texts: Is it worth getting a function generator?

texts: Is a function generator necessary for every day lab use, or is it special purpose equipment? That is, does it have similar utility to an oscilloscope, or multimeter - would you use it regularly enough to justify it's cost?


texts:
I want to connect two VLF antenna (given below) to a RaspberryPi using it's GPIO ports with a MPC3008 ADC.

Desired frequency range is between 3kHz to 30kHz, and MPC3008 supports 200,000 samples/sec max. sampling rate. I can sample the the data coming from the antenna without aliasing.

But, does the RaspberryPi support that sampling rates?

and should I use a gain amplifier?

  Miniature Very Low Frequency Antenna

  ANTM1. This miniature 6 inch long antenna can be tuned from 3 KHz to
  39 KHz with an external capacitor value of 0.1 uF to 370 pF. @ 370 pF
  tunes to @ 39 KHz. 0.1 uF tunes to @ 3 KHz.

  Weather proof sealed. 6 inch wire leads. Great for series resonant use
  in small transmitters or receivers. 1 watt max.


texts: What type of connector is this (see picture)?

texts: I could not find out what type of connector this is. It has a width of approximately 10mm, 0.5mm pitch, and 30 pins. I assume it is some kind of diagnostic port. It is part of a mobile device with OMAP4470 processor. Any help would be appreciated. Many thanks!


texts:
I have a quick questions: can I safely power a LED with 3.3v without a resistor? I have some LEDs that I typically power with 5v and a 220Ω resistor, but I can only supply 3.3v at the moment.

Additionally I have push-buttons that I typically pull-down with 10kΩ resistors when using 5v. What resistor should I use in this case? Is there a general rule on what resistor should be used given the voltage?

Thank you in advanced for your help!


texts:
As you know the li-ion batteries have flat voltage curve and it is not possible to detect battery state of charge (SOC) from voltage accurately. We use fual-guage which measures the accumulated charge.
Since, this is integration method we correct the battery state of charge when the battery gets fully charged (battery voltage 4.2V). It is important to detect the battery capacity (mAH) to accurately measure battery SOC (battery %).  But the battery capacity varies over time and from one battery to other. Battery needs to be calibrated over time and first time we connect. What is the standard technique followed by mobile/laptop manufacturer for the battery calibration?


texts: Realizing logic gates with transistors: AND and OR gate in parallel, trying to understand different behaviours

texts:
I am trying to understand and finally realize a logic gate by using transitors. In order to build a "simple" one-bit adder, my first step was to design a circuit that puts an AND-gate and an OR-gate in parallel (as can be seen below in circuit 1).
The desired behaviour is as follows:

Remark: This is NOT supposed to be the final 1-bit-adder. I am trying to figure out as much as possible on my own, so I kindly ask not to spoiler on how to proceed with the entire 1-bit-adder.

1.) Upper switch closed, lower switch opened: Left LED off, right LED on.

2.) Upper switch open, lower switch closed: Left LED off, right LED on.

3.) Upper switch closed, lower switch closed: Both LEDs on.

With the circuit shown above this behaviour could be achieved, which is good. However, this is the result that I came up with after several iterations of trial and error. One of my first attempts can be seen below in circuit 2. This one is not working and I am trying to understand why this is. Please check out my "first-attempt-circuit" first:

The major difference between the two designs is that the two 20k resitors (per switch) that where set up in parallel in circuit 1 were substituted by just ONE 10k resistor (per switch) just in front of the switches. So the total resistance in the 5V-control-circuit should be the same in both cases, right? However, the behavious is completely different and I do not understand why this is. The behaviour shown by circuit 2 is as follows:

1.) Upper switch closed, lower switch opened: Left LED off, right LED on. (OK!)

2.) Upper switch open, lower switch closed: Both LEDs off. (Bad!!!)

3.) Upper switch closed, lower switch closed: Left LED on (damped, I = 3.25 mA), right LED on (bright, I = 23.48 mA). (Bad!!!)

I assume that in case 2 the lower transistor of the AND-gate opens, allowing base-current to flow back to GND. Further I assume that this leads to a drop in voltage, not leaving enough power to open the lower transistor of the OR-gate. However, I do not understand why this is different in circuit 1, where the voltage between the AND-gate's base and the OR-gate's base should be the same too, just with a higher resistance, right? I would love to see someone bringing some clarification to this one ;-)


texts: Predictions based on resistance measurements not matching reality?

texts:
I'm using my multimeter to measure the resistance of my tongue, and leaving it on there for a full minute it seems to average out at around 1.5 Million Ohms.

However, when I put a 9 volt battery on my tongue, I can definitely feel an unpleasant shock.

According to Ohm's Law, the current going through my tongue should only be (9 / 1.5M) = 0.000006 Amps (0.006 mA). However, this chart indicates that anything under 1 mA should be imperceptible.

Why can I feel the battery through my tongue?


texts: Modelling MEMS accelerometer's measurement noise using datasheet (ADXL330)

texts:
I'd like to model an Analog Devices ADXL330 MEMS accelerometer using data provided in its datasheet to estimate measurement noise. I'm using a simple mathematical model defined in the paper "Non-linear complementary filters on the special orthogonal group" by Robert Mahony et al.:

\$ \bar{a} = a + \mu_a + b_a \$,

where \$ \bar{a} \$ is accelerometers output given in [g], \$ a \$ denotes the true value, \$ \mu_a \$ denotes additive measurement noise and \$ b_a \$ denotes a constant (or slowly time-varying) bias.

The question is what sensible values should I take for \$\mu_a\$ and \$b_a\$? How do I derive them?

I'd like those values to be in units of g. There are some noise characteristics given in the aforementioned datasheet (page 3), but I'm not sure I can interpret those correctly. Any help appreciated.


texts: The flash of STM32F10x cannot run at 24MHZ without latency stably?

texts:
A board with STM32F103C8T6 sometimes runs into hard fault handler.

When I heat up the board to 65C or higher, a hard fault will be caused randomly, which leads me to check if the latency of the flash is not enough.

Then I set the flash latency to 1 clock, the problem is solved,the chip runs stably even when I heat it up to 100C.

But it makes no sense because CPU runs at 24MHZ(HCLK is 24MHZ), which means no flash latency is needed as the datasheet says.

Here are my detailed clock configuration:
Clock source is 16MHZ given by external crystal, and PLL is 3x(I need to use USB ,so a clock of 48MHZ at SYSCLK is needed), then the AHB prescaler is configured to 2, so the clock of the CPU is 24MHZ.

I looked up the datasheet and it doesn't say clearly where the flash is clocked, but it says "Flash memory instructions and data access are performed through the AHB bus", does it mean the clock of the flash equals to AHB (24MHZ in my application)? But it doesn't work stably, where am I wrong?

Thanks


texts:
Have what I'm sure will seem like a strange question but it is important so if someone could help I would appreciate it. Have a son who is developmentally disabled and he has a thing for water hoses in pools or hot tubs. A picture of him is attached.

So the hose is fine sometimes but in winter it doesn't work and it also causes  problems in other seasons I won't go into. My question is whether it would be safe to use a battery powered submersible pump to operate a hose and pump the water in the tub or pool?

My reasoning is that it recycles the water rather than wastes it and it will make for more comfortable experience as well. Obviously I would not do it if it is dangerous so I know I won't use an electrical pump as there is a one in a million chance something could go wrong.

So electric is out but I can't say I've ever heard of someone being electrocuted by a battery. Would a battery powered submersible pump be safe?


texts:
I'm building a FM receiver based on a SA615.
But when I test the VFO (variable frequency oscillator) with a spectrum analyzer and a sniffer probe I don't see any frequency showing up. So the oscillator isn't starting up.

The VFO circuit I made is composed of salvaged radio parts.
Like a fm radio tuning capacitor, and the coil of the radio's loc osc.
The circuit I use is this one:
Where VAR-CAP is connected to the FM tuning capacitor.
And OSC_OUT to pin 3 of the sa615 (emmiter) and OSC_IN to pin 4 (base).
My circuit is based on following examples:  and this

I hope someone can give me some tips or see whats wrong with it.

Thanks in advance!


texts: Problem with calculating propagation delay

texts: I need to calculate the propagation delay for this circuit.I am confused because do I have to take every necessary combination of inputs and outputs or do I have to take the longest route from input to output by deciding to take the route which has the max number of logic gates ? thx for any advice


texts:
When looking at a transformer datasheet, I want to know if the Secondary AC output voltage which is specified is the \$V_{pk}\$ or the \$V_{rms}\$.

From this Triad FS12-090 datasheet, does 12.6V mean \$V_{rms}{ }\$ or \$V_{pk}{ }\$ ?


texts:
Premise
The antenna gain of a transmitting antenna relates its radiation intensity U(θ,ϕ) to its input power as shown in the following formula:
$$G(θ,ϕ)=\frac{U(θ,ϕ)}{P_{IN}/4\pi}$$
Where the radiation intensity in far field zone is related to the frequency domain poynting vector $$\vec{S}(r,θ,ϕ) = \frac{1}{2}\cdot \vec{E} \times \vec{H}^*$$
by the equation:
$$U(θ,ϕ)=|\vec{S}(r,θ,ϕ)|\cdot r^2$$
The radiation intensity does not depend on the distance because of the inverse square behaviour of the Poynting vector, so it is only a representation of how the antenna distributes the power in the different directions (θ,ϕ).
Observation
The Poynting vector is not only defined in the frequency domain, but also in the time domain. Its definition is this:
$$\vec{S(t)}(r,θ,ϕ) = \frac{1}{2}\cdot \vec{E(t)} \times \vec{H(t)}^*$$
It represents the instantaneous power flowing out from the antenna.
Instead, the frequency domain Poynting vector is a vector whose real part is the average power transmitted by the antenna. In the case of harmonic (sine wave) fields, there is the factor 1/2 that comes from the averaging operator. This explains the reason why the frequency domain Poynting vector is defined with such a factor.
Question
The antenna gain is defined from radiation intensity which is defined from the frequency domain Poynting vector. So, it seems to me that the antenna gain means how an antenna "amplifies" (or "attenuates", depending on if it's + dBi or -dB) the average input power along a direction (θ,ϕ).
But physically (not from the definition convention), is this concept of antenna gain a function of time?
The time dependence of the transmitting power (due to the time dependence of the time domain Poynting vector) represents the electromagnetic power flowing out from the antenna, like shown in the following picture (see here to watch the animation):

So, is physically the antenna gain animated? Is it a time varying quantity?
The antenna gain is by definition time - independent (since it involves a frequency domain quantity,) but is the antenna ratio between instant transmitted power and instantaneous input power time dependent?


texts:
I am beginner to ATmega328P programming for PWM generation.
I am trying to generate a PWM wave at PD5 pin the datasheet says PD5(OC0B/T1/PCINT21).
When I generate the PWM with help of timer0 overflow interrupt it works fine, however when I try to use timer1(tccr1a, tccr1b, icr1, ocr1b) and compb_vect isr it doesn't work. Can someone please guide how I can generate PWM at PD5 pin with the help of timer1? Can you please guide is it possible to use timer1 to generate PWM at PD5?


texts: Can I use a VFD to send power of a specific frequency to a frequency meter?

texts:
I have a beautiful old frequency meter from a power station, a "System Frahm" type panel based on vibrating reeds. It has two rows with 21 reeds in each, each going from appx. 45 Hz to 55 Hz. It says that it accepts 110 volts.

I want to be able to provoke the instrument to indicate frequencies of my choice, between 45 and 55 Hz. If possible, different frequencies on the two rows, but it's not mandatory.

I have access to a VFD, the Delta VFD004S21A 220V 1-Phase model. I know it can generate 3 phase power at the frequency and voltage that I need, but will it be able to run without driving a motor, or any other load? Would it work if I added a small 3 phase motor? Would I be better off with some kind of audio power amp + step-up transformer solution?


texts: How to select a power transistor to protect old school automotive ignition and headlamp switches

texts:
WAY back in my past I did some serious EE work, but not having used it for nearly 40 years, I'm a little lost on how I do this...

I have some 6 and 12 v cars I'm trying to restore and was lucky enough to find some very rare new switches. There won't be any more, and even good used ones are hard to find. It occurs to me I really should off-load the power from going through the switches - I'm only interested in protecting the headlight and starter solenoid / relay circuits because they're the high-power circuits and the ones most prone to trouble.

What I thought I'd do was get an IC - I do not want to use relays, solid-state only - and wire it in such that the switch is only used as a signal that throws the IC into action, with the IC passing current to the desired components.

I recall, however, that there's a need to run some (more than the minimum necessary to toggle the IC) current for "whetting" to act as a cleaning function for the switch contacts.

The headlights are rated at about 55W per bulb, so 110, plus a safety margin  would be good, and there are halogen upgrade bulbs available but I'm told they require too much current  for the original switches - a big reason the switches are so hard to find. Some poking around indicates these higher-output bulbs are rated at 100w per bulb, thus roughly doubling the power demand.

There are no published rating values available for the starter solenoid for my chosen type, but I'd guess that nearly all autos will have similar values for the "pull in" voltage / current on the solenoid, what will differ most is the current fed to starter motors - and that isn't involved in my goals here.

Of course, the voltage range available on 12v will vary from about 11 to 14.7 and on 6v, from about 5.5 to about 7.3, give or take a little, depending on state of charge and load - and whether a charging circuit is active or not!

It would be nice if  all the various versions of headlight bulb and the starter solenoid can be accommodated with one IC (per switch) per voltage range, so in theory I'd need two per vehicle and they'd be the same type and have the same circuitry. Just a guess here, but I don't think the starter solenoid draws 100w, much less 200w, but it is just a guess.

OK, that's where I'm at.

I'm unclear if anything is needed to accommodate the wiping current - or even how to come up with any value for it, or, (presuming I have to do something special to accommodate it other than just pick the correct IC) how to wire it. For all I know, there may well be an IC that will work as-is quite nicely, with no extra circuitry required since this is perhaps a more common problem than for just little-ole-me.

I'm also unclear on how to select (and find a vendor to sell)  the IC. I have a vague recollection that the wiring will be very different if I use an NPN vs PNP, but my skills are so rusty there's nothing left but the rust!

Any assistance appreciated.


texts:
I want to make a counter like gray code but this is different , so write this  code but help me to find an error

This is the code

module counter2(mainclk,rst , A,B,C,D );
input mainclk;
input rst;
output A,B,C,D;
reg A,B,C,D;
reg [3:0]qb;

reg anb,dnb,bc,nca,nd,na,nb,cna;
reg ap,bp,cp;
initial
begin
A=1'b0;
B=1'b1;
C=1'b0;
D=1'b1;

qb[3]=1'b1;
qb[2]=1'b0;
qb[1]=1'b1;
qb[0]=1'b0;

end
always @(posedge mainclk )
begin
    if(rst)
        begin
            A<=1'b0;
            B<=1'b1;
            C<=1'b0;
            D<=1'b1;
        end
    else
        begin
            anb <= A && qb[2];
            dnb <= D && qb[2];
            ap <=  anb || dnb;
            d_ff dffa(ap , 0 , mainclk , A ,qb[3]);
            bc <= B && C ;
            nca <= A && qb[1];
            bp <= bc || nca;
            @d_ff dffb(bp , 0 , mainclk , B ,qb[2]);
            cp <= qb[0] || qb[3] || qb[2] ;
            @d_ff dffc(cp , 0 , mainclk , C ,qb[1]);
            cna <= C && qb[3];
            @d_ff dffd(cna , 0 , mainclk , D ,qb[0]);
        end
end

endmodule

and the error is Error (10170): Verilog HDL syntax error at counter2.v(37) near text "dffa";  expecting "<=", or "="


texts: How to create a 120V-175V Variable Frequency Generator

texts:
I am dealing with a system that requires me to drive a capacitive load at 120V-175Vrms, AC square/sine wave at two frequencies: 50Hz and 2000 Hz @ Ipeak = 100mA. I am currently trying to find the best way to achieve this.

I had originally used a HV driver chip that had a supply of 300V, modulate the output to create a 0-300V square wave, high pass filter it, and finally send it to my load. The issue with it was how I generated my power supply. I had used a voltage doubler + voltage divider to obtain 300V from 120VAC in. As you all know, voltage dividers are terrible for usage a power supply from a variable load.

My next plan was to instead use a high voltage op-amp with square wave input, and configure it like a comparator to create a AC square wave, which would drive my load. The issue is that again the power. Here I tried to implement a SMPS from 12V to 175V, but the problem was the efficiency was terrible and thus I could not find any economical 12V power supplies to adequately drive my load.

So my question to all of you: is there a better way to generate an AC sine/square wave of 120-175Vrms @I=100mA? Or is there easy solutions to the problems I have faced in my implementations?


texts: Creating D-latch using Nand gates in Logisim?

texts:
I have designed a D-latch using NAND gates. The problem is when I convert it into a subcircuit the output is False no matter what my second input(clock input)is? It only works if I put the default clock input?

My D-latch

Subcircuit of the D-latch

As u can see the clock input wire is blue means it doesn't affect the output at all?


texts: I have a NiMH battery pack that needs replacing in a tv terrestrial field strength meter. The pack is 6 cells and is rated at 7.2v 2500mAh. It has 2 pairs of 2 wires so 4 wires that connect to 2 plugs on the internal board. I have opened up the pack. two of the wires are on the outside of the pack and not physically connected. I'm guessing it's some sort of sensor and if so can I just remove it and add it to another pack that doesn't have one? It doesn't appear to be connected directly in any way. I have seen similar packs but they only have the usual 2 wires.


texts:
In sigma delta we have SQNR based On OSR.
In SAR ADC I need to find the link between the number of bits(number of switches of SAR) and Its potential OSR and SQNR.
The only thing i have in SAR is the convertion time formula belloa
SAR_time_convertion=T_sampling+NT_switch .
How do i derive from its the F_sample (sampling rate) and signal frequenct Fd?
giving me OSR by fb/(fs0.5)
I know that the input has some frequency and the sampler of the SAR has frequency too but we have the switches too in there ,how it going to affect it?
Thanks.


texts: Necessity of an Inductor at CAN Transceiver end

texts:
Basically 120 ohm of resistor needs to be connected as terminator resistor at the end of the physical CAN channel.

My question is that here, what is the necessity of an inductor (L310) between CAN transceiver and physical CAN line ?


texts:
I have a mini water-pump/motor hooked up to an LM338 (similar to LM317, but capable of higher current output).

I set up the LM338 to create a 6.1-V output, from an 18-V input; this was done by setting R1 = 120-Ohm, and R2 = 470-Ohm in this circuit:

CASE 1: Using a DC bench Power-supply unit == SUCCESSFUL

When I power the regulator input with a power-supply unit (rated up to 3-A at 18-V), the motor runs off the regulator output very well.

CASE 2: Using a Laptop power adapter == UNSUCCESSFUL

But when I instead power the regulator input with a Universal laptop power adapter (rated for up to 6.5-A at 18-V), the motor exhibits this behavior: it ramps up and then within 1-2 seconds, slows down, and then after 3-4 seconds, runs much slower or not at all.

I also noticed the following in CASE 2:

when I initially touch the motor's V+ cable to the regulator output, it's creating a little spark at the contact.
the regulator gets really, really hot to the touch.


texts: Can Atmel Single Wire Interface (SWI) Support more than one device on the bus?

texts:
I'm interested in using multiple ATSHA204's on a bus.  UART or I2C if we have to use more than one pin, but my question is if we use Atmel's bit-banged SWI protocol, will it support more than once device?

I'm not seeing any kind of way to address more than one IC so my initial guess is no.

Supporting research:

http://www.atmel.com/images/avr274.pdf
http://www.atmel.com/Images/Atmel-8847-CryptoAuth-ATSHA204-SWI-I2C-Debugging-Saleae-Logic-Analyzer-ApplicationNote.pdf
https://www.sparkfun.com/products/11551


texts: Always getting HIGH reading from PIR on ESP8266-12e pin D7

texts: I have a PIR EKMC1606112 that I am trying to read using an ESP8266-12e. I have the PIR powered using a 5v regulator so I'm sure it is getting enough voltage. My problem is that when I have the sensor out from the PIR to pin D7 it always reads HIGH. I think it is because the PIR is out putting 4.5-5v @100uA but the ESP likes an input of 3.3v. So I think I need to use some resistors to create a voltage divider. My problem is I'm not sure what size I should use. 1/4watt should work but what resistance. One at X from output to D7 and two at X from output to GND. Am I correct in this assumption and is this the right configuration? What size should I use? 33, 100k, 220k???


texts: High speed multiplexing for multiple I2C devices

texts:
I'm trying to connect 32 I²C "root of trust" NXP A71CH devices.

https://www.nxp.com/products/identification-security/authentication/plug-and-trust-the-fast-easy-way-to-deploy-secure-iot-connections:A71CH

I'm trying to multiplex 32 devices for that chip.

I'm looking for a very fast way of multiplexing those 32 devices, an idea or schematic or a design.

The only solution that I found is to use an FPGA.  Is there a clever solution with just normal embedded microcontrollers ?

One chip costs 50ms, If I want to do 1000 signing, it would cost 1000*50ms. What I want to achieve is to have 1000signing with just 50ms cost. Is there a way of that without using FPGAs ?! Only with discrete components


texts:
I am working on a thyristor (in my case: Semikron SKKT 253/08) circuit operating at 400 V mains (3 phase). What I'm wondering is how one can calculate a thyristor  gate resistor so 12 VDC applied at pulse transformer can't damage the thyristor gate as in the following circuit:

In SKKT 253's datasheet, it states that minimum gate voltage is 3V and minimum gate current is 200 mA is required to turn on the thyristor. So I decided to drive a 1A pulse into its gate using factor of 5 according to Semikron manual page 152. Now back to my circuit:

    Ig = Ir2 = 1A (1)
    Vg + Vr2 + Vd2 = 12V -> Vg + (Ir2 x R2) + 0.7V = 12V (2)
    From equation (1) and (2), we have:
    R2 = (11.3 - Vg)/(Ir2) = (11.3 - Vg)/1
->  R2 = 11.3 - Vg (Ohm) (3)

Now I'm stuck at equation (3) because I can't decide which voltage Vg will be in case Ig = 1A. According to SKKT 253's gate trigger characteristic:

when Ig = 1A, Vg can be from 1V to 6V. Could anyone please enlighten me on this problem ?


texts: Under what conditions does an optocoupler work fastest?

texts:
I want to use the optocoupler FODM452R2 in my design. I want this optocoupler to run as fast as it can (i.e.; work with minimum propagation delay and least rise/fall times). What is the optimum R1, R2 resistor values and magnitudes of V1, V2 voltages?

I know that when BJTs saturate they turn off very slowly, so I have to avoid saturation. I also know that BJTs don't respond fast when the resistor value is too high in common emitter configuration. So there is a trade off. The value of R2 must be chosen in a way to optimize the BJT's switching speed.
Is there an optimum value for R1 as well? Or, is the smaller the better without damaging the LED? On the other hand, does the value of V2 have any effect on the switching performance?

The datasheet doesn't directly answer my question, or the answers are encoded in it in a way I can't understand. It only gives the variation in propagation delay with ambient temperature.

simulate this circuit – Schematic created using CircuitLab


texts: Is it possible to only use high side driver of fet driver ic?

texts: Is it possible to only use high side part of IR2103 mosfet driver ic, being fully functional, without adding low side driver external components?


texts: Can I use a button in place of a clock crystal?

texts:
So basically, I'm wanting to finally get into electronics. A little while ago I bought a few MCP3008 chips and analog pressure sensors. I've been wanting to build an compressed air system with it.

However... I want to avoid using a microcontroller.

I've done a lot of programming in the past, and I tend to like being able to debug things. So I was wondering; Is it possible to replace a clock signal with a simple button? The reason being... I want to slow down the clock so I can manually figure out how to work with the SPI. Possibly using some LED's, buttons, etc and recording the results.

I understand that buttons may need debouncing, etc... but would it work?

For the past hour or so, I've been googling around for an answer, and nothing definitive came up.

After looking at the datasheet for the MCP3008 here:
https://www.adafruit.com/datasheets/MCP3008.pdf

It seems that the minimum clock low/high time is 125 nanoseconds; there's no max listed. Does this mean if I hooked up a debounced button as a clock signal, it would work fine?

Thank you in advance for any help. I apologize if I'm missing something obvious.


texts: How can relays be rated at 10A for both 240VAC and 120VAC?

texts:
I have a small W1209 DC12V thermostat PCB that's had a small 12VDC relay attached.
The print on the relay says that it can do 5A @ 240VAC and 10A at 120VAC.
That makes sense, as both of those equal 1200 Watts.

However I'm wanting to wire it to a 2000 watt load at 240VAC. So have been looking at other relays I can replace the one on the PCB with.

And I'm seeing a fair number of relays which rather than having an 10A @ 240AC & 5A @ 120VAC rating they have a 10A @ 240VAC & 10A at 120VAC

So how is that possible? Is the relay that has 10A for both built for 10A @ 240, and 20A @ 120 too much for it, or is the rating fudged somehow?


texts: I've been working on a project which is turning my Raspberry Pi into a laptop, and have just run into a problem about an LED I will be powering off the Pi as a logo, as it requires more volts than the Raspberry Pi can give. I assume that this will be no problem and the light will just be dimmer than it would have been, although I don't know how this would affect the resistor I would use for it - would i just use the volts given by the Pi divided by the amps needed by the LED to get the resistor power, or would something change?


texts: Reflection coefficient in a microwave amplifier

texts: I have a question about the reflection coefficient in a microwave amplifier (two-port network), what is it and what is it based on?


texts: Are there existing electronic sensors that can sense if underwater or not?

texts: My goal is to to be able to read the water level percent in a small water tank. I was thinking  wiring sensors going up the side that read whether they are currently touching water. My plan is to wire the sensors into my Arduino and then calculate the percent full by the sensors that are touching water and the sensors that are not.  Are there existing sensors with this functionality? (are they cost effective?) Is there an alternative solution? Thanks so much!


texts:
I am building my own laptop, and found out that the motherboard for a laptop has to be designed based on the case.  So, I am designing my own motherboard.  The thing is, I have no idea how a motherboard works.  (I know about transistors, diodes, resistors, capacitors, etc.)

My question is:

How would i be able to design the motherboard (in an app), and what would be my ways of producing one for myself.

I would like a link to a good and (fairly) easy to understand tutorial too please.


texts: USB3/2 hub cascading (reverse hierarchy)

texts:
I want to implement multiple USB ports using one USB3.0 and one USB2.0 hub with four ports each.
The microprocessor I want to implement these ports for has just a single USB3.0 port left (of which the USB3.0 PHYs port is muxed and routed separately through a SerDes. The USB2.0 PHY is exported directly).
Now the obvious implementation approach is cascading both ports.
However I want to use all four USB3.0 ports.

My question is now whether it is possible to put the USB3.0 hub behind the USB2.0 hub (connections: MPU->2.0hub and MPU->3.0hub and 2.0hub->3.0hub). So the USBx lanes would separately be connected to the corresponding hubs and then the 2.0 hub supplies the 3.0 hub.

This way I would have all four 3.0 ports (with backward compatibility) available (as opposed to the hierarchical correct solution MPU->3.0->2.0), however I am not sure whether this kind of "port splitting" is possible.

Thx in advance


texts: Batteries have a constant charging speed from 0%→70% instead of being any faster at 0%?

texts:
A mobile phone I tested keeps charging at the same constant speed from 0% to 70%, which is 10 watts. It uses MediaTek PumpExpress (input power: 12V 0.83A, despite the wall charger is capable of 12V 1.5A).

Why does it not charge at e.g. 15 watts when at 0%?

Another phone charges at 9V 1.67A (15W) using Qualcomm fast charging. It maintains the exact same charging speed from 0% to 60%. I wonder, why it does not charge any faster while being at indicated 0% than while being at 60%.

Side note: I actually keep my batteries in the healthy percentage range.


texts: NO CD pin in SD card module by LC Studio?

texts:
I have a SD card module by LC Studio. I am interfacing it with PIC32. This module consist of 6 pins:

CS
MOSI
MISO
CLK
3v3
GND

I am following Lucio De jasio book to interface SD card. He has described to connect CD pin which is a Card Detect pin to detect the card but in my case I don't have cd pin. How can I detect for card detect state or is there any other option.?


texts: Back EMF in an inductor with an AC supply

texts:
If a pure inductor is supplied with an AC voltage we will always have AC current and time changing electric field in the circuit. That always changing electric field will cause changing magnetic field which will cause an EMF in an inductor which is always equal and opposite to the changing applied voltage (Lenz law.)

So every time the voltage is changing in the source it will face equal and opposite voltage in the inductor everytime. My question is if there is always equal and opposite voltage in an inductor against the applied voltage then how can the current flow in such a circuit?


texts:
I've got a project where I need to use an LCD module, so I started pondering around with one (1602A).
So far I've wired it up with my microcontroller which is an Atmega168PA and written an initialization code for it based on the instructions found here.
I think I've done exactly as said in that instruction (I'm trying to use a 4-bit interface), but still haven't gotten the thing to work correctly.

To me it seems that for some reason the LCD module is not initialized correctly as after the MCU and LCD have both been powered up I only see one (first) line full of full-dotted characters (0xFF) and second line is blank although the screen should be cleared during initialization and cursor should be visible.

I've included my code below:

#ifndef F_CPU
#define F_CPU 8000000UL
#endif

#include <avr/io.h>
#include <util/delay.h>

void lcdLatchEnable (void)
{
    PORTC |= (1<<4);  // enable latch pin

    _delay_us(2);  // wait specified time

    PORTC &= ~(1<<4);  //disable latch pin
}

void lcdWriteNibble (uint8_t byte)  // set data line according to upper nibble in function parameter 'data'
{

    if (byte & 0x10)     // copy fourth bit value on the output pin
        PORTC |= (1<<0);
    else
        PORTC &=~(1<<0);

    if (byte & 0x20)     // copy fifth bit value on the output pin
        PORTC |= (1<<1);
    else
        PORTC &=~(1<<1);

    if (byte & 0x40)     // copy sixth bit value on the output pin
        PORTC |= (1<<2);
    else
        PORTC &=~(1<<2);

    if (byte & 0x80)     // copy seventh bit value on the output pin
        PORTC |= (1<<3);
    else
        PORTC &=~(1<<3);

}

void lcdSendByte(uint8_t byte)
{
    lcdWriteNibble(byte);  // send upper nibble
    lcdLatchEnable();  // latch the upper nibble
    byte <<= 4;  // shift bits in byte left 4 positions so lower nibble would be sent next
    lcdWriteNibble(byte);  // send lower nibble
    lcdLatchEnable();  // latch the upper nibble
}

void lcdSendNibble(uint8_t byte)
{
    lcdWriteNibble(byte);  // write nibble to output pins
    lcdLatchEnable(); // latch the values into LCD module
}

void lcdInit (void)
{
    PORTC &= ~(1<<5); // configure LCD module into instruction mode (R/S line = 0)
    _delay_ms(150);  // wait more than 100ms after power on

    lcdWriteNibble(0x30);  // special case function set
    lcdLatchEnable();   // latch in the values
    _delay_ms(5);       // wait more than 4.1ms
    lcdWriteNibble(0x30);  // special case function set
    lcdLatchEnable();   // latch in the values
    _delay_ms(1);       // wait more than 100us
    lcdWriteNibble(0x30); // special case function set
    lcdLatchEnable();   // latch in the values
    _delay_ms(1);    // wait more than 100us

    lcdWriteNibble(0x20);  // initial function set to change interface
    lcdLatchEnable();   // latch in the values
    _delay_ms(1);   // wait more than 100us

    lcdSendByte(0x28); // send function set
    _delay_ms(1);  // wait more than 53us

    lcdSendByte(0x08); // display off, cursor off, blinking off
    _delay_ms(1); // wait more than 53us

    lcdSendByte(0x01); // clear display;
    _delay_ms(5); // wait more than 3ms

    lcdSendByte(0x06); // Entry mode set to increment and shift off
    _delay_ms(10); // wait more than 53us

    lcdSendByte(0x0C); // display on, cursor on

}

int main(void)
{
    DDRC |= (1<<0)|(1<<1)|(1<<2)|(1<<3)|(1<<4)|(1<<5);  // configure pins as output for LCD module communication
    PORTC = 0x00; // make sure that all the pins are configured as low

    _delay_ms(150);

    lcdInit();

    _delay_ms(100);
    lcdSendChar(0x30);

    while(1)
    {
    }
}

And a picture of the display after it should be initialized and printing character 48:

UPDATE:

Added schematic of my wiring:


texts:
In a BJT or MOSFET circuit we have this curve:

What is that q-point? From my research I have the following information:

  The operating point of a device, also known as bias point or quiescent point (or simply Q-point), is the DC voltage and/or current which, when applied to a device, causes it to operate in a certain desired fashion.

and

  The operating point of a device, also known as bias point, quiescent point, or Q-point, is the steady-state voltage or current at a specified terminal of an active device (a transistor or vacuum tube) with no input signal applied.

But I'm still lost as to what Q-point is. What is q-point? Why is it important? Why is it located at that position on the graph? What does it tell us?


texts: Is combinational logic affected by the clock in FPGA?

texts:
I have a question whether a computational logic expression is affected by the clock if it is in a process and all the inputs are listed in the sensitivity list.  If a change happens in one of the inputs, it will just change without having to wait for the next clock cycle?

I also have a question which is related, whether if for example you have a case statement which is not in a process will it be affected by the clock or if a change happens in one of the inputs it will automatically change without having to wait for the next clock cycle.


texts:
i have a design project, which includes designing a single stage amplifier (cmos device) i have to use telescopic p mos load to design degenerated common source single stage amplifier.
what exactly is a telescopic load, i have tried googling it but all i found out was about telescopic op-amp , telescopic cascode.
Any help would be appretiated


texts: Software to design and simulate circuits?

texts:
Possible Duplicate:
  Circuit Simulation Software

My friend is starting to learn some basic electronics as a hobby, and i have some knowledge on the subject from school. So I am looking for a software that will allow me to design and visually simulate simple circuits, for example I want to make a couple of leds to blink using a few transistors, and I want the software to visually show me the leds blinking.

Is there any software that can do this?


texts:
http://www.carlingtech.com/sites/default/files/documents/M-Series_Details_%26_COS_021114.pdf

This circuit breaker have two different current ratings, depending on amperage range: Full Load Amps and General Purpose Amps. What is the difference between them?


texts: Build an H-Bridge Motor Driver with 4 N-Channel MOSFET

texts:
I have bought 4 N-Channel MOSFETs to build an H-Bridge Motor Driver.
My Motor drive and my power supply voltage is 12v.
My TTL logic voltage is 5v as I want to speed up/down the motor with uC PWM.
Now I have understood that I have problem with driving High Side MOSFETs as their Gate Voltage must be bigger in respect to their Source voltage.
What are my options now? shall I change them to P-Channel MOSFETs?


texts: How to find out which process triggered join_any in verilog

texts:
I have three tasks running in parallel and the fork joins when one of them gets completed. I would like to know which one was completed first and caused the fork to join. Is there a way to know it?

fork
   task1();
   task2();
   task3();
join_any;


texts: Why are resistors tolerances relative instead of absolute?

texts:
Every resistor has a tolerance, this provides the user with an idea of the accuracy of the product. This tolerance is represented by a percentage. This means: a big value resistor will be less accurate than a small resistor with the same tolerance.

$$1kΩ 10\% ∈ [900Ω , 1100Ω]  → 100Ω$$
$$100Ω 10\% ∈ [90Ω , 110Ω] → 10Ω$$

The 100Ω 10% resistor will be closer to 100Ω than a 1kΩ 10% will be close to 1kΩ.

Why is that? Because high value resistors are harder to produce than small ones? If not, why is tolerance a percent and not a fixed amount of Ohms? Why are tolerance relative and not absolute?

These questions are also valid for capacitors, but I'm pretty sure the answer will be the same.


texts: Three terminal LED pilot. What's the matter?

texts:
Long story short, I've purchased a 24VDC LED pilot and I've got a 12VDC pilot with three terminals instead. I was wondering what are each one of those three terminals for, the terminals have standard names (X0, X1, X2) but in the case there are additional names written (C, S, T respectively).

All the google searches I've done lead to me to electronic LED flashers but I don't think this is what I'm looking for. The LED has no serial number I could use to check it out.

This is the symbol printed in the case:

EDIT1:

I've asked the manufacturer for documentation and they've sent me the datasheet, this LED has lamp test function and the additional terminal serves to connect to a lamp test circuit (whatever it is).


texts:
When resistors are serially connected, the current is the same through the whole circuit. To my knowledge, the electric current is electrons traveling.

Also, the power of the generator equals the power lost...

Since current stays the same through all resistors, what exactly is being lost here? (when connected to a voltage source)

If the amount of electrons and their speed when entering the resistor is the same when they "get out" of a resistor, what generated heat? What was lost in the process of lighting a bulb? If no electrons were lost why is a battery not an infinite source of electricity?

What happened in the resistor that made it heat up?

Keep in mind all the information here are only true to my knowledge, which is flawed, if I am wrong, please correct me.


texts: 2nd Order transfer function to difference equations

texts:
I'm wondering if someone could check to see if my conversion of a standard second order transfer function to a difference equation is correct, and maybe also help with doing a computer implementation.
Starting Equation:
$$\frac{Y(s)}{R(s)}=\frac{\omega_n^2}{s^2 + 2\zeta\omega_ns + \omega_n^2}$$

Using the backwards-difference equation,
$$s = \frac{1-z^{-1}}{T}$$

Result:
$$a = 2(1-\zeta\omega_nT)$$
$$b = 2\zeta\omega_nT + \omega_n^2T^2 + 1$$
$$y(k) = \frac{r(k-2) - ar(k-1) + br(k)}{\omega_n^2T}$$

Now, how would someone implement in an algorithm to filter data (since this is just a 2nd order low pass filter)?

 % Coded in MATLAB
time = 1:1024;
wn = 0.5;
zwn = 1.414;
T = 1;
a = 2*zwn*T + (T^2)*wn^2 + 1;
b = T*wn^2;
c = 2*(1-zwn*T);
output = 10*sin(0.05*time + 10) + 4*sin(1*time+180);
y(1) = output(1);
y(2) = output(2);

for i=3:length(time)
    y(i) = (1/b)*(a*output(i) - output(i-2) + c*output(i-1));
end

I would expect this to filter the output's 1 Hz noise, but all this does is reduce the amplitude of the entire graph. Where am I going wrong?


texts: Is there such a thing as a programmable power sink?

texts:
Is there such a thing as a power sink equivalent to a benchtop power supply, where I can set the wattage (voltage, amperage) to be consumed?

What is this device called?


texts: Characteristic impedance behavior with frequency

texts:
The characteristic impedance of any transmission line is derived as
$$
Z_0= \sqrt{\frac{R+j \omega L}{G+j \omega C}}
$$
where R is series resistance per unit length, L is series inductance per unit length, C is shunt capacitance per unit length, and G is shunt conductance per unit length. The real and imaginary part of the above equation can be derived assuming that \$ \omega L >> R\$ and \$ \omega C >>G\$
$$
Z_0\approx \sqrt{\frac{L}{C}}+\sqrt{\frac{L}{C}} [\frac{R}{2j\omega L}-\frac{G}{2j\omega C}]
$$
According to the assumption made above the imaginary part should be very small and thus can be neglected. Therefore the characteristic impedance is almost purely real and is given by \$\sqrt{\frac{L}{C}}\$. (I know that the imaginary part appears because of non-zero value of series resistance R and shunt conductance G, which accounts for the transmission loss.)
Theoretically for infinite frequency \$\omega\$ the value of \$Z_0\$ approaches \$\sqrt{\frac{L}{C}}\$, which is a real number. But I have seen in some cases where \$Z_0\$ is reported to have both real and  imaginary part at some frequency. For example, some authors reported \$Z_0=4.95+j7.6\$ ohm/m for a coaxial cable operating at 1GHz. As you see the imaginary part is even larger than the real part. For small, and constant(?) values for R, G, C, and L I expect the imaginary part to be almost zero at 1GHz. So what happened here? What could make the above assumptions fail? Does R change a lot with frequency?


texts: How to calculate the number of cycles my linear actuators can run

texts:
I've recently bought a set of linear actuators for a personal project of mine and I was wondering how many times can this linear actuator run before my battery runs out. (My battery is rated 12V, 8000mAh)

Here is the link for the linear actuators ive purchase, its rated power is 20W. Is it possible to calculate the number of times it will take to drain my battery?

https://www.banggood.com/DC-12V-50-500mm-900N-Stroke-Tubular-Motor-248121620-Inch-Linear-Actuator-Motor-p-1526731.html?rmmds=buy&ID=47877&cur_warehouse=CN


texts:
I'm trying to add "optional" debugging test points to an existing, very dense 4 Layer PCB design (signal - GND - PWR - signal). I'd like to change the existing PCB as little as possible. My idea was to change the outline as shown below, adding a small debug area through a small neck (approx 5 mm tall by 1 mm wide) to the existing PCB:

This way, in an ideal world, when I get my PCBA's back from the manufacturer, and everything works, I can simply snap off the debug PCB and use the existing PCB as intended in end use. The current end-use mechanical dimensions don't allow for changing the PCB size. Then, before doing a bigger spin of PCBs, I delete the debug PCB, clean up the debug traces, and am ready to go.

Or, more realistically, if things aren't working as intended, I can attach logic/scope/meter probes easily to the traces via a 0.1" header (or similar) I've routed here. Figure out what went wrong, fix any mistakes and try again.

So the questions:

Is this a reasonable approach, if trying to minimize the changes to the existing PCB? Other suggestions welcome.
How can I minimize the chance that snapping the connection point will damage any existing PCB traces? Right now the route-keepin to board outline spacing is 0.25 mm = ~10 mil. I suppose increasing the width of the "part to snap" and aiming to snap closer Debug PCB should help, but other ideas welcome.
I don't intend to extend L2 (GND) and L3 (PWR) to the Debug PCB, but should i still worry about them shorting at the "snap" area? Any ideas to mitigate this?


texts:
I am wanting to design an H bridge to control a linear actuator. 12vdc motor, max current 3.2A under load, and has built-in travel limit switches (ie motor stops at full extension and retraction). There are two wires, for + and - , the polarity needs to be reversed (sorry, I’m sure this is pretty standard stuff so far).
The control I will be using is a 3 wire system ... - 12v, + 12v, and switched + 12v. The constant power is routed direct, whereas the switch wire comes from an ECU. The ECU does have internal H bridges, however if I program it for this operation, it cannot handle the current draw (there will be up to 16 of these actuators).
I have ‘borrowed’ a circuit board from another device (motor driven valve) which works, as per the pic below. However that contains its own limit switches (top right and top left) which I don’t need. The power supply to the motor in centre top, with supply power and switching DIN plug bottom right.
I’d like to design/build something similar, and the actuator will only need to extend or retract fully, and I do not need any speed control. Pretty much the same as the pic but without the limit circuits.
Am hoping someone can help me with this.


texts: stack 0805 sized component on 1206 sized footprint

texts: I wonder if it's generally okay to stack an  0805 sized footprint over a 1206 footprint, without any problems in the assembly machine?


texts:
I'm new in this group, I hope to be welcome and help you whenever i can.
At first i need your help... i'm assembly a drone ( quadcopter ) , and testing the ESC with the motors, and i have issues.
I buy the next components:
My ESC is the next generical ESC ( from AliExpress ) : https://es.aliexpress.com/item/32837...5b0a63c0qh1PAA
My motors are the next: https://es.aliexpress.com/item/32260...5b0a63c0Pri4Fx
My battery is a 3s battery (11.1 V 3000 mAh ) : https://es.aliexpress.com/item/32963...5b0a63c0Pri4Fx
I'm using Arduino, with the next simple code:
        #include <Servo.h>

        Servo ESC1;
        int pot = 0;

        void setup() {

        ESC1.attach(9,1000,2000);

        }

        void loop() {
        pot= analogRead(A0);
        pot = map(pot,0,1023,0,180);
        ESC.write(pot);
        }

The output PWM signal is ok ( i think ).. is a 50 Hz signal that change the high width from 1 ms to 2 ms.
well, i connect the circuit as you can see in the attach draw.
My problem is the next:
When i connect the battery the motor make a few sounds like "beeps" and as i saw in the datasheet of the ESC this is ok, but when i turn the potentiometer to set a higher speed to the motor, it spins faster but for a while and then stop. Also, i notice that the temperature of the ESC and the motor increases significantly. I thougt that maybe the ESC is cutoff the signal to the motor for security (due to temperature increases, but when i start again without waiting for temperature drop it makes the same.. )
I try to setting the Throttle Range reading the datasheet of the ESC and apparently it is configured correctly, but it doesnt work ...
I attach photos of my connection.

I hope somebody can help me pls! Thnks


texts: NMOS - connect body to source or ground?

texts:
I've had some weird occurances in labs etc. (using Cadence) where sometimes we would be told to connect the body/bulk/substrate terminal of our NMOS devices to the most negative part of the circuit (ground) and sometimes we were told to connect the body/bulk/substrate terminal to the source?

Which is it and why? I can recall it did change my circuit simulation results too by a bit. Also, I have the same question for a PMOS (connect to Vdd(most positive part in circuit) or to source?)??


texts: Do we need isolate the MCU from the relay driving transistor

texts:
This question came to me when I saw this question driving a relay with transistor and Opto-isolator.

As Olin Lathrop had pointed out in his answer, relays already provide isolation between the coil side and the switches. Then any reasons to isolate the MCU from the relay driving transistor?


texts:
I am having this op-amp Comparator.
My circuit is similar to this circuit present in the datasheet of the IC, page 21.

I have this circuit now in my board which I want to test. I have never tested an op-amp comparator section before.
So, can someone help me and guide over here on what tests should I perform on the above circuit and validate the behaviour of the comparator?
Like, the important parameters of an op-amp (which I know) are like, the slew rate, input voltage, input bias current, output current and feedback voltage.
I don't know what to test in the above circuit and how to validate that the circuit is working fine as expected.
Questions :

Don't not mind about the circuit and other circuit specifics. I just want to know what are the important tests that one needs to perform for an op-amp comparator circuit? Can someone list the most important ones?

How to measure the slew rate and feedback voltage of an op-amp comparator in the above circuit?


texts: LED on delay circuit for MANY LEDs in PARALLEL

texts:
I found a very simple circuit that delays the switching on of an LED.
With the given value of capacitance, there is a 0.7 second delay between the first and the second LED.

The second LED has about a 0.7 second delay between the first one with the given value of capacitance (4.7uF).
However, I want to use many LED's in parallel, instead of just one LED (I'm trying to write my name with LEDs where each letter has a certain delay between the previous letter). It didn't work when I just put more LEDs in parallel in the existing circuit. What are the necessary changes I should make in the circuit for it to allow many LEDs in parallel?
I'm not well versed with electronic components. In fact I just barely understood this circuit. It would be great if I got some help with this! :)


texts: rotary switch / turn knob? how to call it?

texts:
Im looking for a switch-like rotary knob, that i can turn left and right. Its outputs a simple 'pulse'. You find these in selecting/setting numbers on assorted electronics.  You can keep turning them (both directions), there is no absolute '0' point. But i need to know, if you turn left or right.

Its for a simple Arduino project, i want this rotating know/switch to increase the number on a LCD (turning right) and decrease the number when turning left.

But whats the name ??

Thanks.


texts: Why common mode filters are usually found on AC input stage and not the output stage of an isolated smps?


texts: Why are there not more cores in modern CPUs?

texts:
Many often confuse the meaning of Moore's Law... it refers to the number of transistors on a chip, not performance.

A while back, it became apparent that the gains from increasing clock frequency on chips was not worth the expense and chip makers started adding extra cores to CPUs.

However, the increase in the number of cores on consumer chips has not matched the increase in transistors on each chip.

I surmise that a lot of these transistors have gone into features such as prediction logic ect, because it is difficult for some workloads to be parallelized, or many programmers find parallelizing their programs too time intensive, or CPUs are optimized for existing programs.

However, from my perspective, I would like to see transistors go into increasing core count and on-chip-cache as this would benefit my programs more than marginal increases in single threaded performance given that I have no trouble writing multi-threaded code for most of my particular goals.

If I use the extra transistors for a really large cache, I will not have to make as many trips to memory, which can also be a big performance booster.

Am I incorrect as to the reason core counts do not seem to be increasing at the same rate as the number of transistors? Or is there also some diminished return for increasing core count even for easily parallelized work loads such as memory bandwidth?

Why have core counts not increased at anywhere near the rate as the number of transistors on a chip?

Edit: Just because a workload can be run in parallel does not mean it is an appropriate task for a GPU ect which tend to deal with doing a lot of floating point calculations. CPUs have diverse general purpose capabilities which more specialized chips lack.

An example of this could be, let's say I have a set of 50 heuristic functions I need to run against a large set of data that is already in memory.

This is easy to multi thread, give each function its own thread, and you can multi thread it further by diving up subsets of the data for each function (if the data is not highly interdependent). You could easily satiturate all the cores of even a top end Xeon processor, but you won't be able to make much use of a GPU or SIMD.

Or, just a common web application serving many different requests that do not need to be coordinated.

Or, just several different applications running on the same server for political or administrative reasons.


texts: Calculating the capacitor values to control ceiling fan speed

texts:
I have an old ceiling fan motor that runs with a 1.5µF run capacitor, at what I believe is, its full intended speed.

With the help of some folks here at StackExchange I've wired everything up as in the image below, also refer to the schematic further down this question. The motor seems to be running well.

The next step is to add a 4 way rotary switch that selects between off and 3 different speed settings. I need to figure out the capacitor values I can use in C3 and C4 in the schematic below to achieve the slightly slower speeds for speed settings 1 and 2, with 3 running at full speed.

http://www.schematics.com/project/ceiling-fan-speed-control-27511/

I do believe that the capacitors need to be in parallel for the capacitance to add up, and slow the motor down, please do correct me if I'm wrong. As far as I can understand the capacitance shifts the phases apart further in the two coils.

The simplest approach might be to go and buy some 1µF to 1.5µF caps and play around with different configurations. I already know I need a 1.5µF to get and keep the motor running.

Is it safe to say I can just add another +/-1µF/1.5µF in parallel for my 1st speed setting, and another 1µF for the 2nd setting to slow the motor down? Thus, I have the following configurations:

Speed = 1 : 1.5µF

Speed = 2 : 1.5µF + (C2)1µF = 2.5µF

Speed = 3 : 1.5µF + (C3)2µF = 3.5µF

If this bit of information helps, our supply is 220V at 50Hz, and the motor has, what appears to be 14 coils, according to my counting through the holes in the motor casing.


texts:
I am currently taking an online course on probabilistic graphical models. In the section on belief propagation (BP), specifically loopy BP, reference was made to Robert Mc Eliece's 1988 paper Turbo Decoding as an Instance of Pearl’s “Belief Propagation” Algorithm and turbo decoding.

As I understand it, the key breakthrough with turbo decoding is that one can obtain greater channel throughput by operating closer to the theoretical limit of attainability as given by Shannon's theorem. This increased throughput is achieved at the cost of greater computational complexity in the decoder.

Further I understand that turbo decoding has become widespread and virtually ubiquitous in modern communication channels.

Is my understanding correct?

Also is this currently an active field with development of new decoding algorithms or has it stabilized?


texts: Is this inductor suitable for using in a 1A boost converter?

texts: i have been working on making a boost converter circuit to incorporate into my PCB and have ordered these inductors. I believe i have tracked down the datasheet(difficult with these cheap chinese parts) and it looks like the max dc current is 1A which is fine for me. i just wanted to ask if i was correct in my judgement as i am not completely confident and dont want to use an inductor which cant handle the current. thanks!


texts: Using a mixed technology, SMD and THT components in one PCB

texts:
I want change design from Through-hole technology to SMD design. Some components have no SMD version, for example some transistors in TO-92 package, and Power Mosfets, which available in DPAK SMD package, but since it requires a heat-sink, there is no much benefits of using SMD Mosfets with heat-sinks(DPAK heat-sinks have amost the same size as regular heat-sinks).

For example, I can change all the ICs, resistors and caps to SMD versions, but there still remain Power Mosfets and TO-92 transistors in THT version.
Is there any disadvantages of using mixed technology, when use SMD components with some Thru-hole components mixed in one PCB, except more complexity and thus extra cost? In terms of reliability?  The quantity is small, 10-20 pcs, not mass production. All components in one side.


texts: Is a specific voltage required for a specific frequency (in processors)?

texts:
I read in a paper about latency in dynamic voltage and frequency scaling, that the voltage has to "support" the frequency. According to this paper, if the frequency is too high for the voltage it causes a "dangerous state" (I love how specific they are).

Can somebody please explain what the relationship is? Or point me in the right direction? Also, an equation would be great.

My background is in computers and my understanding about electrical stuff very limited. I already looked online and from what I found, there does not seem to be a relationship. Maybe I'm misunderstanding it.

Thank you very much in advance!


texts: How to use thevenin theorem in this example?

texts:
Use thevenin theorem to find the current through 2 ohm resistor also find thevenin voltage and thevenin resistence.

My approach:First I open circuited the resistance through 2 ohm resistor then used voltage division to find the thevenin voltage but got the wrong answer.
My calculations:
Vth = 9V * ((6+4)/(4+4+6))= 6.43V.

But the Thevenin voltage in answer is 2.571 volts.


texts: Why do we use low resistance cables to minimize power losses?

texts:
Generally, one would like to minimize power losses via Joule heat. Intuitively, using low resistance cables (for example by using materials with low resistivity like copper) should do a better job than highly resistive cables.

However this is not what I get mathematically. Here's my reasoning:

Let's assume that Ohm's law holds, so \$V = RI\$, and let's assume that our power source is a voltage source, so \$V\$ is constant and fixed. Let's consider 2 cases, one with a resistor R and the other with a resistor R/2, where "resistor" means the total resistance of the electrical circuit, so cables + load.
In the 1st case, the power dissipated is \$I^2R=V^2/R\$. In the 2nd case, it is \$I^2(R/2)=2V^2/R\$, i.e. twice as much power is dissipated if we halve the total resistance of the circuit. It seemed counter intuitive at first to me, but when one halves the total resistance of the circuit, we double the current, and since the power losses go like \$I^2R\$, the increase in current more than offsets the decrease in resistance, so overall the power dissipated increases. So, I am lead to wonder why would one want to use lower resistive cables? Wouldn't it mean a higher current, thus a higher dissipated power in the circuit?

The only reason I have found so far is that the voltage available to the load is greater when the cables have a low resistance. I am wondering if that's the reason why we use low resistance cables, because it seems like it still dissipates more power than if we had picked a material like iron instead of copper. So it seems that the premise of the question may be wrong, i.e. in reality we might not seek to minimize power losses.


texts: Three-phase rectifier circuit simulation

texts:
Is this the correct way to simulate a three-phase full bridge (6 pulses) rectifier?

I ask because I have tried this first without the two capacitors, just one, and the capacitor
seems to have discharged (or charged in other direction) in some parts of the wave.

I think this is because the line-to-line without ground reference, then I added two capacitors with a ground (that is in common to neutral) like show in the image, and it seems to work fine, but it should difficult some simulations I think.

(The line-to-neutral RMS voltage is 220V and line-to-line RMS voltage is 380V).

I'm correct about the assumption?

Also, is it acceptable (yes that depends on regulations and so on, but lets take as acceptable) to just wire a plug with line to line wiring (plus ground for safety), without the neutral wire as the equipment will not be connected to neutral?

Update

@ConnorWolf suggested doing the differential measurement across the two rails. Although I have that in mind too, I didn't have doing it (but needed sometimes) and as it says its just implementing it by math using the difference between the two measured points. It worked, I just don't know how other components that my refer ground would get to work.

The V-BUS(+) in the graph is the difference between V-BUS(+) and V-BUS(-) so, V-BUS(+) - V-BUS(-).

Also, from the comments of the non-reader @Naib I put the power supply floating removing the ground reference from its neutral (that I think is not what @Naib is suggesting, I will edit if it is), and putting the ground in the DC-Link without any high-impedance resistor.


texts: Is a floating pin equivalent to a very weak pull down?

texts:
I know that if a MCU pin is configured as "input" and it is not connected to any pull up/ pull down resistor, it is said to be floating.
In this situation, we could say that the pin is in series with the (very) high input impedance of the MCU, which is eventually connected to ground.
So we could say that the pin is in a (very) weak pull-down condition, with the MCU input impedance acting as the (very high) pull-down resistor.
So basing on this assumptions, if we suppose that no significant interference acts on the pin, I would say that (if we wait long enough) the pin voltage will be eventually "pulled to ground". Where am I going wrong?


texts:
simulate this circuit – Schematic created using CircuitLab
A typical way of analysing the unity gain buffer is:
Where A is Open Loop Gain

Vout = A(Vin - Vp) and Vp = Vout therefore
Vout = A(Vin - Vout)
Vout = AVin - AVout
Vout + AVout = AVin
Vout (1+A) = AVin
Vout / Vin = A / (1+A)
if A >> then 1+A ~ A
Vout / Vin = A/A = 1

I would like to get an understanding of how this works from initial conditions ie step response
At t= -1 Vin, Vp and Vout = 0
At t= 0 Vin = 1V and as Vp = 0, Vout = A(1-0) = A
As Vout = A then Vp = A such that Vout = A(1 - A) = A - A^2
Subbing again gives Vout = A(1 - (A-A^2) = A(1-A+A^2)
This is obviously just going to run away so must be incorrect, perhaps it is my initial condition assumption that is wrong?
Alternatively using the simplified model of an op amp:

I could assume that at t=0 Vp = Vin therefore Vout = Vin
However Vin = A(Vin - Vin) is a contradiction
Obviously this is a well known circuit so I must have a fundamental misunderstanding but what have I got wrong?
*Edit
Just to clarify the purpose in asking,
I'm trying to get an understanding of how negative feedback works. The standard analysis at the start of the question is effectively time independent and I would like to know how the output rises with time


texts: MOSFET with Integrated Driver for Boost Converter

texts:
simulate this circuit – Schematic created using CircuitLab

Trying to build a boost converter using a PIC microcontroller with minimum number of external components. Was hoping to find an NMOS with integrated driver (dashed rectangle above) in a small surface mount package (e.g. SOT-23-5) to use as the switch and drive it directly from the PIC output pin. Searched for 'gate drivers' and 'power switches' but couldn't find any suitable part.

Edit:
This is a commonly used configuration (driver+MOS) and was under the impression that more devices in a single package would be available. Why are devices like this seemingly unobtainable?


texts: How to use Lightsensor relay with 3v output

texts:
I want to find solution for one small circuit  with Light sensor.

I need one small light sensor to drive 3v output.
The power of all the circuit must be 5v and when the light sensor is off (no light) then to open (power ON) the 3v circuit.

Is that possible?
Thanks for the help.


texts: Designing 0- 300 mA current source with 12v Voltage supply (load = constant 40ohm)

texts:
I'm trying to design a 0 to 300 mA controlled current source, the problem is that the supply voltage is a normal adapter with a 12v output. I'v already tried several op-Amp based circuits but the voltage drop over the load exceeds the power supply in all of them. suggestions for a circuit?
Load is a constant 40ohm device.
Thank you all


texts: Using single resistor to receive 5v signal on the 3.3v rated pin

texts:
I have been investigating ways to safely receive 5v signal on the input pin that can only support 3.3v input signal. I came across an article that states that it's possible to only use a single 10k Ohm resistor to achieve that. I can understand how this can prevent too much current from flowing through the schottky diode, but I am still skeptical this resistor would produce the necessary voltage drop for the signal that goes further into the MCU since the resistance of the resistor that is placed after diodes is much higher than 10k.

Will the 10k resistor work for this purpose and if so, what voltage drop would it produce?

Thanks a lot.


texts:
Update:
I swapped out the LM2596 with the TI version from Digikey and so far so good.  My first batch of LM2596 chips are from China (unknown brand). Anyone else ran into issues with China versions of LM2596?

I'm using a LM2596S-12 to regulate 36v DC input to 12v with custom PCB.  I've made 12 boards and all seems to work initial.  Out of the 12 boards, 3 of them have random shutdown.  During shutdown, the output of the LM2596S-12 have 0v and the 36v DC input is still on.  I can't get the LM2596S-12 to function again until power reset (remove input voltage then re-apply input voltage).  At times, the shutdown occur after running for couple hours, and other time it would run fine for over a week before shutdown.  I check to temperature and LM2596S-12 stays cool to touch when working.  The typical load for output of LM2596S-12 is about 200mA to 400mA.  I've even added a small heatsink on the LM2596S-12 but random shutdown still occurs.

I'm using typical ref design for fixed output voltage for LM2596.

For my circuit, I tied the pin 5 (on/off) to ground for continuous on.  Cin is not shown the below schematic crop.

My layout


texts: PCI-Express timestamp source that can be used in Windows?

texts:
I need to do some accurate time measurements and I need to have access to a affordable / cheap and somewhat more reliable timestamp/time source than what is built in Windows/CPU.

I need to read the timestamp values from Windows.

Can anyone give some hints on what to use to get a better timestamp?

I guess some kind of PCI-Express based hardware timer card?

I don't need super-high accuracy, but a resolution around 100ns would be good.


texts: Arduino controlled audio amplifier gain?

texts:
I've building a preamplifier that also functions as a headphone amplifier.

When no headphones are present, the gain of the internal opamps should be 1x (unity), so that the signal can be passed out the back of the device at line level for a speaker amplifier to further process.
When headphones are inserted, the rear outputs disable, and the user should be able to select from no gain (1x), low gain (2x) or high gain (6x) to suit the impedance of the headphones.

The entire operation will be controlled from an Arduino. I'm using a switched headphone jack to determine when a set of headphones has been plugged in. The gain should be selectable using a rotary encoder or push button talking to the Arduino, rather than a mechanical switch.

Questions:

1. What would be the best solution to allow the Arduino to control the gain of the amplifier - the dotted green section in the diagram? Transistors or relays, and why? I preferably don't want to add another IC into the mix, and the simpler the solution the better.

2. Given that I'm looking to keep electrical noise as low as possible, are there any concerns I should have with regards to electro-mechanical switches introducing audible noise in the signal?

3. While switching from one gain setting to another, would there be a chance that the negative feedback loop is broken for long enough that the gain skyrockets, causing a moment of noise/thumps or banshee squealing? Basically, is the speed with which the new connection is made going to be an issue?

There's also a significant chance I'm trying to "over-engineer" my solutions here, so any suggestions are welcome. Novice alert.

Clarification: The Arduino is being used to digitally control volume using a PGA2311 IC, and it also handles source (input) selection. So it’s here to stay :)

Disclaimer: this question is similar to one answered over here, but I'm not averse to using multiple relays if that's the most efficient/noise-free/easy solution to implement.


texts: ATmega communication with I2C + extender or with ENC28J60 ethernet module?

texts:
I want to communicate between ATmega328P µC's over 'long distance'. The ATmega µC's will be 5m to 20m apart and the total length of the chain will be around 50m with up to 10 ATmega's in one chain.

What would be the better option:
Making a I2C bus with P82B715P or P82B96P bus extenders or making an ethernet bus with ENC28J60 modules?

Cost and space are important. All modules also need to be powered over the data cable.

At first I thought to go for the P82B715P modules, connected with 4x2 Cat5e cable, but after reading a lot of negative blog posts on long-distance I2C, I started to doubt. Hence my question.


texts: How can a low efficiency antenna be used for receiving but not for transmitting?

texts:
For the reciprocity theorem, if an antenna has a low efficiency in transmission, it has the same efficiency when receiving.

In literature, it is usually said that one shouldn't use a low-efficiency antenna for transmitting because a lot of power would be wasted.

However, I often read that if it's only for receiving signals, a low-efficiency antenna might be used. Why? In such a case, you're wasting the same amount of power you'd have wasted by using the same antenna in transmission!

Also, with a low-efficiency antenna as a receiver, you'll have a smaller S/N ratio compared to what you'd have with a higher-efficiency antenna.

Just because you're receiving the power that someone else transmitted (i.e. someone else spent to transmit it) shouldn't be a good enough reason to use a low-efficiency antenna to receive it.


texts: Understanding PCIE and FPGA clock "magic"

texts:
I've been trying to understand how PCIE clocking works when it comes to connecting an FPGA to a PCIE slot in a motherboard.

Looking at page 12 of this schematic for exampe:
https://www.xilinx.com/support/documentation/boards_and_kits/xtp067_sp605_schematics.pdf

and following MGTRXP0 pin down to page 16 here:
https://www.xilinx.com/support/documentation/user_guides/ug386.pdf

still leaves me wondering what kind of circuitry is being implemented to allow this FPGA to read TLP's at an incomming bit rate of over 2 Gbs. The only way that makes sense to me goes like this:

A RX buffer sampling at PCIE x1 speed reads a TLP and raises an interrupt.
The FPGA can then read the TLP bit by bit at whatever rate it was designed to.
The FPGA then writes to a TX buffer at whatever rate it was designed to, once the FPGA is done writing, the TX buffer will transmit that TLP at PCIE speed when instructed to.

Is this similar to how things work in reality?

Another related question - What kind of MCUs are involved in the PCIE chain that can transmit and sample data billions of times per second? From my very limited experience with electronics I usually encounter speeds MCUs with speeds of 1-5mhz.

Any pointers to relevant books or any other form of information would be very welcome.


texts: Placing a diode between low and high beam on a motorcycle

texts: I am trying to place a diode between the high beam and low beam on my motorcycle. My headlight is a skull, it has the two eyes as high beam, and the mouth as low beam. the way it is wired, when you hit the high beam the eyes light up, and the low beam the mouth lights up. On high beam , I want them all on, and on low beam only the mouth. the eyes are each 50 watts, and the mouth is 55 watts. talking to the manufacturer, he stated that the eyes are each 4amps, and the mouth is 4.5 amps, giving me a total of 12.5 amps, my question is what diode do I need to perform this task? I know it has to be 12 volts, but that's all I know. Any help would be greatly appreciated. Thank you.


texts: What is the benefit of having dynamic configuration in FPGA PLL?

texts:
With PLL it is possible to generate clock signal at different frequencies and phase values. So far I have seen that these settings are done at design time and do not have to be changed during run time.
When does a need arise to be able to change the PLL settings and run time? PLLs in modern FPGAs are quite complex and have a lot of settings that can be used to configure its behaviour.


texts: Communicate with bluetooth module from Arduino Uno - Take Two

texts:
I have an Arduino Uno. Pins 2 and 3 are connected to pins UART_TX and UART_RX, respectively, on a bluetooth SMD module. I have the following sketch running on the Uno.

#include <NewSoftSerial.h>

NewSoftSerial bluetooth(2, 3);
byte b;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);   // opens serial port, sets data rate to 9600 bps
  Serial.flush();
  bluetooth.begin(9600);
  //enter command mode
  bluetooth.println("$$$");
  Serial.println("setup complete.");
}

void loop() {
  // if theres data from the bluetooth module
  if (bluetooth.available()) {
    //echo it to the serial monitor
    Serial.print("bt module said:");
    Serial.println((char)bluetooth.read(),BYTE);
  }
  //if theres data from the serial monitor
  if (Serial.available()>0) {
    b=Serial.read();
    //echo it back to the serial monitor
    Serial.print("serial said:");

    Serial.println(b,BYTE);
    //send it to the bluetooth module
    bluetooth.print(b,BYTE);
  }
}

I see the following on the serial monitor.

  setup complete.

I expected to see

  setup complete.
  bt module said:C
  bt module said:M
  bt module said:D

Why am I not getting a response from the bluetooth module? Am I using NewSoftSerial incorrectly? Is the bluetooth module wired backwards? Are there examples communicating with a bluetooth module from an Arduino board?


texts: Charge pump to a specific potential somewhere else in the circuit

texts:
Just for context: The original problem I was originally trying to solve was measuring current through a shunt whose voltage potential may be outside the range of my control circuit's supply voltage.

Here, the control circuit on the left runs on 12 V DC, however the potential where I'm trying to measure may be in the range 0 .. 30 V DC. Even if I were to use an amp with rail-to-rail inputs I still wouldn't trust the circuit without any headroom, and also the load voltage (V2) might be less than the minimum supply voltage of the amp.

So first I thought measuring current with a shunt that is at a different potential than the control circuit must be extremely difficult, then I wondered how a multimeter even measures anything - well I suppose the battery doesn't care much what it's absolute potential is, even just connecting the ground of a 9V block to the node between R_shunt and R_load probably would have been enough. But I don't want a battery there, so I thought about how I could somehow move voltage from the control circuit on top of the load circuit.

Regardless of whether the original problem could be solved in a better way, I decided to try this approach for educational reasons. By chance, I read in the datasheet of some power H-bridge IC that it uses a charge pump to drive the high side MOSFETs of the H-bridge because it has a similar problem. The charge pump inspired this kind-of DC-DC-converter-like thing:

V1: Always 12VDC, used to charge the capacitor
V2: 50% PWM pulse (0V .. 12V); periodically switches the transistors on. When high, the transistors connect the capacitor to the control circuit, where it will be charged.
V4: Load supply (0 .. 30 V)

The idea is that we charge the capactior with the control circuit, and then cut all connections to the control circuit, somehow connect the ground of the capacitor to the target potential, and let it discharge. The unpleasant part is connecting it to the target potential, which is done with a 100k resistor. That means a small current flows from the load circuit to the control circuit while the capacitor is recharging in the control circuit, but it's enough to lift the potential when the control circuit is completely disconnected.

The thing is at this point I'm completely over my head. I haven't found any information on this arrangement (also I don't really know what to google for). From that I assume that other people may have done this before and decided that it's a terrible idea and I'm definitely going to shoot myself in the foot.

Is this a legitimate approach? If not, what is a viable alternative?


texts: Running Washing Machine from an Inverter

texts:
I run the house on a solar power source through a Trace DR2424E 2500 inverter. Everything works great except for the washing machine. I can't get the washing machine to work unless I put heavy load on the inverter, other than that, I get an error on the washing machine.
for example: if i want to start the washing machine, I will have to power on the fredge, TVs and lights. As soon as the washing machin starts, I can turn off other devices and it will keep running.

I tried to play with the search mode option in the inverter, but with no luck.

Additionally, is it ok to have the inverter running 24/7?


texts: Find a microcontroller from its pin layout

texts:
Is there some service where one can search for a microcontroller from its pin layout?
There's a remote control that doesn't work and I would like to find information about its microcontroller. I'm not trying to find a replacement, I want to get more information about it to be able to make proper tests. Actually most likely the resonator is broken but I got interested in the title of this question.
So far I can only get that it's a TSSOP20 package with +V on PIN6, GND on PIN9 and XTAL terminals on PIN7 and PIN8. Possibly it's serial programmed through PIN15, PIN16 and PIN17 (it could be passive configuration pads too) and works with a 4MHz crystal and it's 3.3V tolerant. The other pins are used to read buttons in a digital fashion.
I'm interested not only in information of services available but also on techniques you use to find information about an unknown chip (since some manufacturers rebrands its chips).


texts: Measure DC component in AC+DC mixed signal in flyback configuration with LTC3108

texts:
I wonder how can read Input DC voltage After voltage dropped resistance(R1)

That's because this is Self-Ocillation Flyback converter,
In here, you can see the VIn is Ac voltage,
But I need to know Dc Level in this waveform.

Please tell me about the way to read Dc level


texts:
Usually the data launched at 1st clock edge will be captured at 2nd clock edge. But Is it possible to launch at 1st edge and capture data in same clock edge?

The clock to capture flip flop is delayed by 60ps from the launch flop. The time period be 100ps. And the data path delay is 30ps. Setup and hold is 10ps both.

In this case the launch flop launches data at 0ps, the data come to capture flop after data path delay of 30ps. The 1st clock edge of capture flop occurs at 60ps.

Now data available at D pin of capture flop at 30ps and hence setup timing is met.

And now the next data will be launched by launch flop at 200ps. At 200ps, hold for the capture flop will also be met. So this condition is possible or i am missing out something?

waveform


texts: [Check my homework]Electronics homework - op amp and transistor

texts:
I'm working on my electronics homework and I'm not sure my logic here is correct. The values are as follows:

\$R1 = 10k\Omega\$,

\$R2 = 1k\Omega\$,

\$V_{D} = 0.6V\$,

\$V_{EB} = 0.6V\$,

\$V_{ECS} = 0.2V\$,

\$\beta_{F} = 100\$,

\$V_{R} = -15V\$.

I need to find \$v_{I}(v_{G})\$ and \$i_{C}(v_{G})\$ in the following two cases:

a) D - ON, Q - cutoff,

b) D - OFF, Q - forward active.

a)Since the transistor is in cutoff state in the first case, there is no current through it, therefore \$i_{C} = 0\$. The plus connector of the opamp is grounded, therefore the potential of the minus connector is 0 as well. Now I can write the following equation:

\$\frac{v_{G} - 0}{R_1} = \frac{0-v_{i}}{R_1} \Rightarrow v_{I}(v_{G}) = -v_{G}\$

b)The transistor is in forward active state which means that \$V_{EB} = v_{I} = 0.6V\$.

\$i_{E} = \frac{v_{G} - V{EB}}{2\cdot R_{1}} = \frac{v_{G}}{20k} - 30\mu\$

\$i_{E} = (\beta_{F} + 1)\cdot i_{B} \Rightarrow i_{B} = \frac{i_{E}}{\beta_{F} + 1}\$

\$i_{C} = i_{E} - i_{B} = \frac{v_{G}}{20k} - 30\mu - \frac{v_{G}}{20k \cdot 101} - 0.3\mu = \frac{v_{G}}{20k}\cdot\left(1 - \frac{1}{101} - 30.3\mu\right)\$

Expression in the last bracket is approximately 1, so \$i_{C} = \frac{v_{G}}{20k}\$.

Are there any mistakes?


texts: Thevenin Theorem seems to not work in this 1 bit RAM RC circuit

texts:
I have a problem which consist in 1 bit RAM made of 3 MOSFETs. One of the questions is to calculate the maximum voltage that the memory element can receive. I have obtained the result by inspection (it is 4 Volts) but I'm unable to reach the same by applying the Thevenin Theorem.

My understanding is: I have a circuit made of several resistors and one capacitor (which is the memory element). If the circuit is reduced to a \$ (V_{TH}, R_{TH}) \$ Thevening Equivalent, and given that the capacitor behaves like an open circuit for long periods of time (it's fully charged), I can assume that the maximum voltage the capacitor might have is \$ V_{TH} \$. The problem is that the \$ V_{TH} \$ I find has nothing to do with the expected result (4 Volts).

I want to know what I'm doing wrong and how to solve this problem by applying the Thevenin theorem.

The exercise, along with all my schemas and equations, are below:

In a previous question I have calculated the parasitic resistance and it is \$ R_{PA} = 185.347405560882 \$ TeraOhms.

The question I actually need to answer is:

  Now, suppose the drain of  Q1  is high, and the store line is held at the same voltage as the drain of  Q1 . What is the maximum voltage, in Volts, that the gate of  Q2  can be charged to? Note, this value must be larger than  VOH = 3.5 Volts  to satisfy the static discipline.

Now, my 'Tehevening Equivalent' attempt to find the voltage in Q2 is below:

$$
parallel(R_{1}, R_{2}) = \frac{1.00000000000000}{\frac{1.00000000000000}{R_{1}} + \frac{1.00000000000000}{R_{2}}}
\\
R_{\mathit{TH}} = {\rm parallel}\left(R_{\mathit{PA}}, R_{\mathit{ON}} + {\rm parallel}\left(R_{\mathit{OFF}}, R_{\mathit{PU}}\right)\right)
\\
I_{\mathit{TH}} = \frac{V_{S}}{R_{\mathit{PU}} + {\rm parallel}\left(R_{\mathit{OFF}}, R_{\mathit{ON}} + R_{\mathit{PA}}\right)}
\\
e = -I_{\mathit{TH}} R_{\mathit{PU}} + V_{S}
\\
\mathit{ITH}_{2} = \frac{e}{R_{\mathit{ON}} + R_{\mathit{PA}}}
\\
V_{\mathit{TH}} = -\mathit{ITH}_{2} R_{\mathit{ON}} + e
$$

Or in SageMath/Python:

V_S = 5.
R_ON = 2100
R_OFF = 110e6
R_PU = 10e3
R_PA = 185.347405560882e12

parallel(R1, R2) = 1./(1./R1 + 1./R2)

R_TH = parallel(R_PA, R_ON + parallel(R_OFF, R_PU))

I_TH = V_S / (R_PU + parallel(R_OFF, R_ON + R_PA))
e = V_S - I_TH * R_PU
I_TH2 = e / (R_ON + R_PA)
V_TH = e - I_TH2*R_ON

The final result (V_TH) I get is 4.99954549553765 Volts, and it should be 4 Volts.


texts: Connecting Positive power supply to power plane

texts:
I am making a four layer PCB. The top and bottom layers are signals and the internal layers are power and ground layers.

L1 --- Signal
L2 --- Power
L3 --- Ground
L4 --- Signal

I am using Li-ion battery and then using LDO to convert it to 3V. 3V is then powering the whole circuit. Should layer L2 should be connected to the 3V LDO output or Li-ion battery positive output? Both are a positive supply source, so I am unable to decide whether I should connect LDO 3V output or Li-ion output to the L2 power plane.


texts: BJT differential amplifier: What causes common mode voltage gain?

texts:
In any normal op amp, if it was ideal it would have a gain such that the output voltage would be

However in reality this is not the case as there is a common mode voltage gain and hence in reality the gain is different and the output voltage would be:

If we look at a simple long tail differential amplifier which uses BJTs how could this be explained? On a transistor level how can you show where this comes from?

What actually causes this non ideal behavior of common mode voltage gain ?


texts: How to interface SIM800L to UART on STM32F103

texts: I have problem to interface SIM800L with STM32F103. I just read SIM800L datasheet that UART logic level is on 2.8 V. But the STM32F103,can be operated in 3.3 V. I connected my TX RX pin directly to my MCU. I send AT command but nothing happen. Am I doing something wrong?


texts:
What circuits can be used to provide a voltage supply capable of sinking around 1A of current that will always float 10ish volts below a given supply, that could be from 12 to 200 volts?

I have thought about using negative voltage regulators or buck convertor circuits, but I am unfamiliar with such applications, being more used to absolute offset typologies and positive voltages. I imagine a relative offset will be more challenging to achieve.


texts: I'm trying to design a circuit in Logicworks that uses an op amp, but I can't find any op amps. Is there an op amp in Logicworks? If there isn't one, then what can function like one?


texts: How to use ordinary voltage regulator from a high fault current source?

texts:
My power source is 12v 40amphour(car battery).   The wiring resistance is low so the prospective fault current could be very high . My project needs 12v but only 500 or 1000ma max. My 12v voltage regulator (NTE960) explodes with 40amps, so I must reduce the current (too much current for other components anyway).

What's the best way to reduce the current before it enters the voltage regulator?

Is the best way to put a 10 watt resistor between the voltage regulator and the power source? (ex NTE-10W015)

V=I*R

Where V=12v and R=15Ohms shows that the output will be 800ma and 9.6watts.

I assume a 10 watt resistor supports 10 watts of output (not that its 10 watts input)

What about a diode? Except for zener diodes I can't find a 10 watt diode.

What if I get 14v instead of 12v? Output will then be 13 watts. What will happen to the resistor then?  Should I use a 15 or 25 watt resistor then?


texts: Help identifying LED strip and its connectors

texts:
Some years ago, I was given, what I assume is an LED strip by a friend.
I'm interested in building a "NeoPixel"-like solution for a Pi Pico and hope I can use this strip.
IIUC from trying to discern any details about the strip, it requires 12V DC to the black wire and the other 3 wires correspond to (R)ed, (G)reen and (B)lue.
My questions are:

Can anyone tell me the manufacturer|SKU for this strip?
What is the name of the converter from a wall wart 12V DC to the 4-pin RGB LED power strip?
Where can I pick up these converters?
Can I then safely connect the strip to the (black) power and the RGB wires to Pico outputs?
Would I be better placed just buying a NeoPixel strip from Adafruit?

Thanks!


texts: How do I find the Thevenin voltage and resistance equations of this circuit?

texts: How do I find the Thevenin voltage and resistance equations of this circuit, with respect to the terminals U and G when Rc, Vc, Rt, and Rtrans are given?


texts: How do I control the latch signal for the TLC5958 LED driver?

texts:
I would like to drive 512 RGB LEDs with individually controllable brightness. My plan is to 8-way multiplex them so I would like to use an LED driver that is designed for multiplexing LED displays.

I was looking at the TLC5958 as it hits all my requirements: constant current sink PWM with lots of channels, supports multiplexing with a high refresh rate and relatively efficient data transfer (I would like to refresh the display at 120 Hz and display 30 frames per second of video data) and has functionality to reduce ghosting in multiplexed displays.

Looking at the datasheet and other supporting documents, it looks like controlling this LED driver is a bit different from most that I've seen. Data is sent into a shift register via a data in and clock line (so far so good), however the data is interpreted differently based on what command you send it. Commands are encoded on the number of clock rising edges that the latch signal remains high for before falling (for example, 1 rising edge means store the data from the shift register into the greyscale memory, 5 rising edges means store the data into the function control register, etc). And it appears to require this latch signal to be raised while data is being transferred and lowered when data transfer is complete. Therefore the latch signal must be synchronized with the data transfer clock.

I was hoping to just use an SPI channel on an external microcontroller or SoC to control the TLC5958, however I think the requirements on the latch signal preclude me from doing that easily. I think I can't just use a GPIO for the latch signal because it won't be synchronized with the SPI data clock.

Am I mistaken? What's the most straight forward way to control the TLC5958?


texts: New to EE classes, have an introductory voltage output problem

texts:
sorry if this seems very easy but I am looking for a little help as I have only just begun to learn EE. My homework problem has me create a power supply using a common reference point only a 24 V source. Only resistors are involved. The goal is to have outputs of +12 V, -12 V, and +5 V. In addition, the power source must supply 80 mW. I've got the outputs of -12 V and +12 V figured out, but have been struggling endlessly to get the +5 V output correct (as well as figuring out the 80 mW). The below schematic is what I have so far:

simulate this circuit – Schematic created using CircuitLab

My inclination is to say "divide the 12 V using voltage division," but I haven't figured out how to make it work with the ground. Some advice would be much appreciated. Thank you.


texts: Should I use cascaded regulators, or connect them all to the same input?

texts:
For a particular design, I need to take an unregulated voltage from a battery and regulate 5 different DC voltages from it. What's worse is that I need step-up and step-down converters. What's even worse is that some voltages need more current than others.

Note: To clarify the question, I've given the specific voltages that I need. However, keep in mind that I'm wondering what to do in general, not just this specific case.

The battery voltage is 11.1 V, which drops as it discharges. I need to create:

15 V
12 V
5.5 V
5.0 V
3.3 V

The 12 V level needs to run at least 1 A, and the three lowest need to run about 200 mA each. The 15 V level doesn't use more than 50 mA.

So this is my question: would it be better to go from the battery to 15 V to 12 V to 5.5 V to 5.0 V to 3.3 V, or would it be better to just connect all 5 regulators directly to the battery?


texts: PIC32 data storage in flash change / corrupt

texts:
I have some random issue with data saved in flash on PIC32MX470F512L.

Since there is no EEPROM, part of the flash storage is used to save configuration and some statistics (ie.: reboots reason, errors on serial communication, etc).

Over about 50+ units, randomly part of configuration change, the cause is not found but some hypothesis for the moment :

No capacitor on MCLR
Reading of the configuration in flash before VDD fully stabilized
Power off during flash write

I am sure there is not enought writes to go beyond limit, somewhere between 1 and 25 writes per day.

Yet I've not been able to reproduce the issue periodically.

Here are some relevant parts of the code...

Main

int main()
{
    /* Variables defines */

    //Configure l'horloge systeme
    SYSTEMConfig(GetSystemClock(),SYS_CFG_WAIT_STATES | SYS_CFG_PCACHE);

    //Active le watchdog (periode de timeout de 8sec)
    EnableWDT();

    //Initialisation de la configuration non volatile
    config_init();

    /* Other init stuff */

    //Gestion des statistiques de demarrage.
    if(mGetWDTOFlag())
    {      //Reset par watchdog
        mClearWDTOFlag();
        g_stConfiguration.stats[STAT_REBOOT_WATCHDOG]++;
        config_saveStats();
    }
    else if(mGetPORFlag())
    {  //Reset par switch
        mClearPORFlag();
        g_stConfiguration.stats[STAT_REBOOT_NO_POWER]++;
        config_saveStats();
    }
    else if(mGetBORFlag())
    {  //Reset par mauvaise alimentation
        mClearBORFlag();
        g_stConfiguration.stats[STAT_REBOOT_NO_POWER]++;
        config_saveStats();
    }
    else if(mGetMCLRFlag())
    { //Reset par mclr (bouton reset)
        mClearMCLRFlag();
        g_stConfiguration.stats[STAT_REBOOT_OTHER]++;
        config_saveStats();
    }
    else if(mGetSWRFlag())
    {  //Reset software (non implemente encore)
        mClearSWRFlag();
        g_stConfiguration.stats[STAT_REBOOT_OTHER]++;
        config_saveStats();
    }

    /* Going to main loop */
}

Flash utility functions

void config_init() {
    // Lecture de la configuration presente en memoire
    nvm_lireConfig(&g_stConfiguration,NVM_PAGE_CONFIG);

    /*
     * Si le numero d'ordinateur est zero c'est parce qu'il n'y a rien dans la
    * flash, on va charger les valeurs par defaut.
    */
    if(g_stConfiguration.numero_ordinateur == 0)
    {
        config_defaut(&g_stConfiguration);
        nvm_ecrireConfig(&g_stConfiguration,NVM_PAGE_CONFIG);
        nvm_ecrireConfig(&g_stConfiguration,NVM_PAGE_CFG_BKP);
    }
}

void config_saveStats()
{
    nvm_ecrireConfig(&g_stConfiguration,NVM_PAGE_CONFIG);
}

void nvm_lireConfig(void *dataAdr, int pageNumber) {
    memcpy(dataAdr,(void*)eedata_addr[pageNumber],sizeof(ComputerConfiguration));
}

int nvm_ecrireConfig(void * dataAdr, int pageNumber) {
    int pagebuff[1024]; //Buffer d'une page, necessaire pour la fonction NVProgram

    // On efface la page avant d'ecrire dedans
    if(nvm_effacer(pageNumber) == NVM_SUCCESS) {
        // Ecriture des donnees dans la NVM
        if(NVMProgram((void*)eedata_addr[pageNumber],dataAdr,sizeof(ComputerConfiguration),(void*)pagebuff) == 0) {
            // Verification des donnees ecrits
            if(nvm_verifier(dataAdr,pageNumber) == NVM_SUCCESS) {
                return NVM_SUCCESS;
            } else {
                return NVM_VERIFY_ERROR;
            }
        } else {
            return NVM_WRITE_ERROR;
        }
    } else {
        return NVM_ERASE_ERROR;
    }
}

int nvm_effacer(int pageNumber) {
    if(pageNumber < NVM_NUM_PAGES) {
        if(NVMErasePage((void*) eedata_addr[pageNumber]) == 0) {
            return NVM_SUCCESS;
        } else {
            return NVM_ERASE_ERROR;
        }
    } else {
        return NVM_PAGE_OUT_OF_RANGE;
    }
}


texts: I understand division in binary but applying it in a circuit is confusing. so far i have built adders/subtraction and multiplication circuits. i think i should have extra bits for radix bits. simple schematic that give me a kick about division logic circuit perhaps.


texts: Changing a power supply from dc output to ac output

texts: I've read an article on changing a 12 v ac-dc power supply to 9v ac-ac by just tapping the transformer output directly, bypassing diodes and capacitor.  This only applies to older type ac power adaptors that have a large, heavy transformer.  Does this modification change any aspects of the amperage?  I'm trying to modify a 12v 1.6 amp dc output power supply for a device requiring 9v 2.1 amp ac.  I also wanted to find out if amperage ratings for devices have any safety factor figured in, allowing for any lower amp tolerance.  Thanks!