "switch")
Power input 1 (which I'll connect to a battery bank)
Power input 2 (which I'll connect to an AC Adapter)
Power output (which I'll connect to the load)
Common ground (for the voltage of the signal input)

I'm probably not searching for the correct piece of equipment, but I can't seem to determine what this might be called.


texts: Is it possible to use cascaded 1 bit magnitude comparators to create an n bit magnitude comparator?

texts:
I know it is possible to use 4 bit comparators to create N bit comparators as shown in this Data Sheet

http://www.ti.com/lit/ds/symlink/sn54s85.pdf

but is it possible to do it with 1 bit comparators?


texts: How to find the problem of this old Marantz amplifier?

texts:
After a first question referring to resistor symbols, I'm back with this old Marantz PM-68 class AB amplifier and I will refer to components using their ID that can be found in the service manual.

When a friend gave me this amp, it was partially working. The sound wasn't bad, but random very loud explosion noises came out of the speakers every few minutes.

It eventually stopped working and I want to repair it. I changed all the main board's capacitors because some of the old ones were leaking. Some fuse resistors (3295-3298) were also blown out (maybe because of spikes when the explosion noises occurred), so I changed them too.

The left channel is now working great, I checked it by injecting sine waves on the input, and the output sines look beautiful! The power lines (+56V and -56V) are stable for both channels.

The problem is the right channel. After hours of debugging with my scope and multimeter, I'm left clueless. There is serious clipping on the bottom half of the sine wave. The bottom of the sine doesn't even exist! I checked all the resistors, diodes, solders (i found a few solders which had dried and were broken, so I fixed them). One of the transistors used for the bottom part of the sine doesn't feel as hot as the others when I touch it after a few minutes, and it's barely warm (7266). When I desolder it and use the one from the left channel, the same problem occurs, so it's not the transistor.

When I check the signal by putting my two scope probes on each side of the 2268 capacitor, I get very nice sine waves when the speaker is disconnected. But as soon as I plug in the speaker, the bottom half of the sine gets clipped.

What would you check in that situation? Can you think of something I could've missed?

Here is the difference between left (yellow) and right (blue) channels at ~33% volume:

Here is the difference between left (yellow) and right (blue) channels at ~10% volume:

Here is the signal I get on both sides of 2268 when no speaker is plugged in (my input is 283Hz):

Here is the one I get on both sides of 2268 when I connect a speaker to the right channel:

Here is the warm transistor (7266). I tried switching it with 7265 to no avail:

Here is the schematic of the right channel:

Here is a close-up view with the measured values under a small load (<10% volume potentiometer):

I tried to swap transistors 7258 and 7260. I also replaced resistor 3274 and diode 6256 with brand new ones.

This is the signal at the base of transistor 7264:


texts:
I'm using the mbed TCP/IP Socket library to receive incoming messages via ethernet. Currently, the incoming data is read in an infinite while(1) loop (i.e. as fast as possible).

I will also be adding several timer interrupt functions which run periodically (1000/sec). Should an interrupt occur while a message is being received, would the incoming message be discarded and have to be re-sent from the client?

How are packets processed in the LPC1768? If I process incoming packages in a separate timer interrupt function (say, 20/sec), can I still guarantee that packets won't be missed?


texts: VHDL to store only unique elements in an array

texts:
I want my component to receive data, and store it into an array, only if it isn't already in the array. Should be simple right?

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

entity repetition is
  port(
    data_in: in unsigned(6 downto 0);
    start  : in std_logic;
    output  : out unsigned(6 downto 0));
end entity;

architecture arh of repetition is
signal i: integer := 0;
type niz is array (6 downto 0) of unsigned(6 downto 0);
signal niz1: niz;
signal repeat: std_logic := '0';
begin
process(start, repeat)
variable ind : std_logic := '0';
begin
if( to_integer(data_in) < 100) then
    if (start='0' or repeat = '1') then

        for j in 0 to 6 loop
            if(j<i) then
                if(data_in = niz1(j)) then
                    ind := '1';
                end if;
            end if;
        end loop;
        if (ind = '0') then
            niz1(i)<=data_in;
            i<=i+1;
            output<=data_in;
            repeat <= '0';
        else
            repeat <= '1';
        end if;
    end if;
end if;
end process;
end arh;

i is an integer which tells us how far we have gottent into an array (of length 7), repeat is in the process sensitivity list, used to restart the process if an element is already present in the array and output outputs the newest unique input. When I run this, output is all 0s.

The thing that's really interesting is if I put if(ind = '1'), it takes the branch always, i.e., I believe it is somehow in advance updating i and the array, before the loop finishes, so it always finds that data it checks for is in the array.

How do I correct this?


texts: Is the information in MODBUS function code 16 redundant?

texts:
MODBUS function code 16 is "Write Holding Registers". The function command structure is:

Address (1 byte)
Function code (1 byte)
First register address (2 bytes)
Number of registers to write (2 bytes)
Number of bytes to follow (1 byte)
Data (N bytes)
CRC (2 bytes)

If registers are always 2 bytes long, then aren't the number of registers and number of bytes redundant pieces of information? Under what circumstances would

number of bytes = number of registers * 2

not be true?

If I were to receive a command where this was not the case, should I reject the command?


texts:
I have a MAX7221 SPI 7-seg. LED driver linked to an AVR168P microcontroller.

Sometimes when powering on, everything works as expected. Other times the display blanks and remains blank. Other times the display illuminates all digits and remains "stuck" like that.

Can anyone give me any pointers as to what I could try to fix this?

(The 10K pull-up on CS is off-board - closer to the uC)

My code:

.MACRO spiDeselect
    SBI PORTB, pinCS3
    SBI PORTB, pinCS2
    SBI PORTB, pinCS1
.ENDMACRO

.MACRO spiSelect2
    SBI PORTB, pinCS3
    SBI PORTB, pinCS1
    CBI PORTB, pinCS2
.ENDMACRO

.MACRO spiOut ; value in portReg
    OUT SPDR0, portReg
spiOutWait:
    IN portReg, SPSR0 ; Can't use SBIS for port > 31
    ANDI portReg, (1 << SPIF0)
    BREQ spiOutWait
.ENDMACRO

.MACRO setupSpi
    ; Prevent SlaveSelect acting as an input
    ; or it'll force SPI into slave mode
    LDI portReg, (1 << pinSS) | (1 << pinCS1) | (1 << pinCS2) | (1 << pinCS3) | (1 << pinBlink)
    OUT DDRB, portReg
    SBI PORTB, pinSS
    SBI PORTB, pinBlink
    LDI portReg, (1 << SPE0) | ( 1 << MSTR0 ) ;| spiDivide128
    OUT SPCR0, portReg
    ; Setup SCK and MOSI pins AFTER enabling SPI, to avoid
    ; accidentally clocking in a single bit
    SBI DDRB, pinMOSI
    SBI DDRB, pinSCK
    spiDeselect
.ENDMACRO

.MACRO max7221SetRegister
    spiSelect2
    MOV portReg, regReg ; MAX7221 register to set
    spiOut
    MOV portReg, valReg ; value to set
    spiOut
    spiDeselect
.ENDMACRO

.EQU Max7221RegisterDecodeMode=0x09
.EQU Max7221RegisterIntensity=0x0A
.EQU Max7221RegisterScanLimit=0x0B

.MACRO setupMax7221
    LDI valReg, 0
    LDI regReg, Max7221RegisterDecodeMode
    max7221SetRegister
    LDI valReg, 0x2
    LDI regReg, Max7221RegisterIntensity
    max7221SetRegister
    LDI regReg, Max7221RegisterScanLimit
    LDI valReg, 7 ; display 8 digits
    max7221SetRegister
    LDI regReg, Max7221RegisterShutdown
    LDI valReg, 1 ; shutdown mode = 0
    max7221SetRegister
.ENDMACRO

progStart:
    CLI
    setupStackAndReg
    setupSpi
    setupMax7221
................

Thanks.


texts: Effects of using voltmeter w/ 20 kΩ impedance across 35 kΩ resistor?

texts:
Our professor assigned the following question:

  Describe both quantitatively and qualitatively the effects of using a
  voltmeter to measure the voltage across a 35 kΩ resistor if the
  voltmeter has an input impedance of 20 kΩ. Assume the 35 kΩ resistor
  is in series with another 35 kΩ resistor.

All I know from the reading and lecture is that your voltmeter needs to have a much higher impedance/resistance than the circuit resistance in order to avoid the meter loading effect, which causes instrument misreadings. How MUCH higher impedance/resistance does the voltmeter need to have in relation to the circuit resistance? I don't know how to do the math (the "quantitative" part). Is what I said sufficient enough for a "qualitative" explanation?

I emailed my professor yesterday morning. He never got back to me, and this was due last night.

EDIT:

Here's what I tried to work out...Using 10V as the Voltage from the Voltage Source, I figured out that the Voltage Drop across each resistor should be 5V when everything is in series. But I don't know what to do when the voltmeter is attached to a resistor. Do I calculate everything as if it's all a parallel circuit now? Is only R1 and VM1 part of a parallel circuit, whereas R2 is still only part of a series circuit?

The answer key says:

  Quantitatively: If the applied voltage is 10 Volts, you should measure
  5.0 Volts across each resistor, but you actually would measure 2.667 Volts

I need to know how he got 2.667V in his example...


texts: Powering the load while charging 3s 18650 battery with BMS balance charger PCB

texts:
I want to charge use this battery management system (BMS) balance charging board for charging and management of a 3s 18650 battery. The load and charging port is connected in parallel with power port of the BMS board. Can I power the load while charging the batteries?
Circuit diagram:

Datasheet of the module


texts: KiCad help for differential pair routing and silk screen layer

texts:
I am just routing a differential pair signal for USB 2.0 with 90 ohm impedance with the KiCad differential pair router. For that I have defined DP width as 9 mills and DP spacing as 8 mills for 4 layer baord taking reference from JLCPCB site.

In the above picture I have routed the signal to the TPD2E009DBZR IC in which 1 pin is still left for connection to ground. Now it doesn't have space for routing the 3rd pin.  How can I route that ground signal? I am sure I am missing something very common.
Second I am designing a PCB which contains more then 150 components. Consider a resistance for the instance for which I have defined 3 fields reference, value and MPN in schematic editor. When I shift to PCB Editor every resistance’s ref and value are visible (don’t know why MPN is not) on the silkscreen layer. The same problem is for all the components. Is there a way  I can control that only reference for components are visible on F.Silkscreen?
PS: I am beginner to high speed design.


texts: Locked rotor current rating vs magnetization current

texts: Is the locked current rating of a motor the highest current I should expect when starting a motor?  Is the locked rotor current rating the same as magnetization current? If not then how should the magnetization current be considered when selecting motor protection?


texts: ADS8671 ADC: 1 MSPS, but 15 kHz antialising filter?

texts:
Looking at the datasheet for the TI ADS8671, it says this device can do 1 MSPS (one million samples per second, right?)

I would think this would allow sampling of theoretically up to 500 kHz, in practice a little less for the antialising filter.

But on page 25, it shows the frequency response of the integrated antialising filter well below that:

So for 1 MSPS I get a flat passband only up to 15 kHz? Can that be right?

Further confusing to me is this datasheet describes two ADCs, one with 1 MSPS and another 500 kSPS, yet describes only one filter. And it says the "filter is typically set to 15 kHz". Does "typically set" imply the filter is programmable? I see no such capability in the datasheet.

What am I missing?


texts: STM8L discovery board, wires for the breadboard

texts:
I don't know if it is the right place to ask, but still

I have a STM8L discovery dev board - http://www.st.com/web/catalog/tools/FM116/SC959/SS1673/PF250636

which has very small square male-type pins. Of what I can measure, it is around 0.025" (or 0.64 mm), if to assume that the size is from default size range.

Now my question is - where could I get a proper set of M/F (female-to-male) wires of that size, because I need to connect this dev-board to my breadboard, and the breadboard itself has pretty much the same size (0.025" or 0.64mm) female pins.

Can someone help me ?


texts: Shunt capacitance in applications not involving photo diodes

texts:
I have read a lot of articles about how to determine the correct feedback compensation capacitors capacitance in transimpedance amplifier circuits, but they "all" use the photodiode as an example.

When using the photo diode as an example when calculating the feedback capacitors value and the cut-off frequency the photo diodes shunt capacitance is used. I understand that the electrical equivalent model of the photo diode is often modeled with a shunt capacitance and that this is often in the few hundred to thousands of picofarad range.

My question is:

If I replace the photo diode with a circuit like the one shown below, where the range of the capacitor value is about 50nF to 50pF, how much would the equivalent shunt capacitance be?

Is it zero?

simulate this circuit – Schematic created using CircuitLab


texts:
I have a 500w dc motor that I want to brake with a power resistor. Using ohm's law I can calculate the resistance needed like so

R = V^2 / P = 36^2 / 500 = ~2.5 Ohm

Building it in real life I'm going to use resistors in parallel rated for 100W, where I'm aware that I probably need less than that but just to be on the safe side I'll use 5 of.

I was wondering though, what would happen if I used less resistance, say 5 x 0.01 Ohm in parallel?


texts: Complete ADC SNR formula when signal is not full scale

texts:
I am very in pain to find a (any) paper giving more than the traditional SNR for full-scale wave sampled by ADC
$$ SNR(Full Scale Waveform) = 6.02N + 1.76 (dB)$$
As far as I can remember if the signal if not full-scale there is an additional negative term in the form of 20log(V/Vfs)
$$ SNR(V) =?  20log(V/Vfs) + 6.02N +1.76 (dB)$$

Is this last equation true ?

Why is it not often shown/written (circuits without Automatic Gain Control are not so rare, leading to small waveform sampling)

Is there an open source document exposing this issue ?


texts: How are these "Programmable Oscillators" programmed?

texts:
I came across the SiTIME SiT8008B field programmable oscillators and their programming device.

What I can't seem to find is an explanation of what the programmer is doing to the "blanks" to set them. Also curious if there's a way to program them without the manufacturer's device, or if that would be ridiculous?


texts:
Background

I saw this video on youtube where this guy adds a marker to his analog oscilloscope by sending a pulse to the z axis input:
https://www.youtube.com/watch?v=QCFBBiIm1h0

I want to do the same thing with my Tektronix 2213, but I want the cursors to be calibrated.

The two signals my system will deal with are A-GATE and the Z-AXIS input.

A-GATE is a positive going pulse that  is high from the start of the horizontal sweep to the end. Its width represents the width of the oscilloscope screen.

The Z-AXIS input controls the brightness of the trace. A pulse at the right time will produce a bright dot on the trace.

The timing of A-GATE is generated by timing capacitors. There is no clock to synchronize to.

My plan is to:

Measure the width of A-GATE with a timer.
Read a rotary encoder. The value will be some fraction D of the full scale value.
Calculate a new pulse width by multiplying the width of A-GATE by D. This new width is labeled as Delay in the diagram below and is set by the rotary encoder.
Set a PWM to the calculated pulse width. The rising edge of the PWM should be synchronous with the rising edge of A-GATE.
Generate a narrow pulse on the falling edge of the PWM that will drive the Z-AXIS input.

The 2213 doesn't have an A-gate output, but let's ignore that (the plan is to carefully open up the case, and get a buffered version of A-GATE through a pass-through in the case).

My first attempt will be a proof of concept with readily available parts. I will likely have to go to faster MCUs and components for good accuracy on the faster horizontal time scales.

The Z-AXIS pulse will have to be proportional to the horizontal time scale e.g. 1/100th of the screen width, but I think I can handle that. I'm thinking of a few astable pulse generators feeding into a mux.

Questions

Should I use a PIC and program it in assembly for reliable timing? I think PICs do 1 instruction/clock.
How do I synchronize the rising edge of the PWM with the rising edge of A-GATE? I am thinking I should use A-GATE as an input to a PLL to generate the clock for my MCU to synchronize the MCU to the scope.
The timing of A-GATE will change with different horizontal time scales. If I generate the clock from A-GATE, Would an MCU be bothered by its clock changing? I realize I will need extra circuitry to figure out what time scale I am on.
Does this plan have any major problems I should look out for?

Any other tips are appreciated.

Meta

I am doing this for fun - I know it would be easier to buy a cheap DSO with cursors.

This is my first system design question on the site. I checked the help section already. Let me know if this question is not appropriate for EE SE.

Most of my experience is with analog circuits. Dumbed-down MCU explanations are greatly appreciated.

Thanks!


texts: Does the current in adjustable voltage regulators changes?

texts:
I'm looking for voltage regulator which gives an output voltage of 3.5V and output current of 3A. I found one adjustable voltage regulator MIC69301/2/3 which says, it gives 3A output current and support currents of 1A, 1.5A, 3A, 5A with an input voltage range of 1.65V - 5.5V.
Does it mean that giving any current value as input at specified voltage to the voltage regulator, give the fixed output current of 3A and desired output voltage based on the voltage divider circuit at the output.
Does the voltage divider circuit has no affect on the output current?


texts: Is base-emitter voltage of BJT transistor (common emitter configuration) constant?

texts:
For sillicon the value of Vbe is approximately 0.7 V. So why is the input characteristics of such a transistor like this

Why not a straight vertical line. Or is this curve plotted for I Vs Vbb. I have seen nowhere plotting this curve against Vbb.
So what is wrong here?


texts: Need 12VDC power - only when ignition key is in lock (OFF)

texts:
I currently have a flashing LED that works on 12VDC power.
This LED will be used as a pseudo (imitation alarm) deterrent in our family vehicle.
However, I only wish to have the LED receiving 12V when the ignition is in the LOCK (OFF) position, and 0V when the ignition key is moved to other positions.  Hope this makes sense?
I understand this could be achieved using a relay, but I'm not sure how this circuit would need to be wired in order to achieve the desired result?
Any help (with diagrams) would be sincerely appreciated.


texts: How to detect load is connected to a MOSFET?

texts:
How can I detect a load is connected to a MOSFET and report that back to the MCU?
So the MOSFET can be ON or OFF, but I need to know in both situations if there's something connected or not.
NOTE: if it involves an additional GPIO, then id like to add an indicator LED instead.

simulate this circuit – Schematic created using CircuitLab


texts: A question about generating low frequency sine waves by a soundcard

texts:
As a part of a bigger experiment I need to control the frequency of a speaker by a PC through a MOSFET amplifier. The rest is someone else will use that speaker output for some mechanical application to push air pressure ect. I need to deal with the electrical part.

Here is the power MOSFET amplifier's input output ports:

Currently a manual function generator(set to 2Hz 2Vrms currently) is coupled to the sym input. I guess this sym is in line level.

Unfortunately I couldn't find the datasheet of the above MOSFET amplifier since it is bit old one.

My freq of interest for sine wave generation is from 0.1Hz to 200Hz. As you see in the below figures a MOSFET amplifier is powering  8 0hm speaker. I also need to monitor the frequency going into the power amplifier by a DAQ or scope.

So far I tried the system in Figure 2 below:

Regarding Figure 2:
From a PC software like Python, I can control the PWM output of Arduino then to an active filter which converts the PWM to a constant voltage. And an old obsolete part VCO(ICL8038 ) converts the voltage to frequency. I have some problems with this. One is one cannot set the frequency very precisely because the PWM has 255 step resolution. ICL8038 sine output is a bit deformed at low frequencies. And also it is not possible to set a single cap which can give a range of 0.1Hz to 200Hz(One needs to change the cap for this range).

So I thought maybe it is not necessary to use all of these. I thought the system in Figure 1 can be used. I mean directly coupling the audio output(I guess it is line level) of the PC to the amplifier's line input(maybe through a buffer of an amplifier).

My questions are:

1-) Do you think I can generate better sine waves comparing to ICL8038 for the range from 0.1Hz to 100Hz by using the soundcard of the PC?

2-) In that case(Figure 1), would I need a buffer or an amp between the power MOSFET and the PC audio port? Basically for the Figure 1, do I need another interface?

(I also read about DDS Synthesizers, but maybe I might not need that for this application if the PC sound card would suffice)


texts: What does it mean if an AC motor has two voltage ratings?

texts: On my AC motor nameplate, it says V230/400 (delta/star). I imagine this means that it is compatible with both voltages, but what allows it to do this? How will the performance change for each?


texts: Will I have better debugging performance by using an external debugger?

texts:
I am currently using a Tiva C Series LaunchPad evaluation kit (TM4C123G) and have started experimenting with Keil's RTX RTOS. I use the on-board Stellaris ICDI debugger for my debugging purposes but as I add more features and breakpoints and start to monitor relatively large arrays, I notice that my monitoring on uVision really slows down which I suppose is to be expected.

My question is: Would I have any benefits in performance (for example, more breakpoints, faster monitoring) in switching from the ICDI to an external JTAG/SWD interface like a J-Link Edu debugger?

The reason I am asking is because I'm thinking of purchasing one eventually for real PCBs but would like to know if it would benefit me right now. I hope the question is clear, thanks!


texts:
I am trying to measure the current of a DC computer cooling fan (Intel E18764-001) at various voltages. Its rated specs are: 12V 0.20A. Check it out here.
So I am suspecting that this is telling me: "give it 12V and you should get 200mA of current" - Am I right?
Anyway, I supplied the fan with various voltages using my power supply starting from 5V all the way to 12V. I measured the current with a multimeter connected in series. Here are the results:

@5V --> 50mA (0.05A)
@6V --> 30mA
@7V --> 30mA
@8V --> 30mA
@9V --> 40mA
@10V --> 40mA
@11V --> 50mA
@12V --> 53mA

Interesting results. Here are my questions:

Why isn't there a proportionate increase in current with every increase in voltage? In fact, after 10V, the current goes up as voltage goes up! Does it have anything to do with either the fan going all funny because it is not getting its designed voltage or the wires can't handle any current more than 50mA? (Last one unlikely as that still doesn't explain the drop to 40mA.)

Why are the current readings nowhere near the power rating of 0.2A?


texts: How would I design an S-R flip flop under these given conditions?

texts:
Given an AND gate, an OR gate, and inverters as needed, design an SR flip flop with S and R active low (0).

I understand that to make such a flip flop, I would have to place inverters on the circuit so that the AND and OR gates behave like NOR gates, as NAND with S=0, R=0 would lead to a race condition. However, I have no idea how I would place inverters in such a way for it to behave like NOR gates.


texts:
Having never worked with electrical components, ignorance of the most elementary sort is holding me back.  I'm looking for suitable components for logic control of DIY home automation equipment.  I've looked extensively online and have no idea.  What websites, books, etc. can I use to figure out what kind of hardware I need?

Some examples of the work the logic controller will need to perform:

Read signal voltage from 6 to 12 sensors (mostly < 5V.  At least a few < +/- 0.05V) and communicate that data to software
Operate outdoors down to -10'F and up to 120'F
Run OS/software based on a common programming/scripting language
Turn on and off relays that control 12VDC, 48VDC, 55VDC, 110VDC, and 220VDC circuits
Crude Real-Time Clock (1 second precision is fine)
Use a common physical connect for access to the UI (RS-232, ITU-8P8C, etc)
Execute really simple programs

I'm not even sure what all information you need to help me.  If you ask for clarifications I'll edit my question pro-actively.  Please edit tags as appropriate.  I'm quite lost, but very motivated to learn.


texts: Which cell balancing method (active or passive) is best for low-voltage BMS (Battery Management System)?

texts:
As a beginner, I am going to design and develop a BMS (Battery Management System) for low-voltage applications (electric bike). So I would like to know which cell balancing method is perfect for low-voltage BMS.

Is active cell balancing method (fixed resistor, shunt resistor) or passive cell balancing methods best for low-voltage battery pack?

How should I decide that?

Please explain in a way that will be helpful as a beginner.


texts: replacing home appliances' internal 120v to 220v

texts:
stackexchange,

am new to electronics but am fairly resourceful. am asking this question out of curiosity. i have 2 home appliances which I bought in US.

A Sunbeam hot shot (hot water) dispenser which runs on 120v 1450w 60hz
A Hamilton beach blender which runs on 120v 175w

I currently live in Bangalore, India. These appliances have been lying unused with me since 2 years and I would want to use these appliances. Selling them off is not an option. Also I don't want to buy a bulking step down converter as it looks ugly on my kitchen counter space.

I read an article on ebay about replacing the internal circuit breaker.

Is this possible on the appliances mentioned above? If so do you think an electrician here would have the knowledge of doing such a procedure? What parts, equipments would I need for such a procedure?

Thank you.

Update

I was of the impression there might not be buyers for US bought electrical appliances in India but am guessing since its October (the month of immigrants from India to US on H1B) I have had quite a few people approach me to buy those things I listed.

From reading the immediate comments to my question, am guessing I misunderstood the ebay post and that converting a home appliance from its default voltage by modifying it internally may not be possible as a DIY or even industrially.


texts: Arduino - Not outputting 2 separate signals

texts:
I’m trying to get an Arduino to output 2 signals with different frequencies for a project.The schematic of the circuit is shown below.

I’m trying to experiment using Pulse Width Modulation to give me a constant signal (the code is similar to dimming an LED). Long story short, when the Arduino powers on the LED connect to ~9 flashes at a constant frequency (I still need to find out the frequency using a scope) and ~10 doesn’t flash at all. Once the button is* pressed* ~9 stops blinking, ~10 blinks for 30ms and ~9 starts blinking again.

So, my question is there a way I can get 2 signals to be outputted from an Arduino and somehow adjust the frequency of one of the outputs by changing a number (like ‘freq (1000)’ for 1 kHz).

Thank-you to all in advance.

//le code

int frequency = 0;
int milli = 10;
int milli2 = 30;
const int button = 2;

int buttonState = 0;

void setup()
{
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(button, INPUT_PULLUP);
}

void loop()
{
  buttonState = digitalRead(button);
  for (frequency = 0; frequency <= 255; frequency += 127) {
    analogWrite(9, frequency);
    delay(milli); // Wait for 30 millisecond(s)
 }
  for (frequency = 255; frequency >= 0; frequency -= 127) {
    analogWrite(9, frequency);
    delay(milli); // Wait for 30 millisecond(s)
  }

   if (buttonState == LOW) {
    for (frequency = 0; frequency <= 255; frequency += 127) {
      analogWrite(10, frequency);
      delay(milli2);
 }
     for (frequency = 255; frequency >= 0; frequency -= 127) {
    analogWrite(10, frequency);
    delay(milli2);
    }
   }
  }


texts: What is the failure rate for PV string blocking diodes?

texts:
PV generators do often contain low voltage bypass diodes at module level, and less frequent high voltage string blocking diodes. Example of such blocking diodes are the Ixys DNA30E2200P (VRRM = 2200V) and DSI30-16A (VRRM = 1600V).
String blocking diodes
These string blocking diodes normally operate in forwarding mode, thus at a higher junction temperature. Let's say forwarding 2,3 Amps at NOCT. NOCT is irradiance 800 W/m², ambient temperature 20ºC, wind 1 m/s.
PCB assembly with heat sink
String blocking diodes are often soldered on a PCB and mounted with heat conducting material onto an aluminum heat sink.

Failure rate
Can someone point me to authoritative source availble for failure rates of high voltage (VRRM > 1500 V) diodes that are used as string blocking diodes in a photovoltaic generator setup, and where the DUT are manufactured 2007 or later?


texts: What is difference between changing magnetic field and changing magnetic flux?

texts: In some books when it comes to electromagnetic induction is mentioned the term changing magnetic field and into other changing magnetic flux so I'm interested in whether there is a difference or is it one and the same thing?


texts: Question about the 'HALT' state of a FlexRay controller

texts:
My question has to do with the 'HALT' state of a FlexRay controller which is implemented according to the Autosar specification.
I have a project in which I need to invoke the Fr_AbortCommunication function in order to stop sending tx messages from our ECU on the FlexRay bus. Details about it here:
https://www.autosar.org/fileadmin/user_upload/standards/classic/4-1/AUTOSAR_SWS_FlexRayDriver.pdf
When invoked this function immediately stops the transmission of tx packets from my ECU but sometimes, depending on when it is called within the duration of the FlexRay cycle it will interrupt a tx packet while it's being transmitted. So for example there could be situations when only half of a tx packet has been sent on the bus when this function stops the communication there before the packet is fully sent on the bus.
I have read in the autosar documentation that this function invokes the Freeze command which puts the flexray controller in the halt state from which, in order to become part of the communication again must be reconfigured.
My question is this:
When I invoke that abort communication function and interrupt a TX packet that is being sent on the bus, what will happen to the intended receivers of that packet(other ECUs that the packet was intended for). Will they notice that I have interrupted the transmission from software and disregard that packet? Or could that half packet cause some issues on the receiver side? I could not find any information on this.
Please help me understand this by pointing me to the right information from the documentation if possible. Thank you!


texts: Is it possible to reverse engineer a ROM chip by grinding and taking photos?

texts:
Recently someone made a claim that you can reverse engineer a ROM by physically grinding the chip and taking pictures of the various layers.

Is this really possible?


texts:
The circuit below is from this Reference Design.

I want to understand the clamp network at the input. How is VGS of Q1 kept at a safe level?


texts: Generate +/- voltage outputs using two boost converters?

texts:
I am working on a project to power some audio equipment that requires +/- 15V DC. Output current load is about 250mA, maximum.  I am wondering if there’s any reason I couldn’t create this using two switching boost converters and a DC wall wart, as shown:
Edit: Would this circuit work better?


texts: Can OID technology return an X, Y coordinate?

texts:
We are working with a overseas vendor that is using SONIX OID technology.
(according to our vendor we are using OID v2)

We are using OID technology from them. A smartpen with OID technology is able to optically recognize small patterns printed on paper. It is able to discern if you touch certain areas (you have to define them) on the printed media.

I know that we can define areas on printed media and assign certain IDs.  Imagine you have picture of a piano with 88 keys, a drum, a guitar...  You can assign different parts of the band different IDs.  For example you define the drum as a region and that gets ID:1 and it plays drumsound. You define the guitar as another region and that gets ID:2 and it plays guitarsound, etc.

However, I'm trying to see if OID technology can also give you back an X, Y coordinate when the pen touches the paper.

The reason why I want to do this for example is I want to map the keys of the piano to different pitches.  Instead of defining 88 regions, I just want to check what the X,Y is and I can determine via math which key they touched.

I'm trying to search on their website to see whether OID can return X, Y.

Does anyone on this list have experience with OID and specifically with SONIX?
If so, can you help me out here?

Thank you.


texts: Can you power ac motor in ev with ac generator?

texts: Can a smaller ev with ac motor be powered by an ac gen instead of using a battery pack and everything that would go along with it?  If so, what would the arrangement be going from gen to motor?


texts:
I am creating a circuit in which a MCU (STM32) must drive 12VDC outputs, and wanted to make sure there wasn't anything missing in my driver circuit for the outputs.

-R1 is the inrush current limiting resistor
-R2 is the pull-down resister to keep the mosfet gate low if the MCU pin floats,
-D1 is the flyback diode, for protection against inductive loads, which will be a use case.

PS: I forgot to change the diode in the circuit, the actual part number is GSD2004W

simulate this circuit – Schematic created using CircuitLab

The load will be connected to the 12V power line and the ground will be switched via the out pin.

The expected load will be practically anything as long as it is 12V and less than 250mA. But there will definitely be relay coils, indicator lights, and solid state relays attached to the output.

If there is anything I am missing that would be necessary or even a good idea or small improvement to include? I just don't want to spin a board with this and find out something wasn't working as intended, so some assurance would be nice.


texts: Is it safe to leave the GND from an antenna jack unconnected from an active antenna amplifier?

texts:
I need help with trying to use properly this circuit, the original idea came from the late Tony Van Roon who designed it.
According to the article it seems that the logic behind it is that the dim signal goes to the FET amplifier thus improving the signal. Of course I understand that there can arise some considerations as there can be noise nearby from EM fields and so on. But that is not my question.
My question is can you use this circuit in a telescopic antenna such as receivers which lack from a jack as indicated in the circuit?. And if so which ends to connect where?. I intend to use this to improve the reception in my SG-622 shortwave radio but my unit does not have a jack.
Since I don't have access to the GND of the receiver I can use an aligator clip to connect the telescopic antenna of the receiver to the output jack on J1 which is tied to the output of the 470 pF capacitor C2.
However I am not sure if it would be safe to leave the GND from J1 unplugged?. Will it have the same results?. Will it improve the signal?.
Some guy used this for a transistor radio and the video can be seen here. Near the end of the video he shows how he had used it but the video doesn't show very clear where did he connected the GND on the receiver. In the comments this person indicates that he connected the output from C2 to the tunning capacitor on the transistor radio and it can be heard that the reception improved. However some person in the comments indicated that such circuit cannot be used in whip or telescopic antennas on radios as most of these are for FM and AM uses another antenna. This has left me confused.
Another guy seen here used the same circuit for his Baofeng uv-3r receiver which it does come with a jack which it does have access to GND on the receiver. On the same video it can be seen around second 37 that the GND from J1 is left unconnected when used in a telescopic antenna such as in those portable SW receivers. The video doesn't seem to show very "much improverment" and it seems it was just a modest boost. Thus, will leave unconnected the GND make any effect?. Can someone help me here?. I'm really in doubt if should it be safe and okay to leave that unconnected?.
Can someone help me to address these doubts?.


texts: Can a MCP4361 digipot have a resistance of 0?

texts:
I would like to use an MCP4361 digipot as an adjustable voltage divider with Pin A being 5V, B being ground, and W being Vout. I need the wiper voltage to span the full voltage range, including 0 and 5V.
Is this possible? Thanks.

http://ww1.microchip.com/downloads/en/DeviceDoc/22233a.pdf


texts:
I would like to simulate a verilog design that is to interface (via a FiFo to USB chip) with a program running on my computer. I have set up my program to redirect all reads and writes to Linux FiFo files (man mkfifo) and am now trying to write a testbench for my verilog code that emulates the FiFo to USB chip. The idea is to read data from the Linux FiFo file and -if there is any- forward it to my DUT.

The Verilog standard names a number of system tasks to read data from a file

$fgetc (Get a byte)
$fgets (Get a string)
$fscanf (Get formatted data)
$fread (Get binary data)
$readmem* (Fill a whole memory at once)

However, these system tasks will block until there is data available or an error occurs. Even worse, they block the whole testbench even when fork'ed so something along the lines of

reg [8:0] code = 9'd0;
...
fork : fgetc_with_timeout
    begin
        code=$fgetc(input_file);
        disable fgetc_with_timeout;
    end
    begin
        #300;
        disable fgetc_with_timeout;
    end
join
if(code)
...

will not work. So, is there any way to get a nonblocking read from a file or is there a way to get the number of remaining bytes/bits/words in a file?

I am using Xilinx ISE so I am constrained to Verilog (not System Verilog), so I am looking for something that works in ISE, and I would prefer to not use PLI code for this if possible.

Best regards,
mox

p.S.> Searching for anything involving 'nonblocking' and 'verilog' lists mostly results not related to my problem, however I have found this non-answered question at the Xilinx forums: https://forums.xilinx.com/t5/Simulation-and-Verification/xsim-and-Verilog-file-IO-is-non-blocking-read-of-a-file-possible/td-p/685611


texts: How dangerous are disconnected bulging batteries?

texts:
It is well understood that if you have a device that uses a Lithium-Ion battery, and if the battery starts to bulge, then something is wrong with the battery and you should properly dispose of it by taking it to a battery disposal/recycling center.  Improper handling could result in a fire being started by the faulty battery, so it's best to dispose of the device and have it replaced.

However, I am curious when the battery begins to deteriorate and starts to bulge, is it still dangerous when it's removed from the device and set aside?  To be clear, none of the metal leads are coming in contact with any metallic, or conductive material, so the circuit is not complete on the battery.  It's just sitting on a non-conductive, safe surface.

Context

I bought a piece of hardware yesterday at its only problem is that the battery is bulging. I've taken out the battery and I want to keep it until I can find an OEM replacement, which could take a few weeks to arrive from the distributor.

I want to keep the old battery so that I can compare it against the replacement which, I'm afraid, might be a KIRFy piece of hardware.  I'd want to return it and get a refund if that were the case.  Keeping the old battery around for a while does have it's purpose.


texts: Find node voltages for MOSFETs given Vdd

texts:
In this circuit, Vdd = 5V. We are given the channel widths to be 11.1 um, 25 um, and .25 mm for M1, M2, M3 respectively.

The hint is to use an iterative process, so from what I understand we have to make initial assumptions. I know that all MOSFETs are in saturation because \$V_{DS} > V_{OV} \$.

I am not sure what other assumption to make.


texts: Searching for root cause of TC4422A failure

texts:
I'm working with a device which employs the Microchip TC4422A to drive a series LCR load in the low kHz range, PWM, 50% DC. The device actually has several of these driver circuits, for several loads, each controlled independently.

The system exhibits no failures when all loads are connected (several hundred systems in the field). In configurations where there is an unused driver circuit (load not connected) there are many failures of the unused TC4422A device. The unused driver output is connected to a trace on the PCB which is several inches long, all the way to the PCB header connector. The circuit is floating, nothing pulling it up or down, no capacitors, no steering diodes.

I believe the reason for failure is the floating output of the unused driver. I believe the otherwise floating circuit is being coupled to external radiated EMI, causing the voltage on the driver output pin to exceed maximum ratings, causing latch-up of the driver.

If there was an issue with the power supply/ground to the drivers, they should all be at equal risk for failure, however the unused driver is the only one failing.

What I don't understand is precisely how this is happening. I can't reproduce the failure on command. There are many variables in the final installation.

Any insight is greatly appreciated. My apologies for the general nature of the information, it's a sensitive situation and don't want to divulge too much.

EDIT: Added schematic

U2 with the load connected will not exhibit any problems. U1 with no load connected, output floating, fails at an alarming rate. The two devices share power supply, input driven from the same uC. U1 is not driven by software in this configuration.


texts: What is the practical advantage of using mirrored signal outputs eventhough what matters is balancing the wires?

texts:
Some devices output differential outputs since both wires carry varying signals which are mirrored. Most devices on the other hand output one signal carrying and one GND wire. There is also differential-ended wiring and single-ended wiring. My question will be about "external" interference type of noise(EMI or RFI or maybe capacitive coupling) impinging upon both wires.

After some reading, if I'm not wrong I came to understand the fact that what we really want is "the same noise should appear upon each line" regardless of it is a differential or single ended wiring. And the noise must be common(common mode) so that the differential amplifier can cancel it out.

As far as I understand, there are two main ways to make the noise common. One of them is twisted pairing. The idea here is the wires are very close to each other because they are twisted and the same magnetic filed or electric field hits upon both wires. The second method to make the external noise common is to make the total output impedance(from source to receiving end) of both wires equal, so if an EMI happens both wires would induce the same voltage at the same time.

Upto here was just a summary of my understanding to show/check to whom read this.

Here is a simple illustration of a single-ended and a differential-ended wiring:

If they are both using twisted wiring and they are all balanced, they would both reject the common mode noise.

So what is the point to send the signals in mirrored fashion if one can balance and twist a single-ended wiring as well? Is that because something is practically easy to establish in differential/mirrored outputs? I really couldn't find a good answer to this.

edit illustration for a comment:


texts: I am trying to identify the following male connector to find a female counterpart. I do not believe it is a JST connector, and the website I found the matching picture on for my part does not list the connector type. It's typically used on small form factor fans.


texts:
Considering the following positive feedback network:

Its transfer function is given by:

According to Barkhausen criterion, for it to oscillate it is necessary that we have:
|AB| = 1
and phase(AB) = n*(2pi), where n = 0,1,..
However, I'm having trouble understanding the following:

If we have |AB| = 1, wouldn't Vo/Vs blow up to infinity? How can it generate oscillations with an infinity gain?

if |AB| < 1, I'm gonna have an oscillation with decreasing amplitude. However, I'm having trouble realizing this just by looking at the transfer Function.
if |AB| < 1, then the denominator 1 - AB would be less than 1 and the gain would be bigger than 1, correct? I cannot  understand how a gain bigger than 1 would output a decreasing oscillation.

if |AB| > 1, we have an oscillation with increasing amplitude. This one makes a little more sense to me, since the denominator would be less than one, but negative. so I would have a negative gain bigger than one, which would output an inverted input with increasing amplitude.

This is making me really confused


texts: How to find the current and voltage of this circuit?

texts:
I have this circuit with a Z-Diode in reverse.
Find U2 and I2?

I solved the fist circuit.

U1 = 0.7V,  I1 = (15V-0.7V)/1kΩ)= 14.3mA

The results for are U2-8.2V  I2=6.8mA but I just can't figure out how to come to that


texts: What is the reasoning behind wire/cable sizing?

texts:
What is the way of thinking to chose the proper wire gauge for the following system?:

There are calculators in web but I don't know the reasoning behind clearly. One example here: http://www.powerstream.com/Wire_Size.htm

As far as I know, the current is the only parameter which causes the heating and voltage drop. But voltage also taken into account when sizing the wires. I think they want to size the wire that it would cause %3 voltage drop.

Here is my example. Is my way of calculation correct?:

Lets say the intrinsic resistance of copper is rho. So for my system for the voltage drop ΔV to be 3%:

ΔV = 48 * 0.03

The total resistance is: [2*L*rho/(wire area)] so

ΔV = 48 * 0.03 = [2*L*rho/(wire area)] * I

(wire area) = [2*L*rho/(48 * 0.03)] * I

So in my case:

I = 3A

rho = 1.68 * 10^-8 (copper)

lets say L = 10 meters

wire area = [2*10*(1.68 * 10^-8)/(48 * 0.03)] * (3)

wire area = 7 * 10^-9 meter^2

Is that correct?

EDIT

The following two calculators calculate totally different results:

http://www.energymatters.com.au/climate-data/cable-sizing-calculator.php?main_page=wire_calc&calc_action=cable_size

http://www.solar-wind.co.uk/cable-sizing-DC-cables.html


texts: Why doesn't this capacitor short this circuit?

texts:
I'm doing a super simple Arduino led project. I followed a tutorial online that wired up the LEDs like this:

I'm wondering why this capacitor doesn't just short the power supply.

Can anyone provide me with some insight?


texts:
Is there some sort of don't care in Verilog (or VHDL) where I can say:

"Use either signal A or signal B, I don't really care because they would be functionally equivalent. Just do your best, good luck!"

Example:

module example
    (input wire [1:0] idx,
     // Sometimes an address of 3 shows up, but in this case the
     // output is irrelevant (not used/read).
     output wire [2+8-1:0] out);

    reg [8*3-1:0] mem_r;  // 3 words of 1 byte each, imagine content
    wire [1:0] idx_restricted;

    always @* begin
        if(idx == 3) begin
            idx_restricted = 2'b00;
        end else begin
            idx_restricted = idx;
        end
    end

    assign output = {idx, mem_r[8*idx_restricted +: 8]};
    // ***Here "idx" could be either idx, or idx_restricted***
endmodule

Without the idx_restricted there is an out-of-bounds to the mem_r.

Anyone know of something like this?


texts: Kindly help me identify the schematic creator/editor used.


texts:
I need implement real time notch filter to 50 HZ powerline noise
My MCU is stm32h753bi , how to do that?
is it rationale to do that in MCU or I should that on PC side?
thank you


texts: Lithium Battery Charger IC - Charging and Power

texts:
Basically, for the circuit I'm making, I need it to be powered by a Lithium battery. Also, this Lithium battery has to be able to be charged via USB.

I have seen external chargers for doing so, however, these would require for me to take the battery out each time and then re-charge it.

I have found this product, on sparkfun: Sparkfun

And the circuit/useage schematic looks like:

So if I understand this correctly:

Pin 1: USB (Power Lead)
Pin 2: USB (GND)

Pin 5: BAT (Power Lead)

The question is this: Suppose this is charging the battery, how can I therefore power the circuit? Since, I'm guessing that both of the leads from the Lithium battery go into the charger, rather than the circuit or the PIC?


texts: Opamp Voltage Doubler Unstable (After Extended Operation)

texts:
I've been working on a circuit which would drive an industry standard pneumatic regulator (E/P transducer).  The transducer takes a standard 0-10V command signal with a typical input impedance of 6.5 kOhms.  The DAC that I've selected (ADI 12bit 8 channel) has an internal 2.5V reference and can output 0-5V.

After researching extensively, an opamp voltage doubler seemed like a good fit.  This worked and was rock solid for about two weeks, but failed after a ~2 day period of continuous operation without warning.  Now the opamp output is close to a correct 2.0 gain but constantly fluctuates as if the output is barely stable and poorly damped.  Has anyone ever seen an opamp fail this way?

We're using a UA7812 linear regulator to supply 12V (from 24V) to the opamp quad (LM324AN) and admittedly it may not be sufficiently heatsinked (gets wicked hot to touch). Still, the 12V supply is solid at 11.83V and voltages supplied by the DAC appear correct and stable.  The actual resistors on the board are 10k with 0.1% accuracy and each measure 9.95k precisely.  Any advice in solving the problem is tremendously appreciated!  It's essential that this be a robust circuit.

Below is our final opamp configuration (and the part number):


texts: Fast rectifier diodes in parallel at SMPS

texts:
I'm trying to build a 35 V @ 10 A SMPS.

I don't have 15A diode to rectify the transformer output. Can I use two BYW29 in parallel? They are rated at 8A.

I know that when diodes are in parallel, the current doesn't flow equally through them. This means that one will do most of the job and get hot, while the other will be used only when the current reaches 10A?

Here is the SMPS schematic (I'm going to modify the output to be 35V at 10A instead of -35..0..35 V at 5A). Also I'm going to use two FS7KM-18A MOSFETs in parallel instead of one.


texts: What low cost LCD can I use in minus -30°C?

texts:
I'm looking for an low cost LCD I can use that can still operate even if they it's exposed by -30°C.
Normally, the 1602 LCDs have a minimum operation limit at 0°C. So I cannot use that ... or can I?


texts: Oscillating boost converter output voltage that has a differential amplifier for load, in DRV8662 piezo actuator driver IC

texts:
I am building a circuit to drive a piezo stack in a pulsatile fashion and I am using  the DRV8662 piezo driver from TI to do so. The circuit diagram is shown here (please disregard the several ammeters and voltmeters shown):

The DRV8662 chip has the following internal circuit (block diagram):

As you can notice, I am imitating the load of the piezo stack of interest through a 380ohm resistor in series with a 1uF capacitor. However, the issue I am facing is concerned with the voltage at VBOOST (PVDD) which in fact serves as a power supply to the amplifier, whose output is supposed to drive the piezo actuator.

The simulation of the circuit was done through TINA, from TI, which gave good results, and for now I am trying to build a small prototype on a Breadboard together with a proper IC adapter, which, I know, is not perfect, but I thought should work for a proof of concept, so to speak, even if imperfectly.

A picture of the breadboard together with an Arduino-nano that drives the EN and Input terminals of the IC is shown here:

The circuit is designed to have around 80V at PVDD once the EN signal is activated and once the Input signal is high the output+/- should give 75V across the piezo stack terminals. However, what I noticed when I probed the breadboard through an oscilloscope, while applying several pulses at the input, was that after the PVDD voltage dips as a result of the current discharge from the boost cap to supply the amplifier, sometimes the PVDD oscillates with a magnitude in the tens of volts in a certain fashion never to settle back until the input pulse turns low again, sometimes it settles then oscillates and vice versa, and in other times it settles around the intended DC value with no problem. In the presence of only the relatively small ripples the voltage is considered "settled". All these scenarios can happen in the same run with different pulses applied immediately after one another, not some seconds or minutes later. This is shown here (note the relation to the input pulse, depicted in orange):

For a closer look:

The way I see it, this oscillation is not the result of the rates of charge/discharge dictated by the capability of the boost circuit or the demand of the load, but rather an unstable behavior, perhaps something is disturbing the feedback loop of the boost controller. If we zoom in further, we can see the ripples caused by the boost switching carried over the oscillating signal:

I hope somebody might have a clearer understanding of why this is happening and how to go about fixing this problem.

Thank you very much!


texts:
Any suggestions on how I can implement resonance sweeping to find resonant frequency with a micro controller?
http://www.youtube.com/watch?v=VjVFKYE6Y-g


texts: Why we need 100n cap parallel to IC power supply

texts:
I've seen this in many schematics, I also do it myself, but I don't really know why it's needed. I've also noticed that on RGB led strips, there's tiny 100nf caps, too.

Why is it needed? Also, if it's generally needed, why aren't those capacitors integrated in the IC itself already? I'm sure there's tech for doing it, so why not?


texts: AC induction motor circuit and stall current

texts: How can I describe the stator current of a 3-phase locked/stalled induction motor by using equivalent circuit of the motor?


texts: How can I safely charge multiple deep cycle batteries simultaneously?

texts:
I work at a car auction and we use deep cycle marine batteries with booster cables attached to hand trucks to wheel around the lot for boosting cars.  I've been told by our battery distributor the best way to charge the batteries individually is at a low (2-5 amp) charge setting for 12-24+ hours.

We use a wheeled automotive battery charger that has several amp settings (2 amps up to 200 amps) in 6- and 12-volts.  We have had problems in the past with batteries gassing and even exploding from being hooked up to the charger improperly (luckily no one has been injured).

The latest failed attempt at charging them all simultaneously involves two copper pipes hooked to the positive and negative leads of the charger (running on a 2amp setting) and the positive and negative booster cables of 4 batteries attached to the corresponding copper pipe.  They don't seem to charge this way, even after several days.  My guess is that the amperage is being divided among the 4 batteries, so they're only getting a very small trickle, if anything.  I've been afraid to crank the charger up to 20amps or so to test this theory without finding out for sure if it is safe.

How can we safely charge multiple deep cycle batteries (we currently use 4) simultaneously using a wheeled automotive battery charger?


texts: Implement rotary switch, toggle switch and potentiometers with Arduino to simulate keyboard press

texts:
I am making a controller for my child; to be used in a video game on PC.

I did get a 11 position rotary switch, few toggle switch and a couple of potentiometers.
Now, I did check few tutorials and I can see that most of them implement momentary switch; so I am trying to work a strategy to implement the other switches and the potentiometers. As board I am using a teensy 3.1

for the rotary switch I was thinking to connect the right 5 poles to the same signal, and the same with the left 5 poles; so all but the center pole will be connected, and if I turn it right is like if I am pressing the + button (like to increase the speed of a car), and - button if I go the other way. Is this acceptable or the signal while switching position may be missed or give me incorrect results?
For the toggle switch; can I just implement them in the same way as a momentary button? So when I enable the switch (so the circuit is open), a keyboard press message is sent, while when I disable the switch, the button is pressed again?
What about the potentiometer? Is there a way to have the buttons pressed when I rotate it in a direction or another? These are not rotary encoders so they stop at one point; and I was thinking that they could be helpful as a way to move through menu.


texts:
I have found out that one can disassemble an ATmega with objdump or avrdude. And if the LB1 and LB2 bits are set low it would be much harder. So if these bits are set high or just reading the flash is allowed is it possible to extract the strings that the program may contain.

For example, the strings contained in a compile C program that runs e.g. under Linux can be find out by running "strings a.out".

Is it possible to read the strings from an ATmega similar to the "strings a.out" example?


texts:
I am designing an Xbee mesh network, planned size is around 10 nodes spread around 200 square metre area. It will be a combination of nodes reporting environmental data with actuators/loggers. I intend to have a single controller/logger to process the data from the network, however, I predict its location (and address) to change. I therefore would need a broadcast to be sent periodically from the current logger to ensure that the data is sent to the proper place

I have read that broadcast on the Xbee mesh network can really kill the performance, however, I was not able to find many details about specifics.

My question is then: would sending a broadcast every 60s in a mesh of around 10 nodes be feasible or would it put any strain on the network?


texts: How to move closed loop pole to meet the design requirements for settling time and overshoot?

texts:
I have tried adding a lead compensator as shown in the second image however am now confused as to how to move the closed loop pole on the right into the feasible region. The first image shows the poles and zeros in my system which are fixed. Any ideas on how to move this closed loop pole into the feasible region would be greatly appreciated! Or is it possible for me to achieve the design requirements with this closed loop pole remaining in the unfeasible region?
Many thanks


texts: How many harmonics are needed to produce a proper square/saw/triangle/etc wave?

texts:
I'm new to software sound synthesis, but I have a question that I can't seem to find the answer to.

I understand that, for example, a square wave at 100 Hz has its third harmonic at 300 Hz with 1/3 the amplitude; its fifth harmonic at 500 Hz with 1/5 the amplitude; ad infinitum...

My question is, how many multiples do I need to calculate for it to sound like a proper square wave using additive synthesis, i.e. calculating a Fourier series? How many harmonics is overkill?

Is that number the same for each type of basic waveforms: square, saw, triangle, and pulse waves?


texts: PIC12F675 Programmer using arduino (port from 12bit programmer)

texts:
I bought some pic12f675 and i am trying to program it using an arduino (for testing purposes, I was trying to write a simple blinking led code, I tried both my code hex compiled and another that I got on internet).

I looked around and found some pic18f or pic16f sketches, but I used this one for pic12f (the code was made for PIC12F508, which is 12bit, and my pic is PIC12F675, which is 14-bit):
http://www.reenigne.org/blog/a-pic12-programmer-from-an-arduino/

The only change I made was to use a 12V battery connected to a TIP102 transistor for the 12V input of the PIC.

One of the hex files I have tried to upload was the one below. I got the hex file general idea: size, address, type, data, checksum. The software I downloaded rejects this hex if I keep the last but one line (:02400E00C43FAD). It says "Address in hex file out of range.". I believe the reason I get this error is because the software was made for 12-bit and the code for 14-bit microcontroller.

:100000000428FF3FFF3FFF3F03138316850107309E
:100010008312990083169F01FF30831285000330FD
:10002000DC00FF30DB00FF30DA00DC0B18281F2873
:10003000DB0B1B281E28DA0B1B28182815288C30F0
:10004000DB00FF30DA00DB0B26282928DA0B262814
:100050002328A130DA00DA0B2B28000085010330B9
:10006000DC00FF30DB00FF30DA00DC0B38283F28F3
:10007000DB0B3B283E28DA0B3B28382835288C3010
:10008000DB00FF30DA00DB0B46284928DA0B462874
:100090004328A130DA00DA0B4B2800000C284F2847
:02400E00C43FAD
:00000001FF

With all that said, assuming that I am correct, I am trying to modify the sofware in arduino to support 14-bit controller (my pic12f675).

And my status on this task: 0%. (almost)

In the arduino source code, which you can find in the first link, then click on github link, file: programmer_c.c. (cant post more than 2 links)

Check the comments at lines 27 to 32.

// Load Data for Program Memory   x x 0 0 1 0     (0 data(14) 0)
// Read Data from Program Memory  x x 0 1 0 0     (0 data(14) 0)
// Increment Address              x x 0 1 1 0
// Begin Programming              x x 1 0 0 0
// End Programming                x x 1 1 1 0
// Bulk Erase Program Memory      x x 1 0 0 1

And here is pic12f675 programming specs (http://ww1.microchip.com/downloads/en/DeviceDoc/41191D.pdf)

The only changes I found was on "Begin Programming" and "End Programming", which was supposed to be:

// Begin Programming              0 0 1 0 0 0
// End Programming                0 0 1 0 1 0

Im not sure how to change it on code yet, but I will find. Even if I fix this, will not resolve the address problem.

If anybody has thoughts or want to help on this port, I would appreciate. Thank you.


texts:
We use STM32F2 at work, I recently face with a strange problem. I do not expect a direct answer from the crowd but I hope some pointers where to look at for root cause.

I have a clock that is 1MHz in frequency, the clock works well except a shadow frequency behind. 40KHz (something between 40 to 42KHz to be exact, I couldn't pin point). It seems a clock is drifting in some direction, these timers are implemented as counters and I cannot think of a scenario why I would see something in the background.

(I noticed problem in ADC reading first, so I know it is not a scope issue)

UPDATE
I am not in the office now, I will check with an analog scope today but basically, I sample a constant input with this clock (ADC is triggered as the rising edge of this clock). When I was analyzing data, I noticed a noise that is 40KHz and this is when I started looking which lead to this following picture.

Also, I use the Rigol's digital filter to make a LP filter up to 100KHz and I clearly see a signal at that frequency, small in amplitude but it is there. I will add a capture of that signal here too.

The scope capture attached.

UPDATE2
More screenshots:

The one on the left at a different time scale. The one on the right both time scales with zoom function.
The bottom left is with 750Khz LP filter on. The bottom right one is swimsuit shot.

UPDATE and CONCLUSION
It turns out this is really a scope issue, it is more than the aliasing, since the scope clearly shows some 40MHz background noise. We look at the potential issue with a high end scope and it is not there. (The root cause ADC issue is still there though, we just need to debug it)


texts: How can I screen 8 glass diodes from light?

texts:
I have 8 no. DO-41 sized diodes in a row like so (representative image):-

I'm hoping to place them adjacent to each other on a 2.54mm pitched proto board.  They're glass cased and I need to totally screen them from all light.  They can't be screened via the overall circuit's enclosure as it's translucent.

It's a sign of good quality in that they actually manage to butt up against each other on a 2.54mm pitch, despite the data sheet suggesting they might not.  However this means that they cannot be heat shrink covered, due to lack of space.  So are there any alternatives to screening them from all light?  Remember that a proto board will have holes beneath the diodes.  The proto board is an Arduino shield of 80mm x 60mm size so I'm hoping to keep it tight.

For interest, this is the spec. for a DO-41 package:-


texts: Do I have to deal with inrush current for my AC/DC converter?

texts:
I am having a question about inrush current for a simple AC/DC converter.
I am using a transformer from 230 to 36 V,followed by a full bridge rectifier and a filter capacitor of 1000 uF 100V.
When switching the power on, can I expect a high inrush current destroying the transformer or the full bridge rectifier?
After rectification and filtering the DC voltage should be around 50 V. The load will draw around 300 mA at 50V.
Transformer I will use
The rectifier is a "GBU8K"
Looking at the the rectifier, it seems it can handle a large forward current peak.
As for the transformer I have no clue. It seems it has a DC resistance of 6 ohms. Is it safe to assume that for fast inrush currents, the inductance of the transformer will have a high impedance and therefore it will be not a problem?
If this is a problem I think I will have to add a series thermistor I also have a hard time finding out which one would be suitable.


texts: Explanation request of a paragraph in a VFD manual about a diode, should I add it or not?

texts:
I didn't fully understand this paragraph in a VFD manual:

My question is: is the free-weeling diode exist inside the drive, or should I put an external one?


texts: Is this basic schema of a brushless driver correct?

texts:
So you have the "logic" part that runs at 0-5V. The controller is a microprocessor that can read out the current monitors and respond to them by changing the voltages by changing the connection of the FETs (one to ground, one to voltage). This brings voltage to the motor windings, and makes it torn.

For FOC, the microcontroller sets FETs so that the voltages on the coils become the output of the controller, which uses them to generate sine wave outputs at the motor voltage.

One thing I don't understand is where the current is sunk in FOC control. Where does it flow ? Wouldn't the neutral point in the motor simply increase to some average of the voltages across the coils ?

Is this accurate ?


texts: How do you connect a coax cable to a homemade bi-quad antenna?

texts:
I want to build antennas because I think they're pretty cool. Like invisible photons that pass through matter. But I'm struggling with basics and considering removing my tinfoil hat very soon.

Here is the not working antenna I built: https://buildyourownantenna.blogspot.com/2014/07/double-biquad-antenna-calculator.html

Does the shield need to contact the reflector ?
Is the reflector connected to something ?
Does the antenna element (the 4 squares) connects the shield and the coax inner cable ? How could it radiate then if it's a closed circuit ?

Many thanks !


texts: PCB design of the 80s (Arcade PCBs) - Ground/Power tracks

texts:
The 80s digital logic PCBs and more precisely arcade game PCBs were laid out in a specific manner.

What is noticed as a PCB novice:
 1) The (mostly 74 series TTL) ICs are laid out in a strict regular grid
 2) There were quite thick power/ground planes around the board
 3) There was quite a lot of space between ICs, much more than on later boards
using DIP ICs *

I do not know however if the later boards were multi-layer (>2) boards.
The C64 board looks much more crowded, although from the same era.

Can anyone elaborate on why PCBs from that era were made like this?

What was a limitation of the design process (CAD/Manual) or
manufacturing/assembly process?

Was the regular layout (point 1) only to make troubleshooting easier?
I often read in service manuals things like: "Solution: Bad 74LS20 at location 3A"

Is there any read-up on the theory of these layout guidelines?


texts: Why necessary to convert machine from 50hz to 60hz

texts:
I have a machine that is from china and built to run on 50Hz. It consists of several motors, heating elements and related electronic control systems.

What is the reason I cannot just use the machine at us power (60hz)?

I've heard that some times machines built for 50 can run on 60 - is this true? When is it preferible to change the cycles back to 50?

If I should run it on 60hz, what is the cheapest type of solution to impliment myself?


texts: Reading char values, returning 16 and 8 bit values?

texts:
I'm reading a internal memory block, im declaring a tracking variable and the start address and end address of the block"

//Defined as globals.
#define _beginAddrr     0x80000000/*0x80070000*/
#define _endAddrr       0x8000FFFF/*0x80077FF3*/
static UINT32 _currentAddrr = _beginAddrr;

The following code is called every 100 ms (so we dont hang the processor), reading 10 values at a time.

void memory_map ( void )
{
    int i = 0;
    for (i = 0; i < 10; i++)
    {
        if( _currentAddrr <= (_endAddrr) )
        {
            PRINTF("0x%08X : 0x%X",_currentAddrr, (*(char*)_currentAddrr)); //Print Value
            _currentAddrr++; //Increment
        }
        else
        {
            //We finish, turn this false.
            set_memorymap_enabled(FALSE);
            return;
        }
    }
}

set_memorymap_enabled() sets the flag off so we stop reading memory, so the memory_map function is called in this way:

if(get_memorymap_enabled() != 0)
{
    memory_map(); //PERFORM MEMORY MAP FUNCTION FOR JIRA
}
else
{
    //PRINTF("Restarting _currentAddrr");
    _currentAddrr = _beginAddrr;
}

Im using an avr32UC3 microcontroller for this task, the output is the following:

My question is, if im reading a CHAR variable, why am i getting leading 'FF' on some variables, does it mean that the value is signed?