texts: How to make the LM339 IC source current on its output pins instead of sinking current?

texts:
I know that the LM339 Comparator IC has a current sinking output. I made a small night lamp with the help of a LDR and an LM339 comparator IC. It worked properly.

The LDR connected to the inverting input (pin 4) of the IC and a reference voltage was supplied at the non-inverting input (pin 5) from Vcc through a resistor. This way the comparator compares the value of the LDR with the reference voltage and sets the output accordingly.

But, then I wanted to replace the LED with a transistor since I wanted to do more than just toggle LEDs. I tried to implement the transistor in my circuit like this, but it still does not work:

I just implemented a part of it (not the switches and all. I have my LDR in place of that) in my own circuit which uses an LDR. Its taken from an answer on another thread. That entire answer can be found here: https://electronics.stackexchange.com/a/283533/127782

I realize that in order to turn on the transistor I need a current source from the output pins of the LM339. How would I achieve that ? If that's not possible, or I have misunderstood something, can you just tell me how to operate the transistor in this circuit ?

Thanks.


texts: why does current flow from (+) psu A to (-) psu B?

texts:
I am a self-taught hobbyist, and I have a question about an experiment that I did. I got two ATX power supplies, a and b, and hooked them up as follows:

simulate this circuit – Schematic created using CircuitLab

I was not expecting current to flow, but to my surprise, the LED lit up. This is my first question: Why does current flow from PSU a to PSU b? Is this because the PSUs are connected to the same power strip, and are not actually insulated?

So after seeing the results of that, I had another idea. I wondered if the PSUs could sink current from a 9v battery. So I connected (-) of the 9v battery, and 12v from the PSU according to the following schematic:

simulate this circuit

Again, the LED lit up, but just barely. I could only just see a tiny bit of light from the led. Why does this happen?


texts:
I've been searching for a similar circuit and only found latching relays with two momentary switches for on and off. I don't know if this circuit has a specific name or not, and since I am a complete begginer I'm sorry if I missed it somehow. Here's my case.

I have a circuit that runs off a 12V DC power supply with one main switch. I need the circuit to be active when the power supply goes on. Simple enough. What I would need now is a switch that cuts the power to the circuit and keeps it off until the power supply is turned off and on again. So just one switch, no turning the circuit on after it's been pressed.


texts: Is the continuity test limit resistance of a multimeter standard?

texts:
The continuity shows us the shorts, but many times I guess, even if the wire has a resistance of up to 50 ohm, the continuity will beep to indicate a short.

Is it always 50 ohm, or what parameter should we look for in the manual?


texts:
I have been working on this layout. Lack of my training, my layout looks amateurish. Can I please get some general direction/tips on improving this design?

Some details:

Breakout board with USB/battery power option
Some differential pairs (USB, audio)
2 layer design - to keep cost down


texts: I was looking for the concept of "Full-scale error" (related with laboratory measurement terminology) on the web without success. I would appreciate your help.


texts:
Anyone knowing of a module that can monitor three incoming electrical phases to a home. If the load goes over a certain maximum, the device changes to one of the other phases for supply to e.g electrical motor?

Kind regards


texts: Why does the phase difference change after swapping elements that are in series?

texts:
I am trying to figure out how to correctly measure the phase difference of a circuit's different currents using multisim. After trying several examples, I noticed that spawpping the position of two in series elements (a restistor and a capacitor), it completely changes the measurement, as you can see below.

As you can see, just by swapping R2 and C1, I get a different time difference between two concecutive peaks (don't mind the negative sign). This confuses me, because I can't explain why it happens.

To make things worse, this difference becomes even greater with a similar circuit that uses different elements, as seen below.

To sum up, I'd appreciate it if someone could explain to me:

Why is this difference? How do I understand it?
How do I decide which one to actually measure if I want to calculate the phase of the current? Does it purely depend on the given circuit?


texts:
I apologize for the extremely basic question, but I want to be sure.

Ideally, an amplifier should have a linear output power to input power relationship. However, in most amplifiers (say a class AB amplifier) this relationship can break down at points. Am I correct in saying that as you go to higher input power, the slope of the output/input function decreases rather than increases?

In other words, if we consider the two graphs below,

does a typical amplifier act more like the blue curve or the red curve?


texts: Little help with this DE=A1D voltage regulator

texts:
So I bought this tiny Chinese camera module (cctv/fpv). It is supposed to take 5-12V, but the vendor states in bold red that it can only manage 3.7-5V. So far so good, I didn't intend to run it on more than 5V anyways. Then, after buying, I idly read through the reviews and found several stating that it burns immediately on 11V and on 5V the colors are washed out. This sounds like even the 5V would be too much.

Now to the question:
There's one review that says to disconnect pin 4 of the voltage regulator, then it would happily take up to 12V:

  Pin 4 of the SOT23-5  voltage regulator should not be connected but it is connected to VIN.  This causes the internal supply voltage and then the video output  voltage to fluctuate as VIN gets over 4V. If you disconnect pin 4 from  the board then you can use this board all the way up to 12V and the  picture will not get washed out but at 12V the little regulator gets  pretty toasty.

Does this sound like good advice?

I've done some digging through data sheets and found out this pin is called "Reference Noise Bypass" and should be connected to ground via a cap.

I am well aware that I bought Chinese crap, I just want to know if I would make it worse by disconnecting this pin.

I can't show the other side of the board because its completely covered by the lens mount.

Update:
I have used the camera a few times now on 5V, unmodified at first. Aside from the sun coming out black (which I think is either a sign of a too high voltage, or just of a cheap camera), I could not find anything wrong. After hammering it into the ground a few times I got black pixels all over bright areas (the whole sky, highlights on white walls indoors...) and I thought I had already damaged it. So I went ahead and just cut that BP pin to see if it would get better. It did, but I'm fairly sure it was unrelated. My video transmitter must have switched to the next channel (causing me to receive a bad image on the original channel) which I also corrected in the same step...
The specific data sheet linked by Ashish Jha says Reference Noise Bypass. This pin can be floating., so no harm done. Probably nothing gained either.


texts: Which TWO wires to disconnect to disable USB mouse

texts:
As there is more choice in DPDT switches than there is for 4PDT switches I am wondering which TWO connections are the best to disconnect to disable a USB mouse?

I need an easy to use switch that allows the mouse to be 'disconnected' without pulling the USB connector out of a laptop so I want to use a DPDT rocker or paddle switch.

From what I have found so far the pin-out is:

VCC (+5V)
Data -ve
Data +ve
GND

If my switch only allows two of these to be disconnected is it better/safer to disconnect both data lines, both power lines or one of each?

(Note: I've attempted to do the disabling programmatically in Windows but unfortunately Windows APIs identify the multiple input devices on the machine all as 'Generic HID' (Human Input Device) so it's not easy to determine the correct one to disable.)

(Note 2 - added in response to some comments and answers: The reason for this question is that I need to supply a solution to a user in a user-friendly manner. To this end registry hacks, Device Manager etc are not user-friendly enough. A simple toggle switch is easy to understand and, so long as it doesn't fry the MoBo or the USB hub, then is safer than sending a user into system settings.)


texts: Should the unit "Ohm" be capitalized or not?  For example, "kOhm" versus "kohm" vs "kΩ", which is most correct?


texts: What supplies ATS control circuit when the mains fail?

texts:
In a church, I've seen a large generator and ATS panel (automatic transfer switch) so that the generator turns on when there is a failure in the mains.
If there is no power in the mains, How does the control circuit of ATS work and send a signal to the generator to start?

I know that in power distribution rooms (stations) which contains switch gear panels, There are DC batteries (UPS). So that the control circuits still works even if there is no power in the mains.

Does the church have at least one battery? or there is another technique?


texts: How to adjust both brightness and contrast of a TFT LCD display

texts:
I am developing an HMI using the display "S039QWQ01HS" and I have the requirement to provide control to adjust the brightness and contrast of it.
For the brightness control, I have already configured a PWM timer to control the backlight of the LCD, but how can I adjust the contrast of the LCD?
I am using the emWin library to control the LCD display but I cannot find anything in the UserManual, neither in the Datasheet of the screen.


texts: How to fully shut off an LED indicator when used with a Smart Switch?

texts:
Update See added comments at end of question.

I am working on a project to implement a remotely lit indicator when triggered through a wireless connection. To make this work I am trying to use existing components as much as possible to eliminate having to build low level electronics. The idea is to use a smart switch that can be triggered remotely via a battery powered fob. The smart switch would then turn ON and OFF the indicator which is wired into the same electrical box as the smart switch. If the indicator is triggered ON from the remote it can then be turned OFF locally using the buttons on the smart switch. There is a problem in that the LED indicator is not fully switched OFF via the smart switch.

The smart switch from Lutron, model number PD-5ANS-WH-R, wired up with the switch using both the LINE (120VAC) and NEUTRAL wires.

(Picture Source: https://www.amazon.com/gp/product/B07GYBC77S)

The load wire of the smart switch is connected to an LED indicator that is then also connected to the NEUTRAL. The LED indicator is designed to connect directly to a 120VAC power source and is rated to pull up to 10mA when it is ON.

(Picture Source: https://www.amazon.com/gp/product/B01M6WULBK)

The internals of the LED indicator are as shown in the following schematic.

Test data measured with the smart switch and the LED indicator connected up shows the following result for voltage across the indicator and the current through it.

Switch ON - 118VAC - 7.5mA AC - Indicator fully bright

Switch OFF - 12.8VAC - 0.0056mA AC - Indicator very dimly lit

The conventional solution for LEDs that stay dimly lit with a smart switch is to place an incandescent bulb in parallel with the LED. That however is not suitable for my application because of the extra heat and no need for the extra illumination beyond the LED indicator.

I am looking for "out of the box" ideas on how to eliminate the dimly lit behavior of the LED indicator when the smart switch is OFF.

Update comments:

I tried the suggestion to add a 50K ohm resistor across the indicator. This did reduce the OFF state voltage across the indicator from the 12.8VAC level down to 9.2VAC but the indicator still glows dimly. I really suspect that the added resistor load on the smart switch may increase the leakage current some. Smaller and smaller resistor values could be tried but then there comes the problem of significantly increased power dissipation when the switch is ON and 118VAC appears across the indicator.
The idea to try placing back to back 33V Zener diodes in series with the indicator is really a non starter because it will reduce the full ON drive to the indicator thus making it not to be as bright as I would like.
Similar comment regarding trying to hide the dimly lit LEDs with some type of light blocking material. This will also have way too much impact on the fully lit indicator in the ON state which I want to keep as bright as possible.
I have sent away for a 120VAC compatible red neon bulb indicator to see if that will offer any better behavior on the switch OFF state.

Hopefully some other folks can offer some additional advice that may lead to a workable solution.


texts: Resistors getting hot in this MOSFET driver circuit

texts:
I created this circuit as general purpose MOSFET driver circuit for PWM frequency up to 10KHz (usually from microcontrollers):

But R3 and R5 are getting hot soon as I connect 5V supply and I did not connect PWM signal line (means that is floating). Could somebody please explain why? and what would be good values for resistors R3, R4 and R5?

They are 0805 resistors and SOT23 BJTs. Components are closer and hand soldered by me. Earlier I had experimented same circuit with normal through hole 1/4 watt resistors and TO-92 BJTs and I did not notice the heating problem that time.

I took this circuit from enter link description here, figure 4.

Thanks in Advance.


texts: Calculating the resistance for a high brightness led beads chip

texts:
If I'm playing with these little toys:

A 10W, 9-12V High Brightness LED Beads Chip:
(https://www.aliexpress.com/item/32901524656.html?spm=a2g0s.9042311.0.0.27424c4dfKjvBR)

A fixed power supply that gives 12.4 V 3A:
(https://www.aliexpress.com/item/32992892986.html?spm=a2g0s.9042311.0.0.27424c4dfKjvBR).

I don't know if I need to put a resistor in series to protect the LED, as it is needed with 5 mm standard LEDs.
Doing some maths, the needed resistor would be calculated using R = (Vs-Vi)/I, being I the desired Intensity current.
As the LED is rated at 10 W, its max intensity would be P = V x I; 10 W = 12 V x I; I = 10 W / 12 V = 0.83 A.
If I want to, let's say, protect the LED, I should apply a lower intensity, e.g. 0.75 A.
Then, going back to the formula to calculate the resistor, R = (12.4 V - 12 V) / 0.83 A = 0.48 ohms ?!
I'm pretty sure my calculations must be bloody and utterly incorrect, because such a ridiculous value for a resistor could not be right... or indeed it is telling me that I don't need that resistor...

Do I actually need a resistor with this kind of LED?
If so, how can I calculate its correct value?


texts: What is the software equivalent of an engineering change order?

texts:
We have a device on which we are considering doing a software update on a bare metal microcontroller. The new image would be programmed on all future products.

If I was to change a component on the device, I would need to fill in an engineering change order.

Is there an equivalent industry procedure when changing software?


texts:
I am designing an impedance meter with NI devices. I am applying 0-20 uA current signal to an RC circuit and measuring the voltage. Impedance is calculated by dividing Vp-p by Ip-p. I am controlling NI devices (both current output and voltage input) through MATLAB. Setup is displayed below.

I am getting these results:

My questions:

Why voltage signal is negative?
Impedance doesn't change when I change frequency of the current signal. Why?
When I change the amplitude of the current signal, impedance changes. Why?

Thank you


texts: What should be the PWM Frequency LED dimming in street light luminary

texts:
I want to know about the PWM frequency to be applied to PWM driver in street light luminary. Is frequency near 400Hz to 1000Hz OK.

What is criteria for the PWM frequency for the street light application

Thanks


texts: Is there hardware compatibility between CAN 2.0 High Speed, Low Speed and CAN-FD?

texts:
I am studying CAN interface hardware for the design of an automotive scanner. So far, I have identified the following types of CAN:

CAN 2.0 High-Speed: bit rate up to 1Mbps
CAN 2.0 Low Speed: bit rate above 40Kbps up to 125Kbps
CAN-FD: bit rates higher than 1 Mbit / s

From what I studied, the difference between High Speed and Low Speed is in the physical layer only, while CAN-FD is also different in the upper layers, mainly because it allows payloads larger than 8 bytes.

However, I still have some doubts regarding CAN-FD and CAN non-FD (CAN 2.0).

About CAN not FD (CAN2.0):
I checked out the discussion at Controller Area Network (CAN), high speed and low speed and in the in the chosen answer is said that High Speed CAN and Low Speed CAN has difference in Phyical Layer implementation. So, I have the following question:

Since I have the 120 Ohm resistor required for High Speed communications, and the data rate is configurable, then, if the CI I choose for my scanner allows up to 1Mbps, I could use it to communicate with different vehicles with different data rates like 125Kbps, 250Kbps, 500kbps and 1Mbps ?

About CAN-FD

Assuming that my hardware is compatible with CAN-FD, that is, it has a controller and transceiver that support CAN-FD. Could I use this same hardware to communicate with vehicles that have CAN 2.0 High Speed or Low Speed? I verified at Can you use a CAN FD transceiver for low speed (fault tolerant) CAN? that it is not recommended, however I found in CAN FD – The Next Big (Fast) Thing and other web sites, that CAN FD is reverse-compatible with existing CAN 2.0 networks.


texts: Measuring a binary number with maximum electrical certainty

texts:
I want to be sure, with arbitrary precision (let say, for example, with 10^-100 certainty), that I can check the following statement (in binary):

x = 49

That is, I want to check that a number that is (correctly) coded in a binary electrical signal is the same as a second number (also correctly coded in binary).

I'm a novice at electrical circuits, but I've worked out that I can perform this operation using 6 exNors and 5 And gates. I'm assuming there is some small uncertainty in these logic gates, and that there's a super small chance that these gates can misfire (maybe even so small it's associated with the quantum electrical noise).

If I wanted to make this system have arbitary precision, what could I do to prevent these errors from /ever/ occuring?

One option I thought of is to perform the same operation multiple times and AND-gate the results together. (I am perfectly fine losing "efficiency," that is, I don't mind if the circuit has "false negatives" where the number is correct but since there was a misfire in one of the circuits it does not return a 1.)

Is there a way that I can analyze the probabilities of the circuit being correct?  And what types of electronics would be ideal for this type of system (my guess would be that higher voltages would have less fundamental noise, so they would be the best to construct the system.) It seems as though there is some work on simulating the propagation of these errors using some advance techniques like monte-carlo simulations and baysian analysis. But is it not possible to get a crude, order-of-magnitude estimate for the amount of uncertainty/error per gate?

*Moved information in comments to the question where it belongs*
The purpose of this device I think is outside the scope of electrical engineering, but it's sort of related to metrology and quantum mechanics. I agree it's a very unconventional thing to be concerned with. I am first trying to get some kind of grounding on the topic because of how unusual it is. Any implementation (or discussion of errors, no matter how small) would be helpful (not concerned with hardware, frequencies, as long as it's digital).

Maybe rephrasing the question. If I performed this comparison operation on a microcontroller over and over, how much time (or how many repetitions) would it take until it misfired and gave an incorrect comparison? (Minutes? Days? Millennia?) And does this error loosely scale linearly/polynomially with the number of gates? So, for example, if I have 600exNors now instead of 6, does my operation misfire 100 times faster? (implying the errors scale linearly)


texts: What are the diode and two capacitors doing in this circuit?

texts:
I have an existing circuit from a working design that I am trying to understand in order to apply the understanding to a different circuit I'm building.

We can reduce the scenario to basically two ICs and a handful of discrete components. The first IC is a CPLD, and it is powered by 3.3V from the computer that it is installed in. The second IC is SRAM, and it is powered directly from a 3V coin cell battery. The two chips talk to each other through a couple control signals and a parallel data bus, and I think we can assume for the purposes of this question that the small voltage difference between the two of them is within tolerances for the signals.
The part I am struggling to understand is that the ground connection between the two of them is ultimately shared, but the ground of the SRAM is passed through a circuit involving two capacitors in parallel and a diode between them, before connecting to the shared ground.
My question is- what could that part of the circuit be doing? I'm guessing that it is in some way trying to isolate the ground of the SRAM, possibly to prevent power leakage between the two sides of the circuit. But I'm not sure, and I'm especially unsure of what the diode there is doing.


texts: What is the meaning of "Cut-in Current" and "LRA"

texts:
I was reading the specification of my refrigerator's Compressor where i found the following table:

Could you please tell me in non technical terms what is "Cut-in Current" and "LRA"


texts: Figuring out the functions of PIC numbers in a data file

texts:
I'm using Bumblebee software to interface my Wisp648 PIC programmer. According to the list of supported files for the Wisp, I should be able to program a PIC16F1829. However, that chip isn't supported by the software.

I decided to try to tweak the program. In the installation directory, I find files like this, 16f84.btd:

Version         = 4
Name            = 16F84
Algorithm       = PIC16
Code            = 1024
Data            = 64
UserID          = 0x2000-0x2003 [F1:0x3F80; F0:0x3F8F]
Configuration   = 0x2007 [PR:0x3FF0]

Or this 16f684.btd:

Version     = 4
Name        = 16F684
Algorithm   = PIC16E
Code        = 2048
Data        = 256
UserID      = 0x2000-0x2003 [F1:0x3F80]
Configuration   = 0x2007 [F1:0x3000; PR:0x00C0]
DeviceID    = 0x1080, 0x3FE0, 0x001F

I now want to make my own file for the 16F1829. I can figure out the functions of these parameters:

Name - the name of the chip (probably only used to show it in a list)
Code - the amount of program memory in bytes
Data - the amount of EEPROM bytes
UserID - the locations for a user ID
Configuration - the location of the configuration word

What I'm not sure about / don't know:

Version - appears to be 4 for most chips, but I don't know why
Algorithm - probably a different ICSP version(?) What should I fill in here for the 16F1829?
UserID - what does F1 or F2 mean?
Configuration - what does F1 or PR mean?
DeviceID - although the 16f84 doesn't have a device ID, the 16f684 and the 16f1829 have. But what do the numbers mean?

I searched for the numbers in the relevant datasheet for several chips, but couldn't find them. Could someone with more experience with microchip parts (or general microcontrollers) figure out what all these things mean, and where I can find the numbers for other chips (like the 16F1829)?

I found that Bumblebee doesn't just accept it if you add another file, but I'd still like to know what these numbers mean.

I used the official software, XWisp, to find some more information about the chips, with the info <chip> command:

C:\Users\Camil>xwisp info 16f84
XWisp 1.41, command line mode

Name        : 16F84
ID value    : none
Prog specs  : DS30262e
Code memory : 1024 instructions
Data memory : 64 bytes
Vdd range   :  4.50 -  5.50
Vpp range   : 12.00 - 14.00
Test status : Tested with a real chip.

OK

C:\Users\Camil>xwisp info 16f684
XWisp 1.41, command line mode

Name        : 16F684
ID value    : 1080
Prog specs  : DS41204G
Code memory : 2048 instructions
Data memory : 256 bytes
Vdd range   :  4.50 -  5.50
Vpp range   : 10.00 - 13.00
Test status : Tested with a real chip.

OK

C:\Users\Camil>xwisp info 16f1829
XWisp 1.41, command line mode

Name        : 16F1829
ID value    : 27E0
Prog specs  : DS41390C
Code memory : 8192 instructions
Data memory : 256 bytes
Vdd range   :  2.10 -  5.50
Vpp range   :  8.00 -  9.00
Test status : Implemented from specs, NOT tested with a real chip.

OK

This might be useful information (I don't know).


texts:
I'm looking at a schematic for an old turntable that I am needing help on when viewing the capacitor values.  All of the polarized caps will have 2 values written next to symbol i.e. C01 22/10 (MS).  I'm assuming one is the voltage and the other is the µF rating.

My Google-fu was not strong enough to find this answer so apologize if it has been asked previously.


texts: How to protect Ultrasonic Distance Sensor and Circuits from Water Vapours / Weather Conditions?

texts:
I am making the automatic water controller using Arduino and Ultrasonic Distance Sensors. My prototype is almost ready. But I have a doubt that if I put the sensors on lid of the water tanks, water vapours might cause some problem or could damage the sensor after a few months. Or if by some way water touches the lid it might also damage it. So how to prevent it?

Thanks


texts: How to know how much energy storage has powerbank?

texts: I just looked to this question and I don't understand how to know how much Wh this powerbank has (click "Specifications" tab), because it has different output voltages and I don't know how to calculate if it's 18Ah * 12V = 216Wh or 18Ah * 19V = 342Wh?


texts:
I've been trying to repair a Saunsui A-40 amplifier for a long time now, (when it was turned on, magic smoke started to flow).

I found most of the driver and power transistors all shorted, so i replaced them (had to use similar transistors because i couldn't find the originals)

I replaced every transistor in that schematic EXCEPT TR06, that one was not burned)

I checked every datasheet and the transistors i chose are suited for the job. (If it's necessary, i'll show the replacements i used).

The amplifier now turns on fine, but it has almost no output, and its completely distorted, only with volume below 3 you can hear really low an almost not distorted signal. I can't figure out whats causing the problem, every transistor seems OK.

I'll show next both channels schematic. (the full schematic is everywhere on the web)

Right Channel

Left Channel

Transistors

All electrolytic capacitors where replaced, and i made sure all resistors are not open circuit.

Voltages measure almost like the indication in the schematic (instead of +/-35V, i have +/-40V, because in my appartment i have 230Vac mains most of the time, all measurments are proportional to the ones in the schematic)

UPDATE:

Test conditions: 1kHz 1VPP sinewave to the input.

Voltage Across R78 = 0mV (this doesn't change with the trimmers)

Voltage @ TR10 collector = -2.5

Voltage Across C44 = 2V (meaning the Voltage @ TR12 is -0.5V when it should be 2.5V, is this correct?)

(i've tested with changing the trimmer to -1.2V @ TR10 collector, the TR12 collector is the same -0.5V)

Here is a screenshot of the osciloscope measuring

Channel 1 (yellow): Input

Channel 2 (blue): Collector of TR10 at a volume of 2 (almost OFF)

Here is a screenshot of the osciloscope measuring

Channel 1 (yellow): Input

Channel 2 (blue): Collector of TR10 at a volume of 5 (half way)
(maxed to 10 its very similar to this one but of course, sharper square)

So, first:

1- Can i solve the voltage @ TR12 collector problem by changing R58 and R69, or this could cause other problems? I doubt those resistors are causing the problem, what is?

2- Does the above problem have anything to do with the saturation of the signal right after TR10? ¿How can i solve that problem? (Note that this continues no matter what i do with the trim pot)


texts:
I'm trying to get the Lilypad working on my machine but i get the following error.

I had a Google for it but everything keeps pointing to a problem with the board. I swapped it out and tried another Lilypad but got the same error...

the one i am using is the first Lilypad with the FTDI connection.

This is the error message i am getting:

avrdude: stk500_recv(): programmer is not responding

Any thoughts?


texts: How are capacitor voltage ratings chosen

texts: I'm reading a user document of a dev board. On page 12, there is an explanation of the power management subsystem. The board VBUS and VBAT lines have a decoupling cap rated at 6.3V, whereas the output voltage rail has a 10V rated capacitor. What affects the decision of putting a higher voltage rating cap on the the rails. Would it affect the circuit if all caps were rated 10V?


texts:
Here I am trying to solve the circuit and from my calculation, I got, I(t)=3e^(-2t) - 3e^(-3t) and Vc(t)=12-18e^(-2t)+12e^(-3t)
When Initial conditions are;
I(0-)=0A and Vc(0-)=6V
From my assumption, current will flow through the circuit until the voltage across the capacitor is 12V so V(∞)=12V and I(∞)=0A. but when I simulate the circuit in MATLAB, I got something different...

1st graph is for current and second graph is for voltage across capacitor.
Here both current and voltage are zero in steady state. How is it possible that steady state voltage across capacitor is zero? Also the current graph is inverse of what I theoretically calculated. Where am I wrong? Please help me out.


texts:
I have a 12v battery directly powering a handful of electronic devices (router, modem, hard drives).
These vary from 0.5a~2a so I have breakers on the (+) lines into the 12v dc power plug.
I'm noticing when I charge the battery through a 120v wall charger, the battery outputs up to 14.1v and during discharge it dips to 12v.
Since I would want to keep a constant, what device would I need to keep a constant 12v output from the battery during charging and discharge?
Would this dc/dc boost be a device that could help?
http://www.mini-box.com/DCDC-USB-200?sc=8&category=981

edit i think this actually solves my issue
Clean 12v car power


texts:
First of all, I know very little about electronics, so my question may seem very stupid.

I have 2 circuits, both have a microcontroller but they have a different power source (both powered by USB, but from a different source). The first circuit should be able to output an analog signal (0-5V) to the other circuit but of course they don't share the same GND so that doesn't work "out of the box". The analog signal comes from a DAC (MCP-4725).

What's the best/simplest way to accomplish this?


texts:
I am building a LED array and am unsure of if I have been given bad information. I was told i can use a PC PSU to power my LED array safely using resistors and rheostats to dim them. After doing some research i have found out that LEDs need constant current more than constant voltage - a PC PSU is constant voltage.

The LEDs I purchased are all 10 watts each. I will be running 11 of them and would like to use one power supply if possible. The specs on the different LEDs and hardware are below:

4 x White
Foreward voltage: 9-11v
Foreward current: 900 - 1050 mA

4 x Blue
Foreward voltage: 9-11v
Foreward current: 900 - 1050 mA

1 x Violet
Foreward voltage: 9.5-10v
Foreward current: 900 - 1050 mA

1 x Green
Foreward voltage: 9-12v
Foreward current: 900 - 1000 mA

1 x Red
Foreward voltage: 6-8v
Foreward current: 900 mA

11 x 2 Ohm Resistor

4 x 1 Ohm rheostat

My plan was to power all of the LEDs on the 12v line, use a resistor for each LED and a rheostat for each color wired in series (blue and white use 1 rheostat). Red would use the 5v line and a resistor and rheostat.

My question is can i use a PC PSU? Is it a bad idea considering its not constant current?
Would this setup work or would it burn up the LEDs? Would there be a better way to wire or drive this? If so what kind of a driver would i need?


texts: Voltage generated by piezoelectric effect

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When you apply a voltage to a insulator if the insulator is shaped appropriately its shape is changed.
When the piece of insulator returns to its initial state a voltage is generated by which is its polarity compared to the original voltage?


texts: Crystal compensation for temp and voltage

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Introduction

I'm toying with the design for a fail-safe wall clock controlled by multiple 32.768kHz crystal oscillators. I'm currently reading about compensation.

Compensator from literature

From what I read (e.g. this paper, Design Technique for Analog Temperature Compensation of
Crystal Oscillators) crystal stability over temperature is cubic at best:

In that paper, Haney suggests the following compensation circuit:

It's interesting, but I have my misgivings. I'm comparing that to a "dumb" design based on microcontroller lookup table compensation. In my estimation, the comparison basically goes like this:

Analog compensation advantages

Less reliance on digital circuitry
Decreased cost of microcontroller
Less noise generated by digital traces
Analogue circuitry has infinite resolution, whereas LUT and ADC have limited resolution
No ADC error introduced (quantisation, linearity, etc.)
Less dependence on characterisation than LUT; LUT needs better sample size
Analogue compensation is instant(ish); digital compensation has latency

LUT compensation advantages

Analogue components have their own tolerances and temperature drift characteristics, and that effect snowballs with increased analogue circuit complexity; this approach has fewer analogue components
Decreased cost from analogue components
Decreased analogue circuit complexity means fewer potential points of failure
Less dependence on analogue analysis
Less analogue component cost
2D LUT can compensate for both temperature and supply voltage variation; circuit above would need additional complexity to compensate for supply voltage, esp. when battery-driven

Questions

Are there any inaccuracies or gaps in the list above?
Are there any simpler approaches to analogue crystal temperature compensation than the one presented by Haney? Would it be worth combining that with a LUT?

As a sidenote, it turns out that there are many integrated VCTCXO (voltage-compensating, temperature-compensating) devices out there, and this is probably what I'll end up using.


texts: How to control power from 12V battery to RPi with a microcontroller

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I have an LM2596 module and a 12V lead-acid battery which I would like to use to power a RPi zero and control with an ATtiny85 in a project which requires the RPi to be active 30s and then shut off 270s.

My question is: How do I toggle BAT1 on or off using as little current as possible?

In my project I want the RPi to only turn on if there is enough light outside, so I am using a photoresistor for that.

simulate this circuit – Schematic created using CircuitLab

So, to clear things up. The photoresistor (U4) is powered by PIN2 only when required to read the light level and PIN3 is used as an analog input on the ATtiny. I don't know how to switch BAT1 from my microcontroller.

I've measured the power consumption of the RPi zero which is at max about 150 mA and on average about 60 mA.

Photo of the LM2596 module I am using:


texts: How many individual lights can an arduino control

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I want to use a regular Arduino board to control LEDs - what is the most lights I can control individually from the board?

Is there a tutorial on how to hook it up?


texts: Hacking Circuits Together Using Existing Schematics

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I am working on a prototype using existing breakout boards from open source hardware manufacturers (Sparkfun, Adafruit, Teensy etc...). Everything is going great!

I am at the stage where I'd like to start designing my own PCB in order to consolidate the components into a single board.

Right now, each breakout board is powered by the same LiPo battery, so it seems that I might be able to simply use the existing schematics from each board and simply combine them onto a single board, where each "component group" draws its power from the battery and shares the ground... analogous to the manner in which the individual breakout boards are currently wired up.

Is this as simple as it seems, and is it common practice for beginning circuit builders to take this approach without implementing KVL, KCL, and Thevenin node calculations, etc...

Thanks for any advice on this.


texts: Virtual terminal in proteus outputs garbage values

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I am using the LPC2148 MC to interface its UART in proteus, I have tried using the UART window in Keil uVision 4 and got the correct outputs. but in proteus, it spews out garbage values.

The clock frequency I am using for the baud rate generation is 15 MHz using the on-chip clock generator and also tried using the external crystal oscillator without any success.

Is there any difference between using the Serial window of Keil and the virtual terminal?

P.S: I have configured the virtual terminal correctly (with 9600 baud rate, 1 stop bit and no parity bit.)

Edit: Here is a code snippet for initialising the UART and transmitting the data.

#include <lpc214x.h>

char numbers[10][2];
int digits[10];

void UART0_init(void)
{
  PINSEL0 = PINSEL0 | 0x00000005; // Enable UART0 Rx0 and Tx0 pins of UART0
  U0LCR = 0x83;                   // DLAB = 1, 1 stop bit, 8-bit character length
  U0DLM = 0x00;                   // For baud rate of 9600 with Pclk = 15MHz
  U0DLL = 0x62;                   // We get these values of U0DLL and U0DLM from formula
  U0LCR = 0x03;                   // DLAB = 0
}

void UART0_TxChar(char ch) //A function to send a byte on UART0
{
  U0THR = ch;
  while ((U0LSR & 0x40) == 0)
    ; //Wait till THRE bit becomes 1 which tells that transmission is completed
}

What value of frequency will be suitable for the on-chip clock frequency or for the external crystal oscillator in proteus?

I tried making both of them 15 MHz at the same time and also tried making them 15 MHz individually.


texts: Need help with circuit design for current measurement of car starter

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Okay I want to make a simple circuit to measure high currents coming from my car battery, and I think I have something that might work, but I'd like anyone who knows more about this to point me in the right direction.

I read car starters can pull hundreds of amps, and so for the sake of this design, I just assumed my car will max out at 200A during ignition.  It might be higher, but I have a small car (Ford Escort) and I think if it goes over 200A for a brief bit it will be okay.

My design is to use a shunt resistor to get a reading of the high current.

It's a 200A, 75mV scale shunt from Digi-Key, here.

So I want to take the voltage on the shunt, feed it into an op-amp, and scale it to max out at 5V for an arduino.  Here's what I came up with.

If you slide the resistance all the way to the left, the load (modeling the starter) will drop to 0.06 Ohms, which is what I'm estimating the starter to be to draw 200A from a 12-V battery.  .06 = 12/200.

Then if you slide it to the right, it mimicks normal operation, for current draw for the rest of the car, and will go as high as 12 ohms, pulling 1 amp.

You can see the output of the op amp maxes out at 5V, and the power on the shunt maxes at about 15 watts.

So obviously this circuit design looks like it could work in theory, but what I want to know is if there's a better way to do this? Or if the circuit can be improved? Or if it would even work at all?


texts: electret condenser microphone plugged directly into arduino

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Possible Duplicate:
  Using a microphone with an Arduino

Can I plug electret condenser microphone directly in ardunio and read ambient sound level? I imagine those microphones pickup sound like voltage and change accordingly...

Will there be a need to amplify signal?
what if I plug in 5 microphones?
do I need to amplify each?

My project is very simply, I want to create 5 lights wich will activate based on sound level around them.


texts: How to avoid using relays/analog switches in a musical sequencer?

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I'm building this:

Albeit with a single pulse adding a bit to the shift register when the circuit is powered and another 555 timer (I'll probably use a 556 for both) to provide the clock for the shift register.

I want to avoid using the relays I have integrated in favor of this:

Which avoids the relays (or analog switches or w/e), but which I also do not understand. That being said, my question is,

How do I integrate the style of the latter circuit in making a shift-register based 555 sequencer without relays/analog switches?


texts: Negative Voltage In Capacitor When + Side Is Connected To -

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Hello, i just didn't understand that why we get negative voltage(-4.7V) from capacitor's negative pole when we apply 0V to capacitor's positive pole.As i figured out, this is used in transistor flip flop.

Power Supply : 5V

The site that i used for simulation is https://www.falstad.com/circuit/circuitjs.html

Circuit Link : Click Here

Please help me, best regards.


texts: MSP430 SPI not working at higher speeds (4+ MHz)

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I'm trying to output a byte's waveform using SPI in master mode. This is working as expected when using the REFOCLK at 32 KHz. However, when using XT2 at 4 MHz or the DCOCLK (at 20 MHz) the waveforms look completely wrong, as shown in the attached picture. Why is this happening? Is their some special setting I need or is the MSP430F5529 just not capable of SPI at these speeds?

First image: Output at 4+ MHz (50 ns horizontal intervals), Second image: Output at 32 KHz

(Measured with the Hantek HT6022BE, which has a bandwidth of 20 MHz.)

Clearly, the 4+ MHz is not putting out the correct waveform, while the 32 KHz is.

WDTCTL = WDTPW | WDTHOLD;                           // Stop watchdog timer

SetVcoreUp(0x01);                                   //Bring up power, taken directly from datasheet
SetVcoreUp(0x02);
SetVcoreUp(0x03);
__bis_SR_register(SCG0);                            //Disable FLL
P5SEL |= (BIT2 + BIT3);                             //Set crystal ports
UCSCTL6 &= ~XT2OFF;                                 //Enable XT2
UCSCTL3 |= SELREF_2;                                //Set FLL
UCSCTL4 |= SELA_2;                                  //Set ACLK also
UCSCTL6 |= XT2DRIVE_0;                              //Select power needed for XT2
do
{
    UCSCTL7 &= ~(XT2OFFG + XT1LFOFFG + DCOFFG);     //Clear fault flags
    SFRIFG1 &= ~OFIFG;                              //Clear general oscillator fault flag
}
while (SFRIFG1 & OFIFG);                            //If fault, OFIFG&SFRIFG1 will be non zero (true)

UCSCTL4 |= SELS__XT2CLK;

P1DIR |= (BIT0 + BIT2);
P2DIR |= BIT2;                                      //Set P2.2 as out direction to monitor clock
P2SEL |= BIT2;                                      //Select P2.2 as SMCLK output

__bic_SR_register(SCG0);                            //Enable FLL

UCB0CTL1 = UCSWRST;                                 //Put UCSI in reset state for configuration
UCB0CTL0 |= (UCSYNC + UCMST + UCMSB + UCCKPH);      //Enable settings: SPI mode (insetad of UART) + Master + Most sig byte
P3SEL |= BIT0;                                      //Port select
P3DIR |= BIT0;
UCB0CTL1 |= UCSSEL1;                                //Disable UCSI reset state and select SMCLK src
UCB0CTL1 &= ~UCSWRST;                               //Enable UCSI

while (1)
{
    while (!(UCB0IFG & UCTXIFG));                   //Delay until UCB0TXBUF is empty

    UCB0TXBUF = 0xEE;                               //transmit 11101110
    __delay_cycles(10000);
}

p.s., I know the SPI is synchronous, but I need these high speeds because I'm actually just using it for the waveform, not to communicate with an SPI slave


texts: Influence of copper thickness on interference between PCB tracks

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Explanation :

I have designed a PCB for motor control. On this PCB there is a power part and a logic part.

The power part is composed of MOSFETs, MOSFET drivers, hall sensor for current feedback and some protections (resistances, diodes…). The logic part is based on a Teensy (a logic board with an ARM Cortex-M3), some Phoenix connectors, voltage dividers, etc. There are also switching regulators to power the logic.

This is a two-layer board with no internal layers. The tracks for the power part are 6 mm width, those for the logic are 1 mm width. Clearance between tracks is at least 0.2 mm. The board has been tested with a 35 um copper thickness and except for some interferences, present on the logic when the motor draws current, the board is working well. Up to now these interferences are software corrected (median filter).

I want then to make the board with a 70 um copper thickness, to be able to pass more current to the motor.

Questions and ideas:

What will happen to interference, if I change from a 35 um copper thickness to a 70 um one (for all the board, so power and logic will be changed to 70 um)?

I think they will increase because the sensitivity of a track to interference, depends on its section and length (wider and longer mean more subject to interference for me). True?

Do you think I need to increase my clearance? If yes, to which value?

I think it also depends on the MOSFET frequency commutation compared with track length (resonance…).

Any help will be greatly appreciated!


texts: Digital Latch Circuit with Unknown Outputs

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Introduction

I am a student currently enrolled in a digital course course. I'm actually an analog kind of individual so I (like most other analog people) have a hard time understanding logic. Anyways, here goes:

Problem

Here is a digital circuit that resembles a latch. I attempted to create a truth table, but found it hard to follow through towards the end. When either A or B is false, the output of the AND gates are immediately false. But when A and B are both true, I can't determine the output of the latch. It appears as if every time I follow through the wires labeling the logic value, they switch over. I'm kinda wondering if this is how clocks are made also?

Question

Given the circuit and truth table shown above, can anyone help me understand why the outputs of this circuit are strange when A and B are both true?


texts: Phototransistor and Photodiodes capacitances when some in an array sense light

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I'm using phototransistors to sense low speed data (about 7 bits a second). With one phototransistor and a 300K resistor, I found my sweet spot and can transmit correct data with lazer.

I find if the resistor value is too high, I won't be able to sense data, and if the value is too low, then the sensitivity is too restrictive.

The phototransistor I use is wired in a common-emitter fashion (with collector to +5V through 300K resistor). The model I'm using is PT334-6c. I'm not entirely sure on the value of the capacitance in that model but I know one exists somewhere since the manual indicates the rise and fall time is 15uS if the resistor is 1K.

For the remainder of my question, let's give this capacitance a value of X.

Now if I connected two phototransistors in parallel to each other (collector to collector and emitter to emitter) and have one resistor as the load, will the capacitance value be 2 times X and will I have to make the resistor half the value?

And what about if of those two phototransistors, one is completely covered so no light enters it, and the other one has the valid lazer pulses going to it? would the capacitance still be 2 times X? or just X because only one phototransistor is active?

How would the number of phototransistors that detect the pulses out of the total number of phototransistors in parallel affect the total capacitance of the phototransistor network?


texts: Can someone explain me this part of the schematic?

texts: This is a linear power supply schematic. I understand 90% of the schematic but that constant current sink is giving me trouble. Can someone explain the purpose of it?


texts: How can I get this to not read an arduino digital input?

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I have been working on this for a while.  It is a small part of a much bigger code.

I have a digital input pin connected to a on/off switch and another input pin connected to a momentary push button. For the momentary push button I am using the onebutton library. It works great.

I am trying to make it so the momentary push button does nothing unless the on off switch connected to a digital pin if switched on or HIGH. For some reason the momentary push button still gets read and my program runs regardless of whether the switch is swichted or not.

void loop()
{
    ignition_mode = digitalRead(ignition);
    if (ignition_mode == HIGH);
    {
        button.tick();
    }
}


texts: Splicing tiny wire inside broken mouse cable

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I don't know a lot about electronics repairs, but I've got a relatively expensive laser mouse that got a frayed connection on the wire:

I'm wanting to repair it as it's out of warranty.  I've cut the cable on either side of the "stopper", isolated each of the individual wires, and stripped the ends off in preparation for splicing.

Stripped http://img163.imageshack.us/img163/196/dsc2886c.jpg

I've read some instructions that indicate I should do an inline wrap and then apply some solder.

Is there a better way for wires this small?

Is there a particular type of heat shrink wrap I should put on this after it's spliced?  Or will electrical tape suffice?

Inside the mouse, the cable is connected to a little plug.  To me, it looks a lot like the fan plugs inside a PC.  It's got 5 pins each 1mm apart.  If there were a replacement plug I could buy and crimp the wires into, that'd be great!

http://img171.imageshack.us/img171/5205/dsc2893d.jpg


texts: Increasing Speed of Bootstrapped Amplifier

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I am trying to implement the design described here to create an amplifier circuit that will amplify a 10MHz, 24Vpp signal to 120Vpp. I am using the THS3062 op-amp, and originally I was looking at using the 2SC4883A and 2SC1859A transistors.  I am simulating my circuit in LTSpice using circuit models for all the parts, and found that it worked up to about ~50kHz. I tried replacing them with the CZT5551 and the CZT5401, and found that it worked up to ~300kHz.

I believe that the transistors are not fast enough, and since I have a higher voltage split supply, my transistors would need to have a high maximum Vce as well as a high speed. Is is possible to find a low-gain, high-speed, high-voltage transistor that will enable this circuit to work at higher speeds? Alternatively, could anyone recommend a modification to the circuit to make it work faster, or possibly an alternate circuit?

Here is my Spice schematic:


texts: Keep constant LED intensity using 3 leds (RGB) with different duty cycles (for different colours)

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I am using three LEDs (red, green, blue) to display some colors. In particular I am using the following colors and RGB values:

* red:          4f 00 00
* orange:       40 14 00
* yellow:       50 50 0
* light green:  10 2f 10
* green:        00 4f 00

Each value is in hexadecimal, from 00 to ff. They configure the duty cycle of each of the leds.

I would like to keep a constant intensity no matter the color, but for that I need to somehow 'normalize' the intensities of the 3 leds, so that when using multiple leds I don't get a higher intensity.

How can I properly scale all those vectors of RGB values so that they give the same intensity? I don't know how the intensitiy of several LEDs adds together...


texts:
I’m trying to solder my TSSOP-16 chip to the DIP adapter. I’m planning to apply solder paste to the adapter’s pads, put the chip on the adapter and then use my kitchen oven to melt solder paste and connect those two together. I have a few questions:

Should solder paste be precisely applied to each of adapter’s pads without going over to neighboring pad or is it okay to just smear solder paste on all pads?
Should solder paste completely cover adapter’s pads or should i put just enough paste so that SMD chip’s leg om adapter-pad is covered?
At what temperature and for how long should I keep this in my kitchen oven?

Here’s an image of my adapter, little smd chip and solder paste:


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As I understand it there are two reasons to ensure your electric guitar strings are connected to the common ground of the instrument.

To dissipate the EMF/RF interference created by the human holding the instrument, which reduces the noise level on the circuit
Safety

I understand the first. But the second reason I struggle with.
The oft sighted example...

it's possible for the common or neutral side of the line to be out of phase with another power outlet or piece of gear. So, instead of the chassis and all common parts sitting at ground potential, they're at line potential relative to another piece of gear.

So far so good.

if you're holding onto a guitar with "grounded" strings that are correctly grounded and walk up to the microphone with a "grounded" housing that really is at line potential it'll knock you flat on your ass. Done properly, it can even kill you.

So surely, in this situation the, the fact the the guitar strings are grounded makes touching the strings more dangerous. If the strings were not attached to the circuit you'd be safe?
So I'm thinking, if the strings are not grounded at all the current might pass through my body and kill me that way, but at this point isn't the guitar irrelevant? So grounding the strings is pointless?
EDIT:
So looking at that link in the comments. The 3rd example in Kyle's link sees the path to ground from a faulty mic either going through the guitarist's feet OR through the earthed strings, but the latter is said to be more likely lethal. So the question remains, why ground the strings of that makes the legal path more likely?


texts: A recent question asked about the advantages/disadvantages of various types of MCU. AVRs seemed not even worth a mention given the answers.  Why then does it seem to an outsider that AVRs are experiencing a rush of popularity?  Is this solely due to the Arduino, or is there something else that makes the AVR an especially good microcontroller?


texts:
I am trying to make a 24VAC to 5VDC converter. My constraint is to keep the height of the entire power module to as small as possible (ideally < 5mm) I have the buck converter design with the height of all components <= 5mm. However for the input capacitor I can't find a capacitor with a small enough height.

My requirements for the power module are:

Vin = 24VAC
Vout = 5VDC
Load current = 1.5 A

Would it be worth considering to put a diode/diodes where the "forward voltage drop" is high enough so it reduces the voltage requirements on the choice of the capacitor.


texts: Finding the transfer function of this RC circuit

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I have the following circuit and I need to find the transfer function:

simulate this circuit – Schematic created using CircuitLab

Considering the position of \$V_{\text{out}}\$, it looks like I can combine the \$R\$ and \$C\$ in parallel both above and below \$V_{\text{out}}\$ and then use voltage division to get the voltage across the bottom \$R\$ and \$C\$ in parallel:
$$V_{\text{out}} = V_{\text{in}}\frac{R||C}{(R||C)+(R||C)}$$
And this would leave me with a transfer function of:
$$\frac{V_{\text{out}}}{V_{\text{in}}}=\frac{1}{2}$$
However, I'm pretty sure this isn't correct.  Am I looking at the circuit incorrectly when assuming I can combine the \$R\$ and \$C\$ in parallel?


texts: How does this power supply schematic work?

texts:
The above is the schematic for the power supply portion of a board. As a electronics noob, I find it highly confusing and hence would appreciate some help in unraveling this schematic.

The EE13 transformer has 2 secondaries, one for 5v and another for 220v. I would appreciate some insight on the following:

1) What are the diodes on the primary input for?

2) How is the 5v secondary rectified to DC?

3) How is the 220v secondary rectified to DC using the TOP264EG component?


texts: How to check if a DC power supply is a floating source?

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Imagine a laptop power supply with 2 prongs and I'm using this as a power supply for a circuit, and the output of this circuit is an input signal Vin for a data acquisition hardware.

How can I verify if this signal is floating?
My idea is to apply continuity test between gnd of the Vin and neutral of AC in of the laptop power supply. Could it be said that then the power supply is a floating supply if continuity test doesn't beep?


texts:
I'd like to add multiple (>5) Ethernet ports to a board I am developing. Linux on the CPU has to see each port individually, be able to route the traffic among ports, and also add traffic on its own (coming from other sources, such as an LTE modem and a video source).

So far I've been unable to find a SoC satisfying all my other requirements and that has at least an Ethernet port, so I wanted to add additional Ethernet ports on the PCIe port. However, I an not even sure what I should look for: I've searched for an Ethernet switch IC and I found the VSC7514 by Microsemi which, according to an ELC2018 presentation, allows the ports to be seen as individual interfaces by Linux. However, the presenter says that only control traffic passes on the PCIe (whereas I have to send data to the switch too).

What should I look for if I want to add more Ethernet interfaces to my board? For a multiport Ethernet transceiver IC?

Thanks in advance for any help! :)


texts: How can I protect a sensitive Component from voltage spikes?

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I have some Deep UV LEDs that are about 100$ a piece. They are Very sensitive to voltage spikes, a nano-second spike could destroy one. I am building a USB powered Device with a battery, and I'm concerned that even plugging in the USB device, or turning on the battery could destroy the LEDs. I need to clamp the source current at 20ma.

What can I do to protect these LEDs?

This is the Part


texts: Addressing the cylinders of a Hard Drive

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I want to address the cylinders of a Hard Drive but I can't find a good manual of the pinout of the IDE interface. Anyone knows how to do that?

I don't want to read/write anything in the disk, just move the arm through the cylinders. And I want to do that by connecting some wires on the interface and sending some signals using a microcontroller.


texts:
I'm just an amatuer working with some electronics at home. I am trying to use an NPN transistor as a switch. 9v on the Emitter, 6v as the control on the Base to activate the switch, and I'm going to get 9+v on the Collector.

However, the voltages end up subtracting. When measured I only get 3v.

Am I setting this up wrong? I'm hoping to boost the voltage in this switch.

simulate this circuit – Schematic created using CircuitLab


texts: Why did starting a motor burn out my power regulator?

texts:
I'm driving a 12v, 1.5A (no load) motor from a 12v lead acid battery. From this same 12v source, I connected a 5v boost/buck power regulator behind a few diodes to drop the nominal 12.9v from the battery to ~11.5v to keep the voltage on the regulator in spec. Off the 5 volt, I power a Raspberry Pi 2 (drawing about 200mA), which then closes a relay to power the motor.

The RPi2 starts great off the regulated voltage, and independently the motor works great off the battery. When I hook it all up, however, and the relay is closed, the RPi2 shuts off. The 2nd time this happened during a test, it appears the power regulator got fried, as it no longer supplies 5v.

I'm guessing the motor draws too much current to start, dropping the voltage too much on the regulator. But why would this burn out the regulator? How can I prevent this from happening? Would a large cap across the power regulator input save it?


texts: 5V DC 500 mA adapter run 100 feet to web cam

texts:
I am using a GUCE51 USB extender 100 feet from my computer to power a web cam. The extender uses a 5V DC 500 mA power supply.

Option 1: Plug the power supply into the 110V AC on the inside and run 5V DC out to the extender.

Option 2: Run 100V AC to the power supply at the extender.

With Option 1, if I use good copper wire will I have enough power at the end of the run to power the extender?

Extender
Logitech Webcam C930e Web Cam


texts:
I designed a circuit with SIM868 module, and i followed the recommendation from datasheet to unsure suffusion current.

The main power supply is getting from VCC:12V source converted to 5V by an DC-DC step down converter that can output up to 3A, after that the voltage is reduced by tow diodes that also have output current up to 3A.

The following is the power supply circuit with battery charger:

And this is the module circuit diagram

I  wanted to test it and a problem occured. When I turn on the module, it automatically powers off after a few seconds.and sometimes if i remove SIM card or detach antenna, module stays on, So, I assume it powers down after it connects to network. and that can be because of power lack.

For that i added and external power source 3.7V that can output also more than 2A that is recommended by datasheet connected directly to module VDD pins, but the same problem occurs.

Did anyone have a problem like this and knows how to solve?

Updates:

I checked with the oscilloscope and I found that when the module tries to connect to the GSM network the voltage drops from 3.7 V to 2.75 V, even if I directly connected the power supply to the VDD pins of the module.

Oscilloscope configuration:

500mV / division
20us / division


texts: What is STM8 hardware and software interrupt latency?

texts:
Just have a first look over the STM8 lineup to compare its performance to AVR which is well know for me now.

One of my the big complain to AVR was the slow reaction to interrupts especially in C compiled code. To describe the problem please see the C code:

ISR(INT0_vect){
    array_p = (array_p+1) & 0x0F;
    array[array_p] = TCNT0;
}

This compiles to a huge ASM:

ISR(INT0_vect){
  b6:   1f 92           push    r1
  b8:   0f 92           push    r0
  ba:   0f b6           in  r0, 0x3f    ; 63
  bc:   0f 92           push    r0
  be:   11 24           eor r1, r1
  c0:   8f 93           push    r24
  c2:   ef 93           push    r30
  c4:   ff 93           push    r31
    array_p = (array_p+1) & 0x0F;
  c6:   e0 91 00 01     lds r30, 0x0100
  ca:   ef 5f           subi    r30, 0xFF   ; 255
  cc:   ef 70           andi    r30, 0x0F   ; 15
  ce:   e0 93 00 01     sts 0x0100, r30
    array[array_p] = TCNT0;
  d2:   86 b5           in  r24, 0x26   ; 38
  d4:   f0 e0           ldi r31, 0x00   ; 0
  d6:   ef 5f           subi    r30, 0xFF   ; 255
  d8:   fe 4f           sbci    r31, 0xFE   ; 254
  da:   80 83           st  Z, r24
}
  dc:   ff 91           pop r31
  de:   ef 91           pop r30
  e0:   8f 91           pop r24
  e2:   0f 90           pop r0
  e4:   0f be           out 0x3f, r0    ; 63
  e6:   0f 90           pop r0
  e8:   1f 90           pop r1
  ea:   18 95           reti

As you can see there are a lot of 'extra' pushes and pops.

To this inefficient (in my opinion) code I should add 7 more cycles of core latency:

I hope that STM8 can be faster for some reasons:

hardware support of nested interrupts with programable priority,
hardware (hopefully) support of accumulator, status, X and Y registers preservation.

In the reference datasheet I found these words:

So as I can see - those pushes will be performed by the hardware so it will be hopefully faster. But there is no informations about how much cycles it will take.

I wasn't able to find this information in the Internet as well.

So the questions are:

What is the actual hardware latency of interrupt response for the STM8 CPUs (the value estimated as 7 cycles for AVR)?
What is the typical C code latency? More sharply: can I hope that STM8 C compiled code will be more efficient than AVR one at this point?


texts: How to Get IP address from MAC Address using ESP8266 wifi Module

texts: I am trying to use my esp8266 to discover several WiFi devices (sensor) in my home. I only know these devices MAC address, and I need to send TCP packets to their IP address. Using RPi, I can do that using ethernet and ARP protocol. But I cannot find similar command in ESP8266. Can you guys enlighten me, ideas about how to get list of devices IP address from router (similar like entering 'arp -a' in Windows )? Or can I directly find a device IP address from their MAC Address?


texts:
Considering the last question in the image above:

  What benefits does the LUT offer over discrete logic implementations ?

I was thinking that an LUT operation is a fixed time event something like O(1). I know that you can't use that metric to describe things on an FPGA but I was wondering if there was a similar metric ?

In addition to that would the benefits be that the LUT is faster than the discrete logic since a "computation" of the result is not necessary?


texts: Magic number in TI white paper "Estimating MOSFET Parameters from the Data Sheet"

texts: I'm reading through a white paper titled Estimating MOSFET Parameters from the Data Sheet (PDF), published by Texas Instruments in 2002, and in section "A3. Gate threshold and Miller plateau voltages", the equation at the top of page 2-43 contains a magic number "-0.007 V/°C" for the temperature coefficient (TC).  I'm wondering if anyone knows where this value comes from, or perhaps knows the method that was used to arrive at this value. (NB: The MOSFET that's being used for the example is IRFP450; see the first paragraph on page 2-40.)


texts: Is current calculation in copper wire for AC simple or not?

texts:
I'm trying to learn electronics by myself, and I'm starting with simple current calculations. Let's assume we have a straight wire of length L connecting a source and a sink. I know the voltage (V), and for finding the current I need to apply Ohm's law:

$$I = \frac{V}{R}$$

This formula works fine for a DC source, and it's an easy one. What happens when one has an AC system? I saw that the formula changes to:

$$I = \frac{V}{Z}$$
where Z is the impedance, which is a complex number. This formula is a new universe for me because of this complexity. Or at least that's how it looks when trying to learn it.

From this website I saw that one could calculate the impedance at different frequencies, but AC also has to do with magnetic fields as well, right? There are two issues I don't understand yet:

Why is the impedance a complex number and what does the imaginary number suppose to reveal?
Is the medium around that wire changing the current calculations due to the magnetic field? If so, how does it get into OHM's law?

I know it might sound stupid to most of you, but for me is not easy to understand.


texts: How to smooth changes in *current* in a current meter?

texts: I have a milliammeter I'd like to debounce with an \$f_c\$ of say 0.1 Hz (10 s) to where it reads a mean average rather than however fast the needle moves, dampened only by physics. Vcc is about 8-9 V dc, and the load circuit under test series equivalent resistance varies from 50 to 330 Ω.


texts:
This is a follow up to my question from yesterday about my schematic Please review my RGB Controller
I've fixed the incorrect DC jack component that was present in my previous question, along with adding the ESP caps across the regulator and the ATTiny's VCC and GND.
Now I've made my board design, and as this is my first board design I want to make sure that I've done it correctly. I followed Jeremy Blum's tutorial to learn how to lay everything out and route the traces, and I've also ran the DRC for the board house I'm going to use (OSHPark) and everything is OK.
Before I get it printed I wanted to run it past you guys to make sure that there's not something I'm missing, or something that the DRC missed.

Here is the schematic, board, and the BOM (the BOM is incomplete due to Design Link being down right now): https://www.dropbox.com/s/t01ht6c0a93fs54/RGB%20Controller.zip?dl=0
Comments, suggestions, and critique is welcome!


texts: What are the trade-offs of transmission bands?

texts: If I were designing an RF circuit how do I determine what band the circuit should operate on? What are the trade offs? and why is the higher the frequency the lower range? It is quite un-intuitive for me since energy increases with frequency which should give a greater coverage or is it all dependent on the power of the transmitter?


texts:
In the LM386 datasheet it's stated that "If a capacitor is put from pin 1 to 8, bypassing the 1.35 kΩ resistor, the gain will go up to 200 (46 dB)".

I don't understand how this capacitor could bypass the resistor. I've tried simulating this scenario in EveryCircuit and current keep flowing in the resistor and it makes sense to me since DC won't flow into the capacitor.

They make it sound like by adding this capacitor the resistor will be shorted but I don't see how this could happen.

What are we trying to achieve in term of current/voltage flow here by adding this cap?


texts: How to find which one is master/slave? - PIC

texts: Im using PIC24FJ64GA002 microcontroller interfacing with EEPROM(24C256). EEPROM's SDA and SCL pins are connected with respective PIC24F I2C1's SDA and SCL. All other pins of eeprom are grounded. Here i have EEPROM address that is 0xA0. Now, how to find which one is slave and master? Is PIC or eeprom? I've heard which has clock that is a master. Both have clock pins.


texts: Resistance and Inductance of a ceiling fan motor needed to spec snubber

texts:
I'm looking to specify (well, suggest) a RC snubber network for someone over on diy.se who is having EMI problems with his ceiling fan knocking out his TV briefly on turn-off:

https://diy.stackexchange.com/questions/56205/why-would-turning-off-a-ceiling-fan-via-a-wall-switch-causes-3-seconds-of-tv-sig

Thing is, I cannot find any information on the winding resistance and inductance of a garden-variety ceiling fan motor.  Is this something I'd have to measure myself, or has this ever been specified or measured for a typical US ceiling fan motor?

EDIT for those who haven't read the link: the fan turning off causes the TV screen to go blank (no picture) for a few seconds, but the TV stays powered all the while.


texts: I'm trying to measure relativistic speeds with an FPGA — are my results legit?

texts:
I've been teaching myself FPGA programming in Verilog over the past year during the COVID-19 lockdown.
I found a discussion of whether it was possible to measure the speed of light using an Arduino or other microcontroller and the consensus was that the processor speed was too slow and there were too many outside factors like system interrupts.
I figured an FPGA would be well suited to this task and it would be cool to see if I could directly measure the speed of a signal through a wire, which moves at something like 0.85 the speed of light. I've gotten code working on a DE10-lite development board that does this, but I'm having some issues understanding the results. I'm really looking for feedback on whether my approach works at all and what to look out for.
My code is very straightforward. A state machine starts in IDLE until a button press moves it to state "COUNTING." In COUNTING an output wire "measure_outW" is raised from 0 to 3.3 V and then a 100 MHz always block increments a register ("measure_counterR)." This always cycle continues until an input wire (measure_inW), which is pulled down to ground by a 12 kΩ resistor, goes high. Measure_outW and measure_inW are connected through the test object, a long spool of wire. So the number of 100 MHz cycles it takes for the signal to travel from measure_outW to measure_inW (through the long spool of wire) is recorded by measure_counterR.
The state then moves to "REPORT" and the binary value in measure_counterR is converted to binary-coded decimal and fed to a UART which displays it on a PC. (I chose this setup just to get practice using a UART in Verilog.)
I used a fresh roll of 24-gauge wire-wrapping wire as a test object. It's advertised as being approximately 305 meters in length. I get values around 264 clock cycles for the travel time. Now this is with a PLL clock of 100MHz. Another roll of the same wire gives me values around 274 so I feel I'm really measuring something.
Question 1. Does an always block, that runs at posedge of a 100MHz clock, occur at 100 MHz or at 50 MHz (because it's just the posedge)? Sorry, I don't have a scope that can handle these speeds. If it's 100 MHz then in each clock cycle the signal moves 0.85  x (3x108 m/s) * 1x10-8 s) = 2.55 m. It takes 264 cycles to get through the spool so 2.55 m x 264 = 673 m. This is more than twice what I'd expect.
Question 2. Is it legit to measure very short time intervals this way? Does the PLL clock synchronize itself across the FPGA so everything is simultaneous? Or does it keep the phase across the device, at the expense of the actual absolute number of cycles?
Question 3. The values I get move around a bit, and are affected by the position of the spool of wire and its feed-in wires. I'm surprised it isn't a fixed number of clock cycles. Why does it vary by about + or - 10 cycles? I know oscillators can vary ("jitter"), but does this manifest over such short intervals (i.e., only 264 cycles)?
Question 4. I've measured two different spools of wire with different values. But when I combine them into one long test object the resulting time is a somewhat less than the sum of their individual times. Is there a capacitive or inductive effect happening? I'm just turning the line from low to high-- not sending pulses so it's not an AC signal.


texts:
An enhancement mode Mosfet's current-voltage equation in saturation mode is given by:
$$I_D =  \frac{\mu C_{ox}L}{2W}(V_{GS}-V_{th})^2$$

The graph:

My question:
I studied that the transfer characteristics can be obtained as long a \$V_D > 0\$. However, isn't it incorrect to just assume that the MOSFET is in saturation?


texts: Can the Nyquist sampling rate also apply for the human eye the same as in electronics?

texts: In electronics the Nyquist sampling rate shows you the maximum frequency that could be sampled without aliasing.  So if the human eye is able to see 24fps does it mean that you can see all the information below 12fps?


texts: How to output downsampling bus in single stream on fpga? (verilog)

texts:
Im working on a block which implements downsampling.

In general it not hard at all to do simple downsampling, all I need is the factor which I should downsample by, and the data input, Im just using counter and delete all the samples except every n'th sample.

here is my code:

`include "config.v"

module downsample (
    input                           clk,        // system clock
    input                           rst_n,      // Asynchronous reset active low

    input                           div,        // input valid
    input       [`CRD_WIDTH-1:0]    din,        // data input
    input       [7-1:0]             factor,     // downsample factor

    output reg                      dov,        // downsample output valid
    output reg  [`CRD_WIDTH-1:0]    dout        // downsample data out
);

    reg [7-1:0] cnt;

    initial begin
        cnt  = 7'h01;
        dov  = 1'b0;
        dout = `CRD_WIDTH'b0;
    end

    always @(posedge clk or negedge rst_n) begin : downsampling_logic
        if (~rst_n) begin
            dout    <= `CRD_WIDTH'b0;
            dov     <= 1'b0;
            cnt     <= 7'h01;
        end else begin
            if (div) begin
                cnt     <= cnt + 1'b1;
                dout    <= `CRD_WIDTH'b0;
                dov     <= 1'b0;
                if (cnt == factor) begin
                    cnt     <= 7'h01;
                end
                if (cnt == 7'h01) begin
                    dout    <= din;
                    dov     <= 1'b1;
                    cnt     <= 7'h02;
                end
            end else begin
                dout    <= `CRD_WIDTH'b0;
                dov     <= 1'b0;
                cnt     <= 7'h01;
            end
        end
    end
endmodule

and the output from the block looks like this:

In this example the factor=4, and everything work as expected.
So what is my problem?

I want the output to be in single stream, I dont want the 'dov' flag to behave like a clock once up and once down.. once the data is ready I want all the data to out continuously.
I prefer not to use FIFO for it.

Thanks


texts: Two batteries in parallel by a long cable

texts:
I want to build a system where I have a solar charger connected to one 12V battery, which is then wired in parallel by a long cable (30 meter, 2.5 mm2) to the other battery.

Will both batteries eventually be fully charged, or will the battery on the long end have a lower voltage/charge due to voltage drop in the cable?

I am trying to understand the relevance of current in the resistance of the cable. As the difference in voltage between battery A and B is being reduced, the current on the cable should drop - and this will reduce the voltage drop due to resistance in the cable, I am assuming?


texts:
I am controlling Arduino from my phone through Processor program which sends commands to Arduino via USB cable. Now i need to put Arduino lets say 10 meters away from the PC. I still didn't get the difference between Xbees and Wifly.

I am trying to establish a simple wireless serial communication between PC and Arduino.

Is a Wifly shiled enough to achieve that?

Or pair of Xbees?

Which is easy to establish communication?

Thanks,

By the way i want to mention that i don't have access to the router. I just share Wifi in an apartment but the router does not belong to me and i can not access that.


texts: 12V solenoid drawing more current than it needs

texts:
I'm fairly new to practical electronics so I apologize if any of this is obvious.  I am currently trying to use a microcontroller to control the energizing of several 12V solenoid valves using a PC power supply to provide the 12V for the valves and 5V to power the microcontroller.

The issue I'm getting is that the valves appear to be drawing a lot more current than they require to operate.  I've measured the voltage and current going through the valves and they read as 4V and 12A.  They are rated at 12V and 0.5A by the manufacturer.  I can't explain what the problem is or where it resides.  I have verified that the proper 5V is being output from the microcontroller and the NPN BJT used for the switching has a 300-ohm resistor on its base.

Any help would be appreciated, this project has definitely lagged as a result of this issue.


texts: Earth potential rise, touch voltage, step voltage

texts:
Substations have buried earth grids, to control voltage rise in case of a fault. This is to protect people against electrocution.

The terminology for earth grid design includes:

Earth potential rise
Touch voltage
Step voltage

What's the difference between these three terms?

[I have an answer written for this already. Will wait a period for other answers, before posting mine.]


texts: Can a DC motor with obstructed movement be damaged?

texts:
I am trying to build shades, which should roll up or down, controlled by a DC motor. This motor can only be turned on or off (1/0 to turn it on/off). Also, it should be noted that the microcontroller behind this is a NI-SPEEDY with a daughter board that provides relay switches (not a range from -1 to 1).

The first thought was that when given a 1, it should roll it up then stop. And when given 0, it should be turned off and let gravity pull it down.

The problem is with stopping: I can't figure out a way to make it stop when it reaches the top. So I thought I should leave it on. But since it won't be able to rotate, I guess it might be damaged. How critical can such a thing be?

UPDATE:

This is the datasheet of the DC motor:

Matsushita Electric, Japan
13.2V DC
MYT-5AC8

Similar to this one and that one.

A 12V battery is plugged to the daughter board of the microcontroller. The motor gets 12V DC, but I'm not sure about the current that is drawn to it.

The battery specs: 12V 7.5Ah/20hr

I tried keeping it plugged to the battery for a minute, and the heat produced was negligible, but I guess keeping it for more than that will fry it.

UPDATE 2:

After trying almost all of the technically possible solutions provided, it turns out all the sensors we put were mechanically not possible to set up. They either were never activated or not reliable. Also, the circuitry involved seemed too complex (you might have noticed I'm a beginner) for two states (0/1). And since the controller is a requirement, it was not possible to use PWM or any other technique to control it via software.

All in all, this was very helpful, I learned a lot. Now let's just hope the motor will not be damaged by the time it is presented to the jury.


texts:
can someone suggest me a way to convert .s2p (touchStone) files to spice models.
I have checked with various sites like www.emwonder.com and www.spice-club.com
suggested in some Forums but it really didnot help me


texts: Simple and powerful audio amplifier around BA4558?

texts:
I have two BA4558 ICs from an old home stereo. I tested them with simple negative feedback circuit for each channel and with power supply of +/- 6V. The speakers I used are most likely with 8 ohm impedance but that is just a a guess.

The idea is two put together a simple and loud battery powered boombox for a mp3 player. Some hiss or minor distortion is ok. No need for a volume control as mp3 has that.

I guess I could bring the supply voltage up to -/+ 18V as mentioned in the datasheet. A friend of mine suggested adding some capacitors around the opamp and also to add some push-pull transistors after the opamp.

Any other ideas?

http://www.datasheetcatalog.org/datasheets/70/233498_DS.pdf


texts: Need help understanding how a transistor works in this circuit

texts:
The circuit diagram I've attached has the direction of current flow represented by red arrows. It's the solution given for the 2006 Pennsylvania State Circuit lab competition for Science Olympiad from here: https://scioly.org/wiki/index.php/Test_Exchange_Archive#Circuit_Lab

I can't wrap my head around why Q1 has current going through it, but Q2 doesn't. It seems like current going down through R3 should engage the base of Q2 and current should flow down through the LEDs and through Q2...

Please help, so confused!


texts: How Zero Crossing optoisolator to work with 220VAC?

texts:
I want to use a H11AA1 to detect Zero Crossing, but I am not sure how circuit should look like. How much voltage should LED receive inside H11AA1?

Here is datasheet:
http://www.vishay.com/docs/83608/h11aa1.pdf

By my calculation, please correct me if I am wrong.
Forward continuous current from datasheet 60mA.

Resistor should be 220/0.06= 3.6k
With wattage 220*0.06=13.2W

Here is some circuit which I found but not seem legit...


texts:
I plan on using a barebones Atmega168 running an Arduino sketch to drive two stepper motors and a heater. To interface with the steppers and heater I want to use 4 PWM pins. I will also have an SPI connection to a host controller so that the host can request a certain amount of steps at a given speed or demand that the heater be heated to a given temperature. To drive the stepping action I will need an interrupt every 100 micro seconds or so.

Now to do this I will probably need and open timer channel (or am I wrong), I know my 4 PWM pins will be using 4 of the 6 available timer channels, but will the SPI be using any and possibly cause some issues?


texts: What kind of relay do I need for for 12V source with a 5V control voltage

texts: Trying to figure out which relay I need for a project I'm working on. The source is a 12V battery, and I'm looking to turn on a 12v solenoid using a relay. I want the control voltage on the rely to be 5V, so I need a 5v relay capable of switching 12V. Found this relay but I'm not sure if I'm looking at it right. Would this relay be capable of doing what I want?


texts:
I am trying to bias a 50Hz 5V(p-p) AC signal (by a signal generator) by +2.5V to connect it to an ADC. I'm measuring both input and output voltages using the measuring function of a GDS-2102 oscilloscope. I've used the following circuit:

simulate this circuit – Schematic created using CircuitLab

However, I'm not getting a 2.5V bias. It is around 2.8V. If I increase the resistance to \$1M\Omega\$, the bias decreases to around 1.6V. I don't understand - shouldn't the bias be determined by the voltage divider? And since the resistor values are the same, why am I not getting exactly 2.5V?


texts: How can I know the rated current of a 6v transformer?

texts:
I've an old bulk transformer. It is 220V/6V.

I Connected it to the basic rectifier circuit with a voltage regulator (7805) so that the output voltage is 5V.

The transformer produces about 8V DC across the smoothing capacitor.

When I connected a 20 ohm resistor as a load, The voltage across this load resistor was about 3.75 volts.

I connected a 30 ohm resistor as a load, The voltage across this load resistor was 4.25.

I'm not sure but I think the drop in voltage is due to I'm exceeding the rated current (maximum) current that the secondary side of the transformer can handle.

My first question is How can I know or measure the rated (maximum) current of this transformer?

Second question: If the rated current does not cause the problem, What could be the reason?

Thank you very much,


texts:
For a couple of days I have been learning about SPI and decided to give it a go with 2 small devices.

DEVICE 1: Atmega328p (MASTER)
DEVICE 2: MFRC522 (SLAVE)

As far as I understand:

master sets SS pin low
master moves data to SPDR
as soon as data gets in to SPDR clock starts transmitting and data shift out
at the same time SLAVE shift data out too
so by the end of 8 clock pulses SLAVE received 1 byte and master received 1 byte too
SS pin goes high again

Scenario #1
I am sending the address byte to MFRC522 from Atmega328p, and expecting a reply. According to the documentation, the first response from SLAVE is "X" I take it as 0x00.
On the next byte sent to the SLAVE, I receive the response from the first byte I sent, and so on until the end.
Since it has some kind of offset would I need to send 0x00 to the slave to read that last byte of information?


texts: using the clock of FPGA in system generator

texts: I have designed a circuit in system generator. I am using a FIFO at the output. I want to connect the we pin of FIFO to the clock of FPGA, but I do not know how should I do it in System Generator. In another language how can I access to the clock of FPGA in System Generator. Can anyone help me?


texts: Coupling coefficient of microstrip resonators

texts:
I am working in HFSS and I'm trying to determine the coupling coefficient between two microstrip resonators (k) so that I can design a filter using a certain resonator shape. I have the formula I need. I just confused as how to practically measure it. I have seen results like the ones below

:

They use the formula:

where F1 and F2 are transmission peaks.
What I'm trying to understand is how should I fix the input and output coupling to generate graphs like these


texts: is this small signal equivalent circuit of mosfet amplifier correct?

texts: We are given an assigment about mosfet common source amplifiers and we are given this circuit. I drew its small signal equivalent circuit but I am so unsure about placement of ro(transistor resistor). Can you tell me if it is correct or not and help me if it is not correct


texts: What is the meaning of performing logical operations on two numbers?

texts:
If we are to consider two Boolean values, the logical operations on them make perfect sense. But what would it mean to perform AND/OR/XOR operation on two binary numbers?

I am learning Assembly level programming (in ARM7) and I'd to write a simple code that performs logical operations like AND,OR,XOR on two Hex Values.

EDIT: My question is not about the procedure of performing such operations on numbers. I'm concerned about the logical implication of such operations.
I came across a block of code that swaps the value of two registers without involving the third register or memory. The algorithm was to perform XOR operation on the numbers.
A(XOR)B = A'B + AB' ,
What actually is the meaning of A'? If A were a Boolean Value 0 or 1, A' would have been 1 or 0 respectively. I don't understand how I can extend the same logic for two numbers.


texts: PMDC motor: how much is voltage reduced if the resistance produced by commutation system is eliminated?

texts:
I have made a PMDC motor. The resistance of the coils is 0.25 ohms. But the commutation system is very resistant. It adds more 0.85 ohms to the armature resistance. So, the total resistance becomes 1.1 ohms through the commutation system.
The motor needs 14.80 volts and 5.75 amperes to work properly, using the same commutation system.
If the commutation system is replaced by electronic sensors, would the over resistance added by the commutation be eliminated? If so, what amount of lesser voltage would be needed? my calculation (according to ohm law) concludes that this motor needs only 3.363 volts if the over resistance caused by the commutation system is removed. As:
Total resistance/ coils resistance= 1.10/0.25=4.4;
Present voltage/4.4=14.8/4.4= 3.363 volts.
Is this calculation wrong?


texts:
I am working on modifying electric old IKEA Galant table(that's the only label i can find on it, it's a pretty old model. And it is surely not IKEA Bekant which has more resources available online). I would need some help to simulate button presses using microconroller(ESP32).

Basically, the table has two buttons - up and down. Whenever the button is pressed it pulls down to GND and the table moves (as on a schematic below). It is about 5V logic sitting on the button before it's pressed.

So I'm thinking about adding a microcontroller which will simply pull down to GND whenever the table needs to be moved. On the picture below two little gray lines are indicating where the microcontroller's pins would connect.

My problem or lack of knowledge is how to add that microcontroller connection? Should it be behind the diode (since microcontroller has it's own ~5V), or should there be any pull up resistors to make sure the mcu doesn't trigger low signal whenever powered up or down?

Any help would be highly appreciated.

Updated:

I have some IRLD120 MOSFETs lying around, so here is updated full diagram of my "kitchen" with MOSFET as Tom has recommended:


texts: Diode Bridge in Simulator not behaving as expected

texts:
Hi I have a Diode Bridge as outlined in the image below. As you can see I am getting a negative voltage on one pair of diodes instead of this voltage being flipped to positive.

Can you see anything wrong with my design or does it look like the simulator program getting it wrong?

Using Every Circuit Simulator on Android.


texts: Is it possible to grub the main code from STM32 with built-in Oximeter

texts:
I have this infra-red oximeter  and it is based on STM32F030C8T6 and  its PCB has
pin headers place labeled as
RST,VCC,DIO,CLK,GND
and RX0,TX0 as shown in photo.
Is it possible to grub  the main code or any way to communicate with it , note I don't have ST-link.


texts: What is the cause of voltage phase shift in a power system?

texts:
What element(s) cause the phasor voltage to shift in a power system?

Why does the voltage phase angle increase with distance in a power grid?


texts: Is impedance matching a requirement for CAT-5e traces?

texts:
I'm building a patch-board for CAT-5e cables, whereby any pin can be re-wired to any other by a set of jumper cables. This is for testing black-box systems where weird things have been done to Ethernet sockets in order to make it difficult for someone to just walk up and plug in a laptop.

I'm in the PCB design phase, and have the following design in mind:

Here's the design I have in mind:

The board is using 0.254mm traces, and the total length of each trace is no more than 25mm. I've alternated the traces on each side of the board to increase clearance between them, and hopefully the PCB itself should provide a little insulation against EM leakage.

I'd like to know if impedance matching is going to be an issue on a standard 10/100 Ethernet link, across this kind of design. Obviously the outer traces are currently about 50% longer than the middle one.

Any other recommendations on improving the design would also be welcome.


texts: How does it work: smartphone pixels are turned off when heated

texts:
I saw this video:
https://youtu.be/urbhA37a70c?t=1m45s

In the video you will see that the pixels of a smartphone are turned off when heated. The pixels are turned back on again when they cool down. Does each pixel has a temperature sensor? :o

I wonder how it works.


texts: Altium - Cannot Select/highlight components on PCB

texts:
this issue arises out of no where periodically. Very frustrated!!

Suddenly I am unable to select any component on the PCB board in order to move it/right-click (the grey box doesn't appear).

I have tried selecting a box around the component but it does not highlight it.
I cannot even right click to see properties.
It is as if the component is gone

I can however, with 'cross select mode' in tools enabled, select the component in the schematic, come back into my pcb design and click 'reposition selected components', however once the component is placed i cannot then click back onto it to adjust or do anything.

After it happens i close it down, go back to an earlier save that i know was working fine, and the problem persists.

Can anybody think of any reason why it would do this??

maybe i have clicked a keyboard shortcut by accident?


texts: SI8751 isolated mosfet driver and msofet NVD5C668NL

texts:
I need help for my very first application with power mosfet
The goal is "simple..": create a SSR for switching a generic DC load with variable power supply from 5V to 48V and max 25A. Isolation isn't a request but I would use it. Switch must be high side.
I am study the silabs SI875x isolated driver. I am not sure if this drive can be used the switching the mosfet If I'm not wrong the switching time is very long (milliseconds).
I need help to find a solution that allows me to speedup the MOSFET switching.


texts: How should the low frequency schematic of this amplifier look like?

texts: I know the model for a transistor at low frequency (first pic), but I never thought of a more complex schematic like this one. It also specifies that Cc is very high, that means it's not going to be a short anymore?


texts: Connecting a USB 1.1 host to a host PC (pretending a PC is a gamepad)

texts:
I would like to connect two USB hosts together and was wondering if a USB bridge is the correct tool for this.
Specifically, one device is a video games console that uses USB 1.1 for controller input. Some similar consoles had devices developed for them (custom PCBs or micro controllers) that plug in to the controller port and pretend they are a controller, forwarding or translating input (such as connecting a different type of controller or enabling wireless gamepads).
I am trying to connect the USB controller input on the console to a PC where I would write software to handshake & forward commands but I'm not sure the correct way to physically connect the devices.


texts:
I am trying to amplify audio from an electret microphone using an LM386 audio amplifier board.

However, the output of the board is very grainy and the audio is distorted.

Is there any way I can improve the audio quality, or the microphone gain?

I have used a 27k resistor from mic+ to a 9v battery to power the microphone.

I will attach the diagram of what I have done below.

Edit - I have now looked into using a coupling capacitor on the input but there are a few schematics and I am still unsure.  I have attached the images below.


texts: What would be the gain of the A circuit (A unit in feedback) in the following circuit? First, what would be B? Merely the short connecting Vo and Q2?


texts:
I have bought "AOCJY2-5-100.000Mhz-E-SW" OCXO which datasheet is available here.

I use this circuit to change the output frequency with a 10K variable resistor. However, by changing the value of the variable resistor the output frequency is fixed (I need to have an 80Mhz oscillator).
What is my mistake?


texts: How much energy is required to charge a battery to 50% vs 100%?

texts:
When I go hiking, I only recharge my phone to about 80% from my backup supply because I know it gets harder and harder to push more energy into a battery the closer it gets to full capacity.  So I am roughly assuming I could charge my phone a few times to 70%, versus 1 charge to 100%.  (The higher the voltage in the battery the slower and less efficient recharging seems to be.  Even how superchargers for Tesla can charge to 80% almost instantly, but takes considerably longer to reach 100%)

I was wondering if anyone knows what that graph looks like.  Total energy input vs percent charged.

**I know it depends on battery type and recharge rate and all that, but generally speaking, they should have a similar graph.

It won't be linear, but how about exponential? logarithmic?  or is it just the inverse and derivative of discharge?

Can I charge to 70% two times vs one charge to 100%?  Any rule of thumb to follow while on my hikes??

My efforts to search haven't been very rewarding, so I figured I'd ask.