texts:
I'm working on a project in KiCad.

I have a connector that has multiple connections for GND, +5V, and +12V (all set to type: Power Output) in order to increase the maximum current. However, I don't know how to tell eeSchema that I want to do this.

When I connect them all to GND, +5V, and +12V (respectively), I get the error ErrType(5): Conflict problem between pins. Severity: error and it tells me that the power pins from the connector are connected to each other - just the way I want it.

Is it possible to acheive this without editing the connector schematic or should I change the pin types to passive for all except one on each plane?


texts: I want to convert 0-5 volt to 4 to 20 mA current loop through a self powered load

texts:
I have done this circuit diagram in Multisim where the R1 is the variable voltage source and the load is represented by the black box. There are two problems:

If I change the load resistance the output current changes.
If I use 9V to 5V converter the output current is beyond my control.


texts: Mosfet or bjt choice for low voltage joule thief application

texts:
I make solar energy harvester using joule thief circuit with a small solar cell as the input. The output voltage from the solar cell is 0,5V. But the generic transistor, exactly silicon material need for 0,7V to start conducting.

Is there any transistor type (mosfet or bjt) that work with 0,5V or lower for my project ?

Thanks you,


texts:
I want to operate a UV LED at continuous 20mA for one week. However, when I measure the LED intensity with a photodiode (see image), I find that the light intensity changes continuously in time. I would like to ask you how I can reduce the light intensity drift that I am observing.

The LED data sheet is: http://static.vcclite.com/pdf/VAOL-5EUV8T4-LED-5mm-UV.pdf. I am operating it in series with a 461.6 ohm resistor and a 12 V AC-DC power supply. The voltage drop around the LED is 3.2 V, the current is 19 mA.

I am measuring the light intensity with a photodiode connected to an Arduino. I attach a picture of the circuit and the graph of light intensity (photodiode voltage output) vs time (hours).


texts: How do I prolong the reed switch output time

texts:
I put a reed switch ( https://en.wikipedia.org/wiki/Reed_switch ) on the handle of a measuring wheel (perambulator). The reed switch will be activated up to around 20 times per second (every 50 ms). The sampling rate on my data acquisition is 200 Hz (every 5 ms). The DAQ is made with an IOIO OTG ( https://en.wikipedia.org/wiki/IOIO ) and the analog input I use can handle (0-3) V. Should I go for a Schmitt trigger or do you have a more elegant solution on how to have a long enough output signal from the reed switch to safely sample it?

I am only interested in the time between activations of the reed switch. I plan to put a LED and a beeper to get a short noise and a flash of light for each. The input level to the IOIO OTG will be the 0.7 V due to the LED. There are 9 mm diameter neodymium magnets mounted on the wheel and the wheel has a circumference of 1 m. I put 10 magnets on the wheel and the approximately highest speed I will measure is 2 m/s. Then the wheel rotates twice per second and thus I have up to around 20 activations of the reed switch per second.

Since we know the circumference of the wheel (1 m) and the 10 magnets are evenly spread out, knowledge of the time between activation of the reed switch will give a good approximation of the speed.

Edit: Changed the text regarding the placement of the reed switch. The reed switch is next to the wheel and the 10 magnets are on the wheel. I want to have 10 magnets to get a good estimation of the walking speed of the person holding the measuring wheel.

I guess I could use a digital input instead. I didn't consider it would be a better option in this case.

Maybe I should clarify what I mean about 1 m circumference and 10 magnets. Between every reed switch output the wheel has travelled 10 cm. If the wheel rotates 2 times per second at fast walking speed (2 m/s) the reed switch will close 20 times per second.


texts: I am planning to design a custom FPGA PCB. the PCB will contain sensors. I need to read the output of the sensors and process them in the processor. I have completed many projects using FPGA's, but this will be my first custom design where I need to consider the hardware configuration as well. I have done research lately, but it is still hard for me to start from a point. Therefore I am asking you to help me and other individuals who wants to design their custom FPGA what are the points they need to consider at each step. Are there books/online resources which can help us in this process? I will also make a document after I have finished my project so people can make use of it.


texts: What is masking-time and chattering in rotary encoders?

texts:
In the datasheet of these encoders there is always a chapter mentioning masking-time and chattering.

I couldn't find any tutorial on this. What are these definitions about?


texts: Help Interpreting "Max light exposure" rating for TSL1406R

texts:
I've purchased a TSL1406 Linear Sensor Array to read the position of a laser dot. The "Absolute Maximum Ratings" section in the datasheet specifies "Maximum light exposure at 638nm" as 5 mJ/cm^2. Being inexperienced with this sort of sensor, I would have expected a "max light" rating to be given in terms of something like mW/cm^2 and I'm not sure what to make of a mJ/cm^2 rating.

Q1: Does this mean that "something bad" will happen if the integration time multiplied by the mW/cm^2 of my laser dot exceeds 5 mJ/cm^2?

Q2: What is that "something bad"? Will the integrating capacitors fry? Or will they simply be unable to accumulate anymore, resulting in bad readings for that particular frame?


texts:
At work we have a machine that is used for testing and calibrating force sensors. It basically consists of a huge lever that is actuated by an electric motor with a gear reduction and a calibrated reference pressure load cell. Right now, the machine is driven by hand by turning the voltage knob of a benchtop power supply that is directly connected to the motor, while reading the mV output of the pressure load cell on a benchtop voltmeter. For each calibration, the required forces are converted to the mV reading of the reference load cell by an Excel spreadsheet. The sensor under test is hooked up to a power supply and it's output is measured with another benchtop voltmeter. The machine is then driven to each point and the result is noted by hand.

We want to automate this machine. The measurement part is pretty straightforward. Our Fluke benchtop multimeter has an RS-232 output which I can use to capture the results.

The part I'm not too sure about is the position control loop for the machine. I imagine some kind of PID loop controlling the machine. I've done some PID control before, but mainly for heating systems. I also know just enough about control theory to be dangerous ;)

I imagine a µC that reads the reference load cell via an ADC and drives the motor via a current DAC. Why a current DAC? While driving the machine by hand, I quickly learned that one needs to give regular "pulses" to the motor to keep the machine at a specific force value to ensure a stable measurement. This is especially important when calibrating sensors with integrated amplifiers, because those amplifiers need to be held at fullscale load for quite some time (15..30s) while they do their thing internally. So I think a constant current needs to be applied to the motor to ensure it holds the required torque.

Does this sound plausible to drive this kind of machine? Is this kind of system straightforward to control by PID? Any suggestions on what properties I need to check to ensure a smoothly running control system? Is a current DAC the right choice for this application?


texts: If we attach two voltage source of same value than what happens? I mean what's the difference between using a single voltage source and two same valued voltage sources in parallel? As they both supply same voltage in the circuit.


texts:
I'm using a mosfet for powering an Arduino mega 2560 on and off. The current drawn is less than 500mA with a 12V battery.

I chose the IRF7457Pbs (RS 543-0888), with these features:
VDSS - 20V
RDS(on) - 7.0mΩ
max ID - 15A

I measured the voltage drop on D-S:

Vin=9.40, Vout=7.55
Vin=12.15, Vout=10.24

This is too high for the mosfet specifications.

I'm using the mosfet driver UCC27517DBVT, (RS 774-1367), with Vdd=12V, IN+ TTL logic level from Arduino. The resistor at the gate is 5.1 ohm.

Why is the voltage drop too high?


texts: Autodesk EAGLE Routing of STM32WLE with tiny UFBGA73 package

texts:
I would like to do the routing of the stm32wle5jbi6 chip that comes in a tiny UFBGA73 package. Please see the datasheet here:
https://www.mouser.de/datasheet/2/389/dm00648230-1799409.pdf
The dimensions are provided on p128 and p129.
I'd like to send the PCB for manufacturing to pcbway.com and they have a minimum trace width and spacing of 4mil:
https://www.pcbway.com/capabilities.html
But they recommend 6mil for both trace width and spacing.
Looking at my board file:

I see that the size of the solder mask (tstop layer) might be the problem. I cannot do any routing in the chip. What do you think about just reducing the size of the soldermask, what is the minimum distance it should have to the cream layer? Can I eventually not use it at all?
EDIT: Please see more details on the dimensions (in mm) here:

Thank you!


texts: Making a schematic in KiCad; how to represent connections from another circuit board?

texts:
I'm using KiCad to design a circuit for my latest project. This board includes a number of transistors whose bases are connected to off-board signals.

What's the proper way to represent this, so when I build the netlist and PCB, these off-board signals become header pins or pads.

Yeah, newbcakes here...

EDIT -
I found a 12x1 connector which does exactly what you think it does. Now, that happens with this when I convert the schematic to a PCB, I don't know. Stay tuned...

EDIT 2 -
I have learned nothing happens to the 12x1 connector automatically.  Instead, on the next step towards pcb-ing, you have to tell KiCAD what everything is.  I did and it worked fine, though there weren't many options so I selected a 7x2 DIP.  I'm 95.982% sure I can make what I need, however.  This is the least of my worries, lol.


texts:
I'm relatively new to electronics, and I'm trying to make a thermometer using a LM335 temperature sensor. By reading the datasheet I thought it was simple, connect up 5V to a resister, then to the V+, connect up V- to GND, and I should get somewhere just below 3V when reading the V+ pin.

However, when I do this, I'm actually getting 4.08. I've tried two different sensors, so I'm reasonably sure that it's not just a DOA.

Any ideas about what I could be doing wrong? What I can do to try to work it out?


texts:
I am making a small project that has a li-ion battery for power.  I need to be able to charge the battery within the circuit and am trying to find the correct amperage to charge it with.  The battery is a 3200mAh li-ion cell (3.8V), and I am wondering what the maximum (safe) amperage is to charge the cell.  I know (think) the optimal amperage to charge with would be 3.2A (1C), but is it safe to use 4A (1.25C) or even 5A (1.56C) without blowing anything up?

EDIT: I am using an Anker 3200mAh battery, but couldn't find a datasheet on their website (after a quick search). LINK

-Ben


texts: Purpose of bare copper perimiters on HF PCBs

texts:
I have seen many RF PCBs with a thick, rounded area of exposed copper going all around the PCB, like in this example:

My intuitive thought is that this is for some kind of grounding or shielding can, however I have seen this on PCBs that had none of that.

What is the design reason for this characteristic, rounded strip?


texts: Modifying memory of an integrated circuit

texts:
The integrated circuits of EMV-chips (normal credit cards) claim that their memory is physically protected, is it possible to make an integrated circuit in which the memory can only be modified and read through the microprocessor and not directly?

I'm asking as I'm thinking of writing my master thesis on the subject.


texts: What does \$x^*(t)=x(t)\$ mean in signals and systems?

texts: I am often seeing this notation \$x^*(t)=x(t)\$ or similar but I cannot remember when I saw it the first time and I cannot find anywhere that explains the meaning of that notation. What does it mean?


texts: Signal connected to multiple drivers error in Verilog

texts:
I have only assigned the values to RegMem once.
    module Registers(
    input [4:0] ReadRegNum1,
    input [4:0] ReadRegNum2,
    input [4:0] WriteRegNum,
    input [31:0] WriteData,
    output [31:0] ReadData1,
    output [31:0] ReadData2,
    input RegWrite,
    input Clk,
    input Reset
    );
reg [31:0] RegMem[31:0];

assign ReadData1=RegMem[ReadRegNum1];
assign ReadData2=RegMem[ReadRegNum2];

always@(Reset)
begin
if (Reset==0)
begin
$readmemh("MemReg.mem",RegMem);
end
end
always@(posedge Clk)
begin
    if(RegWrite==1)
    begin
    RegMem[3]=123;
    end
end
 endmodule


texts: Running COB LED without driver (undervolted)

texts:
!Hobby project!

I have a power supply form a printer (actually I have 3 :) ). The PSU is 24V, 1.25A.
I want to connect some COB LEDs to this PSU without additional electronics. The idea is that the LEDs requires no driver if they are under-volted (am I right?).

I have found some cheap 10W rated 32-34V. I use 3 of them in parallel.

Will they light up at 24V? (I know, it is more like a "guess" question but no other documentation is provided with the LED)
There are COB LEDs out there that are "natively" running at 26V or 32V is the minimum voltage for a high power LED?

If question 1 and 2 fails, how to drive the LEDs with minimal electronics (using the PSU I have)?


texts: Why is there no DC standard for household wiring

texts:
In the country where I live, Victoria, an oppresive dictator, named El Jeffo sold off the state owned power generation distribution and retailing companies to the private sector. We were promised our cake and that we could eat it too. But we all know this isn't possible. Now the situation has deteriorated to the extent that there are power generation companies, power distribution companies and retail companies that are essentially billing systems for the power distribution companies - and these billing companies spend vast amounts of money advertising huge double digit percentage discounts for overpriced electricity. Needless to say, with such huge advertising overheads

A coup took place, and El Jeffo was deposed, but given a role to play football manager. A new regime took over, and it decided that solar was good, and paid huge vast subsidies to people that would install solar systems. Things were good, so long as the sun was shining as you could sell AC power back to the network, not noticing the huge increases in prices that were taking place.

Now, the era of belt tightening has come upon us, and for this reason we are looking at improving efficiency. It is no longer profitable to send the power out via AC. Given that most solar is DC, batteries are DC and cell voltages are in the low single digit volts, and I2R losses would be short for short cable runs, and also that DC to DC converters are every efficient, no need for isolation etc would there be any benefit in efficiency in running TVs, LED lighting, most electronic appliances off some DC (everything apart from huge motors and resistive heatime appliances) and what would be good standard voltages for households for power that is generated and distruted only within the household?


texts: How is that "howling" sound produced in induction motors?

texts:
Note: No, there are no inverters involved in this question here.

I've perceived that most, if not all induction motors make a "howling" sound in their coils that is different from the constant 60 Hz tone they produce due to the working frequency.

This howl has pitch shifts depending on the rotor speed. In very low speeds it is low-pitched and blends with the 60 Hz hum, but as it speeds up the sound evolves into higher pitches. When accelerating I can hear it standing out when it gets around ~100 Hz and then it starts getting quieter after reaching ~400 Hz. When decelerating it does the opposite (I start hearing at ~400 Hz and then it goes down until it blends with the 60 Hz hum).

I have the impression that in motors with more poles this sound is much more audible, like my 16-pole ceiling fan motor. In it the howling is very audible when its spinning at low speeds, like 60 RPM.

And the more "effort" the motor is doing the louder the howl, reversing the fan during operation makes a much louder howl just before reversing (while it's at a low speed and decelerating, nearly stopping) than just after reversing.

I've also heard that howl in several other induction motors, most of them being 4-pole motors. The motors in vertical washing machines, for example, make a quite audible howl when accelerating (in the centrifugation step).

I know that this is probably the result of the interaction between the applied Electromotive Force and the Back Electromotive Force induced on the stator windings, as they're not in-phase and the speed of the rotor modulates the back-EMF on the stator windings.

The resultant between the EMF and the back-EMF (and the successive iterations of inductions between the stator and the rotor) might produce a higher frequency signal on the windings.

However, I can't figure out exactly how this happens.

Does anyone know how can I model the process making that sound?


texts: What motherboard components can I safely conformally coat and will this prevent condensation damage?

texts:
I plan on building and installing a small computer in my car for multimedia purposes. Since the only space I have for it is under the passenger seat and since the temperatures vary between -20 to 35+ over the year, I am worried about condensation and any damage it might cause.
My first thought was to use a sealed case but not only they're expensive, they're physically too large as well. Since I can't prevent condensation, my only option is to decrease the likelihood of it causing any damage. I noticed that other electrical components in the car (radio, amp, etc) are conformally coated and I thought I might do the same. Hence, my question.
I read that such a coating could change the impedance of the PCB tracks or that it would hurt heat dissipation. As such, I am interested in knowing what components on a motherboard are safe to coat and how bad can these effects actually be?
For reference, the board I will use is an ASRock Fatal1ty B450 Gaming-ITX/ac, which, as far as I can tell, uses heatsinks for the chipset and the VRM.


texts:
I am trying to filter a noisy 70kHz sinusoide that goes from -2V to +2V.

A factor 2 amplification should work.
Any suggestion on which circuit to use?

I tried to use an active bandpass filter using the Texas Instruments filter online tool  but it does not find any opamp suitable for the application.

Since the noise is in principle a high noise frequency maybe a low pass filter would work as well, but since I am only interested in the 70kHz frequency, I think a bandpass filter would be better.


texts: Automatic power switch between USB and LiPo battery

texts:
I was looking at the design of Adafruit M4 Feather board. The board can charge a battery via USB (and power the board). When USB is disconnected, the battery take over automatically. What I don't understand his how Q3, a P-Channel MOSFET, can be turned on when USB connector is disconnected.

My understanding is that Vgs must be negative to turn on a PMOS. Normally, in some other circuit, the source is connected to the power and the load to the drain, like the circuit below.

In the first circuit (Feather M4), when USB is disconnected, Vg = 0V, Vd = VBAT, Vs = ???
How does the whole thing work?


texts: Verilog Code for this (simple) Logic Gate?

texts:
Here's as far as I've gotten with this:

module Lab2pl(input x3, x2, x1, x0, output f, g, h);
  wire z3, z2, z1, z0, notx2, notx1;

  and
  a0(x0, x2, z0),
  a1(x1, x3, z1),
  a2(z2, z3, h, f);

  not
  n0(x2, notx2),
  n1(x1, notx1);

  or
  o0(z0, z1, g, f),
  o1(notx2, x0, z2),
  o2(notx1, x3, z3),
  o3(f);
Endmodule

It really doesn't make any sense to me how the wires going from o0/a2 into o3 aren't labeled. I can't find any helpful tutorials or resources and this is due tonight. Any help would be HUGELY appreciated.


texts: Control DC circuit with an AC lock switch

texts:
I am currently adding circuit with a horn and some lights powered by a motorcycle battery. The circuit should be using about 12v 18A. What I want to do is control the circuit with a lock switch. I've found this item on ebay, http://www.alibaba.com/product-gs/331822327/ignition_key_switch_lock.html and was wondering if I could use this to control my circuit.

The rating on the switch is really low, 250v 0.5A, and is rated for AC power, not DC.

Can I throw a relay on this switch to have to control my circuit?
I also would like to put a fuse on this, so what should I max my fuse at?
With such a low amp rating on my switch, will I even be able to trigger the relay?
Also, if I used this switch, what would be the worst case scenario? Could it case electric shock or an electrical fire? I don't really care if the switch gets fried, as long as nothing dangerous happens.

As a side note for relays, how much amps does it take to activate a relay? When I look at relays, I only see how much amps they are rated for.


texts: In a thin-film transistor (on insulating substrate) what is the difference between putting a load on the source or drain side of the transistor?

texts: My question was incorrectly posed, because I didn't include the capacitor connecting the gate to one of the terminal. So in fact this question is regarding common source vs common drain comparison...


texts: Phase Locked Loop Gain Design- FM Demodulation

texts:
Say I am trying to demodulate a message up to 25kHz in frequency, with a peak frequency deviation of 75kHz and a carrier of 1MHz, implying a 200kHz bandwidth using carsons rule.

Would I design the transfer function of the loop (Output/Input) so that there is a 20dB/decade slope up to 25kHz* where I would want it to level off? Should this "level" point be unity gain?

While trying to develop the loop transfer function, I find it possible to end the 20dB/decade slope at 25kHz* and level out, but I find that it is impossible  to design it so that the level out point is unity gain as well. In fact, I can never get unity gain anywhere near 25kHz*.

edit: This seems to be because I do not understand how to measure the Kvco constant. Is this constant controllable, or a natural element of the VCO? In derivations I find, it is treated as a separate entity than Av (the VCO carrier amplitude) and appears as a result of linearizing the PLL in most derivations.

If I can't control the value of this constant then it seems that I will never be able to achieve unity gain at the desired frequency as the rest of the constants (Ac,Av,Au,Kd) influence both the numerator and denominator of the transfer function, thus changing the frequency at which level gain occurs but not the magnitude of the gain itself.

edit2: Is the Kvco constant the frequency deviation in Hz/V? If this is the case, does it need to match the frequency deviation of the incoming FM modulated signal? I believe it would, in which case it becomes a fixed value. If it is a fixed value, does this not limit the design of the PLL? For example, in order to achieve unity gain at high frequencies, the numerator of the transfer function below seems to need to be 0.5 so that at very large values of s, the function essentially becomes 1. If this is the case, I can no longer change the bandwidth of the 20dB/decade region as it has become fixed if I want unity gain.

Here is my short Matlab simulation code for trying to design this transfer function:

%LOOP TF GAIN CALCULATION TESTING
%=================================
%PLL DESIGN INFORMATION:
%75kHz Peak Frequency Deviation
%1MHz carrier
%Baseband message bandwidth ~= 25kHz
%Phase Detector LPF cutoff: 500kHz, 4th order butterworth
%===========================================================
%Set Constants for loop calculation:
kvco = 1; %VCO constant
Au = 150000; %Amplifier Gain
kd = 1; %Phase detector LPF filter gain up to cutoff of ~500kHz
Ac = 1; %FM Modulator Carrier Amplitude
Av = 1; %VCO carrier Amplitude
%=================================================================

Loop_Num = [Au*kd*Ac*Av 0]; %Numerator of Transfer Function
Loop_Dem = [0.5 Au*kd*Ac*Av*kvco]; %Denominator of Transfer Function

Loop_Transfer = tf(Loop_Num, Loop_Dem); %Create Transfer Function

figure(1)
bode(Loop_Transfer) %Plot

And this transfer function has been derived using the following PLL Design:


texts: In-Circuit Crystal Frequency Measurement

texts:
I am designing a small testing unit to automate production testing for my company's main boards. One of the tests to be done is to verify that an 8MHz external crystal oscillator for a PIC MCU is running. Is there a recommended way to do this in a cheap and reliable way?
My thinking at the moment is to sample above 16 Msps (Nyquist frequency = 8MHz x 2 = 16MHz). This would give me enough information to reconstruct the wave and determine the frequency. The problems I see with this is the ADC I am currently using is only 500ksps. I would need to alot extra cost for a higher performance ADC as well as board space for an anti-aliasing filter to get rid of any higher harmonics that might be picked up. This solution feels bulky just for testing if a sine wave is present or not. Any suggestion appreciated.


texts:
Recently, I purchased two 48v 25A power supplies. I want to put them both in parallel. In reality, each PSU consists of 2 smaller individual units(see picture), so 4 units in total. Pin 8 of that ribbon wire connector is the pins you need to connect in order for the two smaller PSUs to output 48v at 25A.

So I know that linking both pin 8’s of the connectors in one power supply will make the 2 smaller units work together.

My question is, could I simply daisy chain the current share pins of all 4 sub-power supplies(what is done in picture) to make them all work together to output 48v at 50A? Reason asked is because these were very expensive and don’t want to cook anything.

Original: https://prnt.sc/q5aqyu

Edit: Datasheet for said PSUs


texts:
i would a help calculating the necessary air gap for a coil assuming an ideal magnetic material:
Cross sectional area of active material = 100 mm2
number of turns= 30
Inductance= 1mH
Thanks in advance


texts: Why is this MOSFET KVL to find VDS not right?

texts: There was an answer provided for this question I'm working on, but it seems that my answer was wrong. The sticky note has was the "correct answer" is supposed to be, but I don't understand why V-minus on the source is not included in that KVL equation.


texts:
I want to design op amp integrator circuit with variable time constant using a simple switch. What is the typical shunt capacitance of a switch? I assume Ron of switch to be less than 5 Ohms. I want switch to minimally effect overall feedback capacitance. I am not worried about transient response when capacitor are switched. Any suggestions on the design?

Thank you all for your suggestions.


texts: Total harmonic distortion (THD) of a circuit

texts:
Where \$V_{sin}\$ is sinusoidal with frequency \$f_{1} = 1 kHz\$.

The THD is defined as the sum of the power of all harmonics (except the fundamental) divided by the power of the fundamental harmonic.

I calculated \$V_{out}\$ wrt \$\omega\$ and the time-averaged power from there. Then I tried evaluating this power at frequencies \$f_{(n)} = n \cdot 1 kHz\$ and calculating the THD from this, but I can't make this sum.

This question was in a 3h exam, and it was worth 10%, so it should take around 18min to do. It can't be that complex numerically.

I'm most interested in the process of solving this over the actual answer. Thanks in advance.


texts: How does current flow through an ideal voltage source?

texts:
In class I had to analyze the following circuit:

When I solve the circuit, using superposition, I get there is a current flowing thorough the ideal voltage source in the right. What will the voltage source in the right actually do? Will it become like a resistor and cause to a voltage drop of 4v?


texts:
Trying to build arduino based boost converter,
The problem is, I have many coils but have no idea what their uh value is, some small ones have numbers on them,
If I use what appears to be a 100uh (by comparing it with 100uh coil images online) and it turns out to be a different value, what will be its impact on the performance or other factors, Can I go with the biggest one I have? Do I need to test their inductance(?) first?
fixed mh to uh


texts: What is the Umlaut Symbol in this relay?

texts:
I'm wondering if the reoccurring "Umlaut" (Ö) symbol in a manual for a process controller that I'm referencing is an actual electronic representation of something, if so what, or if this process control manual was translated from German and was meant as just an "O" symbol? The diagram shows a voltage dependent varisistor relay might the "Ö" represent N.O. terminal? Thanks for the Help.

simulate this circuit – Schematic created using CircuitLab


texts: Why a 20-bit shift register only output last 8 bits?

texts:
I need to use a VFD driver with 20-bit shift register but it only works for the last 8 bits:
void loop() {
    uint16_t buf = 0xFFFF;
    swrite(buf);
    delay(500);
  }
}

void swrite(uint16_t x) {
  for (uint16_t i = 0; i < nbit; i++) {
    digitalWrite(SDI, x & (1 << i));
    tCLK();
  }
  tLE();
}

void tLE() {
  digitalWrite(LE, HIGH);
  digitalWrite(LE, LOW);
}

void tCLK() {
  digitalWrite(CLK, HIGH);
  digitalWrite(CLK, LOW);
}

My SDI input:

The result of output of 0x00FF instead of 0xFFFF.
Functional table:

Thanks in advance !


texts:
If the rule is with parallel circuits that the voltage is the same across all nodes eg:

How does a zener diode regulate a voltage?

After the current passes the Rs resistor and we calculate that voltage (let's say it's 4.5 volts), won't the voltage be the same for both nodes? Even if the zener diode is dropping voltage both nodes should have the same starting voltage of 4.5 volts after the Rs resistor?

When I mean nodes I am referring to the node 1 and node 2 (both drawn in red)

How does a zener diode act to reduce voltage at nodes 1 and 2?

The tutorial I am following, https://www.electronics-tutorials.ws/diode/diode_7.html, is really poorly explained, with a  bunch of extraneous information.


texts:
GPS has three seperate frequency bands which are L1, L2 and L5 while Glonass has two seperate frequency  bands including L1 and L2. Also Galileo has three frequency bands named as E1, E6 and E5.
I want to select an antenna that can receive all the frequencies mentioned above to connect my HackRF One module to process these signals. So, first property of the antenna that I should be aware of would be its bandwidth.
HackRF One can easily acquire the signals if a suitable antenna is selected to its input port. Input port of the HackRF One is 50 ohm, so impedance of the antenna should be referenced to 50 ohm. Therefore, the second property of the antenna is its VSWR value.
Apart from two properties mentioned above, there is one thing that should be accounted which is antenna's gain. I am quite confused about this one. What should be suitable value of the antenna's gain to acquire GNSS signals?
I think one of the most suitable choice would be a telescopic antenna since the market offers lots of telescopic antennas.


texts: I have been told me that a shunt resistor can be made with a welding electrode, and you just have to calibrate it, any one have experience doing this or anything similar?


texts: Control power supply to MAX3232 IC using Arduino

texts: Need to control the supply to MAX3232 ( RS232_TO_TTL) IC using Arduino. The 3.3V supply is also tapped from the Arduino board. I have to keep the Vcc supply of MAX3232 around 3V. With the present circuit diagram, the voltage drop is around ( hence Vcc indented) is around 2.3V. Should I use a different Rc value or should I use driver level transistor like SL100 and avoid Rc altogether? Thanks.


texts: What's the practical difference of a wait process and a sense process?

texts:
All the VHDL-tutorials I've read mentions that one can use a sense process and a wait process, but I have been unable to grasp the difference.

That is:

Waitproc: process
    wait until clock ...
end process

Versus

Sense-proc: process (clock)
    if rising_edge(clock) then
    ...
end process

To me, these to seems do the same thing but obviously there must be a difference.

When should I use which one, and why?


texts: Noise/ Oscillation issue in an op amp circuit

texts:
simulate this circuit – Schematic created using CircuitLab

Currently facing some issues with noise/stability. When a multimeter is connected across Vout and Vref, there is a effectively no noise/oscillation i.e Multimeter reads 0.0012 mV r.m.s. However when an oscilloscope is connected to it (simultaneously with the Multimeter) the noise level rises to 1.8mV AC. I understand this is negligible however this is part of a current measurement circuitry with a T.F of 40mV/A hence its important to keep this reading as low as possible. The reference voltage is used to provide reference to the other subcircuits within the whole system.
This is what I have tried so far, a snubber ciruit; series RC from Node B to ground of 10nF and 100ohm resistor. ALso tried a snubber between nodes A and B. Tried playing about with the compensating resistor R1 but increasing this seemed to made it worse. L1 and L2 are Ferrites respectively. I have tried shorting these out and also playing about with the resistance still no help. Anyone have any other ideas.

UPDATE: I have just found that its in fact the ground connection of the scope is what's causing the issue. just attaching the ground clip on the vref point or Vout upsets it and raises noise to 1mV AC

Regards.


texts:
I have made a simlpe zero crossing circuit to control the speef of a single phase AC fan through conduction angle control with a Triac. The circuit looks like this with the use of 4n25, an optocoupler:

L and N represent live and neutral out of the mains supply.
So ideally i thought while the mains sine wave is above or below zero, you would get 0V beneath the 10k pullup resistor since there is condcution on the infrared diode and thus, conduction through the transistor. and when the sine wave passes through 0, it would make a pulse with 5V at its peak.
But when i put this to test, I see a sqaure wave of 50% duty cycle and 50Hz frequency, meaning the conduction through the transistor basically changes state when the mains sine wave goes from negative values to positive values. I am struggling to see the reason why and could really use some help.


texts: Help needed solve fire house problem 24v to 12v 100 milli amp

texts:
We are trying to make an antique bell work I'm told it needs 12v .1 /
amp or 100milli amp
Our current power system is 24 volt 20 amp can you please help us step this down . We were going to use a common 24 to 12 volt resistor to drop the voltage but unsure of how to drop the amps down to .1


texts: What are the ways to power 5V sensor using solar panels?

texts:
I have an outdoor sensor (which will have to work in the winter on Poland, however, we usually have temperature much over -10 Celsius degrees) which needs 5V.

The sensor operates 24 hours per day and consumes

about 300 mA when working, for about 10 seconds every 5 minutes and
less than 1 mA the rest of the time.

I want to power it using solar panels.

What solar panels should I use (what voltage)?

Do I need any DC-DC boost converters? step-down? step-up? Could you name some examples? How to look for them?

Are there any ICs for that purpose? For example, does BQ25504 would be helpful here?

What type of rechargeable batteries should I use? Are Ni-MH a good choice?


texts:
This is a problem that's always baffled me a bit. How does high frequency (more than 100MHz anyway) wireless communication actually work? I understand that it has an antennae and for receiving it amplifies it and checks for a logical 1 or 0 and reversed for transmitting.

What I do not understand is how an IC can communicate at such speeds? Take for example wifi, 2.4GHz. Is there a chip that is actually processing each bit 2.4 billion times per second? That seems impossible. Could someone explain how a transmitter and a receiver actually work electrically?


texts: I have a 3 phase to single phase ups 10kva. The Input voltage required is 332v to 444v/ 3 phase voltage with an output of 220-240v single phase. I have an external battery bank of 2v x 12 connected in series to make up 24v. My D.C. Voltage is still not enough to run the ups inverter when my 3 phase supply goes off. Can I be able to get a D.C. To D.C. Converter from 24v to 400v with a high amperage. Instead of adding more Battries.


texts: Can TEC1-12706 be damaged by running on low current?

texts: I'm using a HDD power supply of 12V 2A. The plate stopped heating or getting cold. I tested the power supply which is working fine. Tried changing the power supply by mobile charger with no effect. I do not have 12V 5A power supply available to know for sure.


texts:
I went through the data sheet of STM32F4 and found the pin configuration of GPIOs. I don't understand the difference between these configurations:

Input floating
Input pull-up
Input-pull-down
Analog
Output open-drain with pull-up or pull-down capability
Output push-pull with pull-up or pull-down capability

I have used some of these configurations by vaguely understanding it. Could you help me to understand how this works? What is the difference between these configurations?


texts:
I have some 12 volt cooling fans which interfere with a radio transmitter. I notice that if I either put a large capacitor in parallel, or a large inductor in series, I can eliminate the noise heard on the transmissions from the 400mhz RF transmitter.

I want to have a capacitor-inductor pair (or maybe π or T filter) right in the "sweet spot" optimizing for smallest physical size.

What factors and design considerations should take place when optimizing for the right pair of L and C.

There are three 5 watt fans I am powering from 12vDC.


texts: Proteus - Simulation of capacitor discharge

texts: Hello I am having difficulties using Proteus to make a simulation of a graph for demonstration on the graph or discharge of the capacitor. It shows the instant after unloading and there is no logarithm graphic of the unloading, I am then reproducing in the graph, precious guidance.


texts: Connect GND/signal-output-pins to differential-input-pins

texts:
I have a device outputting a signal (-10V...+10V) referring to GND. Now I want to feed this signal into another device, that only accepts differential inputs (-10V...+10V).

Is it possible to just connect GND to one of the diff. input-pins and signal to the other diff. input-pin? Is there something completly wrong with this attempt?

Edit: Both devices are connected to a common ground.


texts:
I have this circuit on a breadboard and it works exactly as I expect. If you put in -5V you get out +5V, if you put in 0V, you get out -5V, and if you put in +5V you get out 0V.

The problem I'm running into is that I initially built this and several other similar circuits with the first bunch of diodes I had to hand without particularly looking at them. It turns out I was using some germanium diodes from an old radio project. They are 1N276 and something in a glass case with a green stripe but no part number. I only had a few so I couldn't continue with this project until I got more diodes. I tried 1N4001 and 1N4003 because I had them on hand, but didn't expect them to work (they didn't). I then bought some 1N4148's which I did expect to work since they are "small signal switching diodes". Unfortunately, the resulting outputs just oscillate wildly.

I'm kind of baffled because the diodes I would expect to work perfectly for this application don't, and the diodes I would never have specified for this circuit work perfectly. Any ideas as to why this is the case and a proper replacement part that will work as expected?

Thanks much!


texts: Speaker Frequency Range and Frequency Response

texts:
What is the difference between frequency response and frequency range of a speaker?

How do we measure frequency range and frequency response?


texts:
So we're trying to store bytes (from an A/D converter) of data into a SanDisk 1Gb microSD card from a LPC1769 microcontroller board using the on-board SPI protocol. I know how all that stuff works, but I have no idea how to start working with the microSD card - I've seen various references to CMD0 and what not, but I don't know where to find this library or how to properly incorporate it into the C compiler for the board.

All I need is to figure out how to start the connection properly and then how to read and write data into the card at designated blocks.

void write(int data, int block)
int read(int block)

Is there a library to do that? If not, how can I implement this?


texts:
The following is an exam question I encountered.

In the above circuit the current across E is 180 mA. Since the current across 300 Ohm resistor is 13.33 mA, there will approximately be a current of 166 mA through the zener diode Z1.

Then the resulting power dissipated would exceed the power rating of the diode Z1.

My question is; what exactly happens in a situation like this? How will a circuit behave when the power rating of a diode is exceeded (both theoretically and practically)

Thank You


texts: Purpose of level-shifter with same in and out voltages

texts:
I am looking at a schematic for the Pixhawk 2 board (page 3).

The UART ports on the microcontroller are sent through a level-shifter chip (TXS0108) where the input voltage is the same as the output voltage. What benefit does this provide?


texts:
simulate this circuit – Schematic created using CircuitLab

I used OA1 as feedback for adjust pin and OA2 as a buffer, there's a 10 mA load at the output to meet the minimum load requirement of the LM317.

The output voltage of LM317 is now totally dependent on the load on the output. Why?
When there's no load output voltage is 9.5V and connecting the non-inverting input of OA2 to any voltage pulls the output of LM317 to 22V and stays there.

Now if I connect any load, voltage will drop depending on the amount of load and it doesn't matter to what voltage the non-inverting pin of OA2 is connected!

How can I control the output of LM317 digitally and have a constant voltage?


texts: How does Frequency Modulation work with radio frequencies?

texts:
Inspired by this question:

What is the basic difference between AM and FM radio?

I got to wondering: If I put my FM radio on some radio channel (Let's just say 100 MHz to pick some number), shouldn't it just pick up whatever is transmitted at 100 MHz? If you modulate the frequency you are transmitting with, why do I not only pick up, essentially, the equivalent of an AM signal at 100 MHz, instead of picking up on frequencies that are not 100 MHz (Since they've been Frequency Modulated, they're not 100 MHz, which is what my radio is on).

Now obviously FM radio WORKS, so I must be misunderstanding something - but what?

  Is this question "why does it pick up a band (100MHz to eg. 100MHz+20kHz) rather than a single point frequency?" – pjc50 5 mins ago

Yes, that is a fair rephrasing. In my head, an antenna is built + filtered for one frequency. If it's picking up stuff at other frequencies, that's unpredictable and definitely not a way to transfer a signal - yet clearly I'm wrong. How?


texts: SMPS control components and technologies

texts:
Preface: the switch-mode power supply is a flyback power-factor corrected AC-DC converter. I'm currently using a combination of AVR microcontroller (ATmega64A) with some analog (such as DACs) and digital (logic) external components. So control system used to switch main transistor, to control inductor discharge time, failures and so on (no special purpose PWM-controller implemented).

This approach has some certain limitations and drawbacks:

I can not precisely control several high-frequency processes and I limited regarding switch frequency to about 30-50 kHz
If I need to make any changes to hard logic - I need to use solder and a knife
I don't really like AVR documentation and periferal structure: many of software changes require a lot of reading and debugging, as peripheral (for example timers) has complicated control and modes

There are several alternatives I already considered as a next step:

ARM Cortex-M0(3) controllers (looks much faster than AVR, more peripheral, huge community),
Altera FPGAs (even faster, flexible programmable logic on a single chip, however there are no or rare any periphery such as ADCs, DACs, require for several unusual power supplies, no small packages available, quite different development chain and finally much more expensive).

So for me ARM looks as an obvious step forward but FPGAs looks very promising in some aspects.

Maybe I'm missing some alternatives?

For example I know that TI, ST and Microchip has several special purpose microcontrollers dedicated to SMPSs.

Maybe there are any controllers between FPGAs and GPMCs which can be good for my purposes?

Conclusion: I realize that I did not describe my needs in a degree that would be enough for expert answer, but I hope to have some directions to look forward and decide myself where to go in my closest future.


texts: Measuring the orientation sensitivity of a UHF RFID transponder, where do the deviations come from?

texts:
I measured the orientation sensitivity of a UHF RFID tag using a Voyantic Tagformance Lite RFID test device. I rotated the tag along the 3 axes using a stepper motor and a rotating table.

The device measures the path losses from the device to the tag location using a reference tag with known properties. I positioned the reference tag to the measurement location and started the calibration process. The device does a frequency sweep from 800-1000 MHz ands sends a read command at varying power levels until the tag responds. Once the tag responds, the path loss is calculated using the known properties of the reference tag.

Path loss = Transmitted power - Power on Tag

Power on tag is a known property of the reference tag
Transmitted power is the power level at which the tag responds

After the path loss has been measured for every frequency, the reference tag can be replaced with the tag under test. Using the same measurement as above, the device calculates the read range with following formula:

Where \$P_{tag}\$ = transmitted power (at which tag responds) - path loss (measured using the reference tag)

and \$P_{max,EIRP}\$ = 3.28 W

This is the first measurement orientation (I measured 4 copies of the same tag)

and here is the result as a polar diagram. Depicted is the read range as a function of orientation angle

Next rotation

and the result

Last measurement

Result

My questions:

The last measurement shows large deviations between the tags, what could be the reason for this? Could it be reflections from the rotating table? I could not properly reproduce the measurements, I always get more or less different results for this measurement.

Edit: What causes the fluctuations from angle 0 - angle 180? 180° - 270° is exactly what I expected. The material I put the tag on is styrodur, it is pretty much electromagnetically neutral.
Why is the overall shape of measurement 1 and measurement 2 different? I would have expected a very close result between those two measurements.

Overall, the results are more or less what I expected but there are some discrepancies that I can't explain. Can anyone shed some light on this? My guess would be that the rotating table is somehow interfering with the measurement in the last two experiments.


texts: What is the meaning of GY-X nomenclature in chips?

texts:
I have a pressure sensor that is using the chip MS5611.
But, the "board" say: "GY-63"

I understand that the MS5611 is the "internal" chip, where the magic comes, but, what is the meaning of "GY-63"?

If I have to call this "sensor/module/chip" with a name, which should be that name? GY-63? MS6511? Which name identify this "thing" as an unique identification (ID)?

Sorry for mix up a lot of concepts. I'm a web developer. I'm not familiarized with this naming conventions.

ADDED:
For example, I have a GY-68, GY-63, GY-GPS6MV1, and 4 or 5 more of them


texts: How to connect Ethernet Switch IC with ARM9 CPU

texts:
I'm planning to develop an ARM9 based Linux board as an Ethernet wired router device.

I selected EP9302 from Cirrus Logic as the ARM9 CPU and RTL8305 from RealTek as the Ethernet Switch/Hub IC.

But I have a serious problem on designing the router with those things. I need 1*WAN port for Internet and 4*LAN ports for switching on device. For that, RTL8305 should be connected with two MII interfaces. I mean EP9302 should provide two Ethernet Interface (such as eth0, eht1). But, unfortunately, EP9302 has only one Ethernet interface.

Are there any solution for this problem?

I heard I may control Ethernet Switch Chip with GPIO pins. But I don't know how to configure them and how to connect them.


texts: To use Reed switch to switch DC supply to a relay coil...what precautions to take?

texts:
I wish to use a reed switch the contacts of which will switch the coil of a relay with coil voltage of 12 volts ( Coil resistance 160 Ohms)  or 24 volts DC (Coil resistance 640 Ohms). I prefer  to use a 24 volt relay  being commonly available but my impression is that the contacts of the reed switches are rated at 20 Volts DC.

Any other precaution is needed to prevent damage to the reed switch ?
The load on the relay is a pump motor of say 1/2 to 1 HP.


texts: Question about the RMS value of the real input power

texts:
I've the following circuit:

simulate this circuit – Schematic created using CircuitLab

I know that the relation between the input voltage and the input current is given by:

$$\begin{cases}
\text{V}_{\space\text{in}}\left(t\right)=\text{I}_{\space\text{in}}\left(t\right)\cdot\text{R}_1+\text{I}_{\space\text{in}}'\left(t\right)\cdot\text{L}_1+\text{V}_{\space\text{R}_2\space||\space\text{L}_2}\left(t\right)\\
\\
\text{I}_{\space\text{in}}'\left(t\right)=\text{V}_{\space\text{R}_2\space||\space\text{L}_2}'\left(t\right)\cdot\frac{1}{\text{R}_2}+\text{V}_{\space\text{R}_2\space||\space\text{L}_2}\left(t\right)\cdot\frac{1}{\text{L}_2}
\end{cases}\tag1
$$

Now, when I measure the real input  power, I will get an the RMS value of the real input power, and my question is: can I state the following:

$$\text{P}_{\space\text{in RMS}}=\text{P}_{\space\text{R}_1\space\text{RMS}}+\text{P}_{\space\text{R}_2\space\text{RMS}}=\text{I}_{\space\text{in RMS}}^2\cdot\left(\text{R}_1+\text{R}_2\right)\tag2$$

Where:

$$\text{I}_{\space\text{in RMS}}^2=\lim_{\text{n}\to\infty}\sqrt{\frac{1}{\text{n}}\int_0^\text{n}\left(\text{I}_{\space\text{in}}^2\left(t\right)\right)^2\space\text{d}t}=\lim_{\text{n}\to\infty}\sqrt{\frac{1}{\text{n}}\int_0^\text{n}\text{I}_{\space\text{in}}^4\left(t\right)\space\text{d}t}\tag3$$


texts:
I'm trying to do some verilog code for my class and I came around BUFGP. After doing some research I only found that it is a buffer for driving clocks. Can anybody explain this to me.
For example I have the following line of code which I'm not sure of what it is supposed to do.

BUFGP BUFGP1 (board_clk, CLK);


texts: Tantalum capacitor selection in LT3652 Buck Converter

texts:
In this circuit, a buck solar single cell Li-Ion battery charger, I need to select C3 and C4 tantalum capacitors. \$V_{BAT(FLT)}\$ is going to be 4.2 V, hence I selected:

\$C3_{VMAX}=10\text{ V}\$
\$C4_{VMAX}=10\text{ V}\$

Datasheet suggests low ESR tantalum capacitors but the supplier has capacitors ranging from \$1\text{ }\Omega\text{ to }80\text{ }\text{m}\Omega\$.

Are the \$C3_{VMAX}\$ and \$C4_{VMAX}\$ values I picked, correct for this application?
What ESR values should I pick for the tantalum capacitors for this application, and why?


texts: 18650 cells - Unable to measure capacity

texts:
I got many 18650 batteries from notebook batteries and I want to test their capacity by my Turnigy Accucell 8.

My problem is, that when I start discharge program (0.5A what is from battery datasheet) it stops after 20mAh and battery have 2.75V. Battery recovers to 3.8V.

When I discharge slowly (0.1A) I get 1500-2000mAh what is right value.

Why this hapenning? How to discharge batteries faster? 0.1A is 10hours discharge time and I have 100 batteries to test...


texts: ARM assembly - Addition of specific bytes from word-size values

texts:
I'm trying to code a way to add specific halfwords from word-sized numbers in the ARM assembly language. For example, lets say I want to add the first 4 digits of r0=0x3B029BA1 and r1=0x0B54A361 or the middle 4 digits of r0=0x3B029BA1 and r1=0x0B54A361. I can't seem to make this work. This is a shortened example of what I have so far.

LDR r0, =0x3B029BA1;
LDR r1, =0x0B54A361;
LDRH r10, [r1];

I'm pretty sure there will need to be an offset for the address in the 3rd line of the code, but I haven't gotten past a halfword just getting into the register 10. Every time I run this code, the correct register values end up in r0 and r1, but nothing at all is appearing in r10. So before I do anything else, I just want to understand why this is happening.


texts: Figuring Out Pin-Header Size for Socket from Datasheet + Ordering Specific Pin-Header Size

texts:
I ordered a 24 pin component socket for an Arduino Pro Micro. The specific one can be found here:

https://www.mouser.com/ProductDetail/575-11044624?r=575-11044624

However, when I received my Arduino (https://www.amazon.com/gp/product/B01MTU9GOB/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1) the male pin headers that came with it were too big to fit the tiny holes in this socket. Unfortunately, I already soldered the socket into the mechanical keyboard I am building and therefore need to find pin headers that fit the holes of this socket. However, I'm confused at how to search for pin headers that fit the specification on the datasheet:

https://www.mouser.com/ds/2/273/090-259652.pdf
(Manufacturer Number: 110-44-624-41-001000)

The Sleeve (Pin): 200 µ” Sn --> Which I think is the size? But I'm not sure how to match that to a pin header size.

When I search on DigiKey for male pin headers, the only measurements that I'm seeing are: Pitch, Row Spacing, Contact Length, Overall Contact Length, and Insulation Height. None of these seem to be what I need to specify.

Any suggestions on:
(1) How to figure out the size of the pin-header I need? and
(2) How to purchase male pin-headers with a specific size?

Thanks,
~Z


texts: Does this exist: Insulating material to cover circuit

texts:
For example when you build a circuit you have the board and the components between them is air.

Is there a clay like material that will act like air does?

Application: you could bundle simple circuits into a ball, attach adhesive to the outside and throw them at things (LED throwie)


texts: TH3122 KBus transceiver seems blocking its own TX

texts:
I'm using an I/K-Bus transceiver IC from Melexis.

This is the one which has collision detection and other functions that makes it easy to send and receive data from the bus.

The I/K Bus is a common bus used in BMWs starting from the early 2000s to control windows, doors, and receive their status (and much more).

It has a pin name "SEN/STA" which is a bidirectional pin used to detect and control the bus state. When you read this pin, it shows logic 0 when the bus is free, and logic 1 when it is busy (thus you should not start sending your message). When you write to this pin, you can disable the "transmission path" (logic 1), or you can force it to be free (logic 0).

Although the chip has a lot of cool features I'm not able to use it to transmit any single message onto the bus.

My schematics is here (tried with the SEN/STA wire removed too):

Here is a scope image of the TX coming from the serial port (yellow), and the BUS line (purple). You can see that the IC tries to start the transmission on the BUS line, but immediately stops it.

Here is a scope image of the SEN/STA pin (yellow) and the BUS (purple):
You can see that the SEN/STA goes up during the requested transmission which is okay, but it should NOT stop the current transmission. It seems the IC thinks the BUS is busy and stops its transmission!

Here is a scope image of the SEN/STA pin (yellow) vs. serial TTL TX pin (purple):
You can see the SEN/STA is high during the transmission (a bit later the yellow line went down, similar to the picture above).

I'm using PuTTY to send data at 9600 baud, 8N1. This is the specification for the I/K Bus.

I think the bus logic of the TH3122 is fine, however it should not disable its own transmission.

UPDATE1

Now I tried to force the SEN/STA to logic 0 during the TX.
Here are my scope images for this:

BUS (yellow), TX (purple), you can see that transmission is disabled after each falling edge of the TX:

BUS (yellow), SENSTA (purple), you can see SENSTA is controlled to be logic 0 for the whole transmission operation as marked on Figure 3 in the datasheet:


texts: trigger alarm with relay from PC sound output

texts:
As a total beginner, I have a project of creating an alarm device for a sailing boat. The background is the following:

a Mac-mini collects, by means of different computer programs, alarms from different sources.
in order to make the sound signal loud enough, a simple possibility would be to plug a hifi-system on the sound output of the PC, and set the volume to its maximum. Of course, this solution is far too costly in energy (the boat has limited electrical power).
so I'm looking for a workaround. I thought that a static relay, connected to the audio output of the Mac-mini, could  activate an alarm such as this one.

There is my question: is it possible to trigger a relay directly from the Mac-mini audio output, or do I have to use a transistor? Some clues are given here but I'm not too sure how to conclude.

EDIT : I just measured the output voltage of an PC audio output (on a PC), and when the volume is at the maximum it reaches from -1V to +1V, with some peaks out of the [-1V,1V] range, if it helps.


texts:
I am designing a H-Bridge based DC-DC Converter that boosts 24V to 350V DC. I use a HF transformer at the output of the H-Bridge for the actual boost. The circuit works OK for a while and then the IC dies. I suspect this is because I have ringing present at the output of the H-Bridge. The first picture below shows the output without the transformer and the second one shows how the ringing increases with the transformer.

My layout currently is on a single layer board and I will move to a 2-layer board to minimize loop areas of signals that drive the gates of the MOSFETS - but wouldn't the inductance of the transformer always cause some ringing? If so, how can I be sure that it won't damage my chip? The half-bridge driver that I'm using is MAX15019 and it can tolerate -5V to 130V at the output pin so I'm mostly concerned about the negative transients.

The following schematic shows the circuit. The graphs are measured at nodes A and B with respect to GND (this is also where the transformer's primary is connected). Note that I have tried various values for the gate resistors and using a higher one usually just leads to more power loss in the transistors. As mentioned before, I am concerned with minimizing negative transients - particularly when the transformer is connected.


texts: How does a bad power factor affect batteries with inverters?

texts:
Let's say I'm using a 100% efficient battery (AC battery, so there's an inverter in front of it) to power a motor with a power factor of 0.5. Let's also assume the inverter cannot correct the power factor for some reason (normally they can, right?) and is 100% efficient. Let's also assume 0 resistance in the power lines.

If I hook up the battery to a 1 HP motor with 100% efficiency, will the battery start losing more than 1 HP? I would assume not since the inverter's job is just to convert power from one form (DC) to another (AC) and it doesn't take power to have current with 0 voltage, correct (this would happen every cycle because the voltage and current wave form are out of sync due to the bad power factor)?

The only concern I have is that batteries have a limited amount of current, so if current was always being extracted from the battery (even at 0 voltage due to a bad power factor), the battery would still be losing potential power.


texts:
I have an air soft gun battery that needs to be completely before charging it because the charger does not have overcharge protection. Basically I have to time charging it.

I would like to make a circuit that would completely drain the battery as much as possible without damaging it before I hook up the battery to the charger.

How would I go around making such a circuit (that would not harm the battery)?

Here is the individual Battery information:

Ni-MH, 2/3 A, 1100mAh, 1.2V, 7 Batteries in the pack. The batteries are lined up + to -

Thanks!


texts:
I'm pretty used to just blindly specifying high-Tg 170C or greater on my complex multi-layer boards.  I do understand what the rating means and have a general idea that higher Tg means they'll survive in the oven at higher temperatures (like for RoHS process).

Anyway I was quoting a tiny 1" x 0.5" 4 layer PCB and the cost difference between Tg 150 and Tg 170 was about 10x for my run.  So I'm inclined to go with Tg 150 :)  But I'm not sure of myself.

What should I watch out for here?  Or maybe better what questions should I be asking myself about my design to ensure I can pick 150Tg with confidence?  Max ambient is 55C and the board doesn't generate much heat, maybe an additional 10C rise. I don't have to use RoHS compliant process I just do because it's nicer to the environment.

I did do some reading and googling but didn't really find what I was looking for.


texts: How does buck converter increases current

texts:
I am confused regarding this, in buck converter Pin=Pout, so if I reduce voltage then current has to increase but my resister load is fixed at, say, 5 ohms - but resistors follows Ohm's law and according to that current should decrease if the voltage is reduced.

So if you could tell me where I am wrong.


texts:
I am using this class D amplifier SSM2356 in my design.

I am giving same input to the audio input left and right.
I play a audio and probe the supply, input audio and the audio output signal (both left and right) at the speaker. Here is the waveform:

Strangely the output is a PWM signal with some ringing, but I believe it should have been amplified replica of the input signal.

Please suggest if my methodology of the audio measurement is correct? I would also like to get suggestions on reducing the ripple on power supply.


texts: Is controlling a voltage regulator's EN/SHDN terminal directly by 3.3V microcontroller possible?

texts:
Let's take the LT1763. The datasheet says that "The SHDN pin can be driven either by 5V logic or open-collector logic with a pull-up resistor."
On the other hand the chart "SHDN Pin Threshold Off-to-On" says about 0.7V at 25*C temp suggesting 0.7V shall be enough to drive the SHDN pin high.

The question is whether 3.3V logic is enough to drive this line reliably? If not, which chart should I study?

I need the device to operate normally off and enable it from the microcontroller on demand. If the 3.3V cannot drive the SHDN pin correclty then I'll need to use an NPN and put the chip power supply between Vin and NPN's collector (for GND).


texts: In the construction of a full wave rectifier, why is there centre tapped secondary winding in the transformer? OR What's the role of centre-tapped transformer in a full wave rectifier?


texts: How do I charge a 2100v 0.95uF capacitor?

texts: I'm trying to make a rail gun, and I am using 4 microwave capacitors for the extra kick but I don't know how to charge them. I would like to know how charging capacitors works and what I'll need to get to charge them.


texts: PSEN Pin when interfacing external memory in Harvard Architecture 8051

texts:
I am a computer engineering student, we have exam soon and I am completely new to this stuff . I have thoroughly searched the Internet but couldn't find any document on how to interface external memory in Harvard Architecture in 8051 microprocessor.

I know that in Harvard Architecture, program code and other data separated by two memories. Can anyone show me that how do I interface a 2732 (4Kx8 EPROM) and 4Kx8 RAM (6116) external memory in Harvard Memory in 8051 or lead me any useful document?

At least, I need to know how PSEN pin is used when interfacing external memory in Harvard Architecture. Thanks.


texts: When the NMOS is connected to VDD and turned off, why does it not block the current completely?

texts:
Here is a link to a Falstad simulation:
Link to simulation 1

The NMOS is connected to the VDD, but when it is turned off we have VSD=0,435 V. Why is the drop not 1,2 V?
The reason I don't understand this is that when the NMOS is off, we are not able to attract any electrons from the p-substrate in the NMOS, so how does it not completely shut the current off and we have a voltage drop of 1,2 V, instead of 0,435 V?
When we swap the drain and source in the NMOS the drop will be 1,2 V, why does it then work?
Here's another simulation:
Link to simulation 2

Look at the left case. Here when the two NMOS on top are turned off, they have an intermediate voltage drop, but here it doesn't matter where the drain and source are?


texts: In order to program a target MCU with STLink you need to connect 4 wires - SWCLK, SWDIO, GND and VCC (3.3V). STLink v2 programmer has 3.3V pin already present and ready to use. But let's say I would like to use my STM32F401 Nucleo-64 development board as a programmer. In this case, I need to remove CN2 jumpers and use SWD connector. The problem is, SWD connector does not have target power (3.3V) pin. Where do I get 3.3V? Can I just take it from nucleo board?


texts: How can I detect which DC power source to send to an underwater camera housing?

texts:
I have a small problem and hoping someone can help:

I am trying to design and build a reasonably universal underwater housing for some different cameras. there is a breakout box on the surface and the housing is cabled to this box for things like a video feed, ethernet control of the camera etc.

My current problem is power. As well as onboard batteries, I also want to feed power to the camera from larger DC block batteries located on the surface. There are two inputs on the breakout box, one accepts 12v DC power + and - from a block battery and one accepts 24v DC power + and - from different type of block battery. Inside the camera housing underwater, there are two power connectors (one 12v with + and - terminals and one 24v with + and - terminals) as I would like to support the use of both 12v and a 24v camera. These power connectors are different styles to avoid connecting a 12v camera to a 24v supply!

I only have three wires left on my underwater cable to carry power so can't just hard wire the 12v input to the 12v output and the same with the 24v input/outputs as this would require four cables (this is an assumption on my part: You can't have 24v positive going down cable 1 with 12v positive down cable 2 and have them share the same negative cable 3. Please correct me if I'm wrong!).

I will only need one of these sources depending on whether a 12v or 24v camera is being used.

To solve this problem and make it the least amount of work for the user possible, I have the following solution:

inside the surface breakout box have a circuit that detects which power input has a battery plugged into it. If it's the 12v battery, use cable 1 to the housing as positive and cable 3 as negative. If it's the 24v volt battery, use cable 2 as positive and cable 3 as negative. If the user has plugged both a 24v and 12v battery, it should favour the 24v and use the logic above but isolate the 12v battery to prevent it overloading.

Down at the housing end, another circuit can detect whether positive current is coming down cable 1 (this would be the 12v battery according to the logic above) or cable 2 (the 24v). Based on this detection, it would the connect the power to either the 24v or the 12v outputs to power the camera.

I don't want to get into voltage measurement as 24v and 12v are expressed as simplifications. Actual voltages could vary (but would remain within camera tolerances). Also I wouldn't want to smooth voltage to a consistent level as the video feed from the camera includes an overlay that expresses voltage of the input power source that people use as a gauge of when to change the battery.

My questions are:

a) is this possible?

b) is there a better solution to my problem?

c) is it possible to just have voltage convertors at the camera housing end? (eg one that would take 10-30v and convert to 12v and one that would take 10-30v and convert to 24v). Overheating is a consideration for a camera in an enclosed environment but if this were a potential solution, I would accept voltage smoothing, contrary to what I mentioned above.

Thanks!

Sam


texts: How can I use the component CD4538 or a 555 timer on Multisim?

texts: How can I use the component CD4538 or a 555 timer on Multisim for a delay of 1 second ? I want both of the nor gates to be 1  for roughly  1 second when the output of the op-amps is  either 01 or 10.


texts: Noise spike on microphone amplification circuit

texts:
I'm trying to build an electret mic amplification circuit. I see some weird spikes by just connecting the microphone like so:

5v ---^^^---------
     10kΩ)       |
                 |
                 |
          MIC+------------probe signal

          MIC-
             |
-GND---------------------------probe gnd

(^^^ = resistor)

The problem is that I'm getting some big spikes that I can't explain. The battery is 4xAA at around 5v, microphone is (this), probe attenuation x10, 1mV/div, 5uSec/div. Any ideas what these spikes might be? The specs of the mic say normal voltage 2V and I'm giving it 5V, could the mic be fried? Does seem to work when I speak, just there is hum when I amplify.

UPDATE
I changed the 4xAA battery supply to a 3.3V linear regulator (UA78M33CKCS) and replaced the 10kΩ resistor with a 2.2k one. I now have around 0.3mA going to the microphone (0.5mA is the max). The spikes are much smaller but still big compared to the signal I get when I speak. The time div in this picture is 20μS/div.


texts: Where to connect shield and ferrites in PCB with isolated planes

texts:
I have a device which has two sections of the PCB completely isolated form each other, but connected by an isolator IC (PN: ????).

I think I need to shield the whole device for reducing EMI because I am having a lot of EMI from the device.

The isolator IC transfers data and clock between the two isolated sections of the board.

One section connects to USB and is powered by the USB host.

The other section is powered by an external power supply and also has connectors for some external input signals that are processed by an FPGA.

What should I do to reduce EMI?

If I use ferrite beads, where should I add the ferrite beads? At the isolators? On pins transferring clock signal, data signal or both? Or on Vcc?


texts: Is there a device that can push down on a button with a wireless remote control?

texts:
I'm looking for a device, perhaps one that releases a small piston, tiny object, or block, that can press down on a button via wireless remote control. The button is about the size of a dime, and is sensitive enough it requires minimal effort to push.

The button is facing up, so I might not even have to mount the device on anything. Worse case scenario I'm hoping to duct tape the device over the button.

An alternative over a push-button could be a timed button. A device that can press down on the button every ~5 minutes.

Is there anything that's close to anything like this? I was hoping to find something from a marketplace website, but I've had no luck.


texts: Would this circuit work like an SR latch? Why is it better to use two NOR gates?

texts: I am very new to digital logic, and have just started to learn about feedback in circuits. The basic example of an OR gate with its output connected to one of its inputs creates a circuit that seems to behave like an SR latch without a reset function (i.e. once it receives an input it will output high indefinitely) so I am wondering if the following modification to this circuit would allow it to function as a latch, and why the standard topology using two NOR gates is preferred.


texts: How to passively shift logic levels to drive LEDs

texts: I have an input signal that is either 2.7V (low) or 9.9V (high). Is there any way to use passive components (excluding op-amps) to turn an LED off when the signal is low and on when the signal is high? This seems straightforward, but nothing is coming to mind.


texts: Why can't I change the speed of an ininduction motor by changing the voltage?

texts:
Given a three-phase asynchronous AC motor ("induction motor"), I tried figuring out whether lowering speed / torque by lowering the supply voltage should work, similarly to how it works with DC motors. From all that I could learn from Wikipedia, voltage-control is not possible, but one has to control the supply frequency to control the speed.
Here's my understanding of a asynchronous AC motor: the three-phase supply current induces a rotating magnetic field in the stator, the stator's field. The rotor rotates slower than the stator's field (the speed difference being the "slip"). This means that the stator's field moves relative to the rotor, which induces a current in the conductive rotor. This current in the rotor creates a magnetic field (the rotor's field). The rotor's field rotates with the same speed as the stator's field, but phase-shifted. The two phase-shifted fields push away from each other, which creates torque, driving the rotor.
Now, if I lowered the voltage across the stator's coils, nothing should change but the strength of the magnetic fields - right? And that should lower the torque. It would probably also lower the slip (given a fixed torque), but would that be a problem?
A slight hint that such a speed control should be possible is that (according to Wikipedia), larger asynchronous AC motors are started using a "YΔ-Connection" (translated from German, could not find that in English), where the motor is run in a star connection at start, putting 230V (in the European system) across each of the stator coils, and switched to a delta connection afterwards, putting 400V across the coils. Thus, a lower voltage seems to be possible…


texts: Can somebody tell me how can the data be read before the address is even loaded. In the image, the data is read before the address was completely loaded.


texts: What's this component and how could these screws affect it?

texts:
Today, I was seeing the circuit of an LNB deeply and a part of it catched my attention. Here is an image of the circuit:

And here is two images of the bottom and the two components that catched my attention(red circles):

There is two screws(Machine screw?)(green circles) that you can screw them up/down and this causes to get them close/far to the components.

Questions:

1- What are these two components?

2- How do they work? and what do they do in this circuit?

Added:

Two other images:

Also I have a demounted one that took from another LNB. Here is several image:

Please note that this component is not soldered on the PCB, it looks it is glued to the PCB using a red glue as you can see in the images.


texts:
I'm building a solid state tesla coil, which requires me to switch very high voltages at high speed to achieve resonance. The problem: I can't find any IGBTs that can switch the voltage I need.

In theory, I will have four IGBTs in a full-bridge driver configuration. I plan on using the IRG7PK35UD1PbF (datasheet), which has a max voltage of 1400 volts. However, I need to drive the primary coil at 6500 volts.

How can switch a load this large without getting obscenely expensive IGBTs? Would it be possible to put them in series/parallel to do this?


texts:
I have a project for a small remote control in which I'll use a magnet instead of screws/etc. to close the case.

Basically it is a two-piece plastic case in which one of the pieces has a magnet glued to it, and the other has a matching metal band at the corresponding spot. When the two are put together, the magnet holds them closed.

I was thinking if I could also use that same metal band as the antenna for the remote. I'd connect the magnet to the circuit, and since when the case is closed the band is tightly attached to the magnet, it'd be electrically connected to the circuit.

Would the magnetic field in the magnet prevent this from working? If yes, is there a workaround?


texts: Boolean Algebra: How do I implenent a 4 bit signed comparator

texts:
I'm studying for my digital electronics exam and I'm a bit lost here.
The goal of the exercise was to build 2 4bit comparators out of single bit comparators, one using unsigned bits and the other with signed bits.
This is the equation for the unsigned circuit:
A>B, Xout: (a xor b)'Yin
A=B, Yin: ab' + Xin
A<B, Zout: a'b + Zin
I was able to draw the unsigned circuit, but I'm struggling to understand how to obtain the boolean equations for the signed version.
I searched everywhere and I only found the unsigned implementation.
This is how I draw the 1bit block of the unsigned version:


texts: How to read values from a NO2 sensor from an Arduino?

texts:
Alphasense sells this NO2 sensor:

http://www.alphasense.com/environmental-sensors/alphasense_downloads.html

http://www.alphasense.com/environmental-sensors/pdf/NO2B4.pdf

How can I read the values from an Arduino ? Do I need something between the Arduino and the sensor ?

I have used a few basic sensors before, but I'm confused with this gas sensor: why  does the response curve seem to loop ? I naively expected a constant tension for a given concentration, but it looks like it is more complicated with chemical sensors.


texts: How to change size of several selected tracks in Altium Designer

texts:
Just that. I know how to change ALL tracks to the same size, but cannot find a way to select several ones and change the size of them.

thanks!


texts: A two-pole system can never be unstable?

texts:
I was reading in some textbooks and places online that a single pole introduces a -90 degree phase shift and that in the phase plot, it never actually reaches -90, it goes asymtotic to it.

Similarly, for a two-pole system, it never reaches -180 degrees, just reaches very close to it.

Does that mean that single-pole and two-pole systems can never be unstable since there is no phase crossover frequency?


texts: Arduino clock speed prescalers at start without fuses

texts: I know it's possible to change the clock prescaler at runtime. But is there a way to set the prescaler that is used at boot on an ATMega328? I'm aware of the fuses, but those are pretty permanent. I want it to start up at 8MHz and see if it's running on a lower voltage backup battery first. And if not, then switch to 16MHz. I've tried doing it as the first thing in setup() but it doesn't seem fast enough.


texts:
I am completely new to this stack exchange and to electronics and general so please keep that in mind if my question is not up to par for this site.

I've attempted to make a night light using a breadboard, 3V battery (Two 1.5 double AA), LED, photoresistor, 2N2222 transistor (not sure which side is emitter or collector), 220 ohm resistor and some wires. The led turns on. The problem is it's not functioning like a night light but rather just like a regular LED connected directly to a battery. I couldn't figure out how to change the values in the schematic, so they're slightly different than the ones I've provided.

simulate this circuit – Schematic created using CircuitLab

So what I was expecting to happen was that when there was light near the photoresistor, it would give less resistance and thus the current would choose that path instead of going through the transistor. Then the Led would stay off. Then when there is more light near the photoresistor, the resistance would increase, and the current would go through the transistor and turn on the Led. Clearly this did not happen. Any help is greatly appreciated.


texts:
I have this AC circuit:

simulate this circuit – Schematic created using CircuitLab
I have found VA which is \$222 \angle-119 mV\$.
The current flowing through the inductor \$IL = 2.6 \angle-89 mA\$
When I use Ohm's law to find current IR1 and IC2 they give me \$IR1=VA/R1 = 2.2 \angle-129 mA\$ and \$IC2=VA/XC2 = 1.3 \angle-39 mA\$  but when I add them (by converting them to rectangular form) they don't give me IL and I am confused why this is happening.


texts: Can I use multiple RF433 modules at the same time?

texts:
I'm talking about these guys:

Will having multiple RF433 transmitters and receivers active synchronously cause any communication problems?

Could I tweak something(be it software or hardware) to make it so that handshaking is available?


texts: What are the advantages of using FPGAs over TTL in intro computer architecture?

texts:
I teach the one and only computer architecture course at a liberal arts college.  The course is required for the computer science major and minor.  We do not have computer engineering, electrical engineering, other hardware courses, etc.  My primary goal in the course is for students to understand all the way down to the gate level how computers work, which I believe they learn best through a hardware lab and not just through a textbook (Computer Organization and Design by Hennessy and Patterson).  My secondary goal is to excite them about computer architecture and increase their excitement about computer science.  Preparing them directly for industry is not a goal, although motivating them to study more computer architecture is.  The students have generally not had any experience building anything or taking a college-level lab course.  Typically, 10-15 students take the course per semester.

I have been teaching the course since 1998 in a manner similar to how I was taught computer architecture and digital electronics back in the late 1980s at MIT: using DIP TTL chips on powered breadboards.  On the first hardware lab assignment, students build a full adder.  About halfway through the semester, they start building a simple computer with an 8-bit instruction set.  To reduce wiring, I provide them with a PCB with some of the electronics (two D flip-flops, two 4-bit LS 181 ALUs wired together to act as an 8-bit ALU, and a tri-state buffer). On the first of these labs, they derive the (very simple) control signals for the two instruction formats and build the circuit, entering instructions on switches and reading results from lights.  On the second of the labs, they add a program counter (2 LS163s) and an EPROM (which my original question was about, before it switched to how I should teach intro architecture).  On the final lab, they add a conditional branch instruction.  While the students spend a fair amount of time wiring and debugging, I feel that's where much of the learning takes place, and students leave with a real sense of accomplishment.

People on this forum have been telling me, though, that I should switch to FPGAs, which I haven't worked with before.  I'm a software engineer, not a computer engineer, and have now been out of school for a while, but I am capable of learning.  I wouldn't be able to get much money (maybe a few thousand dollars) for replacing our existing digital trainers.  We do have a single logic analyzer.

Given my goals and constraints, would you EEs recommend that I stick to my current approach of switch to one based on FPGAs?  If the latter, can you give me any pointers to materials with which to educate myself?

As requested, here is a link to the syllabus and lab assignments.

Addition: Yes, it  is a digital logic course too.  When I got to my college, students were required to take one semester of each of computer architecture and digital logic, and I combined them into a single semester.  Of course, that's a statement about the past, not the future.


texts: VHDL: What will happen in case of "U" or "X" or "Z" signal?

texts:
I am trying to design a generic decoder with an input of N-bits:

library ieee;
use ieee.std_logic_1164.all;    -- standard unresolved logic UX01ZWLH-
use ieee.numeric_std.all;       -- for the signed, unsigned types and arithmetic operations

entity decoder is

    generic (
        input_width : positive := 2
    );

    port (
        input : in std_logic_vector(input_width - 1 downto 0);
        output : out std_logic_vector(2**input_width - 1 downto 0)
    );

end entity decoder;

architecture behavioral of decoder is
begin

    output <= (to_integer(unsigned(input)) => '1', others => '0');

end architecture behavioral;

I am wondering what will happen if some bits in the input are "U" or "X" or "Z" for example: what will unsigned(input) return?

Is it possible to set my output to 0 when this case occurs?

More importantly, how are "U", "X", "Z", etc handled in synthesis?
What will happen if we synthetize this decoder and supply him for example with a "Z" input (leaving the input in open circuit)?

Thank you.


texts: Am I safe working with a power supplier of 12 DC connected to the AC wall socket main line?

texts:
I'm working on an electronic home experimental project. But
I have always been afraid of the issue of electricity since it can electrocute.

My question is..  Am I safe working with a power supplier of 12 DC connected to the AC wall socket?

Taking into consideration that the wires of the DC supplier will be exposed to feed my circuit. I have worked previously in this way with 5 volt power suppliers to feed digital circuits.

But still my uncertainty remains, for example if the transformer AC to DC(power supplier) does not work then AC could be dangerous if I touch the exposed wires of the DC supplier?

The power supplier that I want to use is 12 VDC with 10A of capacity.

Thanks a lot for your answers,

Greetings


texts: Wondering if my protective diode is sufficent

texts:
First off, since this is my first post (I am a long time answer seeker), I would like to thank the SE EE community for all the answers I got here over the years! Thanks!

Being self-taught, I've always gotten by on research and reading but this time I am stalled.

I want to build a DC-DC step-down powering a light sensing op-amp Schmitt trigger turning on a linear LDO reg for a fan (powered by the step-down). There is also another LDO powered by the step-down for some LEDs.

I drew up my schematics, put a protective diode across the fan reg, out of habit but now I am wondering if this is enough. This is the first time I am building something with electronics before the volt regs.

Anyway here are my schematics as they stand right now (they are not fully completed yet but you should get the jist of it) :

As you can see, I put a 1n4001 across the fan volt reg. Now, do I need to do something to protect the LM741 and/or the LM2575? The LED volt reg shouldn't need anything, by my understanding.

The only thing my research has given me is "you might not need a protective diode with a PC fan" which for me translates to - Yes you need one. Couldn't find anything that I can port over to my needs or to clarify my thoughts.

Also, if you spot something wrong with my schematics, please do tell. There is the enable pin/transistor setup on the fan volt reg I am uncertain about, my understanding says it should work as expected (have yet to find a confirmation). The 2941 needs 2v to turn off and less than 0.8 to turn on. There is the 1.5k resistor that might be the wrong value but I should be able to figure that out during the breadboard stage, so no biggy there.

Hope I was clear enough on everything, thanks for taking the time.
Any thoughts will be appreciated.

edit:

The whole circuit is for my aquarium light pendant. I am upgrading from CFLs to high wattage LEDs. Just to clarify, the LEDs in the circuit are not the main LEDs, they are gonna be my moonlights. I want to limit the number of wires I need to send up to the pendant, thus the light sensing fan. With this setup 2 wires takes care of the moonlights, the main LED cooling and grounding the aluminum pendant. Fan will activate when the main (dimmer capable) LEDs turn on past a certain intensity (above the moonlight intensity). Also, I am adding more than just 3 moonlight LEDS. That part of the circuit is unfinished. I am toying with the idea of having different intensity zones in the tank.

For the pots, I have this love of configurablity. The 100k pots with the LM741 are for the triggering intensity and hysteresis. The fan reg 10k and 2k are to dial in the minimum voltage that starts the fan and the maximum voltage at the end of the 5k pot, I do not want to add a kick start section to the circuit (cheaper, not going flEaBAY on this project). The 5k will be off board to control the fan speed. For the LED reg, yes I want to use it as a dimmer. It is easier to dim the LEDs than to tinker on the amount of LEDs to find the sweet spot of illumination for the moonlights (I know, I tried). The 10k pot is the standard R2 for the reg and the 1K is to have increased resolution at higher voltages. I might not need it but I would rather include it now than regret it later. Based on my previous moonlight systems I built, the relationship between light intensity and voltage isn't linear. The LED reg 2k pot will be a 1k R. That was an omission on my part.

I had looked into CC and PWM, there was just too much I was uncertain about. I decided to stick with what I knew. I did put those on my list of things to read up on. Would be really good additions to my bag of tricks.


texts: Can high power USB destroy older devices?

texts: My brand new pair of bluetooth headphones stopped working after charging them with a 2.1 Amps USB outlet. I can't turn it ON anymore. I do see the LED battery Green then I charge it though. I noticed on the datasheet that the Amps for the headphones are 500mA and I've been charging them with my 2.1A usb plug. Could that have friend the circuitry? I'm not sure how battery works, for from Ohms law, IR=V if V is constant 5V, and R I'm guessing is too, then A could not vary.


texts: Negative reflection coefficient question

texts:
If I have a transmission line with a reflection coefficient of -0.3, and I feed it an input voltage of 5V, will my net voltage at the reflection point be

(1 - 0.3)*5 = 3.5V

or

(1 + 0.3)*5 = 6.5V

Came across this problem a couple of days ago and I'm still not quite sure whether or not the reflection coefficient being negative makes a difference to the outcome.

Thanks for all the help!


texts: How to obtain the widest pulse on an oscilloscope?

texts:
I need to get the widest pulse from a train of pulses.
In some tester you have the option to show only the highest measure, There's a way to do that with the pulse measure in a DSO?

The DSO is an Atten ADS1022C, the pulse train is normally around 112 kHz, and I need to know if those pulse ever last more than 1 ms, no matter if stay high or low.


texts: Over voltage and reverse voltage protection of multiplexed ADC with voltage follower

texts:
I am designing a protection circuit for the ADC section of a design I am working on.

There will be 8 analog signals being read by a single pin of the MCU via an 8 channel multiplexer.  The analog signals each go through a voltage divider such that the current to ground is about 1 mA before getting fed into the multiplexer.  The multiplexer output feeds into an op amp configured as a voltage follower (buffer with gain 1) so that the leakage current on the ADC input clamping diodes doesn't affect the ADC reading.

The ADC is on-board my ARM MCU, which can tolerate voltages of -0.3 to 3.3 V.

I would like to add some sort of negative voltage and over voltage protection circuit before the multiplexer to protect both it and the op amp.  I think the best candidate would be to use a set of clamping diodes on each signal going into the multiplexer.  This would entail 16 individual diodes in total (2 for each ADC channel).  Then each analog signal path would look like this:

simulate this circuit – Schematic created using CircuitLab

Ideally, this would allow for a wide range of AC or DC analog signal to be fed into the voltage divider (at left).  My design spec would be for it to tolerate -230 to 600 V AC or DC analog signal.

Instead of soldering 16 discrete Schottky diodes onto my PCB, I was hoping to simply use a TVS diode array to do the job.  I was thinking of using the PUSB2X4Y in this application.  Since it has 4 clamping channels, I could simply use two of these to clamp the voltages on each of the 8 total analog channels in question.

The data sheet doesn't specify how much continuous current each diode can withstand, so I'm not sure if the part will work or not.  Every TVS diode array that I have looked at on Digikey only lists the pulse current that each diode can withstand... not constant.  Anyone know what ballpark figure to plan for on the constant current front?  Is the common practice to not use TVS diode arrays and opt for a multitude of discrete Schottkys to get the job done?

The other thing that I'm not sure about is how to account for leakage current.  Will the leakage current through D1 "cancel out" the leakage current through D2 in normal operation or will it end up affecting the voltage being fed into the multiplexer?  Same question with D4 and D5, though I'm not worried about those leakage currents since I have the op-amp buffering that input.


texts: Component usage in this constant-current source circuit

texts:
In the April 2014 edition of Elektor magazine, they present a circuit for a high-precision current source device (page 42). It allows the user to select a constant-current between 10nA and 20mA. They do a decent job of academically explaining the core of the current source itself, even providing an idealized version of it:

They then show how they implemented this current source in the actual device. They made Rs selectable for the different currents and added components for real-life considerations like surge protection and such. I got a little lost with their usage of a few components though that I'd like some help understanding.

Here's the relevant part of the full circuit. To keep the image size manageable, I'm cutting out the top half of the circuit, which is mostly the interface circuitry for the LCD screen and the DC-DC voltage converters.

Here, IC6 and IC8 play the parts of U1 and U2 from the idealized circuit. And D4 (along with R56, P3, and R60) plays the part of D1 to form a 1V Vref. So the voltage across pin 6 of IC6 and pin 3 of IC8 is 1V. Similar to a multimeter, the user would hook up the load across K2 and K3 using probes.

The components that are confusing me are T5, T6, and R59. I'll go through them separately:

The article says T5 serves as a surge protector. But if the gate is connected to the bottom of RS (RS-SEL in this schematic), wouldn't the Vgs of the JFET be 1V? Therefore, the FET would never turn on under normal conditions, which kind of defeats the current source? I'm obviously missing something.
According to the article, all of the source current from IC6 travels through R59 as long as the user-selected current is 100uA or less. I believe I understand that because at 100uA, Vbe of T6 would be 360mV, which is less than Vbe(on) for T6, so T6 would be off. But wouldn't R59 contribute a very large error in series with R28? The combined resistance of R59 and R28 is 13.6k, which would result in a current of 1V/(10k+3.6k) = 73.5uA. That's pretty far from 100uA.
For user-selected currents above 100uA, how does R59 and T6 affect the voltage going into the resistors downstream? Wouldn't they contribute significant voltage drops that mess up the 1V reference calculations? I can't figure out an intuitive feeling for how the resistor and transistor work together here.


texts:
The PCB manufacturing house that I use says the board thickness between 0.4mm and 1.6mm are the same cost (I have 2 layer design). What is the benefit of having thinner or thicker board thickness for FR-4? What I guess is that thinner is lighter, but may be problematic on pick & place machine (bending), thicker may be good for separating the signals away.

Could someone who is experienced in PCB design/fabrication explain how to select the thickness of the board (e.g, why do you select 1mm, or .8mm or 1.2mm, etc.)?


texts: Compiling a project without .uvprojx in KEIL

texts:
I am learning keil. And I want to compile a project that I found in GITHUB link here. But some of them doesn't include .uvprojx file. So I decided to create an empty uvision project and coppied all files on GITHUB to my new uvision project. But whenever I try to do this, it causes errors like

Error: L6218E: Undefined symbol asd_asd (referred from main.o). So my questions are;

How can I fix this error?
Is there another way to do this than 'coppy and paste'?

Or is KEIL wrong software to do this?


texts: Why wouldn't the diode in this transistor scheme turn on?

texts: In the schematic above, the diode should not light, but why? (Ignore the pencil drawings on the schematic).