texts: I am trying to fix a robot control unit where the L6203 driver was burned / cracked. Replacing the L6203 did not make the motor run, so I am trying to trace backwards on the board. I expect the LS00 in the picture to be controlling the L6203, but I cannot find any data on a 89D3EEK. Could someone point me to a datasheet?


texts: How do I configure a TL494 to limit peak current?

texts:
I am trying to determine component values to operate a TL494 in a mode that limits the peak current. I am basing this off the datasheet's "Typical Application" (Section 10.2).

My understanding is there are two error amplifiers in the TL494. I can disable one error amplifier by tying the inverting input to the reference voltage on the chip and the non-inverting input to ground.

The other error amplifier needs to limit the duty cycle once the current in the circuit exceeds a certain value. Here is my conception of this circuit

simulate this circuit – Schematic created using CircuitLab

V1 is a 12 volt switchmode power supply. V2 is the reference produced by the internal regulator of the TL494. R1 is the load, I have used both resistive and inductive loads. M2 is any typical N-channel MOSFET with a maximum V_gs of 20 volts. I have been experimenting with IRFZ34 and IRFZ44.

Not shown is the connections from V1 to VCC of the chip, as well as the necessary capacitors and resistors to form the oscillator of the TL494. We can assume some low operating frequency like 10 kilohertz.

This circuit drives the MOSFET on and off in a common collector configuration. When the output transistor is on, the combination of R6 and R5 form a voltage divider which charges the gate. When the output transistor is off R5 discharges the gate. This is not the best circuit, but I mounted R5 right on the MOSFET itself. The same is true for D1 and C1. Even up to 180 kilohertz operation I don't see any ringing on the gate. Turn on time is about 0.5 microseconds, turn off time is about 1 microsecond. The components D1 and C1 were added to reduce voltage spikes seen on the source of the MOSFET. Even if I use a purely resistive load for R1 there are still some spikes, these components reduced the spikes significantly when measured with my oscilloscope.

The combination of R3 and R4 should produce a reference voltage of 2.5 volts. Section 7.3 of the datasheet indicates a recommended "Amplifier input voltage" of V_cc - 2. This would be 10 volts in my application, so I am well below that. Forward voltage drop across R2 should produce the same voltage when the current in the circuit is equal to 25 amps. My understanding is that the output turns off early in this case, reducing the duty cycle.

The selection of R7 is not something I fully understand. My limited understanding is that omitting the resistor would give the amplifier "infinite" gain, which isn't possible anyways. I basically just chose R7 because I had it and because the datasheet uses a 50k resistor.

If I ground pin 16 of the circuit this circuit works as would be expected, with no change in the duty cycle. If I connect pin 16 as shown, the duty cycle is lowered but not by any logical amount. With this connected, I see oscillation of V2 up to a value of about 7.5 volts. This seems to indicate I've made some fundamental mistake, as I must be somehow affecting the operation of the internal reference regulator.

Why am I seeing oscillation of the reference voltage? How can I properly select R7? Is my understanding of the error amplifier flawed?

TL494 datasheet:

http://www.ti.com/lit/ds/symlink/tl494.pdf


texts:
I have a metal electrical panel sandwiched in the wall between two bedrooms. The panel has a relay mounted on it. It's very noisy when switching. I'm dealing with 50A, so trying to use a SSR presents it's own set of issues in terms of thermal management.

Any suggestions for how to dampen the click from the relay?


texts: How to make valid harness port when generate sub-sheet from vhdl

texts:
I have an VHDL file (a block) with huge count of the different port that can't combined into the one bus because they have different names. These signals will be further connected to different parts of the circuit. I want to "create sheet symbol from HDL" but Altium add each signal separately (not in harness). I'll try to make sheet symbol manually and add port with the right (predefined) harness type. But in the result Altium doesn't understand that VHDL signals included in harness that placed in the "sheet symbol" (green block). How can I link VHDL signals with the harness?

P.S. All signals in VHDL block named with similar prefix e.g. HARN_SIGN_*


texts: switching between solar input and 5V supply

texts: I am designing an energy harvesting system from a low power solar panel. I am using the output of the solar panel to power a high efficiency boost converter which charges a single cell Lithium battery as shown in the diagram below. My question is what is the best way to modify my circuit to switch between the solar input and an external 5V supply. Ordinarily I would use a diode in series with each of the supplies to switch between the inputs to the boost converter however given the extreme low power needs of the circuit I may not be able to afford the losses across the diode.


texts: Radio Transceiver bulkhead connection and Ground

texts:
I have a problem regarding mounting of RF transceiver. The main board inside metal cabinet is floating and when I check the antenna SMA bulk connector its outer case has a connection to circuit ground. This would eventually short the chassis ground to the circuit ground via pigtail. I need advice regarding this issue.

edit: from the comments below

The frequency is 850MHz.  Pout=20dBm.


texts:
I have created a boost converter which boost 12v to 60v. I want to be able to pulse this voltage under water.  I would like to have only the positive lead (Vout from boost) to come off the boost controller where the negative lead can just connect directly to the batter.  I was wandering if a relay is what I need and if yes would this one work. lh1501ba

EDIT

Ok, after reading all your helpful comments and answers I decided that the relay I chose might not be the right choice if I ever decide increase the frequency.  The delay will just be to much.  I made a amateurish attempt to include a PMOS to do the switching for me.  The voltage will be variable controlled, and because of the nature of the Vgs on the PFET, I needed to also include a NMOS along with a voltage divider to help me provide the the correct gate voltage.  I have it working correctly in LTspice but not sure how it will work in real life.

Here is the current schematic:

M2 is the PMOS and M3 is the NMOS. Also the signals are coming from the microcontroller and I have included a driver to drive the FETs.


texts: What's the right kind of reference to calibrate a measurement instrument?

texts:
I have been working in a calibration system for a multimeter I'm developing.

To do this I'm calibrating the reading values using Fluke meters (basically my instrument has to match the Fluke ones).

However at college I was told that this is not the right way to do this, that I'm assuming the Fluke meters are on the right and have no error margin, so I was told to do the calibration using normalized loads.

I don't know what are or where to find these "normalized loads" so I came here to ask, what's the right way to calibrate a measurement instrument? Where can I find these kind of references?


texts: LTspice: Including Time Derivative of a Node Voltage in Initial Condition

texts:
I am trying to simulate an RLC circuit with the initial condition that V1(0)=2 and V1'(0)=0. I used D(V(V1))=0 in my spice directive, but I don't think the condition on time derivative has actually been implemented.(D(V(V1)) is negative instead of zero at t=0) Are there any suggestions on how I should modify my initial condition? Thanks in advance for any advice!

Edits:
At t = 0, d(V(V1))/dt = 0, I(C1) = 0, hence I(L1)= -I(R) = -0.5A. But the I(L1) in the plot still starts at 0, whereas I(C1) = -0.5A. I tried various values of I(L1) in the initial condition and the result remains the same.


texts: Transducers for sensing brain waves which can be made at home?

texts:
I am in my evil mad scientist mode right now, partly due to the finals tomorrow. Yesterday I was reading about those new consumer devices which allow one to sense brain waves. Somebody even interfaced those with an arduino (man they are everywhere) and a computer.

This got me thinking, can I make such a device at home? I know they could be bought for relatively cheap right now but I am in India and most of them cost more than I would ever have in one year.

Does anyone know of any diy transducers which could sense brianwaves using parts I could acquire easily? I am not looking for neurofeedback. That can be dangerous (for no openEEG for me). I just want to sense, not give signals back to my brain.


texts: Operational Amplifier - Avd - Aol Characteristic

texts:
I am looking on "Malvino Electronic Principles" and it writes that the "Aol" (Open Loop Gain) is 94dB. I am looking on TL082 datasheet and I find the parameter "Avd -Large-signal differential voltage amplification". The "Avd" is like "Aol" or something entirely different? Also, the Avd is measured in V/mV and not in dB? Could anyone explain me if there is a correspondence between V/mV and dB?

TL082 Datasheet:
http://www.ti.com/lit/gpn/tl082


texts: Wiring 2 separate PIR’s to an LED Floodlight

texts:
If possible can someone please confirm that this would work?

I want to place a waterproof box on the front of the house, next to this I will put an LED floodlight (without PIR), I then want to put 1 PIR about 10 meters away from the house in one direction, and then another PIR 50 meters away in another direction, would the quick note I made below work or have I got it wrong? Any advice would be much appreciated.

James


texts:
Just was thinking to buy an oscilloscope, thus went to a shop and started to rummage all of the shops to buy an osci. which could be suitable for me. Read specifications of them. Some features was clear to me and I know them. e.g. sample rate or frequence and I know why the price of oscilloscopes. increases with increasing these parameters and I know what range of these parameters could be suitable for me but there is a question that I couldn't find any answer for it on the net. Why do some oscilloscopes have several input channels? I know with this feature you can capture several signals at the same time but the main question is that when do you need such a feature? I'm thinking that when do I need to capture several signals at the same time but couldn't find the answer. Maybe you could clear me out.

I guess we cannot find any Oscope with less than two channel. Why?

Please post your answer with your experience about what made you to purchase an oscope with more channels. As you know, Oscops with more channels are expensive and so couldn't find anybody ovehere that has oscope with more channels.


texts: Maximum safe working voltage of capacitors

texts:
The answer is 30kV.
My method led to an answer of 41KV, where did I go wrong?
 I believe I cant just add the Vmax(s) at the end, but what would I do instead and why?


texts: Max load supported by a single pin of ATX 24-pin connector

texts:
I have a requirement where I need to control around 20 solenoids which is housed separate from a Raspberry pi, ATX PSU and veroboard containing my logic circuit. For convenience I will call them CASE-A and CASE-B.

The solenoid requires 0.5A@12VDC and the pump requires 3A@12VDC. This will require me to transfer about 13A between CASE-A & CASE-B. I need the connections to be modular so that I can pull the cases apart for troubleshooting/maintenance.

Can I use the standard ATX 24-pin connector ? (something like this--http://www.amazon.com/29-5cm-Computer-Female-Extension-Power/dp/B00EZ50W36/)

I can see the following way to connect them up,
(a) In CASE-A, connect one leg of each solenoid and the postitive lead of the pump to one wire of the ATX 24-pin cable. In CASE-B, connect the other end pin to the +12V lead in the ATX PSU.

(b) In CASE-A, run a separate wire from the other leg of each solenoid and the negative lead of the pump to separate wires of ATX 24-pin cable(21 wires). In CASE-B, connect the other end pins to my veroboard logic circuit (the circuit would then complete the connection to ground depending upon logic controlled by the RPI).

Will the standard ATX 24-pin connector be able to handle the load?

Is there a different way?

Thanks
Vijay
PS: Veroboard logic will be similar to Will this schematic work?, however instead of 5 pumps there will be one pump and 20 solenoids.


texts: AA battery vs AAA battery - amperage and voltage

texts:
I am testing the RPM values of a 1.5-3V motor with AA and AAA batteries. When I attached a dual battery holder with two AAA batteries to the motor, the motor spins almost twice as fast as when it is connected to the dual battery holder with two AA batteries.

Since both types of batteries have the same voltage, why does the motor spin faster? I know that AA batteries typically have more capacity in terms of mAh, however I'm not sure how this translates into motor RPM.


texts: Range-limited integers or unsigned/signed in VHDL

texts:
In VHDL the Integer type is defined as a 32-bit signed integer. Most guidelines recommend that it must be constrained when used for synthesis if don't want a full 32-bit bus. My question is regarding your experience with various synthesis tools and the following piece of code. My assumption is that the non-dependent signals would be optimized away, but there might be other issues.

signal x : integer;

process(x) is
    constant alpha : integer := 12;
    variable y : integer;
begin
   y := (alpha*y + (100-alpha)*x) / 100;
   result <= to_signed( y, 16);
end process;


texts: Effect of Rapid Switching between Charge/Discharge of Lithium Batteries

texts:
I have made a DIY offgrid solar generator that utilizes an arduino to determine when to dump excess energy to a water heating load.
I have programmed the arduino to activate the load circuit when the cells reach 3.5 V.

My concern is that due to voltage sag of the battery, the instant that the load is applied the arduino will then sense a lower voltage and disconnect the load.

This will cause the load to be turned on and off rapidly as the voltage sags below 3.5 V and then bounces back up to 3.5 V, putting the LiFePo4 cells through rapid cycles of charging then discharging.  I am going to test this to determine at which frequency the cycling takes place, although I am sure this will be dependent on the power being provided by the solar array.

Will this rapid switching between charging the batteries and discharging the batteries cause any sort of degradation?
Is it possible that this could cause waste heat generation and side chain reactions that accelerate the aging of the battery?

I am considering adding a bank of capacitors and using a PWM output to smooth out the alternating current.  I am still uncertain if any of that is necessary as I do no know the extent to which this is a concern for my battery.  I did check the setup and determined that the load is switching at around 0.4 Hz.


texts: Couldn't get a 741 OPAMP to work as inverting amplifier with smaller (but not so small) resistors

texts: Using a 741 opamp,  I constructed a simple inverting amplifier circuit as in https://en.wikipedia.org/wiki/Operational_amplifier#/media/File:Op-Amp_Inverting_Amplifier.svg   ; I first tried Rf = 1k and Rin = 330 Ohm. Driving the input with a 1khz sine wave with 1v peak to peak amplitude, I expected to see a gain of -3. Instead, I got a bigger output that was so dirty that I couldn't tell what the gain was. I also think that the output was even in phase with the input! (Sorry I don't remember exactly, and am away from the lab now.) Then I put on a load of 1k. Now the output was clean, but still in phase with the input and was small, maybe even smaller than the input! When I replaced Rf and the load with 10k resistors and replaced Rin with a 4.7k resistor, the result was as expected. The gain was of magnitude about 2 but 180 degrees out of phase with the input! Could someone please explain what happened when I used the smaller resistors? Does it have to do with the 741's output impedance? That would seem strange since the output resistance is only 75 Ohm. Thanks!


texts: Making a square wave which has two different kinds of pulse width

texts:
I am going to make a square wave which has two different kinds of pulse width.At first,i think i can use the digital logic gate to finish it,however,after taking lots of time for trying,i still can't make it,so i come here to ask for help or suggestion.

The square wave i needed is as below

x and y means i don't care about its length,x can be bigger or smaller than y


texts: Can I use a USB connector/plug for RGB Led Strip

texts:
So I have an RGB Led Strip that requires power (3 Colours and the ground).
In total it draws about 1A @ 12V = 12W.

Could a USB socket be used to handle this? Otherwise I'm simply seeking a neat and tidy (read small but with some grab still) connector to plug and unplug the unit from the controller. Perhaps even an S-Video connector? I'm sort of clueless but just want something to handle this relatively small load.

Thanks.


texts: How to model / control a FCCM buck (variable frequency)

texts:
I am trying to control the voltage of a buck in FCCM mode (where the half bridge grounds the inductor until the inductor current goes negative by X mA, and then turns it on again), but I am suffering to understand how can I model/control it, this is my first time trying to do digital power.

The microcontroller only controls the on time (and so the inductor peak current, as it can be calculated based on the delta of the actual input and output voltages), but it have no control over the switching frequency, as it is defined by the output current, output voltage and the delta of the input and output voltages...

My main problem is that all materials teaching how to model and control bucks are for fixed frequency bucks where you choose your switching and sampling frequency for the control loop, and I have no idea for what to search / where to start.

How can I define my ideal sampling frequency (is this acceptable to have a fixed sample/control frequency? this frequency could be lower than the maximum operating frequency?) and how can I model and control this kind of buck?
Explanations and suggestions of learning materials for this specific control mode are appreciated!

Thank you!

simulate this circuit – Schematic created using CircuitLab


texts: Camera Parallel Interface vs Camera Serial Interface?

texts:
I need to select a System on Module that will be used to stream a HD video stream over WIFI. Ideally it should support two camera input.

When researching the various modules on the market, I find some SOCs exposing either Camera Serial Interface (CSI) or Camera Parallel Interface (CPI), or both.

I understand CSI is newer (and I assume 'better', but in which terms ?). Thus, from a system architecture standpoint, when should someone choose CSI over CPI ? Or the opposite ?


texts: What is the effect of redundancy coding on the bit error rate?

texts: If I have a channel with bit error rate BER = \$10^{-3}\$ after modulation, but this is too high so I decide to add repetition coding. With 2 code words and block length of 3 such that I have a minimum hamming distance of 3, giving the system ability to correct 1 error and detect 2 errors. How do I calculate the new bit error rate?


texts: How do I get the PIR sensor to output more than 3.3v?

texts:
I have a setup where I have a 12V source and a PIR sensor like the one pictured (below) and some LED strips that are rated at 12V that I've mounted under the stair railings. The problem I've hit is that the pir sensor only outputs 3.3V when triggered.

In extreme simplicity (and horror) here's the setup I have:

The sensor - Here's the details page about it.

The infrared sensor operates on a voltage range from 5-20v, but only outputs 3.3V when triggered. The LED strips I have are rated at 12V (though I have tested them to work as low as 7.6V).

By searching around I've gathered that I need to turn up the voltage somehow or get more voltage running through the sensor. I've tried various step-up modules (this is one of them), but most require at least 3.5V and above to work correctly. Is there a way to have the sensor output more than 3.3V when triggered or some other way to make this setup work?

PS: I'm not an electrician, so I appreciate layman terms. I do understand logic though.

PS2: I've read this question, but didn't quite get what the accepted answer suggested.


texts:
Recently I've been trying to fix a motor-controling board in my pool cleaner. After some measuring, I've figured out, that two MOSFETs are behaving strangely and their behaviour varies from the other two paires.

Unfortunately I am unable to find the types and specs of the FETs. This is what is written on them:

D409 BA6X17
VNH38 ON 58 65NLG

Isn't someone familiar with these?


texts: Decreasing of \$V_{in}\$ in a high pass filter due to the type of capacitor used

texts:
I observed a strange fact while using a simple RC high pass filter. Here is the circuit I  used.

On \$CH1\$ I measured \$V_{out}\$, while on \$CH2\$ I observed the value of \$V_{in}\$.

I kept the function generator at \$V_0=20V\$ pk-pk (sinusoidal), and I increased the frequency from \$10 Hz\$ to \$10^4 Hz\$ in steps.

The strange thing is that voltage on \$CH2\$ (which is \$V_{in}\$) decreased while the frequency was increased! That is, at low frequency \$V_{in} =V_0=20 V\$ (pk-pk), but then it decreased to \$4.5V\$ at \$10^4 Hz\$!

Nevertheless the filter seemed to work ok because if I plot the ratios \$\frac{Vout}{Vin}\$ (whith \$V_{in}\$ measured with oscilloscpe, hence decreasing) vs frequency (on log scale) I get the right curve, corresponding to my  cutoff frequency \$f=\frac{1}{2\pi RC}\$.

Obviously doing a simulation on Multisim or other simulators I get that \$V_{in}= V_{out}\$ (besides little variations).

Then I tried to build another filter with a different capacitor and I did not observe this strange behaviour, which makes me think that this was probably caused by the capacitor I used.

What I would like to know is if there can be any explanation for this behaviour of the filter wich is due to the characteristics of the capacitor used.


texts: where to add gain and volume controls to LM386 guitar amp circuit?

texts:
Im trying to make a super simple guitar amp.

heres the circuit using an LM386 operational amplifier:

What exactly would affect gain but not volume, and volume but not gain? In the example circuit on the LM386 datasheet theres a 10k potentiometer at the input, but online some people called this a volume control and some a gain control. Im confused. For a gain control I was thinking of adding a variable resistor or potentiometer between pins 1 and 8, instead of R3 in my circuit, because thats how gain seems its supposed to be regulated on the LM386. But will this also increase the volume? Does a bigger voltage swing of the signal mean a higher volume of the sound? I want to be able to get the distortion and clipping of high gain but at a low volume.


texts: How to measure microwave frequency with Lecher lines

texts:
I am working on a project where I need to measure the frequency of some microwaves (up to 10GHz) and as measurement tool I chose Lecher lines as they are easy and fast to build.
However after building the Lecher lines I found out that it's not recording any frequency, either microwaves or UHF.
The Lecher lines are ~ 40 cm long and are made of 2mm diameter copper wires mounted on a wood board. They are held in air by 3 pieces of plastic and spaced by a thin foam. The lines never touch each other as I used a thin foam as separators between the lines.
As a meter I use a 0-100 uA analog meter. When performing the measurement, I touch the wires from the meter to the lines from Lecher lines in a parallel way but no change on the meter is recorded. I also tried to use a red LED as a meter but it also did not record anything.
As a microwave power source I use the Wifi router's antenna.
Can someone help me debug my setup so that I would measure microwaves with Lecher lines or if you know other way of measuring the frequency (which is cheap to build), I am open to trying it.


texts: Do serially connected diodes share equal reverse voltage?

texts:
If I place three cheap 200 V rated diodes across a 500 V supply instead of one expensive diode, is the system guarantied to work correctly?

My worry is the situation at which two of the diodes share 150 V and the remaining 350 V appears on the other diode, bringing out the holly smoke. Would something like that happen?

simulate this circuit – Schematic created using CircuitLab


texts: Why alternators are used to generate DC?

texts:
Why is it that to generate DC, it's often an alternator that's used? Couldn't commutator rings be added and do without AC-DC conversion?

I'm asking because I wonder how efficient it usually is for a typical RC car motor to be used as a DC generator.

Thanks


texts: Calculationg base-resistor between microcontroller and transistor

texts:
I'm curious, when connecting my 2N2222 transistor's base to a PWM output pin on my Arduino, I know the Arduino can deliver a maximum of 40mA current. The 2N2222 only requires around 5 to 10 mA on it's base to switch the collector and emitter. Now, when calculating the base-resistor under "normal" conditions where I'm merely switching it directly from Vcc, the following applies:

However, when putting in a 500 ohm or 1K resistor in (1K for 5mA) directly it works great. But putting it in between the Arduino and the transistor, the transistor doesn't switch.

I suspect thus, that the resistance is too high of the base-resistor. Therefore, we may very well not need a base-resistor.

But, according to spec, the Arduino can deliver 40mA. So, am I correct in assuming the folling:
1) I should calculate the perceived resistance that the Arduino is giving, if it goes high to 5Volt and only gives 40mA, and then
2) Subtract that from the 500ohm resistor needed to make the transistor operate optimally.

Example:

So, I'm theorising that I have to then put in a 375 ohm resistor in to make the total resistance between the Arduino and the base resistor 500 ohm.

Somehow this doesn't feel right. Keep in mind, I'm not an electronic engineer, so I might have the cat by the tail here :P


texts: Unexpected output voltage in opamp (LM741, DC, single supply) circuit

texts:
As a beginner I tried to make a simple DC circuit with an opamp on a single supply. This is what I came up with:

simulate this circuit – Schematic created using CircuitLab

I use R3 and R4 as a voltage divider to get 1V between the inputs of the opamp, and R1 and R2 in the noninverting configuration. I tested this circuit in a few simulators and they show 3V at the output.

$$ Gain = 1 + \frac{R2}{R1}=1+\frac{560}{270}\approx3 $$

I built the circuit and measure 5.64V where I expected 3V. What am i doing wrong?


texts: Simplest possible 5V to +/- 10-15V converter (for op-amps)

texts:
Im looking for simplest possible solution to power op-amps from USB or phone charger.

Requirements:

+5V input voltage
±10V to ±15V output voltage
at least 10mA output current on both rails (+/-)
very low cost
low part count
simple and accessible parts (no specialized ICs)
low noise and ripple would be nice (small and cheap linear regulators at output allowed)

Is this possible without a transformer, when I need no separation and I don't care about GND shift relatively to USB GND?


texts: input voltage drop after connect to voltage regulator LM7805cv

texts:
i got a proximity sensor (https://www.aliexpress.com/store/product/ROKO-Proximity-sensor-SN04-N-NPN-NO-inductive-switch-quality-guaranteed/701042_1673833167.html)

So this is an inductive sensor, it has 3 wires ( black, brown, blue). According to the manual the brown is for VCC input (10-30v), blue is GROUND, black is signal(OUTPUT). This sensor is labeled as NPN NO (normally open).

First i did some test using 12V power source and from the output signal i got roughly about 12V.( Also if i use 9V vcc, i got output around 9V) So no problem so far.

Now i want to regulate that ouput signal from 12v to 5V. So i'm thinking to use LM7805cv voltage regulator to convert the output signal from 12V to 5V, nothing fancy ... But then here come the problem. As soon as i connect output signal from sensor (12V) to lm7805 input, the output that coming out from lm7805 is about 2-3V ( it's supposed to be 5V). So then i check the output voltage from sensor ( which is connected to the input of LM7805cv) and surprised that i got about 4-5v, it's supposed to be 11-12v right ?

If i disconnect the lm7805, the output from sensor back to 12V, but if connect to lm7805, that output from sensor drop to 4-5V.

I also check that there's nothing wrong with this lm7805. As i tried to connect it to 12v or 9v directly (without sensor) and i got 5V output.

Anything wrong? is it normal i got voltage drop that big? i'm not an electrical guy, i just know a bit about simple wiring. So anyone can explain this?


texts: what is the effect of a current-carrying wire through a solenoid?

texts:
The solenoid coil concentrates the magnetic field lines through the interior when the solenoid wire carries a current.

I am curious about a different case, however. If a (separate) straight wire went through the center of an unpowered solenoid coil, and this wire carried current, what would the induced effect be on the solenoid coil (say the solenoid is either grounded or left open)?  Would any induced effect fight the current on the wire through the center?


texts: Cutoff frequency: exactly -3 db of power

texts:
I have a question which may sound strange, but still I'd like to ask community to explain that. Hope other people may find it interesting aswell.

As we know, cutoff frequency is the one frequency harmonics of which is being reduced by 3 db (or Vpp is sqrt(2) times lesser than harmonics Vpp before the filter).

This image gives more or less clear picture of that idea (consider the red line, cutoff frequency marked as fcp):

What that means: the filter passes all harmonics of the input signal through, but some of them are being reduced in power. Harmonics of some frequency are being reduced by 3 db, this frequency is a cutoff frequency of that particular filter.

This is the defininition and the explanation of my understanding of the term. I'd be grateful for corrections, if any :)

Now, the question itself: the word cutoff means that something is being cut. So, we may say that harmonics of particular frequency are filtered, if Vpp reduced by 3 db or more. The question is - why exactly 3 db? Saying exactly I mean


texts: Is it possible to *proportionally* reduce a DC voltage supply?

texts:
INPUT: I start with a variable DC supply (rated up to 5A) that varies between 0V and 24V.

OUTPUT: Let's say I'd like to get a directly proportional output voltage between 0V and 5V (i.e. a re-map of the original range, so that 0V becomes 0V, and 12V becomes 2.5V, and 24V becomes 5V, etc.).

CURRENT DRAW AT OUTPUT: Assume this final output voltage (which varies between 0 to 5V) will be used to power a motor that draws a maximum current of approximately 1A. So, the motor's speed would change as the original supply, and thus the reduced supply, changes.

Is it possible to do the above? Regulators are out for obvious reasons, and a voltage divider would create a lot of heat and doesn't sound like the ideal solution.

EDIT:

A few people suggested PWM would be a simple solution, so I researched a bit and found this example of achieving PWM with a 555 timer (further questions below):

Is this a suitable implementation for my purpose, or is there a ready-to-use PWM-performing IC that I can try applying within my circuit?

Additionally, I looked up LM555's datasheet, and it seems to operate at max. supply of 18V, whereas I need up to 24V. Any suggestions on this front?


texts:
I am using servo and stepper motors for the first time, and have been searching for a solution to this basic problem:

I want to drive a shaft with a motor, whereby this shaft also has a ‘neutral’ state that can be switched on/off with a microcontroller. In this neutral state the shaft should spin freely, without any friction or resting torque from the motor.

This is any extremely low RPM application, so a precisely balanced solution is not needed, however a low weight/volume solution is preferable. I am currently using a small servo (35 x 16.9 x 32mm) with a max torque of 4.2kg/cm.

The simplest solution I could think of was to build a primitive clutch, whereby one or more solenoids bring a plate that is attached to the motor into contact with a plate that is attached to the shaft. If there is an existing off-the-shelf solution or alternative mechanism that anyone can suggest I would be very grateful to hear your thoughts.


texts: How do I properly use Sharp GP2Y0A21YK0F sensor?

texts:
I've recently obtained Sharp GP2Y0A21YK0F IR distance sensor and I'm not sure how to make a proper circuit for output measurement, since I'm getting lots of noise. The only thing datasheet mentions is that there should be a \$10 \mbox{ } \mu F\$ capacitor on power pins as close to sensor as possible. Well, I soldered it directly to the sensor's power pins and it didn't help.

Here's what the output looks on the scope:

The fat line at the bottom of the screen is the actual expected output and when I move my hand near the sensor, the line moves as expected, but the peaks remain the same.

Using an LC filter did remove the peaks, but I'd like to know if there's some industry standard way of solving the problem I have.


texts: How can a battery have electric potential?

texts: Electric potential is the potential energy of a charged particle in a point in space relative to another point in space in an electric field, all that divided by the charge of that particle. I don't understand how it relates to the voltage in a circuit and battery? To have a potential there must have a field...


texts:
I have several USB devices that are capable of running High Speed 2.0 (480 Mbps) mode but runs Full Speed 1.1 (12 Mbps) instead.
Take for example a USB DAC:
It advertise USB 2.0 compliant and fall back capability to 1.1
 SupportedUsbProtocols    : 0x03
 Usb110                  : 1 (yes)
 Usb200                  : 1 (yes)
 Usb300                  : 0 (no)

But in the device descriptor:
bcdUSB                   : 0x110 (USB Version 1.10)

Means that the manufacturer is using a IC capable of 2.0 but configured to run at 1.1?
This is not an issue but I was wondering what is the goal to run a device capable of running High Speed at lower speed. This create the need of a transaction translator and reduce overall performance.


texts: Calculate the capacitance of a supercapacitor

texts:
Is the formula for capacitance of a supercapacitor C = epsilon(A/d) ?

Since a supercapacitor does not have a dielectric, then will the permitivity be the permitivity of free space ?


texts:
Oscillation on an 4 phase 12 to 24V 20A boost inverter

I’m using 2 pieces of LTC3787 to make a 12-24V inverter.
I made a 4 layer board from it to have enough ground to make sure all will be stabile.
But I have big oscillation on my output. With no load it’s ok. But with a few mA of load the trouble starts.
I try to adjust the ITH RC values and tried only the master and the slave unit apart and tried connect my ground on different locations, canceled the 10pf caps on the voltage divider . So fare nothing worked out.

Hope some one can help me in were to look for to solve this issue
schematic:

[1]

[1]

VGS low side FET

[2]

VGS low side FET voltage

[3]

Input current - output ocsilation with 60mA load

yellow = current is 100mV/1A so top is about 75A spikes on the 12V input with 60mA load on the 24V side. blue is the output voltage rimple

[4]

ITH signal voltage - input current on the board 100mv/1A (about 75A)

[5]

input current yellow 100mV/1A- vgs lowside FET voltage

already thanks for all the help!!


texts: K150 PIC Programmer on linux with usbpicprog?

texts:
I'm to search a low cost PIC programmer to use with Debian Linux.
On another post i see a comment about use the usbpicprog programs to write .hex files.

With the usbpicprog.org softwares, you can write the .hex trought K150 on 16F628A in Debian/Linux?

On the usbpicprog, they talk about use the PCB used in herself project only!

The PIC programmer is:
http://mlb-s2-p.mlstatic.com/gravador-picburner-k150-usb-pic-de-brindesoftwares-cabos-14980-MLB20093350708_052014-O.jpg


texts:
I want to design a circuit such that the microcontroller can toggle a GPIO pin and shut the whole system (including microcontroller itself) down and then after a short period of time the power should turn back ON (may be 100ms)?
Can any one suggest a circuit for this? Thanks

The reason why I need this is, microcontroller's I2C latches up on ESD (-8KV) test and wont recover untill I power cycle.


texts: Custom WAVE file results in different sound profile than created

texts:
My problem is as following:

I'm trying to use my sound card to produce a custom repeating wave pattern which I will use in some laboratory test setup. My curve is based on a combination of a couple of sin/cos functions which I got from a Fourrier Analysis.  I created an .WAV audiofile of this repeating pattern and try to play it from my sound card.

However when I record the audioprofile which my laptop is outputting it looks different.

Does anyone know why this is happening? and how to solve this problem?

Original audioprofile:

Output from sound card:


texts: EPROM memory - the theoretical possibility of recovering data from memory after erasing the exposure with ultraviolet light?

texts:
I have a small question.

We have a EPROM memory.

Is there a theoretical possibility of recovering data from memory after deleting with ultraviolet light?

Is this theoretically possible?
Or maybe it is impossible?

Anyone can give a source/reference (eg. scientific publication)?


texts: Suggestions to filter RF from a long wire connected to a logic gate

texts:
The following is the schematic of a security system designed to work on the break-wire principle and intended to be used on a perimeter fence. The input 2 of logic gate U-3.1 is kept low via a long thin (60 ft) bifilar wire. Upon breakage of the wire, R4 makes the aforementioned input 1 high, which turns Q2 on. Although I have dedicated filter cap C2 (100nF ceramic) and ferrite bead on the break-wire near the circuit, Do you think that would be enough? Please post your suggestion to improve this filtering and to make this circuit more immune to false alarm induced by RF, EMI etc. The whole circuit board will be placed in an aluminium box except for the break-wire. The power source is 9v battery.

Kindest regards


texts:
i have this problem. I have to validate with a test that my connection on my power board can carry the nominal current required by the specs.

For current around 10A the setup I'm using is a Multioutput Bench PSU with all the output working in constant current mode in parallel, like the following figure:

If I need to go up to 100A this approach is not feasible anymore because the Bench PSU are normally limited up to 10A.

What are the PSU used for testing the ampacity for current value of 100A?

Are there any commercial type already available?

Are there any DIY way of doing this?


texts: Meter reading is not equal to the actual consumption calculated from the wattage of the equipments

texts: Today I have the checked the meter. It was showing 0.650 kW (instantaneous power) while just four  appliances were running. i.e two ceiling fans of 60 W each and two refrigerators of 150 W and 180 W respectively. Total power consumption 60 + 60 + 150 + 180 = 450 W. Why these readings are not same? Why there is a difference of 200 W?


texts: CB Radio Effects Unit. Can anyone help with a wiring puzzle?

texts:
I’m working on a small CB radio project for a friend, but am having a hard time figuring out some technical details.  If anyone has any ideas on how to solve this puzzle I’d be super grateful.
The concept:
A CB radio effects box which uses a microcontroller to add delay or reverb to the user’s voice.  (I've already got the effects part all figured out.)  My goal is to make a standalone box which you could plug your CB mic into and then plug the output of the box into the CB radio—basically like a guitar effects pedal.  Microphone->Effects Unit->CB Radio.  (See the concept diagram below.)

The problem:
While I thought this would be a really simple project, I’m stuck on how to wire the CB mic so that the transmit/receive button on the mic still works as normal.  I’ve tried a couple ideas, but I’m just not sure how to wire this project so that

There are no loud pops when you push in the mic button
The delay trail or effects from the microcontroller stop transmitting after the mic button is disengaged

My current wiring (see the Wiring Diagram below) isn’t working very well.  First off, there is a loud pop every time I push in the mic.  (I’m assuming that’s because the ground of the mic input is connect directly to the ground of the line output?). Also, once I let the button back out, the signal from the microcontroller still transmits.  So for example if I have delay on my voice, it continues to transmit the delay echos.

Also, here's a diagram of how a CB transmit receive button works and how it’s wired.

Any ideas on how I might be able to wire this?
Thanks so much for any ideas!


texts: Necessity of using emitter follower as the first stage

texts: What's the actual use of the emitter follower stage (Q1&Q2) in the following op-amp circuit? The only reason I see is to increase the input impedance. But even that I don't see it necessary because the source impedance is only 50 ohms and a common collector would be superfluous in this case. What am I missing?


texts:
1.regarding to logic gate concept i have to design the circuit with 4 bits multiple of 3 detector.
 but when i trying to make logic gate and  truth table it seems to me it's wrong so  i have no idea  how can i do design  circuit with 4 bits multiple 3 detector with truth table and circuit shape.
2.what actually detector do in logic gates and what is the affection of that on truth table?


texts: Information on LTSpice switching regulator macromodels?

texts:
I have read this Design Note 12 from Linear Technologies titled “An Op Amp SPICE Macromodel”. I was wondering if there is similar technical information about the macromodels of switching regulators (buck, boost and so on). Does someone know if there is some specification about what really is modelled in these macromodels?
Many thanks in advance!


texts: Overcharge Lithium-Ion when using charge controller + Arduino Load

texts:
I'm trying to determine if I need to rethink my circuit for a solar + Li-Ion powered Arduino. Basically a solar powered module with 3.7V Li-Ion backup for night / clouds (to be charged during the day). Being my first go at utilizing solar + rechargeable batteries, I've been looking at this [1] instructable, specifically Part 6.

Essentially my circuit is a solar panel connected to a TP4056 Li-Ion charge controller's IN connectors. I have my BAT+ connected to a 3.7 Li-Ion + terminal and the IN+ boost regulator to boost up to 5V, and likewise with the negatives. My boost regulator then connects to the Arduino.

My worry is that with all these in the same circuit, the charge controller will never stop outputting power to the regulator in order to run the Arduino, which could then cause anything unused to flow into the Li-Ion battery, possibly overcharging it.

Is this a legitimate possibility, or is there just something I've yet to learn more about?

[1]
http://www.instructables.com/id/SOLAR-POWERED-ARDUINO-WEATHER-STATION/?ALLSTEPS


texts:
I have read in several application notes that there exists a region called the Miller plateau where the current into the Cgd is large such that almost no current enters Cgs holding the Gate voltage almost constant.
The miller voltage is said to be the Vgs for which there is a rapid change in Vds for some load ZL and drain current Id.
So if for some gate voltage, the drain current is large and if the impedance is large too the Vds has to drop very low to accommodate that drain current.
My question is as follows: Does the rate at which the drain voltage falls depend on the output capacitance Cds of the MOSFET?
If so how does the output capacitance of the MOSFET discharge?
PS: No application note seems to consider the output capacitance of the MOSFET, for the switching characteristics.


texts: I just wanted to ask whether it is possible to voluntarily discharge a mobile phone's battery and transfer it onto another battery?


texts: Finding the network equivalent impedance Z(t)

texts: I am a bit lost no how to approach this problem? What should I do to get the total impedance?


texts: List of files needed to rerun Aldec simulation?

texts:
There are bunch of files needed to run an Aldec simulation. What is the minimum set?

Clearly this must include the Verilog/VHDL source, any testbenchs, and a project file. It also needs to include the list of signals from the waveform window.

Specific files suffixes that may or may not be needed are:
adf, aws, cfg, dat, ini, log, mgf, order, rlp, set, wsp, wsw.


texts: Sometimes once in a year, either one of main fuses or a fuse in room blow up due to something. What is the cause of this? Why do we even use fuses? Is it because the voltage doesn't stay at 220V all the time?


texts:
In the circuit below :

It is possible in physics to have :

L1 = 1 H
L2 = 2H
L3 = 1 H

and couple inductances like that:

K1 LL1 LL2 1.414
K2 LL2 LL3 1.414

I think I must respect K < sqrt(LxLy), true ?

For L2, I think it's necessary to have 2 times than L1 or L3, true ?

I don't understand why LSpice simulation software give me the error "bad K coupling for inductances" even K is < 1.

Good day


texts: Wiring RGB Strip LEDs w/ just positive and negative wire

texts:
I'm working on a small project, and I had some leftover strip LEDs lying around. They're just the RGB strip LEDs you can pick up at Five Below. They come with an RGB controller attached to a short USB cable. However, I needed to just cut off a short section of the strip for my project (a single section), and I only have a positive and negative wire, no RGB cables, because I just want white. I only have basic electrical knowledge so I don't know if I'm just going about this the wrong way, but I tried testing it by connecting a wire to the 5V pads on both sides of the section of LEDs and connected them to a female DC adaptor, then connected a USB cable to the adaptor and plugged it into a computer, but nothing happened.
Is there a different way I'm supposed to wire it, or can I not just use the 5V pad and ignore the RGB pads? Or do I connect the negative terminal to a different pad than the 5V pad? Thanks for any help, I know this is probably horribly obvious but most tutorials I find are just for homeowners installing them on their TVs and similar applications and they don't go into specific cases like this.


texts: AttributeError: 'NoneType' object has no attribute 'send' pigpiod

texts:
So I create an another program that can run stepper motor clockwise and counter clockwise with a ramp up and ramp down in there and adding limiter switch on GPIO 16 and 26 to stop the pi.wave_send_using_mode(wid2, pigpio.WAVE_MODE_ONE_SHOT_SYNC) giving a chain wave, this is my code:

import time
import pigpio

START_DELAY=600
FINAL_DELAY=500
STEP=1

GPIO=20

pi = pigpio.pi()

pi.set_mode(GPIO, pigpio.OUTPUT)
pi.set_mode(21, pigpio.OUTPUT)
pi.set_mode(26,pigpio.INPUT)
pi.set_mode(16,pigpio.INPUT)
#pi.write(21,1)
pi.wave_clear()

statee = 0
try:
    while True:

        pi.write(21,statee)
        pi.wave_clear()

        wf=[]
        offset = pi.wave_get_micros()
        for delay in range(START_DELAY, FINAL_DELAY, -STEP):
           wf.append(pigpio.pulse(1<<GPIO, 0,       delay))
           wf.append(pigpio.pulse(0,       1<<GPIO, delay))

        for i in range(500):
            wf.append(pigpio.pulse(1<<GPIO, 0,       FINAL_DELAY))
            wf.append(pigpio.pulse(0,       1<<GPIO, FINAL_DELAY))
        wf.append(pigpio.pulse(0, 0, offset))

        for delay in range(FINAL_DELAY, START_DELAY, STEP):
           wf.append(pigpio.pulse(1<<GPIO, 0,       delay))
           wf.append(pigpio.pulse(0,       1<<GPIO, delay))

        pi.wave_add_generic(wf)

        wid2 = pi.wave_create()

        #pi.wave_send_once(wid2)
        pi.wave_send_using_mode(wid2, pigpio.WAVE_MODE_ONE_SHOT_SYNC)

        if pi.read(26) == 0:
            pi. wave_tx_stop()
            pi.stop()
        if pi.read(16) == 0:
            pi.wave_tx_stop()
            pi.stop()

        time.sleep(0.75)
        if statee == 0:
            statee = 1
        elif statee == 1:
            statee = 0
except KeyboardInterrupt:
    print ("\nCtrl-C pressed.  Stopping PIGPIO and exiting...")
    pi.wave_tx_stop()
    pi.stop()

The problem happens when the motor runs around 5 - 10 minutes, it give an error message like this:

Traceback (most recent call last):

File "/home/pi/Desktop/ramp.py", line 49, in <module>
    if pi.read(16) == 0:
  File "/usr/local/lib/python3.4/dist-packages/pigpio.py", line 1401, in read
    return _u2i(_pigpio_command(self.sl, _PI_CMD_READ, gpio, 0))
  File "/usr/local/lib/python3.4/dist-packages/pigpio.py", line 989, in _pigpio_command
    sl.s.send(struct.pack('IIII', cmd, p1, p2, 0))
AttributeError: 'NoneType' object has no attribute 'send'

So, what the cause of error in my code? Is that cause by pi.read(26) and pi.read(16)? Is there any other ways to stop or terminate pi.wave_send_using_mode(wid2, pigpio.WAVE_MODE_ONE_SHOT_SYNC) at the middle of it process? thank you
small note: I set pigpiod daemon start on boot by folow (https://raspberrypi.stackexchange.com/questions/70568/how-to-run-pigpiod-on-boot   KimSJ answer), is the method of runimg pigpiod cause this error? thank you


texts: PCIe DMA transcation to multiple PC RAM slots from FPGA

texts:
An FPGA endpoint needs to needs to transfer large quantities of data to the host processor's RAM over DMA. So memory mapping to a single RAM might not be possible. Normally high end PCs or Servers have multiple RAM slots instead of a single one.

Can the FPGA transfer memory to the multiple RAM slots? If one RAM is full,
can the FPGA transfer data to the next RAM? If yes how is this switching
done by the PC Root Complex?
Does the chipset attached to the PC's processor have
multiple memory controllers(or MCHs)? Can the processor access one RAM and
keep one for FPGA DMA?

Any advice on this is appreciated. Thanks.


texts: What initial orientation do pick&place machines use when applying the "rotation angle"?

texts:
PCB assemblers require a file describing the component identifiers, the X and Y coordinates of the centre, and the rotation angle. I generate that file automatically from my CAD package (DesignSpark PCB). However the rotation angle that is generated is based on the footprint in the library. When the pick & place machine rotates the component based on the "rotation angle" specified, if it assumes a different footprint for angle=0°, then the component is going to end up the wrong way around.

Therefore, how can I be sure my CAD library and the pick & place database have the same assumption about the components orientations? I can only see one solution, which is to use the datasheet footprint figure (or pinout if not possible) as the initial orientation, but I would like confirmation and perhaps more details about how this works. Also, what happens then for passive components?

I looked around on the web and didn't find a standard, which is odd as in particular, both the designer and the assembler should agree on clockwise or anti-clockwise definition of the angle, even if I assume it is anticlockwise.


texts: How do I extend the ribbon cable in the photo?

texts:
It is a electronic cam lock for lockers. I want the dial pad to be further away from the locking mechanism.

Thank you for your help!


texts: Why we use two photodiodes as optoisolator or optocoupler?

texts: Why do we need two photodiodes in order to create an optoisolator or optocoupler? Many sources say that it is to compensate for the non-linearity of the diodes, but is there any explanation based on an equation or any scientific proof regarding this matter?


texts: Reading a high-speed rotary encoder with a Raspberry Pi

texts:
I'm trying to setup a Raspberry Pi to measure the position and speed of 8 DC motors that all have incremental quadrature encoders. At full speed (unloaded), each encoder ticks at 3.3 kHz. I assume that this means that I have to sample the encoders at >13.2 kHz to measure the position without missing any ticks. (Note: I only drive one or two motors at a time.)

The current board that I have has a MCP23008 I/O expander on it to sample the encoders, but I think that the I2C communication is too slow. With a simple Python script, I can sample a single encoder at ~1kHz:

from adafruit_mcp230xx.mcp23008 import MCP23008

encoder_address=0x20

# Initialize I2C
i2c = board.I2C()

# Setup encoder reader (I/O expander)
mcp = MCP23008(i2c, address=encoder_address)
encoder1a = mcp.get_pin(6)
encoder1b = mcp.get_pin(7)
encoder1a.direction = digitalio.Direction.INPUT
encoder1b.direction = digitalio.Direction.INPUT
encoder1a.pull = digitalio.Pull.UP
encoder1b.pull = digitalio.Pull.UP

# Read encoders
A = opt.encoder1a.value
B = opt.encoder1b.value

I also tried calling i2c-tools from my Python script, but this was insanely slow (~75Hz):

import subprocess as sb

output = sb.Popen("i2cget -y 1 0x20 0x09", shell=True, stdout=sb.PIPE).stdout.read()

I then tried a simple C++ program, but this only got me up to 1.5 kHz (reading the entire GPIO register):

/* encoder.h */

class Encoder {
    private:
        unsigned int device;  // device address
        int file;             // I2C file
    public:
        // Constructor
        Encoder(int device_address);

        // Read motor encoders
        unsigned char read_encoders();
};

/* encoder.cpp */

#include "encoder.h"
#include<iostream>
#include<sstream>
#include<fcntl.h>
#include<iomanip>
#include<stdio.h>
#include<unistd.h>
#include<sys/ioctl.h>
#include<linux/i2c.h>
#include<linux/i2c-dev.h>

Encoder::Encoder(int device_address) {
    std::string name = "/dev/i2c-1";
    this->device = device_address;
    this->file = open(name.c_str(), O_RDWR);
    if (this->file < 0) {throw;}
    if (ioctl(file, I2C_SLAVE, device) < 0) {throw;}
}

unsigned char Encoder::read_encoders() {

    // Write to GPIO address
    unsigned char buffer[1] = {0x09};
    if (::write(file, buffer, 1) < 0) {throw;};

    // Read GPIO register
    unsigned char output[1];
    if (::read(file, output, 1)<0) {throw;};

    return output[0];
}

My questions are:

Is there any way to use my current board to sample up to 13.5 kHz? I.e., is there any way to make my Python/C++ programs run faster?
Would it be better to connect the encoders directly to the GPIO pins? (I didn't want to do this initially because I have so many motors + other peripherals.)
Or, is it necessary to use a dedicated microcontroller? I.e., a microcontroller that keeps track of the relative position, which I can then periodically send to the raspberry pi.

I'm hoping to have a simple PID loop to control the speed of the motors + detect if they hit their limits and stop moving.


texts: Help Identifying a chip from a schlage handkey board

texts: Im trying to repair a schlage handkey which wont boot. I looked at the main board and noticed the chip below. The chip above it is the same part number but when I try to look it up I get nothing. How do I make sense of the markings?


texts: Can (or should) two voltage regulators be connected in a parallel configuration.

texts:
I have two 5 volt voltage regulators that I would like to connect to a 9 volt source in a parallel configuration.  Is this advisable, problematic, or even commonly done?

I have tested this configuration and noticed that one of the regulators gets hotter than the other.  Why is this?


texts: Is the book wrong about the Nyquist Sampling Criterion?

texts:
Is the following statement from a book wrong?

I thought sampling with twice the signal's highest frequency component would be adequate to completely recover the signal. But above it says sampling twice creates a saw-tooth like wave. Is the book wrong?


texts: potentiometer like rotation angle sensor

texts:
I have a set of flight simulator gauges which use a motor to move various indicators. The rotary position of the indicator is measured with a potentiometer like device, but it has 5 terminals instead of three. 1 is the wiper, and the other 4 are taps at 90 degrees on the resistive element. The resistive element is a full 360 degrees with no gaps. Measuring between any 2 of the taps gives about 2.8 Kohms. The rotation sensor was made by a NEI which has been acquired by Honeywell, which has no data for the part. These are old devices, wondering if similar devices in use today and how best to read them for determining the rotation angle.
Thanks!


texts:
I have seen many circuits which allow you to turn on an LED when a magnet is placed close to a Hall effect sensor. But I need a circuit that will turn off the LED when the magnet is close to the sensor. I cannot use a latch since the magnet polarity cannot not be changed. I was thinking about using a switching transistor with the sensor and LED but I am not usre how to configure this correctly. Any suggestions?

I am using an OH090U Hall Effect sensor.

Thanks!


texts: Can a PCB footprint be extracted from a solid model?

texts:
I usually just make a PCB footprint if I need it (Solidworks PCB, Altium, Protel99, OrCAD, etc). I'm an electrical engineer. I've seen very nice 3D solid models for some parts and I wonder if the PCB footprint could be extracted from the 3D model? I know very little to nothing about 3D models. I've seen the word "step" in lots of them and I think Solidworks can open them but besides that I'm clueless.

Could someone enlighten me pls? Thanks.


texts: Why CDMA is able to use whole band, when Wimax is subchanneled?

texts:
Original wording of question: What is fractional network access?

I'm having trouble figuring out what this term actually means, though I can find a ton of whitepapers about how some-standard-or-another means to support it.

I know it's related to the fact that wimax makes use of it's operating on subchannels, but 3g takes up an entire band. How would that work with 3g, then?


texts: What is the meaning of inferred absolute zero temperature? Why does the resistance temperature graph it is obtained from behave that way?

texts:
Studying basic direct current circuits, I've come across the term inferred absolute zero temperature on computation of resistances that change due to temperature. Based on my readings, I understand it to be a predicted value as the word "inferred" means. It predicts the value of the absolute zero temperature based on using a segment of the graph that seems to have a linear slope through extending that line to where the temperature is zero.
Although that is my understanding, I decided to ask it in StackExchange because I've searched for an explicit definition of this term and no source has ever defined it in such a way. You have to go through a lesson of resistances changing by temperature, find the terminology and read the paragraph to get it. I mean, for such a common lesson I can't believe that I couldn't find any source that just defines the terminology in a friendly manner or even have a Wikipedia article that defines it as there it gets a little more clear and precise.
Can anyone confirm this concept for me and define it more explicitly? By explicity I mean that say that the term means this, and not focus on some other topic where I have to read and it is only implied and that the terminology is just put there.

I got the image from this website.
https://enjoy-electrical.blogspot.com/2014/09/inferred-absolute-zero-temperature.html
Is it also right to say that, resistance and temperature in actual testing do not have a clearly defined relationship? Then their relationship also looks like a curve where a segment in the middle seems to have a linear behavior, which is where the concept of getting the inferred absolute zero temperature came from? Why does the resistance temperature curve behave like that? It's just that for me it kind of feels convenient that the middle segment has a linear behavior.


texts: How do I move a motor to a desired angle using a motor encoder?

texts:
So I have this project, the goal is basically to be able to make a motor move to rotate a set of gears and move a panel attached to a hinge to a desired angle. I have a motor encoder attached to the motor: (https://www.amazon.com/gp/product/B07LG18HBL/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1).

I have it hooked up to an Arduino/Motor Shield like so (please excuse the terrible wiring, this is just a proof of concept):

The configuration from the Motor Encoder is the following:

The biggest problem I'm having is that this system needs to control a system on board a satellite, so I need the motor to move to a desired angle based off a numerical input from earth. Once I get it to move, I know how to code it to the angle desired, but I'm struggling to get it to move at all right now. Do I need a separate power source for the motor? How should I code it in Arduino such that it rotates forward/backward an inputted value? There's not a whole lot of documentation on moving motors without a second encoder so I've been struggling a lot to figure this out. Any help would be much appreciated, thanks!


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I have a latching small signal <2A relay (V23079E1201B301) that switches between two audio signals. The relay has worked in about 10k boards over 7-8 years without much issue. We recently got a run done and 4 of 6 boards that we built the relay doesn't work at first - it passes audio in one position but not the other. But then after it switches on/off 15-25 times it starts working sometimes, and then after 30-40 switches back and forth it passes signal fine. If I power it off and check it a few hours later it's still fine.
I hear it clicking every time so I don't feel like it's sticking. It's almost like there's oxidation on one set of contacts and it eventually burns off. I'm a little nervous because I haven't experienced it before, and not sure if there's going to be long term reliability ramifications. I ran the issue by our repair guy and he says the relay never an issue with units coming back from the field.
Anyone else experienced this?
UPDATE: I broke apart a good relay (date code 2014), and one of the recent ones that had been 'exercised' a bit and now conducts (date code 2019). Comparing them they're super similar. A few differences, but nothing that screams counterfeit.
The obvious issue though is that I can see black stuff on one set of contacts (the moving contacts). It's worn off and gold again in the middle, likely from the exercise, but you can see black bands along the outside. Interestingly there doesn't seem to be any other decay or oxidation on any other part internally - or the stationary contacts. Maybe this suggests that it didn't become un-sealed, but that the moving arm has a defect with the finish. I'm not sure.
Going back and forth with the CM and manufacturer to try to get to the bottom of it. Thanks for all the advice.


texts: Why does the gain of a RC filter vary with input amplitude in LTspice?

texts:
I recently design an OTA based filter, and simulate it with LTspice IV. I was surprised to see that the gain vary with frequency (of course) but also with the input amplitude of the signal.

So I decided to simulate a basic RC filter to see how if the gain change with input amplitude, and the same thing happened.

Here is the schematic, with a variable AC amplitude (0.1, 0.2, 0.5, 1) :

And here is the plot :

I don't understand, the frequency response of a filter characterized by a transfert function V(out)/V(in) should vary only with frequency, and not with V(in), isn't it?


texts: Electrical Machine Design: Why do open slots are allowed in synchronous machine while they are avoided in Inductio Machine

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Why do open slots are allowed in stator and rotor of synchronous machine while they are avoided in stator of Induction Machine?

Because flux from stator to rotor (IM)  and from rotor to stator (in SM Cylindrical rotor), will have nearly same linkage.

I know large air gap between stator and rotor of synchronous machine make it less noisy. But what effect the shape of stator slots have on machine's performance.


texts: Transistor switch - extra resistor required?

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I am new to electronics and this forum, and am in the process of building a Raspberry Pi based homebrew controller.

Following the article in the eLinux wiki, here is the relevant part of my circuit:

The links to the datasheets are here: 2N3904 NPN transistor, SSR-40 DA solid state relays. There is no datasheet for the piezzo buzzer.

I have breadboarded this and it appears to function fine, however I notced that the spec sheet for the SSR calls for and extra transistor, between Q1's collector and the positive source:

Is this extra resistor necessary and what does it do in this circuit?
If I need to add it, then how do I size it properly?

Thanks in advance.


texts: Why a CPLD input pin behaves almost like an output pin?

texts:
I want my CPLD (a MAX II CPLD, EPM240, see datasheet) to accept an S/PDIF input using an optical receiver with TTL-compatible output.

I tested the receiver alone: when giving proper power and optical connection to an emitter, its output pin shows a nice waveform on the oscilloscope.

But when connecting it to a pin of the CPLD configured as input (pin 44, 3.3-V LVTTL, default) I stop seeing the waveform; instead the signal seems stuck to ~3V. Of course the CPLD receives no data.

Suspecting that the CPLD pin was accidentally configured as an output, I disconnected the receiver and connected the pin to a 10kΩ pull-down resistor. I'd expect almost 3V if it were an output and almost zero if it were an input, instead I measure a voltage of 1.6V which is something in the middle.

So why is the CPLD behaving so weirdly with a digital input, almost behaving like it was configured as output?


texts: Trying to ID this component & where to get a couple of them? Is it a varistor?

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Here's a photo I made to show back and front of this thing.
I think it's a varistor.

The main body is roughly 8.5mm in diameter.

I straightened the two legs but I think they are SUPPOSED to have a couple of "twists."

Anybody know something similar in values? It goes onto an old power supply circuit board from around 1996.


texts: Powering Two Motors through a Three Conductor Cable

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I am working on a custom pan and tilt system in which the "pan" and "tilt" motors will be powered with a pair of PWM motor drivers. In other words, each motor will have its own driver. The drivers themselves will receive commands from an arduino nano, which in turn will receive control inputs from a 4-way switch joystick. The motors will only be powered one at a time, since the joystick is gated.
So far, this is pretty easy. The tricky part is that the cable I'm constrained to using only has three conductors available for the motors! The two motors will have to share a conductor. I'm struggling to come up with ways to power the motors, since sending power to one of them will, in most configurations I've come up with, also send power to the other motor.
The best I could come up with was to run a lead from each motor through an NC switch on the joystick such that the circuit from the stationary motor would be shorted out every time the shared conductor receives power. In my head, this makes sense, but I have a feeling that this might fry my PWM drivers.

My other idea was to use four logic-level NC relays and run the motor leads through them on the controller-side. Then, I could use code to completely disconnect the "stationary" motor from its driver every time the other motor is powered. But, now I'd have to deal with some delays every time I quickly switch from one motor to the other. For example, if I go "up" and then "left" in quick succession, it would take time for the relays for the "left/right" motor to turn off and close the circuit.

What do you guys think? This seems like the type of problem that a clever switch arrangement could solve, but I can't seem to crack it.


texts: Inductors in series with different currents

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I'm having trouble finding the differential equation that describes the circuit, at t=0 10A flow through L1 and 0A through L2, since current can't change instantaneously. But they're in series so they should have the same current. It seems like I can't find the differential equation using i(t) like I normally would in a series circuit because I don't have a value for i(0). So, how do you solve this?

And thinking about it, the same could happen with capacitors in parallel, how would I solve that as well?

This is from Linear Circuits - Ronald E. Scott.


texts:
I use an AUX male to XLR cable to play music out of a PA at gigs. This seems to work so far.

At a recent gig, the sound person mentioned that the cable I was using should not exist, and that I should pick up a direct box instead. So now I'm here, trying to find out why I should be using a DI box.

After doing some research on direct boxes, it looks like they allow a signal to travel over long distances with little resistance [which I assume degrades the signal]. Also it appears that DI boxes reduce humming through the PA.

Am I missing out on these benefits by using an AUX to XLR cable? Are there other benefits I might be missing out on by not using a direct box?

Here's an example of the type of cable I'm currently using: https://www.amazon.com/GLS-Audio-Cable-Stereo-Male/dp/B006LRPF7Y


texts: DC consumption translation to AC consumption

texts:
I've a battery charger that can output 9v and 2.5A and I use full power from it that is 22.5W.

Can I translate this power consumption from DC to AC current?

My AC is 220V 50Hz, so I'll consume 22.5Wh when I charge my battery like a big lamp?

EDIT:

On device is also written 110V-240V 50Hz/60Hz and Max. consumption 0.68A related to AC.


texts: How to make a piezo speaker louder with 5V?

texts:
I have connected a tiny piezo pc speaker (https://sktechworks.ca/wp-content/uploads/2017/11/Speaker.jpg) to an arduino and used to tone command to play a simple melody in repeat (square wave only since I didn't use a DAC).
But the speaker is very quiet. I have used a speaker like the green one here:

but it is not siginifcantly louder (I need a piezo either way).
I then tried to just connect it to 2 digital ports and just inverted low and high between them, which did make it louder, just not enough.

So here my question, with the same voltage is there a way to produce a louder sound?
I just need a sound  can clearly hear through a few walls.
Because I have a usb speaker (which is 5V) and that one is signifcantly louder.


texts: P-channel or N-channel MOSFET configuration for safety circuit cutoff

texts:
I'm working on a hobby project and bought some cheap linear actuators with motors in them. Due to the terrible motor speed/torque, I switched them out.  Now I have to implement a safety feature to kill the power to the motor whenever a limit switch is actuated in the device. (It tears up the device if it goes too far.)

Below is the project setup, but this is what I think i need to do.  I need to a N-channel power MOSFET to control a P-channel MOSFET.  The first one can be this one and will control a 12v current from the power supply to trigger a second MOSFET.  This second one is what will kill the power to the motor whenever a voltage is applied. I think i need to use two because the voltage difference between the arduino and the 12vdc power supply is too much to trigger the P-channel MOSFET by itself quickly enough.

How off am I?  I'm a hobbyist, but i'm trying to design it right before building it.

Project Setup

Arduino board
12vdc brushed motor that normally pulls 15-20 amps
H-Bridge Relay from Arduino to motor, for control, but not safety shutoff.
   http://www.vexrobotics.com/217-0220.html
12vdc power supply
Linear actuator with gearing and two limit switches at either end of gear.
(If either one is hit, then it breaks the circuit. setup in series.)
Example actuator that looks similar but isn't.

simulate this circuit – Schematic created using CircuitLab

To make it clear: This is a safety shutoff and will only be used to protect the motor from destroying the actuator if there is a bug in the program actuating the device.  I can flip the power manually if the power gets cut because of this new circuit.  I just can't rebuild the gearing.


texts: Why sample current via lopsided resistive divider?

texts:
I'm studying the constant-current circuit of the Agilent E3610A 15V 30W DC Bench Power Supply. The entire schematic is at the end of the user manual, but I've redrawn the parts of interest here for clarity.

The current reference supply provides a reference voltage of 2mV/mA of current limit. Its level is adjustable via VR19, a 10-turn pot on the front panel. This part of the schematic is simplified to reduce max output and I'm showing a TL072 instead of the original LF411, but it's a pretty straightforward inverting amplifier.

The current error amplifier is also a straightforward inverting amp driving the control node. It takes its input error signal from a resistive summing point formed by R23 and R24. When the current is being limited, the value of the summing point is close to 0V. Note that S+ is ground, even though it's the positive output of the supply. The overall DC supply is an inverting amp, so somewhat counter-intuitively, the output voltage is S-.

My question is about the circuit around the current sample node labeled i_sense. A voltage of 100mV/A is developed across R2, which acts as the current sampling resistor.

Unexpectedly, to me at least, the current sample voltage is connected via a lopsided resistive divider (500k/500.001k) formed by R27 and R34.

What's up with that? Why isn't R23 connected directly to the i_sense node?

After studying it for some time, all I have is some vague guesses:

It has something to do with behavior when the output is shorted ...
It somehow shunts the sampling current around the current sampling resistor itself to increase accuracy

.. neither of which I'm able to make work in my head.

Can anyone help me understand? I'm pretty sure it's this way for a good reason :)


texts: Can I create a uniform magnetic field with an n52 magnet?

texts:
I want to build a ribbon speaker and I've read that one of the greatest sources of distortion in these types of speakers is the non uniform magnetic field along the length of the magnet. I've also read that there are ways to make this field more uniform but I haven't been able to find out how.
Can anyone give me advice on this topic?


texts:
I am using 4 2 cell 5000mAh 60C LiPo's in series to drive a robot I am building for Robot Wars (Scorpinator - look out for it).  Each battery came with a balance cable built into the discharge cables but one of my chargers is capable of charging 8S Lipos (which when connected together these are) so I want to try and charge all batteries together to save time but connected together I end up with an 8S with 4x 2S balance cables - no good.

I have searched all over to see what a 8S balance cable should like e.g. which cables connect to which pins, I have found numerous diagrams but none of them specifically show 4x 2S to single balance cable (I found examples of a single 8S battery and 2x 4S).  If and when I get the balance cable sorted should I charge in series or parallel?  Is there a formula that explains the why and how of balance cables that can be used for any LiPo configuration rather than having to keep a library of different configs?  Ideally I want to understand how the cables connect rather than just find a cable gadget that connects 4x 3pin balance cables to a 9 pin (not that I could find one anyway - I tried!)

Cheers

Lee


texts:
I use a travel adapter to plug my microwave (UK plug) into an Austrian, European outlet. The other day, whilst the microwave was switched on but not cooking anything (ie the magnetron was not powered), I heard a crackling noise and when I pulled out the plug, the adapter had melted around one of its pins. What happened? Why did the 13A fuse on the microwave plug not blow?

The adapter is CE certified and has a "10A / 16A - 240 V~" rating (what does this mean?).


texts: How do I properly ground AC terminal blocks on a DIN rail and respective back plane?

texts:
I am building an electrical panel with AC and DC supplied power. My AC ground wires connect to a green DIN rail connector which has metal on the bottom of this terminal and connects to the DIN rail itself (which then is connected to the overall enclosure via back plane).
If I have 3 separate DIN rails all mounted to the same backplane, do I need to ground each individual (6 inch) rail? (for example: Connect AC ground to only ONE green DIN terminal block (which grounds the entire backplane) OR for each DIN rail (all on same metal back plane), attach a green ground DIN block to each individual 6 inch rail and wire the AC ground line to that particular rail?
NOTE: Schematic shows this terminal block only being ground 1x...I have grounded this 4x for 4 separate DIN rails (ALL on the same backplane)
Schematic attached (see RED outline box for ground terminal block).


texts: Filter capacitors to avoid pop when hitting footswitch

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This is an audio circuit question.

I have two line level signals going into two DIs going into a PA.

I want to craft a custom passive mute switch, sometimes when debugging feedback when performing live I have to unplug the line signals from my DIs. It would be much easier if I just had a button to act as a mute.

My circuit is just 2x 1/4" jacks in, 2x 1/4" jacks out, and a DPDT footswitch, simple as can be. When I press the footswitch, the output jacks are simply disconnected from the input jacks and left floating. The input jacks are connected to the two commons of the DPDT footswitch.

I would like to avoid a popping sound when hitting this footswitch though, as a loud pop can potentially blow PA gear.

So my thought was to have 2x capacitors inline with the two output jacks, since caps let AC through (the line level signal) but filter out DC.

Would this work? How do I chose a value? I was planning on just using a 22 nF, which seems like it can pass most audio frequencies without too much bass attenuation.


texts:
I would like to know how does MCU provide it's output current. here is a little drawing of my assumption (simplified) of how a pin is functioning when it is set to output.

Basically it is a transistor that allows current to flow or it doesn't. it cant be something else, but what actually bothers me is V in to the mcu. Does MCU provide an output using Vcc input directly or this input is going through some other internal components.

If this is a transistor and 5v goes through it, do i get that Vce drop ? which is 0.2V. and therefore i actually get 4.8 volts on my pin ?

If i am performing some calculations how would apply a Kirchhoff rules to a circuit with micro controller if i don't know nothing about its internals, only datasheet data.


texts: Momentary to Toggle Switch for Tiny Application

texts:
I need to put a circuit into a pen to turn on and off an LED using 3 AG3 or LR41 batteries connected in series. The LED will be on the tip of the pen and the switch will be on the side surface of the pen. The smallest switch I can found is DPDT Micro Push-On Push-Off Switch but it's too protruding.

There are momentary switches which are small enough but the LED need to be toggled on and off, not just momentarily on and off. So I need a way to convert momentary switch into 2-state toggle switch (once I press it, the output is continuously on, and then if I press it again, the output is continuously off).

Many circuits I found need mcu, transistor, and capacitor. Those circuits still take up too much space for this tiny application. Some use a 555 timer chip, but apart from taking too much space, it also consumes some power when the LED is turned off, so it's not good for this battery-powered application.

Then I bought several pens which uses a momentary switch to toggle LED on and off. They have laser diodes too actually but it's not a problem.

One pen works like this: once I momentarily push the switch, the LED turns on. After that, if I momentarily push the switch again, the LED blinks about 10 times per second. After that, if I momentarily push the switch again, the LED turns off.

Another pen that I bought has a white LED and a UV LED. It uses only one momentary switch and it works like this: once I momentarily push the switch, the white LED turns on. After that, if I momentarily push the switch again, the white LED turns off and the UV LED turns on. After that, if I momentarily push the switch again, the UV LED turns off.

Then I tore those pens' case to see the circuits they use. What I found are these circuits:

There's a lump in each circuit. One pen's circuit has a white lump (which I have corroded it using a cutter so it looks rough), and another pen's circuit has a black lump. I haven't done anything to the black lump. Those lumps are at the back of those momentary switches toggling LED on and off. The other switches are just there to momentarily turn the laser diodes on.

After I corroded the white lump, I found no discrete component in it (no discrete capacitor, transistor, nor mcu).

By the way, the switches of the circuit which has a white lump that I have corroded works by connecting inner circular copper to the other circular copper. The small spring will be connected to the negative pole of the battery, and the uninsulated anode of LED is connected to the positive pole of the battery via the metallic case.

The circuit which has a white lump that I have corroded is the one that has UV LED and a white LED. The one shown in the picture is the UV LED. Its white LED cathode is connected to that terminal directly above 1,5 cm in the ruler in the upper picture, and it's anode is connected to the metallic case.

The golden cylinder is the laser diode's case. The black chip under the laser diode is a surface mounted resistor.

Do you recognize those lumps?


texts: LED Strip / Resistor Heater + Driver Circuit

texts:
For my astrophotography equipment, I need to construct a dew heater and a flat field generator.

A dew heater is simply a bunch of resistors connected in parallel such that each resistor outputs about 0.3W of power, and spaced roughly 1cm apart. Typical dew heaters run off 240V-12V AC-DC adapters and have controls to vary heating.

A flat field generator is a box with LEDs or LED strips mounted on one end, and a diffuser (white perspex) on the opposite end to create an even field of illumination. Typical flat field generators also run off 12V and have control to vary the brightness of the panel.

The design I came up with is this:

Here, the transistor is biased through a potentiometer. The same design would be used for the dew heater by replacing the LEDs with resistors. However, I have a couple of issues with this:

I would like to have a linear (or almost linear) relationship between potentiometer value and brightness/heating (current through collector). In simulations, I can tell that for this circuit, the relationship is not linear. Is there a simple way to rectify this?
For the dew heater, I require it to produce about 5W of power max. How can I calculate the values of every resistance in the diagram to ensure this? Also, since the resistors are in parallel, the sum of all currents will go through the transistor too. Is there a generic part number for a transistor that would be better suited for this task instead of having a fried transistor? Also, how much should the power supply be rated for this? I have an option to use either a 5V or a 12V power supply.
For the flat field generator, the problems are even worse. Linearity issues aside, my panel will use LED strips like THIS one. I can't find a datasheet for this LED strip but it has 18 SMDs per strip and runs on 4V. I think all 18 LEDs would be wired in parallel since white LEDs have a forward voltage of about 3.3V. If that is the case, each strip would draw about 20mA x 18 = 360mA. My panel will house up to 25 of these strips. If I connect them in parallel, they will draw 9A of power! Is there a better way of doing this? If not, are there any generic transistor part numbers that will handle this amount of current, or will I have to break the circuit up into multiple drivers, each driving a few strips? Also, I doubt I will find a 12V power adapter rated 9A.

I know the design is a basic one that you'll find anywhere on the internet. If any of you has a better/more precise solution, I would love to hear about it.


texts:
I have seen a few examples of a low voltage warning LED using two NPN transistors, like this;

My question is, can this be simplified further using only one PNP transistor, if R2 were a value so that the PNP base current was low enough the transistor would be 'on' below a set voltage? Something like this;


texts: How can I design a Caesar cipher encrypter and decrypter without using Non-programmable circuit components?

texts:
My device should be able to take an input from A-Z and another input to from 0-25 and finally a Encrypt or Decrypt option. Currently I have given A a code of 0000, B 0001... so on and the output will be the result of a 4-bit adder (for encryption). I realize my circuitry skill are not profound, hence any form of support would be appreciated. Another challenge is to display each of the letters after the output is received.
 p.s. I also realize the circuit displayed is primitive and probably incorrect.


texts: How can I determine the order of filter?

texts:
This is my first study about signal analysing. I'm very confused about filter order.

My problem is how can I know whether its 4-th order, 12-th order, or 2nd order like the book says so? I'd like to know the process behind it.


texts:
After solving for a system of complex equations, I got the following currents:

$$I1= -.80669-.35675j$$
$$I2= -1.8546+1.30730j$$

Firstly, I found the current magnitude:
$$|I_1|=.88205A$$
$$|I_2|=2.26887A$$
After that, I plugged into the calculator $$tan^{-1}(complex/real)$$

So I ended up with $$\theta_1=23.85678°$$ $$\theta_2=-35.17946°$$

However, the phase angle part of my answer is incorrect; my current magnitudes are considered correct, so my complex current values are correct. Is there something else that I need to do to my phase angle values to get them to be correct?

P.S. I know that values for I1 and I2 would be in the third and second quadrants, respectively, but the answer requested is between -180°< theta <180°, so it wants the values that the calculator outputs.


texts:
Please, I need help with this schematic.
I would like if there is something wrong on this schematic about Raspberry Compute Module 4 Carrier PCB design. I will only use PCI interface and some GPIO's. I want to flash eMMC with USB 2.0 USB and supply with the same connector. Should I add RPIBoot control with a jumper?
Thank you so much.


texts:
To begin with i have an AMD Sapphire Radeon R9 270 and it worked fine for a year and a half.

I was doing some cleaning on my pc (cleaning the heatsinks and things like that) and when i connected everything back in place and proceded to turn the PC on; i got no display, i noticed it started smelling like melted solder, and when i looked inside my pc I saw the capacitor glowing red, then i shut the pc off and it now looks like this

I want know if you can help me find the exact one to buy in order to replace it

Thanks in advance


texts: measurement of the number of LUTs-FF pairs and logic cells under most efficient and inefficient condition

texts:
Can anyone tell me how to get the number of the LUTs-ff pairs and logic cell used under most efficient and inefficient condition in my ISE Design Summary.

I can see there are data of 'Number of Slice LUTs' and 'Number of Flip-flops', so I'm just thinking if the sum of these 2 data is the amount for most inefficient condition.


texts:
I'm currently working a project involving the VEML6040 color sensor (Link to application note). I am reading through the application note and stumbled on the graph depicted below. As far as i understand, this graph is about the responsivity of the sensor vs the wavelength of the light that it recieves.

However i don't understand the unit on the y-axis. It says relative responsivity (uW/cm^2). And then it says 2000,4000 etc.. How should interpret this? Does this mean that for example the blue channel will output a value of 6000 when light with a wavelength of 450nm and an intensity of 1 uW/cm^2 hits it?


texts: What's a safe method for determining the switching frequency of a blackbox ACDC converter?

texts: My project uses an off-the-shelf ACDC converter that conceals design details from  such as switching frequency (or SF range). It's 24 V output rated to 5 Amps. I want to measure it's switching frequency but was advised against probing the device with an oscilloscope since it can be dangerous. Any advice how I can accomplish this safely?


texts:
My understanding is that inductors in a dc circuit act like a wire and don't do anything.

So what are the ones labeled FLxx in this schematic for? Could they be replaced with a simple wire and have no affect on the circuit function?


texts: Does a trace with via handle more power?

texts:
Eventually I see power traces on both sides of dual layer PCBs that have lots of massive vias, do the vias help the traces handle more power? Does it increase heat dissipation and/or decrease resistance?

I sometimes see them in PCBs with the same trace on both sides, so the via's function apparently is not to carry current from one side to another.. is it adding thermal mass or..?

Is there a rule of thumb/graphs/calculations/application notes for this? Or is it more empirical/case specific?

Info about vias for PCB heatsink pads for power ICs is quite common but I couldnt find much about traces.

I know there are other methods of increasing power handling and heat dissipation for traces, but I'm specifically curious about this method.
I think I'm not referring to PCB stitching of RF planes.


texts: What effect does the frequency have in PWM?

texts:
I am programming a PWM controlled breathing LED with RPi.GPIO Library in Python on my Raspberry Pi 2. The problem is I understand what the frequency does and what the duty cycle is but not how these play together.

Can somebody explain PWM to me? :)
Thank you so much


texts: 1S or 2S li-ion battery charging design for ESP32/Nextion device

texts:
I am designing a portable battery powered device and trying to decide on my battery configuration. It will use an ESP32 chip with a few additional ICs, which will draw about as much current as an ESP32 dev kit, I'm guessing about 200mA peak. It will be constantly running Wifi and will not use Bluetooth. It will also have a Nextion 3.5" LCD which runs on 5 volts and draws 150mA. So we'll say the device will draw between 350mA and 500mA total. I am deciding whether to use a one cell lithium ion battery or a two cell.

If using the one cell, I would use a charging IC such as MCP73832 and charge with USB input, then use a boost converter to boost the 3V-4.2V battery output to 5v for the LCD. Then a linear regulator from 5V to 3.3V for the ESP, or otherwise just go from the battery to a linear regulator to drop to 3.3v, and the ESP should be able to run on just 3 volts when the battery voltage drops down below the 3.3V.

If using the two cell, I would use a charging IC such as MCP73842 and charge with 9V wall adapter input, then use a linear regulator to drop the 6V-8.4V battery output to 5v for the LCD and take that and use a linear regulator to drop to 3.3v for the ESP.

I would also prefer to use linear regulators as opposed to switching regulator to keep ripple noise down since I will be measuring small signals with an ADC, but if using one cell I would have to use the boost converter of course to get the 5V.

I will probably use one or two 18650 batteries at 2500-3200mAh each, I would like to get at least 5 or so hours use from the battery and more would be better. If using the one cell maybe a 5000 mA block style battery to get more capacity. What I'm worried about is being able to power everything once the voltage starts to sag with the one cell. I've tested approximately what my load will be when connected to one 18650 Ultrafire, when it was fully charged at 4.2V the device powered on, but at 3.85V it wouldn't power on. I didn't test any voltages in between. I'm aware that the Ultrafire 18650s are not the best, I would use a Panasonic or similar name brand.

Should I go with the one cell or two cell? Right now I'm leaning toward the two cell. And does my design sound right or need improvement?

Thanks a lot for any help.


texts: Wanting to power ~20 LED's; which small, common, & commercially available battery will give the longest life?

texts:
20 White Leds, each rated at a nominal voltage of 3.4V and a nominal current of 20mA.

I want to use battery power exclusively. I'd like to use commercially available batteries. So AA, AAA, 9V, etc.

Not really looking to make my circuit any more complicated than a magnetic reed switch, resistors, and the leds themselves.

My two questions are interdependent and so would like to hear your thoughts. 1) best way to wire them series/parallel and combination thereof 2) best battery source for the longest life using common commercially available batteries (includes common commercially available Li-ion batteries (AAA, AA, etc.))

I used a calculator which produced the following results:

ignore V & R values in schematic, the left one was a suggested repeating pattern for the 4.5V source for all 20 leds, the right was suggested for 9V source which repeated for the remaining leds

simulate this circuit – Schematic created using CircuitLab


texts: Meaning of a small rectangle in schematic drawings

texts: What is the meaning of the rectangle at the top of this schematic?


texts: Measuring 24V AC input state with microcontroller

texts:
I need to measure the state (on/off) of a 24V AC line that is currently powering a solenoid valve. The microcontroller will take over the control of the solenoid through a solid state relay, but I need to know if the line is being powered or not, for the control logic.

I am planning on using a half-bridge to rectify the signal. The signal is then passed through a passive low-pass RC filter to remove the 60Hz line frequency component. Lastly, a voltage divider is then used to reduce the signal voltage to the microcontroller's logic level.

I will probably also use an isolation transformer before the rectifier diodes for safety. Switching speed is not particularly important, so the filter can be tuned for a pretty low cutoff.

It would be simpler to use a relay, but I would rather not use one for this application. Does this seem like a reasonable approach? Is this safe considering that the circuit will be properly built, enclosed, and grounded?


texts: Project - How to onstruct a circuit to introduce and control a 0-300ms delay in an RF feed from a Sky Box to multiple TV sets?

texts:
Just bought a new TV!
It's "smart" but where my previous dumb TV didn't, my smart TV introduces a delay over HDMI from my Sky+HD box compared to the RF2 output which is wired via coax cable to the other 3 TV's in the house. My research tells me this is likely due to the way the smart TV decrypts the HDMI feed.
My 3 dumb peripheral TV's do not have any facility to introduce a delay so I have to ensure the volume is low on the kitchen TV otherwise there is a fiendish echo.
I have previously enjoyed electronic construction and am intrigued to know if I have any chance of being able to construct a circuit that could introduce a delay into the RF feed, preferably the powered RF2 output from the Sky box.
I believe coax cable can be modelled to the following circuitry:

It therefore seems to me that if I was able to calculate values for these components, I might be able to introduce a variable phase shift that would solve my problem. That is, I might fool the feed to think that the cable was a mile long. Perhaps that would result in signal loss/degradation?
Can a 200ms delay be done? If so, how?
I have found that one can purchase HDMI splitters and modulators. Perhaps that is a more logical approach, for example, that I distribute the split HDMI feed over the coax lines? However, I suspect I might still end up with asynchronous results.
I really have done a lot of research and will do more, but would value all opinions and advice. Thank you in anticipation.


texts: Peak Inverse Voltage of full wave rectifier in case of different diodes

texts: Does the peak inverse voltage remain the same for all the diodes in a full wave rectifier, when we are using both germanium and silicon diodes in the rectifier circuit?


texts: lithium ion battery capacity loss across different storage charge levels over time

texts:
We can see this simple chart in many places, however I am curious to know how the numbers work out for different starting charge levels than 40% (3.8V, ish? for li-ion).

For example, how much worse is 10% charge level than 40% charge level? Importantly, is it preferable to leave a battery charged at 100% or at 10% (as these are usually the states that we find cells charged to)?