texts: Differential encoder output of PSK modulation input

texts:
I am a bit confused to the answer given for the following question.

The question reads as follows:

If the input to a binary differential PSK modulation system is 01100101000111 tabulate The differential coder output

I know that for the differential coder output:
0 is encoded by the same pulse used to encode the previous data bit and 1 is encoded by the negative(opposite) of the pulse used to encode the previous data bit.

I am confused because Online and what I calculated does not match the answer that my professor gave.

My answer: For 01100101000111 input --> the output 001000110000101

Professors answer:
--> 1 -1 -1 -1 1 -1 -1 1 1 -1 1 -1 -1 -1 -1

I found that this is only true if I first invert the input then apply the method, (in other words For 01100101000111 input becomes 10011010111000 )

Im so confused now, because I do not think that is how he obtained his final answer.


texts:
For a signal with amplitude,

$$V = A\sin (\omega t)$$

any idea at what point the maximum slope (gradient, dv/dt)  is? I have gone through the method of differentiating which yields

$$A\omega \cos(\omega t) \tag{i}$$

and then doing a second differential, which yields

$$-A \omega^2 \sin (\omega t) \tag{ii}$$

Equating (i) to 0 and then substituting back into (ii) to find which point is where I got stuck. I can do this with a normal equation but trigonometry sometimes confuses me. Any help will be appreciated.


texts: Reuse a microphone (formerly) wired to the digital "General Purpose Input/Output" of a Realtek sound card?

texts:
I recently repurposed an old laptop screen (from a Dell XPS L502x) as external monitor, and then made the built-in webcam work without too much fuss.
The camera module also has an embedded microphone, and I'd like to see if I can make that work as well.
I was naively expecting an analogue signal all the way to the sound card. However, the two wires for the microphone seem to be carrying a digital signal, one being DMIC-CLK1/2 and the other GPIO0 / DMIC-1/2. They were connected to pins 46 and 2 respectively on a Realtek ALC665.
I tried figuring out whether there was any recognizable standard for this microphone's signal, but I couldn't make much sense of the docs.
So what is the communication format/standard/protocol of this microphone? Can I turn this microphone into something usable? Convert the signal back to analogue, maybe? Or will it work out of the box if I just make it a jack cable and connect it to my mic in? Would this work with another Realtek "HD Audio Codec" card only?

Here is a picture of the full webcam module:

The back displays the name of the module, "HannStar J QCM20Q-1" but no luck finding documentation online, only offers for used parts.
From left to right the main structures on the front side are:

a big coil, L3
a small chip, U2, with "ETF" and some dots written on it
a  partly peeled-off sticker with some product numbers
the orifice of the microphone
some metal cover I can't remove
the webcam lense
the connector (7 wires, with two mass) above some test points
a chip with "cFeon F10-100GIP" written on it, apparently this is a memory chip.

Back and front have same top/bottom and opposite left/right, so the microphone is where "PAD L1" is on the back.

Side notes and references, in case it's useful:
My current hardware is a Realtek ALC889 sound card, in a Supermicro X9SCV-Q motherboard that seems to only have two front panel jacks for all audio connectors.I haven't been able to find schematics for this motherboard.

Datasheet of the Realtek ALC665
Dell service manual for the XPS l502x
Schematics for the Dell XPS l502x (audio on page 38, webcam wiring on page 24)
User manual for the Supermicro X9SCV-Q


texts: STM32F103 - CubeMx - MCU reboots with FreeRtos v9

texts:
I using a STM32F103 in my project and I generate the Keil project with Cube32MX with this firmware package for STM32F1 version 1.4.0.

Today I update the Cube to version 4.23.0 and I migrate my project (including the update to the firmware package v 1.6.0.

There is no problem during the program compile, unless some Watchdog defines. I use FreeRtos v. 9 but previously ( when everything works I use v. 8)

When I run the program in debug mode the peripheral initialisation (main.c) works, but when the my task starts the program restart and execute again the peripheral initialisation into the main.c file.

#if ( ( configUSE_PREEMPTION == 1 ) && ( configIDLE_SHOULD_YIELD == 1 ) )
{
   /* When using preemption tasks of equal priority will be
   timesliced. If a task that is sharing the idle priority is ready
   to run then the idle task should yield before the end of the
   timeslice.
   A critical region is not required here as we are just reading from
   the list, and an occasional incorrect value will not matter. If
   the ready list at the idle priority contains more than one task
   then a task other than the idle task is ready to execute. */
   if( listCURRENT_LIST_LENGTH( &( pxReadyTasksLists[ tskIDLE_PRIORITY ] ) ) > ( UBaseType_t ) 1 )
   {
     taskYIELD();
   }
   else
   {
     mtCOVERAGE_TEST_MARKER();
   }
}

I try to disable the FreeRtos preemption, I tried to change the system timer but nothing has changed.

Should I modify some FreeRtos configuration parameters into Cube32Mx?

Thanks for the help!


texts: ICs with humidity or moisture sensitivity - bake recommendations

texts:
I purchased some ICs recently that included something I'd not seen before - a moisture 'sensor' on a paper strip with color indicators for a few specific levels of humidity.  Once the paper reaches a given moisture level, the color on the paper changes color.  If that level is reached, it recommends baking the IC.

This prompts two questions I've not yet found answers to:

1.)  I've rarely, if ever, had problems with static/ESD breaking ICs.  Chip manufacturers are rightfully very cautious about ESD when shipping their products.  Here on ee.stack I've seen discussions regarding ESD with most answers approaching, "don't worry about it that much."  Is this a similar scenario - where I could just blow off the warnings and still have a working IC without baking the IC after reaching that recommended moisture level?

2.)  Assuming I do need to worry about it - After I've built my product, do I still need to be concerned about the impacts of these small amounts of humidity on the IC?  In other words - do I need to use a moisture-resistant housing in my product's case to manage humidity (this is something that could be used in multiple climates.)

Thanks in advance.


texts: Building a compact and bright 940 nm IR light source?

texts:
I'm working on a small personal Airsoft related project and have been looking at ways I can make a bright 940 nm light source.
Hoping to be able to illuminate 20 m or greater area so that I can see clearly in the dark with use of an Raspberry Pi NoIR Camera v2, showing similar results as a night vision camera or night vision rifle scope.

I've seen there are several illumination options such as LED, Bulb and Chip.
 - What type of Infrared light source from the above would be the best choice for a bright, long range, compact and low power solution?
 - What makes Infrared lights brighter / duller?
 - are there other sources of Infrared light sources I haven't stated above that could be effective for the project?
- Are there any dangers using 940 nm light sources?


texts: Recommendation for series protection resistors on CAN bus?

texts:
When implementing an RS-485 interface, I tend to follow TI's recommendation in the SN65HVD75 datasheet to include \$10 \Omega\$ series resistors on the A and B lines.  The TVS diodes I'm using clamp at 15 V maximum, and the transceiver can handle up to 16.5 V, but I prefer some design margin.  The comms are enclosed in a large, metal enclosure, and do not interface outside of it.

As a carry-over, I have been including series resistors on CAN bus interfaces, right at the driver/receiver pins.  This bus also resides in the enclosure and does not interface outside of it.  The TVS diodes clamp at 8 V maximum and the transceiver I'm using can tolerate up to 16 V on the H/L lines.

Given this much higher margin it would seem that series resistors are unnecessary, but I am still hesitant to remove them from the design.  Being only \$10 \Omega\$, they won't drop too much voltage (~250 mV of 3.3 V; high/low input thresholds are 2 V, 0.8 V, respectively).  Yet, out of four sample CAN transceivers from different manufacturers none of them recommend series protection resistors, either.  Should I just leave them down or is there a strong reason to remove them?

EDIT: The CAN bus also interfaces with a user interface board, which drives an LCD screen on the outside of the enclosure.


texts:
From the following diagrams:

Are the current directions correct? Based on where the terminals are connected on both conductors?


texts: Capacitor microphone PSU - design question

texts:
I'm restoring a capacitor microphone PSU. Schematic is as follows

I have an EE question about the existing circuit. [Whatever the answer, I'm going to replace the upper 4-5V heater supply with a 7805 (and the lower part with a TL783 jacked up to 120V output), i.e. this is not a repair question.]

It is arranged via the current-sense resistor, the 9V1 zener, and the OC26 (germanium) pass-transistor as a constant-current source. Considering there is a valve in the microphone and considering the low signal levels prevailing, it surprises me that it isn't a constant-voltage source. Would that be for example because of techology limitations at the time (1964)? say even just crude parts count? Or is there a technical reason concerning valve heaters that I'm not aware of?

The schematic is quite interesting. Note the huge and bootstrapped 180M grid resistor on the valve, to match the high-impedance output of the microphone capsule (only a few pF I believe).

For reference this is a Phillips EL 6154/01, aka AKG N60A.


texts: High vs Low audio transistor hFE (DC Current Gain). Which is better?

texts:
I'd like to preface by saying Rest in Peace my SoundBlasterX's back-panel transistors.
What I tried to do, shown in the images below was ground the copper heatsinks I had glued onto the metal side of the back-panel transistors (using ArcticSilver thermoconductive epoxy) to the chassis common ground. Unfortunately I think I overcooked them as barely any sound comes out of the Headphone or Line-Out plugs at the back of my AE-5 sound card anymore.

After a 10h crash-course with sensei Google on advanced transistor types, I have concluded that these are kind-of trash-tier and a very old design, but still very wide-spread in use.

https://www.st.com/resource/en/datasheet/cd00001225.pdf

No mention of operating frequency bandwidth to be found but similar models go up to 190MHz... which is totally overkill for audio application, since if we divide that by their max hFE of 250, then we get a worst-case roll-off frequency of 760,000Hz
Like I said, total overkill for any audio application (and might capture some annoying background frequencies inside the PC case)

Now, because I'm not the sort of person that's just happy with stock components (or happy in general really) I decided to put in the extra elbow-grease and find some higher-powered replacements to feed my new power-hungry Fostex T50RP MK3 headphones (which can apparently swallow up to 3000mA of signal power, the thirsty little minx)

I had initially settled on the MJE2xx models below, which I'll admit are a bit overkill at 4A Collector current vs. the original 1.5A
https://www.el-component.com/bipolar-transistors/mje254

Though going by the electrical measurements on this card, I'm guessing these are set up in an Emitter-Base configuration and thus giving only 0.5A of total signal thoroughput. The basis of my assumption here being that nobody in their right mind would want to accidentally run 160v of combined voltage (these are set in a push-pull, NPN/PNP config) into any pair of headphones (except electrostatic ones I guess, but those need Thousands of volts so it wouldn't work either)

Then I finally stumbled across the solution... a single seller, the only one on AliExpress selling 20 pairs of 2SD882/2SB772 transistors for 1.78EUR/lot

After rushing to buy four of those lots with the specific aim in mind to match them when they arrive (yes, I'll go through all 160 of them, I'm THAT masochistic), the seller was kind enough to provide the following datasheets for them:
https://www.st.com/resource/en/datasheet/cd00001225.pdf
https://www.st.com/resource/en/datasheet/2sd882.pdf

What's this? Twice the amperage on both Collector and Base? For the same wattage?!
Yes please!

The frequency bandwidth of 100MHz is also a far cry from the paltry 2MHz of the MJE2xx units which some forum posters report having terrible sound quality (probably to do with their worst-case roll-off of only 11111Hz ...yes I also did the math on these ...then canceled my orders for them)

So why didn't I order these in the first place? Well...
https://www.el-component.com/bipolar-transistors/2sb772
According to el-component up there, there was a 10MHz difference between the NPN and PNP versions of this line. (90 vs 80) So that would have made matching a bit more tricky, but the last seller gave me the good news in the form of those Datasheets which clearly show the newer versions being both rated for up to 100MHz

Now for the actual question I have for you fine people.

Would choosing a couple of pairs with the lowest hFE be the best course of action here, or would choosing a higher hFE give better results?

As-usual I appreciate your valuable input and thank you in advance for your time and knowledge :)


texts: Why does a MOSFET's drain current decrease when increasing the transistor's width and length, however the overall W/L ratio stays the same?

texts: I am doing a simple NMOS simulation where my W/L ratio was set to 20. I then increased the width and length of the MOSFET, however the overall W/L ratio was still 20. One thing I noticed was the drain current decreased. Shouldn't the larger W and L increase the current?


texts:
I am designing an embedded system where I need to minimize power consumption in standby mode (ideally no additional consumption from the IR receiver circuit when in standby) This system will be running off of coin cell batteries, so its very important to minimize consumption.

Functionality - some microcontroller is connected to an IR receiver circuit. The microcontroller is in sleep mode normally, when the IR receiver is sent a signal (from an IR remote control) it will wake the microcontroller, decode the message, perform some task, and then return to sleep.

how should I configure the receiver circuit to eliminate power consumption when not receiving data?

Can I simply use a large resistor to limit the current to something like 1mA when receiving data? (this is to minimize power consumption both when in standby and when receiving data)

5v---10kResistor---/DataInPinOnMCU/---IRReceiverDiode---GND

or

5v---IRReceiverDiode---/DataInPinOnMCU/---10kResistor---GND

Will ambient light cause the IR receiver to complete the circuit and affect the power consumption?

when waking on interrupt, how can I ensure the microcontroller does not miss the beginning of the message?

Thanks in advance


texts: How to (.step) change bjt/fet/opamp models in simulations in LTSpice?

texts:
Is there a way to change bjt/jfet/opamp model in simulation in LTSpice (similarly to changing parameters with .step command)?

I would like to compare different bjt/jfet/opamp models, run a number of simulations with different models, then display the transient/fft curves in the same window, to compare their performance in a given circuit.


texts: How can one test that a signal is High-Z when simulating with Verilator?

texts:
Say I have this module:

module Test(
    input  logic a,
    output logic b
);

    assign output = a ? 1'bZ : 1'b1;

endmodule;

Currently, when testing the module with a C++ testbench, the output of the simulation shows the High-Z state as 0 (I assume because verilator models logic lines as integers).

Is there any capability to test whether a 0 is a numerical 0 or a High-Z?

Thanks!


texts: Gain not containg the output, non ideal, resistor

texts:
I was working a mathematical model of a non ideal op-amp circuit and I saw a slide in the following presentation:

The question I have is the following: Why does the close-loop gain \$\frac{\text{V}_\text{o}}{\text{V}_\text{i}}\$ not contain de resistor \$\text{R}_\text{o}\$?


texts: How to differentiate center-tapped power transformer from a non center-tapped one?

texts:
I'm a hobbyist and I have 2 doubts regarding a power supply described into this schematic:

1) How do I differentiate a center-tapped power transformer from a non center-tapped one? My primary language is portuguese and I cant manage to translate it... Can I assume that "24V 2A" is a center-tapped transformer and "24+24 2A" it's not?

I need a +-20V power supply. Into the diagram, it recommends a 30V center-tapped or a 15+15V secondary in order to build one. But:

2) If I split a 30V center-tapped transformer, it will give me +-15V, not 20... Neither if I use a 15+15V, it will not amplify to 20V...


texts: Power line communication, how to check if frequency is present

texts:
I'm trying to communicate on a power line without external filters (only a filter for the 50/60Hz), because I want to use only digital filters.
My processor is a Cortex-M3 device running at 24MHz.
My communication is very simple, if the frequency of the carrier is present this is a 1, if not, is a 0. Obviously I will use a start bit for sincronization.
The frequency of the carrier is 125kHz.
In simple words, I wanna recreate the TDA5051 ASK power-line modem, with software.
I think that there are 2 valid method for doing this:
- Filter the signal with a series of FIR or IIR filters and analize the resulted signal
- Making FFT without filters the signal and check if the portant is present.
What's the best method? There is a best way?


texts:
To use SPI over a 5m long cable we plan to use LVDS RS-644 which calls for a twisted-pair cable with 100ohm characteristic impedance.

Evaluating our cable options we looked into Cat5 cable (originally for ethernet but perfect for LVDS), but unfortunately we need at least 5 pairs: 4 pairs for SPI (reception, transmission, chip select and clock) plus two wires for symetric power whereas Cat4 provides only 4 pairs.

We seem to come across all kinds of high quality 100ohm cables with more than 4 twisted pairs but all seem to be specialty products. Ethernet cables (only 4 pairs) are available with ease but the rest are much more difficult to source.

Any suggestions on other cable standards that could facilitate sourcing them in short lengths but still be specified as 100ohm for high-speed data links?


texts:
I have a strange question for a crazy idea. I have no idea if I am right or wrong on this, but I want to ask it so I can understand.

I want to electrolyse water using the fewest amps possible. This is so that I can have greater efficiency while transferring and dealing with the power.

I know that electrolysis begins at around 6 to 12 volts. No problem there.

However, can I perform this at 700 volts or higher (admittedly separating the cathode and diode to prevent sparking) (or would it?) and use less amps?

I am wanting to lower resistance by reducing amps. This will allow smaller wires. And some other parts of this idea to possible work. I am just at the wall of my knowledge, and would like to start a new conversation to understand this.

Thanks.


texts: In Ethernet Magnetic part why we using chassis ground and separated choke primary side form common ground?


texts: DNP means to short or keep circuit line open

texts:
In the circuit in image, does the resistor R74 which is DNP mean that the V3P3_7842 connection is left open or connected to the R75 on pin 2?

Data sheet says that the pin C11 should be tied to GND through 4.7k ohm resistor which has been followed.

My guess is the DNP connection leaves the connection open. Am I right?


texts:
I'd think that switching a relay with 120V AC at the coils would not work due to this: https://gyazo.com/2a26aab1dbc70d3da16d0e5e31f1e759

Is that correct? If so, does that also mean 48VDC is the max voltage the coils of this relay can handle?

What I'm trying to do is switch on/off a small current using a larger one, so that a microcontroller can detect when it is on or off. Is there a easy/cheap way of doing this? Thank you.


texts: AVR Assembly - Operations with two 8-bit registers in 16-bit

texts:
R20 = (4 * R16 + 3 * R17 - R18) / 8

.org 0
start:
    ldi r16, 10
    ldi r17, 20
    ldi r18, 10
    lsl r16
    lsl r16
    mov r20,r17
    lsl r20
    add r20,r17
    add r20, r16
    sub r20,r18
    asr r20
    asr r20
    asr r20

konec:
    rjmp konec

I created this program (ATMega169), to compute the expression and for the sake of accuracy I would need the operations to be performed in 16 bits. I know that there are R26 R27 registers that "act" as one, but I have no idea how to work with it. I need some study material or some kind of advice. Thank you in advance


texts: Finding RAM product/solution for tiny embedded linux system (<1GB)

texts:
I'm finding it quite difficult to navigate among the copious memory solutions available when selecting a RAM solution for a tiny embedded system I'm developing.

I will run an OS such as PetaLinux on a Zynq-7000 SoC and nothing more than 32 MB is required for this. Additionally, I will run a simple graphical user interface on a small touch screen.

This is a battery powered device and I really don't want any excessive resources on the board because of space and energy consumption. I feel a few GB of RAM might be very unnecessary. I also don't want to utilise any soon-to-be obsolete technology either.

Are there any energetic downsides with having excessive RAM or are these negligible?
For lasting technologies, is DDR3 SDRAM the optimal choice?
How do RAM types deviate in energy consumption?

Any guidance is highly appreciated!


texts: Multiple windings on single ferrite ring vs multiple ferrite rings

texts:
My question is does putting cables through multiple identical ferrite rings the same as winding them multiple times on a single ferrite ring?
I have my current setup as follows with multiple ferrite rings.


texts: Can an audio circuit be powered by a switched-mode power supply?

texts:
Most audio circuits are powered with large, heavy transformers and a small ripple after smoothing. SMPS are smaller and more efficient. EMI can be shielded by a metal enclosure and the output filtered for noise suppression.

Especially where the power is going to be further regulated. Why aren't switched-mode power supplies used in audio circuits, eg. power amplifiers, and what improvements can be done to make a SMPS suit an audio circuit?


texts: Is this capacitor 1.2volt or 5volt rated?

texts:
I am having trouble understanding this.  The document says that this cap is rated at 5volt, but it says that it will break down above 1.2volts...

Can someone please take a look and tell me what they mean?

http://www.arborsci.com/Data_Sheets/P6-8012_DS.pdf


texts: I am analyzing a board with safety considerations. In one part of the circuit, PB0 and PB1 of MCU have been logical anded using an IC (PB0 && PB1). Does anyone have faced with such configuration? It is weired, because we can make a logical and (&&) inside the MCU and place the output one just one pin not two pins. Thanks.


texts:
How important is Electroless nickel immersion gold (ENIG) vs normal HASL or hot air solder leveling is?

I'm prototyping a board that has an Spartan 6 FTG256 BGA.  I'm trying to get a 4-layer board with min 5-mil trace width, min 5-mil trace spacing board.  Partly, I'm asking about ENIG vs. HASL because of cost.


texts: 3 phase power convert to 3.3v raspberry pi signal

texts:
I have a project about to mantain a data log of a 3 phase motor, when the more is on and off count that time and save in memory location.
I don't use any server now to save data, I use a Rpi to do all this stuff. Any other controller I can use suggest please.
I want that 3 phase signal on my Rpi when the switch is on, 1- 3 phase AC to 3.3v dc signal?
Thank you.


texts: Bandpass Filter: Single supply op amp design

texts:
I have taken on a hobby project and I am trying to make a circuit which would be able to identify an acoustic signal with a frequency  of 40kHz.

Here is the circuit of a band pass filter for this:

Here is the magnitude repsonse curve for it

The issue is:

1) What would be the best way to detect the signal for the input?

2) This circuit will be mounted on a moving object and so it would be connected to a DC power supply (battery). This means that I would need a single supply op amp which has a GBW of 928k Hz but was also recommended 3.98M Hz.

I am new to this and would usually just try to figure this out myself but I cant for the life of me find an op amp of this specification?

I would appreciate any help.


texts: RF Emissions Testing and Discovery of Hidden Undocumented RF Device

texts: I would like to know is it possible to induce RF emissions (incidental waves (re-radiation) from a RF device that is not transmitting ? The purpose of this testing is discover whether there is a hidden undocumented and undisclosed embedded RF transmission device that is likely in fact powered on but not transmitting and its transmission frequency range is unknown.


texts: "A student tried to make an AC generator consists of a coil of one turn, and cross sectional area of (7.54 × 10^-3 m²), and rotates in magnetic flux density (2.5 × 10^-2 T), and when it was taken out of the magnetic flux in 1.256 × 10^-3 sec an induced emf of 1.5V has been generated." That was the description of a generator, then it asked whether that generator is practical or not? The answer was "No" without an explanation, so could you please explain it for me?


texts: Home Router - How do routers use multiple antennas and MU-MIMO?

texts:
I have few practical questions regarding classic home routers like TP-Link Archer C2 or modern AX10. I welcome longer explanations if it's necessary.

Which type of antennas do home routers use?
Are the "black pointy things attached to home routers" basic dipole antennas?

How does home router use its antennas?
Let's consider router that has 2 antennas (like C2). Does each of them send or receive data (not at the same time) or 1 of them is used for receiving and the second one for sending data.

How does router take advantage of multiple antennas?
For example, let's say there is 1 device connected via Wifi to router that has 2 antennas (like C2). Does the router use only 1 antenna that is closer to the device, or is the communication somehow split and both antennas are used at the same time. If both antennas are used, is one antenna assigned for each device (communication), or can the communication with just one device use multiple antennas as well?

How does MU-MIMO use multiple antennas?
Do I understand it correctly that MU-MIMO takes advantage of multiple antennas by assigning a pair of antennas for each device (or communication stream) for uplink and downlink allowing multiple simultaneous communications? So if the router has 4 antennas, it allows basically 2x2 MIMO, one per each antenna pair. Archer AX10 supports only 2x2 MIMO and it has 4 antennas, so the theory fits.
However, Archer AX20 has 4 antennas as well and it supports 4x4 MIMO. How is it possible?

Is beamforming tied to MIMO?
Is beamforming basically forcing a stronger signal by one antenna in the direction of MIMO device like mobile phone connected to Wifi? Or is it more general and also supported by routers without MIMO, so basically fast switching the direction for each transmitted frame.


texts: Simple BrainTeaser: Running an AC current between two independent amplifiers

texts:
I'm working on a project using an ultrasound method for identifying objects in water. For example, such a device could be used to locate bodies on the floor of an ocean bed after a plane crash. Our technique relies on moving charge between two wireless, independent amplifiers, each powered by their own LiPos.

I have a set-up like this:

On the left side there's a circuit powered by a DC single-supply battery. On the right side there's a second circuit powered by a DC single-supply battery.

The two circuits are oscillators. A signal communicated wirelessly from a host device (not pictured) to each amplifier is non-invertingly amplified at A, while the signal is invertingly amplified at B. When there's a high voltage relative to the first LiPo's ground at point A, there's a low voltage relative to the second LiPo's ground at point B.

Each circuit has a "contact point" against a central load, R, which is a big body of water. The (theoretically) injected charge makes it easier for our product to locate bodies in the water.  The two circuits aren't connected aside from a single contact point on each side.

When I use my oscilloscope, there's no voltage difference between points A and B, even when point A has an objectively positive charge, and B may have an objectively negative charge relative to A. When I use my ammeter, no current is running over the load. (Why is this?)

Does this have something to do with the output impedance of the op-amp amplifiers that I am using to amplify the charge? Are the op-amps unable to take in current and move it to ground? Is there a specific op-amp or amplifier that might allow this?

Does it have to do with the way the oscilloscope or amplifier measures these values? Is current actually moving, just not measurable by these tools?

I've noticed when I add two more contact points, C and D, the oscilloscope/ammeter produces more expected readings. However, I don't know whether current is running downwards (R1, R3), or across the load (R2, R4). Because battery life (and prior investment in design considerations) has been accounted for current only running across the load (and only two contact points), I would really like to find a way to not have to add contact points C and D. This would also ensure current was running solely across the load, and not down along its sides.

First of all, why doesn't current run when there are only two contact points? Would I need to connect the circuits with a wire to complete the movement of charge?

Secondly, how can I test whether current is running downwards (R1 to R3) or across the load? I need current to move across the body of water.

I would really like to build two auxiliary wireless devices that don't need a wire connecting them. But I also need current to move across the body of water, not downward along its sides, ideally with two contact points.

Is it similar to the way charge doesn't move when batteries are connected in series? Is there any workaround?


texts: Enable DTR/RESET by software with an ATMega328 MCU

texts:
I’m building a project using an ATMega328, and for the serial communication and programming it, I’ve connected a USB CP2102 controller.
The problem with atmega328 (and all arduino boards) is that the MCU resets whenever the system sends signals to the DTR pin of the serial port, for example when we have the device always connected to the USB port of a PC and the computer restarts or powers on, the MCU resets itself.
To avoid this behavior, I have a physical switch which opens and closes the DTR connection from the USB module to the MCU reset pin, which works quite well.

My question is, how can I get rid of the physical switch and have the functionality to enable/disable the DTR to reset connection by software using an MCU pin?

I tried by using a NAND gate with 2 NPN transistors with inputs the DTR and a digital pin and output to reset pin, but it didn’t work well.

EDIT:

I am aware of altering the USB port driver files and disabling the DTR, and the RSTDISBL fuse flag, which both are not what I’m looking for. I need a simple way to enable/disable the DTR/reset connection by software and a MCU pin.


texts:
Here is my try at the problem,

A 3.5 digit implies the count varies from 0 to 1999.So for a 2V full scale the LSB or the resolution is 1mV.

Now the input is integrated for 300ms and the integrated value is 0.30114V, which is now de- integrated down while counter starts to count simultaneously i suppose.
Thus the counter should count till : (assuming reference voltage of 0V)
0.30114 / 1mV = 301 (digital output).

MY doubt:
Is my approach correct ?


texts: Debug an Arduino project on AVR Studio 5 Simulator

texts:
I'd like to debug my Arduino Atmega 2560 project on the AVR Studio 5 Simulator.
The thing is, as I understand it, Arduino code doesn't run on the Atmega chip by itself, it uses a bootloader - In my case Stk 500 v2.

So, is it possible to run it on the simulator? and if so, how?

Can I load the bootloader hex file to the simulator, then communicate the project hex to it via serial? Or is there an even easier way to do it?


texts: Is a NRTL / UL mark required for battery powered products?

texts: We have a small 12VDC battery powered projector that uses a 5 watt LED to project an image through a transparency onto a wall Electrically it is equivalent to a flashlight. Does this type of product require a NRTL safety certificate?


texts: Can the SN54LS47 BCD to 7-segment display driver sink current of a full 7 segment display

texts:
The datasheet of the Texas Instruments SN54LS47 says that this part is for use with common anode 7-segment displays on pg 3 para 1 of the datasheet.

Common anode dispay is where all the segments are collectively connected to VCC and we sink current from the one we wish to turn on. The SN54LS47 has open collector outputs to do this.

The 7-segment display being used is the TDSG5150. It is a common anode display. It has forward current of 10 mA as per its datasheet. It has typical forward voltage of 2.4V.

Now if all the segments are on in the display that would be 100mA. The confusion is that the pg 11 of the SN54LS47 gives a "peak output current" of 200mA subject to tW <= 1 ms and duty cycle being 10%.

Q: What does tW mean?

Q: This is a common collector output part, what does it not say "peak input current" instead?

Q: How do I know if this part can drive the 7-segment display continuosly with all displays on and not overheat and be destroyed?

Q: The front page of datasheet says "open collector output" for the SN54LS47. However, the pg 3 says that it features active low output. What does this mean?


texts: passive high pass filter to iphone mic jack

texts:
I'm attempting to input a heart rate signal into my iPhone via the microphone jack. I need to pass the signal through a passive high-pass filter to remove the DC offset before inputting it in to the iPhone.

At first, I tried to use a passive high-pass filter with a 1uF capacitor and a 100k Ohm resistor, since I needed the cutoff frequency to be very low. The signal I measured matched my heartbeat.

Graph 1:

It turns out, however, that the iPhone checks for a "microphone" via impedance matching; the circuit must have a resistance of ~1k Ohm for the iPhone to detect a microphone. Given this, I made what I thought to be a high-pass filter equivalent to my previous one, except with a 100uF capacitor and a 1k resistor. According to the math, they should behave the same.

The signal I measured instead had very large magnitude spikes that were periodic but not in time (by any ratio) with my heartbeat.

Graph 2:

These data were acquired when the circuit was not connected to the iPhone, see notes for details

What might be the reason for this behavior? And are there any suggestions for achieving the behavior I want with a ~1k Ohm resistor ? I'd greatly appreciate any help!

Notes:

1) For data acquisition, I am collecting the data via an Arduino Uno. The x-axis of the graphs represent the sample number, and the samples are collected every 2ms. The analog input of the Arduino reads a voltage between 0-5V, and converts it into an integer from 0 to 1023.

2) The Arduino isn't the most accurate method of data acquisition, but it's very cost-efficient and should be good enough for these purposes.

3) The iPhone mic input might have an internal high-pass filter of ~30Hz, so this might all be a moot point, but I am still curious why I would get this behavior. This should be a relatively simple circuit!


texts: What does it mean for a transistor to be biased beyond cutoff?

texts:
I understand what it means for the transistor to be biased for Class A, AB, and B with regards to the location of their DC operating points (\$I_{C_Q}\$ and \$V_{CE_Q}\$ are found by finding the point of intersection of the DC load line and the transistor characteristic curve).

For the Class C amplifier, the sources I've read say that the transistor must be biased beyond cutoff, but then I don't understand how this can be since there is no characteristic curve beyond the cutoff:

Also, does this mean this type of biasing forces a current (and with an opposite direction with respect to normal operation) through the transistor?


texts:
I'm building a voice ring modulator. Part of it involves a 30Hz carrier sine wave to modulate the voice with. Since I'm trying to build a portable device it will be DC powered, and since a function generator is not really portable or DC powered, I don't thinks that's an option.

Crystal oscillators work at the MHz range so I'm guessing that's not the way to go either. I could play a 30Hz wave on an old mp3 player and use the audio output, but if there's another way involving analog components that'd be much better. There's no need for a lot of accuracy, just any wave from 20-40Hz will probably do, I would say it doesn't even need to be really stable either.

What approach can I take?


texts: what is an "Adressable" I2c device, and what does it mean?

texts:
The MCP3021 is a standard 10-bit ADC with an I2C Interface. It's datasheet can be found here.

In the general description, it says:

  The
  device is also addressable, allowing up to eight devices
  on a single 2-wire bus.

What does it mean to be addressable, how are devices addressed, and why does it say only 8 devices are allowed on one bus? Shouldn't it be much more?


texts: Saving Oscilloscope Traces as Compressed Bitstream

texts:
I have been recording the output of a comparator by having its output (essentially a bit stream with 3.3V swing @ ~20 Mbps) terminating in an SMA connector, and connecting that to an oscilloscope (which is used to record the traces). This is fine for short periods like 0.1s, but becomes unpractical for larger time periods as the traces require to much hard disk space to record (~1 GB/s) because of the required oscilloscope resolution to differentiate between the bits in the comparator output bit stream.

What I'm looking for is either some sort of DAQ device that takes output of the comparator, and saves it as a stream of 0's and 1's and compresses it, or a circuit that could be designed to carry out this task.

How do I save the output of a DAQ device and compress the bitstream?


texts: Can anyone give me a really simple explanation of how transistors work?

texts: I'm currently into electronics and learning about it as a whole. Does anyone think that they could explain transistors to a basic level. I've read lots of websites etc, but none if them make any sense to me! I'm looking to understand to what extend they activate and how to use them as a switch.


texts:
I started creating a scheme for 8086 based computer now I'm in trouble with memory addressing.
I know a 20 bit wide addressing line can address up to 1024 KB of RAM and that pin A0, when high, select all the even memory banks and when BHE is high the odd memory banks are selected (yes I know there is a bit more complicated logic circuit to do this).

I choosed a setup where there are 8 chips (6x 128 KB are SRAM chips and remaining 2x 128KB are EEPROM chips).

Reading online I know that  using a M74HC138B1R (a so called 3:8 decoder) I need to use A17, A18 and A19 to decode what chip select, ending having the lines A1-A16 to use for chip addressing. The problem comes when according to IS62C1024AL datasheet (chip I wish to use as SRAM) the chip use 17 lines for addressing (A1 up to A17) meaning 17 bit=128KB. But doing this I end up with 1 address line in conflict (A17).

I can't figure it out how to exit this weird situation and I can't figure it out if the A0 still available for addressing, my assumption following the logic is no.
Another thing that seems obvious to me was searching for a 2:8 decoder that apparently it doesn't exist.

Any tip is much appreciate, may be I'm currently missing something stupid I can't figure it out now.


texts: Audio 3.5 mm jack unique hardware key for iOS/Android

texts:
Here is the situation. Let's say there is a set of small devices supplied with an audio 3.5 mm jack. Each of these devices represent sort of a unique hardware key value (say just a number or a string). Let's also say there's is an iPhone/Android app, that needs to detect that one of these devices is plugged in on start up or the plug-in status (unplugging one device, and plugging in another) has changed. The app should have the full knowledge of whether any is plugged in, and if yes - which one exactly. There is no other interaction needed so far.

What would be the easiest (for a guy, who never dealt with any kind of hardware) and the cheapest (in production of such 3.5 mm pluggable devices) solution for the situation.

I've searched around, and most of the examples are quite complex and are about more sophisticated devices, like external sensors, programmable microcontrollers (Arduino, Hijack, etc.), which seems a bit of an overkill to me. But correct me if that's the way to go.


texts:
I'm designing a PCB with 4 layers, but I've seen different recommendations about layer distribution. I'm considering that:
Top layer - Signal + short  traces of VCC
2nd layer - Signal
3rd layer - VCC
4th layer - GND
Can I fill all area around with ground in each plane and place several vias to connect grounds across the layers? Can I have the VCC layer filled with ground plane?
The circuit has a nordic + lora radio in one module castellation. Output antenna has a connector over the module already, so no need to design microstrip lines.
What is the minimum recommended power trace width for a 3.3 V and 150 mA maximum? Shall I have very large traces in 3rd layer and not filled with ground around?


texts:
can you help to simply the following boolean expression?

F = /ABC + /AB/C + ABC + AB/C + /A/BC + /A/B/C

Using an online I found out the solution which should be

= B + /A

But I am not sure of the last step

= /AB(C + /C) + AB(C + /C)  +  /A/B( C + /C ) simplify using rule 6

= /AB + AB + /A/B    (OR Distributive Law)

= B(/A + A) + /A/B  simplify using rule 6

= B + /A/B      expand using Distributive law

until here (B + /A/B) I think I am correct

From here below I am not sure I took the right way

= (B + /B)(B +/A)     AND Distributive law A + (B.C) = (A + B).(A + C)

= (B + /B)(B +/A) simplify using rule 6

= B + /A


texts:
I have a small amount of Attiny85-20PU which I am trying to program with a stk500v1-type-programmer (for the sake of simplicity say an Arduino with ArduinoISP-Sketch).

My first attempts with that part were with the Arduino-Environment, but in the long run I want to use Atmel Studio (in connection with AVRDude as well).

But I am getting a Yikes-Type error from AVRDude. Verbose output shows that it doesn't recognize device signature (being 0x0).

The programmer, configuration (like baud rate) and wiring must be correct because I can successfully program another Tiny85-compatible board (the Nanite85, see https://cpldcpu.wordpress.com/2014/04/25/the-nanite-85/, it is internally clocked, I am not using the bootloader/USB). I have just double checked it, still works. Also, programming an Atmega328 in-circuit (with external clock) is not a problem with that programmer. It can't be a single defective part, I have checked it with two different items.

So my hot guess is that my Attiny85's are fused for external clock. But the datasheet from Atmel (http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-2586-AVR-8-bit-Microcontroller-ATtiny25-ATtiny45-ATtiny85_Datasheet.pdf, section 6.2 clock sources) clearly says that it should be factory-fused to "Calibrated Internal Oscillator". Could it be that this depends on the concrete model of the chip, contrary to the datasheet?

The chips seem properly labeled with Atmel logo and all. Although I bought them on Ebay, I can hardly imagine that any chinese copycat manufacturer would bother with an oldschool 2€ part.

Can I find out if the clock fuses are the problem without soldering the Attiny together with a crystal?


texts: Meaning of firing angle in the context of a DC input supply

texts:
I've learnt the meaning of firing angle only in the case when the input supply is AC. As shown below

So what does firing angle of 60,120,180 degrees mean when the input supply is DC? Like in a six step voltage source inverter as shown below

Moreover, what is the meaning of 180 degree conduction mode? I get that the IGBT stays conducting for 180 degrees, but what 180 degrees of what cycle? What is the base/reference against which this 180 degrees is measured?


texts: How will I know the Power Efficiency of a load?

texts: I have a thevenin circuit with a source load. How will I get the Pin and Pout?


texts: I have a Dell monitor I took apart to examine the LCD for a future project and it has these 4 wires coming out of the side of the LCD marked LRB. After examining the board that I removed the LCD from I can't figure out what they are for.


texts:
I try to power EL wire at a chosen frequency. For this I have a microcontroller generating a square wave signal at the given frequency; this signal oscillates between 0 and 3.7V and the current is limited to 20mA. I want to run this through a transformer to convert to about 110V AC.

The transformer needs an unbiased signal: I think of adding a capacitor in series. (I learnt that this is called a coupling capacitor).
For amplifying the power of the signal, I will need at least a transistor.

I thus drew the following circuit:
(V1 is the square signal, V2 is the Vcc supply, L1 is the load — transformer primary). This circuit does not work (after a very short transition time, L1 has no current). This is probably because, during the “off” part of the square signal, the NPN transistor behaves as an open collector. I observed the same behaviour when simulating the circuit from this similar StackExchange question.

Another idea would be to build a LC oscillator, forced by the signal through the NPN transistor:
(simplified model).
However such a circuit will be limited to the neigbourhood of the resonant frequency of the LC oscillator.

In trying to fix the first circuit, I thought of two possibilities for preventing the open-collector situation: either add a pull-up resistor (between the collector and V2), or a PNP transistor in the same place (thus complementary with Q1). Would either of these be a workable solution?


texts: I am modeling different circuits in LTSpice and I cannot for the life of me find ways to annotate the plots with measurements. How can I perform simple measurements such as measuring 3dB points, max and min, rise time ect and annotate this on the plot?


texts: When did DC-DC buck converter modules become so popular?

texts:
Is it just me or from maybe since 4 years ago every project online for hobbyist electronics is using switch-mode power circuits in them?
Looking back 15 years ago at projects from when I started doing electronics as a hobby, virtually every project used unregulated power supply circuits with linear regulators depending on the application.
Have DC-DC (step-down) buck converter modules become more popular/mainstream for hobbyists in recent years, or was I simply unaware of their popularity?


texts: Advice on connecting heater directly to SP2 relay of PID controller?

texts:
I have an old Omega CN-9121 PID Controller and a 105Watts 115V Fibre heater mantle with an inbuilt K-type CHromel-Alumel temperature thermocouple also attached into it. I plan to use the PID controller to control the temperature of the heater. Looking at the manual below:

Manual for PID

I decided that I wanted to use the inbuilt SP2 relay in the PID controller. From the wattage of the heater, I know it would draw a maximum of only 1A and is going to be below that. The SP2 output from the PID has a small 5V energized relay with 3A load capacity. I would like to know if it is safe to use the heater directly with the SP2 relay terminals of should I use the SP2 relay to run another AC relay for the heater?


texts: Can I use an NPN BJT transisor as a standard switch?

texts:
Is is possible to use a NPN transistor as a normal switch?

If I put 5 V on the transistor base the switch is closed and if there is 0 V on the base the switch is open.

Does the transistor need to be connected to Vdd or GND? I want this switch to be in the middle of a circuit.


texts: When do you need buffers/drivers on buses in a microprocessor design?

texts:
I was browsing Microprocessor Interfacing Techniques and found this pharagraph:

  The microprocessor's buses must connect to every memory and peripheral input-output chip in a system. All MOS microprocessors lack the output drive needed for a large system. Because of this, buffers or drivers are used to boost the driving power of the buses.

I'm not sure what the definition of a large system is, but from the (simple) microprocessor hobby system designs I've seen the usage of buffers/drivers doesn't seem to be common.

How do I know when I need to use buffers/drivers in my design? My gut feeling based on my rudimentary knowledge is that I probably need it when my signals go off the board and interface with unknown components, e.g. in a S-100 system. Is this something I can calculate?


texts: A "Voltage Backdrive" on DC-DC Converters?

texts:
Below is a circuit I'm making. A 24 VDC PSU (VCC) goes through this switching regulator and outputs 5V to power the load. However, the load can also be powered directly by the USB 5V (USBVCC).
Now if the USB is connected but the 24 VDC PSU isn't, I'm getting a ~3.3V reading on the input line of the regulator. Is there a specific name for this? I've been calling this a "voltage back-drive" for now. Also, is this ok for the regulator or will it be damaging in the long run?

simulate this circuit – Schematic created using CircuitLab


texts:
I am trying to solve this problem, the answer should be 15/20 = 75%.

However, I am not sure how this was calculated and want to understand the underlying concept.

A program core consists of five conditional branches. The program core will be executed thousands of times. Below are the outcomes of each branch for one execution of the program core (T = taken, N = Not taken).

 Branch 1: T-T
 Branch 2: N-N-N
 Branch 3: T-N-T-N-T
 Branch 4: T-T-T-N
 Branch 5: T-T-N-T-T-T

This behavior remains the same. For dynamic schemes, assume each branch has its own prediction buffer and each buffer initialized to the same state before execution.

What is the prediction accuracy for the 2-bit predictor, initialized to weakly predict taken? (Answer is at the beginning but I'd like to understand the concept of the calculation.)


texts: Will continuously polling I2C port expander damage it or reduce its life?

texts:
I am using I2C port expanders namely TCA9554A and TCA6424A in my project. I have two options to read the inputs - (a) wait for interrupt and read (b) continuously keep polling the chip for any input changes.

Here is the sample arduino code to read a port:

Wire.beginTransmission(0x22); //0x22 is device's i2c address for TCA6424A
Wire.write(0x00); //Command to access port 0
Wire.endTransmission();
Wire.beginTransmission(0x22);
Wire.requestFrom(0x22, 1); //Requesting port state as 1 byte data
byte inputs=Wire.read();
Serial.println(inputs, BIN); //Printing the received state data

My concerns regarding polling way are the following:

1) Whether I2C lines are fine with handling traffic continuously for extended period of time. My project will be running for months (if not years). Only downtime will be when mains go off but that won't happen for more than an hour or so in a month's time period.

2) Since reading the state involves writing some data to some registers, will it wear off those registers causing an early failure of the port expander than it's expected lifetime.

Datasheets:

1) TCA9554A

2) TCA6424A


texts:
Why does a steeper load line gives higher current gain, while a flatter line gives higher voltage gain? I read multiple tutorials where they only provide a graph without explanation and I can't visualize why it is.

For the upper load line, if a small or input signal fluctuates on a DC-biased base current (e.g. 40uA in the image) at a fixed operating voltage of \$V_{CE}\$, then the output amplified current, or \$I_C\$ fluctuates around 5mA. And for the lower load line, if small signal rides on the 20uA base current, output collector current fluctuates around 3mA with more of less the same amount.  In either case, I don't see where \$ \partial I_c \over \partial I_b\$ differs for different load lines. Same question for the voltage gain.

[EDIT]

Is that what it means by saying a steeper line gives higher current gain?


texts:
I am using in a project TL081 operational amplifiers and an INA118P instrumentation amplifier.
Both need a ± 15 V Symmetric Power Supply, however I have seen some projects in which it uses single supply.

I intend to build a portable system that sends electrical signals to the body (sinusoidal voltage of  2 V pp with 100 kHz to 1 mA). And for this I will use the op amps TL081 to make a high pass filter, a current source and a voltage follower. With the INA118P I will amplify the signal.

My questions:

I'm going to use arduino, I intend to use a single 5 V supply and GND.
What's the difference between a Symmetric Power Supply and Single Supply?

The TL081 does not have much information about Single Supply Operation. For the voltage that I intend to work, is 5 V enough?

Thanks!


texts: How to connect the power for VREFSD pin and anlog pin in STM32F3273 (ARM Cortex-M4) for SDADC application?

texts:
I have an analog amplifier which is powered at single-supply power and have an analog ground of 1.25V.

I want to perform sdadc for my analog output. I am using STM32F373 (48pins), which is an ARM Cortex-M4.

I am confused with the circuit connection between MCU and amplifier. (analog output, analog ground and VREFSD+ and VREFSD- pins)

STM32F373 datasheet

1. Analog Output from my amplifier

Refer to stm32f373 datasheet, page 33, pins definition table.

Since I am using SDADC1 for my application, so I connect my analog output as SDADC input for the mcu.

2. Amplifier Analog ground and VREF_SD+

Refer to technical reference manual, page 225, 13.3 SDADC pins, Table 36.

Since I am have an analog ground for my amplifier, so I think I should make the VREF_SD+ as  external reference. With the description of

When the external reference is selected (REFV=00), this
pin must be driven externally to a voltage between 1.1 V
and VDDSDx.

Therefore, I connect the VREF_SD+ pins in between the VDD (3.3V) and my analog ground (1.25V)

3. VREF_SD-

I connect the VREF_SD- to 0V ground.

Below is the overall view of my circuit connection:

I am not sure about the connection for part 2 (VREFSD+), am I doing the right thing?

I also not very sure, what is the need of VREFSD+ and - in SDADC application. From what i understanding is to set the input voltage range limit with VREFSD+ and VREFSD-. Can someone elaborate a bit further on this? Some background explanation is great.


texts:
I would like to display a bode plot of a buck-boost converter  using Matlab, so I got the figure shown below, If we look closer to the phase plot, we see that it starts from 360°.
My wish is to make the graph starts from 0° rather than 360° in order to make the reading easier to me.

What should I do to make the phase plot starts from 0° ?
Another question is how can I display the gain at a desired crossover frequency in the graph ?


texts:
I recently became very interested in electronics and read few books about it (I never learn electronics in school). I'm still new to the concepts (and don't fully understand them yet), but I decided to apply all I learned in practice and build the electronics for a RC boat. I started with a simple thing - to have a backup battery circuit, that will switch from main to backup battery, when main voltage is below a certain level. For my boat I will use 14.8v LiPo batteries - one 10Ah as main and 2Ah as backup. When main is drawn, the backup will be switched in order to return the boat to the shore.

The very simple schematic that I came with is the following:

It is a very simple circuit, I use a commercial RC latching Lipo Saver module that will cut-off the voltage of the main battery if it is below 13v. This is because I want to focus on the switching part first, and once it is clear how to implement it - then I will work on the cut-off part. (I will also appreciate some ideas how to implement latching lipo cut-off)

So, this seems to work (at least in the simulator), but has one disadvantage - it consumes certain amount of energy just to get running. Depending on the relay - it is between 30 and 150mh.

I tried to built another circuit with MOSFET, where the relay is only powered (by the backup battery, which is fine) when main battery is off and I came with the following:

I use N Depleting Mosfet which is supposed to block D-S in case G-S voltage is negative below a certain threshold. I cannot simulate thin since the software I use does not support depleting mosfets, so I have questions:

First of all - does this looks reasonable to you? Any major mistakes / issues?
Is it ok to mix both + and - voltages on the same wire (but on different circuits). This is the case with the wire that goes from the source of the MOSFET.
If the second circuit is totally wrong, how I can fix it using N Depleting Mosfet. I have some idea how to do it with P Depleting Mosfet, but they seem to be more rare compared to N Mosfets (Digikey show very few P Depleting Mosfets compared to N Depleting Mosfets). From a practical standpoint (I don't know why) it is easier to find N Depleting Mosfet.
Finally, once the switching part is completed and in a workable state, I would like to get some advices how to implement the LiPo Saver part by myself. I'm interesting in a latching switch - i.e. once the input voltage is below a certain threshold, to cut-off the battery. Once it is off - do not turn it on again event if the main battery voltage goes about the threshold, unless the system is completely powered off or a "reset" button is pressed.


texts: What are different ways to 'elongate' an electrical pulse?

texts:
I'm designing a low-cost system to record femtosecond laser pulses and characterize the average power and shot-to-shot deviations (of the laser pulses). A photodiode seems to be the economic solution, but I'm running into issues on the ADC side: the laser-induced pulse coming out of the photodiode is on the order of 10's of nanoseconds, requiring expensive ADC solutions to properly record. So I'm searching for analog circuits that might somehow temporally elongate these electrical pulses, allowing me to sample more points across the signal and accurately measure it. Simply adding some capacitance might work, but I'm looking into other solutions (peak/envelope detectors, etc.)

Currently, the pulses I get from my photodetector are about 30-40 ns wide and a few volts (up to 4V) in amplitude.

I'd like to be able to measure RMS/Average power of the laser (which is essentially measuring RMS/Average of the photodiode output) as well as shot-to-shot deviations (this is the real tough one, not sure its possible with my requirements). I want the lowest possible sampling rate (slowest ADC) to save on money. It will probably be in the 10-100 MS/s range

Thanks for your thoughts.


texts: Mounting a PCB in an Extruded Aluminum case

texts:
I want to make a case for a PCB using extruded aluminum. (Such as the IPOD nano shown below, and the portable amp under it).

How do I mount the PCB inside the alumimum extrusion? (I know some come with slots but are there different options?
Who are some good suppliers of extruded aluminum? (bonus if they do milling on small quantities too)


texts:
How exactly does one calculate the voltage of the marked nodes and arrive at the numbers in the picture (1.75 and 1.628)? I fail when trying. :(

simulate this circuit – Schematic created using CircuitLab

Background:

I'm trying to get a better basic understanding of electronics and as an exercise for myself I'm trying to grasp the maths in a 7-bit resistor ladder DAC. I've managed to calculate the various voltages of all the nodes for each case where one digital pin is HIGH and all other LOW. Things get more complicated for me when two or more pins are HIGH at the same time and now I'm confused on how to arrive at the numbers in the picture. The picture is the circuit when two pins are HIGH. When trying to calculate the voltage of the marked node rightmost in the picture (with the actual value of 1.628V) I concluded that R1 and R3 are two resistors in series, so I treated them as one resistor of value 330 ohm. Then when I bring R2 into the calculation I arrive at 330*350/(330+350)=169.85. So using this value together with R4 and calculating voltage I come up with this: 5*150/(150+169.85)=2.34. Now, obviously I'm failing big somewhere, the question is where?


texts:
I seem to be getting random character in my USART output with an ATMEGA8

uart.c

#define FOSC 8000000
#define BAUD_RATE 9600
#define UBRR_VALUE (uint16_t)(FOSC/16/BAUD_RATE-1)

#include "uart.h"

volatile u8buf UART_RCV_BUFFER;
FILE uart0_str = FDEV_SETUP_STREAM(UARTSendByte, UARTReceiveByte, _FDEV_SETUP_RW);

ISR(USART_RXC_vect)
{
    //got a byte from USART. add to buffer
    volatile uint8_t data;
    scanf("%c",&data);
    if((UART_BUFFER_WRITE(&UART_RCV_BUFFER, data)==1) || (data=='.'))
    {
        //either buffer full or '.' received
        //stop the UART receiver unit + disable interrupt
        UCSRB &= ~((1<<RXEN) | (1<<RXCIE));
    }
}

ISR(USART_UDRE_vect)
{
    volatile uint8_t data;
    if(UART_BUFFER_READ(&UART_RCV_BUFFER, &data)==1)
    {
        //end of buffer reached. nothing more to transmit
        //disable RX
        UCSRB &= ~((1<<RXEN) | (1<<RXCIE));
        //reset buffer
        UART_BUFFER_INIT(&UART_RCV_BUFFER);
        //enable  RX side
        UCSRB |= ((1<<RXEN) | (1<<RXCIE));
    }
    else printf("%c",&data);
}

void UART_WRITE_STRING(char* str)
{
    //Sending a string without any command
    //disable RX/TX interrupts
    UCSRB &= ~((1<<RXCIE) | (1<<UDRIE));
    printf("%s",str);
    //re-enable RX/TX interrupts
    UCSRB |= (1<<RXCIE) | (1<<UDRIE);
}

void UART_INIT(void)
{
    UBRRH = (uint8_t)(UBRR_VALUE>>8); //set UBRR register
    UBRRL = (uint8_t)UBRR_VALUE;
    UCSRC = (1<<URSEL) | (1<<UCSZ1) | (1<<UCSZ0);//set frame format: asynchronous,8data,1stop,no parity
    UCSRB = (1<<TXEN) | (1<<RXEN) | (1<<RXCIE) | (1<<UDRIE);

    UART_BUFFER_INIT(&UART_RCV_BUFFER);
    stdin=&uart0_str;
    stdout=&uart0_str;
}

void UART_BUFFER_INIT(volatile u8buf *buf)
{
    buf->index = 0;
}

uint8_t UART_BUFFER_WRITE(volatile u8buf *buf, volatile uint8_t data)
{
    if(buf->index<UART_RCV_BUF_SIZE)
    {
        buf->index = data;
        buf->index++;
        return 0;
    }
    else return 1;

}

uint8_t UART_BUFFER_READ(volatile u8buf *buf, volatile uint8_t *data)
{
    if(buf->index>0)
    {
        buf->index--;
        *data = buf->buffer[buf->index];
        return 0;
    }
    else return 1;
}

int UARTSendByte(char u8data, FILE *stream)
{
    if(u8data=='\n')
    {
        UARTSendByte('\r',0);
    }
    while(!(UCSRA&(1<<UDRE))){};
    UDR = u8data;
    return 0;
}

int UARTReceiveByte(FILE *stream)
{
    uint8_t data;
    // Wait for byte to be received
    while(!(UCSRA&(1<<RXC))){};
    data=UDR;
    //echo input data
    UARTSendByte(data,stream);
    // Return received data
    return data;
}

main.c

#include "uart.h"
#include "twi.h"

int main (void)
{
    DDRC = 0x01; //set PC0 as output
    PORTC = 0x01; //turn on PC0
    //PD0 = RXD = INPUT
    //PD1 = TXD = OUTPUT
    DDRD = 0x03;

    UART_INIT(); //initialize UART
    sei(); //Enable global interrpts

    //_delay_ms(500);

    UART_WRITE_STRING("Hello World ! 1:)\n");
    UART_WRITE_STRING("Hello World ! 2:)\n");
    UART_WRITE_STRING("Hello World ! 3:)\n");
    for(;;)
    {

    }
}

This upon execution should give me

Hello World ! 1:)
Hello World ! 2:)
Hello World ! 3:)

But what i get is

\n\nHello World ! 1:)
Hello World ! 2:)
Hello World ! 3:)

the number of \n is random. Sometimes there is none, sometimes 1 or 2 or 3. Any idea what I am doing wrong here?


texts: Suspicious definition of erlang distribution in Verilog-2005 spec

texts:
The $dist_erlang function in Verilog-2005 takes an argument called mean. Some information about the mean argument of $dist_erlang is found in this paragraph from section 17.9.2 of the spec:

They also provide C code for how simulators ought to internally implement $dist_erlang (from page 320 of the spec). This code implements a formula that can be found on Wikipedia for sampling an Erlang distribution.
erlangian(seed, k, mean)
long *seed, k, mean;
{
    double x, log(), a, b;
    long i;
    x = 1.0;
    for(i = 1; i <= k; i++)
    {
        x = x * uniform(seed, 0, 1);
    }
    a = (double)mean;
    b = (double)k;
    x = -a * log(x)/b;
    return(x);
}

I'm no expert on statistics, but I'm pretty sure that the multiplication by mean / a at the very end of this function is not gonna result in a distribution whose mean is mean. This would imply that every Erlang distribution sampled from using the equation on Wikipedia has a mean of 1, which definitely isn't true.
Am I missing something here, or is this an honest to goodness error in the Verilog spec?


texts: Programmable gain instrumentation amplifier with R-2R ladder and analog multiplexer

texts:
I want to build a programmable gain instrumentation amplifier with power of two possible gains (1x, 2x, 4x, 8x...). Is there a way to use a R-2R resistor ladder and an analog multiplexer in order to tune the \$R_{\text{gain}}\$?

On the web I found this way to make programmable gain amplifiers using a R-2R ladder and an analog multiplexer but I don't want to attenuate my input signal as it is already small, I'd lose it in the noise in this way.


texts: How to design the A-B amplifier? I mean I have understood the working but how do i choose the values?

texts:
We have a college project to make an A-B amplifier. I have a basic layout of the transistor amplifier. Plus i have chosen the transistors I want. There are : 2N4401 (NPN) and 2N4403 (PNP).

1)My source is a song being played from my mobile. Here I have taken an AC Voltage of 16pk.
2) How do I modify my circuit for it.I realised Higher the Vcc value I take, the output increases more. Why? And what would be the ideal value?
3)Have I selected the wrong diodes? If I have so which one is suitable for the transistors I have chosen?
4)Why is my positive output waveform increasing with each increasing second?Also why is my Ie of npn decreasing?

EDIT 1: I Have changed the circuit after comparing it more carefully with the suggestions other users have given me. The Schematic is attached below with the output. I noticed other users complaining that my questions have been made blindly. Hence, I have been more precise now.
My Input here is a song being played from my mobile/smartphone. I will connect to the amplifier using it's audio jack. Thus, the song will be played on the speaker (here RL).
Firstly, when I make it on a breadboard the input here will be the song right? So, will the song even play (w/t distortion). Cause, Here I have taken a sine wave input and according to the simulation it is just increasing the amplitude.
Secondly, As pointed out by @jock my knowledge of the amplifier design is limited. I have seen probably all the videos relating to this amplifier on youtube . So, I know it's working but I am really confused about how to design one. Is there anywhere I can read up on this?


texts: ATMEGA8 with 8Mhz crystal just running at 1Mhz

texts:
I have a ATMEGA8A-PU with a 8Mhz crystal oscillator (T8.000 is 8Mhz isn't it?) and the following C code:

#define F_CPU 8000000UL

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

int main(void) {
        DDRC = 0b00100000;
        while(1) {
                PORTC ^= 1 << PORTC5;
                _delay_ms(1000);
        }
        return 0;
}

So, just a simple code, that switches the LED on and off every second.

But when I write this program to the controller, the LED switches on/off after about 8 seconds. When I replace F_CPU to 1000000UL, it switches nearly every second.

So I thought, it's a problem with the fuse bits, but they are set to F1 (low) and D9 (high) which looks good to me.

Anyone who has an idea how I get the full 8Mhz?


texts: I am trying to understand what the Data Stream coming through the Component Wires when they are used to connect to a Monitor from a DVD/BLURAY player, Hauppaugge or whatever.  Is there a set of IEEE Standards, Broadcast Standards or Computer Connection Standards for the methods used like the old NTSC, PAL or SECAM standards, that were used previously.  Is there any summary of the options for the various ways of transmitting digital data over these lines (encryption, packetizing,serial and parallel transmission).  I understand that the audio is analog but I am more interested in the various ways that are used with the digital video connectors used between the various devices.  (Regardless what they use CAT 5, audio cable and/or HDMI).


texts: What is the equation for mechanical efficiency of a 3 phase induction motor?

texts:
I know that mechanical efficiency is n= power output/power input, but I don't know how to find each of those. I have to find the efficiency at full load running speed.

I was only given mechanical losses (1.04kW), and that's why I'm confused because most equations talk about copper and stator losses and I'm not given them.

If anyone could help explain what equations to use that would be a great help!

Here's an update of other values I was given:

Input voltage= 400V

No. of phases= 3

Frequency= 50Hz

Running speed= 11.9(rev/s)

Total number of poles= 24

Rotor R per phase= 0.66(Ohms)

Rotor X per phase= 5.3(Ohms)

Effective rotor-stator turns ratio= 0.86:1

Mechanical losses= 1.04(kW)

% of running load at start-up= 83%

I don't know if you needed all of that but was not sure what you need to work out efficiency.

Here's an update of what I know so far:

Efficiency (n)= Pout/Pin

Efficiency= (Protor - Presistive rotor - Pmech losses)/(Protor - Presistive rotor)

And to find Protor (which is power flow in rotor)= P= VI. I got my current by doing Ir=s(N2/N1)E1/sqrt(r2^2+(sX2)^2) as it wasn't given.

To find Presistive rotor would I do Prr= ((3Protor)*(2I))-r.

So Effiecincy= ((Protor - Presistive rotor - Pmech losses)/(Protor - Presistive rotor))*100

Are these equations right?


texts: How to read an audio signal using ATMega328?

texts:
I was trying to use the ATMega328 ADC port A0 to read a signal. The hardware I used was:

Seeeduino Stalker
Electronic Brick Shield
Microphone Electronic Brick (I found a link to the original developer store)

The signal I got seems to be only the positive part of a sine wave. Is it possible that this setup isn't suited for audio recording? What I have to change?


texts: Duplicate Eagle part (package) in same libraray

texts:
How do I duplicate a package in my Eagle library (without grouping, and copying and pasting the contents or opening up the XML of the library in a text editor)?

I know I can copy between libraries, but I can't see how to do it within the same library as there is no option to change the name.

Thanks
Thomas


texts:
Here is an interesting article about mixing stereo.
Most important issues when mixing stereo are :

interaction between channel
crosstalk
noise

Interaction between channel is explained here in 1.0 with passive mixing, from that :

  It would be possible to make the output impedance of all equipment
  much higher, so direct mixing would not cause any circuit stress. The
  problem would then be that we are back to the position we had when
  valve gear ruled ... high impedance causes relatively high noise and
  high frequency rolloff with long cables. Cables can also become
  microphonic, and this is why so many pieces of valve kit used output
  transformers - to provide a low impedance (optionally balanced) output
  to prevent the very problems described. Low output impedance is here
  to stay, as are mixers, so now we can examine the methods in more
  detail.

But for crosstalk, in the mixing passive circuit, how do we calculate it? We can find different methods to measure it. but for simple mixing circuits I did not found any documents describing how it be computed.

We can find an example in here :

  The problem arising from using all three outputs (the two original and
  the new summed output) is one of channel separation, or crosstalk. If
  the driving unit truly has zero output impedance, than channel
  separation is not degraded by using this summing box. However, when
  dealing with real-world units you deal with finite output impedances
  (ranging from a low of 47 ohms to a high of 600 ohms). Even a low
  output impedance of 47 ohms produces a startling channel separation
  spec of only 27 dB, i.e., the unwanted channel is only 27 dB below the
  desired signal. (Technical details: the unwanted channel, driving
  through the summing network, looks like 1011.3 ohms driving the 47
  ohms output impedance of the desired channel, producing 27 dB of
  crosstalk.)

Some technical details are given, but it's not clear to me. Can someone give detailed steps to compute crosstalk for this example? A simulation example could also helps.


texts: ATmega 328p Using crystal with fuses set to "ceramic resonator"

texts:
Would it work in such arrangement?

I'm trying to figure out what mistake I made setting the fuses so that the chip stopped working with SPI programming. I think I set the correct CLKSEL fuses but the SUT fuses I set incorrectly for slowly starting ceramic resonator instead of crystal. Would this still work with a crystal?


texts:
I am trying to complete the circuit shown above. I am having trouble as the ground connection is not clear to me. Please help me to complete that circuit.
And also tell me how to connect C5 ground connection and what happened if I ignored that capacitor and ground connection or connect to negative port.


texts: How does "RS485 Pi" 2-wire transceiver connection work

texts:
I'm familiar with connecting a RS485 transceiver with a separate DE wire. However, on this pi hat, they used just Rx and Tx, and I'm not quite sure how it works. (or does it work?)

Looks like the transceiver switches to Tx with each transmitted 0, and then immediately goes back to Rx mode? Wouldn't the bus enter some kind of 3-state mode then, instead of sending 1? Or is this some hack with the gate capacitance?


texts: Current is the amount of electrons passing through a wire. Can we say that voltage is the speed of those electrons?


texts:
We have been soldering LED boards together for years with no issues. Recently engineering has gone to a new board design and we got the first samples in this week. Because of the improved design and better heat dissipation of the board my team is have great difficulty soldering lead wires and connecting boards in series with wire to the solder pads on the LED boards.

The solder will not stay molten long enough to insert a wire even with the soldering tip still in direct contact with the solder pad. I have tried different temperatures and methods but all have resulted in failed solder joints.

Looking for any advice on methods/ materials to try out.

We are currently using Kester lead free 275 .062 wire at 625 degrees


texts: SPI Isolation : What is the point of the ADuM3151 etc

texts:
I was looking at ADI's isolators designed and marketed for SPI, such as the ADuM3151. I'm interested to know what makes these isolators special, in that what the point of them is.

The isolators don't float MISO when the slave is not selected, which I would have thought would be the whole point of an SPI-specific isolation part. Specifically, from the datasheet :

  To allow compatibility with nonstandard SPI interfaces, the MI pin is
  always active, and does not tristate when the slave select is not
  asserted. This precludes tying several MI lines together without
  adding a tristate buffer or multiplexor.

The ADuM3150 has additional circuitry that tries to deal with propagation delay problems on the MISO line (a painful DELAY_CLK approach), but the ADuM3151,2,3 do not even have that. In both cases, to put the isolator onto an SPI bus I still need to look for a tristate buffer with low propagation times to be able to cut off MISO appropriately without adding even more delay.

Additionally, the limited speed of the ADuM3151A, for instance, and its complete disregarding of SS, means I probably wouldn't be able to have a mixed bus with high speed SPI on the non-isolated side without worrying about noisy garbage showing up on the isolated side. The deselected chip select should make sure that the SPI slave does not act improperly, but having all those output drivers trying to push signals that do not need to cross that isolation barrier makes me worried about noise coupling.

Why would I want to use one of the SPI isolators instead of the ADuM7642, for example, has considerably better propagation times and should work just as well, if not better, than the ADuM3151 for SPI applications.


texts:
If I have a device that draws 5 amps at 12 volts, I can use any 12 volt DC adapter that can provide at least 5 amps.

Why don't all DC adapters have the capacity to provide loads of amps!? If all DC adapters provided e.g. 1000 amps, we would only need to care about the voltage value.

Do too many amps make DC adapters bulky, inefficient, or expensive?


texts: Surge protection not working on a home projector

texts:
I have a problem with power supply and no idea of how to solve it.

The whole system consists of a projector, an AV receiver, a subwoofer and a PS4. Around 800W. Early when I just got the projector it looked for a while that all was fine and dandy, but later some power disturbances started happening.

So exactly what happens is, while playing or watching movies or whatever the whole screen suddenly displays white noise and the sound disappears. this is happening just for a split second, then i see the projector screen looking for a source also for a second or so and then everything starts working again. The PS4 doesn't restart, the game seems to be continuing while this happens. Sometimes there isn't even a white noise seen, just black screen in which projector is looking for source, quickly finds it again and the display is back again.

I have noticed that around 80% of the time this is happening because of other electric triggers, for example switching on the lights in a different room or switching the cooker on and off and similar, so i'm just thinking the rest of the cases are reactions as well, i just don't know to what exactly.

So I bought a surge protective extension cord and plugged everything in it with no luck. To be on the safe side I tried different circuits around the house - the problem still persisted.

Finally with no more ideas of what to try I decided to go for the big guns and got myself an UPS with the capacity of around 1200W as recommended by one quite competent friend. We were convinced this would fix the problem. It didn't.

So my question is, does anyone have any idea of what could actually be happening here? Also, does it matter that I use an extension cord to plug all the devices to the cord and then this whole system connects to the UPS via the cord as opposed to plugging each device into a separate port? The load indicator shows that the UPS isn’t overloaded.


texts: why is the outside of an electromagnet not magnetic?

texts:
On the  electromagnet (5 Volts DC, built upon a transformer core) setup pictured below , only the core part is magnetic (when powered, it attracts a piece of steel) but not the 2 "wings" outside that are supposed to channel the magnetic flux. Their magnetic force is about 1/10th of the central core

Why is that? Is there a geometry to improve channeling of magnetic flux on the outside of the coil ?


texts: Can a relay for 5.5V be replaced with 3.3V relay on the module?

texts:
I'm planning to change a 5V relay module containing optocoupler and other components with a 3.3V relay. The 5V relay is from Songle, and I'm planning to replace it with relay from Bestep.

Would doing so require me to make any other changes in the module, which contains some resistors and diodes?

The schematic is for 5V relay module


texts: Raspberry Pi Single-channel relay with 6 pins pinout decipher needed

texts:
I've got this single-channel relay for my Raspberry Pi. The relay has 6 pins instead of the usual 3, more over out of the box there was a jumper connecting 2nd and 3rd pin (I'm counting pins from top to bottom starting with 1). This is my first ever interaction with both relay and a Raspberry Pi. Why is there a jumper on the relay? And how to use it?
I've hooked up 1st pin to 5V PWR GPIO on Raspberry Pi, 4th pin to GPIO4 and 6th pin to GND. In given configuration LED on relay board lights up whenever I send GPIO.LOW output on GPIO4 but relay isn't clicking.


texts: How do I realize a transfer function with multiple zeros?

texts:
I designed a compensation function for a control system in Matlab and now I'm trying to figure out how to build it using op-amps. I thought I might be able to use a couple of Sallen-Key amplifier topologies, but I'm not sure if it's possible (my algebra skills are dusty). Alternatively, is there any other topology that can realize this form: $$(As^3 + Bs^2 + Cs + D) / (s)$$

A Sallen-Key filter is as follows:

simulate this circuit – Schematic created using CircuitLab

With transfer function: $$\frac{Z_3 \times Z_4}{(Z_1 \times Z_2) + Z_3 \times (Z_1 + Z_2) + (Z_3 \times Z_4)}$$

My gut tells me that I can put some capacitors in \$Z_1\$ & \$Z_2\$ and resistors as \$Z_3\$ & \$Z_4\$, then re-arrange the equation in such a way that it gets me close to what I want, but I'm having trouble doing the algebra. I will definitely need two-stages with this approach to achieve the 4th order transfer function.

In any case, I would appreciate some help in designing this circuit.


texts: How do alternating Christmas tree lights work?

texts:
I saw these alternating Christmas lights:

The top image has all lights on, the bottom left image has odd-numbered lights on, and the bottom right image has even-numbered lights on.

The LEDS are joined by two enameled wires, and three AA batteries power the lot.

How does the controller turn the odd-numbered lights on and off?


texts: How can I measure the pressure from my strain gauge?

texts:
I bought a strain gauge from RS components, and I want to find out how can I get the pressure from the measured voltage on the strain gauge. I managed to the Wheatstone bridge and supply it with a voltage as Vex.

Based on this document, the manufacturer will provide the conversion formula but on the PDF manual here is what I only found. Can someone help me or supply any reference on how can I compute the pressure?


texts: How to find v through superposition theorem in the following ciruit

texts: What is the voltage V of the attached circuit? Using super position theorem. When i active the 9V source & short 12 V source is the current follows in 20 ohms, 10 ohms. & 4 ohms? Or it only flows to 4 ohms?


texts: multiple peripherals though a single USB type C

texts:
I'm trying to build a TV set-up box composed of several peripherals such as:  computer(raspberry compute module), wireless audio transmitter and a DSP each with various power requirements.  I would like to power them using a single USB Type C connector. Is there any off the shelf solution for this? I'm not familiar with the USB protocol but it seems that the power must be negotiated somehow and I'm wondering how can I do that(i.e. do I need to program it, do I need to create a kind of internal USB hub with USB connectors for each compoenent?).

[0] Power requirements

****Raspbery Compute module***********************************
 3V3 and 1V8.                                                *
 3V3 comes up at exactly the same time or before 1V8         *
 aprox 700mA along with the Lan chip                         *
--------------------------------------------------------------

*****External DSP********
5VDC SMPS aprox 300mA ***
*************************

********Wireless Transmitter ******************************************************
source 3V3 voltage  | min 3.135 V | typ 3.3 V | max 3.4651 V |comment 3.3V ±5%
--------------------------------------------------------------------
source 3V3 active supply current| typ 850 mA | max 1100 mA |comment Design for 1.5 A peak
--------------------------------------------------------------------------------
source 3V3 supply ripple| max 50 mV |comment: Peak to peak
------------------------------------------------------------------------------------
source 1V2 voltage | min 1.14 V | typ 1.2 V | max 1.26 V | comment: 1.2 V ±5%
-----------------------------------------------------------------------------------
source: 1V2 active supply current | typ 165 mA | max 200 mA
------------------------------------------------------------------------------------
source: 1V2 supply ripple| max 25 mV| comment: Peak to peak


texts: PSpice Model Editor Not Giving .dll and .lib Files for VerilogA Module

texts:
I am trying to learn how to import VerilogA Modules into PSpice using the Model Editor. For now I am starting with a simple VerilogA model of a capacitor so I can learn how to use the Model Editor and then eventually get to more complex VerilogA implementations. I have been unsuccessful in using the Model Editor DMI Template Code Generator and I'm unsure what the problem was. Here is the simple Verilog module:
'include "disciplines.vams"
module cap(p,n) ;
    parameter real capacitance = 1n ;
    electrical p, n ;
    analog
        I(p,n) <+ capacitance * ddt(V(p,n)) ;
endmodule

I saved this using notepad as "cap.va" and then used the DMI Template Generator. Here are the steps I did for that:

Part Name - "cap"
Part Type - VerilogA-ADMS
Verilog-A File --> Selected "cap.va" file
XML Folder --> Left as is
Output --> Selected the DLL Location

When I hit the OK button the log file pops up but it ends with a "child process exited abnormally" message and there are no .dll or .lib files in the DLL Location. Here is the resulting "cap.log" file:
Reading json
reading Model Name and Type...
Json read..Logging Model Creation...
reading global and instance params for digital and analog..
Copying common files ..
Replacing the Model Name in C:\Cadence\SPB_17.4\tools\pspice\tclscripts\pspModelCreate\VerilogATemplate\xmls\pspiceVersion.xml
Verilog-A Path       : D:/cap.va
Name of Verilog-A file   : cap.va
Verilog-A Location   : D:/
XMLs Location        : C:\Cadence\SPB_17.4\tools\pspice\tclscripts\pspModelCreate\VerilogA-ADMS\xmls
Generating Files
C:\Cadence\SPB_17.4\tools\pspice\tclscripts\pspModelCreate\VerilogATemplate/admsXml.exe -I D:/ D:/cap.va -e D:/ORCAD_PARTS/cap/code/pspiceVersion.xml -e C:\Cadence\SPB_17.4\tools\pspice\tclscripts\pspModelCreate\VerilogA-ADMS\xmls/pspice.lib.xml
[info...] admsXml-2.3.0 (1186M) Aug  4 2010 10:25:25
child process exited abnormally

Did I end up doing something wrong or is there something wrong with the VerilogA File?


texts: How do I calculate how much solar power I need for a system?

texts:
I'm prototyping an autonomous remote system which is composed of the following components:

Arduino Leonardo
Solar Charger Shield V2
3W Solar Panel
Lithium Ion polymer Battery pack - 6A

The system will be located near Narbonne where the insolation varies from 1.18 (winter) up to 6.44 kWh/m²/day (summer).

Questions:

How do I make sure the system will be able to operate continuously?
Which formula(s) can I use to guesstimate?


texts: Why does my AY-3-8910 sound so distorted?

texts:
I'm building a circuit driven by an Arduino UNO that controls a AY-3-8910 programmable sound generator.

The AY has three pins labeled Channel A, B and C.  Each output is an independent sound channel.

I am piping the audio through an LM386 which then drives a small PC speaker.

When I run a single channel, it sounds pretty good.  But each time I mix another channel, things start getting really distorted.

I've built this on a breadboard in the past and it sounded great so I don't know what I'm doing wrong this time.

Below is a crude schematic of my circuit.  I didn't draw the LM386 because it's the same with or without it and I never used it before.

Any ideas how I can cleanly mix these signals?  I don't remember doing anything in the past other than literally connecting all three channels together.

I can provide more schematics and/or videos or pictures too.  This is driving me nuts.  So I'm hoping someone out there has worked with this sound generator in the past that can provide some insight.

Thanks.

simulate this circuit – Schematic created using CircuitLab


texts:
I was wondering if there is a hybrid between the serial and parallel EEPROM's? What I mean is, is there an EEPROM that can be written to over I2C and then once it is setup can be controlled with some hardware Address pins, like how parallel EEPROM's change there output pin states when their address pins change.

Just some background, I am, for fun, building a little 4 x 7 segment led display. I wanted to just have the arduino send the current time once a minute to the eeprom over I2C, where then an external clock and counter change the eeproms addresses to multiplex the display.


texts:
I am trying to simulate ICM7555 timer on proteus schematics. However, after following the datasheet for Astable operation, I don't see any results on the analog analyzer. Can anyone tell me what I am doing wrong?

PS - new to electrical engineering

also, I think that the problem can be in the simulation of proteus since it was saying before that simulation model is missing. I downloaded this footprint recently from the internet.


texts:
I'm setting up my led cube and wanted to test with a few extra leds before hooking up my time intensive cube. FYI I am a computer scientist not an electrical engineer. I would like to make sure my numbers look correct.

LED SPECS:
Forward Voltage (V) : 3.2 ~ 3.8
Reverse Current (uA) : <=30
Forward Current : 30mA
Max Peak Forward Current : 75mA
Reverse Voltage : 5~6V

POWER SUPPLY SPECS:
5v  3.8A

I connected one led to the supply with with two 100ohm resisters all in series. When I measured the current I got 9.4mA and for voltage across the resistor I got 3.14v

Do I need less or more resistance or is it ok? The spec sheet says 30mA forward voltage so I would assume I could stick with 100hm per resister.


texts: Good book for non-beginner firmware development

texts:
I do a lot of firmware work at my job, but I'm looking for more advanced books on the topic.  Things not like the basics of "what is an interrupt".  I'm reading the O'Reilly book on embedded systems development which is OK, but not advanced enough.  For instance, its rare for books to discuss things like Flash pages (which can be really useful), how to put a section of code in a specific area of memory.

Perhaps something with some tips and tricks.  I do primarily PIC programming.


texts: Josephson Junctions: Difference between X and X enclosed by box (☒), in circuit diagrams?

texts: In circuit diagrams, Josephson Junctions are sometimes given as an X and sometimes as an X with a box around it ☒. What is the difference?


texts:
I've been working on a simple power bank project that's been built using Li-ion batteries, the batteries are rated 3.3 V.

I've implemented a charge controller which can efficiently charge the power bank batteries from USB charger without any issues.

The problem here is that I want to create dual output 5 Volts slots 1 and 2 amperes respectively for charging external devices. How can I do that efficiently ?
I've surfed the internet and found articles and answers about current limiting using resistors and/or transistors but i'm so confused now.

Thanks so much.


texts: How to make a circuit to trigger a relay once the cell voltage reaches 83.5V DC

texts:
I need to make a circuit that will trigger a normally closed relay to cut a signal.
I have a 12V power supply DC
I need it to trigger once the main system reaches 83.5V DC
Needs to be powered by the 12V DC system.

EDIT: Thank for all the great input on my question thank you all so much! i did think about it some more. I have made a regenerative system but it doesn't know how to cut the Regen once max voltage of 83V is reached the system has a 12V step down that uses a common ground from my battery pack. so there is a 12V+ and a 63V-84V -(neg) common. if the battery pack is at 83.0V(safety) i need to trigger a relay that would be normally closed, and keep it triggered until the voltage is below 83.0V(once voltage is reached again re trigger) so the regeneration can not function. My battery max voltage is 84V but my Regen system can output 90V. all this is doing is metering voltage, it needs to be made with no adjustments, tolerance is permissible if pack will not go over 84VMax. Or maybe with adjustment?


texts: Solar RC Airplane – Trouble with Mini Solar Lipo Charger

texts:
I'm in the process of building a solar powered remote controlled airplane. My general idea was that I have 5V from the solar panels powering the receiver, the ESC, two servos and a brushless motor. If the voltage of the solar cells falls beneeth 3.7V, my 1S-LiPo-battery takes over.

For this I found the «Mini Solar/Lipo Charger v1.0» from Elecrow which apparently exactly does the trick of being a switch and at the same time charging the LiPo with the power from the solar cell input.

So before I start to tab all solar panels I wanted to do a test run and see if all my chosen components get enough power with the 3.7V-LiPo.

After I hooked everything together and as a last step plugged in the LiPo at the LiPo-socket on the Elecrow-Board, the board smoked :-(

I don't know exactly where to start to find out what I'm doing wrong.

I attached a picture of my setup (without the solar cells).

Thank you very much for you help!


texts: In closed loop configuration of op-amp,what happens to open loop gain?

texts:
Open loop gain comes from the internal circuit of op-amp which is very high, but in closed loop configuration the gain is limited by the feedback resistance. So my question is:

What happens to open loop gain which should be there, because we haven't disturbed the internal circuit of op-amp after closing the loop around?
If open loop gain still exists, then how can the two different voltages exist on same output node (one due to open loop and other due to closed loop)?


texts: Proteus/Ares 8 - why does adding ground plane not make ground links disappear?

texts:
I have a 2 layer through hole board I am laying out with lots of ground pins showing as ratsnest routing links. However, when I add the reverse copper as a ground plane using:
tools/power plane generator
with net (GND=POWER)
and layer (Bottom Copper)
I see only a blue outline near the edge of the board (the ground plane I assume?) and the GND rats nest remains.

What am I doing wrong?


texts: Common cc/cv charger for same volt and different capacity

texts: Can I use Li.ion 7.4v 5400mah in place of built in Li.ion 7.4v 1400mah battery of a portable DVD player and use same old charger?


texts: Increase Rise and Fall Time of this Schematic

texts:
The following cirucit converts a 3.3V PWM signal into a +-12V PWM signal and works as expected. I want to increase the rise and fall time of the ouput signal to approx 2us. How can this be done?

Update:

How about an output filter?

BTW - The ouput wire is approx. 7-8 meters long.


texts: Experiment with transformer: meaning of some physical quantities

texts:
I'm doing some experiments with a transformer, measuring some physical quantities.

  First I did an experiment with the transformer in open-circuit. I determined the voltages and currents on both primary and secondary winding.

I know the power factor measures the ratio between active power and apparent power (it was in fact this way that I computed it).

However, what does it exactly mean? Specially in open-circuit? Is it the percentage of power that doesn't get "lost"?

I know that if I had a load connected it would be the percentage of power delivered to the load. But this way I'm not sure.

Then I computed the parameters of the transformer G_m and B_m. I converted them to per-unit values. Does this have any physical significance? Because B_m is more close to 1 than G_m. Does just mean that the inductor parameter is more relevant than the resistor one?

  Second I did an experiment with the transformer in short-circuit. I determined the voltages and currents on both primary and secondary winding.

I have the same question about the power factor, what does it mean here? Power delivered to a short-circuit?

Then I computed the parameters of the transformer R_t and X_t. Again, converted them to per-unit values. I have the exactly same questions as before.

  Third, I experimented with a load, same thing as before.

Now the power factor must mean the percentage of power delivered to the load, right?

Thanks in advance!

EDIT: Transformer model (valid in pu values).


texts: Where does the SWD header in this schematic connect to the microcontroller?

texts:
Edit: better quality schematic

I'm designing a PCB that includes the STM32f103C8T6 and I want to program it via SWD (with the ST-Link v2 USB connector). I'm using the Blue Pill dev board schematic (pictured above) as a reference, but it's not clear if the SWDIO and SWDCLK pins in the SWD header are directly connected to the SWIO and SWCLK pins or not. Are they?