texts: COVID-19 Human to Human 'Proximity' Logger

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In the midst of the Corona Pandemic we are looking to develop a wearable sensor that when within approximately 2m of another (of the same type) of wearable sensor will log an event.

The ideal would be a low cost and very low power. It must work without line of sight since the sensor can be in your pocket etc. I've looked at all sorts of proximity sensors and none seem to be able to do the job.

My only solution I could come up with is a sub Ghz RF transceiver that polls (twice every second) and is in receive mode for the rest of the time and when a message is received an ACK is sent. The output power will be set very low (0 dbm) without an antenna so should get around 1.5 to 2.5 m range irrespective of a human body that is in between sender and receiver (If I go with my intuition).

Problem is that lowest RX current is around 7mA which means on a 1000mA battery will last less than a week.

Has any body done anything similar or have any advise on maybe another type of technology I can use?

Location is not important and it is most likely going to be indoor.

Any advise will be highly appreciated


texts: What are the functions of these components in this 15V 500mA power supply?

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Hello guys, I want to know what is purpose of the transistor T3 (BC547B) in this circuit. I understand it provides base current to the series pass transistor T5 (2N3055). Also I want to know:

What is the function of transistor T4 (BC557B) and  T2 (BC547B) and T1 (BC547B)?
Is D1 (1W, 15V) a zener diode?

What is BZ1 (24V) in this schematic?


texts:
Would this work as a constant current load since I don't have a high power pot?
Is there a better way to do it?

simulate this circuit – Schematic created using CircuitLab


texts: What is traffic generator (while using Xilinx Memory Interface Generator)

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I am trying to use the Memory controller Block in my Xilinx Spartan 6 FPGA to set up an interface with LPDDR memory. I read the MCB User guide, and I am quite clear about how it works, and how I would be able to use it. So, I generated a mcb controller using the Xilinx Core generator (using the MIG tool), but now I am stuck.

In the Spartan-6 FPGA Memory Interface solutions user guide (UG41) there is a constant reference to traffic generator. I am trying to understand what it is (this is a term I am hearing for the first time), but with no luck.

After 2 hours of googling, the closest answer I got was on this link. After a lot of guessing, I think traffic generator is an interface between the Memory Controller and the User logic, which defines how data is supposed to be exchanged between. But then it raises more questions :

What exactly does it define?
How do I define one on my own?
Is it necessary for interfacing with the memory controller?

There is very little given about traffic generator in the user guide, and I am not able to find any answers. Any help is appreciated.


texts: How can I simulate a bridged output of a speaker at 8 ohms?

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Following on from my previous post on a single 5V rail amplifier, I'm trying to simulate a bridged output op amp set up to drive an 8 0hm load.

One of the solutions was:

  Use a bridge output. This is two power amps with the signal inverted between the two. One drives one side of the speaker high while the other drives the other side of the speaker low the same amount at the same time.

Input is a 400mV P-P Sinusoid
Expecting a 10V P-P Output voltage swing

There wasn't any information I could find on google, so I attempted a design following the quote above (R5 is the simulated speaker load):

The output of it is the following: (Note: The top graph's reference node is the output of the inverting amplifier)

However, if I change R5 to 8ohms, the impedance of a normal speaker, I get the following output:

Is my understanding of a bridged output incorrect here? If not, why can't I simulate the correct circuit?


texts: Multiplexing with or without transistors

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I'm doing something in where I need to multiplex 6 7-segment displays. About doing it, I found things like this:

And things in where the same thing is done without the transistors, just by connecting the cathodes directly to pins of the microcontroller. What's the difference? When should I need the transistors? Is it because the microcontroller couldn't handle current for all the LEDs?

I'm using an Arduino with an ATMEGA328, if that's needed for something.


texts:
I am using an Renesas RL78 and SPI to communicated with an SD card. I have the driver working using the single command Baudrate of 400kBaud when sending both commands and data.

Of course, this is very slow for data transfer, so I have implemented a method to switch the Baudrate to 4MBaud when transmitting data.

I can see a data response from the SD card but it is always incorrect - I'm expecting to see 0xFE and I'm getting 0xFC back. To test what was causing this, I tried changing my set_spi_baudrate() method to disable and re-enable the SPI channel (allowing the change) but not to actually change the baudrate from the slower speed. It seems the act of enabling and disabling the SPI channel is causing the behaviour.

Does anyone have any idea on how to properly switch Baudrates dynamically in this device?


texts: Identify the white 4 pin part of this board

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My touch screen monitors USB 2.0 Type B port is damaged. I tried to find a replacement but I don't know how to find one. So now I'm trying to construct one.

I've found a few boards that have the USB 2.0 port on a board. They don't however have the four pin white connector that the original cable plugs into.

What is that four pin connector called?

Also, what would this kind of pcb be called?


texts:
This question is related to this question: udn2981-maximum-output-current-too-less.

In the UDN2981 datasheet, the picture below shows the maximum current (page 14, bottom left picture).

Since if I would would use 8 mosfets/transistors to switch, I can get 200 mA per pin (using e.g. a 2N7000 per pin), and an UDN2981 can 'only' handle 400 mA in total, and even less if multiple pins are used (like with 8 pins, only about 120/8 = 15 mA (at 100% duty cycle).

Why is there a relation between the pins? Is it related to heat?


texts:
I am having trouble understanding how to build a truth table given a circuit or expression. I believe I have the expression ones down but I can not figure out the ones where the circuit is given to us. So I will upload the picture of the circuit here is what I believe is the truth table. However I dont understand how to tell which one has an output.

The first and gate has X1, NotX2, X3

Second and gate has X1not, X2, X3

So:

So re traced my steps So on the red one from AND to OR would be X1*X2'*X3
On the blue line from AND to OR X1'*X2'X3

So f=X1*X2'*X3 + X1'*X2'*X3

Is there a trick to these, or where is a good place to learn this? Way my professor teaches does not make a ton of sense to me.

Thanks in advance.


texts: Something better than an H-bridge to drive motor?

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Is there something better than an H-bridge to drive two motors using the ATmega8 with a 7V power supply?

My teacher said the H-bridge overheats and is bad. Is there a better solution? For instance: creating my own BJT circuit?


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I want to install 3x 20W LEDs on a 1.5m x 4cm x 3mm aluminum bar.
Is the bar large enough for 60W ?

Known:
From literature I have found that about 2/3 of LED's power is converted into heat.
Using thermal paste
The heat sink will be mounted 10 cm above water (500L aquarium) - I think this will massively improve the heat dissipation.


texts: 100s of devices on SPI bus with daisy chaining - theoretically possible but who's done it?

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I need to control 512 knobs digitally using 128 digital potentiometers. The AD5204 supports daisy-chaining but what do I need to be careful of when interfacing this with a ATmega328P?

I plan to split this across 8 chip select lines with 16 devices on each chip select (CS) line. It looks like the digital out is powered by the device so to me it looks like it will work.

What am I missing?

Will the atMega drive so many devices, if not how should I amplify the bus?
The CS will be held low for a command of 176 bit for the commands to get to the last in the chain.
Noise considerations - erm, low pass filters and load resisters?


texts: How to make an LED turn on if the input voltage is below 5V?

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First of all I'm  new to electronics. I am an automation engineer and a robotics integrator, so pretty specialized. Please be clear! Thanks all.
Context: PLC special circuit needs to stay at 5V otherwise the PLCs will face a potentially fatal problem (old tech.)
I need to make little circuit that I will use to visually minitor the voltage on some old PLCs. I have an input of 5V available to use for the circuit (5V coming from PLC.)
Simply just turns off the LED when ~5V are met, and turns ON the LED when under 5V (~4.7V) threshold.


texts:
I'm intending to buy a lab power supply, high likely a .. I'm thinking about a Korad KA3005D (see picture below).

It does not come with cables for the Red + and Black - terminals, and I (also) would like to have a plug to use power not only via the (4mm) banana plugs, but also by screwing it to the same terminal. I'm intending to create a cable myself.

My questions:

For connecting the power cables it can be either connected to the banana plug or to the screw. On the cable, a half round iron 'circle' is needed … how is such half round thing called to connect to it? I mean the 'plug' that needs to be added to the Red + and Black - terminals.
What is the (inner) diameter (if it is standard)?


texts: I recently had an assignment where I had to use open stub series tuning to find a way to maximize power delivered to the load from the generator. I understand that power delivered to the load is maximized when the input resistance is equal to the generator resistance and that reactance is zero. I know that when you are doing open stub series tuning you choose a length l for the stub such that it cancels any reactance at the position of the series open stub. What I don't understand is how I would calculate this length analytically (in this assignment we had to do it analytically without a smith chart). Below I have included a picture of the solution our teacher provided to us. I don't understand how he took the input impedance equation and arrived to an equation that was dependent on cotangent.


texts: What actually is the load capacitance of a quartz crystal?

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I'm having hard time understanding the principles of piezoelectric crystal oscillators.

I've found this picture:

I understand that "load capacitance" is something you have to connect to a crystal. I understand that this basically means having to connect an external capacitor in parallel to the crystal. I also realize the basic principle of piezoelectricity; voltage/electric field across the crystal will physically deform the crystal, and the deformation also creates an electric field. So why is load capacitance needed? And if it's always needed and it's fixed, why is it not included in the crystal package? Is it because we need to sometimes operate it in series mode instead? In the equivalent circuit diagram, there is already a capacitance, Cp, parallel to the series resonant arm. Why do we need even more capacitance in parallel to that?

In the picture I provided, there is a curve showing impedance of the crystal with respect to frequency. Why isn't the load capacitance showing in the formulae for the resonant frequencies?


texts: Why does RAM (any type) access time decrease so slowly?

texts:
This article shows that DDR4 SDRAM has approximately 8x more bandwidth DDR1 SDRAM. But the time from setting the column address to when the data is available has only decreased by 10% (13.5ns).
A quick search shows that the access time of the fastest async. SRAM (18 years old) is 7ns.
Why has SDRAM access time decreased so slowly? Is the reason economic, technological, or fundamental?


texts: What standards or conventions are there for BOM line items for non-refdes parts?

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Some designs have parts that may lack a reference designator because they never appear on the schematic.  Examples include:

Battery holders
PCB-mounted (soldered on) fasteners such as solder-nuts
IC sockets
Jumper wires on a single sided board (if they haven't been backannotated to the schematic, that is)
Plugin modules such as keypads and LCD modules (if they haven't been given a schematic symbol)
Heatsinks

Are there any standards or conventions for how these are listed in a Bill of Materials for a circuit board?


texts: Voltage at Collector of NPN less than Minimum allowed for High

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I have connected the collector of a NPN BJT (DTC144EE) to the Power_ON pin of my lte module (HL7588).

The pin is internally pulled up by a 100k resistor to 1.8V. The module is powered on by driving the PWR_ON signal low (I send 1.8V from my controller to the base of U$1).

However, I ran a simulation in TINA and am seeing .85V at the collector (when I want device in OFF state) when the minimum of a a high signal should be 1.33V.

On U4s Data sheet:

Any ideas on what is going on here? This is the transistor Sierra recommends for both Power_on and Reset signals so it is confusing.


texts: Is there such a thing as a pin (or pogo pin) clamp for testing?

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I'm an amateur tinkerer of electronic components, and was wondering if a product like I'm about to describe exists for testing components.

Say you have an arduino pro mini board. You want to access the FTDI pins for flashing, but ultimately are going not to solder those pins to something else.  As I know it now, I have to solder header pins to it to connect the FTDI programmer, then I after I'm done with all of that I can use those pins to solder it to whatever it needs to be a part of.  But say I just want to program the board without soldering header pins, so I could reuse it in an application where those original pins wouldn't need to be connected.  Is there some sort of clamp or something that has a bunch of pogo pins (or whatever) that would make contact with the board, then have exposed pins on the top where I could plug the programmer in? It would be the equivalent of an IC test clip, but for boards with pins.

I can't seem to find it on Google.  Does this exist, and if not, why not?!


texts: Measuring pulse durations with microsecond precision or better

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Problem

I'll be receiving pulses and want to know the relative times of pulse start/end with microsecond precision (or better).

Pulse characteristics:

pulse frequency: probably 1Hz to 10Hz
pulse length: 1μs to 200ms
pulse spacing: >10μs between consecutive pulses

I want to measure (ideally) the durations of HIGH/LOW levels, or otherwise absolute times of edges (relative to internal clock) from which I can then calculate the durations.  I want durations/timestamps to have microsecond precision or better.  100ns would be great!

My ideal output data would be a series of sequential HIGH/LOW durations for example:

HIGH for 205μs
LOW for 134μs
HIGH for 18μs
...

This is just a hobby project, so if I mess up measurement of 1% of events then I can just drop those values.  No mission-critical requirements or angry customers :)

I figure that I can use some STM32 MCU, with timer in "input" configuration.
Then have it store timestamps every time an input pin raises or lowers.

The "filtering" that the STM32 timers can perform will be great for debouncing and noise rejection too.

The times of pulse rises/falls need to be precise to the microsecond or better, but there are no other tight realtime constraints.  If it takes an extra 500ms after an edge, before these timestamps get transmitted, that's fine.

Initial solution idea

Ok, not my first solution (that was an oscillator plus a huge pile of 7474+7476 for clock counting and edge-triggered buffering of the clock value)...

simulate this circuit – Schematic created using CircuitLab

Question

Is the solution really just as simple as:

connect my signal to a timer-input pin on the STM32
configure a 32-bit timer as input (so timer's value is stored on an input edge transition) and with appropriate filtering
configure an interrupt to take the stored timer value after an edge and put the value into a queue
process that queue during idle-time, since there's no realtime requirements on getting the data

The input signal will be the output of a transimpedance amplifier, driven by a filtered photodiode.
Signal-to-noise is expected to be pretty good, at least 30dBV.

I'm planning to use STM32G431KBT6 just because it's easily available and I can hand-solder it.  I'm not strongly tied to using this MCU part though.

Time wrap-around could also be an issue if counting at e.g. 16MHz with 16-bit timer.  I guess I can just slave another 16-bit timer to it and use the other one to count wraparounds, effectively giving me a 32-bit timestamp when reading both timers?  Although provided that, at most, only one wraparound event occurs between two timestamps (in the case of a 32-bit timer), unsigned integer subtraction should give me the interval correctly anyway.

Extra thoughts

Since the timer input is filtered, I'm thinking to eliminate the Schmitt buffer/inverter.

Also I'm wondering whether to use the STM32's internal comparators so I have a bit of extra fine tuning for edge thresholds and hysteresis, and connect the comparator output to the timer input, so that edge transitions on the comparator output drive clock inputs, allowing me to record precise timestamps of when edge-transitions occurred.  I'd "tune" the thresholds by connecting DAC output to other comparator input.

Some STM32 parts have opamps built-in too, which I could maybe use for the transimpedance amplifier.  The slew rate is only 0.7V/μs as far as I've seen, but that might be fast enough, I don't have a hard figure yet for what bandwidth I need.

Oh wait, the GaN STM32G-series parts have much faster opamps that are totally suitable for what I want to do!

I also considered using the analog watchdog, but STM32L0: Fast processing of an analog sinusoidal signal suggests that it will be too slow for microsecond-resolution timing and it's a bit of a hack to use it for this.


texts: Capacitive Touch Pad Design with TTP224 ic

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I am designing circular capacitive touch pads of Dia:20mm driving from TTP224 IC on my PCB. There will be 2mm glass panel above Touch pads. My PCB contains other circuits like Arduino, Antenna bands and driving LED's as well along with these touch pads. These 4 touch pads are at different positions (They are not side by side).

Will the tracks (Track width:10 mils) from touch pads to the TTP224 IC when touched will detect the touch or only touch pads will detect the touch? (I don't want tracks to detect the touch).

Can I place common copper ground pour on PCB's opposite layer of that of touch pads?

Can I place Antenna bands (of Bluetooth/WiFi) on PCB's opposite layer of that of touch pads?

Can I place any other IC's or components (Like TTP224, RC's etc.) on PCB's opposite layer of that of touch pads?

What maximum diameter I can take as touch pads?


texts: How to identify LED markers by modulating their brightness?

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For a project of mine I need to use infrared LED markers to identify locations of points in space with stereovision algorithms and multiple IR cameras. I also need each LED marker to have a unique recognizable ID, which is my current problem.

My thought was to have each LED flash between two states of brightness (is this possible?) in a recognizable sequence but still be bright enough to track in the lower brightness state.

I don't know how to implement this or really where to start looking.  I am a programmer but have never worked with actual circuits before. Can you help me get started?


texts: Is current pushed through the circuit or taken by the circuit?

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I am not an electrical engineer so my concept about the practical side of ohm's law is very flimsy. What I am going to ask may sound childish but please try to explain as best as possible.

When you put let's say two things in series; an led (let's assume 150ohm) and a small 100ohm resistor, then you attach it to eight(8) 1.5v batteries, the current flowing through the circuit can be calculated by the ohms law as follows:

I = V/R = 12/250 = 0.048 amperes

A lot of internet articles say "provide" a certain current to the circuit. Does it mean that let's say if for the above circuit if you had to run 1 ampere through it, you will have to ramp up the voltage to 250?

My understanding that if the supply has no current limitation, then the current flowing through a circuit will be as per the Ohm's law. Otherwise you have to play with voltage to get a certain current flow through the circuit.

I mean can you actually force a certain current through a circuit without playing with voltage or the resistance? Could there be 2 similar voltage supplies but one with higher current than the other?


texts:
I want a simple comparator circuit that lights one LED when voltage is above ~1V and lights the other when below. I'm sure I'm missing a basic concept, but it seems like this circuit should have that effect?
What I'm seeing is that L1 lights well, but when L2 is to be active both are lit dimly.


texts: Gain of a differential amplifier with active load

texts: Can anyone help me to find which is the type for the gain of this differential amplifier for common mode input.I had find that is Acm = 1/(gm3*2*ro5).Can anyone help me if this result is correct and how I can prove it?


texts:
Okay, so I'm new to the whole electricity field and I'm trying to get a handle on something so I apologize for any ignorance displayed here.

I've purchased a new graphics card for my computer and I'm worried that when I'm maxing out it's power need, my PSU (Power Supply) will not be able to output enough power.

I understand that AC wattage going into the computer is going to be higher than DC wattage output as some wattage is lost in the conversion and that all depends on the efficiency of my PSU.

So I bought a P3 KILL A WATT 4400.01 to measure AC wattage going into the PSU.  I have a PSU that, in theory, should output up to 500 watts.  When I stress test the card and look at the AC wattage (Amps X Volts X PF) being pulled, it doesn't go over 450 watts.  However, the AC Volt-Amperes being pulled into the system are over 600 so I'm a little confused/worried.  I know, in theory, that the DC wattage being used/pulled should be lower in the system due the loss in conversion and that the system draws extra AC wattage to meet the DC wattage needs.

So, my question is, should I be looking at the raw AC Volt-Amperes going into the PSU or the actual AC wattage (Volts X Amps X PF) to base what the PSU is actually drawing?


texts: Suitability for using a standard light switch to connect to a micro-controller port

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Could a standard run of the mill Lightswitch like this:

Be used in place of a button like this on a microcontroller project:

I'm not in any way suggesting I'm tapped into the house electricity. Literally curious if these larger switches could be used as substitutes or if there would be some reason like some standard resistances that would impede usage at the lower energy levels (3v/5v) sources one would use when experimenting with micro controllers.

For example could this be awkwardly wired to a GPIO port on a Raspberry Pi or Arduino compatible controller and be expected to function appropriately?


texts:
Need advice:
I have a circuit board that is BMS/PCM for a battery as a protection circuit board. The circuit has an IC and has one MOSFET, transistors, and diodes. I want to know how can I increase or decrease the overall current rating by changing components. What components have the main effect? I know the Ohms law. I know current has a direct relation to volt and resistance. The Mosfet datasheet shows a current of 5 amps.
So can I gain the current change by changing resistors and or I have to look for the IC and the MOSFET too?
How can I change the current ratings?


texts: Why the resistor in this op-amp circuit?

texts:
Here's a circuit diagram for a signal response test circuit from the spec sheet for a HA-5195 op amp and looks like a non-inverting amplifier circuit with a gain of 5, plus the 200Ω resistor between Vout and ground:

It's the canonical (I assume?) non-inverting amplifier circuit with R1 = 400Ω and Rf = 1.6kΩ, plus the resistor I'm asking about.

Can someone explain the purpose of the 200Ω resistor?


texts: hard-wire 4-port usb hub to my car's 12v switched cig outlet

texts:
I would like to hard-wire a 4-port usb hub to my cig outlet. I currently have the hub connected to my power inverter and have to flip a switch to turn on the power. My goal is to do a complete behind-the-dash solution where I don't need to flip a switch. I have clear access to the cig outlet in the dash (I would prefer to cut as little as possible but since I don't smoke I really don't care if I need to hack something). I checked the outlet with my multimeter and confirmed that power is only switched on/off with the ignition which is exactly what I want.

My original thought is to just take apart the hub's power adapter and connect the wiring to the cig outlet. The power adapter is just converting 12v down to 5v anyway so I could just solder the connections to the outlet right? I haven't taken apart the adapter yet, I just wanted some confirmation that my thoughts are correct before I do it. If I'm way off or something, what are some other solutions I could do? It's been a while since I've done anything with electronics so my memory is a bit rusty.


texts: Input voltage limits of AD8495 (thermocouple amplifier) vs supply voltage

texts:
I'm working on an android multigauge for cars based of a pic microcontroller. Some inputs from sensors are not fed by my circuit so after stumbling upon this thread: http://www.microchip.com/forums/m612024.aspx, I had to make some changes to the circuit to be able to respect the fact that an input can't have more voltage then the voltage supply + 0.3V. So this was fixed with a schottky diode array on the input and a tvs diode on the supply line.

But I started to check the specs on other chips on my circuit. The AD8495 on it's datasheet on page 3 calls for an input voltage range of -Vs - 0.2V to +VS - 1.6V. http://www.analog.com/media/en/technical-documentation/data-sheets/AD8494_8495_8496_8497.pdf

Am I correct in thinking that if my circuit is not powered but is grounded (fuse blown or something) and that there is voltage on the inputs (+in to -in) then it's not safe? Thermocouple input voltage is tiny but if Vs is 0V and the input is 30mV, that is more than 0V - 1.6V... And if I want to protect against a wrong connection, let's say someone connects 12V by mistake on the input. Then even if Vs is 5V and if I have diodes protecting the inputs, voltage would be limited to about 5.2V and that would still be above VS - 1.6V...

Am I correctly understanding this? And if so, what would be the proper way to make sure that the input is always at Vs - 1.6V max?


texts: SPI communication between STM32F4 and Rasberry Pi produces garbage

texts:
I trying to make an SPI communication between a RPi (as MASTER) and an STM32F410 (as SLAVE, on a Nucleo board). My PoC is simple, I send 8 bytes from the Rpi and print them out with the UART-over-USB on the Nucleo.
Here is the sending code (in Python) running on the Rasberry Pi:

spi = spidev.SpiDev()
spi.open(0, 0)
spi.max_speed_hz = 8000000
to_send = [1,2,3,4,5,6,7,8]
#spi.writebytes(to_send)
spi.xfer(to_send)

and the receiving code on the STM32:

while(1) {
    memset(buf, 0, BRAIN_COM_BUF_SIZE);
    HAL_SPI_Receive(&hspi5, (uint8_t*)&buf, BRAIN_COM_BUF_SIZE, HAL_MAX_DELAY);
    sprintf((char*) dbg_buffer, "[%d][%d][%d][%d][%d][%d][%d][%d]\r\n", buf[0], buf[1], buf[2], buf[3], buf[4], buf[5], buf[6], buf[7]);
    HAL_UART_Transmit(&huart2, dbg_buffer, strlen((char const*) dbg_buffer), 1000);
}

and my SPI initialization code (generated by CubeMX):

/* SPI5 init function */
void MX_SPI5_Init(void)
{

  hspi5.Instance = SPI5;
  hspi5.Init.Mode = SPI_MODE_SLAVE;
  hspi5.Init.Direction = SPI_DIRECTION_2LINES;
  hspi5.Init.DataSize = SPI_DATASIZE_8BIT;
  hspi5.Init.CLKPolarity = SPI_POLARITY_LOW;
  hspi5.Init.CLKPhase = SPI_PHASE_1EDGE;
  hspi5.Init.NSS = SPI_NSS_SOFT;
  hspi5.Init.FirstBit = SPI_FIRSTBIT_MSB;
  hspi5.Init.TIMode = SPI_TIMODE_DISABLE;
  hspi5.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
  hspi5.Init.CRCPolynomial = 15;
  if (HAL_SPI_Init(&hspi5) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
}

Nothing fancy right? This is a one-to-one only communication but I set and configured the CS pin anyway.
My problem with this code is that it works like, IDK 5% of the time, at most. Rest of the time, I got garbage or even worse, looks like the HAL_SPI_Receive() function got absolutly nothing.

Exemple of current behavior:

I send:
[1][2][3][4][5][6][7][8]
and the STM32 receives:
[0][0][1][1][2][2][3][3]

Any clues and/or help to unlock me will be very useful, thanks!


texts: Does amplitude of FM signal even matter?

texts:
Thinking about FM modulated signals that store information only in frequency so that their amplitude has no effect on the sound, I began to wonder: Does the amplitude even matter in the end?

Well, mathematician would say - "Yes, it does. At 0 amplitude there will be no signal."

But I'm rather asking whether it matters, to the close receiver, if I use 10V or 10kV.

What would happen if I had used the former? Would it turn into Tesla tower? Does higher amplitude have better spread? If yes, how far can one go? (and how close to it then - literally)


texts: Does a low-pass filter average the higher-order frequencies into a "DC offset"?

texts:
In a Pound-Drever-Hall lock, an electronic signal is produced of the form:

We are interested in electronically isolating the term:

My question is: how can we filter to get exactly this term (listed above) without any time-dependent terms?

I know that I can use a bandpass filter around the frequency $\Omega$ will isolate this term:

We don't want the time-dependent terms in the signal and instead we want the imaginary term without frequency:

In the literature, it says that we can combine this signal (using a mixer) with a frequency \$cos(\Omega t)\$ - and a low-pass filter.. but how exactly does this work?

Mixing the signals will produce a term \$cos(\Omega)^2\$. I understand that the average of the signal will have a DC-offset. But if my electronics has a high bandwidth, then this isn't really helping eliminate the time-dependence in these terms, right?

So, in summary, can I use a mixer and a low-pass filter to extract out that particular term? And, if so, how exactly does it work?

Additional information:

(This isn't that important for answering the question, but if you are interested) the function F(omega) is:

And we are interested in isolating this particular term because it produces a good looking "error signal" that looks like this picture:


texts:
I am trying to setup communication between my MCU and slave chip but here are the results from logic analyzer:

I have basic knowledge of SPI protocol but as far as I know, data should be sampled at every clock's phase change. Samples are obviously missed on MISO line. What could possibly go wrong?

Edit 1

My slave device is X-NUCLEO-IDB05A1

Edit 2

Problem solved: MISO signal is stable when I work on laptop's battery... It looked very poor on the oscilloscope - that gave me a hint.


texts: received data through UART showing on 7 segment display using ATmega16

texts:
I am writing code for Atmega16 for receiving data from another PCB through UART. I want to display the data on a 7-segment 4-digit display, but when code for UART and 7-segment is enabled the data is not shown. I measured no power in ATmega16 pin that is connected to the 7-segment display.

When I disable the UART and display a fixed value, for example 62, it does show up on the display. I shared the code below.

#define BAUD RATE 2400

void uart_init(void);

void segment(int value);
void print(int number);

int temp;

/**********************************************************/
/**********************************************************/

char s = 0;

int data;

int frequency = 0;

void USARTInit(uint16_t ubrr_value)
{
    //Set Baud rate
    UBRRL = ubrr_value;
    UBRRH = (ubrr_value >> 8);
    UCSRC = (1 << URSEL) | (1 << UCSZ0) | (1 << UCSZ1); //UCSZ2>0 for 8bit
    UCSRC = (1 << UPM1); // for even parity: UPM1>1, UPM0>0....USBS>0 for stop bit
    UCSRB = (1 << RXEN) | (1 << TXEN) | (1 << RXCIE);
}

char USARTReadChar(void)
{
    //Wait until a data is available
    while (!(UCSRA & (1 << RXC))) {
        //Do nothing
    }
    return UDR;
}

void USARTWriteChar(char data)
{
    while (!(UCSRA & (1 << UDRE))) {
        //Do nothing
    }
    UDR = data;
}

ISR(USART_RXC_vect)
{

    while (!(UCSRA & (1 << RXC)))
        ; //execution will wait till the
            //whole byte packet is received

    data = UDR;
    s++;

    if (data == 0xAA) //0xAA is header byte that is sent from another device
    {
        s = 0;
    }

    else if (s == 3) {

        frequency = data; //byte no 3 is frequency
        segment(frequency);
    }
}

int main(void)
{

    DDRB = 0xff;
    PORTB = 0x00;
    DDRD = ~(1 << 0);
    DDRA = 0x0f;
    PORTA = 0xf0;

    sei();

    USARTInit(207);

    while (1) {

        // frequency=62;
        //segment(frequency);
    }
}

void segment(int value)
{

    temp = value / 1000;

    print(temp); //4th digit print
    PORTA = 0x01;
    _delay_ms(1);

    temp = value / 100;
    temp = temp % 10;
    print(temp); //3rd digit print
    PORTA = 0x02;
    _delay_ms(1);

    temp = value / 10;
    temp = temp % 10;
    print(temp); //2nd digit print
    PORTA = 0x04;
    _delay_ms(1);

    temp = value % 10;
    print(temp); //1st digit print
    PORTA = 0x08;
    _delay_ms(1);
}

void print(int number)
{

    if (number == 0) {
        PORTB = 0x3F;
    } else if (number == 1) {
        PORTB = 0x6;
    } else if (number == 2) {
        PORTB = 0x5B;
    } else if (number == 3) {
        PORTB = 0x4F;
    } else if (number == 4) {
        PORTB = 0x66;
    } else if (number == 5) {
        PORTB = 0x6D;
    } else if (number == 6) {
        PORTB = 0x7D;
    } else if (number == 7) {
        PORTB = 0x7;
    } else if (number == 8) {
        PORTB = 0x7F;
    } else if (number == 9) {
        PORTB = 0x6F;
    } else {
    }
}


texts: Relay controlling another relay - surge noise?

texts:
I'm working on a project that uses Arduino Nano to control 1A relays, which in turn control electrical solenoids in a car.  This is for controlling the HVAC air flows in a dash, so my challenge is to control the vacuum signal solenoids.  The project is built and tests fine on the desk.  Nano controls the 1A signal relays with ULN2803A chip no problem, no hiccups.  But when I connect to my test rig which has the solenoids from the car, the Nano keeps resetting as soon as a car solenoid releases.  It sure looks like voltage surges to me, getting past my filters and overwhelming the LM2940-12 power regulators I'm using. No data to prove that though. The capacitors in the design are all 100V rated.  So, my question is "Is it better to add more filtering (capacitor?) to my voltage supplies, or add individual flyback diodes for each solenoid being controlled? If the answer is "more capacitor", then should I look for higher voltage rating? The solenoids are SOL1 and SOL2 on the right.
Initial search doesn't show this problem of resetting the controller, but did learn some things from the TE paper about relay surge supression.  Depending on the answer from above, I might do some redesign to include a Zener diode, or resistor, for each solenoid control.
I have tried adding a IN5404 (400V, 3A) diode from the general GND to +12V power on the pin 30 side of the 1A control relays.  This caused the ULN2803A to fry an output pin within 2 seconds of that relay activating!


texts: 3 phase BLDC sinusoidal drive using PWM controller and/or DSP?

texts:
My background is mechanical engineering (robotics). I apologize in advance.

I have a sensitive torque ripple (Vibrations) application and would like to use sinusoidal drive to run a 3 phase BLDC motor instead of trapezoidal for low speeds. This is for a speed controller (just inferring torque).

12V motors, 8W peak, estimated 2W Steady state. Unfortunately, I am forced to use the UC1825 pwm controller chip. Can the UC1825 PWM controller output to 6 mosfets (inverter) portion, whereupon it has 3 phase output and 1 for direction?What are comparable sinusoidal drive chips?

Datasheet, UC1825: http://www.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=uc1825&fileType=pdf

Alos, if I could implement this using DSP inside an fpga, would I still need a pwm controller (UC1825) or just an 3-phase inverter ?

Thanks!


texts: What resistors do I need for a simple LDR triggered h-bridge?

texts:
I am attempting to build this circuit: https://www.instructables.com/id/H-Bridge-on-a-Breadboard/
But instead of switches, I want ldr s like this circuit:
https://www.instructables.com/id/Simple-Easy-Diy-Light-Following-Robot-Without-Micr/
Both of these projects share many of the same parts so one would think this would be simple but it isn t (for me). I am using 9v from 6aaa batteries and the 2222 transistors and ldr s listed. I have a feeling my ignorance of ohms law is to blame here or my limited grasp on how to decypher a circuit diagram. I am willing to learn if you are willing to teach. "googling it" hasn t gotten me far.


texts: Is it good practice to substitute a resistor by parallel and series-ing them?

texts:
In our electronics (I) lab they told us to never use resistors in parallel or series and choose a value near your calculations. but never explained why.
Is it ok to just buy the range of 1ohm to 1M and use them to get the resistance I want?

I'm starting to build a guitar amplifier. while buying the parts I may end up with lots of spares.

thanks


texts:
I bought a power mosfet(IRF3205) and tried to switch but mosfet is not behaving as I expected when gate pin is triggered it doesnt change its position.

Below is how my schematic looks like, I could not find problem.
Any help is appreciated.

simulate this circuit – Schematic created using CircuitLab


texts: Why can't you just average ADC samples to get more resolution from an ADC?

texts:
I'm trying to get more than 10 bits of precision from my Arduino ADC but I can't really figure out the theory behind it. An often quoted Atmel Application note (http://www.atmel.com/Images/doc8003.pdf) says that

  It is important to remember that normal averaging does not increase the resolution of
  the conversion. Decimation, or Interpolation, is the averaging method, which
  combined with oversampling, which increases the resolution

Then what they propose for 'Decimation' is moving the decimal point. Which amounts to halving the binary reading for every place you move it so you might as well divide the base 10 value by 2 or 4 or 8 or what have you. Am I understanding decimation wrong?


texts: Why are there resistors on the input of this regulator?

texts:
I am looking at an older circuit, and I was wondering why the designer added these two resistors in series with the input voltage of this 5 V regulator. The regulator would be powering a system that pulls 30 mA maximum.
I think I had seen that some people add resistors to try to dissipate heat, but the specified resistors are 1/4 W 0805 resistors. Is that really what they are for?
The regulator is MCP1703-5002E/DB (datasheet).


texts: Character '0' used but not declared for type std_logic_vector??? (Algorithm state machine)

texts:
After adding the counter to my VHDL code am getting the following error:
Error (10316): VHDL error at ASM.vhd(31): character ''0'' used but not declared for type "std_logic_vector"
Thank you

Code:

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

entity ASM is
port(clk, rst, A, B,DOOR: in std_logic;
    Z:buffer std_logic_vector(1 downto 0));
end ASM;

architecture asm1 of ASM is

type t_state is(T0,T1,T2,T3,T4,T5);
signal count:std_logic_vector(2 downto 0);
signal next_state:t_state;
signal current_state:t_state:=T0;
signal tempz:std_logic_vector(1 downto 0):= (others => '0');

begin
clock:process(clk,rst)
begin
    if(rst='1')then
        current_state<=T0;
    elsif(clk'event and clk='1') then
        current_state<=next_state;
    end if;

end process;

next_state_decoder:process(current_state,A,B,DOOR,count)
begin
count<='0';
case current_state is
    when T0=> if(A='0')and(B='0') then
                   count<= count+'1';
                    if(counter_out = 5) then
                        next_state<=T1;
                    end if;
                else
                    next_state<=T0;
                end if;

    when T1=>if(A='1')and(B='0')then
                    count<= count+'1';
                    if(counter_out =  5) then
                        next_state<=T2;
                    end if;
                else
                    next_state<=T0;
                end if;

    when T2=>if(A='1')and(B='1')then
                    count<= count+'1';
                    if(counter_out = 5 ) then
                        next_state<=T3;
                    end if;
                else
                    next_state<=T4;
                end if;

    when T3=> if(DOOR='0')then
                 next_state<=T0;
                 else
                 next_state<=T3;
                 end if;

    when T4=>if(A='0')and(B='1')then
                    count<= count+'1';
                    if(counter_out = 5 ) then
                        next_state<=T5;
                    end if;
                else
                next_state<=T4;
                end if;

    when T5=> if(DOOR='1')then
                next_state<=T0;
                else
                next_state<=T4;
                end if;

    when others=> NULL;

  end case;
end process;

output_decoder:process(clk,A,B,current_state,DOOR)
begin
if(clk'event and clk='1') then
case(current_state) is
    when T0=>tempz<="00";

    when T1=>tempz<="00";

    when T2=>tempz<="00";

    when T3=>tempz<="10";

    when T4=>tempz<="00";

    when T5=>tempz<="11";

    when others=> null;

end case;
end if;
end process;
Z<=tempz;
end asm1;


texts: Does SysTick_Handler() have to be in main file?

texts:
Does the CMSIS SysTick_Handler() have to be placed in the main file (i.e. same file where it is configured)?

If not, how would I go about placing it elsewhere? Is it just a matter of defining the function in another .cpp file, and including "LPC17xx.h"?


texts: How to model a physical channel using verilog?

texts:
I don't have access to high speed transceivers FPGA. So i wish to model the channel of high speed transceivers which is not error free so that i can test my codes if they are working fine or not.
Is there any way to model a physical channel using verilog.


texts:
I have taken an old project from PCAD and loaded it into Altium and it works great. Now in the project the same footprint was used for each different component with the same footprint. For example, there are multiple different capacitor values in the project yet the same 0603 footprint was used for all of them. This isn't a problem until I go to generate the BOM and all the capacitors are the same thing because they are the same footprint. If there is an easier way to connect the supplier links to each different capacitor without creating a new footprint for each different value, that would be amazing. Right now I am creating a different footprint of each different cap.

Any help would be amazing! Thanks a ton!


texts: About transistor biasing and coupling capacitors in ICs

texts:
I'm trying to understand how biasing works in ICs. When using discrete transistors we are told to bias them using polarization circuits typically made of voltage dividers. Then ac signal is introduced with coupling capacitors. However, in analog IC textbooks we are told that bias is done with current sources. The problem with this, is that I cannot understand how DC voltages are set in this scenario, and why are ac signal sources connected directly without coupling capacitors.

For example, in the circuit shown in the picture below. I assume that Rd is supposed to represent a current source that forces ID to flow into the transistor, but then how is the DC voltage at the gate set ?
Moreover, why in most analog IC textbooks no coupling capacitors are shown when adding the ac signal source? Are they not used at all in ICs ? How can this be possible ?


texts:
I've been looking around to see if there's a relatively cheap (around £5) accelerometer / tilt sensor in a DIP package for prototyping. Breakout boards exist for the ADXL335 but seem to be comparatively expensive.

Does such a device exist?


texts: How to figure total voltage with two voltage sources in the circuit

texts:
I have some questions about multiple voltage sources while figuring out KVL. Ive included a circuit labs circuit which shows my question more clearly.

https://www.circuitlab.com/circuit/vucqu6/questions-about-multiple-voltage-sources-while-figuring-out/


texts:
An availability of spare electronic components at my home and a project that is due next week has led me to wonder about making a Ruhmkorff coil that can produce good sparks. However, the traditional design demands a mechanical breaker circuit which I think can be easily replaced by a circuit as shown in following figure :

Is the design sufficient or do I need some adjustments to make it work with the available parts ?

These are the parts I currently have:

TIP31C Transistors
Diodes (UF4007)
48k Resistances

I have already wound a ~900 turn coil for the primary coil made of thin enameled copper wire. The classical design states that a capacitor is good for better performance. I don't seem to have one. Is it really necessary? If yes, what rating would you recommend.


texts: How do you do a software reset of the am355x (like on the BeagleBone Black)?

texts: Is there an easier way to do this than setting up a watchdog and waiting? Using only software (no tying a GPIO to the reset pin)?


texts:
I make the imaginary part of \$loop \ gain=0\$ to find phase crossover frequency.

But in one video, the person told that this method can only be applied when Polar plot crosses the real axis and cannot be used when it touches the real axis.

I don't get why he should be right as Imaginary part equated to zero implies the phase is either 0 or pie or point lies in origin then where does touching and crossing came into the difference.

Also, will I consider such point that is if polar plot touches real axis as \${Kmarginal}\$ for calculation of \$Gain \ Margin\$ using formula \$\frac{Kmarginal}{Kgiven}\$?


texts: Does providing a noisy Vpp for a short period of time affect programming an EPROM?

texts:
I have been designing a complex(from my perspective) EPROM Programmer with an ARM-based STM32f103C MCU -actually it's a bluepill board- , I already programmed my EPROM before by hand manually and even had another question here on Electronics stack exchange related to the same EPROM asking about another thing. I don't have any backgrounds in reading datasheets, as I am still in school not yet in college, so I found a statement in the datasheet of my EPROM which I didn't understand and wanted one to help me in it....

My EPROM is a UV "M27C256B-12F1" EPROM, The statement is repeated in Table 7 till Table 10, so I guess it's a very important note.

  VCC must be applied simultaneously with or before VPP and removed simultaneously or after VPP.

This is the datasheet the tables starts in page 5

From my little understanding, I think that this statement says that VCC should be provided before Vpp and removed after Vpp, but what if the Vpp is provided multiple times while Vcc is still HIGH or on ?

For example:

            _______     ______     ____
 VPP:   ___/       \___/      \___/
            ___________________________
 VCC:   ___/

The reason why I ask is because the VPP is gonna be provided through a tactile switch which can provide a noisy output like that: (or me accidentally flipping the switch two times(

   |--- not stable --||-----stable-------|
    __     ______     ____________________
___/  \___/      \___/

And actually when I programmed the EPROM manually I used a switch but only programmed two addresses, now I gonna programmed the full 32-kilo address with a programmer I made and I would like my work and circuit to be clean... and to be sure the EPROM is taking nice wave-forms which won't effect it in the long run.....

In a nutshell, my question is is it bad to provide Vpp multiple times while Vcc is on ?

Thanks.


texts: Why is MATLAB used so much in industry when there's other software that can do a better job?

texts: All the classes I'm taking require the projects to be done in MATLAB when there are times that C++ would be much better to use. One time the professor took three hours to find a transfer function when it would have taken two minutes tops in Maple or Mathematica. I've heard about people using Python but I've never really looked into it.


texts:
Detecting light with an LED
How do I detect light with an LED?


texts:
I use an analog input (AI) reading board with 12 bit resolution and read range +-10V. The board AI reading error is given as +-5mV.

I need select a pressure sensor, one of them gives 0-5V output, the other gives 0-10V, so which is ideal for my board.

Thanks.


texts: band pass filter on solar cell to detect laser

texts:
my target is detecting a laser generated with 1k frequency using a solar cell, i'm using this idea which is using a band pass filter on the solar cell to block the dc sun light and let me detect the laser, the problem is that i'm completely lost for how i would implement this in a circuit

i've calculated the RLC band pass filter to have 3kohm, .22h and .1uf, which is not bad to start with

the solar panel i'm using is Mini Solar Panel 6V/250mA

but as i'm inexperienced in this field i'm kinda lost, so please either gimme answers or simple schematic

bunch of questions :
q1- is the filter going to remove the dc volt coming from the sun and only leaves me with analog signal of 1k frequency ? aka if the sun will gimme 5v and the laser effect will be 20mv then will the filter o/p be +-20mv square/sin wave ?
q2- i'm using microcontroller to read this input so how much current would that produce if i'm using the following schem.., do i need a resistor to limit the current and how would it affect the wave


texts: Why do linear time varying system exhibit frequency conversion

texts:
I am trying to understand the theory behind spectreRF simulations. Specifically, PSS (periodic steady state) and PAC (periodic AC)
The following concept keeps getting mentioned
"After a PSS analysis, the circuit is linearized about a periodic (time varying) operating point
with frequency conversion effects included."
I understand that after a PSS simulation, a periodic (as opposed to static) operating point of the circuit can be defined in the time domain. So, in the time domain, instead of, for example, the gm of some device being constant, the gm changes periodically.
I also understand the concept of frequency conversion, that a single tone input will be a multiple tone output, and that this is the point of PAC analysis
My question is, how do we get from a periodic operating point to frequency conversion? I specifically want the theory.
If you have Cadence login information here is a link
https://support1.cadence.com/tech-pubs/Docs/spectreRFTheory/spectreRFTheory20.1/spectreRFTheory.pdf
Here is a Screenshot from that guide
,


texts: Can't get pins on molex micro-fit 3.0 connector

texts:
I have this molex connector:
https://www.digikey.com/en/products/detail/molex/0430251800/531407
and these pins:
https://www.amazon.com/gp/product/B072KTD2ZJ/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
With 22awg wire. I have followed this video:
https://www.youtube.com/watch?v=NCU86Yxnnac
And I cannot get the pin to click into the connector like the guy in the video does. The pin doesn't slide in all the way despite my applying considerable force (which doesn't seem necessary)
I've never made a molex connector before so I'm completely lost as to what I am doing wrong here.
Any help would be incredibly appreciated!


texts: USB OTG: Possible to perform emulation of slave device on master with drivers recognized?

texts:
I'm not exactly sure if this should be under a separate StackExchange topic altogether (programming maybe?), if it is, please move it and sorry for the inconvenience.

I'm planning to build a device using either a Raspberry Pi A or Radxa board with the aim of emulating a slave device (unified keyboard and mouse) via commands sent by the board (possibly by a slave device to the board? or a network protocol). As I understand from the specifications of the two boards, there are USB OTG ports that allow for acting as a slave device, however from my knowledge, USB OTG only allows a fixed set of functions as a slave device. Is it possible to make the specific USB port I wish to perform emulation from slave-only considering it is an OTG port? Also, how do I handle driver recognition in this case? Where is the firmware embedded for USB OTG?


texts:
I am designing an RF board in Altium where due to the dielectric selected and its thickness, the trace width for a 50 ohm characteristic impedance is thicker than some of the SMD component pads. What is the best method for routing a larger RF trace to a small SMD pad to minimize the impedance mismatch?

I am currently using the teardrop tool to taper the line down gradually to the smaller width (see below)


texts: Is the frequency accuracy of this MAX7373 oscillator within tolerance?

texts:
I'm currently using a Maximum Integrated MAX7375 MEMS 8MHz oscillator (http://www.digikey.ca/product-detail/en/maxim-integrated/MAX7375AXR805-T/MAX7375AXR805-TCT-ND/4967873) as a clock source for a microcontroller project.

While doing some tests on the microcontroller, I noticed that the internal time of the microcontroller was going a little faster than the real world time. For example, when I would set an alarm on the microcontroller for 30 minutes, it would be go off after 29:44. When I would set it for 1 hour, it would go off at 59:28.

I then attempted another timing method within the microcontroller and had the same results. I decided that my 8MHz clock must be going a little faster than 8MHz. I then took the oscillator to the oscilloscope and was able to confirm that my clock was operating at 8.09MHz.

So my question: is this performance typical, or in range for this oscillator? I notice that the data sheet specs the oscillator as 8.00MHz, which seems to suggest that my oscillator is operating at the worst possible rate for its tolerance.

Furthermore, why exactly would this oscillator be performing so poorly? I thought MEMS oscillators were often considered superior than cap/crystal resonators? Thoughts?


texts:
I got this setup for controlling high voltage with PWM through a Mosfet ranging from 0-60v.

Im using the PCA9685 for generating the PWM signals and then the mosfet FQP30N06L for controlling the external voltage. So far I have only tried the current setup with lower voltage (12v) which works fine. But with the Mosfet FQP30N06L I am using the maximum voltage rating is 60v. This might be a problem with 60V since a spike most likely would kill the Mosfet.
So i am considering using another Mosfet. I saw this mosfet IRF3710PBF and wounder if that would be a better pick since it has maximum voltage rating 100v?
Am I correct when I am saying exchanging the FQP30N06L with the IRF3710PBF, connected the same way would be a good pick?
UPDATE:
I just saw as well that the IRF3710PBF has a Gate-Source Threshold at 2v which might mean that IRF3710PBF might not fully switch on. Any other Mosfet suggestion would be great!


texts: Why are the theoretical and measured frequency responses off a low pass filter different?

texts:
The calculated/theoretical value for the cutoff frequency was different to the measured.

What is the reasoning behind this other than measurement errors?

It should be noted that this was a simple RC low pass filter.


texts:
I want to build a resonator that slowly (~3 seconds) decays without a stable oscillation. I've tried using a simple RLC circuit without luck - I've got ~1-2ms decay time at maximum; so, I've turned my attention to active oscillators, particularly to the Wien bridge oscillator shown below.

If I turn the R4 all the way to the right, I get a stable square-wave output; if I turn it to the left, the output shape becomes more and more sinusoidal and at some point it becomes unstable, decaying to silence after some time has passed after an induced by pressing the SW1 button disturbance. If I continue turning the R4 to the left, the decay time decreases; it seems logical, that if I want a decay time around several seconds, then I need to turn the R4 right just up to the point where the oscillation starts.

This solution, however, is impossible to embody in real parts, since even a small change in resistance (due to the temperature change, for example) will put the oscillator in the stable oscillation territory again, which I want to avoid at all costs.

So, my questions are:

How can the Wien bridge oscillator schematic be modified so that it will be slowly decaying without the risk of a stable oscillation?
Is there a better way to build a slowly decaying resonator?

I am looking, if possible, for a purely analog solution without inductors and without "cheating" by using a stable oscillator and a VCA to control the slowly decaying signal amplitude.

simulate this circuit – Schematic created using CircuitLab


texts:
In products such as KNX there are only two wires used to communicate between a potentially large number of devices, and also provide power at the same time. For example in KNX the normal voltage on the bus is 30V, and to transmit a bit the voltage changes +/- 5V, see page 33-36 of http://knx.com.ua/attachments/article/132/KNX-basic_course_full.pdf

What I would like to understand is how such a circuit can be built. What I can see in the linked pdf is after the power supply there is a "choke" which has close to 0 ohm resistance for DC and very high resistance to AC, I understand this prevents the power-supply from overriding the data. But how is such a choke constructed?

Furthermore, I would like to understand how to construct a device that can raise/lower the voltage on the bus by 5-6V without using external power.

I do not have a background in electrical engineering, I studies computer science, and have a basic understanding of resistors, capacitors, inductors, and I would like to be able to model such a circuit, i.e., in ltspice to understand how it works (I am not searching for a working model, my goal is to understand it).


texts:
I was using the simple darlington circuit below as the test circuit.
DC operating point analysis was run on both LTspice and Multisim, with V2 as the manipulating variable and the base voltage of Q2 as the responding variable.
After the experiment, I found out that the result were different for Multisim and LTSpice when V2 is near to zero voltage. Noted that I had modified the BJT model in Multisim to match that in LTspice.
Belows are the result of Multisim and LTspice when V2 was set to 0V and 2V respectively. For 2V, the result matched but for 0V, the result showed huge difference. Any idea causing this issue?
I have also attached the convergence/accuracy parameter lists for LTspice and Multisim.
V2 = 0V

V2 = 2V

Paramater
LTSpice

Multisim

Which one is more accurate? Is there anything I miss?


texts: Difference between equivalent output current & secondary RMS output current for flyback

texts:
What is difference between equivalent output current & secondary RMS output current for flyback?

Assume Vout = 24V, Output power = 50W

If we divide 50W/24V = 2.08A, this is called as equivalent output current (refer image 1)
If we calculate the secondary RMS, the value will be almost 3.97A, this is called as secondary RMS output current (refer image 2)

Refer below for calculation details.

As you can see, if using 1st equation, we can get output power 50W, while if using 2nd equation, we can get output power 96W.

If my amplifier need 4.0A, this 4.0A should be calculated based on equation 1 or equation 2?

If both is correct, does it mean that this 2.1A (50W) can rise maximum to 4A (96W)?

What is the maximum output current can be draw from the output with the same primary peak current?


texts: Can vias and traces conduct electricity on PCB surface?

texts:
I'm currently designing my first PCB, though when I place a microSD reader on the board I get errors in eagle that the area the reader is over is restricted.

I would have thought this would only apply to components on that side of the board itself, but I get errors when I route traces and vias underneath the reader. So is it possible that traces or vias could conduct electricity through the microSD reader (some bare metal may touch the surface) that might possibly touch the PCB's surface?


texts: Understanding solution to op amp in first order circuit

texts:
http://www.scribd.com/doc/33828848/Fundamentals-of-Electric-Circuits-Alexander-Sadiku-Chapter-07-Solution-Manual

Problem 67:

I'm working on a homework assignment and have solved all of the problems successfully except this one, so I checked the above link to see if i couldn't work out my error, but I'm missing it.

When I solved, I saw that it was a follower, so set my V(t) to be 5, and v->INF to be 0, since the cap should be drained by the time the sun explodes. Safe bet. Then I said that the Req for the capacitor at t>0 was 20 kohms, so the time constant is $$20 * 10^3 * 1 * 10^{-6} = 20/1000 = 20 mS$$

Given $$v(t) = V(inf) + [V(0) - V(inf)]e^{t/T}$$
I get $$v(t) = 5e^{-50t}$$

The solution is using Kirchoff's Current Law to find ... something? it also multiplies by the unit step function for reasons I fail to comprehend...

What am I missing?


texts: Is it possilbe to make up some sort of circuit that would allow you to vary the Ah provided by a battery?

texts:
I suspect the answer to this question - "Is it possible to make up some sort of circuit that would allow you to vary the Ah provided by a battery?" - is "NO, Not Possible" but here goes.

I want to test a device with varying Amp Hours from a rechargeable battery.

For example, I have a fully charged 4.5Ah battery but I want to make it look like it only has 2Ah or 1.5Ah or some other value under 4.5Ah - is that even possible? I'd recharge the battery before each test.

In effect, I want to limit the time the device would operate before the battery was exhausted by altering the Ah of the battery.

This is sort of like using a timer to control the time but that does not meet my requirements. I want the device to operate until the battery is exhausted and I'd like to determine times vs Ah so that I can substitute a battery with an appropriate Ah rating for the approximate time I want the device to operate.

If this is possible, can you give me at least an idea of the circuit needed?

Or - Can a power supply be constructed on which you could not only set the voltage but also the Ah it would provide before shutting off power output? That would be another way I could do what I want to do.

It would not actually emulate a battery in that it would produce a constant voltage where as a battery's voltage would decrease with use but it would be a way to at least approximate what I want to do - if my first idea of varying the Ah of a battery is not possible.

Perhaps a device to measure the amperage draw and time and calculate the Ah and shutoff power to the device at a set Ah value??

This is all probably quite impossible. I may have to get batteries of the correct voltage with different Ah and just time how long the device operates with each battery.


texts:
Could I check my use of diodes in the following circuit?

I'm wiring a new car stereo head unit into my motorhome (RV).

I'm going to use most of the standard radio harness connections.  However I would like to run the 12V power from the leisure battery so we can listen to the radio whilst parked up without the engine on and not drain the main battery.

The question I have is around the wire going into the head unit from the ignition circuit to turn the radio on when the ignition is on.  I want to add to this a separate connection from the leisure battery with a separate switch.  I want the radio to come on when I either turn the ignition on or switch the leisure battery switch.

I was going to use two diodes so that the leisure battery didn't interfere with the ignition circuit.

Have I got my wiring correct?

Will single 6A diodes do the job?

Thanks


texts: Number of samples (n) and number of data points (N)

texts: I have a question: I am doing some research on the FFT and had an inquiry. If I have a fixed number of samples per period, what is the effect of increasing my data points, say from 128 to 256? I know that my resolution increases since it is the sampling frequency divided by my number of data points. In other words, the distance in HZ between two adjacent data points decreases. Is there anything else? Or am I looking at this wrong. Any clarification would be greatly appreciated. Thanks!


texts:
Why are split bobbin cores not used for distribution transformers (10kVA and up)?

They are available for low voltage but are not so popular for high voltage. Why?


texts: What does a table under "Emission Point" label mean in metal-can laser LED mean?

texts:
Screenshot above comes from page 6 of this datasheet
That's for OSRAM PLPT5 450KA blue laser diode.
So far I did not have any problems understanding technical drawings, so I suspect this may be a standard notation I've somehow never seen so far, or a custom notation used on laser diode (or other optical elements) datasheets, so it seemed natural to ask here first, some of you probably have already seen this on other datasheets..
The thing I don't understand is the part marked with red line: "⊕ 0.17 A", data apparenly meant for "Emission Point" location. At first I thought it's its radius/diameter, but the same drawing in other places uses typical ø symbol for that, so it's not diameter.
I also do see another "A", I think it's using the same font, but I don't see any correlation between those.
Please solve that mystery for me, I have a feeling that this is something basic, but it eludes me:

red line, what does ⊕ symbol mean?
red line, what does 0.17 dimension mean, and what is its unit ('A'? ampere?? angstrem??)
red line, what does A mean here? (any relations to 'A' from green line?)
green line, what is that black triangle denoted by [A] label?
it seems to be some marking/symbol, as it doesn't seem to be drawn in any way on the other two projections


texts: LTC3106 solar harvester over-voltage at output during recharge

texts:
I'm using an LTC3106 in the configuration of the attached schematic:

It works fine from battery and from Vin inputs, delivering the expected 3,3 V at Vout.
Problems arise when, with Vin present, the charging of the battery starts: at this point if there isn't a load of at least 0,6 mA the Vout stays at 5,2 V (almost the same voltage of Vaux) instead of the expected 3,3 V
This behavior appears regardless of the voltage of Vin input in the whole range 1-5 V.
Any idea?


texts: Using EEPROM for transceiver data communication in Tx and Rx mode?

texts:
I am planning to use EEPROM (ST-M95640-DF) in between Transceiver IC (ST-S2LP) and the MCU (STM32L152RE). I would put program commands in a read-only section of the EEPROM to be accessed easily.
Now my question is it advisable to use EEPROM to write data that transceiver IC has received and transfer it to MCU via SPI with a possible C language code? Will the write-time of EEPROM be a problem here for me? The data rate would be around 300 kbps and the clock would be operating at 25 MHz.


texts: Why feed back the common mode signal to the circuit under test?

texts:
This is the conceptual circuit diagram for a ideas detector.  It's from The Brain Bulb - I've Got an Idea! by Jeri Ellsworth.  She uses an instrumentation amplifier (AD620) with a feedback element which is highlighted below:-

This arrangement is consistent with that chip's datasheet example for an ECG monitor, as:-

I found this question that has a similar circuit, but outputs the common voltage which I can understand if you want to measure it.  By why would Jeri's circuit (and the ECG example) feed it back into the person?   Isn't the point of an instrumentation amplifier to automatically remove the common signals?  And why then do this for Jeri's circuit, and not a Wheatstone bridge?  She just says that it's to reduce noise.  Lorry weigh bridges have noise too.


texts:
I'm looking to start a few different projects and stock up on some basic components - I was just wondering if anyone knows a good supplier of DC motors, stepper motors and servos?

I'm in vicinity of Sydney in Australia, so big pats on the back if they ship here. Thanks!


texts:
I recently asked a question that ended up involving answers about an automatic global reset capability that FPGAs have, and though the question got solved, I'm still quite unclear about this, and would like more information. I tried to scour the web, but wasn't able to find satisfactory answers.

1) What exactly is this global reset capability?

2) Why do FPGAs have this capability?

3) How do FPGAs infer this capability?

4) Could you provide an example of code which would have the FPGA infer the global reset, and an example using the same code where the FPGA does not infer the global reset?


texts: For p-n junction, at the depletion region which side is at higher potential?

texts:
At depletion region, a potential barrier is setup, E(electric field is from right to left)[according to viewer], but left side is shown to be at higher potential.

Inside a battery, E is in the direction of +ve terminal to -ve terminal.

1st image source: http://www.satishkashyap.com/2015/08/solutions-for-tutorial-2-on-pn-junction.html

2nd image source: http://web.mit.edu/sahughes/www/8.022/lec08.pdf


texts: Ground Connection When Using AC Wall Wart Supply

texts:
I'm working on an audio project and was planning to power it off of a +/- 12V wall-wart power supply, of the type commonly used to power modular synthesis racks. I've noticed that these supplies only have positive and negative voltage connections, and no connection for common mode or ground.

If I am using this type of power supply, what do I use as my ground connection?

Specifically the issue I am concerned about is that I am using a step-down regulator (https://cdn-shop.adafruit.com/datasheets/tsr1.pdf) to power a microcontroller I am using in the project, and want to make sure this is properly grounded.


texts: I can't get my switching power supply to turn on!

texts: I recently purchased a power brick (VM-80W12) and I've been trying to test it with the multimeter to determine the polarity. It however registers 0 Volts continusly (yes I plugged it in) I've heard that sometimes a power supply will only switch on when it get's a load resistance on it's output and I was wondering if that was true. If so then how do I go about testing the power brick?


texts: How does a dielectric alter the electric field?

texts:
My textbook is trying to explain why adding in a dielectric between two conductors causes a change in the field inside. They provide the following image:

I don't understand how the second image is equal to the third image. Why does polarization and alignments of the molecules create an electric field in the shown direction?


texts: How to limit input current with LTC3625 and MPPT circuit?

texts:
How can I limit the input current with this circuit?

I need it to draw a max of 0.2A, so I can see how long it takes to charge different capacitors. Changing the value of R1 on PROG pin does not reduce the input current as per my previous question.

As you can see below, the input current is 5A.  My real solar panel only puts out 0.2A, so I want to simulate how long it takes to charge different capacitor values before I build it.   Also the simulator only seems to work with Voutset to 4.4v.  If I make Vout=0, then it does not reach the output voltage.


texts: Trouble understanding the LM555 schematic for 50% duty cycle oscillator mode

texts:
I am working with a LM555CN and I am trying to have it run in astable mode and make a LED blink. In essence I am trying to follow along with this video.
Now, there is a part in the chip instructions where it tells you how to set it up in order to have it run with a 50% duty cycle.

Here is the part where I am not understanding correctly and I would like someone to explain this to me.

The way I read this (which is wrong apparently) is that these 2 resistors are connected in series (effectively creating a voltage divider, right? Not right?) where the end of the second resistor goes to pin 7 and the half-way point goes to pin 6 (and 2).
In the image attached below, the bottom pair is how I implemented it. The top pair is how it's implemented in the video.
I perceive my implementation as what I see in the schematic, yet it does not work as expected. The LED does not blink and stays on (or it blinks very fast, not sure).
If I make the connections as shown in the video (top pair), it works as expected.
This is where I cannot really wrap my head around how things work with the way they are connected in the video.
The way I see it, the resistors are connected in series again, but this time the half-way point feeds to pin 7 and the end of the 2nd resistor feeds to pin 6, which is not what I see in the schematic.


texts: Why is propagation delay of ethernet cables unaffected by cable length?

texts:
I did some searching on how propagation delay in ethernet cables is affected by the cable length. The answer seems to be that the delay is negligible until the cable length reaches a kind of threshold value which imposes a limit on the maximum length of ethernet before it becomes too unreliable. However, propagation delay is distance/speed, so technically a longer cable should have a longer delay. I am assuming the cables have the same diameter.

My guess is that since information is continuously sent in a stream, while it takes longer to initiate the transfer, the rate of data transfer is unaffected. However, the latency would still be slower, which would be a problem. Why is the cable length rarely discussed?


texts:
In RF communication the carriers such as 950MHz, 133MHz are available under 1 GHz. If there are 50 devices using the for example 433MHz carrier, then how could  large number of devices talk to each other? Wouldnt their communications be disturbed?

What is the limiting factor for the number of devices that can talk to each other at the same time?


texts: Why Does the And Gate have Two Transistors on Top?

texts: Wouldn't the left-side part of the diagram function as a nand gate without the two transistors at the beginning? Why are they part of the diagram? Because in the following picture of a nand gate, it's not an issue.


texts:
I trying to detect if a "dominant" state on the CAN bus is set from a specific CAN node. For this I place a "bridge" between the node and the bus.

I don't want to forward each frame with a microcontroller, rather I would like to have a possibility to determine the direction on the bit level regardless of frame structure/bit rate.

Two possible solutions I came up with so far:

Clearly this blocks the bus, but would there be a way to prevent this from happening?

Buffer each bit with a microcontroller before forwarding to any side of the bridge. With this solution I would shift all bits +1 and would also need to determine the bit rate.


texts: atmega32u4 configure counter in CTC mode

texts:
as pointed out in thread: atmega32u4 use Timer as souce for a counter
I tried to use the generated clock of timer 4 as input for a counter1
and counter1 should fire the compare match event after 42 clock cycles.
But I'm not able to reach the desired behavior.
Here is a little test code:
#include "Arduino.h"

#define CLOCKPIN 12
#define DEBUGPIN 19

//#define USE_A

// generate 1 MHz from 8 MHz
#define CLOCKCYCLE 3

// UPDATE
#ifdef USE_A
ISR(TIMER1_COMPA_vect) {
#else
ISR(TIMER1_COMPB_vect) {
#endif
    digitalWrite(DEBUGPIN,HIGH);
    digitalWrite(DEBUGPIN,LOW);
}

void setup()
{

    // set up pins
    pinMode(CLOCKPIN, OUTPUT);
    pinMode(DEBUGPIN, OUTPUT);

//--------------------- generate clock -------------------
    // reset timer4
    OCR4C = 0;
    OCR4D = 0;

    TCCR4A = 0x00;
    TCCR4B = 0x00;
    TCCR4C = 0x00;
    TCCR4D = 0x00;

    TCNT4=0;

    // Toggle OC4D on Compare Match | enable PWM
    TCCR4C = _BV(COM4D0) | _BV(PWM4D);

    // Clear Timer on Compare Match
    TCCR4D = _BV(WGM41);

    // set lock bit for sync update
    TCCR4E = _BV(TLOCK4);

    // Set compare value
    OCR4C = CLOCKCYCLE*2;
    OCR4D = CLOCKCYCLE;

    // No prescaling
    TCCR4B = _BV(CS10);

//--------------------- setup counter -------------------

     //reset timer
    TCNT1 = 0;

    // disable
    TCCR1A = 0;
    TCCR1B = 0;

    // clear interrupt flags
    TIFR1 = _BV(OCF1A) | _BV(OCF1B);

    // trigger on falling edge of T1
    TCCR1B = _BV(CS12) | _BV(CS11) | _BV(CS10) | _BV(WGM12);

#ifdef USE_A
    // interrupt on every 42. cycle
    OCR1A = 42;

    // turn on compare A interrupt.
    TIMSK1 = _BV(OCIE1A);
#else
    // interrupt on every 42. cycle
    OCR1B = 42;

    // turn on compare B interrupt.
    TIMSK1 = _BV(OCIE1B);
#endif
}

loop is empty.
With define USE_A I get the following waveform:
 the interrupt is fired every ~66200µs sounds like the 16bit counter overflow.
With define USE_A commented out I got the following wired result:
 219µs clock on 1180µs clock of. the only idea I have for this is a reset or something.
Does anybody have an idea whats wrong with my counter code?
UPDATE:
Changed the missing flag and ISR call. Now does USE_A look like this:

Top should now set to 42 and reset to 0 after interrupt occured?
But currently it takes nearly twice the time...


texts: 12V Jacob's Ladder circuit introducing noise on input and messing with PSU

texts:
I have made a Jacob's Ladder display for fun.
I have no oscilloscope to give exact details, but there must be some kind of noise or high-voltage ripple that is resetting the display of my Lab Power Supply (based on DPS5015 buck module).

I have attached a pic of the circuit. Is there some kind of diode/cap/inductor I could use at the input to stop the spikes/noise from resetting my PSU display?

The circuit is meant to run off a car battery, but that is not ideal for me. I imagine a battery won't care one bit about this noise.

(I understand this is likely a fault of the PSU for not handling the noise/spikes properly. I plan on using a 12V laptop brick I've salvaged when I make a proper enclosure. But if it's as simple as adding some components, I may as well, to eliminate any possible issues with the laptop brick (a Lite-On SMPS).)

On a side note, the circuit says "12V input, 5A minimum" but I've measured under many different scenarios for spark gap etc, and it seems to remain constant at about 1.3A. Due to this, I imagine the 2.7A laptop brick I play to use will be adequate. I'll install proper protection (on top of the laptop brick's own).


texts:
I'm using the TPS63050 buck/boost converter in a design. The datasheet basically just says "don't leave it floating" in the table on page 4. I want this enable pin to be under the control of an external circuit, and so I will implement a pull-down resistor on that pin to accommodate the condition where that external circuit would otherwise float the pin. What I can't quite ascertain from the datasheet is, how big a resistor can I get away with for this purpose. I was thinking of populating a 1 MegaOhm resistor to GND, to minimize the static current draw required just to enable the regulator.

Is there any reason I should be concerned, or any likely problem, with using such a large resistance in this context? My gut says it should be fine, but it would make me feel even better to get some positive affirmation or advice to the contrary from my colleagues here on EESE!


texts: How to make +12v standby power from ATX power supply?

texts:
Can I make a 12v SB line from the existing lines on this ATX power supply? I'm told that +/- 10% voltage is acceptable. Can I combine a (red + orange + purple) 5V + 3.3V + 5VSB = 13.3VSB?

I'm working on a Dell C8220 board with proprietary 18-pin, 8x +12V & 1x +12VSB & 9x Ground.


texts:
I have the following RCL circuit

simulate this circuit – Schematic created using CircuitLab

After using the Laplace transform my lecture notes mention that we get the following circuit

simulate this circuit

What I don't understand is why the polarity of the voltage source next to the capacitor is like that and it is not reversed. Shouldn't the initial condition V0 match the polarity of the source? Isn't that that reason we add the voltage source in the first place?


texts: I am having trouble understanding a lecture slide for Mask Programmable Arrays. The cell on the right is supposed to represent a 4-input NOR gate. But I just cant wrap my head around which pads correspond to the NMOS and PMOS transistors.  Can someone explain where the transistors are located? Also if they are intrinsically connected to each other.


texts: Advanced Math in day to day Electronics?

texts:
So i've been watching the MIT 6.002x Classes and they are really interesting, I feel like i've got a good grasp of Circuits and the Basics (I graduated with a CS degree...but EE appeals to me too).

Anyways I noticed....probably like a lot of people that a lot of the advanced math isn't really used on the job. It happens...better to know it than not I guess. But leaving out Signal Processing and similar "Intense"/math heavy sub-fields of electronics....how much Advanced Math do you feel like you use on the job?

I guess someone that did circuit design, Microcontroller Programming and such how much math would they really get into.

And Second Question: Is there a book that goes into the Advanced Math that's necessary for this? or do "most" electronics books pretty much already have what is necessary.


texts: How to produce a simple beep/sound without using piezo-buzzer

texts:
I am designing a fairly simple board where I need to sound a simple chirp/beep every couple of minutes, however, layout space is extremely limited.

Therefore, a full-blown piezo buzzer is a no-go; they mostly seem to be of at least 10 mm diameter based on my research.

I am interested in a type of part or circuit within less than 6 mm X 6 mm X 3 mm of board space, which can produce a chirp/beep (of around 10 to 20 dB, i.e., audible from about 5 feet away). Is this achievable?

For instance, I recall encountering a high-pitched noise in the past from an inductor within a buck-boost regulator circuit -- the sound wasn't loud enough but I am also curious to see if there are methods to reproduce something similar but with greater amplitude.


texts: How to demonstrate the effect of baudrate in serial communication

texts:
Regarding baudrate in serial communication, the only requirement is that both devices operate at the same rate. The common baud rates are 1200, 2400, 4800, 9600, 19200, 38400, 57600, and 115200 ect. And especially what I see is that 9600 is the most popular.

On the other hand I also see in some C codes for microcontrollers they also for instance use much higher baudrates such as 115200. Now all the time in my encounter whenever I reduce the baudrates to 9600 or even more the system still works. Last time I think I tried with an encoder and changing the baudrates did not change any functioning in practice. I simply lowered the original baudrate which was 115200 to 9600 and there was no problem. Why would they set it to high baudrate when lower works it is a mystery for me. (¿)

Since I didn't encounter any example in my micro environment and limited experience, I'm very curious to know when would baoudrate start to affect a system. Some encountered examples would help a lot. I even appreciate if one can suggest a simple setup where I can spot the error or an issue due to low baudrate. I can use an Arduino and HyperTerminal to test such a communication. What I want to observe is that lets say we have the Arduino is nonstop sending some fixed data to the serial port and we read that with a program such as HyperTerminal with a baudrate of 115200. Let's say we start to lower the baudrate and we observe at a particular baudrate we get/read nonsense. What would be the idea to create such a test? I mean I need to relate the data somehow to the transmission speed aka baudrate.


texts: References with explanations of how works CORDIC algorithm for division

texts: Does anyone know any available reference to learn how works CORDIC algorithm to implement a division?


texts: How do I draw M-PAM curves of Channel Capacity Vs SNR?

texts:
I've seen the following figure in several different articles:

(this one was taken from here)

I understand that channel capacity of the Gaussian signal is

C = 1/2 * log2(1 + SNR)

However, I don't understand how to get the other ones (M-PAM with M=2,4,8...). I've tried deducing the error probability and then using the channel capacity equation for a BSC channel to no good.

Does anyone have any pointers on this? I want to draw it with Matlab/Python/Whatever and see it with my own eyes :)


texts: Learning the Art of Electronics - keypad

texts:
Has anyone found ordering information or the schematic referred to on Page 620 of Learning the Art of Electronics?

Page 620 of LAoE says, "The keypad is not a standard commercial part. See Appendix E for ordering information and Appendix 14N.20 for the schematic, in case you want to build your own."

However, Appendix E doesn't mention the keypad. The digital parts list on the LAoE website (link below) says, "See LAoE website" but there the trail goes cold; the website gives details for ordering the LCD but not the keypad (as far as I can see).

Also, Appendix 14N.20 doesn't seem to exist, nor the schematic for the keypad.

So the questions are:

Has anyone found ordering information for the LAoE keypad?
Has anyone found Appendix 14N.20 or the schematic for the keypad?
Can anyone suggest an alternative approach to providing the keypad functionality which includes:
controlling lines D4 to D14 of an XC9572XL counter; and writing 8 bit values to RAM via a 74HC541 octal 3-state buffer.

https://learningtheartofelectronics.com/parts-lists/parts-lists/


texts: Arduino piezo vibration measurement circuit

texts:
I'm looking for a very simple measurement circuit to measure vibrations with a piezo elment and an arduino device. I want to read positive and negative values.

I have this sensor: http://www.seeedstudio.com/wiki/Grove_-_Piezo_Vibration_Sensor

I know that this sensor module only gives me digital output. But I want to measure the vibration amplitudes and the frequency. So I would use just the piezo element.

I found a lot examples, from very simple to high accurate. But most of them cutting of the negative values. E.G. http://www.learningaboutelectronics.com/Articles/Piezo-knock-sensor-circuit.php

And in the example above, there is no protection for the arduino. I also found statements, that the arduino needs no protection reading a piezo sensor at analog pin, because of the low current. And the analog pins are protected against higher voltages.

I want just a simple circuit to read negative and positive values from that piezo element. My arduino device use 3.3V input voltage. The piezo sensor can have in extrem up to 70-90V.

What is the minimum configuration to set up such a measurement circuit? I don't need highest accuracy. It should be as easy as possible. It is just for test purpuses. I think I have to use an voltage divider with two equal high resistences to set a DC offset for measuring the negativ values. But what else do I need for a minimal working example?


texts:
I am trying to understand the circuit have shown below. As far as I tried, it seems a differential amplifier for me. So, I tried to solve it in the way we deal with DC signals. But I failed to solve it. I couldn't understand the behaviour of this circuit. I am not good at AC signal analysis. So, I came here for help.

This is the circuit I am dealing with. I need to know some info about this circuit.

Which kind of category this circuit belongs? I guess it belongs to differential amplifier type.Is it right?

There is a voltage offset added at non-inverting input of the op-amp. If I remove this offset, the simulator shows simulation error. What's the purpose of this DC input there?

This is the output signal of the circuit. Blue color denotes input, red color denotes output. Can I get the same output without adding DC offset?


texts: On initiating I²C communication, status register SR1 gets reset immediatelly

texts:
With the following code to handshake an EEPROM
 STM_enableRCCAPB1PeriphClock( RCC_APB1Periph_I2C1, ENABLE );
 STM_resetRCCAPB1PeriphCmd( RCC_APB1Periph_I2C1, DISABLE );
 I2C_Cmd( m_pEE_I2C_TYPE, ENABLE );
 I2C_ITConfig( m_pEE_I2C_TYPE, I2C_IT_ERR, ENABLE );
 I2C_InitStructure.I2C_Mode        = EE_I2C_MODE;
 I2C_InitStructure.I2C_DutyCycle      = EE_I2C_DUTY_CYCLE;
 I2C_InitStructure.I2C_OwnAddress1     = EE_I2C_OWN_ADDRESS;
 I2C_InitStructure.I2C_Ack         = EE_I2C_ACK;
 I2C_InitStructure.I2C_AcknowledgedAddress = EE_I2C_ACK_ADDR;
 I2C_InitStructure.I2C_ClockSpeed     = EE_I2C_CLOCK_SPEED;
 GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_6 BITOR GPIO_Pin_7;
 GPIO_InitStructure.GPIO_Speed  = GPIO_Speed_50MHz;
 GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF_OD;

  /* Generate the START condition */
  I2C1->CR1 |= I2C_CR1_START;

  /* wait until START condition is set */
  while ( NOT ( I2C1->SR1  BITAND  I2C_SR1_SB ) )
  {
  }

  /* send the address of the EEPROM with r/w-bit reset */
  address = EE_EXT_ADDRESS;
  address |= 1u; // read / receiver
  I2C1->DR = address;

  /* wait for either ADDR (ACK) oder AF (NACK) to be set */
  u16StatusRegister = 0x00u;
  while ( NOT ( ( u16StatusRegister  BITAND  I2C_SR1_ADDR )  BITOR  (
u16StatusRegister  BITAND  I2C_SR1_AF ) ) )
  {
    u16StatusRegister = I2C1->SR1;
  }

I see the rising of either AF or ADDR in the debugger's register view after executing
I2C1->DR = address, but as soon as I execute u16StatusRegister = 0x00u, all bits in SR1 are reset.
Could anybody guess why that's happening?
I'm using IAR workbench 7.50 and IAR I-jets debugger on a STM32f103, and there are no interrupt routines coded.

I re-coded it a bit:
 /* Generate the START condition */

 I2C1->CR1 |= I2C_CR1_START;

 /* wait until START condition is set */

 while ( NOT ( I2C1->SR1 & I2C_SR1_SB ) ) { }

 /* send the address of the EEPROM with r/w-bit reset */

 address = EE_EXT_ADDRESS | 1u; // read / receiver

 I2C1->DR = address;

 /* wait for either ADDR (ACK) oder AF (NACK) to be set */

 u8Timeout = MaxWaitForACK;

 while ( ! ( ( I2C1->SR1 & ( I2C_SR1_AF | I2C_SR1_ADDR | I2C_SR1_BTF | I2C_SR1_TXE | I2C_SR1_RXNE ) ) || ( u8Timeout == 0u ) ) ) {

     u8Timeout--;

 }

 if ( I2C1->SR1 & ( I2C_SR1_ADDR | I2C_SR1_BTF | I2C_SR1_TXE | I2C_SR1_RXNE ) ) {

     /* BTF set <-- EEPROM send ACK */ /* ADDR set <-- EEPROM send ACK */

     bRetVal = TRUE;

 }

 else {

     /* BTF not set <-- Timeout <-- EEPROM send NACK */ /* AF set <-- NACK read */

     bRetVal = FALSE;

 }

This works always (single step, debugging context, and live) in the case the EEPROM is missing, but in the case the EEPROM exists, it only works when stepping or debugging, not live.
And even more curious: when breaking after the evaluation, see AF set in the fail case, which I don't do when stepping through.
Any thoughts?


texts: Send digital data over same wire as analog data

texts:
I am trying to modify an existing circuit that I am able to send another digital signal over the same connection.

My circuit is a so called "Partyline Intercom" which is based upon the schematics of Richard Crowley's Com Clone 2.

The circuit has an audio "bus" where all the audio signals are mixed together, to every unit there is a mic and headphone hooked up and you can hear everything the others say over the mic (as well as your own voice) there is also a second signal (called "Sidetone") which is as I understood basically a DC coupling. When this signal is sent, on every unit flashes a light which means something like "Take the call".

The signals are sent over a 3-Pin XLR-Cable (+30V - Signal - GND).

I do not want to change the given functionality but add up a digital channel where I can transmit some data over the same audio bus (using an Arduino Nano for example). These data will not have a high rate, I will send something like 16 bits payload (64 bits maximum if it would work) in 50-100ms to control some status LEDs on the units (Like a camera Tally - "You are live now" - red light).

How can I implement this digital channel? Would it be possible to easily build a bandpass filter that sends everything under 30.000 Hz to the audio and sidetone circuit and everything over that threshold to the digital connection?

The maximum distances I would use are something like 50 to 100 m.


texts:
Im looking to learn more about this topic so that I can implement it in an amplifier design. I've read around and understand most of the math behind it, but I'm still a little fuzzy on how to implement it. Here are somethings I would like to know to start with:

Is this a strictly code-related method generating PWM signals, or is there a way to implement this in hardware?
Are there certain methods of commutation that do not work with this scheme (such as HEDs, encoders, or resolvers)?

If anyone has any links that would be useful in helping to further understand SVM, I'd greatly appreciate it if you could share them with me.


texts: Buck converter or LDO with multiple voltage levels

texts:
I'm designing a project at the moment that will be powered by USB-C. There's more information about that in this previous question of mine.

The project can be easily split into two parts:

Control/logic side which requires 3.3V/500mA
LED side which requires 5V/6A

What makes this slightly more complicated is how the power is supplied from the USB-C. On connection, the power adapter will provide 5V (current can depend on a few factors) on the VBUS pins. A USB-C controller can then negotiate with the power adapter to provide up to 20V/5A on the VBUS pins. For my particular project, I'll be using a power adapter than can provide 20V/3A.

At the moment my thoughts are:

Use the power from the VBUS pins to power a wide-range LDO that takes 5V upto 20V and has a fixed output of 3.3V. This can control the logic side of things.
Provide VBUS to a buck converter, which is only enabled once the VBUS voltage reaches 20V, to provide 5V to the LEDs.

My primary concerns are:

The efficiency and heat dissipation of an LDO that has a 20V input and outputs 3.3V (even only with 500mA maximum current).
The stability of the output from the buck converter when supplying the LEDs. These LEDs are similar to the WS2812B
The heat from the buck converter running with the relatively high current.

Is there a better way of doing this, or is the buck converter for the LEDs and the LDO for the logic the best way around this? In particular are there any issues that might occur that I haven't mentioned above?


texts: Why can generators be damaged by series capacitors (SSR)?

texts: Specifically I am talking about generation that uses steam to generate turbo spin (steam cycle) like nuclear or natural gas plants. I have been learning about Subsynchronous Resonance (SSR), which is whenever a generator of the kind mentioned above can be potentially damaged due to sudden changes in torque induced by a series capacitor creating frequency and voltage oscillations. Long distance power lines will use a series capacitor to reduce the inductive losses created by the line. What I would like to know is: What leads to the capacitor creating these oscillations in the first place?


texts: I have a light that I want to order new optics for. Any one know how to find manufacturer information or spec sheets?

texts: A friend showed me LEDsupply.com where you can order new lenses and possibly LED replacements. However, I have not been able to find enough information about this led or circuit board to move forward. I'm hoping someone knows a reliable site or way to conduct this type of backward search.


texts:
I want to connect some ATmega328P µC's to a CAN bus by using MCP2551 & MCP2515 ic's. I want to use some Cat5e 4x2 twisted pairs cable.

How do I make the actual drop off points? Do I just cut the cable in two, twine the cut wires together and solder them to the MCP2551 pins?


texts: What is "transformer connected" vs. "direct connected" for a electricity meter?

texts:
I am looking at sub electricity meters. Right now I am reading about the ABB product line EQ. In the documentation (link to PDF, "Electricity Meters - For modular enclosures and DIN rail"), they split the products into two categories, the ones that are "transformer connected" and the ones that are "direct connected".

If I read the documentation correctly, they also call the "transformer connected" by the acronym "CTVT". I've tried to look this up, also without luck.

What does that mean?

I only know a bit more than highschool physics, so please try to give an answer that a non-engineer can understand. If that is possible :)


texts: Why are crystal capacitors considered to be in series?

texts:
I'm trying to pick a crystal and capacitors for the clocking of a MCU, and, from what I've understood, my crystal needs a load capacitance of 30pF (it's specified in the datasheet) in order to properly work. The way I'd have done this would be:

simulate this circuit – Schematic created using CircuitLab

However, everyone is telling me I should do this:

simulate this circuit

Because the capacitors are, somehow, in series. This makes zero sense to me: I'm using one more capacitor, and the capacitor in the right side is next to the low-impedance output of the inverter, so I just don't see it in series. Also, my design uses one less capacitor. What am I missing?


texts:
During my research of PSU I came across schematic from Linear's datasheet:

1) Whats the purpose of node which is going from output to SW pin of buck converter?

2) Is node which provides 6V headroom for LDO sufficient for normal operation of PSU?