texts:
I'm looking to recover from a rookie mistake I made while working on a 12Vdc power supply. My multimeter was reading a 11.8Vdc output off a voltage regulator, and I thought 'Hey I have a sketch that turns my Uno into an oscope'. Not a good idea. As soon as I touched the probe to the output my Arduino and laptop instantly shut down. No smoke or visible damage to either. When I plug the Arduino into a usb wall adapter the LEDs come on. I'm really hesitant to connect it back to my comp.

What should I be looking for in to test for damage? The probe was grounded and fed into analog 0.  Is this PIN toast? Is the board safe to hook back into the computer?

Any and all answers/suggestions are greatly appreciated. Live and learn I guess.


texts: maximum reverse voltage applied to a resistor-LED configuration

texts:
Consider the simple circuit below:

simulate this circuit – Schematic created using CircuitLab
LED datasheet: link
Does the applying of a reversed 36 volts to this circuit damage the LED? Knowing that the maximum current that could flow into the LED is 36V/2kOhm = 18mA (the LED can withstand 30mA forward current)
The maximum reverse voltage is 5V. Does that mean that the LED will actually blow if I applied say only a reversed 5.1V on the input?
And in case the circuit is that sensitive to reverse voltage, what are the simplest way to protect this circuit from a reverse voltage?
EDIT: I actually tested the LED and it doesn't seem to be damaged by applying 30V in reverse(applied for several minutes). Also I connected an ammeter to measure the reverse current (Fluke 87V with uA accuracy) and it shows absolutely no current flow. So what's the deal ?


texts: Is the dynamic resistance ignored in this output impedance formula?

texts:
Does the following tutorial neglect the dynamic resistance across the base and the emitter in derivation of the output resistance:?

It assumes Vbe constant and ignores the dynamic resistance? But dynamic resistance still exists even there is no change in Vbe(?) Because it says the voltage drop Vin - Vout = (I/beta)* Rsource. Dynamic resistance seems to be ignored(?)


texts:
I'm reading through Hayt's Engineering Circuit Analysis 9e and it does a fairly good job of giving the intuition for "where" the energy is going in a damped RLC circuit, but I'm hoping that someone here can help me get full closure.

Consider a parallel RLC circuit with no input and where the capacitor is initially at some non-zero i(0).

First of all, I'm hoping to clarify why the maximum voltage achieved by the system occurs in the underdamped case. Intuitively, is this because the resistor's value value is so large that most of the current will flow between the capacitor and the inductor (and thus energy is just exchanged between the two rather than being dissipated by the resistor).

If the above is true, then I am trying to square that with the fact that the slightly underdamped or critically damped case has the shortest settling time. My understanding is that settling time corresponds to the time required for all of the energy to be dissipated. If, in the slightly underdamped case, we are exchanging energy between the capacitor and the inductor in an oscillatory manner and the resistor is therefore not dissipating much energy, how does that system settle (well) before the overdamped case where the resistor (I think) dissipates a large amount of energy because resistance is low and much current therefore flows through the resistor? Or am I somehow confusing energy dissipation with the voltage here.

Generally, I'm looking for an intuitive explanation of "where the energy is going" and why it "goes away" quickest in the critically damped or slightly underdamped cases, rather than a mathematical demonstration.


texts: Home automation: Adding relays in series vs parallel

texts:
Recently I bought an Arduino Uno to discover electronics. I am a computer science student, hence the programming part is not a problem, however, I lack some knowledge about electronics.

Now I want to do some simple home automation, mainly to control the lights in my house. I was thinking about adding an Arduino controlled relay (in the central electrical box of my house) for each light I want to control.

However, for each light in my house I have a switch. Suppose, I'd add Arduino controlled relays in series with the switch (as in the figure below):

The problem is that with the relays being in series, I can only switch on and off the light if the switch is closed. Hence, like above, the switch is open and my Arduino controlled relay will have no effect.

Now, suppose I'd add the Arduino controlled relays in parallel:

In parallel, we observe the inverse problem. If the switch is open, we are able to control the light using the Arduino controlled relay. However, if the switch is closed (like above), the current will flow through it anyway, i.e. the light will glow without the Arduino controlled relay having any effect.

How does one tackle this problem in home automation systems, without the need to rewire my entire house?

PS : Excuse me if the diagrams are wrong in some way. I absolutely have no electronics background.


texts: Best way to amplify two analog signals and keep the differential sign

texts:
I have an analog sensor with two outputs. Each channel output can range from +0.4 to +0.6V. Currently I am reading them with a 16 bit ADC, and subtracting them after each recording.

It would be nice to amplify them. It would be super nice to get a single signal out. I am getting an opamp shipped to me tomorrow, two Ti TL072ACP 8 pin ICs.
My sensor acts such that sometimes channel 1 is say +0.45 and channel 2 is +0.55, but sometimes channel 1 is +0.55 and channel 2 is +0.45, it is critical I keep track of which channel is high if I were to go with a single output from my opamp.
So currently the differential voltage can be positive as well as negative. Forgive me if this is too simple of a question but I can't make any mistakes, and need to be 100% certain I have it wired correctly and keep the differential sign (+/-V) relative to the signal.

Both analog channels need to be treated the same, as each has equal weight in determining the sensor reading. It makes me nervous to call one channel inverting and the other non-inverting. Both channels measure in the same way, just give their readings under different conditions. Sometimes one is high sometimes the other is high. The sensors cannot give negative results either as they are actually 2 discrete photodiodes pointing in different directions, and each generates voltage based on exposure to light. Imagine it as a sundial that I can use to tell the "time" by reading where the sun is in the sky with the sensor pair facing East-West.
I have a 5V supply on the board the contains the photodiodes (they are actually part of a CMOS microchip) and was planning to add a tap to power the opamp.


texts: Battery Power Control with MOSFET - One Button FlipFlop

texts:
I cannot get my head around the circuit below of a Flip Flop SR switch using one push button and only MOSFETs:
The image below seems incomplete probably due to a typo (as R3 is not shown) but I believe R3 should connect Vbatt to R4.
The general concept is that with just one Push Button you are able to toggle the MOSFET Q3 ON and OFF.
I understand that from resting position (C1 discharged), the first push on the Button will bring Q1 (and consequently Q2) to conduction, thus charging C1 to Vbatt.
What I do not understand is what happens next if you push again the Button: Does the C1 bring Q1 gate to Vbatt (thus witching it off)?
I spent hours trying to understand but I am honestly lost.
Any help is appreciated.
Bests


texts:
note I know essentially nothing about solenoids

I brought this solenoid thinking that I could use it to hit an object, but when I put it to a power supply, the only direction that it would go is down. I tried changing the direction of the current but that did nothing. Is there anyway I could get the solenoid to push out instead of pull in?


texts: From a power consumption point of view, which should I use: SSR or Relay?

texts:
I'd like to find out which to use: a SSR (Solid State Relay) using TRIAC and optocoupler or a relay.

My consideration are from the point of power consumed, my challenge here is to choose the less power consumer one.

The biggest problem I found with a relay is through holding its state; the power is consumed first to activate the relay, then to hold the relay activated. If that lasts for long time, it will consume so much power.

My application is using a microcontroller that controls the flow of AC electricity that requires latching the state, what ever it is, for a long time.

So, from the point of power consumption, is the SSR (using a TRIAC and a MOC) or the relay more power hungry?


texts: Turn on relay when voltage larger then 13v

texts: I want to build circuit that turns on relay when voltage larger then 13 volts and turns relay off at 12 volts or lower  .I would like to use 12 or 5V relay


texts: When use Voltage divider in circuit analysis

texts:
I am trying to find the voltage in R2 with voltage divider, this is the schematic:

simulate this circuit – Schematic created using CircuitLab

but I can't, and I don't know how to apply the voltage divider here. What I tried to do was:

First I convert the Delta R2-R3-R4 to Y (wye), because the Voltage divider should be used in a series circuit so I tried to convert the delta to series, but that just work for find the total Resistance.

simulate this circuit

I don't know which value will take the R1 and R2 in the formula:
$$
V_{out} = \frac{V_{in} * R_2}{R_1 +R_2} \\
$$

so in this case $$V_{out} = V_{R_2}$$ I am using  $$V_{in} = 10v$$, but I can't figure out which should be the Total resistance in this case, I mean what is the value of: $$R_1 +R_2$$

I found the Voltage of R2 doing Mesh Analysis. But I don't if is possible to find that value whit Voltage Divider.

In the case that is possible or not, when should be used Voltage divider ?

Thanks a lot for any hint.


texts: Do the capacitors on the picture look broken?

texts:
I have here a CD player's board (the player is from 80s, Gründig CD 30), the player works OK first 10 seconds, after that there is loud noise (sound is still possible to recognize but is very very cracky). The capacitors [on the picture] look somehow strange to me, particularly those orange spots. Could it be the symptom of broken capacitor?

Update:
thanks for the answers, the capacitors are really not broken, with no adjustments I assembled the player and the problem is gone, no noise at all. Mystic. So those orange spots seem to be some kind of glue. Thanks for the answers once again.


texts: How to design a multiplexed keyboard circuit for Arduino?

texts:
Hi all,

I'm working on a project where I'm trying to read my calculators keyboard to know which key was pressed. I've decided over the past few days that hooking into the calculators PCB wasn't going to work since the keybaord is multiplexed, making the reading process much more complicated. So I figured, I'll design my own circuit based on the existing one.

My main problem is that I have no prior experience with circuit designing. It should be identical to the old one in dimenions and it should have all the "buttons" and holding holes at the same place. My circuit doesn't need any electrical components besides the wires, as far as I know.

My very basic and  unprofessional drawing + original PCB:

Notice that the first row has 6 buttons and the last row has a big button covering to places.

Could you share any thoughts, designing tools, tutorials that would help me with making this circuit? Thanks in advance!


texts: Program to simulate seven segment display in atmel studio

texts:
I am using Atmel studio for the programming of atmega64 microcontrollers with a Cerebot board II.

Firstly, is there a program that can simulate a seven segment display device as if I was looking at the device in front of me plugging it into a Cerebot board II?

Secondly, is there a built in function of Atmel studio 6 that can simulate a seven segment for me?


texts:
There was an assignment as follows: implement a counter which gets as an input of 8 pulses, 5 volts each, with frequency of 40K Hz, without using counter block, or any IC components. In the output there are 8 diodes, with each pulse another diode should be activated, such that with the first pulse - the first diode get's activated, with the second pulse, the second diode get's activated, and so on.

my idea of implementation was to use FF's to act as a shift register - on the first pulse, the first FF passes the 5 volt and lights up the first diode, on the second pulse, the second FF get's activated and lights up the second diode, and so on.

I tried to implement a FF of my own, using logic gates, but for some reason, it doesn't work. When I tried using the FF component which multisim offers, I linked the FF's in a row, but the second FF get's contaminated too soon, before the second pulse arrives - thus activating the diode before the time. perhaps anyone could give me some advice on what am i doing wrong:

what's the problem with the way I connected the FF's in the first picture?
why does the logic gate implementation of my FF doesn't work?

Full design:

the simulation result of the blue point X marked in picture (1) - the AND gate output:

mulation result of the FF's as depicted in picture (1):

NOTE: the second pulse arrives after 2.5x(10^-5) sec, but the second FF (depicted in green in the 3rd picture) gets contaminated and activates the diode after 2x(10^-9) sec

and last, my FF implementation using logic gates which refuses to work and outputs zero all the time:

Thank you very much for you time and attention!


texts: Load cell behaving weirdly. Output magnitude of force depends on which side is held and which side force is applied

texts:
also asked at: https://forum.arduino.cc/index.php?topic=670246.0

I have a generic load cell (image) and am using Hx711 which is connected to arduino. The code is from Instructables.

When I fix and apply the load as in case 1, it shows positive force. But when I do as in case 2, it shows negative force. I haven't flipped the part just rotated about Z axis.
Here is my question: Shouldn't both cases show same force considering region of 'strain gauge 1' is at tension and region of 'strain gauge 2' is at compression? Am I missing something?


texts: Can a 50 Hz, 220 VAC transformer work on 40 Hz, 180VAC?

texts: I am designing an AC to DC converter. My power source is a single phase synchronous alternator that has a voltage range of 170~260 VAC and a frequency of 40~60 Hz. Can i use a transformer designed on 50 Hz and 220 VAC to work on my alternator specs mentioned above?


texts: Initializing the ESC through microcontroller

texts: I have an esc and a brush less dc motor. the connections are given in the pictures. i have written the program for the micrcontroller such that it send 1ms high 19ms low pulses to esc for 5 seconds. then i change the high duration to 2ms and low to 18ms. but nothing happens at the esc not the motor. the motor doesnt rotates. i tried 1.5ms high too, but nothing happens. is there any initialization of esc, so that then pwm is sent to it for rotating the motor. i mean that is there any serial communication involved in it? if yes then what are the instruction?


texts:
I found the following circuit interfacing with a GPIO input on an MCU that has an internal pull up resistor. The GPIO is being used to detect the state of the push button. I have two questions regarding this circuit:

How does the inductor debounce the push button?
What is the purpose of the diode here? If it is a flyback diode, should it not be connected across the inductor instead so that the inductor can dissipate energy?

Any help is much appreciated!

EDIT:
The GPIO is now called out in the image.


texts:
i built this DC motor power amplifier to drive the motor in both directions using an analog signal (from -1 volt to 1 volt via the potentiometer ) , the motor i use is rated for 24 volts and draws around 400mA at no load , however, when i tested it only one direction works fine ( the NPN TIP142 side) with no significant heat , the other side however doesn't drive the motor all the way to 10 volts and the PNP transistor becomes hot real fast, i replaced it with another tip147 but still got the same results, any idea what maybe causing this?

Update 1: I inserted a resistor in series with the PNP gate and it enhanced the motor's performance , however the oscillations still exist , should i also consider an RC snubber ??


texts: How can I set up a chained DAQ system with small off the shelve boards?

texts:
I'm building an exoskeleton in a student team and we're having some trouble finding the right prototyping system for our electronics system. All of the shelve systems are either too slow or too big. The setup is simple. Each leg has 3 joints and each joint has an array of sensors. These sensors have to be read by a DAQ system and then sent to a target computer running a control loop (simulink or labview).

NI has offered us some help by using their MyRIO's to acquire all sensor data where we can then send it to a CompactRIO over CANbus. However, we are unsure if that's fast enough. Each joint has to send 500bits per sample and we really need to keep the latency as low as possible. In total we need to sample at 200Hz. From what I've heard and read is that the CANbus won't be able to supply us with a fast enough connection due to all kinds of overhad. Perhaps it is possible to chain multiple CANbusses in parallel?

We looked into EtherCAT as well but all the data acquisition systems are huge and industrial. We need to keep it small.

Designing our own electronic boards is really difficult due to our time constraints and knowledge within the team.

So my question is what the available options are in case CANbus with NI hardware doesn't pan out due to its speed.

The requirements for the boards and overal system are:

Interface with Simulink or Labview
DAQ boards no bigger than a MyRIO
Programmable
4 Digital inputs and 3 analog inputs per board

EDIT: added sampling rate


texts: How to simulate a push-pull line in a power management IC (PMIC)?

texts:
Given a power management IC (PMIC, datasheet), two lines are internally connected to the same low-dropout regulator (LDO).
One line is directly connected to the LDO, the other is a push-pull pulled internally to the LDO.
More details:

The LDO is fixed at 3.0V with a max 60mA (or 100mA, ambiguously).
The direct line (VCC_RTC) shares the LDO properties above.
The PWROK output line is a push-pull pulled to VCC_RTC.
Unpowered resistance between VCC_RTC and PWROK settles on 5MΩ (+ probe on VCC_RTC).
Unpowered resistance between VCC_RTC and PWROK is instantly 15MΩ (- probe on VCC_RTC).
Supply voltage is 5.0V.
Datasheet

My goal is to approximately simulate how applying an external voltage to PWROK affects VCC_RTC. To do that, I'm trying to simulate the internal push-pull.
Here is my attempt using ideal MOSFETs:

For those familiar with PMICs, what is a more realistic representation of this push-pull component when left normally high?
(If you're curious, I want to understand the effects of applying 3.3V to the PWROK line to see how the VCC_RTC line changes voltage and/or supply current.)


texts:
I have been trying to create my own CAT6 cable lengths, but have been having problems with achieving a connection.

Every diagram that I have seen online doesn't match my wires exactly.

I have an orange, blue, green and brown solid wires. When you strip the protective sheathing off, each color is twisted with a solid white wire, not striped like every diagram shows and explains.

The outside of the sheath says CAT6 and I have been using CAT6 connector but every time I make a connector, I am not registering a connection once it is plugged in.

Someone mentioned that maybe I'm not crimping down hard enough, so I even went as far as to strip down the sheathing on each individual wire to help with connections and that didn't help.

I've made sure that, when I am inserting the wire, they are not crossing.  The order in which I am inserting them into the connector is:

white
orange
white
blue
white
green
white
brown

If anyone can help, I would greatly appreciate it.


texts:
I am posting a screen shot of the abs max rating of the LPC43xx microcontroller. It states that the total power dissipation of the package is 1.5W. I am assuming that the total power dissipation means the power dissipated when all the peripherals and all working inside the MCU. Supposing I have only the I2C working how much would the MCU dissipate in terms of power. Also this chip has regulator power supply and I/O voltage supply.

Should I incorporate the power contribution from both and sum it up, so Preg+PI/O?

Will the total power dissipated be the power of the above + PI2C ?


texts: How to verify observe or check the source of AC line noise

texts:
I'm using a complicated system which reads pressure measurements and sends to an ADC. I will not go to details of the system because I just noticed a big difference due to different AC mains connections.

Below is a basic illustration of the system:

The system is always in the second floor. If I plug the AC power cord to the mains in 2nd floor I get a very noisy spiky output. Both with 2 prong and 3 prong connector. So it seems its not earth related.

But if I leave the system in the second floor and plug the AC power cord in the 1st floor I get a very clean output.

Below shows this difference. Both voltage is on vertical axis represents sensor data and scaled with factor 100.(For example 10 in vertical pressure axis is 0.1 Volt). These wild spikes are like HF noise.

I tested it many times and I'm sure this is the source of the noise.
The place in the 2nd floor has an AC motor and florescent lambs. But this happens some days. Some days not.

I mean if I use the mains power in 2nd floor for powering up the system I observe this on some days.

But if I use the 1st floor's plug there is never noise.

Something is causing noise on AC lines in the second floor.

Since neutrals are all connected in a building could it be the live is being exposed to noise in 2nd floor?

Can I measure/verify this with noise with a scope and a step down transformer? Or with an RC differentiator?


texts: Switch current sense resistor: series or parallel?

texts:
I am building a device that measures current in various ranges. For this I want to switch in different current sense resistors. To do this I see two ways: the resistors in series or the resistors in parallel.

Series:

simulate this circuit – Schematic created using CircuitLab

Parallel:

simulate this circuit

They produce slightly different values, but that doesn't really matter all that much, because I have to calibrate it for the actual values anyways.

But I am wondering if there are any inherent advantages or disadvantages of one method over the other for current sense purposes.


texts: I don't understand why this open collector not gate needs diodes

texts:
I'm trying to understand why the following circuit, which corresponds to an open collector not gate, needs to use two diodes. The circuit I'm taking about is below:

I think I understand the one just after the Vcc, I guess it's for preventing the current to flow to ground when A is high, am I right? Why can't you just remove the Vcc instead of using that diode?

I'm trying to figure out what is the purpose of the one that is between ground and B, but I don't get why is it necessary to prevent the curent to flow from B to ground.


texts: Are "fixed voltage" LDOs adjustable too?

texts:
I have a quick question...
I have purchased a 5VDC fixed voltage LDO. P/N: MC7805CT-BP
I was wondering if I can still use a voltage divider to set the output to a higher voltage.

If yes... does this mean that virtually ALL LDOs are adjustable?


texts:
I have done a fair amount of soldering with SMD components now. I can solder an 0402 size component I prefer not to. I can solder an 0603 just fine and anything bigger. But my question is, what diode packages are similar in size to an 0603 but no smaller. I am not very familiar with diode SMD packages. I am aware different applications require require different size packages for power reasons. I am concerned with board space for my application and my ability to solder them by hand.

I will need a small signal diode package(s) in the 0603 size range.
I will also need the around about recommended package(s) for dissipating ~100 mW continuously.

I am aware diodes come in MELF packages but this limits my options for zener devices and increases cost (sometimes).

So far, it seems SOD123 is my best option for diversity of zener devices. I am hoping to find something slightly smaller.

I also know diodes come in SOT (TO) style packages I am not very familiar with these devices but its more familiar than SOD, SM() and other diode (device) packages I am not familiar with at all.


texts: How a compiler generally works for a microcontroller

texts:
I want know how a compiler works. I know the stages of compilation, but

How will the compiler allocate the segments (data, heap, and stack) for a microcontroller?
How will it optimize the code?

This may be platform- and compiler-dependent. But I want to know in generic terms, what need to be considerd while programming.


texts: Possible to identify burnt component and its value?

texts:
The device is a Banana Pi M3, I accidentally short it out when I was playing around with my multimeter on the GPIO pins.... A noticeable spark came from that component in the above picture circled in red. Hopefully, only that component got burnt and nothing else, so I can replace it.

At first I thought it was a resistor or a capacitor, but I was wrong, I think. I'm guessing it's an SMD ferrite bead judging from the manufacturer's schematics. Schematics. I think it's the third page labelled PMIC where it shows an USB connector along with a DC in symbol.

Problem is, the values aren't labelled in the schematics, so I won't know what ferrite bead to order, the only thing I can tell from looking at it is that it's a 0603.

I have this multimeter: "INNOVA 3320 Auto-Ranging Digital Multimeter," from Amazon (Sorry, I can't post more than 2 links), if that helps. I don't mind buying new equipment, this is a learning experience type thing for me. Thanks.

Edit: Just a little detail as to how this happened. When I was playing with my multimeter, I put the negative probe to GPIO pin 2 and the positive probe to GPIO pin 6, I accidentally moved the positive probe around making it touch either pin 5 or pin 8 or both while still touching pin 6. The GPIO layout is the same as Raspberry Pi Model B+, or at least that's what the makers said.


texts: I am an Arduino beginner and want to build a obstacle detection system. I've IR Leds and TSOP receivers(38kHz). How can I modulate the LED to blink at 38kHz? Could you please help me out with some code!


texts: Why does this Edge Trigger Work on input of 555 monostable config?

texts:
I recently wired up a 555 timer in a mono stable configuration and found that when the trigger was held low for longer than the configured output pulse width, the output would stay high. After thinking about this.. it made sense. My 555 timer is wired like so:

I searched around on the web and found an article.
It explains that including a capacitor on the input causes a very brief drop on the input when the input signal goes low. Even if the input signal says low, the input to the 555 timer goes high immediately after triggering the 555 timer. The 555 timer won't give a high output until the input signal goes high, then low again to trigger another output pulse.
The part of the input they suggest is wired like this, which is what i'm most curious about.

Why doesn't the capacitor keep a direct path to ground? I know capacitors don't really allow DC current to flow, but what allows it to discharge to ground at all?

Even more tricky, why does it also work properly with a capacitor in series with the input and one end floating (open switch)?

This cap on the input is really confusing me.


texts: Multiplexer instead of multiple AND gates?

texts:
I have to use a standard 74hc595 Shift Register and monitor all of its outputs that I have previously set at my will as 1s and 0s. Because I have certain constrains on the monitor lines that cannot be tackled, I considered to use logic gates and ( lets say AND gate ) and by driving all outputs to HIGH connect expect a HIGH signal as well. If any output showcases any problems and changes between its states (radiation testing will be performed) then the last output will show a LOW signal and therefore I will know that something is wrong.
I want however to use less ICs than the current design ( 2 gates ). Can the multiplexer help me anyhow?
Again, I have 8 outputs. All HIGHs and I want a HIGH when all are OK and a zero when either them outputs go LOW.
Multiplexer as a milti-input gate.


texts: How would you connect a light dependent resistor / photoresistor/ CdS cell at a right angle to a surface mount board?

texts:
My project uses light dependent resistors (aka photoresistors or CdS cells). All the ones I can find for sale from the usual suppliers are through hole type. ie. they have two wire legs.
The PCB I'm working on currently consists entirely of surface mount components. I'd like to place two LDRs at the edge of the board at a right angle. I could just solder them manually but I enjoy the exercise of designing for manufacturing even while I'm still prototyping and adding through-hole components would introduce another step.
Best idea I could come up with so far is to use a right angle surface mount header and then whoever assembles the final product just pops two of them in, probably after trimming the leads.  But I tried with some standard 0.1" spaced female headers and it results in a rather loose fit.
I was thinking there might be some screw terminals or something press-fit that would result in a more secure connection but so far my search skills are failing me.
Any ideas?


texts: Optoisolator With LED in series not working

texts:
I'm using an FODM8061 Optoisoltor with and open collector Logic Output. I'm referencOptoisolator Logic Output Question

Here's my current circuit:

LED 1(on the left) connects to an open-collector gear-tooth sensor. The led is used to help set the location of the sensor. It's intended to light up when the sensor is correctly positioned. On the right side, the signal coming out of R6 goes to the MCU.

My diagnosis: The LED will light up when I bring cathode to ground, but I get no output on optoisolator. When I short the LED(remove the led from the circuit) and bring it to ground, The optoisolator works as intended.

Why would the LED cause this issue? Can I provide any other information?


texts: Trying to ID a failed component, almost looks like it was a halogen style bulb

texts:
I am trying to see if anyone can help me identify a component on a PCB.  This device took a voltage spike on its AC line from a lightning strike on our home, and the unit is no longer working.

The component is labeled "SA1" on the PCB, but as you can see, only half of the device remains so I can't get enough unique numbers to cross reference anywhere.  This board is immediately down-stream from the power on/off switch, and if I am following the traces on the PCB correctly, this component is soldered between the neutral and ground planes; the hot side of the 120vAC feed is fused with a 5A-250V fuse.

The failed component almost looks like it was a halogen style bulb, but not sure why there would be one in this location on the system, or how it would work with placement between ground and neutral, unless the yellow wire is actually the hot and black is neutral which seems counter to typical color coding practice.

The PCB is labeled with "E154554" & "SH-A 94V-0", but searches for that show many different PCBs with none looking anything like this board.  I even saw those same numbers on other boards in this device, so that was rather weird and explains why I am not finding anything in my searches.

If you have any guidance, I would really appreciate it.  Just trying to see if replacing this part will fix the issue, or if the spike was such that it has fried things all over inside this unit.


texts:
Will the gain of the following IDEAL Op-Amp be zero?

My reasoning is that the positive (non-inverting) terminal voltage is zero because it is connected to ground.
Since the voltage for the negative (inverting) terminal is supposed to be equal to the non-inverting terminal voltage for an ideal op-amp and that the Vin of the op-amp is equal to the non-inverting voltage minus the inverting voltage, the Vin will also be zero.

Therefore. the gain will also be zero, and the Vs will also be zero.


texts: What is the effect of a neodymium magnet on a smartphone's touch screen?

texts:
What are the possible effects of multiple neodymium magnets in relatively close proximity to the capacitive touch screens most smartphones use nowadays?

As the screens themselves are LEDs the image should not be affected (unlike the old CRTs), but I'm not sure about the touch components.


texts: Detecting electrons as they tunnel through the band gap of a P-N junction

texts:
As a learning exercise I'd like to try creating a random number generator using reverse-biased BJTs.  As I understand it, if the emitter is saturated in reverse bias, occasionally electrons will tunnel through the band gap to the base pin.

Can this be done with common BJTs or are special parts required?
What sort of amplification will be required to actually detect this tunneling?  I.e. at what voltage will the signal be on the base pin when an electron tunnels through?


texts: use minimum number of NAND gates to realize this boolean expression

texts:
How should I proceed to find the minimum number of 2 input NAND gates to realize this boolean expression. I am allowed to use both complemented and non-complemented inputs.

$$F = X.Y + Y.Z + \overline{X}.\overline{Y}.\overline{Z}$$


texts:
I am using a MCF5253 controller which is based on Coldfire Architecture.
It has 8KB of Instruction Cache.
Everything was working fine till I enabled it's Instruction Cache.
Now what's happening is Adapter is getting reset randomly.
When I debug it, It resets due to exception of "Illegal Instruction", No such exception comes if I run by disabling the Instruction Cache.

Is it necessary that periodically one should clear the cache? and if it is then at what frequency.

Another thing I would like to know is how can I calculate Cache Hit/Miss Ratio?

Thanks!


texts:
Background
I'm working on application that I think the LP2950-50 would be appropriate for.  I want to control a set of SSR 40 DAs from the GPIO pins of a raspberry pi.  Empirically, I've found that 5V applied across Vin of the SSRs works best to close AC side.  I don't want to use the 5V out from the Pi, so I'm trying to build a power supply circuit that sends current from a LP2950-50 to the SSR (using an LDO per SSR).  I'm using a 2N2222 NPN transistor per GPIO pin to control current flowing from the LDO to the SSR.  I've built a prototype of this circuit, and it works. I can control the SSRs as intended.  The circuit is an array of the following (one per SSR):

The problem
I'm not consistently measuring the expected voltage on Vout of the LDO.  What I have observed is that if I increase the impedance of the circuit between Vout and Gnd, the value I measure between Vout and Gnd increases.  This seems contrary to the datasheet which suggests that I should be getting ~5V out regardless of the load applied to Vout.  I've been able to get the LDO to produce the expected voltage, but only by finding a resistor of appropriate size.  ~1KOhm between Vout and Ground seems to do it.  I'm able to replicate the issue with the following simple circuit.

When I measure potential across the resistor and LED, I'm only seeing ~3.25V.  If I increase the size of RL to 1KOhms, the voltage across RL and the LED increases to 5.5V.  I can swap in a brand new chip and get the same result.
What I've tried
Various capacitors.  I'm using a 1uF tantalum capacitor with an 8 Ohm ESR rating.  Per the datasheet, the ESR value may be too much.  Should this out-of-spec ESR produced the results I'm seeing?  I also tried a 1.5uF ceramic capacitor hoping it would have an ESR between the minimum of 20-30 mOhms and 5  Ohms.  It produced the same result: need to vary the impedance across Vout and ground to get the desired voltage.  I am not yet capable of measuring the ESR of the ceramic resistor.  Aside from ordering another pack of caps with known ESR that's in range (or trying another sized capacitor), I'm about out of rope on this.  Any thoughts on anything to try next?  Apparent design flaw on my part?  Or maybe the chip is working as intended and I should let it go.
Edit after answer:
I was reading the pin-out incorrectly on the datasheet.  After inserting correctly I can measure the expected voltage, even with an out-of-spec capacitor.  When supplied a 60Hz square wave signal from the Pi GPIO the LDO continues to perform well.  It continues to deliver a 5V signal on Vout despite an out-of-spec capacitor.
Notes:

I've calculated the internal resistance of the SSR to be ~400 Ohms via Ohms law.
LP2950 Datasheet: https://www.ti.com/document-viewer/LP2950/datasheet
Capacitors (TAP105K035CCS) datasheet: https://www.mouser.com/datasheet/2/40/tap-776819.pdf


texts: Chinese CC adjustable load microcontroller

texts:
I've bought recently a cheap adjustable load from AliExpress (see link).

For the price, it's really decent. I use if to test LiPo batteries discharge.

All in all, I'm really happy with it, but it really, really lacks at least one feature: data exporting. It would be perfect is I could extract the datas from its little brain.

Upon some researches, I was pretty disappointed to find that its main microcontroller is a rebranded (is it really?) chip referenced as "00RBJ03" for which absolutely no datasheet can be found. However, the chip right next to it is a simple 64kb EEPROM, for storing values I guess.

Have you ever encountered this kind of problem? Is there anything I can do to get to know what is that microcontroller?

Thanks in advance.


texts:
How big a ground plane does a gps antenna need?

I am using a GPS puck antenna that has a magnetic base to hold it on to, typically, the roof of a car. I would like to use it from my room at home, on a piece of ferrous metal plate mounted horizontally outside outside a window. So my question really is: how small a ground plane can it reasonably be?


texts: Solar LiFePo4 Battery sudden discharge at end of the night

texts:
Image above showed performance of the system over the past week. Blue is battery in W (this takes into account 2 230w/h batteries. Orange is the current from the PV. Grey is the W used by the LED during the night.
The drop I am referring to is on the night of 29th before the 30th.
The weird pattern on the 26th night is due to an internal problem with my task manager, just ignore that section
I am not an electrical engineer but have some understanding of electrical components. Sorry for noobness, hopefully you guys can change that
tl;dr :LiFePo4 batteries discharged really fast for no apparent reason. why would LiFePo do this?
I have 2 230Wh 13 V LiFePo4 batteries in my outdoor lights. Panel is 18V 70w and LED is 30w. I don't have other data.
They on my property and off the grid.
New system, less than 10 cycles.
They have a 30 W LED attached and a 70w Solar Panel to charge the batteries.
Batteries charge during the day and discharge at night.
I live in a warm environment North Hemisphere, 34 F is very rare even in winter. It has not gotten colder than freezing yet this month
Usually one battery stays at 100% while the other discharges from 100% to about 30% to then recharges during the morning. They rotate every 3 or 4 days.
Yesterday battery A (battery on call) dropped from 32% to 5% and battery B (not on call) went from 100% to 58%
I get this data from an app and not physically since they are 15 feet from grade. I pull data every 15 minutes into an Excel sheet and plot stuff out to keep track.
I checked the battery status for maybe 1 hour and they started charging: battery A to 7% then 9% and 12% and battery B to 59% then 70%. So it seems to be charging normally.
Why would it discharge so quickly?
Thanks in advance
Edit: 230Wh not Ah


texts:
I have to prepare easy analog PWM regulator which can operate from 0% (0V). I know that one 555 can't do that...
Do you know any circuit that can handle that?


texts:
These days light aircraft come with lots of instruments that require thin co-ax cable for GPS antennas, transponders, collision avoidance systems, tracking and navigation systems.Like this GPS antenna as an example.

Whats the best way (from the signal quality perspective) of handling extra co-ax?

Space behind an instrument panel is often at a premium, manufacturers typically supply antennas with 1-2 meters of cable but in a small aircraft (microlight or glider) the antenna might be only 12 inches from the instrument. With 4 or 5 such antennas the space behind an instrument panel can quickly become a cluttered mass of wires. The people who install these instruments are often the pilots or engineers with little knowledge of electronics. There seems to lots of 'psedo-science' around how to handle the extra meter or two of cable.

1) the simplest (and most common) option seems to be to leave the
cable excess in a neat loop (like in the photo) secured with a cable
tie. However, some say this will cause inductance which will effect
signal quality (my view is that inductance is a current related
phenomena, and the current flowing through the coax will be
negligible)
2) the 2nd prevailing opinion is that the spare cable should be
looped in a figure of eight fashion to prevent induction.
3) another suggestion I've heard is to loop the spare cable in the
biggest possible loop (i.e. a two meter cable looped twice into a
30cm diameter loop) the argument here is that fewer turns means less
inductance.
4) the best solution is almost certainly to trim the cable to
the exact length, however this isn't without it's own problems, the SMA/SMC cables are so small that they can be really hard to crimp, and antenna often need to be moved about when searching for optimum positioning, so there's always the danger of getting the length wrong

So back to the original question. From an electrical engineering perspective, with a view to getting the best signal quality without interfering with similar instrument nearby whats the best way of handling excess cable? Is it one of the options listed above? Or something else? Or maybe it won't really make any difference?


texts: Audio op amps - what do they do to the audio I hear from the speaker?

texts:
I have a simple DC circuit which outputs audio from a ESP8266 attached via 2 wires and a NPN transistor to a simple speaker. It uses this library : https://github.com/earlephilhower/ESP8266Audio/ to read and playback audio, it works and I hear audio.

My circuit at the audio bit looks similar to this:

     2N3904 (NPN)
                            +---------+
                            |         |     +-|
                            | E  B  C |    / S|
                            +-|--|--|-+    | P|
                              |  |  +------+ E|
                              |  |         | A|
ESP8266-GND ------------------+  |  +------+ K|
                                 |  |      | E|
ESP8266-I2SOUT (Rx) -------------+  |      \ R|
                                    |       +-|
USB 5V -----------------------------+

I also have an audio op amp : OPA2134PA. The Datasheet which I have read can be found here: http://www.ti.com/lit/ds/symlink/opa2134.pdf

Having read this pdf, and various other google searches I cannot determine, what an Audio Op Amp does? I know an op amp, takes the difference between 2 inputs, and amplifies it.

What does this mean for my circuit and more importantly to the sound I hear from my speaker were I to add the OPA2134PA?

I think my pins would be:

1 - Output (negative to speaker?)
2 - Input negative (collector on NPN transistor)
3 - Input positive (USB 5V line . ???)
4 - Negative power supply (??)
5 - Positive power supply (??)

The pins are likely wrong, so in addition to my simpler, what effect does the audio op amp have on my sound playback question, please also help me figure out how to wire in my audio op amp pins correctly.


texts: What's the difference between the terms Electronics and Electrical?

texts: So can anybody tell about what's the difference between the terms Electronics and Electrical ? How do we differentiate them from one another?


texts: How to convert an DC to AC signal more efficiently H-bridge?

texts:
Currently I am working on an project to feed back the output from an solar panel to the grid. One of the circuits used is the H-bridge. This part is used to convert an arbitrary DC signal to an AC signal. The first circuit was the following:

The 2N2222A are in my case simple N-mosfets

The second circuit was the following:

The third circuit was simply using an IC with all the components internally.

The first circuit we could not get to work, but was probably because our shortcoming of knowledge :) . The second one we did get to work, but was hard to maintain an good signal and was using 2 watt! Therefore we made the third one to lower the power assumption. This one was using somewhere around 1 watt (it changes from time to time, which is something we have to still found out).

Question:

Currently we have the H-bridge for the DC>AC,but is (still) using 1 watt of power. Is there something  (in used chips for example) so we can get the used wattage down in total. Is there maybe another option we can use to make an AC signal which is far more energy efficient.

UPDATE:

1.) The target efficiency is high as possible, every loss on some component is one to many. Of course, you will never get it to 0, but the lower the better.

2.) The VCC of the first circuit has a voltage of 25 volts (INPUT). The four ports (A,A,B,B) are connected to the "grid" (with a 20 volt AC, we first test with a lower voltage). A and A are directly connected and B,B are connected to the grid with an inverter to get a positive voltage over the mosfets. The OUTPUT must be at least around 21 volts (so the voltage will be higher then the grid).

3.) In the second circuit the function generator is the grid, with the same specs as the first circuit. The pwm signal is not sure yet and can be varied. In the third circuit the function generator is a representation of the grid point after the travo (see point 3 in update 2).  The resistors are all 1k and are just for some security at some points.

UPDATE 2:

1.)

MOFSET: MOSFET N-CH 60V 16A TO-220; part number STP16NF06L
For the other parts I will have to look. I can't look them up right now, but the diode is just a simple diode (no zener).

2.) YES, the 25 volt is the input and the output must be at least 21. volts.

3.) For testing right now we are indeed using an 20V AC trafo between the grid and our circuit. This of course makes a sin wave.

4.) I am living in Europe so the "standard" voltage is 230 volt RMS. The travo is NOT RMS. So the peak is at 20 volts.

5.) The losses were measured with connecting a voltage supply to the input of the h-bridge (around 25 volt) and the output (the "load" point at the H-bridge) was connected to the travo with 20 V RMS. The current was measured at the input point of the H-bridge (VCC). The voltage was measured at the voltage source and over the "load". The consumption of the H-bridge was in the second case 2 watt and 1 watt in the third circuit. The first we never got working correctly (still not sure why, so there are no results of that).

6.) The input is an square wave.

7.) The efficiency is not calculated yet, just the loss in watt. I am not currently at the place where it was build so can't give any value on the efficiency.

8.) The whole package in the third case was using around 180mA.


texts: op amps comparator or differential amplifier

texts:
I have a part of electronic schematic as described bellow, I'm a little bit confusing about the function of the LM321 amplifier. In this case, can we say that is a differential amplifier or just a comparator (open loop, no feedback, cause of the PNP transistor)?

I thank you for your support.


texts: Multiplying the deviation from mean of two time varying voltages

texts:
If I have two time varying voltages, \$V_1\$ and \$V_2\$ coming from two light detectors, how would I go about 'multiplying' the two signals with an electronic circuit?

The voltages vary \$\pm 5V\$ against a mean of ~6 V at a frequency around 1 GHz.  The idea is to subtract the mean value so the voltages swing positive and negative.  Multiplication and summation at this point gives some measure of the coherence of the signals.  If both are positive then multiplication is obviously positive, if both are negative then you also get a positive output.  If they are coherent then they should swing +/- together.  Some summation over time gives a measure of the coherence.

Basically it's an attempt to replicate the Hanbury-Brown and Twiss effect.


texts: LTSpice - How to specify the component model name through .param directive

texts:
I have some subcircuits that I want to define as components, but still be able to specify the component models used internally, for a much quicker testing of the design's performance under different set of models.

I know how to change the attributes of internal parts by passing the numeric notation on the SpiceLine of a symbol (.asy) to which the names of the variables are the same as the variable names of attribute values in a .subckt model definition of a model .included in a schematic.

So here's a simple subcircuit

vdrop_diode.txt:

.SUBCKT vdrop_diode 1 2

D1 1 2 1N4148

.ends vdrop_diode

here's the snapshot of the symbol:

The only attributes filled out were:

Prefix: X
Value: vdrop_diode

Then here I want to be able to change the model of the component

vdrop_diode2.txt:

.SUBCKT vdrop_diode 1 2

D1 1 2 {D_model}

.ends vdrop_diode

snapshot:

The only attributes filled out were:

Prefix: X
Value: vdrop_diode
SpiceLine: D_model=1n4148

The default model is 1N4148 (as specified in SpiceLine), but I to be able to simply change to any model I wish. The first problem was 1N4148 passed in SpiceLine was being interpreted as 1.4148e-9. It takes the N as nano, like it was just numeric notation. But, when I tried model names that cannot be interpreted as numbers, like say BAT54 it outputs:

WARNING: Can't resolve .param d_model=(bat54)

Am I not wrapping it in quotation marks or something? Or can this just not be done.

I'm not looking to stepping through a list of model names, just specify a model name for a subcircuit definition.


texts: In Impedance track algorithm, How is resistance is related to soc(state of charge)?

texts:
In impedance algorithm for battery capacity, why we are calculating impedance and why it important to know impedance for SOC(state of charge)?

2.I doing some research on algorithms which we have,so,kindly suggest me something.

Thank you


texts: Creating a custom TRRS splitter for headphones and mic; how to handle the mic's TRS jack?

texts:
I want to create a TRRS splitter / joiner that can be used to combine two 3.5mm jacks, one for headphones and one for a microphone, into a single 3.5mm TRRS male jack. It'll use the CTIA standard so that I'd be able to connect it to a standard PC or mobile phone headset port.
The issue is that the sort of microphone I want to connect (here's an example) uses a TRS jack, and with a TRRS cable only one contact / wire is used to carry the mic signal (which with the CTIA standard is the sleeve). I'm fairly certain it's an electret microphone, it's mono, and it's unbalanced.
What do I do with the ring contact on the mic's TRS jack?
Here's a (crude) illustration of the issue:

Perhaps I connect both the mic tip and ring to the TRRS sleeve? Or maybe the mic ring should be connected to the ground?


texts:
this is more of a theoretical question, and I do not know if this is suited for this QA site at all,  but at school I was asked to provide 3 examples of sensors (in the narrow sense) that are also actuators.
I cannot find any information for the life of me. The only example I can find are piezoelectric sensors, but I am not sure if this is correct.

A sensor in the narrow sense is a device which reacts to a signal/stimulus from a electrical signal.


texts: Polarizated BJT Class A: Conceptual DC analysis

texts:
The transistor (figure above) has a following characteristic: \$V_{BE} = 0.7V\$ and \$\beta = 120\$. It is polarized to class A peform amplifier with \$V_{CE} = VCC/2\$. What the value of resistor \$RB\$.

My attempts:

Honestly I find 2 answer to same question:

\$V_{CE} = 6V\quad\therefore\quad V_C =6V\Rightarrow i_C = \frac{V_{CC}-V_{C}}{1k} = 6mA\$

\$i_B = \frac{i_C}{\beta} = \frac{6}{120}mA\$

\$i_{113k} = i_B + i_{RB}\Rightarrow i_{113k} = \frac{V_{CC}-V_B}{113k} = \frac{6}{120}+i_{RB}\Rightarrow \frac{11.3}{113} = \frac{1}{20}+\frac{0.7}{RB}\$

\$\frac{1}{10} - \frac{1}{20} = \frac{0.7}{RB}\Rightarrow \boxed{RB = 14k\Omega}\$

Correct Answer

Second Attempt

If \$ V_{BE} = 0.7V\Rightarrow V_B = 0.7V\$, since \$V_E = 0V\$

Simple Voltage division:

\$ V_B = \frac{V_{CC}\cdot RB}{RB+113k}\Rightarrow 0.7 = \frac{12\cdot RB}{113k+RB}\Rightarrow 0.7\cdot 113k = RB(12-0.7)\Rightarrow RB = \frac{0.7\cdot 11.3\cdot 10}{11.3} \Rightarrow \boxed{RB = 7k\Omega}\$

Wrong Answer

So, why did I miss/leak the second analysis?


texts:
I'm a terribe novice when it comes to electronics and I've got a question:
I have a simple circuit including a photocell that regulates current (I hope this terminology is correct). It works as it should: The more light, the more current flows.

Now I am looking for some opposite device: A schematic / device / photocell (?) that increases its resistance the more light is applied.

Is there something like that? I'd be gracious for any help.

edit details:

I'm quite sure that what I'm doing is a total no-go, but somehow it's working anyhow (i'd be glad for any tip you guys have :))..
My super-simple (dangerous?) circuit consists of a 9V battery and a power-led. in between their connection I simply placed a photocell. As mentioned, I'd like this photocell to work in opposite of its current function: Power-led should become brighter if I "close up" the photocell.

thanks a ton so far!


texts:
I'm curious about JFET/MOSFET circuit B class amplifier. When BJT is used we only have those (+/-)0.7V limiting the transistors and causing crossover distortion. But with adding FETs or MOSFETs to the circuit, things rapidly change:

FET class B amplifier: Here JFET in only limited by the pinch-off voltage (not by 0.7V like BJTs) so crossover distortion does not occur. If input voltage exceeds the pinch-off voltage then we only get a signal cutter, right?
MOSFET class B amplifier:

-- Enhancement mode MOSFET: Crossover distortion applies for this one, since we need to turn ON the transistor. But the disadvantage (my opinion) is that crossover distortion is quite wide/large, since the transistors threshold voltage varies from 2V to 4V.

-- Depletion mode MOSFET: Same as for JFET, only that here we can also enhance and deplete the channel, right?


texts: What is the efficiency of electric power converted to heat?

texts:
I'm trying to understand how much heat is generated when a given amount of electric power is drawn.  And from what I understand, it's pretty much 1 to 1 isn't it?

Example:  If I have a 1 HP motor running at 50% load and so pulling about 0.5HP, then isn't the amount of heat coming from the coils equivalent to 0.5HP of heat?

I draw this conclusion based largely on the fact that the only real power used in the motor is supposed to be resistive power.  The reactive part produces no heat, nor does it do any mechanical work. Well if I had an Ohmic resistor allowing 1KW of power to flow, then I'm essentially generating 1KW worth of heat aren't I?  Granted, not all of the heat is dissipated in the resistor itself.  Some of it is dissipated in the various transmission lines and components delivering the power.

Is my understanding correct?


texts:
I have a 1.8" TFT color display from Banggood. It's very nice with the vivid colors.

However, the screen refresh is slow. I'm limited by the SPI speed of 1 MHz. It results in an update rate of:

  160 pixels x 128 pixels x 16 bit/pixel ÷ 1 MHz = 0.33s per frame

Effectively, it's even lower as the Teensy LC stops for about 1 cycle after each byte and there is overhead between the SPI transactions. So it's more like 0.5s per frame or 2 fps, which is very noticeable. It's more like a left to right swipe animation (see image below).

So my question is:

Is the speed limited by the display controller chip, probably a ST7735?
Or is the speed limited by my breadboard wiring?
Is there a faster display available where I could use the SPI bus at 4 or 8 MHz?

Update

Here's a picture of the bottom of the board.

Not much to see:

The SD card slot and the three resistors R1 to R3 are not used.
The resistor R4 close to the LED pin (right most on the image) is connected to the LED pin and has 7.5Ω (7R5).
The part with three legs in the top corner reads "V2PK". I guess it's a voltage regulator that would be used for 5V operation. I operate it a 3.3V. There's also a capacitor and an open jumper close to it.

The interesting part is probably hidden between the PCB and the display.

Solved

It's now properly working. On a Teensy LC it runs at 16 MHz, on a Teensy 3.2 it runs at 18 MHz. Both are the maximum SPI clock rates for these boards.

It turned out to be a software problem. The main problem was that I hadn't properly disabled DMA. It would then kick in too early on the next SPI transmission, i.e. it would start with the first byte of the transmission even though it was supposed to start on the second byte. This mixed up a few thing and left the device waiting for the last byte to be transmitted.

I still do not really understand why it work at lower frequencies but failed at higher ones.


texts:
Could anyone recommend a replacement capacitor for an sk, mp capacitor 2uf 350v?. This one was used as a starter for an old fan.
Thanks.


texts: I have a square wave backup inverter (UPS). Whenever the power goes out, UPS turns on but all the fans run with noise and humming sound. I know it is because of square wave and harmonics. But when I plug in my laptop charger during power outs into socket (connected to UPS output), the noise is gone. What is going on here? Is my laptop charger is working as harmonic filter and absorbing harmonics? Same thing happens when energy saver is turned on but the effect is little.


texts: How to return from SystemC thread with error code?

texts:
I've got a SystemC testbench (for a VHDL DUT but that's irrelevant right now). I'd like to be able to cause the test to terminate, with a specific exit code, from within an SC_CTHREAD.  I am pretty new to SystemC (I'm mostly a verilog/sv guy).

I've tried simply including "exit(error_code)" but while that terminates the simulation, the final exit code comes from my sc_main's return statement.  Edit: I guess this makes sense since the "exit" probably terminates the separate thread with that exit code, but not the sc_main thread.

I've tried calling sc_stop before that exit, and usually get an error about calling a pure virtual method (I believe that's end_of_simulation, which I have not defined....but that should be optional, right?).

The only way I see to affect the exit code of the process is to change the return statement of sc_main, but that doesn't quite work when all my action is happening in an SC_THREAD created by a constructor of an object somewhere (if it's not obvious I truly don't understand how SystemC works very well, probably because there's a lot of hidden action with secret classes that we can't see, as opposed to verilog where simulation ordering is all there is, assuming you understand blocking/non-blocking).

Note: I am running with a commercial simulation tool, and not pure C++.  It's possible that there's an implementation bug there.  I'm trying to get our pure C++ compile running but it seems to have broken a while ago (I'm not responsible for the SystemC model).


texts: Impedance control for small antenna feed?

texts: I have a BLE board with a 1/4 wavelength antenna and a feed that is about 12mm long. The wavelength of 2.45ghz is 122mm. I've seen various discussions saying anything over 1/10 the wavelength you probably need to impedance control the trace?  Is this true? Can I get away with not using very tight impedance control on this feed line?


texts:
I wanted to check the power consumption of my LED bike lights, so i connected my multi-meter up and switched the light on.

Initially the current was 1.2A, but over the next 15 mins or so the reading dropped to about 0.7A, there was no noticeable change in light output. At first i thought this was some sort of heating effect reducing the current.

But if i switch the light off and on again quickly the current would return to 1.2A and again drop off over 15 mins or so.

Can anyone explain what is going on? Shouldn't the current usage be more or less constant?

The bike lights are the generic "magicshine" LED type lights connected to 18650 batteries if that matters.


texts: sizing a DC bias RF choke for a differential antenna + PA

texts:
Trying to figure an antenna for the Si4012 RF chip. Page 26 of https://www.silabs.com/documents/public/application-notes/AN639.pdf talks about feeding the two sides of the loop antenna through two pull-up inductors (LP and LM) which it fails to provide any values for.

I have read here that I should

  Select a sufficiently high inductance value. (Z = 2 * pi * f * L)
  Select an impedance (Z) that is much larger than the load resistance.

This usually translates into "make it tenfold"

In my design, |Z_load| is somewhere between 500 and 600 ohm (PA and adapted differential antenna). Wouldn't it be required to pick an inductor having its impedance in the 5k - 6k ohm interval in order to actually be effective at blocking the fundamental + first few armonics ? -

Meaning 2.2 uH with a SRF of more than 1736 MHz in order to cut out everything to and including the 3rd armonic. The trouble is I am unable to find on the market such a large inductor at that kind of SRF. They usually go to 100+ MHz SRF at 2.2 uH. Perhaps I am miscalculating something ?


texts:
I'm a co-op student working on a hardware design for an industry client, and I'm trying to use a TPS63000 to get a Vout of 3.45V. Vin is 5V. When I power this circuit up, I read 5V on Vin but only 0.7V from Vout.

Here's the PCB design:

I'm not sure what approach to take in troubleshooting this. Any help would be appreciated.

EDIT: Unfortunately I don't have easy access to an oscilloscope, but when I do, I will definitely try to confirm that there's a pulse across the inductor.
Yesterday I assembled another PCB, and I'm getting a very similar result. Vout actually stabilizes at 322mV, and does so with a high degree to accuracy. During startup, I do see Vout shift drastically, but always settles around 322mV. Sorry that that's not very much to go on, an oscilloscope will definitely help give a better picture.

So it seems to me possible causes are: A. lack of R3/C3 on the Vin pin, B. narrow traces on the PCB, or C. bad chip. Thanks for all the responses so far.


texts: What is the purpose of diodes in parallel with transistors in a solid state relay?

texts:
I know the diodes facing each other are for ESD protection, but what do the diodes facing opposite do ?

The circuit is basically a 24V (usually used in industry) digital output.


texts: Switchmode design for a general-use benchtop power supply?

texts:
I'd like to build a bench power supply for prototyping and development work. Most of the benchtop power supply designs I have seen are based around a transformer, rectifier and linear regulator (eg 7805/LM317).

However, I like the idea of keeping it efficient, so am interested in building something switchmode instead.

My work is mainly microcontroller-based, but I mess around with audio stuff from time-to-time too. I'm thinking that a 3-rail design (±15V to 0V adjustable, +5V, up to 1A) would cover most things.

Would the increased ripple voltage of a switchmode power supply make it unsuitable for general-purpose use?

Or, given that I'll be relying on this power supply for a lot of future work, should I stick with the simplicity of a linear regulator design?


texts: Do all components obey Kirchhoff's Current Law?

texts:
Kirchhoff's Current Law states that the net current through a node is always 0. AFAIK this derives from conservation of charge principle. My question is, is KCL applicable to any electrical component? For example is it applicable to transistors, integrated circuits, etc.

My thought is that it should be applicable, because otherwise, the component would be accumulating charge over time, which I presume is not a stable or desirable (in general) condition. Another possibility would be that the component would be "leaking charge". For example, the component would be "throwing charge into air" etc. In this case, the component is not accumulating charge but charge is being moved out of the circuit. I guess this doesn't happen in general as well.

So my question is, is Kirchhoff's Current Law is applicable to any circuit element? For example, if I add up the currents through pins of an integrated circuit at a given time by taking current directions into account, will I get 0 amperes? Similarly for any other circuit elements. Are there any cases where the net current is not 0 amperes?


texts: In a communications system does the order of channels is in a cascaded channel affect the overall capacity?

texts:
I'm currently looking at capacity for cascaded channels as part of my Communications Systems module and we're looking at a question in which we have four identical channels represented by the conditional probability function given in a matrix:
p(y|x) =
|0.9 0.06 0.04|
|0.04 0.9 0.06|
|0.06 0.9 0.04|
Then another channel:
q(y|x) =
|0.98 0.01 0.01|
|0.01 0.98 0.01|
|0.01 0.98 0.01|
As far as I could tell the capacity didn't change whether q was in position 1 in the cascade or position 5 in the cascade. I also tried some different matrices that didn't resemble the identity matrix so much and again I found position didn't matter and I was wondering why this is?


texts:
The circuit is a LPF with a buffer stage in front of it that uses a linear pot. to control gain & attenuation. The setup is such that the response of the linear pot. is similar to a log. pot..

A single 5V power supply is a known limitation, however the design must have this.

The 1st stage gets input from a CD player (low Z output), this goes to the buffer with DC offset added. This goes to a 2nd stage which sets the potential gain that can be set by the pot. by the ratio of R6/R5. Next, the LPF.

The circuit uses 3 op-amps and 2 levels of DC offset are added. If the circuit could be simplified it would be great. Thanks!

simulate this circuit – Schematic created using CircuitLab


texts:
I read the following in the datasheet of ULN2803

  Utmost care is necessary in the design
  of the output line, COMMON and GND
  line since IC may be destroyed due to
  short−circuit between outputs, air
  contamination fault, or fault by
  improper grounding.

I understand what short-circuit is, but what does "air contamination fault" mean?


texts:
I have an atmega168pb and I've noticed that there is a difference in how the board can be programmed between Windows and Linux.

On Windows using Atmel Studio you can select an ISP interface and it automagically programs the board through the USB port. However since Atmel Studio is not available on Linux an external programmer is needed. This irks me because hypothetically I would need to buy hardware to provide a solution that is already exists in a software implementation.

Is there a way to flash an AVR chip on Linux without the need for an external programmer, like an AVR-ISP for example?


texts: If electricity is a flow of electrons in a wire then eventually all electrons will leave the beginning of the wire and reach the end of the wire. Is that possible? Why if not? What will happen then if yes?


texts: Will this lithium ion battery cause too much heat and fry components?

texts:
I am looking at this lithium ion battery from ebay for a project of mine. Its 12v and delivers 1-2A

I am using a female socket lead to power and gnd wires for the battery to connect to a breadboard.

I am assuming that the battery will deliver 1-2A and so im a bit scared that it might fry regular prototyping wires, and breadboards and resistors might heat up, will the battery spew out to much amperage and fry everything, is this true and if so what should i do to prevent it, voltage regs?

I am using several power thirsty components: 4 dc motors, arduino mega, 4 hc sr04s, an acceloremeter and 2 light sensors along with a servo motor. The battery should be sufficient for powering these components (let me know if im wrong) but im wondering that if each component requires different voltages should I use voltage regulator for all other components (they all require less) and then hook arduino straight to 12v separately?

Without going into all the numerical specs of each component and judging from the list, how much heat would be generated figuratively and is the battery a good source for the components im using?


texts: Fusing electronic platforms into one IC board

texts:
I have an insane goal whose possibilities id like to discuss.

To start with I am interested in three different electronics platform for edge computing:

Edge computer: Like Raspberry pi or Intel compute stick that comes with light processors, IO devices (Minimum USB), Bluetooth & Wifi Antenna.
AI Sticks: Like Movidius stick. It is AI optimized to run algorithms and make fast predictions.
5G chips: That can tap into 4G/5G networks for data communication.

Now obviously one solution is to take these cores in the form of interfaceable IO boards and connect them using cables. To put it mildly that is sad ugly.

My insane desire is to be able to merge them all into one high speed/high frequency killer electronics platform (on which light weight OS like Alpine linux runs)

One thing I have thought about is to somehow get hold of VHDLs for these platforms and burn the design onto FPGAs or likes of it. Is this feasible and what are the alternatives?


texts: Need help in cable temperature calculations

texts:
I am trying to calculate how hot will a 0.6m long 28AWG wire carrying a load of 12VDC, 0.2A get.

I understand that are other factors such as environment cooling rate, thermal resistance between air and the cable etc.
Ampacity values are not really relevant to my scenario as the cable is in contact with the human body. Thus, I am more concerned about whether if the user can detect the change in the wire's temperature.

I also do not have the resources nor the proper apparatus to conduct an accurate measurement test.

An aluminium core 28AWG wire has a resistance of 0.32716 Ω/m.
Power dissipation:

$$P=I^2R$$
$$P=0.2A^2\times0.32716Ω \times 0.6m$$
$$P=7.851mW$$

Found this equation here, altough it is only meant for radiative heat loss
$$ \dot{Q}_{12} = \epsilon A\left ( \sigma T_1^4 - \sigma T_2^4\right )$$

Based on the above, I got a value of \$309K\$ which means the temperature increase is about \$4°C\$ from an ambient temp of \$305K\$.

Is this an accurate reference?

Basically, I want to know if a 28AWG wire will stay cool during operation or do I need to select a lower gauge wire.


texts: What Causes Voltage Drop In A Vacuum Tube Diode

texts:
This question is about the voltage drop across a vacuum tube diode.
Consider a circuit that consists of a battery, a vacuum tube diode, and a resistor all wired in series.
My understanding is that, at high-enough voltages, the current through a tube diode is approximately constant. Let me call this \$I_\text{out}\$.
This current must run through the resistor and back to the battery. By Ohm's law, the voltage drop across the resistor should be \$\Delta V_\text{resistor} = I_\text{out} R\$.
My question is: what happens when \$\Delta V_\text{resistor} < V_\text{battery}\$. Where does the remaining voltage go? Presumably it is lost at the diode, but I don't understand the model for voltage drop across a diode.


texts:
I have this Bi-Direction Switch:

(Image source - front of switch)

(Image source - back of switch)

I want to change the Button/Switch (I don't know the exact English word) to this one, for style reasons:

(Image source)

I can't find an explanation how the Button/Switch on the PCB works. Should I just try to solder the thing on there? Or would you recommend something else?


texts: What kind of IC component is this (JBN 5)? Photo

texts:
I'm playing with an Electric Fence Tester, trying to understand the schematics. I can't identify this component, due to my poor knowledge in electronic.

The aim was to connect the 7 segment display to an Arduino and make a remote tester via Wifi&REST request to my PHP server...but iI would prefer to read directly an analog pin that give me back the tension, yet transformed and stabilized.

Now I have wrote this:

simulate this circuit – Schematic created using CircuitLab

Thank you in advance! (sorry for my english).


texts: Modulation of 36 MHz wireless microphones

texts:
I've been given a handful of wireless microphones that transmit in the 36 MHz band, but unfortunately no receiver was included and proper receivers for that wireless mikes seem to be crazy-expensive.

I've taken at look at the RF with a scope and it looks a lot like simple FM with a pilot tone.

I'm guessing that the pilot tone is used only to detect if a channel is being used and not drowned in noise, so the receiver can squelch the noise.

Does anyone know how the audio is modulated?

I'm looking around for a simple, cheap FM receiver that I can modify to receive the mike signal and I've noticed that 36 MHz RC receivers are insanely cheap, so I'm thinking that I ought to be able to grab the demodulated analog signal before it enters the digital RC part of the receiver and pass that off to my own low pass and squelch circuit.

Any better suggestions for a source of cheap 36-37 MHz FM receivers?


texts: How do electrical engineers actually apply control theory in real life?

texts:
I am currently taking a course in control theory.

In control theory the system or impulse response is usually an algebraic expression in Laplace domain. Much of the work done in school is to find this transfer function or shift the pole of this transfer function around to make the system stable.

But this all feels a bit unrealistic. How so? Suppose I wanted to find the transfer function of my cell phone, how would I ever go about doing this? How do I know that the input-output relationship would be characterized by a simple differential equation? And how would I ever go about "shifting" the poles in real life so to achieve stable or some desired operation?

Can someone provide me with a realistic example of how a real device can be characterized using control theory (i.e. so that the system transfer function is known) and what it physically means to design the controller or shift the poles. 100 points for most real life example. Thanks!


texts:
I'm trying to design a PCB to use some large capacitors. I recently discovered that there is a much wider and cheaper range available as long as the capacitors are snap in style.

How exactly do the footprints work for these? The datasheet just shows two holes as usual, is there anything else needed? Do the leads fold over as the capacitor is snapped into the PCB? Is any additional clearance needed around the cap to account for the folded leads? Are they easy to replace once the electrolyte dries up? I want to make my device easily serviceable. Standard capacitors can easily be desoldered, but I wonder if snap ins are as well.

To install, you just put the leads through the holes and push down until they fold over?

Do snap ins have any disadvantages?

Edit: I realize snap in capacitors still have to be soldered, just wondering about how they physically "snap in", and if the larger leads prove more difficult to desolder, and if you can "unsnap" them to replace them if necessary.


texts:
I understand the role of a synchronizer is to make sure the input satisfies the dynamic discipline of registers. How does the above synchronizer fix that problem exactly? (What's the basic idea behind it?)
The information for the slide is found at:https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-004-computation-structures-spring-2017/c6/c6s1/


texts: Does the physical features of a wire like surface area, length or specific resistance form any sort of limit to the bandwidth of signals that can be passed through that wire?


texts: Can anyone illustrate a functional block diagram of a HC-SR04 ultrasonic sensor? I understand how it works when it comes to the application but I would like to know how it works fundamentally as a system.


texts:
I would like to be able to splice two buses in kicad into a third larger bus.

Say I have a subsheet with an output pin connected to a 16 wire bus (an unrelated note, it took me a while to figure out how to get buses through a subsheet but it works). I have another sheet where I place several identical copies of that subsheet and want to have the output of that sheet be a N*16 bit bus to be used in the top-level sheet, as an illustration, here is a simplified example of what I want to achieve

The first bus passes through perfectly, (e.g. lines 1-16 have associated nets and are properly placed in pcbnew), however the second bus (lines 17-32) doesn't get connected

I figured out a way around this by assigning each subcomponent bus a seperate unique bus name and then mapping each one, pin by pin to the corresponding pin on the master bus. it is however rather inconvenient given that the full schematic has 512 total lines in the bus ( :O ).

The not-so-convenient-solution is illustrated below (not all pin-assignments are shown for clarity)

In short, the question is if there is a way to get around bit-banging all the buses together like this and have a solution more like the first non-working method.

EDIT

Before anyone asks, this doesn't work either


texts: Is it possible to shortcircuit/damage an EMV card without a current source?

texts:
I've recently was accosted^H^H^H^H^H^H^H^ sorry, was gifted by the bank with contactless debit cards. They're standard EMV ("chip and PIN") cards apart from that.

I've decided to buy "card protectors", which are basically composed of thin metal (aluminum?) foil glued to the inside of a paper sleeve, as seen here:

Problem is, the EMV chip on one of those cards stopped being readable in terminals soon after I started using the sleeves.

Curiously, authorization by magnetic stripe and NFC (after removing the sleeve of course) both work fine.

It doesn't seem like the particular sleeve is magnetized - although I've only been able to use my smartphone magnetometer readings for verifying that.

Update: two days after the EMV chip failure, it seems that the NFC circuitry has died as well.

My question is: is it possible for such sleeves to damage the chip contact element somehow, and if so, how?


texts:
The prices of components of supposedly the same type and with the same parameters vary strongly between manufacturers.

Assuming my use does not come close to the absolute maximum ratings, is it worth paying extra for more expensive brands, or do the cheaper brands perform just as well? Or can I get bitten by subtle differences between manufacturers?

Does this also depend on component type? For example: resistors (with the same specs) might all perform equally, but 78xx regulator quality varies strongly, etc.

One thing I did notice (and do value) is that with the more expensive brands, the quality of the datasheets is usually much better. But mainly, I'd gladly pay the higher price if it means I can avoid hunting for subtle bugs I'm most probably not experienced enough to find anyway.


texts:
I have a 1998 Dodge Durango and am swapping transfer cases. The new case (NP242) uses a 4-pin switch (see photo). Dodge discontinued the adapter harness some time back and I have not been able to find a used one. The other end of the harness uses a Yakazi 090II Sealed Series that I have been able to find. My old switch used a Weather Pack connector here, so Dodge was all over the map on these. I know some Jeeps used this switch as well (99-01 Grand Cherokee?).

The terminals appear to be metri-pack 150, but the pin layout (cross vs square) and the notch (lower left in opening) does not align with any MP150 connector I have found. I did see one that looked similar for a 1992-97 LT1 oil pressure sensor, but tried one I had on an LT1 car of mine and it would not plug in.

The dimensions I measured were as follows:
Inner part where pins are: 15.5mm W x 12.5mm H
Outer part where seal sits: 22.0mm W x 17.4mm H

Thanks for any advice or help.


texts: Circuit Overvoltage Protection Using 12V Power Rail from Computer Power Supply?

texts:
I'm looking at building a circuit that is powered by the 12V power rail that is commonly provided with a desktop power supply.

What would be a good rule of thumb for what an "overvoltage" scenario would look like if a desktop power supply failed, and you wanted to protect what is powered in that circuit?

What sort of current or voltage peaks would you expect in a failure scenario for a desktop power supply?

For over-voltage protection, the easy answer is using an IC something like a LTC4360 -- but is protection up to 80V sufficient for a desktop power supply failure?

What happens when a power supply fails, that is hooked up to 120V AC source?  What starts pouring out of the broken power supply? (Hopefully nothing -- right because it has some kind of over-voltage protection -- but still....?).

Do you go with a more discrete solution and add a physical fuse and a crowbar circuit of some sort (I kind of like the fuse approach personally) -- if so, what kind of parameters?

Maybe an SMD resettable fuse and a zener diode? (Seems like the cheapest way).

I don't have any experience in power supply design -- or in this case, when power supplies fail and what that transient event looks like.


texts: Please help! Implement 4-bit Incrementer with two 74LS163 + 74LS74A + XNOR gate(s) + AND gate(s)

texts:
The Question

Use two 74LS163, one 74LS74A, XNOR gates and AND gate(s) to build a circit that can "add" two given "4-bit binary numbers" A and B.

Here is how the circuit computes SUM = A+B (for SUM <= 1111):

Load A into a counter.
Count up by number of clocks given by B to obtain SUM.

Hint: one 74LS163 will give you the SUM. The other 74LS163 will tell the first one when to stop counting.

You must place A and B into the inputs of the circuit, and initialise the circuit by setting/resetting/loading necessary register(s) using a signal INITIALISE = 0.

74LS163:

74LS74A:

What I've come up with so far

I am very new to this topic so I'm not sure if any of this is correct.

Here is a simple chart of how I believe the circuit works:

State diagram for SUM:

State diagram for B:

I don't know how to continue next. Could anyone please help? Thank you!


texts: Which UL standard(s) holds the specifications of all UL AWM styles of cabling?

texts:
Which UL standard documents the specifications of all UL AWM styles of cabling, detailing their construction, conductor sizes, insulation, etc. ?
In my research, I was directed to UL Standard 758 Appliance Wiring Materials, but it does not contain the specifications of each individual styles.
I also found https://iq.ul.com/awm/ which is supposed to be a library of the styles, but the page doesn't load for me and throws an error.
From the UL.com site, I went into Resources / UL Standards which brought me to
https://www.shopulstandards.com. Once there, searching for 20276 or 2725 (or UL20276 or UL2725) brings up nothing.


texts:
The limited stack size of budget PICs is a problem area and I have adjusted my code to accommodate this reality. I currently adopt a rough paradigm of grouping closely related functions into a module and declaring all variables global static in the module (to reduce the amount of variables stored in the auto psect, and issues of mutability are only relevant in ISRs, which I account for.) I don't do this because it is good practice, but the reality is you have a finite amount of space to allocate all local function vars that exist in an entire project.

In the embedded world of 8/16 bit chips, is this an appropriate method, provided I'm sure to take necessary precautions? I also do things like allocate > 256 bytes of RAM for Ethernet buffers and have to access that memory via pointers so I can avoid the semantics of memory banking. Am I doing it wrong? My app works, but I am 100% open to suggestions for improvement.


texts: General formula for efficiency of bridge rectifier

texts: Is there a general formula for the efficiency of a bridge rectifier ? I have seen a lot of efficiency curve like in the picture attached, but how should I calculate the efficiency of the rectifier based on input or output power alone ?


texts: What is this component and how can I drive it?

texts:
A long time ago as a kid I disassembled a plasma globe. Inside was a small board with a box-like plastic-enclosed component. This component has a long wire which leads up to the center of the plasma globe. For a long time, I used this circuit for some experiments with HV. However, the circuit has been practically destroyed while I was shipping it (mechanical damage). This main component seems fine though, so I have removed it from the board.

I would like to be able to salvage this part. Can anyone provide a data sheet or any information about how I can power this, and what exactly it is? It has two pins on one side of the bottom face, and five pins on the other side of the bottom face. The only marking is a label which reads "HL-66". I've attached a couple images for reference:


texts: CFLs and Incandescent Lightbulbs in household light fixture

texts:
I have a few light fixtures around the house where there are multiple sockets per fixture - 4 sockets/fixture in the kitchen, dining room, bathroom ceiling light fixtures.  I began the process of converting these over to using all CFL bulbs, but wanted to use up the supply of incandescent (Edison) bulbs I previously had. Thus, in some fixtures, there were 2 CFLs and 2 Edison bulbs.

I have noticed that when bulbs have failed in those fixtures, it was usually the Edison bulbs.  Is there a particular reason(s) why having CFLs and Edison bulbs in the same fixture might be bad?

Assume that each bulb is rated for the same actual wattage.


texts:
I have an old laptop which the display is removed. So I was wondering
if there is any way to make an adapter for DVI to use the existing
2x15 pin LCD plug.

This is what the manual says about the plug:

  The 15-pin D-sub monitor port supports a standard VGA-compatible
  device such as a monitor or projector to allow viewing on a larger
  external display.

Essentially I want to achieve this:

And this is what the plug looks like if that would be of interest:

I have the male plug which fits into the female plug shown in the images. The male plug has cables attached to it. The cables that ran through the display housing to the actual display.

What I would like to know by asking this question is:

Can it be done?
If yes: Will I need to make some sort of signal conversion or will it be
enough to simply connect the cables to a female DVI?
If no: Why? Is there an alternative way?

Also, I will gladly accept some feedback on which tags and terminology to use when it comes to this subject.


texts: Is it safe to touch a running 1 hp electric motor?

texts:
This question is about touching the housing of a generic AC electric motor like this one:

...while it's running, without considering any type of insulation, such as wooden floor, rubber gloves or boots, etc. Thanks.


texts: Why did USB win out over parallel interfaces?

texts: What were the technical reason(s) USB massively overtook parallel interfaces such as SCSI, IEEE-488, and enhanced parallel ports?  I understand the hardware can be simpler with just one data line rather than eight.  But intuitively there would be a significant speed advantage to transferring full bytes at a time rather than bits.  Is it a matter of USB being both hardware-simple and "fast enough"?


texts: How close can I put a 2.4GHz transmitter to an RFI-sensitive device?

texts:
I have a process-monitoring system which is sensitive to RFI, specifically in the 412-419MHz range. It has not been tested for sensitivity to 2.4GHz, but I've measured a WiFi signal level of -66dBm at the device in question while it was operating with no issues. The transmitter I'm concerned about has a max output of 1.25mW EIRP at 2.42-2.45GHz.

How do I determine how close I can let the transmitter get to the RFI-sensitive device without exceeding the existing signal level in that location?

I've tried reading into some wireless range and power loss calculations, but this isn't my strong suit and I'm not getting very far. I'm not necessary looking for just a distance, but the process to determine it.

Edit: Considering the unknowns in this situation, I understand that it's not feasible to get a precise value for distance for this particular device. However, the discussion below gives me a bit of a ballpark to go on and I expect that I'll be heading towards some testing to confirm. If any useful information arises at that time, I can incorporate it into this question, but I'll consider it closed for the time being.


texts:
The following code is meant for MSP430. Can somebody help me what is the purpose of trapping the CPU?  How will the program proceed if the CPU is trapped there?

Running the CPU of DCO and the crystal.

We want the MCLK sourced from DCO and ACLK to be sourced from VLO or 32KHz crystal.
The ACLK is sourced from LFXT1 by default.

#include <msp430g2553.h>

//This small set of code takes care of an inconsistency between g2553 and g2231. It should be present.

#ifndef TIMER0_A1_VECTOR
#define TIMER0_A1_VECTOR TIMERA1_VECTOR
#define TIMER0_A0_VECTOR TIMERA0_VECTOR
#endif

void main(void)
{
 //code goes here

WDTCTL = WDTPW + WDTHOLD;  //disables the watchdog timer by sending the  password (WDTPW) and hold command (WDTHOLD)

  //calibration starts here..
if (CALBC1_1MHZ ==0xFF || CALDCO_1MHZ == 0xFF)  //trapping the CPU
{
  while(1);  // If cal constants erased, trap CPU!!
}

 .//rest of the code for calibration...
 .
 .


texts:
I assembled a few JST PHR-4 connectors with wires (manually crimped SPH-002T-P0.5S crimp terminals with AWG24 wires and inserted it into the PHR-4 connector housing). When I tried to join connector header with the mating PH male pin header on PCB, I find I canno to insert it there. I don't want to apply too much force to connector, to avoid PCB damage. What can be the problem there?
I suspect this may be due to I created connector using manual crimp tools, and this can no provide the required accuracy.
Here is datasheet.


texts:
I am in doubt about how to route the relay in below situation.

The thick lines(3mm) on the left are Normally Closed, Normally Open pins of the relay, and the third line(2mm but top and bottom) is  Common.

The relay is supposed to withstand 220V AC with 2A.
The trace length is about 8mm
The PCB is two layered PCB with 1/2 Oz copper and 1.6mm board thickness.

Is there any better way to route it? Can the routing withstand the specification?


texts: How do i connect bluetooth to Lilypad Arduino?


texts: replacing a 2k resistor with a 1k and trimmer - wiring

texts:
I have a question about wiring up a trimmer in this circuit (NE555 - piano module)
I have no background in electronics so please bear with me.
One of the keys in the 'piano' sounds just off tune, so I would like to change the sound of that button by replacing a 2k resistor with a smaller resistor and a trimmer.

I have a 3296 trimmer of 1k

The only problem is that this thing has three pins, and I don't know exactly how to wire it properly.
If I understand it correctly- I can wire it up like this?

Or is there no need to wire up pin three?


texts: What is the power factor of a classical power supply?

texts: What is the power factor of a classical power supply ? I mean a transformer, rectifier and filter capacitor. Is it constant ?


texts:
I have ADM485 already mounted and an output of some device, buffered by CD4050BM. For the circuit to be safe for the RS485 bus, the ADM transiver initially should either be in Z-state or read-state. "Some device" is not always connected the circuit, so I want to use pull-down resistor to archive read-state by default.

Currently I'm not able to post images here, so I'll try to give short explanation of what I'm about to do.

-RE and DE of ADM485 are connected to each other (and this can't
be changed in my case)
These both are connected to an output
CD4050BM buffer unit (input of one is conected to "some device")
I wish to pull down this junction (-RE, DE, buffer out) with
resistor of 10k.

Is it ok to do it this way? Which resistor nominal I should use?

EDIT:

Here is an image


texts:
What causes turning ON a single output pin on Microchip PIC16F690 to spontaneously turn OFF another pin on the same port? I can work around this problem by writing a byte to the entire port, controlling all pins simultaneously, instead of just a bit to control the pin state. I'm using the Hi-Tech C compiler here. I am determining the state of the pin with 9 LEDs each consuming 3 mA. This is way below the max power specs.

The mplab header file has the 0 pin on port A declared as such:

volatile       bit RA0  @ ((unsigned)&PORTA*8)+0;

I am turning the pin on by writing a high value to it.

RA0 = 1;

Is the problem that the complier is treating the "1" as a byte and writing to the whole port?
Do I need to cast it? If so, shouldn't have the complier given me an error?

RA0 = (bit) 1;

If I write to the whole port everything works as expected:

PORTA = 0b00000001;


texts: having different voltages from 2 batteries in serie (3 voltages...)

texts:
for a project, running on battery, I need 3 different voltages (+/-3V and 6V)

+/-3V for OpAmp and µC (attiny85 will be plug to the 3v)
6V for the actuator

I was thinking about using 2x CR123 (3V lithium battery) in serie. Doing so, I can use them in a split rail configuration... But what about the 6V ?!

In deed, to control my actuator, I wish to use a DRV8838 (from TI) with the VM pin to 6V ... But .. their is only one ground pin... would it work if i use the -3V as ground ref?
- Or should I found a such a driver but with 2 ground pins (one for the signal, the other for power)
- Or should I reconsider the power supply section entirely using 1x CR223 and something else to split it into +/-3V ?!

I'm a bit confused so I hope I'm clear enough..
Anyway thank you for reading and Thank you again if you can put me out of this :)


texts: SPACE VECTOR MODULATION(SVM) for BLDC motor

texts:
I want to run a 4 pole bldc motor(12V) using SVM in open loop.

microcontroller: Infineon
IDE: Keil Microvision.

I have successfully generated the Space vector which starts rotating as shown in the pic.This space vector PWM is supplied to the Bridge drive(6 MOSFETs). But as soon as I start, a very high current flows. Why is so? Am I doing something wrong?
Scope Video, 3 phase high side FETs


texts: use phones usb for directly controlling and powering something

texts:
I am new to this topic and did a lot of research but could not find a solution to my question.

What I want to do:
I want to attach something directly (I do not want to add a microcontroller) to the micro usb slot of my phone to power and control it (I want to use my phones power to power something else). I will use the 5V voltage that usb can give me (as far as I know I will have to use a USB OTG compatible device, but that is not the issue). So far so good. What I additionally want to do are the following two things:

I want to control the power.

1.a) Is there a way (Writing app or ...) to get my phone to output usb pwm?

1.b) I dont necessarily need the fast rate of pwm. So is there any way (Writing app or ....) to turn on and off the power of the usb output?

Can I read incoming data while powering and can they be outside of the usb protocol? This is supposed to mean: Once my Phone has done its work I want to give a signal onto the D- and/or D+ of the usb cable to tell the phone that it should stop giving power. That signal will not be in the usb protocol but will rather just be some voltage. For that I would need to be able to directly read the usb income and control my phone based on that. Is that possible?
In Short: When I want to be done powering I put a Voltage of e.g. 3.3V onto D-/D+ and the phone notices this and turns of the power.
So the questions are:

2.a) can I power something and read data over the same usb at the same time?

2.b) can I directly read the D-and D+ pins and use them to control my program?

Thank you very much.


texts:
I'm trying to use a specific audio amplifier, TPA3111D1, to power a 10 watt speaker from a microcontroller.  I would like to generate sound from a microcontroller that doesn't have a built in DAC, so I am looking for a good DAC that would work with this amplifier.  The amplifier allows both differential or single audio source inputs and I'd like the DAC to work with 0 to 5V TTL inputs from 16 pins of the microcontroller.

I think 16 bit should be the appropriate size of the DAC but there are so many to choose from.  If anyone has a good tutorial on using a DAC for audio generation from a microcontroller I'd love to see it.  Can anyone suggest a DAC or at least narrow my search down a little bit? Thanks!


texts: I noticed that in many audio op-amps, RC constant is designed so that the cutoff frequency is about 16 Hz. I think that's because the human ear responses to frequencies higher than 22 Hz. But I am a bit confused. If the RC component decides the cutoff frequency, why do they always use values of about 100kOhm and 0.1uF? Can't it also be a different combination, such as 1kOhm and 10 uF. Is that because the current issue?