texts: 74HC14 for debouncing: output is too low with Vcc=3.3V

texts:
I'm trying to make a keypad for STM32 MCU using a 74HC14D.653 for debouncing. Datasheet says that it can be fed with 3.3V Vcc so I will not have to make level-shifting between it and MCU.

The circuit (in theory) outputs logic LOW when buttons are released and logic HIGH when they're pressed.

When I already ordered the PCB and assembled it (I know it's (a bit) stupid not to test this particular circuit before putting it all together...) I found out a pretty unpleasant thing: when for example SW3 is pressed the output on pin 2 is not 3.3V at all. It's only 0.90V!

At the same time the rotary encoder connected to another 74HC14 in the same way works somehow but the built-in switch also does not work (my guess it's just a capacitor discharge when the shaft is being rotated and MCU catches this noise as a valid signal).

What I did wrong and how can I fix it (if it's still possible)?


texts: ways to control resistance by microcontroller

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Q. I have a (fuel) gauge that accepts a configurable resistance range (0-500 ohm, two-wire, one to ground), which I want to control with an micro controller (Arduino Pro Mini or Nano with an Atmel 328P).

Some considerations:

I'm already using SPI for a CAN bus, and am hesitant to add another device on the SPI bus, as the CAN bus is rather mission critical. i.e. don't want to miss CAN messages. Also it requires quite a lot of wires.
I also already use i2c, adding an i2c device would be straight forward in this application. I mention this because I see i2c digi pots out there.
Accuracy is somewhat needed (say <10%). I've seen that most digi-pots have an relative accuracy of max ~20%. However, they continue to explain that the relative accuracy is low, but I'm not sure what that means.. this question probably merrits its own topic though, so forget that for now unless it's a one sentence answer.
Ideally the components required are through-hole/DIP, but this is not a hard requirement.

I think the gauge is designed to be controlled by a rheostat, as it requires a linear resistance range, correct me if my assumption is wrong).

What would be my options? Could it somehow be done using the Arduino's analog output? When researching, I've come across Digi-Pots, DACs and JFETs. But the application was never the same as what I'm doing, often using PWM and more geared towards voltages then to resistance...

Update; Some more details:

Fuel gauge has two wires, a positive and a negative. The positive wire sends out a 5V, 17-19mA current (for those who want to know, it's a Speedhut gauge).
Arduino is 5V and, depending on which analog PWM pin you use, outputs a PWM signal at either 490Hz or 977Hz. The duty cycle is controllable in the code between 0-100%.
The application is automotive. The vehicle is 24V. The gauges are 12V, fed by a small buck controller. The gauge has a microcontroller, and I suspect runs at 5V.

Update; output not as expected:

I'm measuring a constant ~19kOhm on the circuit output (multi meter between "output"-wire and ground). I would expect it to vary as the PWM duty cycle changes.

I've not hooked the fuel gauge up yet, as first I want to make sure the circuit is OK. I have hooked up my multi meter instead. Maybe it simply doesn't work like that, perhaps the multi meter current output is too weak?
PWM output is correct according to my multi meter; it gives me a nice 490Hz 0-100% duty cycle.

I've attached a photo of my breadboard layout. My phone doesn't have a great camera, so i've added the names of the components. What's not clear on the photo is that both the 10k resistor coming from the LM and pin 3 of the Mosfet are on the same row 10, the tiny 10pF resistor is on rows 10 and 11. I think I've copied the schematic pretty accurate. I did not have some exact resistor values, so I've used close ones, which I think should be good enough to see output.

I'm not just chucking my problem over the fence, but any pointers would be welcome, I'm still only a few months into this stuff. :) Thanks!

*typo: 10pf = 10nf


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All the textbooks and articles regarding diodes talk about forward bias or reverse bias and break-down voltage. I don't know why the break-down voltage is never related to the forward bias?

I think the same thing could in reality happen in forward biased mode as it can happen in reverse biased mode. If we apply lot more voltage than 0.7 V in forward direction, this is still bad, and it may lead to a break-down condition.


texts:
I am testing many solutions for wireless power transfer, among the solutions i am evalutating all of them (but one) are based on switching FETs (serie resonant halfbridge, class E, push pull..) so very good efficiency, but to eliminate this one (colpitt oscillaotr) my supervisor is asking me for good arguments because it has the advantage of being the cheapest solution.
For this exact circuit i simulalted, (with a secondary coil coupled to L1) and a load behind and i have less than 8% efficiency for a huge load range. (i didn't change a thing since i have a relatively poor background in analog electronics. in a famous MIT wireless powertransfer paper, they had 80%.

So my question is:  How Can this oscillator be more efficient (with a more optimal design), or is there some strong arguments like : No there will always be huge losses in the biasing circuit or in the transistor because it is will always conduct current with non null Vce.. or somethign like that

thanks


texts: How calculate inductor discharge time through LED?

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UPDATE

Overnight I realized I'd been sleeping as I read part of the textbook I've been using or at least didn't quite fully grasp the purpose of inductor volt-second balance. I added the results of applying that here in an answer below.

I'm doing a detailed analysis of a joule thief circuit as an exercise in my independent study of switching converters. I'm finding it a terrific "lab" exercise as I'm starting out because the circuit's simplicity (5 nodes total) limits the possible interactions, making for an accessible "on-ramp" to the learning curve. I've been really happy with the number of basic behaviors I've been able to get clear in my head as I've simulated it and observed its operating waveforms on the bench with my scope.

I decided I wanted to derive a set of formulas to describe the basic characteristics of the circuit, things like the duty cycle (D, D'), frequency/period, etc.

I have an expression for D, but I'm stuck on how to approach an expression for D'.

The circuit looks like this:

I started with \$I_C\$ (collector current), because that determines \$D\$:

During the on stroke:

\begin{align}
I_B & = \frac{V_R - V_{BE}}{R} \approx \frac{2 \cdot V_{in} - 0.7}{R} = \frac{1.3}{1000} = 1.3\,\mathrm{mA} \\
\\
\frac{dI_C}{dt} & = \frac{V_L}{L} = \frac{V_{in}-V_{CE}}{L} \approx \frac{0.9}{0.0003} = 3000\,\mathrm{A/s} \\
\\
I_{Cmax} & = \beta I_B \approx 150 \cdot 1.3 = 195\,\mathrm{mA} \\
\\
I_{Cmax} & = \frac{dI_C}{dt} \cdot D \\
D & = \frac{I_{Cmax}}{\frac{dI_C}{dt}} \approx \frac{0.195}{3000} = 65\,\mathrm{\mu s}
\end{align}

So far this corresponds to the simulation surprisingly well.

However the discharge of L through the LED is non-linear in both voltage and current and I need a little help setting up the equation:

Here's what I know:

\$I_D\$ starts at \$I_{Cmax}\$ and ends at zero.
\$I_D\$ = \$I_L\$ during this period because the transistor is off. So I'm sure \$V_L = L\frac{dI}{dt}\$ holds and \$V_C = V_{in} + V_L\$.
The right answer is \$D' \approx 17 \mathrm{\mu s}\$.
My qualitative hypothesis is that at each moment, L and the LED reach an equilibrium between the slope of current decrease and \$V_L\$, somehow tracing out the forward V-I characteristic of the LED in the process. I do notice that the decline in \$V_L\$ looks awfully linear for most of D'.

Anyway, I was wondering if any headway was possible on this, perhaps by way of a differential equation or a clever approximation. Without D' I can't get T which means I can't get the oscillation frequency (by this approach anyway).

Can anyone offer insight into how I might proceed?


texts: The offset null pins of the LM741CN op amp don't seem to work properly

texts:
simulate this circuit – Schematic created using CircuitLab
I can't nullify the output offset voltage of an LM741CN op amp.
I tried the circuit mentioned in
the datasheet, but with no luck.
I connected the V- pin to ground of a 15V power supply and used a 10k pot as mentioned and the output is just stuck at +rail and doesn't even move a bit.
I also tried to use a 9V battery on a potentiometer to just compensate for the input offset voltage with the wiper end on the + pin. It worked and I got 30mv on the output but it also reads a 50 mA on the power supply and the op amp gets really hot.
I edited the circuit to bias the inputs to half of the supply voltage and made it my virtual ground now should be ok that the -v terminal is 7.5V below the inputs which allow for maximum swings on both sides like the circuit below. Are there any other cautions to take into account about this circuit? If there's any suggestions about any modifications or pitfalls in this circuit would be appreciated.

simulate this circuit


texts: Analog beamforming vs digital beamforming

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I am reading some research articles on wireless communication where they talk about beamforming techniques and their differences in Multiple antenna Tx-Rx systems (MIMO). It says analog beamforming can only support one stream( Or one user) at a time while digital beamforming can support multiple streams and users.

Can someone clearly explain why is this the case?

To ask more directly,
why cannot I create beams in multiple directions carrying different information streams using an array of antennas while using analog beamforming?


texts: How the delay locked loop (DLL) align the clock?

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The delay locked loop is used for align the clock in integrated circuits. In the IC there are no of flip flops and other devices. I want to know that how the DLL align the no of clocks going to different flip flops.

Sorry for the wrong English.


texts: Balance charge unknown number of LiPos in series

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This exact question has already been asked here, but no answer was given so I'm reposting it.
I want to charge an unknown number (between 1 and 8) of 1s LiPos in series with my balance charger (ISDT T8). I know how to manually connect a fixed number of LiPos together to charge them in series, but I would like to make a circuit which would allow me to (ideally passively) connect an unknown number of batteries in series.
Basically, I want the positive terminal of the circuit to always be connected to the positive terminal of the bottom-most LiPo battery connected. Here is what the connections would look like if I had 3 LiPos connected to this circuit and then decided to remove the 3rd one.

The task seems trivial but I've spent quite a bit of time searching and thinking of how I could achieve this automatically but didn't find anything. I don't want to have to manually reposition the positive terminal of the circuit because according to Murphy's law an error seems inevitable. Can you people please help me?


texts: I am using an RS422/RS485 driver to send Arduino 5V logic data over longer distances. I use the SN75174 driver for this purpose. In order to avoid ringing, I am not sure if I have to connect a series resistor on the data input of the driver. In which cases is a series resistor for protection of ringing and current limiting necessary and how do I chose the resistor value?


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I am planning to use this UART-to-RS485 module :-
http://www.elecrow.com/uart-ttl-to-rs485-twoway-converter-p-1545.html.
This module is bidirectional and uses a single pair of differential signal to transmit/receive data. My question is how is the chip deciding whether it has to transmit data from TXD to A+ B- or from A+ B- to RXD?. Shouldn't there be 2 pair of differential signals, one pair for TX and the other pair for RX? What is happening in this module??


texts: How do I calculate period of synchronous counter?

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So how do I calculate maximum frequency if this values are given:
\$T_{Hold-ff}=0.2ns\$,
\$T_{Delay-ff}=2ns\$,
\$T_{Delay-nor}=0.3ns\$,\$T_{Delay-nand}=0.4ns\$,\$T_{Setup-ff}=0.5ns\$.

I thought about: \$T_{Delay-ff}=2ns\$+\$T_{Delay-nor}=0.3ns\$+\$T_{Setup-ff}=0.5ns\$

Is that good?

Also how could I calculate Response time (time from the clock edge on the clock until output A, B, C)?


texts: H-Bridge motor driver not working properly

texts:
I'm trying to make this long post a little easier to read, and this is the only way I know how. So I apologize if this looks too much like a school report.

What I'm trying to do:

As part of my final year college project, I am trying to build a driver circuit to drive my magnetorquer (Think of it as a solenoid within a metal coil) , I am using this magnetorquer : www.cubespace.co.za/cubetorquer . I intend to supply bi-directional current to it using a H-bridge motor driver, I am using this motor driver chip
I will be controlling the input pins (InA and InB) using PWM signals from my arduino. As a test, I am just using a simple arduino program that varies the duty cycle of the pwm output in Pin 5, and sets Pin 6 to digital low. Shown below is the circuit connection of my circuit:

 Note that the batteries would represent my DC Supply(I am using 5V to power my chip) , and the inductor represents my magnetorquer. Also, assume that the bottom left pin of the IC is pin 1.

What went wrong:

I have observed that as I am drawing an unusually low amount of current, compared to what I should get theoretically(V=IR , resistance of the magnetorquer is shown in the link above ). When the duty cycle of my PWM signal is set to 50%, the chip only draws 0.030A of current, in that case the resistor of my magnetorquer would be R=V/I = 2.5/0.03 = 83.33Ω! Which is almost thrice of what is stated in the link above!

I am using an oscilloscope to measure the output voltage across my magnetorquer, when I set my duty cycle to 50%, what I get on the oscilloscope is a square wave that has max and min voltages of 2.5V and -2.5V respectively. If Pin 5(OUTB) of my motor driver is always 0, I should expect to see my output voltage vary from 0-2.5V right?

Also, when I set the duty cycle to 100%, I should be expecting to see 5V on my oscilloscope, but what I see is a very small DC voltage ( about 100mV ) which is effectively 0.

What I've tried:

I tried connected the negative end of my magnetorquer to ground while keeping the positive end at Pin 8 (OUTA) of my motor driver chip, but nothing changed.

I have tried shorting Pin 5(OUTB) of my motor driver chip to ground, didn't work either.

I have also tried connecting a the second channel of my DC power supply ( Set to 2.5V ) to pins 6 and 7 (InB and InA ) of my motor driver chip, when I do this the current jumps up to about 0.150A and doesn't increase when I increase the supply voltage of the second channel of my DC power supply.

I'm currently really out of options, at this point I can really only assume that my motor driver chip is broken. Is there something that I am not doing right?

Thanks and sorry for the long post.


texts: Is there a difference between nested if statements and exhaustive?

texts:
Is there a difference between the two?
I would expect maybe the first has delayed evaluation of conditions?
if(A='1') then

if(B='1') then

end if;
end if;

Over

If(A='1' AND B='1') then

end if;

```


texts: Dismantling 110v DC LiFePo4 Battery Pack

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I've inherited a 110v battery pack that used to be used for a solar array made of 34 each 100 amp hour LiFePo4 3.2v for a nominal voltage of 108.8v all together. I'm getting about 90v total from the leads off the pack, so I know that it's severely undercharged. I'd like to take them all apart and diagnose each one to see how they're doing.

What is the correct procedure to safely disconnect each battery from their series set up? Do you need me to supply pictures to better show how the batteries are wired? I'm asking because I've only dealt with 12v Lead Acid Deep Cycle batteries so far, 10.9% of the 110v I'm getting into. If I can safely recycle any of these for another project I'd be elated.

(As for the batteries, the last time they had a full charge was 3 weeks ago, they've probably only been through 300 cycles @ 50% discharge and the reason they're discharged right now is a human error... they were left attached to a DCDC converter :-( )

Thank you all.


texts:
I'm working on a project on the Samsung Galaxy S smartphone. I need to know some additional information on its accelerometer that I can't find. Accelerometer datasheet

I need to know following details:

which type of measurement range they use? +-2g , +-4g or +-8g ?
noise depend on the bandpass filter used by the smartphone: how much is the band?
there is some way to evaluate from this data sheet the standard deviation of drift process of the sensor?


texts: Resistor between Line and Neutral in SMPS

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In Below SMPS Circuit ( Credit to:- NXP SMPS Design Tool ), in Red mark what is function of this resistor and why mid point of register is connected to Aux biasing of transformer.

Thanks in advance.


texts: Decoupling caps distance from the IC pins

texts: Is there any equation which can answer the max allowable distance for the decoupling capacitor to be placed for  a max. frequency that is used?


texts: How to provide power to a rotating circuit?

texts: I want to build something with my unused fan. I am planning to put a lighting circuit using LEDs and a microcontroller (ATmega, Arduino Nano, or something), thus creating some kind of image from the rotating LEDs. However, I have no idea about how to power the circuit. It would be nice if I can power it through 220V from the fan + regulator + cable to circuit (I prefer not to use a battery), but the cable used to power the circuit in this case will always be twisted. Any idea?


texts:
Using the image below as a reference,

What would the two graphs look like if switched from a, to b, then back to a (instead of c)?
Why is a resistor used in the circuit? Alternatively, what would the graph look like without it?
Could the first voltage spike be taken care of with a voltage regulator and the second with a diode, or would both be handled by the regulator?


texts: Measure voltage and amperage drawn by an Arduino?

texts:
so I'm in a green engineering class in high school, and my friend and I have been tasked with a special project, measuring the amount of power drawn by an arduino so that we can determine the energy efficiency of each person's project (automated model homes).

My plan is to run the DC wall power supply through a circuit that will determine the voltage and amperage drawn by the arduino from the DC wall power supply, and then output the power to the Arduino (where it was going originally. The big problem here is that I don't know the equivalent resistance of the Arduino, because it varies as the Arduino does different things (turns on motors, blinks lights, etc.).

As the output of this ammeter/voltmeter circuit I would like to have two leads that output an analog voltage that correlate to amperage and voltage, which I can then read from Arduino code.

The code is not the problem here (duh, this is an EE site), I just don't know enough about circuits to make an ammeter that has an analog output.

For voltage, I thought about just running the positive of the power supply to an analog pin with a 5MOhm resistor in between. Would this work?


texts:
I am developing an application on the 8051 chip and I'm using Multisim to simulate the connection. I have connected RS to P3.0, E to P3.1, D0-D7 to P2, Vcc to 5V, GND and Vee to ground. I just want to display a charcter to test the LCD with the chip. The code I write for it is:

P2 = 0x00;
lcdinit();
writecmd(0x81);
writedata('H');

The functions are defined as follows:

void lcdinit(){

    writecmd(0x38);
    writecmd(0x0f);
    writecmd(0x01);
    writecmd(0x06);

}
void writecmd(int a){
    RS = 0;
    P2 = a;
    EN=1;
    Delay(150);
    EN=0;
    Delay(150);
}

void writedata(int a){
    RS = 1;
    P2= a;
    EN =1;
    Delay(150);
    EN=0;
    Delay(150);
}

I have tried the above code, it compiles fine but no result on the LCD which should print "H".

The help is highly appreciated!


texts: LED Bulbs - parasitic or electric issues?

texts:
My house was built in 2005, I have no dimmer switches, voltage is about +/-4%. I’ve bought very cheap and higher quality LED bulbs. Many of them have been dying in 6 months or less, always starting by flickering (slowly).  My refrigerator is 4 years old and the LED that lights the water / ice area is flickering. I’m less well versed in power supplies and 120V design, so I have questions.

1.) Is there any way the refrigerator LED would be related to what is happening in the rest of the house? I believe the answer is no but please correct me if I’m wrong
2.) I don’t have a scope but can get one. Is there any sort of parasitic or anything that could be going through the house causing death much too quickly?
3.) I haven’t started tracking fixtures specifically but it does seem like closet and others always die quick. Will a cheap fixture (literally screw terminal and three wires) have an effect? Everything is properly grounded

I’m going to start tracking individual fixtures and pair them with a better (Philips) / cheap (Costco Feit electric) bulb combo but in the meantime - what am I missing??

**UPDATE: See two pictures attached. Resistor burnt on top side, bottom side shows thermal issues on pads for the FET and the larger inductor and position C3. Note the MLV - doesn't seem like a surge event.


texts: Circuit to identify phase difference between capacitor voltages of two different RLC circuits without loading it

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I am looking for a circuit that can translate phase difference of two sinusoidal signals (operating at ~1MHz) to analog voltage swing of 0 - 5V.

The signal A & B comes from the capacitors of two different RLC circuits.The conditioning circuit should not load the circuit as it will change the RLC filter circuit operating point.

I could think about digitizing sine signal + EXOR + filtering but, the RLC capacitor that I am using is about 50pF and using MOSFET for digitizing didnt help as gate input capacitance did change the operating point of the previous stage.

Another option, I was thinking is using a voltage follower opamp + EXOR + filter and I am looking for opamps that can have inputs > 20V with supply voltage of 5V and operating at >1MHz. Any ideas?

Additionally, I came across CD4046B, but I believe that it also needs digitizing before it is fed into the signal & comparator Inputs.

Thanks in advance!

EDIT1:

Below is a rudimentary circuit (Please ignore part numbers). If the loading is limited to a few 10uAs, then I beleive the operating point would not shift that much.


texts: Building an electret microphone amplification circuit, it's not working

texts:
Here's the schematics:

The circuit is powered by a 9V battery. There is a voltage divider that gives 4.5V between R4 and R5, this voltage is applied to the negative pole of the electret microphone (V2). The rest of the circuit is the first stage of an instrumentation amplifier built with a TL-082 op-amp and the condensers are there to remove the 4.5V bias before sending the signal to the mono jack.

The microphone by itself works perfectly, when it's connected to the amplifier the computer only gets a small noise. Could any you guys help?


texts:
I am studying Schilling-Belove Electronic Circuits, 3rd Ed. where in its second chapter under the "Maximum Symmetrical Swing" section it gives an example where the base current is kept constant and the beta is varied from 200 to 400 which makes the collector current reach the edge of the saturation value almost... and then it says.. "... (hence) the transistor is biased with a constant-emitter rather than a constant-base current".
What I don't understand is how can the emitter current stay constant while we can vary the base current to our will to satisfy design requirements.. It isn't that Ib and Ic can adjust between themselves keeping Ie constant.. Ib and Ic themselves are constrained by beta.. Or is there something hidden in the language I am not getting through..


texts:
I am planning to connect an Omron ZL1-series 4-20 mA level transmitter to a 0-10V input on a PLC.
To do so, I have to convert the current to a measurable voltage by connecting a 500 Ω resistor to the PLC's input.
However, in the documentation for the LT This is stated:

Analog output: Current output: 4 to 20 mA, maximum load resistance:
300 Ω (The output is 20 mA for the nearest point in the measurement
range in respect to the Sensor and 4 mA for the farthest point.)

Does this mean I can't use it as a 0-10 V input?


texts:
I'm using an ATTiny2313 to act as a serial concentrator. It only has 128bytes of RAM. I think I'm running out of RAM during the ISR. My question is how much RAM (stack) does an ISR use to save the context (registers). I.e. if I use ISRs how much will I have left out of 128 bytes.
Is there a way to detect stack overflow?


texts: How to design low pass filter using Sallen-Key architecture?

texts:
I have hard time to design a 4th order low pass filter using Sallen-Key architecture with corner frequency 33kHz and overall DC gain of 0dB.
I have f01 (normalized) =1, Q1= 0.541, fo2(normalized)=1 and Q2=1.306.
What are the resistor and capacitor values if I consider C1=1nF for the two stages? How the op-amp circuit will be?


texts:
This is probably a really simple question, but I can't seem to find a definite answer anywhere.
I'm guessing 50Ω cable means 50Ω per unit length.

What unit length is this? If this is not how its defined, how is it?


texts: Charging a L-ion battery 3.7V/850mAh with terminal connectors

texts:
How do I charge a battery with a connector as shown in this link:

https://uk.farnell.com/bak/lp-503759-is-3/battery-lithium-pol-3-7v-1300/dp/2077882?MER=bn_level5_4NP_LastViewed_1


texts: Open drain voltage detector NCP301LSN45T1G

texts:
I have to use a voltage detector to detect a decrease in voltage to reset a microcontroller. I have found the NCP301LSN45T1G to do this.

But I have a question about the Reset Output current (N-Channel Sink current).

How do I have to consider this parameter? Is it used to calculate the pull up resistor?

I thank you for your answer. So If I have understand your explanation I have to use a pull up resistor of 796 ohm to obtain a 5V at the output as explained with my schematic. Is it right ?


texts: Half Wave Rectifier - Voltage Signal Across Diode vs Voltage Signal Output of Diode

texts: I am learning how to work rectifiers and I build a half-wave rectifier to test signal in simulation. When I add probe output of diode and voltmeter across the diode, the signals are different. It seems fair but I cannot explain why signals are different. What is (in technical terms) output signal of diode (VF1) ( It is rectified signal as know) and signal across diode (VM1)?


texts: Can you drive a logic level IGBT directly from a micro controller?

texts:
My question pertains specifically to devices like an EcoSPARK®2 400V, N-Channel Ignition IGBT.  I'm investigating the requirements for building an electronic ignition system for a go cart.  This would energise the coil and thus generate a spark.  You'd be firing at a maximum of 175Hz.

The datasheet uses the following test setup for inductive load testing:-

The datasheet also says that the IGBT has a logic level gate drive.  And from the performance curves and switching characteristics table, it appears the RG = 1KOhm.  I'm not sure how to assess it's 21 nC gate capacitance wrt other similar devices.

However this seems to contradict most of the answers on the IGBT tag. Lots of gate drive is recommended there for quick up and down switching. Some even suggest going below 0V to guarantee turn off.  A 1KOhm resistor would cap the drive to an absolute limit of 5mA (5V logic) which doesn't seem a lot.

In all honesty, I had made preparations to use a TC4422 drive chip but maybe I don't need to. Is this just a newer form of IGBT and I can directly drive it from a micro controller output pin?  Too good to be true?


texts:
Can a cheap RTL-SDR (with suitable software) plus a variable frequency digital output (for noise or square wave generation) be used to construct an inductance meter suitable for measuring values in and around the range of 0.01 to 0.1 uH?

Are other even lower-tech methods (plus a computer or micro-controller) possible (e.g. programmable digital output and a simple A/C voltmeter, etc.)


texts: Amplifier with bass, treble and volume contol

texts:
I'm trying to make a an 10 watt stereo amplifier with bass, treble and volume control. I found the schematic of a 10 watt amplifier ( first image ) and a schematic for for the bass, treble and volume control ( 2nd image) my question is how do i combine the 2?
where do i connect the 1st circuit to the 2nd circuit?


texts: Why are two PID controllers needed for FOC (Field Oriented Control)?

texts:
I've been looking at code to do FOC and noticed that two PID controllers are usually used for torque control -- one that keeps Id near zero and another that maximises Iq.

I understand why Id should be minimised and Iq should be maximised.

What I don't understand is why two PID controllers are needed to solve for what as I understand is essentially one unknown.  My understanding (which probably needs correcting) is that the only goal of FOC is to figure out the torque and speed induced phase offset between the voltage and current which is caused by the windings' inductance and back-EMF.

If this is correct (that knowing this phase offset at any point in time would be enough to optimally determine what voltage to put on what windings) then why isn't there one PID loop which optimises for the percent of the output power that goes to Iq?  Something like trying to get Iq/(Id+Iq) to be as close to 1 as possible.


texts: AT+CNBP command for SIM5216E cellular module

texts:
I am trying to use the the simcom AT command set to change the preferred band on my "SIM5216E" module. I know I need to use the AT+CNBP command, but I am unsure of what code I need to enter to select WCDMA 850 only.

The above screen shot is of the command manual. The whole manual can be found here: "http://mt-system.ru/sites/default/files/documents/simcom_sim5215_sim5216_atc_en_v1.21.pdf" I am unsure of how the number system is supposed to work. If someone could provide me with the WCDMA 850 code it would be much appreciated.

Thank-you for your time.


texts: Best solution to get 3.3V from 5V-20V @ 250mA

texts:
For my Super OSD project, I need a +3.3V supply at 250mA from a variable input of 5.5V to 20V. Cost is a concern, as is size. Originally, I considered an LM317 in a SOT-223 package, due to the small size. Unfortunately, it's difficult to get a heatsink for SOT-223 packages.

Then I did some calculations; the LM317 would be dissipating up to 4.175W with 20V input and 250mA of load and with a θJA of 140°C/W, the LM317 would cook along nicely at 584°C above ambient. So not practical.

The next solution would be a little buck converter, but I'm looking to get a small design and a cost of <$3. Does anyone know of an ideal chip for the job? Or is it still possible to use a linear regulator? I'd prefer to do so, but getting rid of the wasted heat is really a problem. Power efficiency is not critical for this application, as an electric motor will be drawing 10's of amps, compared to the few hundred mA for this module.


texts: Problem to find ALPS Encoder with only reference number

texts:
My ultrasonic tank uses two ALPS encoders. The problem is that both are defective and I would like to replace them.
However, I have a lot of trouble finding the same ones. Please would any of you know the reference of these items? (please find photo attached)

Thank you very much in advance for your reply.


texts: H bridge system for inverter using n channel mosfets

texts:
Hi, I have been constructing (transformer based) homemade inverters mostly using CD4047 as my drive circuit. Then one day while I was doing my research online, I came across an H-bridge system — one that I had never thought of. I was impressed with the fact that the system allows the use of a transformer without centre tap.

For a couple of days I have been trying out the circuit above which I downloaded from the web, but my problem is that the circuit seems to have been designed to be used with SG3525, and in my experience I have never constructed a drive using SG3525.

OK, I tried using CD4047 with the H-bridge system, and for like 1 minute it seemed to be working. But all over sudden, two MOSFETs blew off, one from the high side and one from the lower side.

So my question is, what should be done to the circuit to avoid MOSFETs blowing? Initially I wanted to design a 24V 6000W inverter charger; the MOSFETs I used were 4× IRF064.

Also, if you can try to advise me what to do if I wanted to add more  MOSFETs in parallel and charge the batteries using the same MOSFETs and transformer, I will really appreciate it.

Below is my drive circuit using cd4047.


texts:
I have battery power (9v) for stepper motor (auto-tracker for telescope mount). I need micro stepping and high torque (0.1 N*m). I decided to use bipolar stepper and A4988 because there are cheap modules from eBay.

But: I need to rotate stepper very slowly (about 1 step per second), so most of time the motor stay without rotation and A4988 produce a holding current, but I need no holding torque (there are no external torque that can rotate my motor).

How to maximize battery life in my case. Maybe just set "enable" pin of A4988 to 1 between rotations? But I have another questions in this case:

1) Can I lost steps if I will set enable pin to 1 between every steps? In data sheet there is note that if I will use sleep pin, then after wake up A4988 go to HOME state, so I will lost steps. But there are no notes about behavior of enable pin.

2) How microcontroller can know when step have executed (before set enable pin to 1)?

Maybe there are another solutions. I need at least 5 hours of 9v alkaline battery, 0.1 N*m, single step each second.


texts: Can I calculate minimum rise time of a transmission line if I know the length and the loss tangent?

texts:
Overview: I am trying to work out if it's possible to transmit my 1.2Gbps MIPI data down a 600mm long flexible PCB strip. Assuming I have the impedance correct, will the signal still be degraded by the loss tangent of the dielectric?
Some background: I have already made some test strips, 180mm long using DuPont's AP laminate, and have discovered that the rise time on each is 250ps. When I produce a 600mm long strip, the rise time will be significantly longer.
According to the MIPI spec, I need to achieve a rise time between 150ps - 250ps for my 1.2Gbps DDR clock.
Possible solution: DuPont have another laminate, Pyralux TK, with a lower loss tangent.
Question: Is it possible to estimate the likely benefit of this alternative material. Is there some simple rule of thumb, like: "half the loss tangent implies half the rise time"? Or is this something I simply have to simulate in Polar?
My attempt at an answer: This is a graph from the Pyralux datasheet:

According to my calculations, a rise time of 250ps, gives a bandwidth of 1.4Ghz. Looking at the graph, that equates to a loss of about 0.05dB/cm. Over 60cm, this would be a loss of 3dB, which is equivalent to an amplitude loss of 1.413.
That doesn't seem too bad, although I'm not sure how it relates to my minimum rise time in practice. Do my calculations make sense?


texts:
In the below circuit, the circuit maintains a constant current on LED.
My question is after the LED there is a voltage of 18V, still, need to be dropped. Will the NPN Transistor heat up while dropping the voltage?
Also, the voltage source to led will vary from 12V to 20V. How can we modify the circuit? Or the existing circuit is fine?


texts: Lead Acid Battery Charger Design Factors

texts:
In any lead acid battery charger how does the per ampere rate of the battery being charged factor into the design. I think. You have to worry about the current voltage, and the current current being drawn by a depleted battery at charge time ?

Say I have two different batteries that I wish to charge. A 2.3A and a 250A one.


texts: Universal voltage input using depletion mode N-FET - Advice

texts:
In an attempt to idiot proof a device I am designing that needs both 24V DC and 120V AC inputs for logic, I set out to create an input system that could handle either voltage going to a simple 3.3V micro controller. Below is the schematic of what I came up with. Simulation shows that using a Depletion mode FET combined with a sensing resistor, I should be able to limit the input current regardless of the input voltage. This with an opto-isolator and rectifier before hand should effectively allow me to sense 24 and 120 volts interchangeably.

I'm new to depletion mode Mosfets and did not see much about this type of application other then an app note from Infineon here.

Below is the basic circuit I am describing, the 180V input can be exchanged with a 24V dc input. this is basically the input pin to the system.

Edit:

The simulation only has -0.6V Vgs to limit the current, that does not match the expected -2.1 - -1.0 in the datasheet, but that is for a mere 56uA. Turns out that the data sheet later on lists the variation of Vgs and my model falls within that range.

The one issue I found in the data sheet so far with this plan is that it appears that N-Mos Depletion Fets suffer from thermal runaway when used in this fashion... At least that is what I gather from the image below.

Can anyone give me any advice on if this is a good path to take?


texts: Why do bidirectional (TVS) diodes sometimes have a 'direction' mark?

texts:
TVS diode with marker

Some components that are needed to be be in a certain direction (like most diodes, and some capacitors) there is a white line over the component to show the direction.

But why is this done for a P6KE43CA, Bi-Directional TVS Diode, 600W, 2-Pin DO-204AC like the picture below. Does the direction matter since it is bidirectional?

TVS diode without marker

This is how mine look like from P6KE15CA; sorry for the bad picture, I do not have the TVS diodes at hand so used a screenshot crop from the page I bought them from:


texts:
I am learning 8051 coding. I came across the instructions of these forms ADD R7 and ADD A, R5. Now, since ADD is a mathematical operation, which should always take place in the accumulator, isn't the ADD A, R5 command redundant?

And secondly, how can these be a 1 byte instruction? I mean, there should be 2 bytes, one for the opcode which says that it is an add operation, and the second byte will have the byte value that is to be added to the accumulator. How can both be squeezed into one byte?


texts: Problem about the properties of convolution

texts:
I have a difficulty to understand the convolution integral itself. Can anyone please explain what are the differences between the following 3 convolutions?

x(t)*h(t), x(-t)*h(t), x(-t)*h(-t).

Thanks.


texts:
I have two recorded audio voice WAV files I have recorded by saying "Good Morning" twice.

I want to compare the two audio files and say both are identical.

How can I do that?
What is the right approach to achieve this?


texts: Buck Converter Design Issue: Load voltage capped at ~9V the Vin is max 24V

texts:
I'm very stuck and I've run out of solutions.  I designed a buck converter in ltspice which I then physically made.  It worked decently at high voltages, but at low voltages, the gate signal just becomes warped and alot of heat is dissipated.  That's not even the main issue, the issue is that the circuit only works if I'm using an oscilloscope and scope probe to monitor the signal on my microcontroller which provides the pulse signal (in this case a teensy 3.5).

I've attached an updated schematic of my simulation:

The DC-DC converter that I would use physically is much simpler than the LTM8057.  I'm simulating with the LTM8057 to see if the problems I was having with my buck converter was DC-DC converter related or otherwise.

I've narrowed down the issue to the gate driver (TC4432).  The thing has no reference voltage and then uses my Teensy/scope probe has a high impedence to ground.  This causes my Teensy's to blow up (I've fried 3 so far).  Reading some online sources suggests that the gate driver should have a reference to the source side of the circuit (on the right of the MOSFET).  My idea was to just link the Vout- of the LTM8057 to the right side (source) of the MOSFET.  But no matter what I do, the circuit doesn't run.  It only runs in the above configuration where even at maximum duty cycle, I only get 9 V on the load:

I have no idea what to do now.  I don't want to waste time soldering another circuit.  The last circuit I built confirmed that there was something badly wrong:

At lower duty cycles, it becomes horribly inefficient.  It only worked at higher duty cycles because I was scope probing the Teensy to monitor the output PWM signal.  I thought it was a common ground issue, but rearranging my grounds didn't work.  So I've fallen back to simulations again.

So finally my question is: In the above simulation, how do I get full range of voltage across my 10 ohm load?.  Then I can try to recreate it physically.

Thanks!

EDIT: If the gate needs to be driven with a higher side voltage more than or equal to the source (24 V), then why does this following schematic work?


texts: How should I lay out timing matched traces?

texts:
Two nets on my PCB need to be matched to within 100 mil, preferably 50 mil.

Currently I am doing this (see below); they are matched to about 10 mil.

However I am worried about whether I am Doing It Right (TM). Is there a better way?

I am using gEDA/PCB which unfortunately doesn't have an auto trace length matcher, but it does have a trace length calculator which is good enough for matching these.


texts:
I have a STM32F769NI, Cortex M7, using FreeRTOS, debugging using a JLINK inside of Rowley CrossStudio.  The issue at hand is no flag interrupt cause.  I2C3->ISR = 0x8000 which is the TXE flag, and I have only enabled the TXIE and STOPIE flags in CR1.

Uncommenting the rptr++ line "fixes" this problem.  I have tried changing stack sizes and other things, but the source of this problem is pretty unclear to me.  Could this be some completely unrelated thing somewhere else like freertos setup?

Edit 1: The bad sequence happens after the End of Transfer, perhaps portYIELD is in the wrong place. Its like the stack calls it back into the isr rather than a real interrupt.

static uint32_t writeI2Cx(driveTarget *target, uint8_t address, uint8_t *data, uint32_t len) {
  target->buffPtr = data;
  LL_I2C_HandleTransfer(target->I2Cx, address, LL_I2C_ADDRSLAVE_7BIT, len, LL_I2C_MODE_AUTOEND, LL_I2C_GENERATE_START_WRITE);
  target->I2Cx->CR1 |= I2C_CR1_TXIE | I2C_CR1_STOPIE;
  ulTaskNotifyTake(pdTRUE, portMAX_DELAY);
  return (uint32_t)target->stat;
}

static volatile uint32_t rptr = 0;
void I2C3_EV_IRQHandler(void) {
  BaseType_t xHigherPriorityTaskWoken = pdFALSE;
  uint32_t reason = I2C3->ISR;
  if (LL_I2C_IsActiveFlag_RXNE(I2C3)) {
    /* Call function Master Reception Callback */
    //Master_Reception_Callback();
  } else if (LL_I2C_IsActiveFlag_STOP(I2C3)) {
    /* End of Transfer */
    LL_I2C_ClearFlag_STOP(I2C3);
    LL_I2C_DisableIT_TX(I2C3);
    LL_I2C_DisableIT_STOP(I2C3);
    target_R.stat = 0;
    vTaskNotifyGiveFromISR(xD_R_I2CTaskHandle, &xHigherPriorityTaskWoken);
    portYIELD_FROM_ISR(xHigherPriorityTaskWoken);
  } else if (LL_I2C_IsActiveFlag_TXIS(I2C3)) {
    //Transmit one byte and increment pointer
    LL_I2C_TransmitData8(I2C3, *target_R.buffPtr++);
  } else if (LL_I2C_IsActiveFlag_TC(I2C3)) {

    //LL_I2C_ClearFlag_TC(I2C1);

  } else if (LL_I2C_IsActiveFlag_TCR(I2C3)) {

    //LL_I2C_ClearFlag_TCR(I2C1);

  } else if (LL_I2C_IsActiveFlag_NACK(I2C3)) {

    LL_I2C_ClearFlag_NACK(I2C3);

  } else {
    /* Call Error function */
    __NOP();
  }
  //rptr++; <-- Uncommenting this line "fixes"
}
```


texts: LTspice (XVII) Use component instance name as a parameter

texts:
I am trying to to simulate a ferroelectric capacitor using simple schmitt triggers subcircuits :

simulate this circuit – Schematic created using CircuitLab

I would like to pass {R1} as a function of each subcircuit instance names (or from a table with each desired values). The goal is to do something like this :

    R1=100k*(instance_number)

that will effectively increase the R1 value for each new component created.

As I need a few hundred subcircuit in parralel with different {R1} values manual editing is not optimal.

EDIT:

The aim of this project is to reproduce the electrical measurement of a ferroelectric material similar to what can be seen here:

This can be achieved by a large sum of ideal schmitt triggers with capacitors in series.


texts: Verilog assigning fractional value to integer

texts:
I am new to Verilog, but have some coding experience in VHDL. While reading someone else's code, I came across the following part:

genvar i;
generate
  for (i = 0; i < 8; i = i + 1) begin : gen_for
    integer p = (66.0*i)/8.0;
    assign data[p + 1] = ...

My doubt here is what will be the value of p rounded to?
Will it be rounded to the nearest integer or to the largest integer < (66.0*i)/8.0 (floor operation)?


texts: Homemade TRRS Adapter for Microphone Only

texts:
I have a wireless monitor with a 3.5mm headphone jack in it, and I'd like to take the output from that monitor and stick it into my computer such that I can record it.  However, I have only a TRS-to-TRS cord to get sound out of the monitor and a TRRS port on my computer.

I poked around the internet and found the following to start me off.  My thought was to take my TRS cord, cut it, and take the tip wire and connect it to the mic input wire on the TRRS plug and solder together the ground wires on the sleeve of the TRS plug and the second ring of the TRRS plug.

Upon soldering the whole mess together, I checked for shorts, found none, plugged it in...and got...nada.  The computer recognized an external microphone, but would only register input when I plugged in the connector to the monitor I mentioned.  Prior to all this, I had done some continuity tests and I am 99% sure that the pinout I found was correct.  In other words, on the TRRS plug, I found a red wire attached to the tip, a green wire to ring 1 (the rightmost ring in the image), and wire with clear insulation on ring 2 (the "common" ring in the image), and a blue wire on the sleeve -- so I assumed that the pinout was correct.

However, I have no sound out, and I'm sure that all of my wires are otherwise sound (e.g., the connector from the monitor to the adapter is OK) and that the monitor does actually produce sound (e.g., if I plug a pair of headphones into it, I get good sound out).  I've tried tying the other two wires on the TRRS plug (tip and ring 1) to ground, and that didn't do anything either.

How might I make this work, if at all?


texts:
I need to plot this transfer function

When plotting the phase vs frequency graph, I am having problems to calculate the change in phase between 10 and 10^1.5. To my understanding, at frequency=10 the phase is -90°, then, there is a phase change and the slope should increase at a rate of 45°/dec but there is a change in frequency at 10^1.5. To calculate the degrees until the curve reaches 10^1.5 I applied simple trigonometry so that from frequency=10 to 10^1.5 the curve has moved up 10.80°. However, that answer is incorrect and the actual Bode plot shows that from frequency=10 to 10^1.5 the curve has moved up 22.5°. Could someone please explain to me how to properly calculate the phase change from frequency=10 to 10^1.5?


texts:
Why this simple program stops execution after reception of a single character over UART?
Normally the program blinks LED every half of second. When character is received the ISR should start. Nothing like this happens. The LED should blink once again but it doesn't. I am running it on atmega2560.
#define F_CPU 16000000UL

#include <stdint.h>

#include <avr/io.h>
#include <avr/interrupt.h>

#include <util/delay.h>

#define UART_BAUDRATE 9600
#define UART_BUFFER_MAX_SIZE 256

volatile uint8_t data = 'a';

ISR(USART0_RX_vect)
{
    // Receive character
    data = UDR0;

    // Blink LED
    PINB = 1 << PB7;
}

int main()
{
    // Configure LED
    DDRB = (1 << PB7);

    // Configure UART
    UBRR0 = F_CPU / 16 / UART_BAUDRATE - 1;
    UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);
    UCSR0B = (1 << RXCIE0) | (1 << RXEN0) | (1 << TXEN0);
    UCSR0A = 0;

    sei();

    while (1) {

        // Blink LED
        _delay_ms(500);
        PINB = 1 << PB7;

        // Transmit a character
        while (!(UCSR0A & (1 << UDRE0)));
        UDR0 = data;
    }
}


texts: Problem with Solid State Relay based on MOC3061

texts:
I was experimenting the circuit below. In the load, I placed the input of a full bridge rectifier. The issue is that the power triac is never activated. Sounds like the zero cross is not working.

Is that because a bridge rectifier is not a proper load for this circuit?

I simulated trying with an opto with no zero cross, and the simulation worked.


texts: Is unplugging computer power cable from PSU the same as electricity outage?

texts:
I am not sure if they are the same, but something puzzling just happened. My dell precision workstation 2007 has been fine ever since, with many, many power outages over the years. But there is a time a guy pulled the power cable off, and a few days later the PC no longer boot, with loud whooss fan sound at startup. After testing, everything was fine, only the motherboard died, with apparent fried capacitors. And if they are the same, would there be a difference if the PC is plugged to a power strip?
Can anyone please explain? Thank you.


texts:
I'm trying to analyze an RL Circuit .
I saw this equation for voltage drop over an inductor:
V = L * di/dt

But what about internal resistance of the inductor ?
I have a coil that have about 2 ohms resistance. how can I use this equation for it ? can I assume the internal resistance as a resistor before or after the coil ?


texts: How to increase current capacity of an ideal diode circuit?

texts:
We know ideal diodes doesn't exist but there are circuits that behave similar to ideal diodes.So my question is.
Can I add two ideal diode circuits in parallel each with 100 Amp current capacity to get a capacity of 200 Amps? These diodes are made from MOSFETs and BJTs. I am using LTC4371 manufactured by Linear Technology.


texts: Reason for Phase lead in RC high pass filter

texts:
I'm struggling to understand the phase response of a high pass RC filter.

At low frequencies, does the capacitor charge/discharge so quickly that there is a phase lead? But then we should have seen a similar behaviour in the low pass filter.

At high frequencies, in a low pass filter, the capacitor is unable to keep up with the frequency of VIN and charges/discharges at a slower rate resulting in a phase lag. Should we not see a similar behaviour in the high pass filter? On the contrary, VOUT actually gets more and more in phase in the high Pass counterpart which I don't understand.


texts: Combining 2x1 mux and 4x1 mux with AND gate

texts:
I've found an example from my teacher's notes and I've no clue how to solve it. Could someone help me?

Find the F output

Please go easy on me I'm still trying to learn this. My first attempt was completely wrong I've checked the MUX truth table again so here is my solution.
4x1 Mux should be:
A'B'C + A'B0 + AB'1 + AB1 = C+A
2x1 Mux should be:
AB + 0 = AB
then
(C+A)AB = AB
I'm using this website to simplify boolean algebras.


texts: How do I calculate the impedance needed to drop 120V AC?

texts:
I've been wanting to use the H11AA1 zero-crossing detector to detect the zero-crossing points of Mains Voltage - 120 V AC @ 50 Hz. The data sheet says that the max forward currents of the diodes are \$I_F\$ = 60 mA, max power dissipation is \$P_{diss}\$ = 100 mW, and typical voltage through \$ V_d = 1.2 V\$. I'd like to hook the H11AA1 up to the Mains line without a transformer and instead use passives to dissipate the remaining energy.

I've been modeling each line using this model:

The 'input voltage' that the impedance sees should be a half-wave rectified sine function, and the output should be a periodic square wave.

\$ v_i(t) = Asin(\omega t) * (u[t] - u[t- {\frac T2}]) \$

where \$ A = 120, \omega = 2\pi f = 100\pi\, T = \frac {1}{2\pi f}\$

Because of the diode truncates the voltage, the waveform should look like a periodic square wave (pretending there are instant rise/fall times)

\$ v_f(t) = \sum_{k=-\infty}^\infty 1.2(u[t] - u[t - kT]) \$

The current through the diode should look like:

\$ v_i(t) = 0.6sin(\omega t) * (u[t] - u[t- {\frac T2}]) \$

Using node voltages,

\$ \frac {V_i - V_f}{Z} = I_d\$

\$ Z = \frac {V_i - V_f}{I_d}\$

The issue I'm having is that I'm expecting the impedance to have a complex component and thus my expected output functions should have a phase shift - but I have no idea how to account for that, if so. Are there any other mistakes in my assumptions about the diode voltage and current? How should I go about solving for the impedance?


texts: protect op amp input from overvoltage from piezo sensor

texts:
I use a piezo to register the moment of a knock via a micro controller's analog in (1.8V Max)
So far I used the scheme in the figure without any diodes. This works so far, but depending on the knocks harshness, the op-amp cuts the sensor signal. This is why I want to protect the op-amps in+ from overvoltage.
I have two questions:

will two back back zener-diodes 5.1 V protect my op-amp sufficiently?
if yes: Does anyone know smt diodes which are quiet big, like 3 mm or so.


texts: Can a double conversion UPS energize grid-tied micro inverter solar array during power outage?

texts:
Hypothesis: Can a double conversion UPS energize a grid-tied micro inverter based solar array during power outage if the UPS input and output are both connected to main panel?
Assumptions below diagram
Questions:

Can the UPS provide reference voltage to the solar micro inverters to operate?
Can the the UPS get damaged due to excess AC current backfeeding into UPS's inverter?
Can we limit AC current backfeed into the UPS by dumping excess solar power to run a 5 ton HVAC?
Can the UPS keep a fixed 60Hz output (as the utility grid does) if the micro inverters adjust their output frequency?
Can the UPS batteries charge safely from micro inverters output?
What other safety and functional concerns should be addressed?

Assumptions:

Both the UPS and solar micro inverters are split phase 208V 60Hz
7.8KW solar array based on Enphase IQ6+ grid tie micro inverters.
3000VA APC double converion UPS model SURTD3000XLT with sine wave output
UPS output frequency tracks input frequency
input of UPS powered from breaker panel with 30A 2-pole breaker
output of UPS is plugged safely to breaker panel bus bar with 30A 2-pole breaker
grid is disconnected.


texts: Choosing the right DC-DC converter for a computer

texts:
I am looking at converting a computer to run off of a 12V battery, which means replacing its PSU with a DC-DC converter.
So, assuming that the computer is currently using 600 Watt PSU, then I assume that rating applies to the INPUT side of the PSU, which is a 120V. So, that would mean its max rated load is approximately 600W/120V = 5 Amps. Is that right?
If the DC-DC converter takes a 12V input, then it would seem the equivalent the rated load for the converter would be 5 Amps x 12 Volts = 60W. So, I would apparently need only a 60 Watt DC-DC converter.
However, when I look at typical catalog listings of DC-DC ATX converters, they seem to offer WAY more power than this. For example, if you look at PowerStream's DC-DC converters, the smallest one they have is listed as 320W and seems to have the same form factor as a typical small AC-DC ATX power supply. That does not really seem possible. So, is PowerStream listing their converter wattage as a 120V equivalent, not as a true 12V wattage? In other words is their "320W" PSU actually a 32 Watt PSU, and they are just calling it 320W to imply that it can replace a 320W 120V AC-based PSU?


texts: Is there a circuit that can create dispersion?

texts:
I'm wondering if there's a circuit that would create dispersion effects. Essentially, I'd like to create a circuit which can do the following:

Spread out a high frequency pulse. For example, put in a dirac delta function and get out a signal that looks like a gaussian distribution.
Leave lower frequency signals relatively unchanged (no dispersion).

This might also be called a frequency-dependent phase shifter. Or a circuit which has constant group delay up to a particular "cutoff" frequency after which the dispersion effects kick in and group delay becomes non-constant.

I have a feeling there's a circuit topology that is commonly used for this, and I'd just appreciate a point in the right direction. Thanks in advance for any help!!


texts: Can I wire a security camera into a switched lighting circuit?

texts:
I live in a building with a communal stairway. This has lights which are switched on each floor, controlled by a timer box which holds the lights on for 2 minutes after the push button is pressed.
I want to install a Raspberry pi zero running Motion Eye to act as a security camera.
The only power available is from the lighting circuit. I’ve opened a nearby connector box and have 3 wires: N, L and Switched L. What I observe is that I have 240VAC between L-N when the lights are off. This drops to 5VAC when the lights are on so is insufficient to power the PSU for the pi. The Switched L is of course 0VAC when off and 240VAC when on.
I’ve observed that there is a 100VAC voltage between L and SL when the lights are on, rising to 240VAC when they are off.
So, my question is, is it acceptable to connect a Raspberry pi PSU across L and SL?


texts: How can I implement regular expressions on an embedded device?

texts:
I have some (I thought) pretty portable code that uses <regex.h>. When I tried to port this over to compile for a PIC18 with xc8, the compiler could not find the header file for the library.

module/ciface/ciface.h:12:10: fatal error: 'regex.h' file not found
#include <regex.h>
         ^~~~~~~~~
1 error generated.

Is there any way to use regexs on an embedded device?


texts: Can I connect the primary of two coupled inductors (transformer) directly to mains voltage in parallel or do I need intermediary circuitary?

texts:
Examining a voltage regulator schematic, I believe I can connect the primary side of a step down transformer to mains voltage directly to step it down on the secondary, but PSpice doesn't let me simulate that same exact circuit(transformer with bridge rectifier) claiming I can't have a voltage source and inductor loop without a series resistor to break it. I don't know if this is just a PSpice limitation or if connecting the primary of a transformer directly to mains without resistors is a bad idea?

In PSpice, the two inductors are coupled using Place->PSpice Component->Passive->Coupling.

Background: The goal is to rebuild a voltage regulator using discrete components. I am trying to go from a 120 V 60 Hz to 12 Volts. Once I can step down and clip the negative wave correctly, I'll add the capacitive filter to smoothify or make the waveform more DC like.


texts: Difference between synchronous and conventional dc-dc boost converter?

texts: What is the difference between synchronous and conventional dc-dc boost converter? which one is best and why?


texts: Are there MOS VLSI Process Design Kits (SPICE models) for free SPICE simulators?

texts:
I want to do some proof-of-concept work in IC analogue IC design. I know that plenty of free circuit simulators exist (LTSpce, NgSpice etc.), however they are meant for PCB simulation and most perform poorly when attempting any serious work with transistor level designs. I know that this is mainly because they are supplied with elemental (MOS) device models that fail to capture the intricacies found in true silicon circuits.

My question is whether there exist some open source Process Design Kits (PDK), libraries of SPICE models, that one can use with any of the free simulators (or PSPICE, cause the OrCad-light version supplied by Cadence would suffice). I did some work in Cadence IC Design environments in uni and worked with both the AMS 0.35um pack, which is a real technology, and the GDPK 180 which they provide as a "general" PDK to play around. The later is exactly what I'd be looking for. For this project:

I don't need latest deep submicron tech (none of the SiO/FinFET stuff), it can honestly be quite old tech (like the aforementioned 180nm)
It doesn't have to be super-robust for any ultra-high frequency applications, I'm not intending on RF applications
It must be able to handle low power, subthreshold region operation (which is mainly why I'm asking the question)
It would be nice if it converged well with 100 nodes. From my experience PSPICE produced some very odd results (random jitter...) in circuits that contained multiple complex components (this might be the simulator's fault, the models' fault or my fault, hard to tell)
I would like to be able to specify gate width and length as a minimum for PMOS and NMOS devices, instead of having a discrete model for every possible W/L configuration (preferably).

I know PDK's are provided by foundries and are process specific. I know this is often industrial data that is protected as IP. All I hope for, is that for academic purposes there are libraries of models that aren't rubbish and are "good enough" if one wants to do serious simulation of circuits in CMOS.

Thank you for any responses!


texts:
It looks to me like the Friis formula is outdated. We can replace it with the E and H near field formulas, that converge into the same value in the far field.

I found it hard to use the Friis formula, whenever I switch from nearfield into farfield move, there is a sudden 20-30 dB error lag between the nearfield value and the farfield value. I don't think there is any kind of boundary that just does that, I think the values smoothen out and slowly converge.

So basically the Fraunhofer Boundary λ / (2 * π ), is a very stiff method to figure out the edge of the farfield, and it's prone to a lot of error. I think it's outdated.

Instead using the nearfield formulas introduced by Dr. Hans Gregory Schantz, seems like a more smooth way of looking at things:

It certainly works in the nearfield, it was verified by experiments. And there is no reason why it would not stretch into the far field. And basically the far field instead of becoming a stiff boundary like the Fraunhofer Boundary, it becomes like a smooth convergence point:

In this test I simulated a 2x 1 m long antennas 50 m distance from eachother, but it's like this for any other parameter.

As you can see if we go with the Fraunhofer Boundary using the Friis formula, the Farfield starts at 1.2 Mhz, however the nearfield formulas didn't converged yet, nor there is a concrete point of convergence. It looks like the Farfield Boundary at this case starts more like at 104.6 Mhz.

So it looks like the Fraunhofer Boundary is an obsolete concept, I think it's more dynamic than that, and there is no boundary, I think the impedance differences just smoothen out as frequency increases until it slowly reaches the free space impedance.

Edit 1: Sorry actually, the "d" in the formulas represents the distance between the transmitter and receiver, not the boundary sphere.

Edit 2: And the Fraunhofer Boundary doesn't start exactly at 1.2 Mhz, but somewhere between 806 Khz and 1.2 Mhz, I didn't calculated the exact frequency. However it doesn't matter, either way, there is still a high difference between the 2 fields's path loss. So I guess the far field starts when the impedance reaches that of the free space, which is more like at around 104.6 Mhz.


texts:
I have 97 LEDs soldered on to a stripboard in rows. Each row has varying lengths and I have no idea how to power the whole sign at once.

I tried powering 28 LEDs across two rows using a 9 volts (I was going to use a 9V battery but the bench power supply seemed more forgiving if I do something wrong) on a bench power supply connected to a buck converter. When I powered the circuit, the LM2596 chip on the buck converter went bang!

I was able to use this set up to power short strings on 4 LEDs but I would like to power the whole thing at once.

How would I power this board? Should I be using a buck converter, should I use something else and is there any way to power the all the LEDs with a battery.

I was trying to follow a tutorial on YouTube (The tutorial by Great Scott I tried following) but didn't know how to connect the LEDs

Below is a picture of the setup of the Buck converter

Below is a rough diagram of what i was going to make (Black thick line being LED string and Red thin being wire connecting strings)

I used this Buck converter module https://www.amazon.com/gp/product/B008BHB4L8/ref=as_li_qf_sp_asin_il_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=B008BHB4L8&linkCode=as2&tag=gre09a-20&linkId=4YLLYWHFS3V7EXZM


texts: Plotting the radiation pattern of a dipole antenna using MATLAB

texts:
I want to plot the radiation pattern of a half wavelength dipole antenna using MATLAB. But in dB scale, the plot has undesired peaks.
The code is shown below:
theta = linspace(0,2*pi,1e3);
wg =1;
k = 2*pi/wg;
l = wg/2;

U = ((cos(k*l/2*cos(theta))-cos(k*l/2))./(sin(theta))).^2;
Umax = max(U);
Un = U/Umax;

dbUn = 10*log(abs(Un));

polar(theta,dbUn)
grid minor

The plot is shown below:

Actually this is a pretty simple algorithm to implement but I do not know what I did wrong.


texts: Is TVS diode fast enough to protect MCU from MOSFET malfunction?

texts:
I am using standart N-channel MOSFET (Fairchild FDS6676) switch like in this picture:

Load is actually 10A resistive and 27V power source is fused with 15A non-recovery fuse. I am driving it directly from 3,3V logic - ARM MCU.

I know that MOSFET will be quite stressed because it is designed for 14,5A continuous current and 10A will be drained for sure. There might me some peaks to 12-13A for few miliseconds. As I calculated, there will be about 3-4W of power loss on this MOSFET.

I have heatsink mounted, but still concerned about reliability (always with thermally stressed parts). In case of MOSFET break/malfunction (overcurrent peak above 14,5A or over-temperature failure), MOSFETS often shorts all terminals, so I could get 27V to gate and directly to MCU port. In case that S-D burned together will blow my fuse, but in case only S-G not...

My question is - is TVS protection diode fast enought to protect MCU in such scenario? Or is there any better approach? I am considering Littelfuse AQ4020-01FTG-C.

Thank you


texts: Need Atmel 89C5131 microcontroler library for Altium designer v14.3.9

texts: I want to design a small electronic circuit using Altium designer v14.3.9, and I need the microcontroller Atmel's 89C5131 (the symbol, not for PCB), but couldn't find it in any of my libraries. Does any one know where can I get it?


texts:
Figure out the Vout wave form of the following circuit: ( assume the name of the 9u capacitor to be C2 and not C1)

Is there any way to intuitively plot the waveform by understanding the behavior of the circuit? Assume that initially all the capacitors are discharged.

My attempt at the problem:

C1d(Vin - Vout)/dt = C2 dVout/dt + Vout/R

For t<0,the output voltage remains zero.

For t>0, the input voltage remains constant resulting in an equation
-C1 dVout/dt = C2 dVout/dt + Vout/R

or (C1+C2) dVout/dt = - Vout/R

Solving this equation,

ln (Vout)  = - t/[R(C1+C2)] with initial condition of Vout being zero which poses a problem with the logarithmic function. Am I making any mistake in my analysis?


texts:
I am looking for supplier for RGB LEDs for an upcoming project RGB POV LED Globe. Normally I would go to my local electronics supply story, but this project requires lots (~1000) of LEDs and my local electronics store charges a premium for the LEDs, (@1.50 each)

I have done some searching online from a few retailers such as http://www.alibaba.com (~$0.19) or http://ledssuperbright.com ($0.35) or http://www.adafruit.com ($1.0) or http://www.sparkfun.com (~$0.6) or http://www.digikey.com (~$1.1)

I trust adafruit and sparkfun and have had good experiences from both of them in the past but I am worried that there is a such a huge range in price difference between each of these sites that I might be missing something critical.

Also I looked at other POV projects and some use diffuse others use clear LED. I'm not sure what type of LED I should use for this project. The MiniPov3 uses diffuse.

My questions are:

What make a good RGB LED?
What features should I be looking for in the data sheet for this type of project.
Should I use diffuse or clear LEDs on my RGB POV LED Globe project?


texts: Can I use a fuse rated 400V 32A on a 220V 32A circuit?


texts: Resistor on transimpedance amplifier input?

texts:
I am currently examining an expired patent file of a photoelectric sensor. The file includes the circuit, I am trying to understand it with my limited analog electronics knowledge:
Patent no: US6455839B1

The circuit is on Page 3 - Fig 2. I am stuck at the first part of the circuit (the photodiode amplifier). From other photodiode amplifier circuits I have researched, none of them had the resistor in the inverting input. It's not mentioned in the PDF (not even numbered). Only thing I could think that it may be forming a series RC circuit with the parasitic capacitance of the photodiode, so it may be dampening high frequency noise by increasing time constant. Or am I thinking too deep?


texts: designing Low-Pass Transmission Line Stub Filter

texts:
I'm trying to design a Low-Pass transmission line stub filter, and I have a few question regarding it.

I'm rather new to RF-circuit design, so please bear with me.

If my desired specs include the pass-frequencies and the block-frequencies, does that let me figure out a suitable \$N\$ somehow (does bigger \$N\$ make the slope more steep? How is this determined?)

How do I go about limiting the size of the reflection coefficient, or what counts as \$Z_S\$ in the circuit?

Any useful literature I should dive into in the topic of designing a transmission line stub filter and figuring out the details?

Thanks in advance.

Also, how should I consider the desired attenuation decibel amounts at pass/stop frequencies?


texts: Can someone help explain the operation of a safety relay system. I know that they can be connected to e-stops for emergency stops but I don't understand the relays and how they operate.


texts: I have connected a microprocessor to a bluetooth module using UART. During the sleep of my microprocessor, I measured 7.8uA flowing from uC's rxd to bluetooth module's txd. I measured 70k pull-up to 2.8V on uC's rxd side and open-circuit on bluetooth module's side. Will this configuration causes leakage current in UART line?


texts: Why DC is not used for long distance voltage transmission? (Tesla vs Edison 2015)

texts:
It seems this question has been marked duplicate but I believe the answers given here is much more in detail.
Why we are still using AC voltage for long distance voltage transmission. As we know with our current technology we could step up and and step down DC voltage thus reducing the Amps and losses. Dc current would have no harmonics or frequency issues. We may convert DC back to AC at receiving end.

Reasons for my arguments are Advantages of HVDC over HVAC transmission


texts:
I'm interested in generating a chart / diagram of power usage for a system, as well as some sort of tree digram of voltage rails.

For example, you might have a PMIC connected to VBAT, the output of which is connected to a 3V3 LDO, 5V SMPS, etc etc.

Keeping track of all the rails, and where they connect to would be very handy.

Additionally, being able to assign powers to each rail would aid in visualizing where the power is going.

Any thoughts on how to create something like this easily?

Ideally, I'd like a tool that could generate a chart automatically -- I don't want to create a tree diagram manually with 50 boxes if I can do it programatically.

Thanks!


texts: diodes at the output of window comparator

texts: Can anyone explain to me the function of those two diodes?


texts:
I'm currently designing a mixed-signal PCB for a client and I've been reading a lot about signal integrity and most of the books recommend a 4 layer board (or more) because of the noise resistance from having a solid ground plane and reduced routing.

The board in question has two 16-bit ADCs and two 16-bit DACs with OP amps in the analog section, a microcontroller with some level shifters and mosfets in the digital section, and two DC/DC converters and an LDO regulator in the power section.  Space is not much of a constraint, but having high resolution and low noise in the analog section is important.  There's an I2C and an SPI bus running between the digital section and the edge of the analog section, operating at less than 10 MHz.

Routing wise I can totally get this board done in 2 layers.  Will I really notice a huge difference in signal integrity with a 4 layer board and dedicated ground plane?  Is it worth the extra cost?  I'm leaning towards 4 but I'd like to hear your opinions.

Thanks in advance guys.


texts: I want to sense the current through a solenoid when it is ON. Ideally I would want this for testing purposes and overcurrent protection. As I have a free ADC pin in my microcontroller, I came up with the approach below. I don't expect a current greater than 500 mA, and the coil will be given a single pulse, no PWM. Is this a good idea? I'm looking for a simple solution, i.e., not extra ICs or amplifiers.


texts: What is the connector used on the Samsung AMS495QA01 Screen?

texts: Its on some screen(s?) made by samsung however i do not know where i can find the connector itself. which is what im after.


texts: What is the physical explanation of electric breakdown?

texts: I would like to know what is the physics behind the electric breakdown in gases so they become electrically conductive. So far, all the information that I have found describes the phenomenon in a macroscopic scale. I am interested in the microscopic explanation of the phenomenon, e.g. What happens to the molecules.


texts: A question on difference between an computationally created sinusoid signal and the recorded signal (when played out through a speaker)?

texts:
I have created the following signal(in Matlab), a 5000 Hz sinusoid multiplied with a bump (just to limit it in time) so that it forms a short beep. Now if i observe the spectrum of this computationally created signal (in matlab) there is an impulse like structure at 5000Hz and nothing else.

Now i perform this experiment. I play this signal in matlab through a sound card into a speaker and record the sound played on the speaker through a microphone. The surprising thing is that if i observe the spectrum of this recorded signal, i find a impulse like structure at 5000Hz as expected but there is a another impulse like structure of much lower amplitude at 10000Hz and an even much smaller one at 15000Hz. I wonder how it can be explained.

When I repeated this experiment with 2000Hz I found same observation at 4000Hz and 8000Hz.


texts: 555 Astable Timer produces incorrect period/frequency

texts:
I am building a 555 astable timer circuit for a course which must match the BPM of a song. The song has a BPM of 104, which requires a timer frequency of roughly 1.733 Hz.

The circuit looks as follows:

(the green wires go off to the left onto another breadboard, which looks as follows:)

It is hard to see, but the 0.01µF capacitor goes to pin 5 of the 555 timer.

The values used in the circuit as follows (measured using a LCR meter):
R1 = 5.5kΩ
R2 = 38.5kΩ
Ctotal = 10.02 µF

The problem is that the circuit produces a frequency of roughly 1.5, far off the from the desired/predicted frequency of 1.733. 5V Power is being supplied to both rails, the chip has been replaced, but to no avail. Here is a picture of the simulated circuit in LTspice:

Is this due to some limits of the 555 timer at frequencies nearing 1Hz or due to some miswiring on my part?

simulate this circuit – Schematic created using CircuitLab


texts: How can I build a circuit to drive a 12V solenoid from a 3V source, so up 3V to 12V by storing in capacitors, charge and discharge cycles?

texts:
No electronics background, noob, but I want to drive a small solenoid to cycle it everytime I push a button.

I wanted to use 2 AA batteries in series as they fit the size of my project well. I will use the solenoid just to hit a fixed part and generate a small noise, like a knocker.


texts: How do I connect a 62pin SNES connector to a breadboard?

texts:
I have a 62pin SNES connector.  It is too narrow to fit on the breadboard like I would an IC.  I thought about filing down two breadboards so there is a thinner "trench."
Is there any adapter I can use?  I know it is a proprietary part, but I thought it might be possible to fit somehow before I started filing down breadboards.
More generally, I think this could apply to anything.  What do you do with parts that won't fit the breadboard, non-standard?


texts: Can a 555 be used to control the charging and discharging of a capacitor to provide bursts of current?

texts: I have a solar cell that charges a capacitor. I want to switch on a motor when a voltage level is reached and then switch off again at a lower voltage or when the capacitor is discharged. I modelled this in a simulator using a 555 by connecting diodes to ground on the threshold and trigger and then 10K resistors to the supply rail. The 555 was powered from the capacitor. I tried this with an actual 555 with an LED on the output. The real system always reach a stable state. Can what I am trying to do be done? How do I change the circuit to make it work?


texts: Isn't calling USB 3.0 nodes "hubs" inaccurate?

texts:
Host transmitted protocol packets are routed through intervening hubs directly to a
  peripheral device. They do not traverse bus paths that are not part of the direct path between the
  host and the target peripheral device. -- USB 3.0, section 3.2.3

USB 2.0 is broadcast technology, meaning that all devices on the bus receive all packets. USB 3.0 is unicast technology, meaning that packets are routed only to the target device.

Technically, shouldn't we be saying "USB 2 hub" and "USB 3 router"?


texts: Castellated/Edge-plated PCBs: Comments on Mechanical/Electrical contact reliability

texts:
(This is a follow-up to this related question).

I'm interested in some feedback from people's design results/experiences with Castellated PCBs as a method of attaching one PCB to another. By Castellations, I am referring of course to Half-vias or Edge plating, as follows (both images are from Stack):

It seems to be an elegant solution, and appears to be a fairly popular form factor, especially among RF modules.

But I am concerned with (and would like comments regarding):

how robust the mechanical contact is
how reliable the electrical contact will be
what design methods/factors might influence the quality of the connections

E.g., one layout approach, as described by @Rocketmagnet in the earlier related question, is to place vias on the dimension outline, thus half-drilled holes act as the solderable castellations. Is this a standard/accepted method, or should a designer actually contact the PCB manufacturer and custom-design the board specifically requesting castellation addition?

As seen in the image below, results with the half-size plated through-hole approach (from this person's blog) aren't too impressive (the page's author holds the poor milling responsible).


texts: Relation between current voltage .Acc. to ohm's law and P=IV

texts:
Here in image increase in current increase the voltage and vice versa

Here in image when voltage increase current low and vice versa 2 pages of same books what is right and how to understand ?


texts: Response of a Differential Pair to Differential Mode Signals

texts:
I do not understand this kind of analysis of a Mosfet Differential Pair:

This analysis wants to prove that, when a purely differential mode signal is applied (so opposite signals are applied between the transistor gates and GND), it is possible to analyze only half of the circuit, with GND at the point E, as shown in the following picture.

The statement I read is that since V1 = - V2, the potential at point E should be equal and opposite to itself (first question: why? Is it due to the symmetric voltage drops between the gate and the source of the 2 MOSFETs?) and this is possible only if it is constant in time, and so it is put equal to GND (first question: what does it mean? A constant voltage is not necessarily equal to GND).

Can you explain me this procedure step by step?

Third question: with differential signals, can be both Mosfet ON?


texts: When an HC-05 Bluetooth module receives data via wireless does it write it to receive(rx) pin or transmit(tx) pin?

texts:
I'm using an HC-05 and I have it successfully wired up to my ATMega328P so that the HC-05 Tx is tied to the ATMega328 Rx and HC-05 Rx is tied to the ATMega328P Tx.

So I'm assuming that the data received on the wireless signal is then written to the HC-05 Tx pin. That sends it to the Rx pin of the ATMega328P (since it is wired as I explained above).

Is that a valid description?

Just trying to untangle this in my mind so I understand that received data (via wireless) appears on the Transmit (Tx) pin.  I could almost see that wirelessly received data could be found on Rx pin since it is really data that is received but I think the two are separate.

Guess About HC-05 Chip and Wireless Data

I'm guessing that a chip on the HC-05 writes the received data to the serial port (Tx), right? And then data that i want to be sent over the bluetooth from the HC-05 would be read on the Rx pin which is then converted to wireless and sent by the HC-05?

Can someone clear it up for me?


texts: How to build Li-ion over-discharge protection board

texts:
I have an Arduino board with a pump attached to it, and for powering both, I'm using a 18650 battery cell with a DC-DC Boost Converter. I plan to leave it working even when I'm not home, and I know that if the battery over discharges, there will be trouble, so I would like to design an over-discharge protection board.

I can see from this video that it is not a big deal to build one, however, I don't have a battery alarm buzzer. Is there any way to build such a protection board without that part?

Or is there any simpler way to build such a circuit with the components that I have: a relay (JQC-3F(T73)), some diodes (N4007 type), capacitors(22, 47 and 100uF) a potentiometer, a bunch of resistances (from 1mΩ to 51 kΩ) and transistors (PNP-8550, NPN-8050 and IRF520).

I'm attaching the scheme given by the person that made the video:


texts:
I need to process image data from 10 image sensors simultaneously (namely from OnSemi MT9V022s or similar). All 10 sensors will be externally triggered by a common signal. Ideal solution would be to do the processing on some high-level CPU like ARMv7/8 or x86 but I dont know how to connect all the cameras to the CPU. I would like to avoid using USB for the connection since I dont need the USB stack for anything (maybe except transfer speed).

The image sensors have either serial or parallel output. Since there may not be 10 similar data input types on a given CPU, is the only way to multiplex the image data to fewer (or single) streams? If so, how could such multiplexing be done? Are there some ICs that could be used for that or do I have to design a custom FPGA? As I see it, may I need to develop a custom "multiplexer" device that would input all 10 sensors and join them to a common output?

Given I would like at least 10 x 320x240 8-bit grayscale at 10-30 FPS what are the IO options for the common output (SPI, USB etc.)? Can I use a CSI interface for the common output and write a driver that would do the de-multiplexing? Or can I just multiplex the sensors for transfer and then de-multiplex them in CPU and use a Linux image sensor driver? A target CPU would be ideally a strong multicore ARM with OpenCL support - maybe something like nVidia Tegra K1 or X1.


texts: Lots of industrial electronic hardware mounts to DIN rail. I would think there must be a weight limit to such mounting. But I haven't been able to identify one. Is there a defined weight limit, either by written standard or accepted practice?


texts: Energy-efficient Power Supply (PSU) circuit for STM32WLE Microcontroller with 1.8-3.6V for 150mA peak current

texts:
I am thinking how to best (best=lowest energy consumption and standby current) power a STM32WLE:
https://www.st.com/en/microcontrollers-microprocessors/stm32wlex.html
The power management of the IC itself is described on p23 onwards, the MCU accepts from 1.8-3.6V.
My constraints are:

I want to power an external hall effect sensor with a stable voltage (let's say 3.3V).
As battery, I would like to use a LiPo but it is not a must.
Standby current should be less than 50µA
Max current pulled will be 200mA

I have been thinking about following implementations:

Texas is offering a few nice buck or buck/boost converters such as these ones here: https://www.powerelectronicsnews.com/diy-how-build-a-smart-power-supply-for-your-microcontroller-projects/ . If I use a buck/bost converter, I am not so limited to the battery chemistry. What do you think?
Here someone has tried using just a couple of forward biased silicon diodes to reduce a 5V input signal but it just seems wrong when going for lowest power consumption: https://www.allaboutcircuits.com/technical-articles/a-low-cost-method-of-powering-a-microcontroller/
Previous thread here from stackexchange:
Most efficient way to convert from 3.5-4.2V (singe cell LiPo) to stable 3.3V for currents up to 500 mA?
Buck converters are suggested there
The LTC3440 has a  quiescent current of around 25µA, which sounds fair: https://www.analog.com/en/technical-articles/it-just-got-easier-to-convert-lithium-ion-battery-voltage-to-33v.html#
I guess I can just browse for low-quiescent current buck/boost converters.

EDIT: My question is: Can you review my ideas for implementing an energy-efficient power supply for a microcontroller?


texts:
I need help with an ASEM HMI130TF with a SCADA program on it works on Windows 7. it is connected with LAN network TCP/ip with a PLC and another HMI, and it has a static ip.

the problem is it sometimes loses connectivity to this LAN, thus it can't send or get commands from PLC, I don't know why. I tested the cable and every other element and they are all ok.

I tried to connect it to the internet directly and it worked perfectly. but it doesn't want to connect to the LAN.
can you help me?s


texts: RFID - Detecting items in box regardless of tag orientation

texts:
I'm thinking about something, and am wondering if RFID can accomplish this. Is it possible to place an RFID antenna on the bottom of a box, put an arbitrary amount of items with different shapes with RFID stickers on top, and have the antenna detect their IDs?

I saw some omni-directional antennas however they seem quite linear too. Would this work if the bottom space of the containing box is 50 cm² (20 inches²), and some of the items are placed in the same horizontal space as the reader?


texts: what is a proper circuit for RF switch matrix in microwave frequencies?

texts:
I am going to make an RF circuit that can switch between multiple RF ports in microwave band like an MxN  simplex switching matrix. Generally I don't know if this would be possible in analog domain as digital domain with high switching rate and low distortion?

To be clear, what is the typical switching rate that is achievable in RF/Analog domain when we wish to implement this by basic elements in discrete form?
secondly, is there any good electrical circuit scheme form band 2Gig or more that can work in discrete circuit ?

assume we have 10 receiving antenna to be switched to 12 band pass filters at 2Ghz and 250Mhz bandwidth.
the required insertion loss is less than 6 db and the leakage from irrelevant ports should be less than -40db.


texts: RGB LED strip, powered by an ATX PSU and controlled by PWM, makes my speakers buzz with Arduino connected by USB

texts:
I've not much idea about electronics, but I managed to do some little projects in the past. Now I'd like to place some RGB LEDs in my desktop PC windowed case. For that, I bought a 5050 SMD strip with 300 RGB LED's (5 meters). Now I want to control it with an Arduino Uno.

I followed these two tutorials:

RGB LED Strip Controlled by an Arduino
*notice there is a misplaced resistor on red color

Adafruit Tutorial - RGB LED Strips

I'm using IRFZ44N MOSFETs, as shown in the first tutorial. The LED strip is being powered with 12V from an ATX PSU (not the one in my computer). I want to power (and send serial data to) the Arduino board by using an USB cable connected to the computer.

Everything is working, but my problem is that I get noise into my speakers (monitor built-in) when:

PSU is powering the LEDs.
PWM values are varying (color fading).
The USB cable is connecting the Arduino and the computer.
Audio cable is connecting the monitor and the computer (or my project's GND).
Speakers (monitor) are on.

I saw very few similar cases on internet. They speak about capacitors and inductors, but I can't get what and where should I be adding to my project.

Update: It tried by powering my LEDs with a wall AC adapter at 9V and 12V and the noise disappeared. But I still need to know how to remove the noise when using a computer ATX PSU like this:


texts: Viewing the Arduino Serial Monitor while ATMega328P is powered by batteries

texts:
Is it possible to view the serial monitor of the ATMega328P (with the Arduino Nano Bootloader) while the arduino is powered by an external power supply?

I'm trying to troubleshoot my program, and it will be a lot easier if I'm able to view what is going on with the code while the batteries are plugged in. My circuit is powered by two 3.7V Lithium Ion batteries in series. Right now, I'm trying to debug the charging circuit part of my program. It will be easier to do so if I can use the serial monitor to view the data registers on the I2C bus while the Lithium Ion batteries are charging.

For this project, I'm not using the arduino board, but the actual ATMega328P microcontroller. To upload the program, I have been using the FT232RL USB to Serial converter module. I did a test to see if it was possible to view the serial monitor with my Arduino Pro Mini, and it was successful. I powered the Pro Mini via the batteries, and connected the TX and RX serial pins on the FT232 and to the Arduino Board. Now when I try the same thing with the standalone ATMega, the Serial Monitor isn't responding. I am still able to upload a sketch and view the Serial Monitor normally if I remove the batteries, so what am I doing wrong? I'm asking on here so I don't accidentally damage my microcontroller in the process.

Here is the ATMega328P portion of my schematic:


texts: Platinum RTD temperature sensor choices between 1000ohm and 100ohm

texts:
I heard the Platinum RTD temperature sensor are very accurate and I want to use it for my temperature measurement project (-40 degree to 80 degree range). I don't want to use other type sensors.

Platinum RTD sensor have 2 categories: 1000 ohm and 100 ohm.

Which one should I use?

What are the differences? Is it because 1000ohm will give you higher voltage than 100ohm so you can easily do ADC (0-5V, 10 bit, Arduino)?


texts: A basic question on Ohm’s law and the definition of voltage

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1 Volt is defined as: when 1 Joule of work is expended in moving 1 Coulomb charge between two points.

On the other hand the Ohm’s law states:

V = I × R

I draw a theoretical circuit below where an ideal 1V voltage source is coupled to a 1 Ohm resistor.

From these two definitions is it possible to estimate the total charge moved between A and B when the supply is 1V and the resistance is 1 Ohm?

Seems like time is confusing me because Joule is energy unit. Watt joule eV voltage resistance all mixed up.


texts:
Question:

Could conformal coating affect the properties of an inductor by adhering to its windings?

Context and problem:

I have a simple boost regulator circuit based around the TPS61230 IC. It has a handful of SMD resistors and capacitors and one largish SMD inductor (http://www.mouser.com/ProductDetail/Bourns/SRU1028-1R0Y/?qs=%2fha2pyFaduga8qwkov01I2ofW5jqNjYb0PGY4sjOrrG99%2faGtQIpWg%3d%3d).

The circuit worked fine when I built it up, but I decided to conformal coat it to protect it before installing in the final product. Since I conformal coated it I'm not longer getting my 5 V on the output and instead when powered there's a -0.5 output voltage which then goes to zero. I can't see how the conformal coating could affect the rest of the circuit, but the inductor has openings on the top which my conformal coating spray probably got into.

The question I have is how might the spray have affected the properties of the inductor to cause this behavior? Is this the likely problem? I don't have any extra inductors so am trying to hone in on the issue before ordering more.

Picture of circuit board, and yes, I covered my connector pins during conformal coating.


texts:
I'm completely new at electronics, and so I just got my first multimeter - a pretty cheap one, a Draper Digital multimeter. Got my first problem with it as soon as I opened it to place the battery.

The only mention of the battery in the manual was to "insert the appropriate battery taking note of the polarity". There is no immediately obvious marking around the battery slot that would tell me which way to plug the battery. No plus or minus signs can be seen.

So I'm thinking either:

There is a way to tell how to place the battery that I'm somehow missing.
The placement of the battery doesn't matter for some reason beyond my understanding, and I'm really supposed to just "take note" of it. (In which case, why does this matter?)
This is an issue with this specific kind of multimeter, and I should be contacting the manufacturer.

What are your thoughts on this?


texts: Enable connected to unpowered regulator on another board

texts:
I have an ARM board which uses a VIO of 1.8V and requires that no i/o line be driven before it is fully powered up. It signals this readiness by asserting its "SYSEN" line.

My design has SYSEN from this board connected to the enable line of a 1.8V linear regulator on a separate docking board. The 1.8V line powers (one side of) all the level shifters - thus I'm protected from damaging the ARM as 1.8V will not exist until SYSEN is asserted.

But there is a corner case which is that "what if the fuse on the docking board blows". Then the 5V line to the regulator is unpowered when SYSEN goes high (1.8V). I initially chose the Micrel MIC5247-1.8:

but looking at the datasheet:

the enable clearly cannot go above Vin. If Vin is zero, then EN must be zero. I would suppose there are input protection diodes in place to gnd and Vin or some such.

If I choose to use another device, say the Microchip MCP1804-1.8, then it's still not always absolutely clear what is allowed. Looking at the MCP1804 datasheet it shows protection diodes to gnd, but not Vcc. Promising. The max ratings imply that SHDN can exceed Vin but the params sort of say the opposite but in an unhelpful way:

If I give up and just gate the enable line (eg: 74AHC1G125) at least that datasheet specifically gives static characteristics which indicate that Vi can exceed Vcc. Eg: If Vcc = 2.0V then the min for a logic high is 1.5V, there's no max given. Also leakage currents are given when Vcc=0V and Vi=5V.

(Edit: Scratch that - if Vcc is 5V and Vi is 1.8V then it doesn't do me any good to use a bus buffer of any sort. I'd have to gate it with discrete components - eg: SYSEN to a fet pulled up to 5V and then invert that logic. Which is too many components for a simple issue!).

Should I try to read between the lines on datasheets like this or is it always the case that I just have to buy the devices and test them? I'm inclined to say the MCP1804 will likely be fine but I'm not sure.


texts:
i want to get the clock frequency divide by 5, can i do it with integer type or i need something else to run the decimal number?

library ieee;
use ieee.std_logic_1164.all;
use IEEE.NUMERIC_STD.ALL;

entity divide_clk is
port( clk: in std_logic;
 clk_out: out std_logic);
end divide_clk;

 architecture behave of divide_clk is
signal count: integer range 0 to 24999999:= 0;
signal temp : std_logic := '0';
begin
process(clk)
begin
if (clk'event and clk='1') then
 if (count = 2.5) then
 temp <= not(temp);
 count <= 0;
 else
 count <= count + 1;
 end if;
end if;
end process;
clk_out <= temp;
end behave;


texts:
I need a backup power source for my aquarium tank filtration system. A pure sine wave UPS seems to be an expensive overkill, so I'm looking for alternatives.

The filtration system pump runs of 230V, 50Hz AC motor with magnetic coupling (I assume synchronous?) and consumes somewhat less than 10W of power.

My idea was to buy a cheap modified sine wave power inverter from eBay, rated for 100W, and use a spare 12V sealed lead-acid motorcycle battery I already have.

The inverter came yesterday, I've tried it with the battery and my pump. It seems to work, at least in sense the motor pumps water properly, but it does not seem to like the modified sine wave much - it's very noisy and produces more heat than normal. I stopped it after a minute worrying about damaging my equipment. I suspect this problem is caused by sharp edges and high harmonics produced by the modified sine wave inverter.

Wouldn't it be possible to simply smooth the output of a modified sine wave inverter somewhat to make it more acceptable for the motor? How about using a some capacitor on the 230V output?

I've done some research and found some people arguing it was inefficient but possible, in principle, by using a capacitor on the output, parallel to the load. I don't need it to be very efficient, it's just 10W, nor I need the smoothing to be perfect, but I definitely need to make the output more sine-like. Is this idea viable? If so, how I compute the optimal capacity of the filtration capacitor?