texts: Full-wave rectified sine wave representation?

texts:
Let us suppose I have an input voltage \$V=V_0 \sin(\omega t)\$ connected to a full-wave rectifier bridge which changes the voltage to \$V=V_0|\sin(\omega t)|\$. Now, if I want to work out the voltage drops, currents and the impedances in the following circuit, how do I represent the rectified waveform in terms of a superposition of elementary sinusoidal signals?

simulate this circuit – Schematic created using CircuitLab

I tried to use wolframalpha to give me a Fourier decomposition of the wave (which I don't know how to compute analytically). But now I do not know how to find the final output voltage across the load resistor. I know the basic methods of finding impedances of capacitors and resistors, but since there is a superposition of many waves here,I am unable to find the answer. The impedance of capacitor is \$\frac{1}{i\omega C}\$, I don't know the ω here.


texts: What will happen if I solder two 120mm 12v computer fans to one 12v phone charger?

texts:
After enough YouTubing and self educating, I decided to take the plunge and purchase a soldering iron.  It took me two attempts (apparently the cable of the charger that has the grey dashes on it is the hot side and not the ground), but I managed to solder an old 12v phone charger to a 120mm case fan used for a computer.  Everything wrapped up and it appears to work okay in my homemade keezer.  Unfortunately though, as large as my keezer is (5 taps worth), one 120mm fan may not be enough to circulate the cold air throughout the entire chest freezer.  My thoughts were to add a second fan, but don't want to have two power cables leading out if possible.

What would happen if I soldered both fans to the same, single 12v phone charger?  What about more than two?  Would the fans run at the same RPM or would they run at a lesser speed?  Are there any issues with this I may encounter past potentially reduced RPMs if that is in fact the result?  Should I just plan to use separate identical power sources to power however many fans necessary?  Thanks for the help!


texts:
Anybody has an idea of what the GE3 and RE3 stand for on Vishay mosfets order code?, for example the SIR870ADP can be ordered as either SIR870ADP-T1-GE3 or SIR870ADP-T1-RE3

The datasheet only mentions SiR870ADP-T1-GE3 to be "Lead (Pb)-free and Halogen-free" and I cannot find anywhere what the T1-RE3 ordering code means

Product page: http://www.vishay.com/product?docid=63657&tab=quality

Datasheet: http://www.vishay.com/docs/63657/sir870adp.pdf


texts: Cannot use HardwareSerial pointers or references in my Lib for Arduino AVR?

texts:
I wrote a wrapper class for a serial lcd screen for 4dulcd - and i want to be able to pass which serial i am using to communicate with it

I have these in my code
myClass.h

#include <HardwareSerial.h>

public:
uint8_t Init(long BaudRate, HardwareSerial *serial);

private:
HardwareSerial *_HardSerial;

in myClass.cpp

uint8_t myClass::Init(long BaudRate, HardwareSerial *serial){
_HardSerial(serial);
...
}

In my sketch

#include <myClass.h>
myClass lcd;

void setup()
{
  Serial1.begin(9600);  // <- Error here?!
  //lcd.Init(115000,&Serial1);
...

So the error is

  sketch_sep17a.cpp: In function 'void setup()': sketch_sep17a:16:
  error: 'Serial1' was not declared in this scope

If i remove the myClass.h header than the Serial1 works... i Include it and it throws this error that makes no sense to-

I tried to include the hardwareserial in my sketch and make an instance of it but it requires all sorts of construction properties that i have no idea what they mean. And i would not even want to release my lib to do this as it is inconvenient for the normal end user.

I tried both references and pointers- same error.

Can any body help?


texts:
I did a standard inverting operational amplifier (UA741), with Rin = 6k and Rf = 1k.

I have a lab power supply, with 30V of difference for the amplifier.
I don't understand why this doesn't work, it should be Vout = -Vin/6 but I measure Vin = Vout = V-(AO).
I put Vin between 0 and 10V for instance, static, and voltage measurements are made with a standard voltmeter. I tried with several new op amps and it's the same problem.


texts: What is needed to go from single Ethernet to many?

texts:
I have an embedded Linux system with a single Ethernet port, but I need to go to many ports. It is obvious I need to add magnetics and ports. The trickier parts follow.

My processor has an on-board MAC and I'm using a single-driver PHY. Do I only need a new PHY with more drivers? Is it possible to use multiple PHYs on the same MAC? Do I need a MAC for each port?


texts:
I'm looking at using a LCD panel (Chimei Innolux HJ0801A-01E) that is exactly the right physical size and resolution for a project - I'll drive it with a FPGA; I have looked for a while and I don't think there's a better fit. Discontinued but there are more around than I will ever need. Trouble is it wants a lot of different power supplies. To the point where getting the power right is turning into the hardest part of the project.
Requirements:

VCC: 3.3v 60mA
AVDD: 10v 40mA
VGH: 18.9v 1mA
VGL: -7.8v 1mA
LVDS: 2.5v 1mA (?)
LED backlight 9.3v 220mA

The LCD also shows power on and power off sequences. For this reason I'm thinking the FPGA should switch each of these supplies on or off in the correct sequence using enable pins.
There's a power supply capable of 5V, 12V and -12V close by with plenty of capacity for the above. Board space is not important.
I've found LDO regulators that are cheap and adjustable and have enable pins like Microchip MIC5377 (positive) and Texas Instruments TPS72301 (negative). Is there any reason not to use one per required voltage with suitable external components? It seems obvious but the PCB that these displays are often bundled with ("PCB800099") have a bit more complexity and if it could be done cheaper they would have. Maybe the Realtek chip that does VGA/Composite/HDMI/LVDS makes all that necessary; not sure.


texts: In a parallel plate capacitor, how does placing a metal in between the plates reduce the capacitance?

texts:
This source claims that putting a metal plate in between the capacitor plates greatly reduces the capacitance. How is this possible?

Two equal capacitances in series decreases the capacitance by half, but the distance is also decreased by half, so the overall capacitance must not change right?


texts: Memory (RAM) of computers after shut down

texts: After computer shuts down, is it possible to retrieve data in RAM? I heard that police was able to do that... so I felt that was somehow weird..


texts:
Lets say I have -2 dBμA/m as a limit.

How do I convert the magnetic field strength in A/m to dBμA/m? Is it as follows?

$$20\cdot \log(\frac{ |H| }{10^{-6}})$$

Thank you!


texts: What are the differences between USB and RS232?

texts:
Can someone tell me why people use either USB or RS232.  They are both serial ports, right?  And I understand that USB is much faster (especially USB3.0) but if people wanted too I'm sure they could make a successor to RS232 that is just as fast.

So, what are the advantages and disadvantages to both?


texts:
My question has to do with the rule of thumb we generally use when dealing with transmission lines.

We say that if the length of the line is 10% or less of the wavelength, we could neglect the effects of the transmission lines—and that makes sense if we look at from the perspective of the time delay it takes the wave to travel along a short vs a long line.

But when looking at it from the perspective of the input impedance equation, the 10% rule of thumb doesn't always hold. For example,

$$ Z_{in}=Z_o\dfrac{Z_L+jZ_o\tan{(\frac{2\pi}{\lambda}L})}{Z_o+jZ_L\tan{(\frac{2\pi}{\lambda}L})}$$

For some values of \$Z_o\$, and \$Z_L\$, (with \$L=0.1\lambda\$), you don't necessarily get an input impedance close to the value of the load one (which I think would mean we could ignore that the TL is even there).

Take for example, \$Z_o=50\$, and \$Z_L=300\$, with \$L=0.1\lambda\$, then \$Z_{in}=23+j64\$. The line does transform the impedance seen by the source even though it is "short" as per 10% the rule of thumb.

Also, even if the line effects were negligible somehow, the reflection coefficient would still be nonzero since it's defined by:

$$\Gamma =\dfrac{Z_L-Z_o}{Z_L+Z_o}$$

What would be the effect of having a nonzero \$\Gamma\$ even when the line effects are considered negligible? (Hopefully this makes sense!)

What am I missing here?

Thanks


texts:
I've just received a Christmas card with a tiny lcd that played a movie when opened. Sweet! Obviously, my first impulse was - time to load my own video! I hooked it up via a tiny usb port I found and I managed to open the video on it - it was titled "SOMETHING-MPEGx17.avi". Now, I tried loading an avi and then an mp4 onto it - neither played correctly. Does anyone have an idea of what to try next? Is there some way to archive an mp4 into an avi or something?

Thanks!

PS: Not sure if this is the right stackexchange site for this... Is it?


texts: Can I use a 5V phone charger to run a device which expects 3.7V battery power?

texts:
I have an old mp3 player which originally ran from a 3.7V LiPo battery. It could be charged from USB using a mini-usb connector. The device goes into charging mode when power is present at the usb charging port, but will not operate in playback mode without voltage at the battery terminals. The battery is long dead and I removed it and soldered a connector to the battery input of the circuit. Using an adjustable regulated supply I can run the device by supplying 4.25V at where the battery used to be (the battery indicator shows "full" at 4.2V and "low" at 3.6V) or from 3 AA batteries, however I would need a smaller wall-plugged power source for practical (stationary) use. I tested the device using a smartphone charger and ran it briefly (2 minutes) with no apparent problems. The measuered voltage was 4.85V. I would need some advice on the following:

What (if any) problems could arise from running this device at 4.8-5V? The device expects around 4.2-4.3V (voltage of a fully charged LiPo), so this would be 0.6-0.8V higher. Short test operation (about 2 min) went fine, could there be problems if playing back music for hours?
Is there any way to diagnose such problems? Perhaps by measuring temperature on the surface of the IC?
What are the possible consequences? Besides device failure, could this also cause a fire hazard?

Here is an image of the player's internals:

The square IC is marked M7103A-A1, however I could not find a datasheet for it. The rectangular IC's markings are unreadable. The cable in the lower right corner is where the battery used to be. The charging port is on the lower left.


texts: Maximum Symmetrical Swing for BJT Amplifier

texts: I am doing the DC analysis for a BJT amplifier using the 2N3904 transistor in a common emitter configuration.  I am given +Vcc = 18V and need to find Rc to give maximum symmetrical swing.  From my research I see to choose a value for Ic and then find Rc such that Rc = (+Vcc/2)/Ic.  In this way the voltage at the collector i.e. Vc = +Vcc/2.  However, I saw a different design which said to find Rc using Rc = ((+Vcc - V_Re)/2)/Ic where V_Re is chosen as 1V.  The former approach makes more sense to me. Looking for guidance as to which way is better.


texts:
Given the following schematic and told that \$ \beta = 80 \$ and \$ V_A = 100\$. I'd like to try and design the circuit such that the dc voltages at the base and collector are 0.20V and -3V respectively.

To DC the capacitors will appear as shorts and to aid analysis I thought to redraw the circuit as follows

Here one equation is obtained such that \$I_E = I_b + I_c\$

Due to the independent source here I thought to create a supermesh (shown in red and chosen arbitrarily in that direction) to obtain a second equation. I began to sum the voltages in the loop however ran into the problem that there is a dependent current source in that loop now. I'm currently stuck at this step unsure of how that handle that dependent current source in the super mesh.


texts: Creating a custom library part in EagleCAD and avoiding DRC Errors

texts:
I made a custom footprint for an SMD connector I'm using. I wanted to build vias into the footprint for each pad and to connect a trace from each pad to its via. The reason I want to do this is so that I don't need to re-do that routing effort in every component that I place (there are a bunch), and since I know I want to route the signals from the connector on a buried layer. The footprint looks like this:

When I defined the device that uses the footprint, I simply did not "connect" the SMD pads and associated the schematic signal pins with the aforementioned vias.

I made the library part without a problem, but now that I'm going to use it, I am getting lots and lots of DRC errors. These are all related to Clearance between vias, traces, and SMD pads in the library component, and Overlap between my vias and pads and the library traces, without even routing anything. Furthermore, when I actually do route a signal to one of the vias by way of the SMD pad, I get Overlap errors where my trace runs through the SMD pad to get to the library connected via, as shown in the following snippet:

As you can see, I've "approved" 720 DRC errors in my layout that are associated only with the bare library parts. So my question is, how do I define my library part correctly so as to avoid these fictional DRC errors?


texts: What is the C-value on rechargable batteries?

texts:
On rechargable batteries, I found a specification which said something like "15 C". Up to now, I thought it would mean "15 cells". But when I saw this battery: I was sure it couldn't be the amount of cells because it is so small. :D

On another forum, I they said it is some kind of factor that says how much current it can provide. I find that rather unclear. So what does "15 C" mean?

Thank you in advance!


texts: How often should the CMPS11 be calibrated?

texts: I have a project with arduino and the magnetometer CMPS11. I wanted to know how often the CMPS11 should be calibrated using this procedure: https://www.robot-electronics.co.uk/htm/cmps11i2c.htm


texts: Power sequencing of simple peripheral ICs for ADC/GPIO with an MCU

texts:
Imagine I have the following scenario: Having a +5V rail powering an MCU and several other peripheral ICs, let's assume in this case a voltage reference (for example 4096mV). The output of this voltage reference is further assumed to be connected to an ADC pin of the MCU. (The same should then apply to a digital signal connected to a GPIO pin)

Now, the datasheet of the MCU states VCC +0.3V or 6V, whatever is lower as the absolute maximum rating on any of its pins. During startup, is it thus necessary to employ power sequencing in order to guarantee that the voltage reference doesn't output any voltage greater than 0.3V before the MCU is fully powered up or is it common practice to just connect both to the same power rail? (Even though the MCU might take longer to power up)


texts:
I know how to reverse a single phase induction motor.
I also try to understand it using this link. But, I can't understand how to reverse the motor of fallowing wiring diagram. In this diagram, RED and BLUE terminals connected to TRIAC separately.

How this motor start,stop,and change direction according to this diagram?
How about internal connection to the winding of this motor?


texts: Exactly what type of resistor is being referred to in this diagram?

texts:
I'm trying to control an RGB LED strip using a NodeMCU. I have been following the guide linked here. However, the diagram included in the diagram is rather unclear, especially for someone like myself who is new to electronics. This is the diagram:

All I can make out from the picture is "500 Ω". However, when googling for the resistor, I am unable to find exactly what I need. For example, on this AliExpress listing, I am unable to find any mention of "Ohms" and just get given an option of multiple "...R". "...K" "...M".

I would really appreciate it if someone could point me in the right direction as I am new to electronics and have found myself stumped by this relatively basic issue.

Thank you in advance for any help.

P.S. I am aware that the method used to step down the 12v to 5v shown in the diagram can be problematic and I am instead going to use a 12v - 5v car charger.


texts: Is there a way to proof that you don't see the cut-off frequency in the plot?

texts:
In my previous question, I've asked something about acut-off frequency (Finding the cut-off frequency).

But in my plot I don't see those, I see the one that I find when I pick the zero and the pole ones. Is there a way to proof that we don't have a cut-off frequency in my question?

Thanks in advance


texts:
I am trying to solve question 11.10 which is taken from 2001 GATE IN paper.

So I think the answer is (a) because the input buffer which faces the analog input needs a higher slew rate in order to have a high bandwidth and acquisition time. While bias current St the output buffer will cause the hold capacitor to leak faster, so that needs to be minimised. Am I missing any other reason? I'd appreciate an detailed explanation on how slew rate affects the performance of this circuit.


texts: BigTreeTech SKR 1.3 (LPC1768), mbed examples not working

texts:
I have a Chinese LPC1768-based board I used to control with Marlin firmware, and recently I started to want to program it my own way instead.

So, I was successful with PlatformIO and Marlin's custom library they have extracted (Arduino-like): https://github.com/p3p/pio-nxplpc-arduino-lpc176x. I am able to blink whatever pin I want.

But, when I try to move to standard Mbed OS/baremetal examples e.g. https://github.com/ARMmbed/mbed-os-example-blinky-baremetal and compile it either via PlatformIO or the online compiler, uploaded firmware does not function. I am sure the bootloader writes the binary to the flash memory, but nothing happens, no signs of life.

So, the question is: am I wrong supposing that any LPC1768-based chip is the same as a chip-based development board? Any other suggestions? Thanks.


texts: Design approach for small, portable non-contact thermal measurements

texts:
I'm looking for ideas and suggestions for putting together a small, non-contact thermal measuring device for finding hot spots on a circuit board.  It needs to be small enough that I can toss it into my tool bag.

I currently use several techniques for finding hot spots on circuit boards.  The most obvious technique is to simply slowly wave the back of your hand over the board - this finds significantly-hot areas easily.  But this isn't necessarily a pin-point detector.  It does have the advantages of being both free and always accessible, though.

I've also got a variety of temperature-measurement devices - these range from contact devices using a thermocouple or thermistor.  In this case, though, I'm looking for non-contact temperature measurement.  The equipment being debugged runs at high-voltage and stores significant amounts of energy.

My non-contact options are also several.  I've got a couple of passive IR measuring devices: an older Fluke unit that uses a DMM for display, a couple of different passive IR units with built-in display, and a relatively-inexpensive FLIR thermal imager.  The problem with all of these devices is size - they take up too much space in my tool bag.

Another technique that I use when locating hot devices on a PCB is to simply flood the area with Isopropyl Alcohol (IPA) and see what components evaporate the alcohol the quickest.  Same problem with portability, though.

Ideally, this device would use something other than a meter for user feedback.

One of the most useful pieces of test equipment that I have is something called a "Leak Seeker" - this is essentially an auto-ranging and auto-nulling milli-ohmmeter that uses sound for user feedback.  It is used to locate short circuits on circuit boards and has the compelling feature that you don't have to look at a display when using it - simply move the test probe to various nodes on the circuit board and listen for changes in tone pitch.

I want to do something similar with this device.  It would always be indicating the change in temperature from some arbitrary reference temperature.  One approach would be to simply store the current temperature when the device is powered ON and use a tone to indicate temperature changes relative to the reference temperature.

But that's about as far as I've gotten.

The initial stumbling block is a choice of sensor.  I don't work with IR sensors and am not sure what I should be looking for when I begin my search for suitable devices.

What sensor can I use to make a small non-contact thermal measurement device?

update:

I got an email from someone pointing me to exactly what I'm looking for on Kickstarter.  KickStarter DeltaK Temperature Indicator

Although this device is pretty much what I'm looking for, I'm still wanting to see what I might come up with myself.

My original question still stands: what particular sensor should I be looking for?


texts:
Below is a circuit used to control duty cycle in SMPS, and I have some question about this design:

Why the designer has connected the output of the error amplifier (Type 3 in this circuit) to the positive pin of comparator U5 through a volage controlled current source, rather than connecting it directly.
What is the usefulness of  the VPWL resistor R7 (Selected in blue in the schematic) to this modulator?

The specifications of this VPWL resistor are shown below:


texts:
I have two same sized DC brushed motors found in different variants of an appliance of the same brand. They are possibly equivalent, but they have different labels.

One is labelled with:

(Johnson Electric logo)
31348
3K3861

The other is labelled with:

3501-0011-01  REV C
CIM-2450-1
24 VDC  0.9 A
50 RPM /15 LB-IN  9-95

The diameter of the motors are 27.5mm, and length of the motor bodies is 32.5mm.

What does the last line, beginning with "50 RPM" mean?  Surely it doesn't simply mean the nominal speed, since 50 RPM is way too slow. Does it have something to do with the concept of "motor regulation"?  This online catalog meantions motor regulation in units that I am not sure about, e.g. on page 50, for motor model HC313G-001, it says Motor Regulations: 304.857 Rpm/m-Nm . Huh, is that rpm per millinewton-metre?


texts:
I’m making an automotive circuit using a third party flasher unit such as this one.
I feel these units can be a source of failure so I want to be able to remove and replace a faulty unit a few years down the line if necessary.
Do they follow some kind of standards with a possibility of a PCB mount socket to mount it? How would you mount these on a PCB?


texts:
I have a device that requires 1.21 Gigawatts over one second to fully activate.  Upon activation the device is disconnected automatically. The device can accept the power at any voltage, and will simply present itself as a load that will consume the required power in one second regardless of the source voltage.

I have an energy source, essentially modeled as a capacitor, with an effective capacitance of 159µF.

Assuming I charge this energy source to 7.69 x 10^15 Volts, and there are negligible losses between the power source and device, how many device activations can I achieve before I must recharge it?


texts: How do I calculate voltage on a multi-powered DC circuit where all ends go to ground?

texts:
I'm writing software that will calculate the correct voltage on each component, given the state that the DC system is currently in (ex. what power sources are on, what relays are open, fuses popped, etc.).

As I begin to learn about the differences in calculating voltage between series circuits, and parallel circuits, I've yet to find an example where the output of a power source doesn't lead back into the same source.  In my case, they all go to ground.  If this is a compound circuit (both series and parallel), I would have to use Kirchhoff's circuit laws to solve it.

I am having difficulties understanding the voltage flow, because I have no numbers to go by.  Everything will have a resistance, and I'll know the voltages of the batteries/generators, but I have nothing to confirm my assumptions about how voltage will split and degrade, and what will happen when multiple power sources are on.

So, What kind of circuit is this?
Series? Parallel? Compound?

There is a split at the Battery Bus, but due to the diodes,
there will never be a complete loop back to where they split.
I suppose I may need to run the following equation on the three fuses after the battery bus?

When resistors are in parallel:
Rtotal = 1/(1/R1 + 1/R2 + 1/R3 ... + 1/Rn)

and run the series calculation for the rest of them to understand the voltage split at the battery bus?

When resistors are in series:
Rtotal = R1 + R2 + R3 ... + Rn

Same idea with the fuses on the Main buses in the distribution boxes?

How is voltage affected when multiple power sources are on?
I'm not really sure how to handle the calculations when say, both generators are on, and the battery is on:

Does the voltage combine?  Does this highest voltage win?

Could someone explain the flow of voltage through this system and how one would be able to calculate it based on the resistance?

Currently I am running a depth first algorithm from each active power source and collecting all paths that go to ground.  I then calculate the total resistance of each one of these paths,  and then use Ohms law to give each one of them a voltage.  I am under the impression that this would only give correct results if the paths were all in series, and I'm not sure that is the case, as there are multiple splits everywhere a fuse appears.


texts:
I have some accelerometer vibration sensors that pass into a cabinet. They use BNC type bulkheads.
Several of the bulkheads got damaged. The original bulkheads are 50 ohm and the coax cables on either side are also 50 ohm. I can only readily get 75 ohm replacements. The signal coming from the accelerometer is less than 2 kHz.
What is the effect of this mismatch?
My thought is that, because the signal is solidly below Radio Frequencies, the coax should behave as wire and not as a transmission line. Because of this, the mismatch is irrelevant.


texts: Hypothetically, 6 or more phase line with same mechanical energy?

texts:
So I don't understand a concept of mechanical to electrical energy conversion.

Let's assume I have a 3-phase generator and need X amount of mechanical power in order to get 200 Volts Phase-Neutral.
Now suppose I add some windings etc. so that I have a hypothetical 6-phase system. Would I need more mechanical energy in order to get 200 V for each phase, or can I get it by same amount X? So basically, if I have more phases do I need more mechanical power?


texts: Please identify these capacitors and values

texts: I'm tracing a circuit. What kind of capacitors are these yellow things? The upper one has markings of "105V 212K1", what does 212K1 stand for?  The lower one has markings of "335V 136K4", what does 136K4 stand for?


texts: Do flat flexible connectors (FFC) couplers exist? (i.e. I don't want to use a cable)

texts:
I'm working on an electronic design where I have a motherboard that allows daughter boards to connect to it. The motherboard and daughter boards should be parallel to one another.

Because my design must be minimally flat (~0.25"), I'm having a difficult time finding a correct connector type. The connector I'm looking for must have 9 (10 is okay) conductors. The width of this connector is ideally less than an inch.

I have stumbled across flat flex connector (FFCs) and am genuinely interested. This would add the benefit of allowing the daughter boards to extend a distance past the board if I decide to use an flat flex cable. This is very useful in my application.

However, there times where I may simply want to connect the daughter board as close as possible to the motherboard. In this case, I would not want to use a cable, but I would rather user a rigid coupler.

Do they make couplers for FFCs such that I can connect to FFC closely together?

Thanks!


texts: How are touch interfaces developed and tested industrially?

texts:
Touch interfaces are omnipresent (mobile phones, wearables, cars, ...). I'm very interested in understanding how those touch sensors are developed, validated, and tested industrially.
Is there a "reference finger" that is used in the production line? Or every single device is tested by a human? How do we take care of the different skins and environmental conditions around the globe? Which figures (ex. SNR) are relevant to compare different solutions?


texts: How do I find op amp specifications regarding voltage limits?

texts:
This question is perhaps a bit unusual and is about how to read/interpret specifications.  I have been doing some testing with a common difference amp (LM324) and have also used LTSpice to double check that my actual breadboarded results are what the simulation expects.  The testing I have been doing is to measure the effect of changing Vcc on the value of Vout.
I am comparing 2 input voltages, say 29V and 26V and expect Vout to be 3V (I am using a unity gain configuration with the op amp).  The power for the op amp is varied from 27V down to zero and what I see is that as the voltage gets to around 14-15V, the Vout drops from a steady 3V to below 1V.  The same holds true if my input voltages are 26V and 23V so I'm clearly hitting some limiting value of the op amp.
My question is this.  Where in the LM324 documentation can I find the details that explain this behaviour and how can I use this to predict the behaviour before I start building the circuit?  I'm guessing it's something to do with common rail details, but this is only a guess.
My motivation is to find out what is the lowest Vcc I can drive my LM324 with if I am measuring a whole range of different input voltages from 28V down to 0V.

As per suggestion, I have now added a screenshot showing the circuit and the test results in LTSpice.

Thanks for your guidance.
Mike


texts:
I have been wondering for a while. With cheaper LDO regulators I often see them advertise that you can use a ceramic output capacitor. In the datasheet examples they use them. But then they say things like "ESR for output capacitor should be between 15mOhm and 200mOhm. I understand there is some small resistance added by the trace to the capacitor but often it is theoretically < 1mOhm based on trace width and length thickness. I have used regulators like this and know it works but why would the manufacturer spec a minimum ESR?

Also in case people misunderstand, I know the ESR is required for feedback loop stability, I'm asking why a manufacture puts what I feel is contradicting information in their datasheet.

Below is an example of what i mean, it is from AP7311. The datasheet can be found here: Datasheet


texts:
What is the proper procedure to measure RMS noise with an oscilloscope?

I have 2 standard resistors, 1k and 100k and a 1.5GHz BW, 5GSa/s Keysight DSO. I have a probe which offers 1:1 (1MOhm//100pF) and 10:1 (10MOhm//15pF) ratios.

I use AC coupling, 1:1 probe and "AC RMS - Full Scale" measurement - which 1mV/div and 100ms/div.

I measure 340uVrms for 1k and 940uVrms for 100k (just clipping the resistor between the probe).

However, I cannot reproduce this result using equations. Three attempts:

The resistor is in parallel with the probe which is 1MOhm and 100pF for 1x. Hence the bandwidth will be 1MOhm//R//1pF ~ 1/(2*pi*RC). Since the total integrated noise is given by 4kTRB = 4kTR/(2*piRC) = 2kT/(piC) = 2/pi kT/C the result should be independent of the resistor 5.1363uVrms. This is far off from the numbers above but even worse - the numbers above are different
I assume the bandwidth limitation comes from the probe itself which is 6MHz for 1x. The result would be sqrt(4*kT*100e3*6e6)=100uVrms for 100k and 10uVrms for 1k. Again, both far off.
I assume the bandwidth is limited by the bandwidth spec of the scope which is 1.5 GHz. This gives 157.68uVrms for 1k and 1.5768mVrms for 100k.

Again, not consistent.

How do I measure noise with an oscilloscope?


texts: How to measure external voltage differential with single ended ADC?

texts:
I would like to measure voltages from external circuits with the single ended ADC from an Atmega324.

The plan is to power the Atmega324 with 3.3V and use a 1.024 or 2.048 voltage reference. The voltages to be measured are 0...5V and 0...24V, DC with 1kSPS. In the end, I want to utilize all eight ADC Inputs of the Atmega while measuring all of them simultaniously, so using differential mode of the Atmega wouldn't work, at least from my understanding, since they only work against specific channels,like AIN0...7 against AIN1 and AIN0...7 against AIN2.
Instead of measuring all voltages in reference to the ADC circuits GND, I'd like to be able to use it more like a voltage meter.

The external circuit to be measured could, as a simple example, look like this:

simulate this circuit – Schematic created using CircuitLab

In order to measure the voltages, I had to connect the probes like this:

simulate this circuit

Here are the things that bug me:

If I use the ADC as single ended, like in the schematic, wouldn't I short out R2 via the GND connection from Probe2 to the ADC and back to Probe4?
According to the datasheet, "The ADC is optimized for analog signals with an output impedance of approximately 10 kΩ or less.". That means the voltage divider and the impedance i want to measure combined had to be below that. So the voltage divider would heavily influence the circuit I want to measure, depending of its nature.

Now I'd like to ask for tips on how to tackle the issues I see.
Regarding issue 2, the resistor impedance, I read that you could create the voltage divider with high resistance values, in the range of a few MegOhm and either
a) add a ~100nF capacitor next to the lower resistor (R2/R4 of the second schematic) in order to supply the internal S/H capacitor with that.
or b) use a OPAmp in a buffer configuration (one that can handle the high inputvoltage relative to GND for measuring the 24V)

I am not sure about issue 1. Would a differential ADC be able to measure the voltages properly without a GND connection? But then I would need an external ADC chip that offers 8 differential inputs.
A buffer opamp would have to be isolated internally, or you have the connected GND again. Since else the opamp wouldn't work, without current going into it.

What would be a good solution to this problem?


texts: Is a battery's internal resistance a function of integrated current over time?

texts:
I've got a question regarding the internal resistance of a CR2032 coin cell. Here's some background info on the project I'm working on:

I'm working on an electronics project in which I hope to have battery powered, more specifically I would like it to be powered with a CR2032 coin cell battery (https://na.industrial.panasonic.com/sites/default/pidsa/files/crseries_datasheets_merged.pdf). However, I've also decided to be open to other coin cells that are more appropriate for my application.

After a few early failed attempts to power my design, I decided to do a little more research into the characteristics of coin cells. From my research, I discovered that the rated coin cell capacity is only valid for the continuous drain rating which is typically low current draw ( < 0.25mA). The reason that this rating is so low is due to the fact that coin cells are not ideal voltage sources (duh), but instead they have a relatively high internal resistance. So when high current is drawn from the coin cell, this leads to a high voltage drop across the internal resistance thus reducing the available voltage across the coin cell terminals.

Furthermore, I've come across design recommendations that suggest putting a capacitor in parallel with the coin cell if your load can be periodically (pulsed) powered, this seemed to work very well. This setup is intended to allow for slow current draw into the capacitor in between power pulses, and then have the capacitor be the primary power supply during high current demands.

However, my design is still not perfect. Here are my problems:

Initially when I was powering my design without a parallel capacitor, the board would stay powered for about 3 minutes before it died. My initial thought was that I was drawing too much power from the battery and had completely drained it. However, I realized that I could wait 10 minutes, and then the coin cell would be able to provide enough power until the board died again after 3 minutes of operation. From this I concluded that I had not used all of the battery's capacity, rather I was just drawing too much power which temporarily reduced the coin cell terminal voltage.

Question: Why is this happening? I theorize that it is due to the battery's internal resistance, however, I had the assumption that the battery's internal resistance was constant. The effect I described above seems to suggest that the internal resistance increases as the battery is discharged. And as soon as you stop drawing power and let the coin cell rest, it appears that the internal resistance decreases such that the coin cell is functional again.

After adding the capacitor in parallel with the coin cell and converting my load such that is draws power periodically (pulsated), I was able to improve the lifetime of the design to about 20 minutes. However, the same phenomenon as described previously seemed to happen again. The board died, but as I let the coin cell rest, after about 10 minutes it was able to power the board again for about 20 minutes. This again suggests that the design isn't dying due to expended capacity, but rather the internal resistance is increasing.

So my question: What is this effect? I'm theorizing that the battery's internal resistance must be a function of integrated current such that it increases over time. Also I'm curious as to what is causing this? Is it just from me drawing too much continuous power from the coin cell? Even though I'm using a capacitor and pulsating power, my capacitor must not be taking the full brunt of the power?

Thanks for the help!


texts: Naming convention between two pins Input -> Output

texts:
Is there some naming convention to name a net label (or hierarchical/global label) from an output to an input pin?

E.g. in the example below, for the name SHIFT_REGISTER_1_OUT, I could also use the following names:

SHIFT_REGISTER_2_IN
SHIFT_REGISTER_1_TO_2

Is there some kind of naming convention for such names?


texts: State Equation of negative resistance from current source

texts:
I have to find the state equation from the circuit, the problem is, on the node with red marker. Here is what I've done

  \$u = I_C+I_R\$

  \$u = C\frac{dV}{dt} + \frac{V}{R}\$

and if the value from components is included, then

  \$u = \frac{dV}{dt} - V\$ (because of negative resistance)

is this right? based on the solution given, it should be

  \$u = \frac{dV}{dt} + V\$

is the negative in resistance is ignored?


texts:
I have two CPU fans which have been damaged. In one the wires were separated in the middle, in the other they were separated at the solder contacts. I have very little soldering/wiring experience, how difficult would it be to repair these and what would be the best technique to do so? Standard size fountain pen included for scale. For reference these are Phanteks PH-F140HP fans.

Number 1:

Number 2:


texts: What is the nature and history of UL capacitor recognition?

texts:
First, the background. I've been working on a grid-tied inverter design for some time now. General topology is:

We've just completed UL listing our product under 508c, and the process was quite instructive. UL performs "breakdown of components" tests, which involves placing a dead short across selected components. They do this to any component which, if it failed, would overload another component. In our case, they performed this test across our snubber cap. Since we were listing with a 50kA SCCR, this exposed the diodes and wiring of a 30A unit to the full 50kA. Naturally, they died, rapidly and spectacularly.

Two solutions presented themselves. One, DC fusing. Unfortunately, fuses that can break 850VDC and are rated at 50kA are large, expensive, and have long lead times. We didn't want to condemn our users to buying them with every unit, when all actual installations will have other means of current limiting. The other option was to add a second snubber cap in series with the first one. That way if one fails, the other is still there, and the diodes are not overloaded. This solution was both cheaper and less trouble for the user, so we went with it.

Now there is, in theory, a third way around this. We could use a capacitor recognized by UL as a reenforced component. In that case, they would waive the breakdown test entirely. However, there is no such capacitor! UL recognizes X and Y type capacitors for safety purposes. Those capacitors are recognized only with AC voltage ratings, not DC ratings. (Some have DC ratings, but they are not recognized by UL.) From what we've been told, there is simply no process by which a capacitor can be UL recognized as a reenforced component for DC voltages.

At a seminar last week, on a completely unrelated topic, someone was discussing putting a capacitor between two isolated sections of a circuit. The comment was made that, until the advent of UL-recognized X and Y capacitors, they had to put two capacitors in series to pass UL. (Nice to have some confirmation of our solution!) Now that implies that there was a time before which X and Y capacitors could be UL recognized. Which further implies that at some point, someone made a decision to create a means of such recognition.

I want to know the whys and hows of that change, so that I might better understand a hypothetical context in which UL might decide to create a recognition process for DC capacitors. So what is the history of UL recognition of X and Y type capacitors? How is such a decision made? Under what hypothetical circumstances might UL decide to create a process for recognizing DC bus capacitors?


texts:
How does the tester screwdriver work? If I put the tester screwdriver inside the "hot wire" of an electrical socket, it lits up if I press my finger against the metal cap on top of the screwdriver. This happens also if I stand on a surface of isolating material, such as wood. I read elsewhere that this happens due to stray capacitance formed by the "hot wire", the human body, and the ground. One has

$$ Z = R + \dfrac{1}{j \omega C}  $$

for the impedance, so if C  is high enough, the impedance should be close to r , the "effective resistance" of the formed circuit. Here I get lost; why r  is small enough to cause a current in the range of mA  even if I stand on an isolating surface?

So really what I am asking is how one may represent the system hot wire - screwdriver - human body - wooden floor - building - ground as an electrical circuit, and which parts of the physical system contribute to the resistance, capacitance (and inductance?) and in which proportion, even very approximately.


texts: How do we predict if power loss will increase or decrease in a DC circuit?

texts:
I want to know whether it is possible to predict if power loss will increase or decrease in a circuit with a fixed EMF, a fixed resistor in series and a variable resistor in series.

If we change the variable resistor's resistance, how do we know if power loss over the variable resistor will increase or decrease? This is presuming we already know the values for EMF, the resistance of the fixed resistor and the original power loss before changing the resistance.

For example, if we double resistance, what happens to the power loss of the in the variable resistor?

Furthermore, we can assume no internal resistance.

I think its something related to the maximum power loss when load resistance equals internal resistance rule.


texts:
If I have an MCU, e.g. ATTiny85, and I connect a 5V source to a pin on the MCU, what current is flowing?

My understanding is that the pin I'm connecting to will be at 0V and if I connect the 5V source then a large current will flow due to virtually no resistance, but this isn't true.

How is my understanding wrong?


texts:
I have a boat with a dual battery system and have purchased two 0-30V voltmeters similar to this one, it has three wires which I understand is negative, positive and a wire for the voltage to be measured.

I am wanting to put one on each of the battery's and have them operated with a push button switch.

Am I correct in that the switch would go on the positive wire, and would it be better to have the voltmeter for battery A be powered off battery B, and vice-versa, or would it not matter much?

My intention is for this to be an easier and safer means of testing that the batteries have juice and a means of diagnosing faults at sea or seeing how much drain the house electrics are putting on the batteries so it doesn't need to be super accurate.


texts:
I have an ADC sampling at 500MHz (It is collecting data from an Ultrasound sensor). I need to be able to stream this data to my PC (for the time being - this will be done through a wireless unit). I am looking for a computing solution that sits in between the wireless unit and the ADC. I am putting all of this on a robot and I am trying to keep it as small as possible (in terms of dimensions) and hopefully keep the power consumption low.

Is there a solution that is better than using an FPGA? I have read that it is very hard to get an FPGA to run at 500MHz and some kind of Parallel computing might be required? Does that mean I am supposed to use GPUs?


texts: Can a pin be GPIO output and input at the same time?

texts:
So I'm working with an AD5593R chip, which I don't expect anyone to have specific experience with, but I'm hoping there might be a general principle which I can apply.

Basically there's a control register that lets you set which of its 8 pins are GPIO output, and a separate register that lets you set which of its 8 pins are GPIO input. This confuses me slightly.

What if I set them all to 1 in both registers? Are they all output and input at the same time? Or does whatever I set most recently override the other?

I mean, what about the control register that dictates which are DAC pins? What if I try to make them all GPIO in, GPIO out, and DAC simultaneously?

How does this sort of thing usually work? The datasheet does not make it clear.

I mean, I'm not even sure what happens if I tell set all the bits to 0 in all those registers-- then what mode are the pins left in?


texts: 555 timer to drive transistors with low load resistance

texts:
Recently, I have a project that needs to heat up a metal filament with a single pulse voltage. I built a circuit with 555 timer and transistors to heat up the metal filament(0.2 ohm). The circuit diagram is as below:

simulate this circuit – Schematic created using CircuitLab

The circuit works pretty fine when R1C1=3s; 12V with 1.1A going through the load. However, when the time begins decreasing to 0.01s, the current reads from the output voltage source is very low (300 mA at 20V) and could not heat up the filament at all.

Normally, when directly connecting to voltage supply sources, the filament would light up at 2V with 1.5A. I wonder the way to light up the filament in such low pulse second. Could anyone help me with this? how to design?

【Update】 Thanks for comments. I forgot to put common ground. The D1 and R2, R3 is for trigger purposes. I click a button to trigger that circuit, but sometimes trigger time would longer than pulse time. So I put those components there.

I tried to build this circuit with one BJT before, but it encountered the same problem. It worked pretty well ~3s but it could not light up the filament in just~ms. That's why I tried to put another BJT to increase current(maybe it's a bad idea).

【Update】
Thanks for answer. Right now the filament could light up via the circuit below.

simulate this circuit

Still, there are some tiny detailed problems I encountered. First, the light intensity which comes out from the tungsten filament is not always the same. At mono-pulse 20 ms mode, it originally could not light up at 12V. But after pulse it again and again(small time gap(~1s) between each pulse), it becomes lighter and lighter until saturation. But after waiting a longer time gap, it returned back to its initial state which is darker or even could not light up. Though pulsing two to three pulse voltage(20 ms), it could finally light up again with saturation intensity. I am not sure why this happened. Maybe some parasitic inductor? Could anyone comment on this problem?


texts: Average current mode control vs peak current mode control

texts:
I am reading an application note "Average Current mode control" of switching power supplies written by Lloyd Dixon. Here is the abstract :

If the average current mode control is better than peak current control why there is still components which are based on peak current control  ?
(On several applications I have a problem of noise immunity. Sometimes when I generate a high electric field next to my application, I see that the PWM of the UC384X is stoped as If there was a peak on the ISNS pin...)
Thank you very much and have a nice day.


texts: VHDL parallel execution of statements using variables

texts:
If a, b, c and d are variables, then this does not execute in parallel:

a := b;
c := a;

But what about the following:

a := b;
c := d;

Do these statements run concurrently or sequentially?


texts: Using a scope for an instrumentation and mains earth

texts:
When I make a measurement using a scope and observe transducer voltage output on the scope screen, I want to eliminate the noise as much as possible which is due to device and scope coupling or common mode noise like 50 Hz and its harmonics or capacitive coupling ghost voltages. I want to be left with the transducer's own noise(intrinsic) as much as possible.

After reading this question I still am not sure about the common practice.

Is it better to use 3-prong or 2-prong(aka eliminating the earth) in many cases for eliminating ground loops or capacities coupling between the device to be measured and the scope?

Is the only reason to use 3-prong for a scope safety?

In instrumentation should the instrument be powered from an isolation amplifier to eliminate ground loops  or coupling noise? Can you provide a diagram which illsutares some good practice?


texts: Disambiguation of Anode and Cathode Terms in Diodes

texts:
In a regular silicon junction diode the positive side is the anode an the negative the cathode.

But when someone uses a Zener diode that operates in reverse bias there is a problem with what constitutes an anode and cathode.

In a Zener diode operating in forward normally the anode is positive and the cathode is negative. But when the diode is operating in reverse bias, what constitutes an anode and a cathode?

Does anode and cathode describe the polarity of the terminal, meaning that now the old anode will be the new cathode, as the polarity has changed, or those terms mean the actual physical terminals of the diode, so now the anode will be negative?


texts:
Not long time ago, as i couldn't find a proper Mosfet to drive a high wattage led strip ( 5050,5630), i asked how to create a circuit that allows me to turn on properly the mosfets i already own. irf510,irf520 and the RFP70N06.
Led Driver/Controller for 3.3v & 5v circuit
i got it working an before i hooked it up to my microcontrollers i tested it with some 3v batteries(CR2032) leaving out the R1 resistor. it worked. then i put 3 1k resistors there. And used it with an arduino. And it worked. Not that i tested it much but everything was fine. Now i just finished to setup a new microcontroller, Raspberrry PI... so the difference is the 3.3v vs 5v of the arduino.

With the Raspberry Pi 3.3v i'm not able to turn on the green part of the led strip.

Now, the answer is prolly ... put a smaller resistor in R1.(wich one?)

But i want to understand.

The leds, red needs less voltage(2.1), the green needs more(3.1). but isn't the blue the one that normally needs more voltage(3.2)?
could this be a problem?
As i'm just driving a transistor with a Raspberry pin the above has not much sense. if i'm able to turn on red and blue i should aslo be able to turn on green.
where should i measure whats wrong?(i have a multimeter, no oscill..).
Maybe the raspberry pi's pin's don't all output the same voltage. Would that be normal?
if it's possible i want to be able to control this circuit with both logics 3.3v and 5v...  so if i need 2 different R1's i could desolder the 1k ones and create a custom smaller connection circuit to use with each logic. in that case what resistors should i use? or even better how can i calculate myself what resistors i need to drive it properly looking at the datasheet?
RFP70N06,  2N3904

simulate this circuit – Schematic created using CircuitLab

Note: The above schematics is for one channel there are 3 !!! red,green,blue.


texts: How to apply fourier transform to \$0.5^n u(n)\$

texts:
I'm working in a signals class for continuous signals, and we have this problem shown above. I have tried using this function \$f_1*f_2 = F_1 * F_2\$, where I'm assuming this means multiplication of two functions is equal to the convolution of their fourier transforms. I'm using \$f_1 = 0.5^n\$ and \$f_2 = u(n)\$.

So I can calculate the fourier transorm of \$u(n)\$ fine. It is \$\pi\delta(\omega) + 1/(j\omega))\$. However, I cannot for the life of me figure out \$0.5^n\$. I tried to put it into the fourier transform integral integral of\$(0.5^t)/(e^{j \omega t})dt\$ from negative infinity to infinity, but I end up with \$ 0.5t/e^{jw}\$, and when evaluated from negative infinity to infinity, I end up with \$ \infty \$ as my answer, unless of course the integration is wrong.

Therefore, either the answer is \$ \infty * \pi\delta(w) + 1/(j\omega)\$, which when convoluted would equal just the second function..? OR am I going about this problem completely wrong?


texts: Powering neon indicator lamp from battery

texts:
I would like to power neon lamp like NE-2 from low DC voltage like 1.5 V battery.

Is it possible to boost low voltage like that to 85-120 volts which is needed for neon lamp?  And can i use blocking generator schematics for that, or it will not work and have to use something with MOSFET like this?

I'm a beginner in electronics so i'm trying to keep schematics for this as simple as possible (less components and easier to assemble) even if it will be less effective.


texts: I simulated in Orcad an inverter, and I wanted that to Co-Simulate it in Matlab. The problem is that I get only '0' value on Simulink scope. The circuit in Orcad is (see first picture.) and the circuit in Simulink and the settings for it (see second picture.). Last picture is the result of simulation. The quiestion is: why my Output is always on 0 , I tought that the scope can't get the digital signals and I tried to get the values of variables on Matlab and plot them, but same result.


texts: How to interpret BGA package for creating footprint

texts:
I want to create a footprint for a BGA-292 package. I might be wrong but there are 2 different views of the package in the datasheet. The first outline shows:

In the photo above, the right side should be the flipped view of the top-view on right side. This makes sense, but, there is a top-view view of the pins as well:

If you look carefully, this does not match the first picture. Rows and columns are swapped while the A1 pin is still on the bottom-right corner of both pictures. Which one should I trust?

What does the TOP-VIEW mean? is it looking through the top of the package into pins? then why numerical and alphabetical columns and rows are swapped?


texts: Need a help with 3D Low Frequency Wakeup Receiver AS3933

texts:
I am software developer and I am totally new to circuits field.

Can somebody help me to understand how the 125 kHz transmitter and AS3933 receiver works?

This is the link where it says how it function, but the steps they have given  is very generic for me to understand.

http://www.ams.com/eng/content/download/200176/865682 (link goes to a 4.3MB PDF)

The steps they gave in the document (p.4) are as follows:

  Connect the +9V DC power supply F to the 125kHz Wake-up Transmitter Board.
  Insert the +3V battery at H of the AS3933 Demoboard
  Turn on the AS3933 Demoboard via the ON/OFF-Switch C. All LEDs flash up once.
  Start transmitting wake-up patterns via AUTO E of PATTERN B.
  As soon as the AS3933 Demoboard receives a wake-up pattern the RSSI LEDs flash up for
  0.5s and show the momentary received signal strength. At the same time the X, Y, or Z LED flash up indicating which channel receives the
  strongest signal

Basically what I am looking for from member of this forum , is to demonstrate what should I do in order to test this development kit. I mean 1st, 2nd , 3rd and...so on steps.

I also want to know in what specific distance this circuit will transmit and receive the signal?


texts: Implementing a TI antenna design on an existing PCB

texts:
I'm currently working on a PCB that processes certain sensor measurements. These measurements are then periodically transmitted over the LoRaWAN network (868MHz). I'm using an RFM95 module with an SMA connector and an 868MHz external antenna. This works fine but I'd like to incorporate the antenna into the PCB. I've done some research but I'm very new to antenna technology and I ran into some problems.

I've decided that I want to prototype with Texas Instruments' recommended antenna design for the 868MHz band. Whilst reading the design note I came across very specific antenna measurements (obviously), but also measurements for the ground plane located on the bottom side as visible in the image below.

However, I'm having difficulty understanding what I CAN and CAN'T do with this ground plane. As I'm looking to incorporate this into an existing PCB, I'm wondering whether I can populate the ground plane area with components or not. Furthermore, I'm wondering whether I can extend the ground plane as the current PCB is larger than 63mm x 43mm.

  Actual question: Can I extend the ground plane and place components on it as I would do in a regular PCB design.


texts: Connect lower power speaker to audio amplifier

texts:
I want to test an audio amplifier based on TDA7294 and the highest rated speaker I  have has 20W @ 4 ohms.

How can I connect it to the output of the amplifier without destroying it? I'm thinking I should use a series resistor, but how to calculate value and power?

I don't need a long term, reliable solution. I just want to test the amplifier at its maximum output power and I don't have the required speaker.


texts:
I know FPGA design using VHDL and I came up some new topic recently that usage  of triplication in FPGA but I am not confident about its understanding.

How can we use triplication in FPGA design and how do we verify this.


texts: Using a microcontroller to turn on LED strip

texts:
I have 60 leds that came in a led strip. One meter length of the led strip requires the following:

400 milliamps
12 volts

I want to control these LEDs with micro controller. I'm thinking of using a TIP120 and a raspberryPi.
A raspberryPi GPIO pin can output 50 milliamps continuously. (Update: This is not true, see below)

I am a beginner, and I'm not sure I'm doing this correctly. All my calculations are based off of things I read on this blog.

Math
Base current:
The TIP120 has a collector current of lc = 250 * lb so I'll need a base current of 1.6 mA.
( 1.6mA * 250 = 400 )
The raspberryPi should have no problems with the Base current
Base resistor:
I'll need a resistor low enough to ensure that the TIP120 base remains saturated but stays less than 50 mA as to not overload the raspberryPi.
According to the blog I mentioned, I find the base resistance by looking up the Vbe(sat). See figure 2.
where Vbe(sat) is 400 on the x axis, the collector current is about 1.3 on the y axis.

If the raspberryPi outputs 3.3 volts, then there is a voltage drop of 2 volts
(3.3 - 1.3)
So according to my calculation, I need a resistor between 4 and 40 Ohms
R = V/I
2 / (0.05 A) = 40 Ohms
2 / (0.50 A) = 4 Ohms
(Update: Incorrect, see bottom of question)
I still consider myself an amateur and I am in a bit over my head.

Do these calculations look correct?
Will TIP120 work? (any other suggestions welcome)
Are there any other considerations I should take into account for my schematic?

Update
As pointed out in the answers, I typoed the milliamp ratings by a factor of 10. I should have said:
2 / (0.005 A) = 400 Ohms
2 / (0.050 A) = 40 Ohms
Update 2
It appears that there is some fogginess about the maximum current a pin on a Raspberry Pi can provide. To be safe, I'm going to assume it is 8 mA.
https://raspberrypi.stackexchange.com/questions/9298/what-is-the-maximum-current-the-gpio-pins-can-output
https://raspberrypi.stackexchange.com/questions/1130/what-is-the-nominal-gpio-pin-output-current
Update 3
Ada fruit wrote a great blog article on how to control an LED strip with a micro controller. She recommends a  STP16NF06 or a  TIP120
https://learn.adafruit.com/rgb-led-strips/usage


texts: Error: HDL-Complier-661 Non-net port cannot be mode of input

texts:
I'm trying to develop a Verilog code for right shifting as a part of Floating Point ALU. I'm getting the following error in line 7:

Error: HDL-Complier-661 .... Non net port cannot be mode of input

Please tell me what my error is and provide me with corrected code.

        `timescale 1ns / 1ps

    module right_shifter(small_mant, shift_amt, shifted_mant);

    input [3:0] small_mant;
    input [2:0] shift_amt;
    output [5:0] shifted_mant;
    reg [3:0] small_mant;
    reg [5:0] shifted_mant;

    always@(small_mant or shift_amt)
    case (shift_amt)
    3'b000: shifted_mant <= {2'b01, small_mant[3:0]};
    3'b001: shifted_mant <= {3'b001, small_mant[3:1]};
    3'b010: shifted_mant <= {4'b0001, small_mant[3:2]};
    3'b011: shifted_mant <= {5'b00001, small_mant[3]};
    3'b100: shifted_mant <= 6'b000001;
    default: shifted_mant <= 6'b000000;
    endcase

    endmodule


texts:
I am wondering about 61000-3-2 current harmonics pre-compliance test.
Say a company designs a single-phase [up to 13A] power converter for low-line 115V and high-line 230V and pass 61000-3-2 pre-compliance test, should the same test be carried out for extreme cases such as 85V for low-line too?
Thank you.


texts: Find the right motor to lift a robot's arm

texts:
I'm trying to find the right DC motor to lift a robot's arm.
I know the total weight of the arm, its length, and its center of mass.
The motor only needs to lift the arm up about 45deg.
How exactly I calculate and find a proper motor for these requirements.
Is there more data that I need?


texts: How the DC source can make reverse bias diode?

texts:
I was studying up on the material we are going through, and found this video that talked about "biased clamper circuit."

At 1:34, it is confusing, how can the DC source make a reverse bias diode?

It seems to me like there should be any effect, because it's a DC source.


texts: Is there a simple way to discharge a bipolar capacitor using a 5V signal and a MOSFET/BJT?

texts:
I am using an op amp configured as an integrator, as shown in the schematic below. There is an input signal which can go both positive and negative [+1V ... -1V], and then depending on this input signal polarity the output of the integrator will ramp up or down until it reaches the supply rail of the op amp (±12V in my application). This all works fine:

I would now like to use a control signal from a microcontroller (~5V DC) to be able to reset the capacitor charge to zero at any arbitrary time, and keep it shorted out to prevent further charging. I tried to do this using a simple MOSFET, as shown below:

As can be seen in the SPICE calculation, this doesn't work properly - the charge is reset to zero correctly, but the negative part of the waveform is now clipped. I am not sure I understand why this is the case.

Can anyone tell me what mistake I have made, and suggest a way to achieve what I am looking for? Thanks!

EDIT ------------------------------------------------------------------------

After reading Caleb's answer, I have also tried to place a switch across the capacitor (a classic toggle switch here, but in practice could be an analog switch such as the DG417, as suggested). I have also placed a 1 kΩ resistor in series, to keep the discharge current through the switch at around 10 mA, as recommended in the comments (discharge response time is not an issue or requirement for me at all):

However, now a new problem arises as seen above. I didn't realise the need to specify in the original question, but whenever the capacitor is shorted I would also like the integrator output to be zero, regardless if the input signal is still applied. It can be seen here that the output is non-zero, as the input resistor and series discharge resistor effectively form a potential divider. Does this mean that I also need to add some MOSFET to short the output of the op amp down to ground whenever this "discharge control signal" is applied?


texts: Cannot find the maximum ratings for the output current

texts:
For the part of a circuit shown below I'm using an LT1007 but couldn't find any information about the maximum current output can sink or source.

They have written every tiny detail but the maximum output current is not there. Can anybody else see or infer it from the data-sheet?


texts: Implement a Function using 3x8 decoder (74LS138)

texts:
I need to implement the function below using 3x8 decoder (74LS138) and a minimum number of gates but I did not see 74LS138 before.

F = (A.B)'

I implement the function using a normal 3x8 decoder but I think it is not the best way to do that and I also need to use 74LS138.

My Solution:

Do you have any idea about the solution?

Thanks in advance.


texts: How to generate a random signal in multisim 14.1

texts:
I'm trying to design a circuit which digitised a very noisy input. It is normally +/- 1mv but will randomly peak up to +/- 20mv, the frequency of interest is 0.1<hz<10 but the signal contains higher frequency components up to 40 Hz. In order to best design the circuit I want to create a rudimentary model of the signal in multisim.
I know you can simulate thermal noise but does anyone know if there's a way to simulate other types of noise?


texts: Snap Action Switch SPDT - Electronic Symbol

texts: Does anyone knows if there is a certain electronic symbol for a "Snap Action Switch SPDT" like this at the below image?


texts:
I have started getting back into electronics and have been getting all my old IC chips organized into a simple storage solution. However, there are a few chips I have not been able to find any real information on.

The first one is the only one that returns any kind of internet search result. The ID number on it is DM74L93N. As far as I have found, I think it might be some kind of step counter. I haven’t been able to find out any more than that.

The other two chips don’t return any information at all. The manufacturer is NEC Japan. The number is either H760IT-726 or uPB7442C.


texts:
Considering an LCC HVDC system and that the flow of power is ALWAYS in the direction shown in the figure.
I know that converters in general produce harmonics.
My questions are:

Does this HVDC system produce harmonics only in the DC side in the middle and in the AC side circled in green? Doesn't it produce harmonics in the AC side circled in red too?
I think not, but if the converters produce harmonics also in the AC side circled in red, why and how it do so, since that waves enter the converters and not the contrary?

Is the aim of the DC filters on the DC side to create a straight behavior of the voltage and current?

I know that in LCC systems, the AC harmonics currents are reduced. Since the voltage depends on the current, is there a decrease of the harmonics voltage too?


texts: Stepper motor works as expected high rpm but not low

texts:
I'm working on a project where I will drive two 12V 0.4A bipolar stepper motors. I am using an adafruit ESP8266 HUZZAH, two L293D stepper motor drivers and a SN74HC NAND gate. I am supplying the motor with 12V. The code that I am using is simple, rotate the motor clockwise and then counter clockwise. This code works fine at speeds greater than 37rpm, but not bellow this. What happens is that the motor will not fully rotate 360 degrees and stop, cancelling the loop. The higher the rpm, the closer the motor gets to completing the rotation. This is an issue since I am mounting an IR sensor that will pan and tilt, allowing the temperature of the room to be scanned. The speed needs to be low to allow readings to be made.

NEMA 17 0.4A 12V

Adafruit Feather HUZZAH ESP8266

L293D

I know the L293D is not an ideal driver for this setup, but I do not understand why the motor is behaving in this manner. Thanks


texts: What are suggestions for resistor and capacitor substitutions?

texts:
When thinking about substituting components, I know that resistors are easily substituted within their 10%/5%/1% tolerances. But what about wattage on a resistor? Is it safe to do substitutions, say 1/4W when the schematic calls for 1/6W. What about tolerances? I assume that I can substitute a 10ohm/1% if the schematic calls for a 10ohm/5%, but not the other way around.

For capacitors, the only substitutions I've done to date are installing higher voltages than specs...e.g., if my schematic calls for a 470uf/15V, I've subbed a 470uf/50V that I had lying about. Is that a safe practice? or should cap substitution be avoided?


texts:
I have found this 7404 LC oscilator schematic online.

How does it work? I know that you can connect the input and out of a NOT gate and it will oscillate at a very high freq, dependant on parasitics and transition freq. of the gate.
In this case, does the 470k provide feedback required for oscillations or do those small 5pF caps provide 180deg of phase shift for it to work as a regular oscillator?


texts: Inverse z transform using partial fraction

texts: Here's my attempt at an inverse z transform using partial fraction. I was going through my textbook and it stated that all the z terms need to be converted to z inverse before using partial fraction expansion, yet I have hit a roadblock. Please advise.


texts: specific application of 9V battery pack substituted for a 9V power supply

texts:
I have a JamMan Solo XT loop pedal that is rated at 9V DC, 200mA. I want to make a really simple altoid tin battery pack. I'm checking with you guys because I don't want to damage the foot pedal with incompetence.

So if Pmax occurs at R1 = Rload, and Vload = Iload*Rload, then R1 = Vload / Iload which is 45 ohms. Is the circuit really as simple as this to make everything operate correctly and not damage the foot pedal?

Is it advisable to find an LED with 45 ohm resistance as a substitute for a standard resistor. Are there any resistor types that you might recommend?

Theoretical Schematic

simulate this circuit – Schematic created using CircuitLab

Practical Picture

Thanks guys!


texts:
The very cool circuit is from here:
http://engmousaalkaabi.blogspot.com/2016/01/81-led-chaser-using-double-ic-4017.html

Here are my few questions regarding it.

1, It has 18 transistors. are they really required for lighting up some small LEDs? I think 9 transistors should work.

2, It's about the 4017. When powering on and without a clock signal from 14, does Pin 3 (first output) goes HIGH or LOW? (according to this circuit, Pin 3 much go HIGH for it to work.)

3, what is 3.3k doing in this circuit?

4, last and my main question will be. Can I replace a 555 ic without a micro-controller such as a small attiny 95 and turn this array of leds into a clock? will the CD4017 fast enough for that? according to the datasheet, it has 2.5mhz clock input.


texts: reverse polarity protection using alternative configuration

texts: it is a typical diagram of reverse voltage protection using N channel MOSFET. what one should do is to connect the anode to the source of the MOSFET. But here instead of that I have connected to the negative or drain of the mosfet. The mosfet should trigger since still the gate is positive (V_z) with respect to the  source, but also we can see that the zener voltage is appearing at the gate-drain of the mosfet. will that cause any harm or any functional difference? Because since, the drain of the mosfet is isolated from the body, so does it even matter if we apply a voltage between GATE and drain?


texts: Can I output one flip-flop into another on the same clock pulse?

texts:
I have two positive edge octal D type flip flops with output enable (they're both 74LS374 chips), and I am wondering if it's possible to enable the output from one chip and clock the other on the same clock pulse, effectively copying the contents from one chip to the other

Thanks


texts: Coiling ac wire around iron rod bad or good?

texts:
I have around 4-5 meter excess wire length on extension board to power my computer. Power consumption is around max 500 watt.
I know there are probably 2 more thread on same topic.
But they mostly talk about heat because they are coiling around non conductive material.
As iron is more thermaly conductive than air, I think heat won't be an issue. Let me know if it is
The main part I am concerned about is coiling good or bad.
I know coiling AC wire creates some kind of flux ( I don't have any experties in electrical)
I want to ask whether it will affect my electricity bill?
Also is there any danger of electric shocked if I touch my table? ( Wire is coiled around table metallic leg.)


texts: Can I safely use a Triac at a higher specification than designed? e.g. for a BTA12 600TW, could I safely use a BTA18 800TW i.e. where the volt & amp values are larger than the spec?Thanks for any suggestions.


texts: Unexplained behavior pic port b on change interrupt

texts:
I am trying to configure the port b interrupt on change interrupts to work with a program I am writing with MC XC8 demo version.  I am using a PIC16F628A I am using this code to initialize the pic for interrupt reading.  However it seems when I start up my program an interrupt is called.  I don't understand why this is happening as the datasheet says interrupts will only be generated for pins set as an input and I have set all of port B to be output.  Could someone please explain this strange behavior

int main()
{
    TRISA2 = 0;
    TRISA3 = 0;
    PORTB = 0;
    TRISB = 0;
    CMCON = 0x07;
    initialise();
    writeCommand(0b00001111);
    writeCommand(0b00000110);
    writeString("Hello World ", 11);
    GIE = 1;
    RBIE = 1;
    PEIE = 0;
    while(1);
}

void interrupt interruptRoutine()
{
    if(RBIF)
    {
        writeString("Interrupt", 9);
        RBIF = 0;
    }
}


texts: Check the quality of not original Arduino boards?

texts: There are several reproduction Arduino boards available. How can I check that the board is wired correctly and that the ATmega chip and the other parts are comparable to the official design?


texts: Struggling with Thevenin Equivalent Problem

texts:
I had asked this question before and thought I had found the help I needed, but unfortunately I found myself unable to solve the problem fully when I attempted it. The problem:

For the Thevenin resistance, I believe I'm on the right track but am not confident in my answer: R5+(R4 ||(R2+R3)), excluding R1 because I believe it will become irrelevant if I short the voltage source?

As for the Thevenin voltage, I wasn't sure how I was supposed to go about solving it. Any insight would be appreciated.


texts: Quiet sound from ESP32 via decoder DAC I2S MAX98357A

texts:
I am building a project to play sound in MP3 format via the internet. In the project I am using an ESP32 NodeMcu and a MAX98357A. Sound is good quality but is too quiet. The MAX983557A is working in 15dB gain mode.
Is it possible to add an amplifier after the MAX983557A and before the speaker(3W ohm) to make it louder?
base pin setup:
esp32 25pin-> Max983557A DIN
eps32 26pin-> Max983557A LRCLK
eps32 27pin-> Max983557A BCLK

Max983557A + -> Speaker +
Max983557A - -> Speaker -
Max983557A VCC -> 5V
Max983557A GND -> GND
Max983557A GAIN-> R 100kohm -> GND

I tried connect PAM8403 amplifier between DAC I2S and the speaker but I heard a very loud hum.
Pin set up with PAM8403:
+ -> USB COMPUTER
- -> USB COMPUTER
Max983557A + -> PAM8403 LEFT_IN
Max983557A - -> PAM8403 GND_IN
PAM8403 LEFT_OUT_+ -> Speaker +
PAM8403 LEFT_OUT_- -> Speaker -

I also tried LTK8002D but this module was from anotherspeaker. The sound was a little louder but I heard the murmurs. In the end I burned it.
My project is based on this library: https://github.com/schreibfaul1/ESP32-audioI2S


texts: How to electronically disconnect two way data line

texts:
I have a SPI data line which dynamically is switched by several microcontrollers between MOSI and MISO mode, i.e. only one physical wire is used for two way communication. The micros take turns which one to use the line based on a protocol logic.

I need to switch one of the micros off the line, like physically disconnect it so the line is in high impedance and the other communication can go on undisturbed.

I tried with a tri-state buffer 74HC125, but it is only one way communication. Connecting two 74HC125 buffers "in circle" - A to B and B to A doesn't work. The line is always pulled low by the IC and not left in Z state.

I tried with a 74HC245 two-way transceiver, but still no success: I can switch directions from A to B and from B to A but only one at a time, and I need a full time two way connection when not in Z state. The stated "Latch A=B" mode in the data sheet does not work - the line is pulled low all the time by the IC.

So to recap:
I need to have a full time two-way communication line which can be switched to a high impedance mode electronically.

What would be the way to achieve this?


texts: Can I use a single resistor for multiple LED with different +ve sources?

texts: In the photo below I would like to use a single resistor after the LEDs, instead of having individual resistors before the LEDs. Is this problematic? Will it work?


texts:
Is there a short tutorial describing simple, low voltage circuit switching using the LPT port?

I know it could be done using USB or RS 232 relays, but I would like to assemble it with (buying) minimum or none electronic components, except things I have: an LPT cable, a LED diode or a fan, and a 12 V adapter.


texts: Eagle: keep decoupling caps near their IC

texts:
Is there a way to annotate decoupling caps in the Eagle PCB schematic, such that in board layout, the airwires (or some other thing) make it clear which IC it's 'supposed to be near'? Right now the airwires just give me a line of caps all between supply and ground, so I have to work out which cap is for which IC.
Of course they are mostly the same value caps, and I could figure this out with naming. But if I had a device with many supplies and lots of decoupling needed, it seems like this would be a pain, so I'm wondering if there is some smarter way to do this.


texts:
Is the below a valid circuit implementation and are there any things to watch out for? It's a simplification of the larger circuit but the crux of it is that I need to sink current into two GPIO input pins. The pins are signified by the 1 and 0.

Also, would a diode on the pins be advisable?

Edit: Here's the non-simplified circuit. The question relates to the 3.3v part of it. In essence, the timer and decade counter sequentially pulse current, 'activating' the transistors one at a time. The keypad is a simple matrix keypad. What I'm wondering if I can do is to put a GPIO pin on the line between the keypad and ground. The intended effect is that, when a button on the keypad is pressed, 2 pins will change state - this signifies the row and column.

Note that some of the resistance and capacitance values are notional at the moment.


texts: Calculating Thevenin equivalent circuit with series current source

texts:
Wikipedia writes this about calculating the output current \$I_{AB}\$ when finding the Thevenin equivalent:

  2a. Replace voltage sources with short circuits, and current sources with open circuits.

  2b. Calculate the resistance between terminals A and B. This is \$R_{Th}\$.

But! What if the circuit contains the following (independent) current source and resistance:

+--R---o
|
I
|
+------o

I think they could be replaced with a voltage source with the potential difference \$V=I*R\$.

If we calculate the output current before replacing and after replacing the above, we would get different answers! What am I misunderstanding?


texts:
In my design two solenoids (MagLatch C5-L-272-B-1  and  MagLatch B22M-L-154-M-36) are used. Each solenoid is driven by a H bridge powered by a voltage selector (12V or 24V). The command signals are driven by a microcontroller.

The 24V is used to latch (OPV_CLOSE_HB_TOP and OPV_CLOSE_HB_BOTOM activated) the solenoid in one position and 12V (OPV_OPEN_HB_TOP and OPV_OPEN_HB_BOTOM) is used to unlatch it.
The reason why there is a voltage switch is to follow the datasheet (Link) remark:

  The reverse voltage applied is dependent on the load attached to the plunger but must be well below the initial energizing value.

So to latch the solenoid a pulse of 24V is applied for 20 ms and to unlatch 12V for 20 ms is applied.
This works perfectly, but I am trying to improve this design by removing the 12V power supply and use only 24V for the H bridge, as shown on the next figure:

To latch the solenoid the same pulse is applied (24V for 20 ms), but now to unlatch the solenoid a pulse of 24V for a smaller duration (10 ms) is applied. By doing this the energy provided to unlatch the solenoid is half of energy provided to latch. For me the new design is equivalent to the old one. Am I right?

I have tried the new design and it seems to work, but I would like to know if it can destroy the solenoids in the future or if other unwanted behaviour can occur.

Any others suggestions or warning are welcome.

Thank you.


texts:
im new to pcb design,im trying to add copper pour in my design ,I always seen PCBs with signal line between copper pour, but in my case copper pour is on one side since board width is 5mm  only
just look at this picture

signal1 and 2 is analog signal, is it bad idea to keep signal line like  this heavy gnd near signal, is signal degradation will occur?


texts: Simple RC circuit connected to Transformer

texts:
I am trying to understand about RC circuits and am having confusion understanding power out of the secondary on an ignition coil with a simple RC circuit as load. The output of the secondary coil is pulses in the form of a sinc wave.
I initially have a setup as below:

simulate this circuit – Schematic created using CircuitLab
The voltmeter is actually an oscilloscope probe connected to an isolated channel on an oscilloscope.
I measure the voltage drop across the 1000 ohm resistor and then calculate the current and power. The output power is approx. 0.05W, the input power is run from a power supply unit and shows me the power, 2.3W. This gives a transformer efficiency of approx. 2%.
I then add a small 80pF capacitor in series as below:

simulate this circuit
As before I measure the voltage drop across the 1000 ohm resistor, then calculate the current and power. The output power from the transformer has now increased by approx. 1.2W BUT the input from the PSU has decreased to 1.5W. This gives a transformer efficiency of 80%.
A few questions that I am not sure about:

Can a simple small capacitor actually increase the efficiency of the ignition coil by that much?
If so how? I partially understand about resonance and this contributing to the magnetising current, but can such a small capacitor actually increase the efficiency and the power draw of the ignition coil by that much?
If not, where am I going wrong in my understanding, measurements or calculations, or could there be something else drawing more power than the small capacitor?

The overview of the coil is here:
https://www.summitracing.com/parts/msd-8225


texts: Convert 3v to 5v very high amperage using boost converter

texts:
I am trying to build a power bank that has 3 output USB ports that can provide 2.1 amp each; it has 8 LiPo cells. So total of 2.1×3=6.3amps so basically 7 amps at 5.1v out.

I have built the setup on breadboard but cannot get more than 2 amps out of even one USB port. I have tried making the inductor bigger, in size,  triple wire for lower resistance and larger diode and N channel MOSFET.

PWM is with STM8S microcontroller at switching speed of 64kHz using 3mH inductor. I thought that paralleling the inductor, diode and switch would be enough to give more amperage but I'm not seeing that as a result. Instead the result is just 2.1 amps total. Then Schottky diodes starts to become hot or the 3 logic level MOSFETs.

Can the boost converter be useful for low voltage, high amperage or do I have to use transformer based circuit? Or do I need 10 diodes and 10 MOSFETs and a huge inductor for greater current?


texts: Transient Response question. I want to know why during t>0, the voltage source has been short circuited?

texts: Can anybody please explain why the voltage source has been short circuited here after the switch has been closed at t=0. Thank You.


texts: How to design Power Line communication with line transceivers?

texts:
I am trying to design a communication system that will send data signals over a 400V DC voltage line by using line transceivers.
I attached the LTspice schematics below.
The transformer is for providing isolation between 400VDC and the transceivers.
The problem is the size of the inductor shown inside the red circle. If I decrease the inductance value, the square wave coming from the A-B input loses its shape and peak voltages occur. This causes false high voltages at the RO output of the receiver side.
However, since the DC current is 3.5A at the power line. The required inductor size increase enormously with the inductance value in order to prevent saturation. In the attached plot the simulation results are shown while using 200 uH inductor. You can see the problem. So, how can I calculate the required inductance and is there any other configuration for this system that works with a smaller inductor?

The "DK" input shown in the left of the schematic is similar to the picture I attached below.
I did not show the generation part of that "DK" input at the question for decreasing the picture size.
The LTC2862 transceiver outputs the modulated signal (second plot of the below picture) from its A-B outputs.
That modulated signal travels through the transformers and 400V DC line then comes to the A-B input of transceiver at the right side of the schematic.
RO output of this gives a modulated signal (but only 0V and 5V, like the green plot at the picture I attached at the question) according to the voltage at the A-B inputs. Then low pass filter removes the 80kHz carrier signal and the data sequence is formed and received just like the first plot at the below picture.
As I know this is amplitude modulation but If I am wrong please correct me.


texts: Choosing bootstrap capacitor for MOSFET driver

texts:
I have IRS2011 high/low side MOSFET driver, for driving IFRZ44N MOSFETs configured in H-bridge. How would I calculate the bootstrap capacitor required by the IC for driving high-side?

I am aware of the equation in this pdf, but since these wont drive the H-bridge continuously I dont know what to use for the frequency. I am driving a motor with the H-bridge.


texts:
I want to interface a thermal printer with an 8051 microcontroller. The thermal printer has a DB25 parallel port. I didnt get the information regarding device driver of thermal printer.
 The printer I am using is a cbm-1000.

RM - probably: Citizen CBM1000 printer as per manual here

The only information I have available is :

(1).  Write the byte to the Data Port.
(2).  Check to see is the printer is busy.
If the printer is busy, it will not accept any data,
thus any data which is written will be lost.
(3). Take the Strobe (Pin 1) low. This tells the printer that there is the correct data on the data lines. (Pins 2-9)
(4). Put the strobe high again after waiting approximately 5 microseconds after putting the strobe low. (Step 3)

Kindly help me on this project

setb p1.5 busy
bit P1.5 strobe
bit P1.4 port

Data equ P2

org 0h

start:
call word_Welcome
call enter call word_Lab
call enter

quit:   sjmp Quit

Printchar:
mov portData,A
jb busy,$
setb strobe
clr strobe
acall delay
Setb strobe
acall delay
ret

delay:
mov R7,#90
del1:
mov R6,#50
DJNZ R6,$
DJNZ R7,del1
ret

word_welcome:
mov DPTR,#Text_welcome

lagi1:
clr A
movc A,@A+DPTR
cjne A,#'$',Print1
sjmp Out1

Print1:
call Printchar
inc dptr
call delay
sjmp lagi1

Out1:
ret

word_Lab:
mov DPTR,#Text_lab

lagi2:
clr A
movc A,@A+DPTR
cjne A,#'$',Print2
sjmp Out2

Print2:
call Printchar
inc dptr
call delay
sjmp lagi2

Out2:
ret

Enter:
mov A,#0dh
call printchar
call delay
mov A,#0ah
call printchar
ret

Text_welcome:
DB 'aWelcome To$'

Text_Lab:
DB 'Computer Laboratory$'
end


texts: Xilinx FPGAs - how to demote specific warnings to info or make them disappear?

texts:
Xilinx tools give LOTS of warnings on any significant design. Sometimes, I go through fudging my design to remove warnings (like if one channel from an ADC module is unused, I go change the module to remove it, etc). However, I'd really prefer to be able to keep my design blocks fixed and logically complete (more reusable), and just mark the unused signals as "that's fine, I know about that, go ahead and do your thing (remove them)".

It's also much easier to understand say a 16-bit shift register if I can use a 16 bit signal, instead of for example a 13 bit signal in the case of always loading "00000" in the LSB bits. I've been obfuscating my code to remove these warnings.

Stupidly, marking outputs specifically as 'open' is still a warning...  although that's obviously the design intent.

Is there any attribute or UCF entry or anything that I can use to suppress these specific warnings but only for specific signals? (unused signal, signal always '0'/'1')

EDIT

I just discovered project message filtering. With that, I can mark specific warnings as hidden (using the complete text). This is close enough, I suppose...  although I'd still like a way to prevent them from being generated in the first place.


texts:
I have a stepper motor which step angle is 2 degrees. I want to display seconds using a needle attached to this stepper.

The watch crystal divides nicely to produce 1Hz pulses, so every second I can command the stepper to rotate CW 3 pulses (360 deg / 60 seconds = 6 degrees per second. Since the stepper goes 2deg per step, I need 3 of such pulses).

Now suppose I want to use each step to display seconds in a more smooth manner. I would need to step the motor every 1/3 of a second, or at 3Hz.

I'm trying to find out what's the best way to do that.

One obvious trick is to use a higher frequency (I'm using 64Hz) and tolerate some jitter. Is there any other way that will give me the exact 3Hz out of the 32.768kHz? (even knowing that one is not divisible by the other?)

BTW I'm using an MSP430, but this problem could be ported to any other platform.


texts: PIC: Watchdog timer off by a factor of 4

texts:
I have a PIC16 (datasheet here) for which I use the watchdog timer. I configure the watchdog timer as follows:

WDTCONbits.WDTPS = 0b01110;

According to page 105 of the datasheet, this should configure the watchdog timer for 16 seconds. However, the timer interrupt is called after only 4 seconds. (I have tested the timer with other values and the 4x discrepancy always persists.)

My first thought was that it was due to the 4xPLL being enabled. But as far as I understand, the watchdog timer is based upon the LFINTOSC clock, which is invariant under the 4xPLL.

Why is my watchdog timer running at four times the speed it should be?


texts: Where can I get CiA 302, CiA 304 and CiA 305?

texts:
Where do I find the following CANopen documents?

CiA 302
CiA 304
CiA 305


texts:
I would like to use eMMC as boot device in my design. I am planning to use a 8GB, version 5.1 eMMC(THGBMHG6C1LBAIL). But the processor,to which the eMMC is to be connected,supports only eMMC 4.4 version, with 4-bit IO mode.

Can you please clarify me the following.

1.Can the latest version of eMMC still be able to work with the processor version.

Generally,can we connect any latest version of eMMC to processor that supports older versions and still get that working.

Your help is highly appreciated.


texts:
Recently I switched off several molded case circuit breaker (MCCB) and saw a flash at the back of the breaker for an instant. This happened to all the MCCB on-site (around 14). The MCCB are all rated correctly - 200A capacity with a feed in peak load of 145A.

Is this perfectly normal? My knowledge tells me that the flash is a normal occurrence because I am breaking the circuit at a high current (probably around 100A), hence, the breaker had a flash as it is breaking the circuit contact (which is intended I suppose).

Thank  you.


texts: What is the meaning of this drill notation on datasheet PCB drawing?

texts:
Drawing the land pattern for a through hole part and am seeing this extra information below the main hole diameter (and tolerance):

For example, let's look at the one drawn right below the LED symbol (this is for a RJ45 connector with embedded status LEDs).  I see the main part is diameter 0.89mm but...

What is the 0.035mm beneath it?
What does PLC stand for?  It's not the first time that one has showed up on these datasheets, but I cannot for the life of me find the meaning of this acronym.  I noticed the diameter was quite small, so wondering if this is a pilot hole location.  My guess was "pilot location center" but that turned up nothing in Google either.
What are the numbers beneath that, in the box, with the ZYX?

Have always had PCB components fit my landing pads, so curious what the engineer was trying to communicate with all this seemingly extraneous info.

Note: It is unfortunate that the word PLC means something else regarding electronics.  That has made searching for this on stackexchange or elsewhere practically impossible with all the noise.

Thanks for the future edification!


texts: How to convert BCD to multi-digit 7-segment?

texts:
I have a BCD input in the form of 8 wires (eight bit number, up to 511 decimal) and I want to display it on a seven segment display.

I have found a product which has 4 1/2 digits and a converter, but according to the datasheet, there are only 4 BCD inputs (four bit number, up to 31 decimal). Am I reading the datasheet wrong?

I have also heard about multiplexing but I do not understand it.

The datasheet can be found here.
The product can be found here.

Thanks,


texts: vcc and ground connection in schematic and pcb

texts:
so I made my first pcb design using easyeda.com and the schematic and pcb link
My ground pins are all connected and i gave VCC too in the schematic but it is not shown in the PCB deign is that normal?
How can I improve my schematic and hence the PCB design(i have used autorouting for routing in PCB)
  The PCB I designed is an Arduino mega shield and its mainly used to drive 6 stepper motor and 6 servo motor along with endtops each stepper motor is 12v 1.2A bipolar stepper motor and servo motor is 6v(towerpro) mostly to move along different axis and servos for gripper(hold objects)
ICs and parts I have used
a4988 stepper motor driver
l293d dual h bridge driver for servo
arduino mega 2560
power jack to input power
some connector pins 4p & 3p connectors
updated schematics :


texts: reading the frequency and the magnitued from a GH bode plot

texts:
Lets say i have a GH(jw) bode plot,
And i have an input signal of sin(wt) to the system.
Is the GH(jw) bode plot actually can tell me the magnitued and the phase for each frequency i give in the input of the system, Or is it only tells me about the stability of the system?
Is it allowed to take the phase and magnitued out of the GH(jw) bode diagram and calculate the output signal?
Or should i use the trasfer function of the closed loop T(jw) and place my frequency in it and find the magnitued and the phase?


texts:
I have a circuit which provides power to an SOC and charges a battery when needed. For this, I have chosen to use two IP5306s. The reason I use two of them is because of the "feature" it has which causes a power output interrupt when USB power is disconnected and the chip switches to battery power. I have seen a couple other designs where two injoinic chips are used to overcome this issue. A good example is the PiSugar2 which used to feature an IP5306 and an IP5209.
The general design goes like this...
One IP5306 is responsible for charging the battery. This IP5306 can be connected to USB power, but it cannot be connected to the load that is the SOC.
The other IP5306 is responsible for powering the SOC. This IP5306 cannot be connected to USB power, but it is connected to the load that is the SOC. Another important note is that this IP5306 is the I2C version of the chip.
Both IP5306s are connected to the same battery.
Now before anyone asks why I don't just choose another charging circuit, I will say this. Using the IP5306 has proven to be the simplest solution while ALSO providing a way to read battery statistics over I2C.
Here I have provided a schematic which shows what I am working with along with some descriptions of my troubleshooting steps and their outcomes. Please let me know if there is any other information I need to provide to make this more clear.


texts: how should I label components changing between PCB versions?

texts:
I have a current version of my PCB, and I'll make a new one where I will delete some resistors here and add some more there.

What's the common rule for numbering? Should I re-use the numbers of deleted resistors for the new ones, should I re-number everything to avoid holes in the numbering sequences, or should I leave the holes in the sequence for the deleted resistors and add the new ones at the end of the sequence ?