texts: What's the main differences between a TSSOP and a SOIC and when would you use one over the other?

texts:
I was recently looking at some SPI SRAM chips at Mouser and noticed that a particular IC came in both a SOIC-8 and TSSOP-8 package.  The specs seem identical but the price is different (not by much, but different).

Visually, it looks like you could take a SOIC and push down from the middle to flatten the pins out and you would have a TSSOP.   I know it's not the same thing but it looks like you could.  ;-)

Anyway, given the same specs, why would you choose one package over the other?  Both seem to be as easy to solder as the other (pins not under IC).  Both seem about the same size.

For me, it would seem you would pick the cheaper of the two but there has to be more than that.

Thanks

EDIT

One thing I didn't make clear, is that I am wondering if the differences are just physical or are there others?  I see now that the size difference can be quite large considering....

So I am gathering that if board space is a premium (which it usually is) then use TSSOP.  But then why do we need SOIC at all?

Hope that makes it more clear.


texts: I work in a research lab where we occasionally need to develop electronic driver boards for quantum cascade lasers. The type of signal these handle are digital data streams up to around 10 MHz and output drive current up to 100 ma or so. The board needs to interface with Altera development boards using their proprietary hsmc connector. We have some preliminary designs that work on a soldered breadboard, but the lack of a proper PCB is causing ringing and overshoot, etc. (there are some SMDs involved). Since I'm primarily a software engineer, I'm looking for a basic how-to on spining prototype PCBs using modern tools. Any help appreciated.


texts: Simplify switch network for dual-element heater

texts:
I have a small space heater that each has a pair of quartz radiant heating elements.  Each element is 400 Watts with individual latching button switches.  This allows the heater to operate at 400W or 800W (either of one button pressed or both buttons pressed).

I find that the heater is often too hot and I'd like to add a 3rd option of 200W.  This is accomplished by placing the two heating elements in series across the incoming line.

The ideal situation would still use only two button switches with the heater power selected in binary fashion.  Two buttons gives 4 distinct states: Off, Low (200W), Medium (400W), High (800W).

The existing button switches are SPST and appear to be rated at 10A or so.

I've been doodling and the best arrangement that I can come up with requires replacing one of the button switches with a DPDT version.  I'm having a real problem finding a suitable switch.

I'm hoping that someone can suggest a better alternative to what I have so far:

simulate this circuit – Schematic created using CircuitLab

The 4 combinations of SW1 & SW2 allow for heat selection of: Off, Low, Med, High.

What I'd like is suggestions of how to simplify this to, perhaps, two SPDT switches instead.

Worst case scenario is that I add a beefy DPDT relay controlled by the existing SPST SW2.


texts: Amplifying analog signal from AO of KY-038

texts:
I'm using a KY-038 for sensing sound if I connect the DO pin and set the potentiometer to the highest viable sensitivity then if I make a loud sound it detects and sends an output upwards until 1023. But, as I understand from the schematics of KY-038, only the DO is amplified but not the AO.

So, if I make a sound then the AO does have an effect but since it's already oscillating between 523-534 when no audible sound is present, I cannot detect it because that effect is way too small. Like, it may jump to 540 or maybe 500 but I can't really check for it in code because it's just such a little difference. Also, the idle sound level also sometimes changes its range slightly like instead of going 523-534, it'll do like 512-527 etc.

So, how can I amplify the signal from the AO so that it can detect sound more prominently? Would love it if you could provide clear instructions. (Also, have seen this answer already but the amplification doesn't seem to work )


texts: Mounting Ultrasonic Sensor on Metal Container to Measure Liquid Level

texts:
Is it possible to mount an ultrasonic sensor on the outer metal surface of tank/container to measure the level of the inside liquid ? the gap between the sensor and the metal surface would be 0 mm to 0.5 mm max.

Will the metal surface interfere the waves of sound or it will penetrate the metal due to the tiny gap ?  (Picture showing the idea)


texts:
I have to use an accelerometer in my project. The project demands high accuracy in measuring acceleration magnitude and phase in all the three axes. I am searching for a detailed comparison of using three 1d accelerometers or using a single 3d accelerometer for this project. The comparison should compare the two choices in the following aspects:
1_ Accuracy of measurement
2_ Ease of installation
3_ Ease of writing code to extract information from the raw data
4_ Cost


texts: What is the purpose of the IR-diode Cover on Remote Controls?

texts:
Some electronic devices' remote controls have their IR-diode covered with some glossy, dark acrlyic-glass like screen, others dont and you can directly see (and possibly touch) the IR-diode.

What is, however, the purpose of this cover?

And why do some remotes not require it?

What material is this cover made of?

Why is it dark (doesn't the dark toning diminish the amount of IR light being emitted)?


texts: GPS time accuracy (SIM808 or similar) - process between NMEA sentences and AT command response

texts:
In an SIM808 chip or similar you can get the GPS information with this AT command:

AT+CGNSINF
+CGNSINF:1,1,20150327014838.000,31.221783,121.354528,114.600,0.28,0.0,1,,1.9,22,1.0,,8,4,,,42,,

the UTC time is in the third data field as: yyyyMMddhhmmss.sss

However in the manual the function of AT+CGNSSEQ is described as: Define the last NMEA sentence that parsed.

My question is in general:

how accurate is this time when I receive it from the serial interface of the chip?

Sub questions:

Should I assume that the time between the AT command answer and the last NMEA message that was received by the GPS unit is variable?
Can I compensate for delays in the systems and how?

Delays I expect:

Difference between NMEA sentence coming in and AT command?
Time to process NMEA sentence
Time to read AT command and prepare response
Serial communication time


texts: Displaying data in engineering units on desktop

texts:
Suppose I have 100 numbers of DSPs whose ADCs are converting analog data into digitals ones. The data may be current,voltage, frequency etc. Now DSP deals with counts only it does not understand engineering units like Volt, Amp, Hz etc.
Now I want to display this "count" data in more engineering units on a single desktop. Remember I want to display the data of say 100 DSPs together on desktop.
DSP has RS232 port for communication.
How can I show scaled data from DSPs to single desktop?
Which communication protocol/Interfacing softwware should I use?

For example :
DSP 1--- I=16000 V= 500 F=1000 counts and scaling factor is 0-100 V equivalent to 0-32760 counts 0-10 A 0-32760 and 0-100 Hz equivalent to 0-32760 counts.
How can i display on desktop?

Thank you for the information. Let me simplify my question. How can I transmit data from say 100 numbers of DSPs ADC via RS 232 protocol to a common desktop? I want to transmit the data from DSP to PC which will be pure counts and data will be converted into engineering units in desktop.No floating point operations will be done in DSP


texts: Can the weak-pullup 'H' assignment of std_logic be synthesized, or is it only allowed in simulation? You're probably wondering why I would want to do this: I'm trying to emulate both the master and slave I2C devices inside the same FPGA (internal bi-directional bus), thus I have no external pull-up resistor. I'm not sure what input logic level the FPGA will see when both master and slave are set to 'Z'. I realize that since both devices are inside the FPGA, I could just avoid using the bi-directional buffer, but I'd like to be able to use the same exact i2c master code, as is, and at a later time route it to real hardware.


texts:
If someone were to transmit short wave "Skywave" from the equator in the UTC+0 timezone (Greenwich Time) with vertical polarization, and the receiver is at the equator ~10000km away in the UTC-6 timezone (Galapagos Time), given enough transmission power, what would be the polarization of the received signal?
Assuming that the magnetic and gravitational field strength are consistent in all locations along the path of travel and that the reflections off of the surface of the earth do not affect the polarization.  Also assuming that the transmitter and receiver are both at sea level, and that the reflections off of earths surface are all at sea level on a perfectly smooth surface.  The time is also midnight half-way between the receiver and transmitter, so "Skywave" conditions are optimal.
EDIT: Knowing that the ionospheric radio reflection may or may not randomize the polarization of a reflection, lets simply assume all reflections act as if they are reflecting off of an idealized radio reflector.


texts: Why have electricity travel across the country at 1,150 kV?

texts:
The Powerline Ekibastuz–Kokshetau in Kazakhstan holds the record for having the highest operating transmission voltage in the world, running at over 1 megavolt. Why did they choose to deliver energy this way?

EDIT:

If higher voltage means thinner wire can be used for transmission, why doesn't the rest of the developed world operate at transmissions this high?


texts: Transfer characteristic of two-cascade resistive voltage divider

texts:
Transfer of a simple voltage divider with two resistors (R1 upper and R2 lower) is: $$ \frac{R2}{R1+R2}$$
Now I would like to have a two-cascade divider that looks like this:

Since the output of the first cascade (R1&R2) is connected to the input of the second cascade (R3&R4), we can multiply individual transfer functions which gives us:
$$ \frac{R2 R4}{(R1+R2)(R3+R4)} $$
However, this is incorrect. The correct answer is:
$$ \frac{R2 R4}{(R1+R2)(R3+R4)+R1R2} $$
Question. Where does R1R2 in the denominator come from?


texts: 7 segment LCD works on breadboard, not on stripboard

texts:
I am using a 7 segment 3 1/2 digits "raw" LCD (like this one) using 4 CD4543 controllers and a MSP430. I use one of MSP430's pins to create a 30Hz square wave that I feed into CD4543's phase input. Other MSP pins are used for the latch disable and binary inputs.

The LCD works fine on the breadboard and it's very stable (shows constant contrast over time).

However, when I tried moving the LCD (along with the 4543s and the MSP430) onto a stripboard (using more then 100 thin wires), the LCD kept fading away and behaved weirdly (human proximity or pressing on the wires behind the board would light it up or turn it off).

I checked and rechecked the wiring and could not find anything wrong.
I removed the LCD from the stripboard and it runs fine on the breadboard so it doesn't look like anything was wrong with the components.

What could be the problem that prevents my project from running on a stripboard?


texts: i have a question about a amplifier im working on

texts:
the amp is a radioshack mpa250. I hooked it up, and took the top cover off to see how big the transformer and caps were. theres two 80v, 10000uf caps in there, with a 40.5v transformer... i checked the output of the transformer before the bridge rectifier, its reads 40v after the bridge rectifier it goes up to 110v... im not sure if im reading that, or even testing it right...
The main problem im having is that it seems the transformer and capacitors arnt big enough for the amp, im seeing voltage drops around 20 - 25v, and the lights dim, i guess you have to cut back somewhere (the amp was 180$) i was thinking about putting a bigger transformer inside http://www.antekinc.com/an-10440-1000va-40v-transformer/ (outputs around 10a rms) its 100$, i really think its worth it to do these simple upgrades, the amp has a good design and sounds nice. The transformer hum's loudly (yes its grounded the right way) i think its not strong enough... the caps are rated for 80v, and their pushing 110v dc into them... thats a big problem... i think this amp is starving for power, once these upgrades happen i think its gonna really shine. that is some backround info, but my question is how big of a cap can i put inside there, i mean the peak current draw from that transformer is probably 20a...and the new bridge rectifier i have is good for 25a or so... i just want to know if i could fit a farad cap in there, or something alittle smaller... please get backk to meh, i wanna see this amp work at its ability!! thx in advance.


texts: Transistors - The change in the base current

texts:
I came across this question in my book, it says:

  what will happen to the output voltage if we increase the base current in the figure below?

What confused me in the figure is that the output voltage is the voltage on the load Rc, and I used to think of it to be the voltage across the emitter-collector junction, like this:

In the second figure I would say that increasing the base current will decrease the output voltage, but I don't know what to say in the first case in Figure one.
What is exactly the output voltage in Common Emitter configuration? And what is the difference between the first and the second figures? And what will happen if we increased the base current in the first and second figures?


texts: PMOS soft turn on slower current ramp up to capacitive load

texts:
I'm trying to understand MOSFET soft switch and I know the more common off-the-shelf configuration is to put the capacitor between gate and Vo. However, I'm trying to understand why I can't do it in another way, that is putting capacitor between gate to ground as the picture shown here. I'm using a PMOS here. Can someone help me understand why I can't do it this way to limit the inrush current to load R6? Here, there is a rocker switch that's normally open and will be flipped to close position to turn on the PMOS. I want to know why putting the capacitor between ground and gate of MOSFET doesn't work. Thanks.

Why is my LTSpice running extremely slow when simulation this circuit at the time the rocker switch is closing??


texts:
A system I built uses a commodity siren for audio feedback. In production it's outdoors and 50m from the operator and the volume level is just right. On my bench it's deafening. The tone generator board lacks provision for volume adjustment so I suppose I'll have to attenuate the output.
The whole system is nominally 30W. The resistive component of the horn seems to be about 6Ω. Quite likely this is nominally an 8Ω device.
All the pots I have lying about are for much higher resistances; it seems to me I need to add quite a small resistance. Would I be better off trying to adjust bias on one of the the amplifying transistors? How would you go about adding volume control?
I have already taken the amusingly prosaic step of putting a sock in it. When working on other aspects I simply disconnect the horn but for wiring and system integration checks there's no getting away from it.

For those who like to have the background info...

The module at left is a 30A relay with optoisolator for low trigger current.
The horn tone generator is the centre module in this photo.
Immediately above the tone generator is a garage remote relay module that connects an Arduino digital input to GND when the fob button is pressed.
At right is an Arduino Nano socketed on a screw terminal board.
The round thing at top is a piezo buzzer providing audio feedback on the bench.

Seen in profile along the bottom wall we have

A buck converter adjustable step-down module providing 5V for the Arduino
A buck converter adjustable step-down module providing 6V for the servomotor
A Freetronics microphone module used to detect engine run state so the controller knows about manual engine start/stop.

Yes it really is all held together by industrial Velcro. What started out as a convenience in a rapidly evolving prototype turned out to be an outstanding shock-mount.
The controller and a big diesel water pump are 100m away down at the river. Due to terrain they are barely audible from outside the house and completely inaudible inside. The neighbour's dogs bark at everything else but the pump doesn't seem to bother them.


texts: How to control a flag in two different procedural blocks in verilog?

texts:
I want to rise a flag once I enter procedural block#1, and I want to reset it to zero in another procedural block. Of course I get an error saying the flag is driven by too many drivers. How can I overcome this problem?

Block 1, sensitive to sw (FPGA board switches):

always @ (sw)
flag =1;
begin
case (sw)
8'bxxxxxx01: x2= 13'd1249;
8'bxxxxxx10: x2= 13'd2499;
8'bxxxxxx11: x2= 13'd3749;

endcase

end

Block 2, sensitive to CLK:

always @ (posedge CLK)

        begin

        if (counter2 == x2)
        begin
        counter2 <=0;
        flag=0;
        end

        else
        counter2 <= counter2 +1;

        end

Assuming all initialization are taken care of.


texts:
I'm working on soldering a 3.5 mm female jack to the Thinkgeek Personal Soundtrack Shirt Controller so I can output to any speaker I please, however I am wondering if this is an actual connector I can buy so as to not have to solder in the cable.  The connector in question is the white one in the left of the image.

Worth mentioning the fact that it did have the connector, but it was lost years ago thus leading to me now trying to make it into something useful fun.


texts: Capacitor between mosfet source and gnd?

texts:
This question has probably been answered before, but I am having a hard time finding explanations about the capacitors purpose. I have been looking at schematics of led matrix circuits and you can often see the anode row is controlled by a mosfet. The mosfet usually has a 100 uF capacitor connected between the source and gnd. Why is that? is it just to smooth the  power supply current drop or is there another purpose. How important is the capacitance value, what would happen, if there  was no capacitor.

If you know where I could look this up, just point me in the right direction. Thanks.


texts:
I am a software engineer and I came across this article which states

  If a processor attempts to draw more power than a power supply system can provide (by drawing more current than the system can supply), the result is typically a volt- age drop, which can cause the device to malfunction. Modern processors can vary widely in power consumption with high peak currents; hence, they provide voltage indexing methods that allow the processor to slow down and regulate voltage within a wider margin.

I have read other articles where they explain that you can imagine voltage and current relationship as water hose, where Voltage is equivalent to pressure, water flow is equivalent to current and the diameter of the pipe is equivalent to the thickness of the wire - or resistance. So my question is two fold:

How does drawing more current leads to voltage drop, because voltage and current are directly related, right?
We need both high voltage and high current to cause damage, then why the sudden drop in voltage causes any damage to computers. Causing a drop voltage should only mean less force with which the electrons flow, so it should be opposite to causing damage, isn't it?

I am sure I am missing some basic physics logic here. Can you please clear this for me?


texts: What is the maximum frequency a bridge rectifier can handle?

texts:
I was designing a basic power supply with frequency ranging from 50-60Hz and thought about using this bridge rectifier KBPC50005.
I cant seem to understand the range of input frequencies it can take, its application notes have graphs made for 60Hz load, my input supply's frequency is 50Hz, and i think it might work but this lead me to this question that how can I be sure about it? Will it really work?

What if my input signal's frequency ranges to 100Hz or 800Hz? Will this rectifier work? How low or high frequency can it tolerate?
Or to be more general, what are the factors on which the input frequency characteristics of any bridge rectifier depend? Any ideas?


texts: Can a CPUs speed be increased by (physically) upgrading the CPU clock?

texts:
I don't know much about CPU operation, but I'm learning. I read somewhere that making a CPU work faster is as simple as increasing the clock speed (one  method among many), and that the real limiting factor being electron travel speed in the circuits, which wont be met until extremely high THz rates, or well over PHz.

My question is what would prevent me from speeding up a CPU if I replace the clock with one that ticks at 1+ THz instead of the typical few GHz for modern processors? Assuming I manage to completely prevent heat build up, would such a simple change to the processor boost the speed like this? If not, what other factors have to be considered?


texts: How does specific apps find "hidden" Bluetooth devices?

texts:
Segway has made an electric scooter. It has Bluetooth so I can connect my phone to it. When I open the app, it asks me if I want to scan for devices. I hit yes and my scooter comes up. I can then see statistics and so on from the device.

If I open up Bluetooth settings on any other device, I cannot find the scooter. I know the scooter comes with a specific name (like Ninebot1234), but I can change that name.

I basically want to connect any other device to that scooter, then perhaps try and send some Bluetooth commands to get those statistics.

I want to research more into connecting to a hidden Bluetooth device, so I don't have to specify the Bluetooth address, but I'm not really sure how I should approach that. What kind of technology or software lies underneath making a hidden Bluetooth "network", and how does the app know which Bluetooth devices to scan for?


texts: Current sink - power and heat calculation

texts:
My goal is to build a constant current sink to profile different batteries. The maximum paramters are
Vin=4.2V
Isink = 1A
Resulting in a maximum power of 4.2W
The circuit is equivalent with the following:

To select a suitable mosfet i would have to know
1.) How much will the mosfet heat up
2.) What type of heatspreader / cooler would be suitable to cool a common type mosfet (TO-220)
3.) Are there any mosfet that can operate at the given parameters without a cooling device!


texts: Understanding in-loop compensation for capacitive-loaded OpAmp

texts:
I'm trying to understand the in-loop compensation for a simple amplifier loaded with a capacitive load, as seen in this article from Analog:

http://www.analog.com/library/analogdialogue/archives/38-06/capacitive_loading.html?doc=CN0343.pdf

I understand how the compensation works and all the stability matter. Though, I can't understand the simplification used in the article to find poles and zeros of the feedback network's transfer function. Why are they first shorting \$C_f\$ and considering \$C_L\$ alone and then opening \$C_L\$ and considering \$C_f\$ alone?

I am familiar with OCTC and SCTC (time-constants method) and all the low-frequency and high-frequency approximation by shorting and opening capacitors, but here it doesn't make any sense, because \$C_f\$ is smaller than \$C_L\$ in real-world designs: so we should consider \$C_L\$ as a short-circuit in an hypotetical high frequency analysis and \$C_f\$ as an open-circuit in a low frequency analysis.

Though, this would give wrong results because two of the zeros should be at about the same frequency to get a good compensation, so we can't split the analysis in low and high frequency.

Anyone with a good hint on how they did this kind of analysis?

Here is the relevant section of the document:


texts: Power plane layers visualization in Altium

texts:
So I set one of the internal layers in a 4-layer board as a "plane" layer and now the border of this layer along with every via and hole is drawn like this:

As I understand this is the pullback line, but it is really distracting. Is it possible to hide this huge green line without hiding all the polygons? Is this how it is supposed to be?
Thanks


texts: FPGA simulates well and passes timing check but fails in PCB

texts: So you have finished your FPGA design.  You have simulated it with an extensive test bench created by a different engineer and it works, event at speed after it has been compiled, placed and routed.  No errors or warnings from the fpga tools.  You go to lab and think, OH BOY, I'm going to program the FPGA and watch this work, but it doesn't.  No data gets through, no signal move.  Nothing.  You check the power on the board and there is more than enough, even for the FPGA boot cycle. You check the routing on the PCB for critical signals, and they look good.  What do you do next???


texts:
I am trying to build a Collpitts oscillator using an 8MHz crystal, but the signal I get, is completely distorted. Any idea why?

The yellow signal is probed at the output, while the pink is probing the base of the BJT.

To start with I thought the problem was that my BJT was not in linear region, so I increased the load resistor to 2k to reduce the amplitude of the input signal, but the distortion was still there.

Do I have some secondary oscillation somewhere? Any idea how to fix it?

PS: The crystal is 8MHz not 8mhz.


texts:
What can I learn from an equivalent circuit model of photodiode like the following?

I've actually gone the whole way beginning from doping semiconductors through each noise term to the amplification gain.

Now I'm at the application stage and I stumbled over this circuit and noticed it is quite common. But since I don't see any technical purpose of it, I guess it is constructed to understand the photodiode itself in a technical way. But what does it tell me really? And why is nearly everything parallel to each other?

I've seen this EE.SE question (equivalent circuit for solar cell) which is quite connected, but doesn't touch it directly. However, it hasn't been answered yet anyways.

edit

To be more precise: I'm more interested in the circuit itself and less in the single parts of it. I probably can google each part of it but what is about the circuit itself?


texts: Is it safe? 9v from 12 to 3.3 on ATX PSU

texts:
I've an ATX PSU that I've modified to run without a motherboard, to power the many (6 or so) low amperage 12v and 5v devices at my workspace, to reduce # of power adapters plugged in and to provide dedicated toggle switches for some devices.

I've also got a 9v device, so I was wondering if it's safe to create a 9v line for that device by using a 12v line as the positive, and a 3.3v line as the negative.

My guess is that the answer is "no" because the PSU is not designed to have electrons flowing out of 3.3v into 12v, but perhaps I am wrong!


texts: What software is used to design and simulate Mac computers, iPod and iPhone circuits?

texts:
Apple computers are great. I love my MacBook, however, I haven't been able to find any decent circuit design and simulation software that runs on a Mac. This brings me to a question: If Mac OS X has no professional electronics design software, then Mac electronics are designed on PC's?

This would be interesting news for "MacFanaticsPCHaters" and for all of us trying to develop hardware on a Mac.


texts:
Just some clarification on the open-drain concept for I2C.
Open-drain configuration is used mainly to avoid any sort of short circuit in case one device is one line is being pulled low by one master while the other master is pulling the line high. And how it works is by whichever master pulls the SDA line low first gets to control the slaves, and by pulling the SDA line low in this diagram means setting the gate voltage of the MOSFET high, isn't it? Because when it's high, the output/drain is pulled low. If that's the case, why is the gate labelled as SCKN1 OUT as opposed to SCKN1 IN?


texts: Is diode with forward voltage ~0.15v faulty?

texts:
I tested a diode model SB360 PFS which it showed about 0.15 forward voltage. The reverse voltage is zero.

Looking the diode specification I read that Vf is 0.49v to 0.68v. So my question is if this diode is faulty.


texts: Does charging near maximum C rate have the same effect as high battery levels?

texts:
We know: The maximum C-rate decreases with the increasing charging state.

Let's assume an 2 Ah Lithium-Ion or Lithium-Polymer mobile phone battery. (2 Ah is considered tiny in 2018, but this is just an example).

The internal charging current is 3 A (1.5 C) at 0% to 50% (couldn't it be higher at 0% than at 50%?)

At 50%, it starts decreasing, so it reaches 1C (which is 2A) at 75%.

Then it decreases from 1C to 0.1C throughout

My question is:Does the same charging speed at a higher battery level (e.g. 75%) produce more heat and consume more lifespan, because it is closer to the maximum possbile C rate?

It is said to be unhealthy for a mobile phone battery to be charged to indicated 100% due to internal pressure.

Would this internal battery pressure also take effect if I charged the battery too quickly at a high level such as 85%?


texts: Which is the acquisition time of the SAR ADC of a LPC1768?

texts: i'm trying to design a RC filter to drive the ADC of the micro-controller LPC1768  and i need to know the acquisition time of it (which is not in the datasheet). I'm using this article as a design guide. Thank you. Regards


texts: Selecting correct current limiting device

texts:
Requirement: During an external test 20W of power will be drawn from my supply circuitry for 1 minute. My mission is to implement a solution that limits the power draw to a level below 20W in under one minute.

Background to the requirement: it is somehow considered that 20W is a power at which enough heat could be generated that a danger of fire is at hand.

My system: I am designing a system containing a MCU and a couple of things to be measured and controlled, among them a DC motor. I have a safety requirement which says that when 20W is drawn from my supply circuit the power drawn from it must be limited (permanently by fuse or temporary by another measure) in order to prevent heating and hinder unintended short-circuits. My power supply is a battery pack of 10,8V which during short circuit test gives 25W and 4A in a small resistor for longer than a minute, during this lapse the battery voltage sinks a couple of volts.

Now to the problem: Under normal circumstances I would use a usual fuse, but there is one big quirk, which is that when the  motor is on, it draws around 2,5A from the supply (might have higher inrush as well) (however the voltage sinks to a level so that the effect in the motor is below 20W). This makes it hard to find a reliable solution with fuse in the unclear region between 2,5A and 4A.

I have this far looked on thermistors, active current limiters, fuses and polyfuses. But none of the options look optimal, especially because the solution should preferable be reliable (as this is a safety measure), and active devices are not preferred.

And advice on design of a current limiting solution is appreciated, the more elaborated, the better.

Also, what percent of motor's nominal current draw should the fuse be in general case? From what I have read at least 150% - am I correct?


texts: Why we use 330 ohm resistor to connect a LED?

texts:
Possible Duplicate:
  Correct formula for LED current-limiting resistor?

Why we use 330 ohm resistor to connect a LED ?

I mean:

the R is by practice 330 ohm.

Why this value? How do I calculate it? what's the purpose of it?

Is there a specific parameters in LED to get this value?


texts: Shouldn't an antenna with a higher gain provide a stronger signal in the designed direction?

texts:
I have a Wi-Fi access point with six antennas: three for 2.4GHz, and three others for 5GHz. The spec of the access point indicates that the gain is 4 dBi for 2.4GHz antennas, and 6 dBi for 5GHz ones (see the last line on page 2 of the datasheet).
I tried to see what would happen if I replace three antennas by the ones rated 8 dBi (such as these), first replacing the 2.4GHz 4 dBi ones, and then doing the same with the 5GHz 6 dBi ones. During the experiment, I positioned a mobile phone in a different room (on the same floor), and checked the dBm indication with Network Analyzer app. The antennas were positioned to point towards the ceiling.
I expected that once the antennas were replaced, it would make the signal more directional, which means that my neighbors on other floors would receive less of it, while my Wi-Fi devices situated at the same floor would get a stronger signal.
In practice, for 2.4GHz, the signal was just slightly stronger, but not by much: 55 dBm instead of 60 dBm. 5GHz signal was weaker—59 dBm with old antennas, 61 dBm with the new ones.
What could explain that?


texts: powering an old 9V multimeter with a 6x AA battery pack

texts:
I have an old Nimex NI2100 multimeter that is working fine with 9V batteries.

Btw i'd like to power it with 6x AA batteries instead so i've bought a battery holder and wired like this:

I've checked with another multimeter the voltage beetween the +BAT and -BAT pins on the PCB is 8.4v.
However it does not turn on!

Is it possible it has some kind of protection for using with different kind of power sources?


texts: STM32F429 / STM32F439 read-while-write from two memory banks. Prevents stalling CPU?

texts:
I have been reading up on the STM32F429 flash memory (2MB version). From the STM32F4 reference manual I found out that it has two memory banks and supports read-while-write (RWW), which means it can read from one memory bank while writing to the other.

My application has real-time constraints and I want to know what the worst-case situation is.

Lets say the microcontroller application is running from memory bank 1 and I want to write/erase data on memory bank 2. I have some questions after reading section 3.4 to 3.6 in the reference manual.

Is there any situation where the microcontroller application in memory bank 1 needs to write to flash during normal code execution?
If yes to question 1. Does this mean the application code execution have to wait until e.g. a sector erase is done on the memory bank 2 as it does not support write-while-write? Or is it someway to give memory bank 1 priority is it needs write/erase access?


texts: About designing AND gate using N-type mosfets: first image is used everywhere. However, it uses an additional inverter part.  Is it not possible to design the circuit like below (second image)? If not, what is the reason for that?


texts: MOSFET for reverse polarity protection of a LiFePO4 battery powered circuit?

texts:
I am looking to protect my circuit from a reverse polarity event. I found suggestions for using a MOSFET, particularly a p-channel type. Does anyone have a specific recommendation for a device to use for the LiFePO4 battery (about 3.2V nominal) technology? I am not totally sure about this, but would it be possible to select a MOSFET that has a Vgs that would also protect the battery from being over-drained?

Edit: Max current 500mA. Also looking to save electrons, so the device needs to be efficient both in on and off state.

Edit 2: Looking for a specific P-MOSFET or spec requirements to check in the data sheet when ordering parts to try out. Thanks.


texts: Average power can be measured by wattmeter, so why in the attached example it doesn't function properly- doesn't show 0 W?


texts:
I've read that the permitivity of FR-4 is around 4.5, however I would like to measure the permitivity of an actual double sided copper clad board, the way I am thinking is to measure the thickness of the substrate and calculate the capacitance of a parallel plate capacitor with air between it, then measure the capacitance of the copper clad board by attaching electrodes to either side using a good LCR meter. The ratio between the measured value and the calculated value should give me the relative permitivity.
Im not looking for extreme precision here.
What do you guys suggest?


texts:
I was so stupid to leave a Ring rsc 516 smart charger in the rain. Hopefully, only the fuse is blown.
However, I am not sure where the fuse is?

could it be the black thing on the photo?

I did a continuity test, but there was no beep.


texts:
on an amplifier I found at the input 4 resistors of 0 ohms.
What is their role and how does this circuit work?


texts:
I am relatively new to the world of guitar pedals, and I have recently (after a few failed attempts) built a successful Bazz Fuss.

Although I've successfully  built it, I'm not sure how exactly it works. I would like to learn what each part in it does.

Here's the circuit:

My main questions are:

What are capacitors doing in the circuit?
What is diode's purpose and why is it connected this way? I've thought it would be connected straight from the capacitor to  the transistor base.
And of course, how fuzz works (in general).


texts: Problem with Atmega 168 USART receive interrupt ,while communicating with Xbee

texts:
Before decreasing my reputation please let me know what I have done wrong. Bear with me as I am a newbie.

I have written a program so that a receiver radio module sends 1 when it receives an 1 from a broadcaster module.I am using XCTU with a Xbee as the broadcaster.Here is the code.

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

unsigned char data; //to store received data from UDR0

//Function To Initialize UART0
// desired baud rate:9600
// actual baud rate:
// char size: 8 bit
// parity: Disabled
void uart0_init(void)
{
 UCSR0B = 0x00; //disable while setting baud rate
 UCSR0A = 0x00;
 UCSR0C = 0x06;
 UBRR0L = 0x06; //set baud rate lo
 UBRR0H = 0x00; //set baud rate hi
 UCSR0B = 0x98;
}

SIGNAL(SIG_USART0_RECV)         // ISR for receive complete interrupt
{
    data = UDR0;  //making copy of data from UDR0 in 'data' variable
    if(data == 0x31)
    UDR0 = data;                //echo data back to PC

}

//Function To Initialize all The Devices
void init_devices()
{
 cli(); //Clears the global interrupts
 uart0_init(); //Initailize UART1 for serial communiaction
 sei();   //Enables the global interrupts
}

//Main Function
int main(void)
{
init_devices();
    while(1);
}

Now the problem is that when I send an 1 we do not get any response from the receiver. We tried the same thing with an Atmega 2560 based devboard as the receiver and the program worked like charm. But when we try it with Atmega 168 nothing happens.
Well with Atmega 168 we use internal crystal of 8MHz with 8 prescaler ie 1MHz system clock so I have used

 UBRR0L = 0x06; //set baud rate lo

Used for dev-board

 UBRR0L = 0x5F; //set baud rate lo

to get 9600 baud. But no matter what I do the interrupt just isn't working. We tried running a toggling cycle in the main program to see it that is working or not and that worked too. But when ever I transmit a signal via XCTU (terminal software) the receiver does not go to ISR like it is supposed to.

Please help. Ask me back if anything I need to clarify.


texts: Battery voltage quickly drops when measured

texts:
I have a 9V battery that has around 9V when I first apply the probes for a multimeter. However, if I hold the probes on it for a few seconds, it starts dropping... about 0.10 V per second. And it just keeps going down.

I am guessing that this battery is shot but what is the mechanism for this? Why would it show a high voltage and then fall off instead of just showing low/no voltage from the beginning?

Is this because maybe the electrolyte is still able to produce power but there's something in the electrodes causing a super high resistance that just increases under load?


texts: Why does noise-figure of components become less significant further down the chain in a cascaded network?

texts:
I understand mathematically why this happens, but I can't intuitively get my head round this idea.

To clarify this is the cascaded noise figure equation:


texts: How input resistance related to better amplification in transistor circuit

texts:
These figures are from book by Sedra/smith.
I have a doubt regarding input impedence or resistance (Rin) shown in figure.
In book it is written that "The input resistance (Rin) represents the loading effect of the amplifier input on the signal source. It is found from Rin=Vi/Ii"(in figure).
it started with   common emitter configuration (small signal π model shown in 1st figure  ) and then author  introduces another model( CE amplifier with an emitter resistance Re ) with slight modification shown in figure2 and one of the  main motive to add emitter resistance  is increase input  resistance(Re)
I am not sure  ,how increasing input resistance lead to a better amplifier (specially bjt circuits shown in figures )?
Specially after adding emitter resistance , voltage drop across Rπ (π model of CE with emitter resistance)  decreases which causes lower amplification that's why I asked this question
There are lot of questions of input impedence on web but i hope someone  answer it for that particular  amplifier circuit rather than general one.


texts: Creating an ASM file that will return the characters located in 8 consecutive registers

texts:
I have to create an ASM file for the PIC18F452 that does the following:

(a) define the label MapName as the first of 8 consecutive registers containing a null-terminated string of not more than 7 characters.
(b) access an 8-bit unsigned integer variable called MapIndex which was declared in a C file.
(c) define an ASM function getMapChar which can be called from C using the function prototype char getMapChar(void). The function should return the appropriate character when the value of MapIndex is <= 7 or the value 255 if MapIndex is > 7.
(d) make the labels MapName and getMapChar accessible to an external C file.

My code so far is shown below:

; Configuration word : WDT off, power-up timer on, code protect off, RC oscillator
list = p18f452
            MapName         equ             0x20
            MapName1        equ             0x21
            MapName2        equ             0x22
            MapName3        equ             0x23
            MapName4        equ             0x24
            MapName5        equ             0x25
            MapName6        equ             0x26
            MapName7        equ             0x27
            CurrentChar     equ             0x28

extern      MapIndex
                            org             0x00
                            goto            getMapChar

getMapChar                  movlw           0x00
                            movwf           MapName7

GLOBAL      getMapChar
GLOBAL      MapName

END

I have already done parts (a), (b) and (d) but I am having some problems with writing the code that moves through each of the consecutive registers automatically using the value of MapIndex. Could anyone help me please? It would be much appreciated.


texts: How to decode morse code with digital logic

texts:
I have been curious as to how one might implement a morse code decoder with basic digital logic (no microcontroller), mostly as an exercise. I could decode individual letters with a state machine, if I had asynchronous inputs such as dot, dash, and pause. My problem is essentially in generating those outputs from a raw source like a telegraph key.

Is there a good circuit that can detect when a signal goes high for a certain amount of time? I would need it to send one signal when it is up for a short time and then goes low, and another signal when it stays up longer (three time periods for a dash vs one for a dot). I also need a signal when it stays low for three periods for a letter break, or around seven units for a word break. It needs to be fairly liberal with its timings, as it is intended to decode manual entry, not computer modulation.

It would be super nice if it used minimal components and if I could use a potentiometer to adjust the time period.


texts: Is Inductor peak current same as the Inductor Inrush current

texts:
I am using a DC-DC converter which is having an inductor rating of 68uH and 2.05A.

Output Voltage of dc-dc is 23V and output current max is 300mA

Schematic :

I am using a current probe and measuring the current through the inductor.

When I turn ON the DC-DC converter, the Inductor draws 10.75A. Should I consider this as Inductor Inrush current or peak current? If I consider this as Inrush current, as I do this during start-up of the converter, then how to measure the peak current of the inductor?

And since the inductor is rated for only 2.05A, won't this high current damage the component even though it is for a short duration?

Current probe is set as 0.1V/A in the probe and 0.1V/A in the scope as well.

Inductor Peak current (below is the waveform captured during the start-up of the DC-DC converter):

Inductor RMS Current (below is the waveform captured during normal running condition of the DC-DC Converter) :


texts:
I'm planning to assemble a circuit this weekend; it is basically an attiny85 with a USB interface. The circuit is well known on the internet; see for instance this schematic:

(Image taken from http://codeandlife.com/2012/03/03/diy-usb-password-generator/)

Now, currently I don't have any zener at home; I hope the local supply has them, but  couple of times they didn't have even the most basic components, so there is some risk I will not be able to have them by the WE. So, here comes the question.

Can I substitute the two zeners with two blue leds? I know that the zeners have a steeper curve, so I will not have stable 3.6V (or better, a slightly lower voltage) on the lines, but... Is this really a problem for USB lines?

I read question LED as Zener: is this a good way to lower the BOM cost?, and there the main concerns were about the stability of the voltage (and in that case they were not an issue). Do you think there can be issues with USB? Did you already try that?

Thank you


texts: Do I need to make a timing report for min/max at Static Timing Analysis in Four categories of timing paths?

texts:
I've been studying to understand Static Timing Analysis aka STA.
One of what I can't understand is whether I need to make a report timing for min/max at Static Timing Analysis in Four categories of timing paths?

Should I have to take care of each 4 category path to make a timing report? If Yes, Why? Or just I need to make one MIN/MAX timing report? Why?
EDIT:
Could you guide me a description of solution for each category's a timing violation? I think, in R to R path case, it will be one of the solution for adding a F/F pipeline for setup violation and insert buffer for hold violation.
But, No idea else at all. Could you guide for me for 3 else categories in setup and hold violation case?


texts: Configurations for charging batteries of varying voltage from one source for RV

texts:
I have wired up a solar system in my travel trailer, using a 7s1p 48V (58.7V) pack from used Nissan Leaf battery modules. I am now making a 12 volt battery from a bunch of LiFePO4 18650 cells I have from dead tool batteries as a backup battery, so the basic appliances still run if the inverter kills the main battery (all batteries are wired correctly with a BMS).
I am trying to figure out the best and safest way to charge the small battery and also connect it, so the batteries charge using shore power and the truck while traveling.
Originally, I wanted to have the trailer's converter boosted to 58.7V into the big battery, then that bucked to 15V from the big battery for the little one. The problem is that the converter's output is also the DC input for the trailer, so wiring it like this would make a loop between the batteries.
My first thought is to solve this with analog relay circuits that reroute, depending on whether the converter is putting out or not. I came here to ask if this is unwise, because it seems like it would work but is also a little risky.


texts:
Would it not be ok / safe to take a surge protector style power strip, cut the mains cable in the middle (or maybe slice it open and just fish out the load and neutral wires so that the ground wire is intact), splice in a 600 VA isolation transformer and then use that Iso Power Strip (tm) for up to 5 amps of audio gear like rack equipment, maybe small active speakers like studio monitors and the like?

Are there any failure modes to look out for?

Would it not provide superior protection from surges and the like?

Would it not reduce ground noise?


texts: How do you find the phase lag of the current in this FM demodulation "discriminator" circuit?

texts:
I need some help understanding this discriminator circuit for FM demodulation.
(L1, C1) is the primary LC tank which resonates with the carrier frequency, whose FM signal is applied at V12. As the FM signal oscillates according to the signal, the instantaneous voltage and current amplitudes of the LC tank vary across the Bode plot for the circuit.
The RC filter then picks out the AF signal from the varying amplitude due to the signal's skipping around the amplitude. In particular it does so according to the voltage relations between that across L3, and the two halves of the centre tapped secondary.
Warning: I don't understand transformers comfortably yet.
Questions:
Most important:

When the LC tank is above or below resonance, how do you find the phase of the current and voltage through and across L1?
When the LC tank is above or below resonance, what is the phase of the voltage across L3?

Just to verify:

Are the voltages and currents of L1 and L2 in phase / phase difference of 180 degrees?

Do the capacitors C and C4 cause a double 90 degree phase shift (180 degrees) on the voltage across L3?

I care about 1) because I don't know how to currently explain to myself why the phase of voltage across L1 and the current through L1 can be anything else than 90 degrees. Why? Because the voltage across L1 is di/dt which is a 90 degree phase shift off of the current through L1.
I care about 2) because in combination with 1), knowing the phase of the voltage across L3 would allow me to understand the voltage relations for the RC filter circuit. 3) Would allow me to understand the same. 4) Is supplementary.


texts:
I have a 12V "non-spillable sealed lead acid battery" (the UPS type) that is labeled to be 9Ah (it is almost new). When I fully charge it and then discharge using a discharger that counts ampere-hours (at 0.5A), it measures only about 6Ah.
Is this expected behavior, or should it be closer to the rated capacity for a properly functioning battery?
Also, how much does the discharge energy depend on the current at which it is being discharged? Label says "9Ah/20HR", does this mean that optimal capacity can be reached when discharging for 20 hours (which would be 0.45 A)?


texts: Can I store all channels from the signal coming from a digital antenna?

texts: Whatever signal comes out of a digital antenna carries many basic broadcast channels (ABC, FOX etc.) Once this signal reaches the TV, some extraction circuit extracts (or tunes to) the channel I want to watch.  If all this is true, then, why can I store the raw signal coming from the antenna on a device, and extract the desired channel(s) later as needed?


texts: Why is there a wait at the end of a VHDL test case?

texts:
A template for a test process looks like this:

process
begin
  -- for example x <= '0' after 5 ns;
  -- ...
  wait;
end process;

Is this wait required? Why would we wait forever at the end of a test?


texts: I am trying to be able to dynamically switch two wires on a brushless motor ESC for a Quadcopter. The plan is to wire an arduino to the flight controller so that I can program it to switch the ESC direction when needed. The problem is that I don't know of a good way to do this. I could use two mosfets on each ESC, but I'm nervous because they're 20A ESC and I don't want to use heatsinks to save weight. I can't find suitably small DPDT relays that can handle the current either. Any ideas? Please note: I'm not an electrical engineer, but more accurately described as an electronically literate Aerospace Engineer, so if you can dumb down to my level, it would be appreciated. Thanks!


texts: SPI Half-Duplex for the Holtic HI-3593 ARINC429 IC

texts:
I am having some problem understanding half duplex SPI. My understanding of SPI is when you send a byte you read the garbage byte, and if you want to read a value you send a dummy byte to read the value. But for the Holtic HI-3593 chip, this is what it says:

  For the HI-3593, each SPI read or write operation begins with an 8-bit
  command byte transferred from the host to the device after assertion
  of \$\small\overline{CS}\$. Since HI-3593 command byte reception is
  half-duplex, the host discards the dummy byte it receives while
  serially transmitting the command byte.

My questions are:

Do I need to have an explicit command to read the dummy/garbage byte or is it taken care of?
To read a value, do I need to send a dummy byte?


texts: On my Arduino, why is this LED always on, even though I told it to turn off?

texts:
I am a software developer trying to understand how computers work at a lower level.

I have purchased the Arduino Uno Microcontroller and I have followed all of the tutorials from LadyAda.

I have noticed that the LED (not the power LED) is always ON unless it is flashing even if I supply the following program, which clears the memory and should switch off the LED:

#include <EEPROM.h>

void setup()
{
  // write a 0 to all 512 bytes of the EEPROM
  for (int i = 0; i < 512; i++)
    EEPROM.write(i, 0);

  // turn the LED on when we're done
  digitalWrite(13, LOW);
}

void loop()
{
}

Why is the LED always on? I have Googled this and have read a few similar questions on another forum like this, but I have not yet found an answer.


texts: Multiple input to single output converter and vice versa

texts:
First question so please forgive any mistakes.

I'm trying to design a system by which multiple LEDs are controlled by multiple switches, but without using as many wires as there are switch/LED pairs.  I'm planning to have roughly 20 momentary switches connected to the same number of set-reset latches which control LEDs.

I'd like to know if there are any chips or circuits I can use in order to take these 20 inputs, compress them down into as few wires as possible so that I don't have to cable manage 20 wires (which, for my application, will be unfeasible), then provide the same number of outputs at the other end.  The outputs will only need to provide a brief pulse along the correct line, due to the set-reset latches I'm using, and no two inputs will be able to be activated simultaneously.

Thanks all.


texts:
I have  a circuit whose the purpose is to reduce the EMI by "moving" the switching frequency around a value. I would like to understand how this circuit affects the switching frequency, i.e. how it affects the oscillator frequency of the UC3845. For this, I need to understand how the UC3845 is working. Finally I would like to do an FFT for seing how it change the frequency spectrum.

Here is the datasheet: https://www.mouser.fr/datasheet/2/308/UC3844B-D-1814882.pdf

According to the datasheet the frequency is set according to a capacitor Ct and a resistor Rt. It is mentionned that the "capacitor Ct is charged from the 5.0 V reference through resistor Rt to approximately 2.8 V and discharged to 1.2 V by an internal current sink." I can predict the charging time of the capacitor but with the informations given I can't predict what would be the discharging time... as I do not know the sink current. Apparently the sink current or the capacitor depends on the deadtime that we want to have." During the discharge of Ct, the oscillator generates an internal blanking pulse that holds the center input of the NOR gate high. This causes the output to be in a low state, thus producing a controlled amount of output deadtime" The output is the pin linked to N MOSFET. So it is opened. Well, I though "deadtime" was the time when the energy in the inductor is null, it is only possible in DCM. Nevertheless in the datasheet it seems to mean that the MOSFET is just OFF. Did I do a mistake?

What is interesting, or (what I learnt) is that the resistor Rt and the capacitor Ct do not only set the switching frequency but also the deadtime.

Nevertheless, I do not know how to model the oscillator without knowing the current drawn from the capacitor by the current sink. That's why i am looking for an LTspice model of this IC.

Thank you very much and have a nice day!


texts:
We were given a circuit with 7 resistors and 3 voltage sources

For emf sources, \$E_1=120V\$, \$E_2=60V\$, and \$E_3=30V\$ while for resistors in ohms,\$R_1=10\$, \$R_2=5\$, \$R_3=20\$, \$R_4=8\$, \$R_5=12\$, \$R_6=6\$, \$R_7=8\$. Nodes are indicated in small letters (a-j). Loops \$abefa\$, \$abcdefa\$  and \$aghcdijfa\$ are assumed clockwise while the loop \$cbedc\$ is counterclockwise.

I applied Kirchoff's Current Rule in nodes \$b\$ and \$e\$:

\begin{align}
I_1+I_3 &= I_2\\
I_4+I_5 &= I_2
\end{align}

And then I apply the Voltage Rule: Loop \$abefa\$:
$$120-I_1R_1-I_2R_2-30-I_4R_4=0$$

Loop \$cbedc\$:
$$60-I_3R_3-I_2R_2-30-I_5R_5=0$$

Loop \$abcdefa\$:

$$120-I_1R_1+I_3R_3-60+I_5R_5-I_4R_4=0$$

Since I have 5 equations already with 5 unknows, hopefully I should solve these values.

From 1st and 2nd equations, \$I_4 = I_2-I_5 = I_1+I_3-I_5\$. Setting \$I_4\$, and \$I_2\$ in terms of \$I_1\$, \$I_3\$ and \$I_5\$ only and substituting them to equations 3, 4 and 5, I get:

\begin{align}
23I_1+13I_3-8I_5&=90\\
18I_1-12I_3-20I_5&=60\\
5I_1+25I_3+12I_5&=30
\end{align}

Luckily my calculator supports systems of equations for 3 uknowns, but then I get a math error, which could indicate infinitely many solutions? Maybe I incorrectly applied Kirchoff's rule but I don't know where. Also, I verified if the circuit works properly using an online circuit simulator and yes it worked well with indicated current and voltage drop values within each resistor. https://www.falstad.com/circuit/ (The circuit setup installed in the simulator is identical to the image). We are asked to solve this using 4 methods (Nodal, Maxwell, Superposition and Kirchoff) and I started with Kirchoff.


texts: Why is it usually the case that the negative rail for ICs needs more decoupling capacitance (has worse PSRR) than the positive rail?

texts:
That the premise in the question seems to hold can be seen from various sources, including:

comparing the datasheets of various clones of LM317 and LM337 (too many to list, but generally the datasheets for the latter recommend more decoupling on input, about an order of magnitude more than for the former, e.g. TI's datasheet for LM317 recommends 0.1uF input/supply bypass, whereas the one for LM337 recommends 1uF for the same.)
related to the above, the TI datasheet for uA78xx has a split rail power supply schematic where the decoupling for the positive regulator is less than that of the negative one. This is reproduced below.

the Analog appnote MT-101 shows worse PSRR for the negative pin than the positive pin:

So the question is why is this asymmetry usually present.


texts: What's the Laplace transfer function of a moving average?

texts:
What is the Laplace transfer function of a moving average?
$$y_k=\frac{x_k+x_{k-1}+x_{k-2}+x_{k-3}+...+x_{k-N+1}}{N}$$
I tried to get it from the z-domain transfer function using conversion tables:
$$\frac{y_k}{x_k}=\frac{1+z^{-1}+z^{-2}+z^{-3}+...+z^{-N+1}}{N}$$

But unless I've read them wrong they don't have the "bricks" I need to get me anywhere.


texts: Can't use PROGMEM attribute with non - const variables

texts:
In an ATmega32, I intend to use the program memory for writing too but I am getting a

variable 'var' must be const in order to be put into read-only section by means of '__attribute__((progmem))'

error. The reason I thought I can use the program memory for writing too is that the SPM instruction is supported in the device I am using. So would you have any suggestions why I am getting this error and what can do to use the program memory for writing too? Thank you very much.

Best regards


texts: Multiplexer between Capacitor and Inductor (Tank circuit)

texts:
I am trying to design an inductance and capacitance meter with multiple scales, to achieve this I thought a multiplexer can do the job, but it didn't.

My question is: What is wrong in this design and how can I select between the capacitors without a multiplexer?

L1 is the inductor plug.
The meter should measure the tank circuit resonance period using a comparator.


texts: Understanding the polarized relay concept

texts: During the selection of relays for my project I got to know about polarized relay which I had never heard of before. Could somebody please explain how exactly it works and its areas of applications.


texts:
Is the following sign a switch and if so, what kind if switch is it exactly?

It is used in the schematic of the ABB Eden (Adam & Eva) Module.


texts: Calculating steady state output using Laplace transform

texts:
I've tried to obtain the the steady state output with the help of final value theorem and multiplication properties of Laplace transform.But I'm not sure whether I've solved the problem correctly or not. Please let me know if any corrections are required.

This is the question.

This is the approach I've tried. The solution is 45. But I'm not sure whether I've made the correct assumption of input signal x(t) as a step signal with amplitude 5.


texts: Skype Phone Project - Help with Audio Amplifiers Selection

texts:
I am doing a project that involves using a landline phone to work as the speaker and microphone for Skype calls. A representation of the final design is given below.

I have a landline phone in which I will remove all the internal circuitry. In this phone I want to build and add my own circuit. Only the headset of the phone will be used.

The mic and speaker of the headset, connected to an RJ9 connector will be first converted to a 3.5 mm mono speaker and mic connection. This will be connected to the PC using a miniature USB sound card.

When the user wants to use skype, he will dial from the PC and use the headset to converse. This much I can do. I also want the output from Skype to be routed to an external speaker (built into the phone case) if the user presses the Push-to-Talk button, thus enabling him to listen on to the conversation without talking.

Here is where I am stuck.

When the user puts the telephone headset down while on a call, I want the mic to be muted and the audio from the PC routed to the internal speaker in the telephone. To achieve this, I will have to switch the audio source from the PC from the headset to the external speaker. I am not able to decide how to accomplish this given that the amplification levels of the headset and speaker will have to be very different. Can anyone help me with selection of a set of IC's that will allow me to do the same.
I want the mic to be turned off when the telephone headset is put down while on a call in skype.

I will be using a microcontroller board for managing the IO's (mostly an Arduino Nano).


texts:
Today I tested a power supply (a large wall wart) with my multimeter. It is labeled as supplying 13.8V but the multimeter was reading  20V. I tested other power supplies to make sure its not the meter and they where spot on.
My question is what could make this voltage high? The wall wart is rather old; probably ten plus years.


texts: Can a Doppler shift of 3Hz be detected in a frequency of 1.2 GHz?

texts: Well! I am working on a project where i am supposed to detect a frequency shift of 3HZ in a carrier frequency of 1.2 GHz. My team has decided to bring down the frequency at about 100Hz or less where shift is detectable. Theoretically, a shift of 3Hz can be detected in 100Hz signal. However, in real life, will it be possible?


texts: How to prevent circuit from shutting down when motor drain too much power

texts:
I have a device which has motor and circuits with PLC. This device is connected to a 12v battery which is powering the PLC and motor. Everything is working fine but when the motor's load is heavy, it draws the power from the battery and cause the PLC to shut down due to lack of power. And happened in milliseconds. My PLC will then be rebooted. This is a problem for me.

Beside having an isolated power source for PLC and motor any other ways which we can prevent the PLC from being shutting down? Is there a way to drain piority power to the plc?


texts:
I've made many RC circuits and RLC circuits ( series and parallel resonance).
I want to make sure that these circuits work and make resonance, but I don't have CRO device. Is there any way to detect the resonance using Multimeter or something like that ?

I tried to hear the resonance. Human ear can hear 20 to 20K Hz, so I used 100uF coil and 1 uF capacitor to make Resonance of 15KHz frequency. ( 12 volt / 50 Hz AC power source ).
when I connect the 8-ohm speaker, I didn't hear sound. actually, it was a very low sound. It looks like the sound that I hear when I connect the speaker to the power source directly.


texts: Solar panel - blocking diode - DC to DC converter

texts:
I have a solar panel that outputs 21V. My idea is to connect it to dc-dc converter and TP4056 to charge Lipo battery.

Just like on this schematic but  first the DC-DC so that it can step down to 5V and then to TP4056 and then to the rest devices like ESP8266/Raspberry Pi.
What I wonder is that normally you need a blocking diode that you can see on the schematic to block the current flow back from the batteries and thus discharging them (e.g. at night). But having the DC-DC converter first do I  still need a blocking diode or the DC-DC will already stop the back-current flow?


texts: A question on eliminating ringing on a pulse

texts:
Above is a circuit with L C R components to model ringing.

As you see a 1V 50Hz pulse is applied to the circuit.
The ringing can be seen at the output pulse in blue color which has the resonance frequency of the parallel LC.

Even though the input signal is 50Hz, since it is a pulse(composed of harmonic sines) it generates ringing at the 5kHz component of the pulse(resonance freq. component).

My question is: Is there a remedy for this ringing at the output without affecting the pulse widths?

Edit:

I added a series LC with the same resonance freq. in series with R as seen below:

If I take the output from terminal of R1 the output (Out1 on circuit) is with a large spike(please left-click to enlarge):

But if I take the output from the terminal of C2 the output (Out2 on circuit) is clean and with no ringing; with large rising and falling edges but this could be fixed with a comparator I guess.
Here is Out2 on circuit:

edit2:

Here is the output from Andy aka's suggestion which completely removed ringing by keeping the pulses sharp:


texts: Noise on Proximity switch signal on PLC system

texts:
I am working on a PLC based system that uses High Speed counter cards to pick up a signal from a 24 VDC proximity switch.  I am having a problem with short duration 10 to 15 volt spikes being seen on the counter card as a false proximity switch hit.  I can see these spikes on an oscilloscope.

I rewired as many of these signals in shielded cable as possible but these errant spikes persist.

The proximity switches I am using are PNP and rated to pass 200 ma.  I am considering using a bleed resistor from the proximity switch signal to common to minimize these false spikes.

Any recommendations on how many milliamps/ resistor value I should be using?  I have tried a 20K resistor to bleed about 1 ma to ground when the signal is in the low state but I don't know if I should be trying to bleed more current to common?


texts: Lets say I would like to measure a 12 V battery with an ADC that has a lot lower reference voltage, like 3 V. For this battery, I don't need the full range, but only 10 - 12 V (so the ADC value 0 could be 10 V). If I use a simple voltage divider, I will measure the whole voltage range, also bellow 10 V. Is there an Op Amp configuration circuit that could be used to obtain this functionality?


texts:
I've been learning SPICE over the past few days, using the LTSPICE program. One thing that just escapes me, is how exactly do we know when a component's absolute maximum ratings have been exceeded? For example, the diodes have a maximum current flow, however, no matter what I set it to, it always simply works. Even when the design is blatantly violating the ratings.

This brings 2 questions:

Is there any way to enable something that lets you know when some component's maximum ratings have been exceeded?
If this doesn't exist, what is the purpose of inputting the maximum ratings into the component's model?


texts: Using multiple transistor to increase current handling

texts:
I need to make circuit that will convert 24v to 5v 4A.
I have bought LM7805 mosfets and they are converting 0-40v to 5v 1.5A.
Problem is that I need minimal of 4A at the end so connecting 4 transistor in paralel should give me 6A on the output (6 * 1.5A)? I tried this and it does not work.


texts: Gyro-based mechanical stabilization in robotics

texts: I'm from a computer engineering background and have a good knowledge about programming microcontrollers. I want to create a small plastic plane that is always kept parallel to ground regardless of the motion I apply to it. I can imagine that I would need a gyroscope to detect the applied movement, but the question is, Is there a programmable device that I can directly use for this? Also do I need motors for that sake? It will be great if you can give me a better design than the one I'm imagining


texts: Max Current through Neutral in wye-wye 3phase circuit

texts:
Assume that you have a wye-wye 3 phase circuit.  Each of the 3 phase wires can take a max of X Amps.  What is the max current the neutral of the circuit could have?

Is it possible for the neutral current to be greater than X?


texts:
I use a Sallen-Key filter for a project at university and I need to know its input impedance. Is there a way to compute it theoretically ?

Here is my circuit:


texts:
I need a simple, single directionnal level shifter for 3.3V -> 5V conversion.

There are many options on the internet, some using a logic ic and some using 2 NPN transistors (converter and inverter), but I never found an option using only a single transistor (and 2 resistors).

My understanding is that when input is at 3.3V, the transistor is blocking and R2 pulls output up ; while when input is 0V the transistor is passing and pulls output down to transistor VCE(sat).

So, why wouldn't such a converter work? There must be a reason...


texts:
I'm writing a document that should explain about a mini-PC in my company in order to give information for EMC test engineers who don't know the product.
The mini-PC introduces high granularity modular design and parametric enclosure.
This is the product specification file.
I'm intending to make a one page brief overview of the product that could be useful before performing the EMC test and get authorized for FCC mark.
I was wondering what are the product-related parameters, specifications, description that should be in the document in order to give a previous knowledge for the EMC engineers before performing the test.
Here are some aspects that I thought of:

Power
Extensions for mini-PC
different enclosures for the SBC (including dimensions, Height, cooling ribs)
PCB Specs (number of Layers, diff traces impedance, single traces impedance)

What do you think about these aspects, and can you suggest me more ideas?


texts: Zero crossing detector output to another optocoupler

texts:
I will use the configuration below to build a zero crossing detector to connect to a PLC.
I will change the output voltage to 24VDC and the correspondig resistor to 50K.
The problem is that the input port in the PLC contains a PC817 optoisolator and I am not sure if the optoisolator will repeat the input signal.
Have you ever done this configuration connecting the output signal to an optoisolator? Will it work? If I put a LED as test light will it flash? How many optoisolators can be concatenated?


texts: What could be the cause of high leakage inductance on my custom flyback transformer?

texts:
I've built a flyback transformer by hand for a circuit I am making and after shorting the secondary I have found my leakage inductance is very high. The primary inductance is around 2 mH, while the leakage inductance is at 1.3 mH and it is supposed to be at max only 60 uH. I have made the transformer twice now with the same result and I can't figure out what is going on.
Primary turns: 143
Secondary turns: 6 trifilar
As requested I am providing more detail. My primary inductance is calculated by:
$$ Lp = Vin^20.5*Duty*eff/(Po*fs)  $$
Vin = 135V, Duty=0.636, eff=0.72, Po = 10W, fs =137kHz
I need to have a target primary inductanced around 1900-2000 uH, and so I need to used a gapped core. The transformer construction given by PI designer is. Note there are 3 layers of tape between primary and secondary.
.
My Primary winding looks like this:

Shorted secondary to measure leakage:

Picture of core inside bobbin, there is a slight gap at the top which could potentially contribute:

The core material I am using is N27, core is gapped 0.17MM (recommended core gap from PI is 1.2 mm. Here is the data sheet The measurement was made on Proster 3M4070 LCR meter, accuracy should be off by roughly +/- 5 uH. The wires used for the core were not triple insulated, they are some wires I got off Amazon from BNTechGO


texts: 555 Timer works perfectly until solenoid connected to relay then continuously triggers

texts:
Note: the solenoid text in the image is just a representation.
Real world everything is fine until I connect the solenoid to the Com and N/O of the relay. It then cycles once and starts to continuously re-trigger on it's own once a second or so. I disconnect the solenoid and it works as it should.
I have used the common 12V as in the image and I have also given the solenoid it's own separate 12V but it makes no difference.


texts:
My question is not about a particular bus or line and the termination I should put on it.

I know some busses need termination resistors like CAN or address/data for memories.

If I understood well these resistor are needed to avoid reflection on the signal.

My questions are :

Are termination resistors needed only to avoid reflection?
What is the electrical phenomenon that lead to reflection? Why is there
reflection on a signal if there is no resistor?
Is the value of the resistor depending on the bus length or more on
the frequency of the bus?
If resistors are for reflection purposes what is the phenomenon that
destroy the reflection by adding a resistor?
Why are termination resistors needed sometimes in parallel and other
times in series?


texts: How does one relate an RC circuit's time domain solution to phasors?

texts:
It seems to be a given for phasor analysis that the voltage across a capacitor can be defined as follows:

$$ V_{C}(t) = V_{A}\cos(\omega t + \phi)\tag{1} $$

Where Vc(t) is the capacitor's voltage at time t, Va is the amplitude of the voltage supply's sinusoid, ω is the angular frequency of the signal, and ϕ is the phase offset.

From there, you can go on to define the voltage as a phasor, for use in steady-state analysis. Unfortunately, I'm having trouble proving to myself that this sinusodial behaviour can be assumed of a capacitor's voltage.

I know that, for a fixed source, the voltage across the capacitor becomes the same voltage as the supply. In the case of a sinusoidal supply, however, it would seem possible to me that the supply would change faster than the voltage across the capacitor could, causing, at the very least, the voltage across the capacitor to have a different amplitude to the source voltage.

I tried to find the mathematical solution for this circuit by equating the current through the resistor to the current "through" the capacitor:

$$ \frac{V_{A}\cos(\omega t + \phi) - V(t)}{R} = C\frac{\textrm{d}V(t)}{\textrm{d}t} $$

Plugging this into Wolfram Alpha yields the following:

$$ V(t) = c_{1}\exp\left(-\frac{t}{RC}\right) + \frac{A}{(RC\omega)^{2} + 1}\Bigl[RC\omega\sin(\omega t + \phi) + \cos(\omega t + \phi)\Bigr] $$

Which seems to imply a non-source amplitude, as well as the composition of two sinusoidal functions rather than one. Is the calculation I've tried to perform correct? If so, how would one relate this solution to (1)?


texts: How safety capacitor replaces optocoupler

texts: I see some phone chargers using safety capacitor (after some research I found its safety capacitor)But not optocoupler to isolate in and out . How safety capacitors replace the optocoupler


texts:
I try to make my own USB cable for my iPod but I found a PCB in the picture on 5 volt USB The sot23-6 on PCB doesn't have any text, Any idea what it is?
When I don't plug in a device OUTPUT is 3v but if I plug in a device OUTPUT is jumping to 5v


texts: problem assigning a zero-length array port in vhdl

texts:
I have a vhdl component with a custom type defined for a port. The type is an array of a composite record type. The array size is adjustable via generic and according to the person who designed the component, I can set it anywhere from zero to eight. I would like to set the size to zero to disable it but I'm having trouble getting it to synthesize because I cannot find an acceptable way to assign the input ports.

So how do I assign a zero-length input vector on a component instantiation?

Below are some code snippets of what I have to aid with understanding my question.

Type declarations:

type axi_out_type is record
    aready : std_logic;
end record axi_out_type;

type axi_out_vector is array (natural range <>) of axi_out_type;

type axi_in_type is record
    wid    : std_logic_vector(3 downto 0);
    wdata  : std_logic_vector(1023 downto 0);
    wstrb  : std_logic_vector(127 downto 0);
    wlast  : std_logic;
    wvalid : std_logic;
end record axi_in_type;

type axi_in_vector is array (natural range <>) of axi_in_type;

Component declaration:

component my_component is
generic(
    ...
    NB_AXI_SLV: in integer range 0 to 8 := 1;
    ...
);
port(
    ...
    axi_in_ports: in axi_in_vector(NB_AXI_SLV-1 downto 0);
    axi_out_ports: out axi_out_vector(NB_AXI_SLV-1 downto 0);
    ...
);

signal my_axi_in : axi_in_type;

Component instantiation:

comp: my_component
generic map(
    ...
    NB_AXI_SLV => 0,
    ...
)
port map(
    ...
    axi_in_ports => (others => my_axi_in),  --What do I assign here?!?!
    axi_out_ports => open,
    ...
)

my_axi_in <= (wid=>(others => '0'),wdata=>(others => '0'),
                wstrb=>(others => '0'),wlast=>'0',wvalid=>'0');


texts: How is NAND Flash memory array organized?

texts: Could you please explain how memory array organization calculated? Here I have attached snapshot of 2Gb NAND flash memory array organization. I can't understand the calculation of 1 Plane (marked in yellow color), but I do understand the calculation of 1 block.


texts: Sharing the load between resistors, parallel or series?

texts:
If in a circuit a resistor with given value of R should be of W watt, is it OK to replace it with following cases:

2 \$R/2\$ of \$W/2\$ in series.

2 \$R\cdot2\$ of \$W/2\$ in parallel.

In other words, can we increase heat dissipation by putting resistors in series or parallel? what are the pros and cons if any?


texts: Can I power multiple Constant Current LED fixtures with a Single Constant Voltage Driver?

texts:
I would like to repurpose eight, 8' LED strip lights that were previously individually powered by 1600ma constant current drivers. Is it possibble to power these LED fixtures with a more readily available Constant Voltage driver? I only have one of the previously used drivers (dimmable) which had an output voltage between 10 and 55 so my plan would be to dial down a 60 V power supply to 55 V. As far as limiting the current, my plan would be to put enough fixtures parallel to the power supply that it couldn't exceed the 1600ma per fixture rating. For example if I was to use a 600W power supply my logic is this:
600w / 55v = 10.91A / 7 = 1558ma per fixture at 55V
Is this logic at all correct or will I just smoke the LED's attempting this?
Thanks.


texts:
I need to flip/mirror the full PCB along the Y axis. Is there any option to do that in Altium Designer?

I only find info about how to mirror a single component but no the full PCB


texts:
I just had (and solved thanks SE) a problem with a wall socket where the ground contacts were malfunctional. Much of the electrical safety relies on proper grounding. As far as I can read, details for state-of-the-art measurement of grounding is a science for itself, but the described methods seem far from impossible to do.

I want to test grounding of each socket (and possibly measure resistance for monitoring) as far as possible and practical for safety reasons (personal protection, possibly reduce noise (especially bad with telephone at my parents' house), and obvious prerequisite for surge protection).

Question: What are practical, safe and economic ways for a technically skilled person, but not regularly trained as electrician? E.g. 3 or 4 wire measurements with earthing, "measuring probe" and "helping-earth probe"? In particular, I am not specifically interested in one earthing metal pole but in the earthing as such that "arrives" at the sockets.

I live in an area with houses and small gardens, but with low distance to other houses/streets (5-50 m distance in all directions). So far, I could not figure out in what way my apartment house is (or: should be) grounded (no answer from landlord, I think they do not know themselves). Is it then necessary to disconect the earthing pole from the rest of the house as I read somewhere? (Seems that this was primarily meant only to test one specific earth pole independent from possibly other earthing poles)

I am willing to spend some money, but not necessarily hundreds of dollars/euros per household. I see devices (from cheap (24 €) to expensive (174 €), all still affordable) such as this, this, this and this. Price would be ok as I can use it for my family and friends as well, this is why I'd prefer DIY (if considered safe). Do such devices offer a valid approach to my question?

Disclaimer: All electrical engineering of the house was done by certified electricians (at least I hope so), and I do not want to change anything - unless I discover a problem and will then obviously ask a certified electrician to solve it if it requires work on the mains.


texts:
I am new to the CAN. I have came across bit stuffing which is used to ensure that all receivers nodes are synchronized to transmitter node (After 5 bits of the same polarity, CAN will add a bit stuffing bit of the opposite polarity).

I have some doubts regarding bit stuffing in CAN:

  Bit stuffing in not applied to Identifier field in CAN protocol.

Is this statement correct?

  All bits after Identifier field will be bit stuffed if applicable

Is this statement also correct?


texts: What is the real ADC Sample rate for Xmega256A3BU or similar xmega controllers

texts:
Based on the datasheet of XMEGA controllers, it has sample rate up to 2Msps (2MHz sampling speed).

But it is also written that the conversion time for 12-bit need 3.5µs which gives ca. 300 KHz real sampling rate.

I really want to know what is the real sampling rate for XMEGA controllers.


texts: How does the DAC function within this circuit? How does the transceiver work in this case?

texts:
I have this circuit which I have to study but I don't know  how the DAC circuit works when  combined with the other components.  I  understand the functioning of the DAC but not that of the other components.
What is the function of P5 component, what does it do?


texts: How to modify this tank circuit to obtain a 3rd order passive band pass filter?

texts:
I am very confused about band pass- and band rejectfilters. I have this circuit which represents a bandpass filter. A 2nd order (2 energy exchanging elements) bandpass filter if I am not mistaking:

But to obtain a 3rd order BPF, should I add a capacitor or coil in series or parallel? And why?


texts:
I run a small hobby-business that make DIY Electronics Kits. Business has picked up and I am wondering if there is some kind of machine that will do part counting.

The parts types I count by hand are : Jumpers(Thousands of 10-20 sets) , Pin headers , spacers & screws, screw connectors and a bunch more.

How does large Electronics companies deal with this and are there options for smaller start-up's?


texts: Finding roots of undamped and damped time domain response of a 4th order characteristic equation

texts:
A fourth order system is expressed in terms of the characteristic equation as
\$s^4 + 8s^3 + 24s^2 + 32s + k = 0\$
Using the Routh’s array criterion determines the value of the gain parameter k and the corresponding
roots for the following two cases:
(i) System time-domain response is undamped oscillations.
(ii) System time-domain response comprises of damped oscillations.
I was able to find the stability range of parameter k as \$0<k<80\$, but I'm struggling to understand how to find the roots when system gives undamped and damped oscillations.


texts: Amount of Decoupling Capacitance in Integrated Circuit Layouts

texts:
When doing integrated circuit layouts, how does one pick the amount and value of the decoupling capacitance ?

When doing over 10GHz designs, I typically EM simulate the supply line and use the resulting RLC value to determine the decoupling capacitance.  I look at the lower frequency response around DC and look for ringing especially if I use MIM caps which are higher Q versus MOS capacitors.  If I have ringing in my response what do I do?  Do I de-Q the capacitance of the MIM capacitors using resistors?  Or just use MOS capacitors?

When doing lower frequency RF or analog IC designs, I would just let the RC extraction help me with the supply lines and so on and then determine the capacitance that way.

Is this thinking/methodology/flow correct for these different frequency designs?  How best to determine the amount of decoupling capacitance on chip?


texts:
I'm redesigning a logic circuit. Previously the circuit had a decoder with 4 inputs which made sense because it used like 12 of its outputs. However changing the circuit for what I have now I only use 4 of its outputs. Now I was wondering on how can I get rid of the decoder because I don't feel that it makes that much sense to have this huge decoder and only using like 4 of it's entries.

I attempted to change to a small decoder or a multiplexer but I don't that's the way. Because for example I use the input 0000 but I don't use the input 1000. If I used a multiplexed that had 2 entries (the 2 less significant bits of my original input) it would select the signal I want for 0000 with 1000 and 0100 and 1100... And I don't want that to happen...

Can someone give a tip or a hint on how to proceed? Thanks!

EDIT:
I deleted my comment because I find out I was providing wrong information about the codes I'm using

The codes I need are 0001, 0010, 0011 and 0100. So the 4th bit is not used...


texts: Non-zero output from a LM741 in a differential configuration

texts:
I'm trying to amplify a DC voltage coming from a strain cell (with a built in Wheatstone bridge). The voltage swings from -1mV to about 4mV depending on the strain. I've set up a differential amplifier using a LM741 as the one depicted here:

The chip's Vcc- and Vcc+ pins are connected to 0 and 5v, respectively. The input resistors are 100 ohm and the resistors Rf and Rg are 120k. When I turn the power on without anything connected to the inputs, there is approximately one volt between the output and the zero. When I short out the inputs to ensure that no voltage is present, the voltage drops very slightly (a dozen mV) but is still present.

What could be causing the trouble? Is the gain set up too high? Is that the bias that I have to null using the "OFFSET" pins on the 741?


texts: Do AC current sources exist and why or why not? For both actual and theoretical

texts:
I got confused when I encountered this problem on Chegg.
https://www.chegg.com/homework-help/questions-and-answers/5-find-ac-current-source-iin-polar-form-b-find-vt--c-choose-one-source-current-leads-sourc-q19121964
Question:
5.
a) Find the AC current source, Iin in polar form.
b) Find VT .
c) Choose one:
i) The source current leads the source voltage.
ii) The source current lags the source voltage.

My question isn't about solving the problem. Do AC current sources exist? I've tried searching and they don't pop up except for the Chegg problem I saw. I also recently took a Circuits class and three basic active components discussed to us are the DC voltage source, AC voltage source and DC current source. I don't get if they exist at all, and if so why is information about it not as common?
EDIT: People might answer only about the actual AC current source. I am also talking about theoretical. Like can I do the same thing in Chegg where you put a wave symbol and an arrow and call it a theoretical AC current source? How would you then use it in computations? Do you just attach a phasor to it and use current in the x-axis instead of voltage for vector diagrams?
It's because I'm curious on both. Yes I want to know whether they exist in real life but I also want to know their "existence" on our theoretical computations. Are they there but scarcely used? Or do they not exist at all on common electrical circuit related courses?


texts: How much energy can a RF harvester capture from a mobile phone

texts:
Hi Guys,

I've wondered if mobile phones were able to transmit energy to RF harvesters. Is there a way to calculate how much energy can be harvested from a standard smart phone today when placed at a distance of 1 inch for X period of time (eg: 5 seconds).

This can be used to power future applications with RF / NFC without the need for batteries.

See link for reference. http://www.creative-science.org.uk/mobile_LED.html

Thank you.


texts: I have been working on a hi-fi audio amplifier, and I plan to put it in a metal enclosure when it is finished. The amplifier is (relatively) low power, so I'm powering the system from a wall-wart power supply. Many of the connectors on the board (headphone jack, RCA auxiliary outputs, power input) have their shield/chassis connected to ground, which means unless I use a grommet or something similar, the chassis would be electrically connected to ground (the chassis would never be intentionally used as a ground conductor, however). Could this cause any issues? Note that I have seen this question asking about a similar topic, but I wasn't sure if the answer could differ for a system that is sensitive to low levels of noise.


texts: How can I trigger a photography strobe from a iPhone LED flash?

texts: I would like to trigger a photography/studio strobe flash based on the flash of an iPhone camera's LED flash. I'm picturing a device that I could attach to the back of the iPhone temporarily when I want the system to work. I would like it to respond in less than 500ms.


texts: How do I calculate the discharge time of a battery with a step-down converter?

texts:
I'm building a battery to drive a small 12V motor which is rated to draw max 7A.
The battery has the following stats:

Nominal voltage: 14.4V
Capacity: 20.4Ah

So I calculated that the energy should be 293.76Wh.
So I understood the discharge time should be calcuated as:
Energy/(Voltage * Current)

Since the motor is rated for max 15V, which is below the 16.8V max of the battery, I will use a buck converter to bring the voltage down to 12V.
So my question is, would the calculation then be:
293.76Wh / (12V * 7A)

Or, do I use the nominal voltage of the battery in the calculation?, i.e.
293.76Wh / (14.4V * 7A)


texts: Light Detector/Identifier circuit using photodiodes

texts:
I'm currently completing my final year project and am currently stuck going round in circles as how to complete it.

To summarise: I need to design a circuit which is capable of IDENTIFYING a light source (primarily biomass flame light) from other light sources using photodiodes.

My circuit will (hopefully) be in 3 parts. Part 1 - photodiode sensor circuit; part 2 - microchip to analyse part 1 and prepare results; part 3 - output results on display. Part 1 is causing me my problems as no one has done anything like this before from my research into this.

I have made a very simple Transimpedance Amplifier using a photodiode in photovoltaic mode feeding into an Op-Amp - basically a current-to-voltage converter. Howvever through exhaustive testing I have found that the circuit responds to any and all light and does not allow me to distinguish as to what the light source is therefore I stopped with this circuit.

My next port of call was to use the chip "TCS3200" as a standalone chip which has filters in front of the photodiodes. Connecting S0/S1/OE to 5V and monitor Pin6, I would measure light levels using the filters (Red, Green, Blue and Clear/No filter) to allow me to make an educated guess as to what the light source is based on the readings. I have yet to do this but will update this as soon as I have.

However my question is - is there ANY way that this could be done using photodiodes? Being able to not only detect light but more importantly to IDENTIFY it as well. Is there a way to do this? Have I overlooked something or am I missing something? Any help would be appreciated. Thanks.


texts: LED accent light that slowly dims when removed from power source

texts:
We've all played with different transformers and power supplies that have an LED indicator that dims before going out entirely when the power supply is unplugged.

I'm working on designing an accent light which would involve a translucent crystal light source (probably made of resin or glass if I can find a cheap supplier) containing LEDs and certain electronics, and a base which would supply electrical current. For gamers, it might appear somewhat like a Welkynd Stone. My question is what is the simplest way to cause the LEDs to dim slowly (say over 2-10 seconds) when the crystal is removed from the base? Similar to the unplugged transformer, but with an intentional and controlled dimming.

I just purchased some LEDs and plan to build a test system over the next month or two. These LEDs are in a 5 meter strip divided into 3 LED series run in parallel and rated at 12v. I do not know the amp rating of the LEDs, but I'm guessing in the 20ma range (what I've read is average for bright white). I will probably use 4 series totaling 12 LEDs in the test build. LED strip link

If I have the transformer from AC power built into the base, I was guessing I could use a number of capacitors in parallel with a resistor to store electricity and slowly discharge it into the LEDs. But I'm a self-taught enthusiast so I honestly don't know if this would actually work. Nor do I know the number and ratings of capacitors and resitor that I would need.

If I have the transformer built into the crystal, the transformer and rectifier would retain a small amount of electricity, but I don't think it would be nearly enough to provide the effect I'm looking for, so something else would have to be added to make it last for several seconds.

A nicad battery with control electronics is literally my last resort for achieving this effect, and I'll probably give up on the idea before I go programming my own circuit board.

That's my main question. If anyone wants to toss in some thoughts on how to connect the crystal to the base, I'm open to suggestions. My original plan was to simply have a direct copper to copper connection with the base. But I've recently been considering an EM charging system (akin to a powermat or these wireless rechargable flashlights my dad has). The concern with the wireless is providing consistent power to the LEDs, though it is safer. I've also learned quite a bit already about constructing the power supply from perusing this SE site, but if anyone has any suggestions for that, too, I'm all ears. For the test build I'll probably hook it up to a computer power supply, or a laptop power supply if I can find a 12v one at Goodwill or the local electronics parts store.

If I get the test model to work, I plan on building possibly a dozen of these for accent lighting around my home.


texts: Multiplication of 2 waves in a phase detector of a phase-locked loop

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What would be the product of a 60Hz square wave and a 60Hz sine wave with an approximate phase shift of -45 degrees?

I could not find a proper solution to this anywhere.


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Why is power consumption sometimes given in mA and not in units of Watts? For example, consider the following statement:

"A USB device specifies its power consumption expressed in 2mA units in the configuration descriptor."

I have seen this in some datasheets too and initially thought them to be typos.


texts: Blinking an arbitrary number of LEDs in succession

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I've recently come across a problem that I feel should be nearly trivial, but for the life of me I can't figure out how it would be done. Basically all I want is a series of LEDs that will light up like dominoes. Essentially just looking for some way of triggering the next LED really.

This would be a pretty trivial problem with an Arduino and a relatively small number of LEDs (as many LEDs as pins), but I'm really looking for a way to put together a few dozen of these. I would prefer a solution that works without a microcontroller, but if I can use one microcontroller for a semi-arbitrary number of LEDs I would be more than happy.


texts: Need a precision single supply log amplifier (voltage to current)

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In the synthesizer world there is a standard called "1V/octave" which basically refers to a linear input voltage corresponding to a logarithmic change in frequency (e.g. 1V = 100Hz, 2V = 200Hz, 3V = 400Hz, 4V = 800Hz and so on).

All the schematics that I can find are made for symmetric power supply and they only work with positive voltages. Now when I convert those schematics to my single supply environment I can only use voltages between 4.5V and 9.0V (I run on a +9VDC power supply). I have spent days modifying these circuits to my need but I don't have any luck.

Here's one of the many circuits provided by the internet: