texts: Automatic switching of a constant current circuit

texts:
I'm running 14 ~3W (700mA) LEDs in series on a constant current LED Driver that handles between 36-65V output.  The driver runs the LEDs at 600mA.

The heatsinks I've attached are pretty small, and if I put my fingers on one, it heats up in about 2 minutes or so, and then takes about 20 seconds to get cold again.

I'd like to use an Arduino to turn on and off the circuit, for roughly these periods.

I wrote a basic sketch to handle the Arduino part to keep a relay on for this period...

  s_l = millis() % 120000;
  on = (s_l < 100000) ;
  digitalWrite(relayPin, on);

I have relay modules, and transistors lying around... but I'm not sure how well they will play with a constant current circuit.  The LEDs don't care if I am PWM'ing, but maybe the driver will get some weird feedback loop if I mess with it?

I'd prefer to use transistors, because the relays clicking will probably drive me crazy - but I will take any solution.  What is my best option?

Just a relay on the AC side?  I'd prefer not to work with AC, as it is a lot more dangerous.

Thanks in advance...

Edit:  picture of constant current LED driver guts:


texts: Is the SCK line in I2C unidirectional or bidirectional?

texts:
I've always considered SCK to be a unidirectional line since the master generates/transmits the clock signal and the slaves "see" the generated pulses. I have found many sources that agree with this idea via Google. However, I was reading this I2C primer/refresher by Analog and I noticed they defined the SCK line as bidirectional:

From paragraph 3: "The I2C bus uses only two bidirectional lines, Serial Data Line (SDA) and a Serial Clock Line (SCL). "

So what's going on here? Is the SCK line only bidirectional sometimes, like when there is more than one master in the I2C configuration?


texts:
I want to build a lithium ion battery charger with tp4056 module but most of my power supply's voltage is 12-19 V

Datasheet says input voltage is 4.5-5.5v and current 1A

Can I connect 1-3 tp4056 module in series  ?

I think it won't work because voltage drop not constant ( depends on how much module consume )

I thought to use l7805 or lm317 but 1A is seemed too much for them

Right now I'm thinking about using pwm circuit with MOSFET but If anyone have better idea , I want to hear it
Also if I make pwm circuit to convert 19V (4A) to 5v , output current stays same or could it be 12A ?

Thanks for helping


texts: Microchip PIC10 (8 bit microcontroller) learning reference. Where to start?

texts:
So I've generally learned how to use an Atmel Attiny13a, but now I have found that I need to switch to a Microchip PIC 8 bit microcontroller such as the PIC10 series.
Can anyone give me some good online resources or names of books that teach microchip 8 bit microcontrollers? I know there are some advanced 16bit microchip resources available, but I can't find anything on any of the 8 bit series. I have no idea where to start.
And the switch to microchip is due to cost and programming cost as well... It is a very low power simple product with only 3 I/O pins needed.


texts: What happens when main() returns on ARM-GCC

texts:
As I am working myself into the AT91 Bootstrap project, I have found that its main() function apparently returns the address of the next-level software component:
int main(void)
{
  ...
#ifdef CONFIG_BACKUP_MODE
    ret = backup_mode_resume();
    if (ret) {
        /* ...jump to Linux here */
        return ret;
    }
#endif
  ...
#if !defined(CONFIG_LOAD_NONE)
    return JUMP_ADDR;
#else
    return 0;
#endif
}

I am wondering, what happens at this point under the hood:

Is the return value stored according the normal calling conventions or the return value of main() is treated in a specific way?
What processor instructions get executed after the main() returns? Is it something in some epilogue of main() or it is some hardware-level behavior of the SAMA5 processor? How exactly does MPU use the return value?
To what extent is such behavior generic: SAMA5? ARM?


texts: Finite State Machine made of JK Flip Flops in Logisim help

texts: I'm trying to make a 4 bit finite state machine that prints out (2, 3, 5, 7, 11) in order. I have completed the next state table, flip flop transition table and the JK Karnaugh maps for all the bits. However when I implement the circuit in logisim the number 2 ,3 ,7 and 6 are repeated in a loop and I have no idea why.


texts: What would cause an ADC to stick on an arbitrary value?

texts:
I have a differential ADC (HX710) that I am using to interface a load cell. The wiring is as follows with (J4) going to the load cell:

Mostly, this reads very reliably and accurately. However, intermittently the ADC reading will stick at a seemingly arbitrary range of values (ie. not a power of 2) that would normally represent a very high weight (but not a max reading with respect to the ADC's range). I can't consistently get the circuit into this state. It seems almost random - say every 20th power cycle?

During this failure mode, I can completely unplug the load cell from the system and the ADC will still be floating in this high range.

Under normal circumstances, running the ADC without a load cell returns just the expected unweighted value bouncing around in the noise floor.

Is there a reason that a differential amplifier, like this, might get stuck in a high range intermittently?


texts: Virtually grounded negative input op amp exists but no virtually grounded positive input. why?

texts:
If the positive input of an operational amplifier is grounded, the negative input is said to be virtually grounded and it has therefore zero potential.
But the contrary is not true. A grounded negative input doesn't make the positive input virtually grounded.
Why?


texts: Resistance of a material during dielectric breakdown?

texts: Basically my question is that when a material (let's say air to be specific) undergoes dielectric breakdown with enough voltage, how conductive does it becoming during the breakdown? Maybe that depends on different factors, so let's just say for air in standard conditions and with just about enough voltage for it to breakdown (around 30 KV/cm). I saw a question asking about this which didn't have any answers.


texts: Why do 2 different online active filter calculators give way different GBW requirements for the same frequency range?

texts:
I am confused about 2 different online active filter calculators giving different GBW requirements for the same frequency range. One calculator is giving GBW requirements in the kHz range while the other calculator is saying I need a very high GBW in the MHz range - up to 40 MHz.
I am trying to calculate an 8 pole bandpass filter in the range of 5400 Hz - 7500 Hz and this is what each says about GBW requirement for each section:
first website is https://tools.analog.com/en/filterwizard/:
GBW for each section with the above calculator:  768 kHz, 654 kHz, 741 kHz, 547 kHz
2nd website is https://webench.ti.com/filter-design-tool/filter-type:
GBW for each section with the above calculator: 3.4 MHz, 4 MHz, 27.4 MHz, 39.6 MHz


texts: How real an issue is static for hobbyists (Arduino etc.) for parts storage?

texts:
The parts I buy come in all kinds of packaging:

Here we have a USB charger in a basic anti-static bag, Kapton tape and MOSFETs in ESD bags and a small development board in a plain plastic bag.
I'm pretty confident the Kapton tape could have been safely shipped without an ESD bag! But for other parts, I'm not so sure.
So my question is - when it comes to storage can I fairly safely chuck most of the kind of parts a hobbyist would use into something like this:

By hobbyist, I mean someone doing small Arduino-style projects with LEDs, motors and the like.
Or should the plastic storage containers and their potential for static worry me even as a hobbyist? If it should worry me, is there anything I can easily do about it? E.g. would it be enough to line the bottom of the containers with conductive foam like this:

My impression (perhaps false) is that most hobbyist parts are fairly static-safe. The fact that a company like Sparkfun is OK shipping small development boards in plain plastic bags suggests to me that maybe this isn't such a big issue?
Are there particular parts that someone like me needs to look out for, e.g. most large thru-hole parts are fine but one should look out for X?
I'm primarily interested in storage - I do all my work on an anti-static mat (that I have connected to a radiator) but I'm starting to accumulate enough parts that I want to get them more organized (and so just bought the parts bin seen above).


texts: Can a voltmeter itself disturb the exact measuring of voltage?

texts:
I'm trying to understand the effect on a system when the voltage of the system is measured by connecting a voltmeter.
For example let's say we are trying to measure the voltage of a battery.
To measure the voltage of the battery, we must connect the voltmeter. Each probe will be connected to each side of the battery (positive and negative lead.)
Assume this voltmeter is a high-end one, there is almost zero current flowing through the voltmeter (infinite input impedance.)
Although it is, I'm concerned that this behavior itself could disturb the voltage of the battery because the Fermi level of each side of the battery will change.
When a probe of voltmeter is connected to one side of battery, their Fermi level would be in alignment for thermodynamic equilibrium because both the probe of voltmeter and the lead of battery are metal. If their material is different, the Fermi level of probe-lead connected metal would be somewhere between that of pristine probe and lead.
Anyhow, by connecting the probe to the lead for measurement, this changes the original Fermi level of the battery. The same thing may happen when we connect the other probe of voltmeter to the other side of the battery. So the voltage displayed in the voltmeter would be somewhat distorted because this is the result after some electrons from the voltmeter flow into or out of the lead of the battery.
Since the voltmeter measures Fermi level difference between two probes, the metal of the probe will probably have an effect on the result.
I've never seen or heard this kind of effect discussed. Is it because the contribution of the effect mentioned above is negligible or am I just wrong?


texts: How to automatically switch RF path to external antenna

texts:
I'm designing a circuit that has 2 antenna options for one transceiver @ 1.6 GHz.  One antenna is internal and is the default RF load.  Another antenna is external - to be attached by the user if desired.  If and when the external antenna is attached, an RF switch will change the path from the internal to the external antenna.  Here's a simplistic sketch of what I'm thinking...

I was thinking of using a directional coupler to measure the VSWR on my external antenna line and using the result to control the RF switch automatically.

Does this make sense?  I'm not very experienced with RF designs... Are there any do's, don'ts or gotcha's?  Best practices?

edits
My average transmitted power is 1.6W during a TX sequence.  This is for a hand-held device (walkie talkie size)


texts: USB device with a serial number and 3 LEDs

texts:
I'm looking for a way to build a USB key. I have a bit of experience with the Arduino, however for this project that seems to be a bit of overkill.

The key should contain a unique serial number (EEPROM?), either to be programmed or factory-set (whatever is easier). Besides the serial number, I need to control 3 LEDs. Each LED has 3 states (on, off & blinking).

I was think to start with a CP2102 based USB TTL UART.

For the EEPROM: AT25010B (SPI) or AT24C01B (I2C) or a dedicated chip

The software (linux) should talk to the RS232 port and be able to retrieve the serial number, and set each LED to the 3 different states.

I read about I2C and SPI. I seems SPI is easier to control, but you need more pins to hook it up.

My questions are:

1) What would be the better protocol I2C or SPI (in terms of 'easy' implementation)?

2) Assuming you can't hookup the LED's and the EEPROM direct to the UART. I  need some type PIC to facilitate the communication. What would be a could PIC for this?

Not sure if it matters but: once I have a working prototype, I need to be able to batch produce a few hundreds of these.


texts:
What is difference between 2 transformers rated to give output the same voltage but different current (ampere)?

Such as, if a stepdown transformer is rated as 12V 600mA, and another is rated as 12V 1000mA (or 1A); what is difference in their function? in spite of same voltage, would they produce different current on load on secondary?


texts:
Have to find the power developing on the 7k resistor (I*U).

Calculated (hopefully correct) Rthevenin to be 12k//4k which would be 3k.
Circuit simulator shows that the current through the resistor should be 3mA but i can't figure out how to get to that number with the voltages provided, seeming as i would need my Uthevenin to be 30 volts for that to work (afaik).

What am i missing?


texts:
I often see those two terms explicitly used as synonyms, but sometimes from the context I would say they're not.
So, is a bypass capacitor exactly the same as a decoupling capacitor?


texts: Does the VDE 0100-722.543.101 apply to Powerline communication?

texts: The norm says that there should be no signals on the PE. I have seen a lot of Powerline devices been connected to PE e.g. Devolo Magic 2 lan DINrail. The question is are they using it just for reference/safety or do they actually send signals over PE? Does this rule apply to Powerline communication or not? Does anyone know that this device, in particular, conforms to the norm?


texts: How to use a SN75441 h-bridge in conjunction with an arduino

texts:
I am trying to use a SN75441 h-bridge in conjunction with an arduino in order to drive a DC motor forward and backward. Let me describe the setup and then the problem I am encountering.

I have an SN75441. Pins 1 and 16 are connected to the positive rail. (+5V) Pins 4,  5, 12 and 13 are connected to ground. Pin 8 is connected to a +9V power supply. Pins 2 and 7 are connected respectively to two of the arduino logic pins in output mode. They are alternating every few seconds being respectively H,L then L,H, then H,L again, and so on. You get the idea. Pins 3 and 6 are connected to the DC motor.

The +5 V positive rail for the SN75441 is supplied by the arduino. Everybody shares the same ground.

The setup is analogous to the one found here:
http://itp.nyu.edu/physcomp/Labs/DCMotorControl

My expectation for the behavior is that the motor will change direction every few seconds when Pins 2 and 7 reverse.

What actually happens is that the motor switches direction 0-3 times and then remains going in that direction forever. Now, what appears to be happening is that the arduino starts resetting very rapidly which means it keeps resetting to the logical output pins to their initial setting.

My question is two parts:
1) Why would that be happening?
2) How do I fix it?


texts: AM radio interference with class A amplifier

texts:
I am using a class A amplifier constructed around an NPN Darlington transistor (BC517) because the gain I was getting with a single NPN transistor was nowhere close to what I needed. The transistor is biased with two 100K resistor going from collector to base and base to emitter. Instead of a load, I have a 10K resistor, a 100K resistor from the collector drives the input to a comparator (this class A amp is being used as the input stage to a ADC I built). The input comes from an electret mic coupled to the base via a .1uF cap (I have given the mic a proper voltage bias with a 10K resistor). There is some small radio interference with the ADC, which I know how to deal with, but the main problem is that I am getting a massive amount of interference from a nearby AM radio station with my class A amp. The radio waves are being picked up at about the same volume as the sound from the mic. This will not do, so how can I fix it? Should I use a different kind of amplifier (it needs high gain). Is there a way to suppress interference in my existing design?

simulate this circuit – Schematic created using CircuitLab

Many thanks!


texts: Why single phase motors uses double pole single throw switches instead of a single pole single throw switch?

texts:
I've seen many motor starters that have double poles to contact the motor leads to the AC source. I wonder if there is any reason for not using single pole single throw switches which are mostly used in all home electrical applicances.
Why the neutral wie is not directly connected to the motor?
Any help is appreciated.


texts:
My mother is obsessed with new-age quackery, and has rented an "E-Power" machine, a device that appears to be a waveform generator connected to a belt that you wrap around your waist. I'm concerned that it might be dangerous because it seems to create electrical currents within one's body. It purports to allegedly increase the electrical potential across the membranes of one's cells, creating a host of health benefits.

One of their video demonstrations concerned me most. They show the person wearing the belt holding one side of a fluorescent light bulb, with the demonstrator touching the bulb partway. They show that the bulb lights up. It appears that the belt is inducing a potential within the participant, and creating a current which flows through the participant's arm, through the bulb, and through the demonstrator's arm. Since the demonstrator is wearing shoes on what appears to be a wood floor, I can only assume that either the potentials between the demonstrator and participant are equalizing, or the demonstrator is connected to ground in some way that's not obvious.

I was informed of the dangers of conducting current directly through one's body in my electrical engineering classes, so seeing the current conducted through the participant's arm concerns me, especially since the product advertises itself as functioning at 70 kilohertz. As I understand, humans cannot feel pain from electricity at high frequencies. This person's foolish experiment indicates that people stop feeling electrical pain somewhere around 20 kilohertz. This means that any possible injuries caused by this machine would be impossible to feel.

Am I right in being concerned about the safety of this device? Are there any safety concerns I've missed?


texts:
I've got an LM358 comparator turning on an LED. What I'd like to add is a way to dim the LED by a fixed amound when a 12v signal is sensed.

It's in a tach circuit in a car, and when the headlights are turned on the dash lights get fed power, so when that occurs it's probably dark enough where the LED should be less bright.

I've got something modeled in ltspice with a resistor and npn on parallel with the led to draw off some of the current. Does that seem sensible or is there maybe a better way? Thanks!

Here's an example of a similar 2-stage shift light in action:


texts: How to have a bad power supply fail safely?

texts:
I just read this article: iPad charger teardown: inside Apple's charger and a risky phony

Basically I would like to see by myself the effects of a bad power supply failing.

Can it be done safely?

Edit: Here are the reasons why I want to see it happen.

I would never buy a shitty power supply like this one (~3€ on eBay) for a device which costs around 500€, but considering the really low price, I am willing to spend some time to see what would have happened if I had bought and used this one. As mentioned in the article, one person seems to have died because of a badly insulated charger. So basically, I want to replicate the typical use case of such a power supply, and safely see how it fails. Will it explode, will it slowly die, or just stop working? I certainly am not going to plug my iPad in it. I am ready to spend a small amount of money on disposable electronic components if necessary. I hope this clarifies why I want to have it fail. And of course, my main concerns in this experiment are my own safety, and not to damage anything else beside the charger and the circuit that will draw current from it.


texts: 12 AWG galvanized steel high tensile wire okay for running 12 volt 7 A DC?

texts:
I need to run 12 VDC about 50' along a fence that already has several 12 gauge galvanized steel wires running on it. It is going to be pulling less than 7 A at most.  I can make sure the lines are not touching, but they are in the air and exposed to the elements. Will this work? and will I see significant voltage drop (greater than 5%)?  My battery is a 115 Ah deep cycle lead-acid and I have a 12 V appliance that needs at least 11.5 V that consume about 4 A.
Also, dumb question I want to ask, but does negative line need to run all the way back to the battery? and if so, can that touch metal t-posts posts that are 2' in the ground?  I am wondering if metal the fence itself was connected to the negative battery lead and my hot (+) were copper, insulated and direct would this help significantly?


texts:
I am trying to set up a circuit with a 14.31818MHz crystal (PAL decoding). The data sheet for the chip, using the crystal, states the relationship between the two capacitors, connecting the crystal to ground, as;

$$
C_{L1} = C_{L2} = 2C_{L} -C_{STRAY}
$$

I don't know what the Cstray is, neither what 2CL stands for. So how do I find the two in order to calculate CL1 and CL2?

Thanks


texts: GPIO Access on Cortex-M4 : Read-Modify-Write vs Atomic

texts:
I recently came across the Bit-banding feature on Cortex-M4 core and how it provides a solution to avoid race-conditions while toggling bits of registers.
The M4 also has a dedicated BSRR register for performing atomic bit manipulation on the GPIO ports,I understand that using this makes the application thread-safe

Is there any downside to this approach compared to the generally used Read-Modify-Write method of toggling GPIO pins.If not, then why are GPIO_ODR registers provided for the cortex-m cores, why not use only the BSRR register for GPIO pin access.


texts: I have an ESC and a brushless DC motor. I am interfacing the ESC to the motor. But I am not getting what I want, so my question is, can I directly connect the motor to the battery without taking the ESC into account?


texts: Can I connect transmitter output to spectrum analyser input directly?

texts:
I have a spectrum analyser, that tolerates 30 dBm 50VDC signal on its input and has internal selectable attenuator up to 40 dB. Can I connect it directly (i. e. without any external attenuators) to transmitter antenna connector, which output I know will never exceed 20 dBm (and 3VDC in case of some extreme failure)?

I know this probably seems as a basic question. By my logic I can connect them directly, but most measurement diagrams I've seen had attenuators in them explicitly, so I want to be sure if I don't need some kind of external load between transmitter and spectrum analyser.


texts: Obtaining dynamic resistance of a zener diode in LTspice

texts:
Please left-click to enlarge

Above is a circuit where:
D1 is a 10V(breakdown) zener diode, V1 is a voltage source which varies from 11V to 5OV DC and R1 is a 1k resistor.
My aim is to identify the dynamic/bulk resistance of the zener diode by using LTspice.

I simulated the circuit such that 0 - 40mA current passes through the zener.
The resulting V-I plot can be seen above.

Lets call Vz is the zener voltage and Iz is the zener current.
What I uderstand from what I read is that, the dynamic/bulk resistance of the zener diode refers to the derivative dVz/dIz when Vz is above the knee voltage.

My questions are:

1-) Can I use this plot to obtain Vz/Iz which correcponds to the dynamic resistance? If so, is there a standard at which current the derivative corresponds to the bulk resistance?

2-) How can I plot the derivative of this plot i.e dVz/dIz in LTspice?

Edit:
DC Sweep:

Please left click to enlarge

When I did a DC sweep, results at 5mA (since data sheet takes 5mA as reference):

dVz/dIz (total dynamic impedance I guess) is 25 Ohm from the above plot. But the data sheet says at 5mA max zener impedance is 20 Ohm.

And the voltage at 5mA Iz is 10.2V in the plot. But the data sheet says nominal voltage at 5mA is 10V.

Is there anything wrong with the way I compare?

data-sheet: http://pdf1.alldatasheet.com/datasheet-pdf/view/71139/LRC/BZX84C10L.html


texts: Question about the current flow and voltages in a simple NAND diagram

texts:
I've so far learned about boolean algebra and its applications to transistors. This is a picture of a NAND diagram:

A NAND has this boolean property : \$ f(A,B) = \overline{A \cap B}\$. What I want to know is how the current is flowing (increasing/decreasing) and the voltages across the collectors. For example, lets say a voltage is applied to A but not to B, then the output which is a load lights up. From my understanding, you need a high enough voltage applied to the base of of a transistor to turn it on and once the base is saturated, you'll have enough current flowing from the collector to emitter. The current on the collector decreases which should mean a low voltage reading on the collector, but this transistor is connected to another transistor. Why is B turned off creating this reading across the resistor?


texts:
I want to know how can i wire this toggle switch to obtain 3 positions :

Position 1 : Turn Off System
Position 2 : Turn On System
Position 3 : Write "High" On a microcontroller (ATtiny84)

This is the slide switch i am willing to use : Link


texts:
I have tried Jasser's solution to toggle LED's using a single transistor at
"Use transistors for controlling two LEDs"

Aim is to use it as a power indicator, using a 3 legged bi-color LED (red=off, green=on), but I fail to see the feasability.

The red and green (separate) LEDS have already been switched and I understand the math to put the right resistors in. This much works!
I'm lost when it comes to the bi-colour LED's common cathode.

Any suggestions? Common anode perhaps? Or PNP?

Rephrase:

In a model railroad I want to be able to choose between a traditional AC transformer (powersupply 1) or digital control (powersupply 2).

The switch (rotation) that I'm using for this has 2 separate channels:

one is used to power the rails,
the other could be used to indicate which powersupply was selected.

I plan to use either +3.3 or +5V DC (not decided yet) to drive bi-colour LEDS (to save space).

I want both leds to always be on (either red or green). A simpler solution to only power the "selected" led wouldn't properly visualise which powersupply was selected in a when in the dark.
Basically, a LED should be red, unless selected (powered) by the switch (=green).

The original scheme worked for me when using separate LED's for red and green, but when I tied the cathodes together to simulate a bi-color LED, powering green did not switch off red. The new scheme works for me!


texts:
What is the pulse width for the mark pulse in an equal mark to space ratio pulse train operating at a repetition frequency of 5 MHz?

The answer is suppose to be 100 ns .But I didn't understand how to get the result.Can someone explain to me how to get the answer? Thanks in advance


texts: Why my register file operates abnormally

texts:
I tried to implement a 32x32 bit register file using Logisim, however once I have finished drawing and proceeded to test it by initializing the content of individuals registers to zero using the reset input, only some of them have reset, others have generated an error.
To clarify I have implemented all the sub-circuits used myself and have tested them individually and they work as required.
So, this is the register file and as you can see some outputs are red:

Each register is implemented in a sub-circuit composed of 32 flip flops D (as in the image shown here).
The supercircuit error is actually caused by errors in one (or more) of the flip flops that make up the register

Going even deeper, analyzing the flip flops that give errors and the relative latches that compose them, the result is the following:
(Note that the clock is enabled although not visible in the screenshots as I am debugging)

I can't explain why some registers and their sub-circuits work correctly while others give this kind of error.
I don't think the error is related to my implementation but I'm not sure if the error depends on Logisim itself (I know it has several bugs and issues).
Any additional information or help is welcome as I personally have not found anything about it by searching the web.


texts:
I received this question as a homework:
"In an RC network with DC source, two capacitors added in parallel will reach a steady state voltage sooner than added same capacitors in series, considering all parameters unchanged. Caps have initial voltages zero. TRUE or FALSE"

simulate this circuit – Schematic created using CircuitLab
Please ignore the values of the Voltages, Capacitors and Resistors in the above two schematics. This is just a reference to show my understanding of the above question. I need to know which schematic would attain a steady state voltage at the respective nodes soon and why?
I have never read about series RC network. Even if that is the case, from where is the output voltage taken?
I do not understand. Can someone help me with a diagram to understand the difference and help me with the answer, please.


texts: In the Arduino IDE, what exactly happens when you choose the 'upload with programmer' option to program via a AVR programmer instead of the USB cable? Does it upload just your program, or does it include the bootloader too? If i previously uploaded the bootloader will it still be there, or does it get overridden? Does it set the fusebits during this process?


texts:
I have a PCB that needs a number of connecting sockets (a mixture of mini-DIN, XLR and HDMI) but real estate is limited.  I was thinking of using the HDMI sockets as a means of reliably getting large number of connectors into a small space (as there are 8 connectors that need to be plugged in and the cables are also cheaply available and don't need to be custom made).

The cables need to be plugged into the PCB vertically (there isn't enough space to get all the connectors along an edge).  I therefore want a vertical HDMI PCB socket.  The unit cost of this connector seems to be much greater than for comparable horizontal connectors.  I can find other connectors that have "wings" on the sides like this:HDMI connector with wings, but these use up too much space.

Has anyone come across connectors such as these? Can you recommend a source for these?  Or have any other ideas?


texts: Does anyone know what are the equations for this oscillator? At the output, I need to obtain a frequency of 1kHz, but I can't find the right equations. Also, my teacher told me to remove I1, but without it it doesn't work, since there is no noise in the circuit, how could I remove it then?


texts: LM358 measured slew rate much higher than spec

texts:
I am measuring the slew rate of an LM358 op amp running +/-15V using both unity-gain (+/- 10V input signal = 2/3 full scale) and 'comparator mode' (+/- 1V input to noninv input, inv input grounded). I've made the measurement in situ as well, with a circuit whose output depends directly on the slew rate. In all experiments, the slew rate of the humble '358 notoriously slow) comes out to be roughly 18 V/us, with a lowest measurement in the range of 11 V/us. I've tested multiple 358s and found the same result. In all tests, the other op amp (dual package) has its inputs tied together, output is open.
TI brand LM358 page is here. SR should be 0.3 V/us typ.; I'm measuring over an order of magnitude faster response.
Datasheet here [pdf]. SR recently updated to 0.5 V/us at G = +1.
In all calculations, a square wave output is measured on a scope, the slew rate is calculated as $$SR = \frac{\Delta V}{ \Delta t}= \frac{V_{end}-V_{start}}{t_{end}-t_{start}}$$
Example calculation: 10x probe measures a rise time (linear voltage ramp) of 1.34us, voltages are -1.36V up to 1.12V, thus
$$ SR = \frac{2.48 \text{ V} \times 10}{1.4\ \mu\text{s}} = 17.7 \text{ V}/\mu\text{s}$$
Now it's perfectly alright with me if the 358 has a faster slew rate. But I had actually hoped for something slower; not only that, but having an op amp be that far out of spec (as a 'typical value' nonetheless) caught me off guard.
Can anyone verify the 358 slew rate? Or explain why the rate is so much faster when I'm measuring it?
EDIT
Image of one of the LM358s I'm measuring.


texts:
I'm working on controlling an incubator by writing commands to its serial port, a 9 pin RS232.  The commands are simple byte strings, such as #02ts.  The incubator responses are similar to the commands I send.  If I connect it to my computer with an RS232 to USB cable, everything works great.

Now I'm looking to control it remotely, and I was told to try a serial to wifi adapter.  I've come across a vast variety of items which claim to do this, and I'm lost when it comes to what each item is suited for, and I have no idea what exactly it is I need.  What is the best way to wirelessly communicate to this incubator's serial port?


texts: How can a transpose buffer be realized in an FPGA

texts: As far as I understand a transpose buffer is where we write data of a nxn matrix as rows and then can read it out as columns of the same matrix. There does not seem to be an IP block to create such an entity. How can such a structure be realized usually? The objective is use in a 2D 8x8 DCT which is implemented as two 1D DCTs seperated by a transpose buffer.


texts:
I'm planning to do a waveform generator using an FPGA board (spartan 6 board from diychips), however I am new to verilog so I am encountering a bit of a problem. I created a sine-wave sequence using MATLAB and imported it into my verilog code. Here's the code that should output the 7 bit sequence :

module dac7bit(input M_CLOCK, output reg [6:0] DAC);
reg[8:0] counter;
reg clk = 0;
reg[4:0] i = 0;

always @(posedge M_CLOCK) begin
    counter <= counter+1;
    if(counter==320)begin
        clk <= ~clk;
        counter <= 0;
    end
end

always @(posedge clk) begin
    case(i)
        5'b00000 :DAC <= 7'b1000000;
        5'b00001 :DAC <= 7'b1001111 ;
        5'b00010 :DAC <= 7'b1011110 ;
        5'b00011 :DAC <= 7'b1101011 ;
        5'b00100 :DAC <= 7'b1110110 ;
        5'b00101 :DAC <= 7'b1111100 ;
        5'b00110 :DAC <= 7'b1111111 ;
        5'b00111 :DAC <= 7'b1111110 ;
        5'b01000 :DAC <= 7'b1111001 ;
        5'b01001 :DAC <= 7'b1110001 ;
        5'b01010 :DAC <= 7'b1100101 ;
        5'b01011 :DAC <= 7'b1010111 ;
        5'b01100 :DAC <= 7'b1001000 ;
        5'b01101 :DAC <= 7'b0110111 ;
        5'b01110 :DAC <= 7'b0101000 ;
        5'b01111 :DAC <= 7'b0011010 ;
        5'b10000 :DAC <= 7'b0001110 ;
        5'b10001 :DAC <= 7'b0000110 ;
        5'b10010 :DAC <= 7'b0000001 ;
        5'b10011 :DAC <= 7'b0000000 ;
        5'b10100 :DAC <= 7'b0000011 ;
        5'b10101 :DAC <= 7'b0001001 ;
        5'b10110 :DAC <= 7'b0010100 ;
        5'b10111 :DAC <= 7'b0100001 ;
        5'b11000 :DAC <= 7'b0110000;
        default: DAC <= 7'b0100000;
    endcase

i<=i+1;
    if(i==24) begin
        i<=0;
    end
end

endmodule

I have created a register DAC that I have mapped in the .ucf file, using this datasheet. The pins are then connected to the R2R DAC outside the board via jumpers. I am not sure if this is the way to do it (to map the pins), I got this idea from how this was done for the I/O board shipped with the FPGA board itself.  Here's the .ucf file:

 # DAC
 NET    "DAC<6>" LOC = P104;
 NET    "DAC<5>" LOC = P101;
 NET    "DAC<4>" LOC = P99;
 NET    "DAC<3>" LOC = P97;
 NET    "DAC<2>" LOC = P94;
 NET    "DAC<1>" LOC = P92;
 NET    "DAC<0>" LOC = P87;

 #====================================================
 # Clock signal
 NET "M_CLOCK" LOC = P123;

However I could't probe anything, all of the pins were high. I thought that the problem might be with generating my own clock signal, or with the case() syntax, so I tried to just assign some 7 bit value to DAC register on each M_CLOCK cycle. Still, nothing has changed. Therefore I think that the problem is with either initializing the DAC register, mapping it, or assigning values to it, however I can't find anything that could help.

EDIT:

The problem was much more trivial than I expected. It was due to the software I was using. I had installed Xilinx ISE on a Windows 8 machine and some of the features (such as producing working bit .mcs files it would seem) were bugged. Once I got to my school computer that runs a working version of ISE the code worked as expected.


texts: How to modify input wires before sending them as input in another modules?

texts:
I want to design a 8 bit adder-subtracter in verilog. when cin is 1, it should add 2 numbers, when 0, it should subtracts.

For performing subtraction, I said to add number1 and ~number2 and 1. here is the code:(when subtracting, cin = 0. so ~cin = 1. and it the 3 values will be added by a full_adder which works truly) this is done for all 8 bits.

`timescale 1ns/100ps
module full_adder(input a, b, cin, clock, output reg sum, cout);
    always @(negedge clock) begin
        sum = #7 a ^ b ^ cin;
        cout = #7 (a & b) | (a & cin) | (b & cin);
    end
endmodule

module adder_subtracter_8bit
    (input [7:0] num1, num2, input cin, clock, output [7:0] result, output cout);
    //1 is for adding, 0 for subtracting

    wire w0, w1, w2, w3, w4, w5, w6;

    assign #3 num2[0] = (num2[0] ~^ cin);
    full_adder ADD0 (.a(num1[0]), .b(num2[0]), .cin(~cin), .clock(clock)
                         , .sum(result[0]), .cout(w0));

    assign #3 num2[1] = (num2[1] ~^ w0);
    full_adder ADD1 (.a(num1[1]), .b(num2[1]), .cin(w0), .clock(clock)
                         , .sum(result[1]), .cout(w1));

    assign #3 num2[2] = (num2[2] ~^ w1);
    full_adder ADD2 (.a(num1[2]), .b(num2[2]), .cin(w1), .clock(clock)
                         , .sum(result[2]), .cout(w2));

    assign #3 num2[3] = (num2[3] ~^ w2);
    full_adder ADD3 (.a(num1[3]), .b(num2[3]), .cin(w2), .clock(clock)
                         , .sum(result[3]), .cout(w3));

    assign #3 num2[4] = (num2[4] ~^ w3);
    full_adder ADD4 (.a(num1[4]), .b(num2[4]), .cin(w3), .clock(clock)
                         , .sum(result[4]), .cout(w4));

    assign #3 num2[5] = (num2[5] ~^ w4);
    full_adder ADD5 (.a(num1[5]), .b(num2[5]), .cin(w4), .clock(clock)
                         , .sum(result[5]), .cout(w5));

    assign #3 num2[6] = (num2[6] ~^ w5);
    full_adder ADD6 (.a(num1[6]), .b(num2[6]), .cin(w5), .clock(clock)
                         , .sum(result[6]), .cout(w6));

    assign #3 num2[7] = (num2[7] ~^ w6);
    full_adder ADD7 (.a(num1[7]), .b(num2[7]), .cin(w6), .clock(clock)
                         , .sum(result[7]), .cout(cout));

endmodule

however, this isn't work properly and the outputs(which are wires showing the result) are all X.

testbench:

`timescale 1ns/100ps

module TEST_adder_subtracter_8bit();
    reg [7:0] a, b;
    reg clock, cin;
    wire [7:0] result;
    wire cout;

    adder_subtracter_8bit UUT(.num1(a), .num2(b), .cin(cin), .clock(clock),
                          .result(result), .cout(cout));

    initial repeat (2000) #7 clock = ~clock;

    initial begin
        a = 8'b0000_0000;
        b = 8'b0000_0000;
        clock = 0;
        cin = 1;

        #180;
        a = 8'b0000_0001;
        b = 8'b0000_0001;

        #180;
        a = 8'b0000_0111;

        #180;
        a = 8'b0000_0001;
        b = 8'b0000_0111;

        #180;
        a = 8'b0001_1010;
        b = 8'b0001_0011;

        #180;
        a = 8'b0000_0001;
        b = 8'b1111_1111;

        #180;
        a = 8'b1111_1111;
        b = 8'b0000_0001;

        #180;
        a = 8'b1111_0000;
        b = 8'b1111_0110;

        #180;
        a = 8'b0111_0011;
        b = 8'b0111_0111;

        #180;
        a = 8'b1111_1111;
        b = 8'b1111_1111;

    end

endmodule

Can anyone say how should I fix it?


texts: If a circuit only has a current source and no voltage source where does the voltage come from to supply the circuit?

texts:
For example this circuit, A current source is something with would alter the voltage across it to meet a certain current.

But where is there a voltage source to do this or even have a voltage at Vx. How is this circuit functioning without even having a voltage supply?

I have looked here : Is current source also a voltage source?

To try to understand the difference between what a current source is and a voltage source but nothing helped answer this question.

Could in this case the current source act as a voltage supply?

Thanks


texts:
I was tryig to build this circuit ("Series-feedback pair") from "Art of electronics" book (p. 150).

Since I do not have the exact components I tried to model it in LTSpice with what I have and ended up with this circuit (the resistor have non-standart values as I will anyway will have to adjust them upon trying this out on the breadboard), where the darligton pair I added when I could not achieve the desirable level of open-loop gain:

Although this circuit does the job, but to achieve the desired performance I had to fine tune by hand some resistor values. For example when I change Rs to 500 Ohm or 3kOhm the circuit does not work anymore, clipping either for positive swing or for negative swing.
And also, since I was building it stage-by-stage, after adding a feedback, the operating point had shifted significantly, so I had to readjust it almost from scratch.
My question is:
Is there a more-or-less standart procedure for designing such or more complex feedback circuits or is the manual tweaking the only way? Since when complexity would increase these adjustments will take quite a bit of time.
I tried to google about it for a while, but could not find any description, other than for simple CE amplifiers.
Thank you in advance.


texts: What's the difference between Clamper and Rectifier

texts:
I have a doubt that instead of rectifier we can use positive clamper to get the DC voltage at output, because the clamper adds the DC voltage to the AC signal, but even the same thing is done by the rectifier.

So can you please explain why can't we use the clamper for outputting DC from AC?


texts: When does the stack pointer get copied from flash to SP on startup?

texts:
I'm trying to track down a problem on a MKV31F256 micro.  The firmware immediately jumps to the hard fault handler on startup.

I'm able to set a breakpoint on the first assembly instruction in the reset handler and look at memory and the registers, and I was surprised to find the stack pointer was not set to the top of RAM (0x20008000).  Rather, SP is set to 0x00000000

However, the initial stack value is correct in the vector table.

I was under the impression the Cortex M4 automatically loaded the first and second entry in the vector table into the SP and PC registers.  Is this not the case?

I double checked on a different Cortex M4 micro (nRF52832) and SP is set correctly by the hardware on startup.

Is the automatic SP initialization an optional feature by the individual chip manufacturers?


texts:
I have a hard time to understand why two different opamps in a substractor configuration deliver highly different output in a TINA simulation.
At the end I try to implement a high impedance differential aplifier (instrumentation amplifier), which second stage is a subtractor, and I got very different result with different opamps in simulation.

So I first read some basics here: http://www.ti.com/lit/an/slyt213/slyt213.pdf.
They explain an instrumentation aplifier as well as simple substractor and in regard to the later there is a formula for Vout which contains only the values for input voltages and external resistors.

So I think then, the particular opamp model does not matter at all for this configuration and DC operation.

Now in TINA I made a DC operation point simulation, for an ideal opamp, for TL082 and for LM7321. The schematic shows my configuration.

simulate this circuit – Schematic created using CircuitLab

Now with an ideal opamp I get the correct 50mV at the output, with LM7321 and 9V supply I get something around 45mV which I suppose is stil OK, but with TL082 there is 1.52V at the output (but the circuitlab simulation results in exactly 50mV). What do I miss? Is it a buggy spice macro in TINA or is there something else in TINA or in the datasheets I should consider or am missing?

I would like to use TL082 because its cheap and I have already some in stock bought as "general purpose opamp".

Please educate me a little :-)


texts: Small ICs pitch and Oscilloscope probing

texts:
I have a STM32L432KS circuit with this 0.5mm pitch UFQFPN32 package:

I have to take a look at some pads but with which kind of oscilloscope probe could I use?


texts:
I'd like to use the below circuit to protect my device from overvoltage.

simulate this circuit – Schematic created using CircuitLab

D1 is rated to 15V. SCR1 is supposed to be ON Semi MCR100-8G with maximum current of 800 mA. F1 supposed to be rated at 0.5A in order to blow below maximum rating of SCR1.
So my question is, can I place fuse to F1 position? All schematics I've seen had fuse in place of F2. I want to omit it, and use only F1 instead.
Also, should I add some resistor between D1 anode and SCR1 gate? If yes, how to calculate its value?

Thanks to @rdtsc who noticed a very silly mistake of mine. Obviously the only possible place of fuse is F2. So now the question is:
Provided that SCR1 has maximum current rating of 0.8A, and maximum surge current of 10A, can I use F2 with 3A rating?.


texts: Is the zero sequence component considered balanced?

texts:
how is the zero sequence component is balanced while the three vectors are inphase and not displaced from each other by 120°?
Isn't the definition of a balanced system is one in which the magnitudes of all phases are equal and are spaced out by 120°?
The confusion came from the book below:

The source:
Electrical Power Systems
By
C L WADHWA
2012 by New Academic Science Limited
ISBN : 978 1 906574 39 0


texts:
What are the main advantages from a theorical point of view of a Heterodyne transmitter versus a Homodyne Transmitter?

I've seen the main difference is the VCO or PLL connected to the Mixer after the Modulation/Demodulation phase to take the modulated signal to RF frecuencies for the antenna.

If would be possible to take the modulation signal directly in RF frecuencies taking a high Carrier Frecuency, wouldn't be a easier choice?


texts: Will the 595 shift register burn out if outputs are always high?

texts:
I'm working with a SainSmart 8-Channel Relay Module and I'm powering it via a 595 shift register via raspberry pi. The issue I'm having is that these sain boards activate the relay when the input is low and deactivate when high so essentially I have to turn the output high to turn the relays off and vice versa.

My question is whether or not this setup will cause long term issues with the pi or shift registers since the relays will be off the majority of the time. If so, what needs to be done to prevent issues?

I'm powering the shift registers via external 5v 1a source, not from the pi.


texts: Phased array receiver circular polarization

texts:
In a phased array system, what will have to change in a receiver's architecture if it needs to work for both linear and circular polarization?

I saw in one article it is said "Supports automatic circular polarization control by embedding 0o/90o phase controllable phase shifters" source:(http://www.satixfy.com/beat/)

Can anyone please explain me why they used the phase shifter?


texts: What makes a motor to run in its rated power?

texts:
Why does a motor tend to work on rated power always? (I have a series of doubts one by one I am planning to clear).

ustpower mentions

  A low voltage forces a motor to draw extra current to deliver the
  power expected of it thus overheating the motor windings.

Why does it force to make a motor run in the rated power even at low voltage? How does a motor know what's it's rated power at low voltage?


texts: How do these diodes prevent opamp from saturation?

texts:
I cannot understand how the clamping diodes prevent opamp from saturation when the switch/FET is off in the following sample-and-hold circuit:

I only know that if the negative feed back of an opamp is broken it easily saturates to one of its supply rails due to even a nV difference at the inputs.

But in this case diodes are preventing such saturation eventhough the feedback is cut when the FET is off.

Can this be explained in an easy step by step manner since I have found some very short info but dont get it.


texts:
On my STM32F769I Discovery board I tried BlinkLED example, using Eclipse IDE (xPack toolchain, OpenOCD, ...). Debugging fails when frequency was adjusted (original code) to 192 MHz (later on boosted in the example).
The code line where debuggers fails is moment of writing to RCC_CFGR register.
When I change frequency to 96 MHz (the only line I changed), debugger successfully passes the line mentioned and proceeds to "main" function.
The board has supply from my laptop's USB output (no external supply).
What could be the culprit of such behavior ?


texts:
I have AC/DC 3/6/12V out universal adapter with two pins (without earth connector) and would like to use it for powering my arduino project and playing with oscilloscope. Knowing that my oscilloscope will make big bang if power supply is connected to main earth ground, I would like to test somehow if some of the AC 220V wires are connected to main earth ground.
I know that my AC/DC is safe because of plug type but how to know that somewhere in the system main earth ground is not connected to phase or neutral.


texts: What is actually meant by derating of a generator and what are the factors to be taken into considerations for derating a generator. Also what are the methods involved in derating a generator and what are the counter effects when derating is not done properly ?


texts: What is a good circuit design to drive this relay safely from an ESP32?

texts:
I have this relay module : https://www.amazon.co.uk/gp/product/B06XKQQXKW/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

I want to drive the 8 control pins (driving low at 3.3v) from the ESP32. I believe that each pin needs 70mA according to this datasheet:http://datasheetcafe.databank.netdna-cdn.com/wp-content/uploads/2015/10/SRD-05VDC-SL-C-Datasheet.pdf.

The relay is a SRD-05VDC-SL-C which I believe correlates to a 5v high sensitivity coil. That means each pin will draw 70mA to drive the coil, obviously this is way beyond the spec for the ESP32. Except this relay board is being driven by an optocoupler, so I am not sure if this is the current i am supposed to be looking at.

How can I drive this safely using normal cheap components, as doing so directly from the device would be pushing its current limitations. I understand a NPN transistor will likely be involved, however I am not entirely sure of the safest, best way to proceed. Please help by example of a circuit.


texts: I'm trying to build an instant or zero 2 pole switch (DC current). Basically what I'm trying to accomplish is that when the switch is powered off, the lines are connected like shown in the first picture (The color of the same circles displays the connected sides). When you turn on the switch, the lines are connected like in the second picture. The closest thing that I found out is a solid state relay due to its high-speed switching time. I need the high-speed switching time, as the device on the other end isn't allowed to turn off or reboot.


texts: Sample and hold circuit giving distorted output

texts:
I'm making a sample-and-hold circuit for a 3 bit Flash/Parallel ADC and to allow the conversion to have enough time to happen I want to maintain the input voltage steady for the duration the conversion will take. I intend on sampling an audio signal from a phone or mp3 player.

I'm simulating the circuit first and I'm having some trouble with the output from the sample-and-hold part.

I'm using the LM358N opamp for the buffers and an IRL520 NMOSFET to switch. The opamps are on dual 9V, -9V supply

To switch the MOSFET, I'm using 0 and 9V signals at 1kHz and the input signal to the buffer is a 6V peak to peak sine wave at 500Hz.

Ideally, the output should be a staircase looking waveform but with my holding capacitor at 1uF the signal is distorted.
This is the scope output at 1uF.

I've tried quite a few different values for the capacitor to little success.

I initially thought it was due to the switch resistance forming a low pass filter with the capacitor but it Rds is pretty low (0.18 ohms).

My question is why is this happening and how do I solve it. I know I'm a bit new  to asking questions here so if there's anything useful I've left out please let me know.
I'd really appreciate any help in solving this.


texts: Unknown voltage in IR pulse sensor circuit

texts:
I've build a simple circuit based on the sketch from here: http://makezine.com/projects/ir-pulse-sensor/

simulate this circuit – Schematic created using CircuitLab

However, after connecting everything I have strange readings on output. It is all the time value around 60mV. I've been thinking that maybe this is the IR from sun light, but after covering receiving diode with aluminium foil which is meant to block IR light it is still around 60mv on output.

On the attached circuit I've marked places where I measured voltage and the outcome values. Can someone please tell me where can be mistake?


texts: A doubt on interfacing EMG circuit to Arduino?

texts:
So I have done an EMG detection circuit using TI's instrumentation amplifier chip INA128 as below (sorry if the schematic looks bad):

And the circuit is working OK for my requirements (although slight hum and background noise is there). I was trying to interface the V_out to the ADC of Arduino. Which interfacing circuit would be better for this purpose? I was trying the instructions given here using op-amp summing amplifier solution. I used LM741 op-amp in my circuit. But it was a failure. My output signal V_out varies between -100mV to 100mV.


texts: Does a Connector With Multiple GND Pins Make a GND Loop?

texts:
There are some cable standards that have multiple GND pins on the connector proper.  A good example of this is the SATA connector (it has 3 of them).

In reality, each GND pin has a slightly different impedance, due to varying factors: connection quality, cable quality, cable age, etc.

Wouldn't these mismatched impedances form a GND loop?  Wouldn't it be better to have a single GND pin (of larger gauge if more current is needed)?

And if it is a GND loop, why are cables wired this way?


texts:
I was wondering what is the name of this component, it really doesn't really have a part number, or anything similar so my research has really gone down to a low.  Researching silver disk thingy does not help either.

I found this part in a microwave, as well as in an old CRT TV, along with a bunch of other good parts.  What is the name, and purpose of this component?


texts: Xbee series 2 - router or end device firmware?

texts:
I am using multiple XBee Series 2 nodes in my home automation setup, however, I seem to be seeing unusual delays in packet delivery (around 1 or 2s). I have a single coordinator module and multiple routers in the network.

I was wondering, how well does the mesh protocol work? If multiple of the routers are in close proximity, does it actually slow the mesh down? (by close proximity I mean between 3-5m). My rationale was to use router firmware for all my devices as they are not power-constrained and I thought it would be better to have routers - is that the case?

Shall I have the router firmware only on the nodes that really need to be used as routers and flash the rest as end devices even if they are plugged into the wall?

Lastly, the delay has slightly increased when I enabled encryption.

UPDATE

System details:
Room 1 - Xbee coordinator conncted to Raspberry PI via 56700 link
Room 1 - Xbee router used for direct actuation
Room 2 - Xbee router used to communicate with arduino @ 9600 link
         (commands fit into a single packet)

I am not using any broadcasts, all of the routers are AT and have DH/DL set to communicate with the coordinator and the coordinator using API mode to communicate to the main controlling software.

Lastly, is there any time needed for the mesh to initialise? Or is it done ad-hoc? Is that information stored on Xbee reboot?


texts: Atmel Software Framework. Confusion with USART example

texts:
I'm trying to get the following basic USART example working on a SAM4S:

http://asf.atmel.com/docs/3.4.1/sam4s/html/sam_usart_quickstart.html#usart_basic_use_case

I am using a custom PCB board with a SAM4S16B MCU on it.

After setting up my project in Atmel Studio as instructed and attempting to compile, I am getting a number of errors of the form:

Error   4   'PINS_USART_MASK' undeclared (first use in this function)   C:\Users\Nick\Dropbox\Uni Work 13\comms\comms\src\main.c    94  5   comms

My question is wondering whether the following lines are placeholders that expect something else to be substituted in the define values?

#define USART_SERIAL_PIO             PINS_USART_PIO

#define USART_SERIAL_TYPE            PINS_USART_TYPE

#define USART_SERIAL_PINS            PINS_USART_PINS

#define USART_SERIAL_MASK            PINS_USART_MASK


texts:
I'd like to make a 2-channel audio mixer. I'll connect one of the entrances to my phone with an aux cord. I'm going to put my headphone mic on the other one. I'll also connect a potentiometer to both channels separately and adjust the volume. I'm going to combine these two channels into one channel and connect the output output to my computer. My goal is to record audio on a computer. Is there a circuit diagram that has the properties I want? I would be glad if you send. Thanks.
EDIT: For example, this scheme seems to have exactly what I want. But if it works I'm not sure. Do you think I should try this?


texts: generator coils: max power given wire gauge

texts:
I've been messing around with some neodymium magnets and magnet wire to make a generator. I've rotated my rotor as fast as I could and noted the no-load voltage. I wondered if (at this current speed) I could define a maximum theoretical wattage based on the wire gauge.

If my generator produces Vmax on a certain gauge wire, that gauge wire has a maximum current rating before it melts, so the maximum power would be Vmax * Imax?

I know there are a lot of factors that define whether or not the generator could actually, but having a theoretical max could help set some expectations.

My question is: Is this the right way to calculate the theoretical limit? I'm not sure if the power can actually go a bit higher due to coil resistance and inductances and such, so I figured I'd ask.


texts: Who receives the value returned by main()?

texts:
I know that in computers, value returned by the main() function is received by the operating system.
But, what happens in the main() function of a microcontroller?


texts: How much current can I draw from one of the output of a transformer

texts:
I have a flyback transformer which I took off the shelf.

It has 6 outputs:

4 at secondary side and
2 (+1 input) at primary side.

I'm able to approximately know consumption of each output.

How much can I draw from each output?

I think that each maximal output current is function of the other maximal output current.

Does it depend on how each  output contributes to saturate the core?

If you have any documentation about this subject, I would be really thankful.


texts: Fixing old CRT oscilloscopes... what to look for first?

texts:
I've been amassing a pretty large collection of these old scopes, and it's about time I got to trying to fix them.

About half of the ones I run across and buy don't have traces. I don't need to get them in perfect working order again, but I'd at least like to get a trace on them. So what do I look for first?

I know resistors' values change over time, and the capacitors are big culprits, right? What about CRTs? Do they just "go bad" from sitting for 50 years? And what about the transformers? I can't really see a transformer just going bad, because you'd have to somehow manage to break one of the windings in it, correct?

Anyway, thanks a heap for the help.


texts: How to best connect a temperature sensor to an aluminum block?

texts:
2 questions:

How would you connect a temperature sensor to an aluminum block? Could I use a thermal adhesive, basically just gluing the sensor to the block?
Which sensor would you buy? I like the nice cables of the waterproofed versions, but I'm thinking the plain sensor is maybe better suited to gluing to the aluminum block?

DS18B20 Digital temperature sensor + extras
Waterproof DS18B20 Digital temperature sensor + extras
High Temp Waterproof DS18B20 Digital temperature sensor + extras

Background:

For our DIY PCR project we need to continuously measure the temperature of an aluminum block. The temp. range will be from room temperature to around 100 °C. From what I have read I understand that we need a digital temp. sensor, because the Pi does not have analog inputs (not without additional extensions anyway).


texts:
For Preamble detection and postamble closure for a memory interface controller , could anyone explain how the following Figure 4 , Figure 5 and Figure 6 work together to sample (or capture) the incoming DQ signal during DDR read activities ?  Should dqs_rg_in be fed to parallel (instead of series) posedge-triggered and negedge-triggered register ?

Delaying the incoming strobe for READs is more involved and will be covered in detail in an independent technical note. <-- Do anyone have idea on which exact independent technical note it is referring to ? I suppose for READ preamble, DQS is aligned with DQ , so why need to delay the incoming DQS strobe ? If it is due to DQS setup timing requirement for sampling DQ signal, then how would I implement the slight delay in verilog coding implementation ?


texts: Use HM-10 (Bluetooth LE) or ESP8266 for telemetry

texts:
I am in the process of building a quadcopter, and I would like to send the telemetry from the device to my laptop wirelessly (wires are very inconvenient for debugging!).
I have several HM-10 BLE modules.
What attracts me in BLE is that it is fully supported by iOS, Android, Macs and modern PCs.
However, it looks like it is very slow (the original HC-10 module has default speed set to 9600), and from what I understand, the data packet is limited only by 20 bytes (so the telemetry data must be sent in binary, plus we cannot feed it much info, especially if it is in a floating point format)

Has anyone used these modules for sending telemetry information? Is it reasonable at all?

The only other option I have currently is ESP8266 module (I have esp-link firmware), which seems to be much faster in transfer speeds according to what I've read, but it seems to take a long time to boot (my MCU has already "started" and sending data, but the ESP is still connecting to the Wifi access point), plus it doesn't work "in the field" where there's no Wifi access points.

Thank you in advance for your suggestions!


texts: How can I get ground from a NEMA 5-15R wall socket without electricity?

texts:
I have some network equipment that I want to connect to ground (they come with 2-prong wall wart PSUs and have a separate screw hole for a grounding pigtail) - but where would I get ground from in a regular home?

For me, the obvious choice would be an existing wall outlet (regular USA 120V 15A NEMA 5-15R). But I don't need the 120V, I kinda just want to get the ground, connect it to a copper grounding strip or bus bar, and then connect grounding pigtails to that.

If that is sane, then I wonder: How would I get the ground out of the wall socket? I guess I could just jam a banana plug or something into the grounding hole, or cut open a power cable and make sure the +/- electrical plugs aren't connected. But that seems hack-ish and dangerous.

But there also don't seem to be "simple" NEMA 5-15R-ground-taps available (kinda the exact opposite of this), which makes me wonder if a) this approach is actually the correct one and b) whether there might be a much simpler/better way to get ground from somewhere in a regular home. (A non-corrosive steel post outside isn't an option really here, no good way to run a wire into the room)


texts: What is time constant for this UC3845 circuit?

texts:
Time constant tau=R*C=100 (us) Am I right??
How to get relation equation about V_ref and V_c?
me:

Am I right?


texts:
I have a board I salvaged from a joystick that uses potentiometers to measure the location of the arms. On the PCB a edge pin and the center pin are wired together. I would like to connect the pots to my arduino, but I can't figure out how to connect it properly. This is the basic circuit I have right now.

The question: how do I wire this up to receive a meaningful value when the pot is rotated?


texts: Parallel charging of lipo batteries, maximum voltage difference?

texts:
There are numerous products that enable lipo batteries to be charged in parallel.

Most sources are clear on voltage and capacity requirements, which follow pretty directly from basic circuit calculations:

batteries must be same number of cells
mAh capacity of batteries can be mixed

One area of confusion is how much the batteries can differ in their voltage; a commonly cited value is 0.3V, but many different answers have been provided.  Some of them are from quite old forum postings, so the answers may have been correct circa 2005-2006 but superseded by newer technology.

So, how much can voltage differ between two lipo batteries before it is inadvisable to charge them in parallel?


texts: Avalanche relaxation oscillator biasing resistor

texts:
I've tried the circuit in this article. It works very well and I've obtained 2ns clear pulses at 150 V (the main issue was to find the right avalanche voltage, which turned out to be 150-160V for my 2n3904 transistor).

While the basic principles of operation in this circuit is clear for me, I does not fully understand the role of the resistor R3. In what sense is it supposed to "bias" the transistor?

Also, is it possible to use a TVS or another avalanche type diode in place of the transistor?


texts:
I would like to add a !(SLEEP) line for this CMOS oscillator in a way that in case of low input on !(SLEEP) line, the output PWM line is constant low.

2 questions for the circuit:

In this case do I need to use Schmitt trigger for the AND gate?
Is there a simpler, more professional way to achieve this?


texts: How can I change the frequency of my ATmega168?

texts:
I'm completely new to MCU programming. I have an ATmega168 and a 20 MHz oscillator.  My question is, how can I "tell" the controller to use this oscillator? I tried to read the datasheet, but that didn't help a lot!

My guess is that I should set the "fuse bits"!

Is it possible that I use this oscillator and run the controller with a lower frequency  say 16 MHz?

By the way, I'm using Atmel Studio 6 to program this.

UPDATE

After dextorb's comment, I've uploaded this image:

In the datasheet Table9-5 they say that for a 20MHz frequency range CKSEL3..1 should be 011! Where can I put this value and after setting it, does it mean that I'm good to go with 20 MHz?


texts: Output from radio feeding both a speaker and microphone input

texts:
I am trying to connect the output from a radio both to a speaker and taking the same signal and inputting it to the microphone input on a computer. The radio has no internal speaker, just a jack to feed an external speaker. The problem I am having is that the external speaker (required) is acting as a microphone and any noise near the speaker is also being fed into the computer. I need to isolate the speaker from the mic input. Also, the signal needs to be attenuated because of the strength. Any help would be appreciated, as everything I have tried, has not worked.

Bob


texts: Implications of INL on the accuracy and resolution of an ADC

texts:
I was trying to understand the meaning of various specs given in a typical ADC datasheet, and I came across this article. Now, if I understand correctly, it seems to me that the accuracy of the ADC in bits can be taken as \$n - \log_2{{e}}\$ bits, where \$n\$ is the number of output bits of the device (its resolution?) and \$e\$ is the INL (integral non-linearity) error in terms of LSB.

My questions are:

Is my understanding correct? If not, what is the correct explanation?
If a 16-bit ADC has a INL of \$\pm 4\$ LSB, can we say that the accuracy of the ADC is 14-bit, and will have to ignore the lowest 2 bits for most practical purposes?
Here is a 16-bit ADC with a typical INL of \$\pm 0.4\$ LSB. Does this mean the device has a typical accuracy of more than 17-bits? How is this possible? Or does it mean the device typically has an accuracy of over 17 bits, but since it has only 16 output bits, it has to truncate the data to a lower resolution?


texts: How does internal capacitance affect an electret microphone?

texts:
I'm evaluating two different high sensitivity, low frequency microphones from the same manufacturer.  They are the same part with a differing internal capacitor, but I'm not provided an internal schematic so I'm not sure what the drawing/datasheet means by internal capacitor, and how that affects my project.

The following part has an internal capacitor listed as 33pF:

http://www.puiaudio.com/pdf/POM-2245L-C33-R.pdf

While this part has an internal capacitor of 10pF:

http://www.puiaudio.com/pdf/POM-2245L-C10-R.pdf

Are these connected across the microphone contacts, or elsewhere in the internal microphone amplifier? Or is it descriptive of a microphone parameter rather than an additional component part of the microphone?

I'm looking to measure low amplitude, low frequency sounds (5Hz-100Hz). What will I find different in practice between the two microphones for this purpose?


texts: Why is the arrow on this MOS transistor IC common?

texts:
The schematic below is of a CD4007 MOS transistor chip.
From the schematic it can be seen that on either side, PMOS or NMOS, the arrows indicating what type of MOS transistor it is are all connected to a single pin - pin 7 for the NMOS side, and pin 14 on the PMOS side. In this case, pin 7 is a source and pin 14 is a drain.
Why is that? Does anything need to be connected to those pins to use the other transistor in the chip?


texts:
I have a question about Bandgap Reference circuits.

How did he get Vt*ln(n)?? This is how I did it:


texts: If the output of the 555 timer is not trigger to high, is it ground? Or is the output left floating?


texts: Relationship between clock skew (For Reg-Reg path) and minimum clock pulse width requirement for capture Flop

texts:
I am hoping if some expert in timing analysis could answer on this topic.

Here is the question:

I am creating a liberty timing file for an IP block using ETM (Extracted Timing Model) method. Accordingly, I have the min_pulse_width parameter for my clock pin extracted by the tool using this ETM method (I input Verilog netlist and SDC to the tool for this extraction).

Tool documentation says that the parameter "min_pulse_width" is extracted for the clock pin using the following formula -

MAX(Arrival time at launch flop - Arrival time at capture flop + min pulse width of library cell) -- for all the paths in the design.

This means there is a relationship between clock skew at a REG-REG path and the min pulse width of my capture FF cell.

I want to exactly understand how they are related ? Can someone give an intuitive explanation for why the tool would extract min_pulse_width for clk pin this way and also talk about relationship between clock skew and pulse width ?

Thanks ,


texts: Lithium Battery Protection Circuit - Why are there two MOSFETs in series, reversed?

texts:
I was studying a battery protection chip and reference circuit (below) commonly used in cell phone Li-ion batteries, and am confused by the two MOSFETs in series on the negative terminal EB-.

According to this question, I now understand that MOSFETs can conduct in either direction S-D or D-S.

My questions are:
1. Why are there TWO MOSFETs in this circuit? Why not just one?
2. If they conduct in either direction, why are FET1 and FET2 installed with opposite polarities?  How does this benefit the circuit?


texts: What phenomena does "Coherence Bandwidth" explain?

texts:
Could anyone please provide a simple explanation of what Coherence Bandwidth means, and how is that related to Delay Spread.

I read some articles but they don't help me to form the relation between the two concepts. I know that the Delay Spread is something which occurs when we have multipaths. Whereas, the Coherence Bandwidth describes the "stability" of the channel in terms of frequency.

Please correct me if there are errors in my understanding and question.


texts: I am trying to make a prototype receiver based on HCS500 Keeloq decoder IC. However, I'm not sure what to feed with RFIN pin? Should I just put antenna or data from standard ASK/OOK decoder, which gives data bits already demodulated? Datasheet doesn't tell much about that part, so if anyone know how to deal with input part or got reference schematics for it I would appreciate it.


texts:
I need to find a way to make an on/off proximity detector triggered by a magnetic field, fitting in a small space of about 5mm ^ 3, and connected to the board by only 2 wires. I know a could use a reed sensor but I would like to avoid using it because as far as I know, it is not widely used in industry. I would like to know if it is possible to do the same using a Hall sensor like this one AH182.

Here is its block diagram

I spent some time learning how Hall sensors work and it seems possible to do what I want using a simple voltage divider like this (Vcc is a +5V regulated power supply).

This sensor has an open collector NPN transistor, so if no magnetic field is detected then no current can flow through the output, and therefore the sensing voltage is about equal to 0 (R2/(R1+R2)*Vcc). On the contrary, if a magnetic field is detected, the current can flow through the output and the sensing voltage is equal to Vcc, while making sure that the output current does not exceed the maximum rating current of 10mA.

I doubt it is as simple as that because otherwise, I don't understand why special type of Hall effect sensor for 2 wires applications exist, like this one MLX92241. I would like to avoid such application specific device if possible, for the same reasons I mention about the reed sensor.

Thanks in advance!


texts: I accidentally selected the wrong clock in atmel studio (8-12MHz RC Oscillator instead of 8MHz crystal) and I'm trying to figure out how I can un-brick it now. I have an arduino on hand and a friend told me I can use that to simulate an RC oscillator. However, despite what I've tried, I have not been able to get it working. I've tried a wide range of baud rates, but I don't know where to go from there.


texts: I'm not sure if this question is appropriate for the forum: I'd like to make up some male to male stereo leads with a 3.5mm jack at each end. The only assemble-yourself ones I can find are pretty fat. What I'd love it a self-assemble plug that's slim like the iPod headphone jack. Anyone know where to get them?


texts:
This is a pretty open-ended question intentionally. :-)

All of the soldering I've done to this point has been with through-hole components. I hope to move up to some smaller surface-mount parts at some point in the future.  I've got a Weller WES51 soldering station that came with a "screwdriver" tip (ETA, I think) that's starting to feel a bit like working with a sausage as my skills (incrementally) improve.  There is a large number of ET series tips available.  How do I choose the right tip for the components I'll be working with?


texts:
I have a question regarding the following circuit:

simulate this circuit – Schematic created using CircuitLab

This circuit gives 30V to the output when the clock input is HIGH, and gives near zero when the input is LOW. But how does this make that exactly? I have trouble in understanding how M1 can put nearly 0V when CLK is OFF.


texts: Providing fusing for motors if system is protected by a fused disconnect?

texts:
So I was told that at the site of install the customer is providing us with a 30A fused disconnect so we can run 3 motors for our machine (2× 5hp ones (non simultaneous), and 1x 3hp one which can run when one of the 5hp ones runs)

Here is my question

If the circuit is fused up stream via the 30A disconnect would you still need to fuse all the 3 motors with their required fuse sizes at 480V? So in this case the 3hp would get a 6A fuse slow blow , and the 2x  5 hp ones would get 10A fuses.??


texts: Measurement of highly resistive samples with Keithley 2182a nanovoltmeter

texts:
In our laboratory we are measuring transport properties of various materials. Currently we have deployed Keithley 2182a nanovoltmeter.

When measuring bulk mineral (tetrahedrites, Cu12Sb4S13 Peru) samples with high resistance (over 10^5 Ohm below 20K), the measurement seems to react as if we measure a capacitor, when the sample is electrically connected to the grounded chassis of the measurement cell. On the other hand, we measure a sawtooth signal, when the sample is electrically insulated.

For clarity sake we have tried to do the experiment only with a 10^6 Ohm resistor connected directly to the nanovoltmeter (original LEMO connectors, copper clips), so the diagram can be reduced straight to resistor connected to the voltmeter. The resistor naturally should not produce any voltage.

We have also observed, that duration of the measurement in number of power line cycles strongly affects the result. With several repetitions of measurement step the result looked somehow like this:

The voltage measured with different measuring times, reproducible with both samples in experimental cell and resistor connected directly to the nanovoltmeter. Inset shows the sawtooth signal we obtained with samples with highest resistances, when properly electrically insulated.

Does anybody happen to know, what are we measuring? (This question is out of practical purposes, the nanovoltmeter is purposed to measure low resistance samples, but it would be nice to know some background anyway)


texts: Adding offset before second order active filter

texts:
Since i wont be able to provide negative voltage to the negative power rail of the OPAMP, i wanted to give my signal a slight positive DC offset and execute the amplification process in the positive region. Since capacitors in the filter circuit might as well serve as coupling capacitors, i am really confused about where to put the dc offset voltage divider. The setup below is supposed to filter signals below 130 Hertz and amplify the signal ten times but does neither. Any idea on how to make the design work is appreciated.

Op-amp datasheet


texts: USB 3.1 Type-A Legacy Connector to USB 3.1 Type-C

texts:
I am unsure of how to design for the following arrangement, any input would be greatly appreciated:

Computer [USB Type-A Connector] -> USB Type-A to USB Type-C Cable -> Custom PCB [USB Type-C Connector] -> HD3SS2522 MUX (http://www.ti.com/lit/ds/sllses1c/sllses1c.pdf)

As the computer uses a USB Type-A connector, the USB Type-C specific lines are missing (SBUx, CCx). As far as I understand, the MUX uses the CCx lines to determine the cable orientation and route accordingly. Without these lines, how would the MUX be able to know the cable orientation?

Thanks!

EDIT:

I missed the part of the USB Type-C Specification which refers to USB Type-C to USB 3.1 Standard-A Cable Assembly Wiring (Table 3-12). It  states that a pull-up resistor Rp (56KOhm) is used on pin A5 within the USB Type-C plug. This will set the source advertisement as "Default USB Power" and also allow the MUX to detect the cable orientation.


texts: Adding a ferrite bead to source of mosfet (smps)

texts:
We are designing a SMPS (ultra low noise) based on TI schematics http://www.ti.com/lit/df/tidrgc2/tidrgc2.pdf (5V, 15W quasi resonant)

In order to reduce EMI (we have some ringing across Mosfet when its turned off) we added some ferrite beads before the R4 and R5. (330 mA, 600R/100MHz, 480mOhm DCR)

Of course we modified the R4 and R5 (we subtracted the R of the ferrite bead). We also added a FB on gate of mosfet (same specs).

However while ringing decreased substantially , every time we push to 15W (load) our unit goes bad. It works fine at 5 W.

I read that inductance on the mosfet source is a bad thinng in SMPS. Can it be the root cause (inductance of the FB)? Am I missing something?

update:
We removed the ferrite beads as instructed. Will try a different approach.


texts: For a CAN bus application, is it correct to connect an ESD protection IC to GND, or chasis of the device?


texts: How fast should I feed 74HC164 for driving LEDs?

texts:
I want to ask about bitrate for 74HC164. I want to drive LEDs with it.

Circuit will be similar to this:

How fast CLK rate / bitrate can I use in this circuit? I know that LEDs have some capacitance.


texts: How to prevent single rail ampliier power-on pop sound?

texts:
I would like to build a 9V battery powered microphone pre-amplifier and I'm encountering a design problem which I don't know how to solve:
I have an opamp that serves as main amplifier which is powered by the battery using a ground and 9V rail. In the context of this question I think this circuit is sufficient to explain my situation (values are not accurate and circuit is not complete):

Now, my main problem is that whenever I'm going to close SW1 to turn on the device, I'll get a loud pop sound at the output because C4 is not yet charged (at least that's what my simulation is telling me).
I'd ideally prefer to use the smallest circuit possible and a circuit with very low quiescent currents. There are two ways I've considered:

Somehow make the main amplifier supply rise very slowly when SW1 is closed
Somehow short R5 when the device is turned on. I've considered using an n-channel MOSFET, but I'm not sure if I can reliably make sure it's always shorting R5 fast enough.

Would one of these be the way to solve this and if so how would a circuit look like?
I've also looked at this question. Since I'm not hooking up a speaker: Would disconnecting my output ground using a MOSFET work like in answer 1? Unfortunately I don't understand answer 2 at all.


texts: Is there a simple IC for disconnecting a power source?

texts:
I'm looking to create a simple circuit to connect/disconnect a power storage capacitor to/from a larger circuit. In the model railroading world, we use capacitors as "keep-alives" to keep the decoder (the larger circuit mentioned above) powered when a train rolls over dirty track or a dead spot. This can create a problem when programming the decoder. The programming process requires removing power from the decoder for periods of time, and if the capacitor is connected during this process, programming can fail.
The decoders I use have a logic level (4.5V) output that is active high when the capacitor (~12V) can be connected to the decoder, low when the capacitor should be disconnected. I've seen others use this signal to control a FET that controls a solid state relay that connects and disconnects the capacitor, but SSRs are (relatively) expensive and this seems like something that should have a single IC solution to me. I was thinking this could probably be done with a power MOSFET, not remembering that MOSFETs are unidirectional devices (since the capacitor is both charged and discharged by this circuit).
I found that two MOSFETs can be used back-to-back to create a bidirectional "switch", so I ordered a few QS5K2TR common source 2 channel N-FETs to play around with. I have gotten this approach to work on my bench by connecting drain 1 to ground and drain 2 to the negative side of the capacitor and controlling the gates by connecting them to +5V or leaving them floating. For this to work, I had to connect the shared Source to the gate through a 10K ohm resistor, similar to what is found here: https://www.homemade-circuits.com/bidirectional-switch. I haven't seemed to need the charge pump mentioned when using back-to-back N-FETs.
Here's the circuit as it stands:

I'm a bit uncomfortable with this solution since I don't really understand why the shared Source needs to be connected to the gate through the resistor. (Well, I understand that N-FETs rely on Vgs to turn on/off, but I would think that connecting the shared Source to Gate through a resistor would prevent this from working correctly, especially since the "high" voltage current of charging or discharging the capacitor flows through this shared Source)
I also haven't been able to find what seems like the usual solution for what I have to imagine is a rather common problem: disconnecting a battery/capacitor that is charged and drained over the same lines. I'm sure this is because I'm not using the right search terms.
Can anybody point me towards the correct approach for this problem? Is there a single IC that could fill the roll of U1 above, replacing the dashed box?
Thanks for your help!


texts:
I discover a problem on my design, with a STM32F042K6 MCU and a MCP2561 Can Transceiver.
I can send some frames on the CAN Bus but i can't receive any frames.
When i put my scope probe on the CAN Rx Line between the MCU and the Transceiver o observe a bad low level voltage like this :

I have checked, this MCU Input is 5V tolerant.

What is the reason of this bad low level voltage ?
I think it's why my MCU don't receive any acknowledge and any frames.

Is there a problem on the Transceiver or on the MCU ?

Thank's for your help !

It seems there is a problem on the ACK bit transmission :
I don't understand why. Any idea ?


texts: I am working on  the project with SE2431l front end ic ,unfortunately the lead time of the ic is very much. So i was searching for the substitute. I found RFX2401C but the pin to pin configuration is not same.  Can any one suggest ic of same family?


texts: Filtering capacitor only adds noise in a rail-splitter

texts:
Say I need to make a very low-noise signal inverting schematic. For that I came up with the schematic below - the U2 is a low-noise opamp in an inverting configuration, and the schematic around U1 is a rail-splitter typically seen in guitar pedals - it provides the "ground" level for the U2, thus converting a unipolar power supply into a bipolar.

The problem is that simulation shows that removing the C2 filtering capacitor drastically improves the noise characteristics for some reason. When C2 is connected, there is a very clear spike at around 20kHz, while removing it removes the peak (graphs are also shown below).

So, the question is: what causes this spike? Why can't I add additional filtering using C2 capacitor (even the rail-splitter TLE2426 datasheet suggests leaving only the C1 capacitor)? It does not even improve the noise characteristics at ~1kHz frequency range, so what is the point in it? In guitar pedals the noise characteristics are not so important, but still, why is it there then in guitar pedals if it does not improve characteristics at any frequencies? Any suggestions on should I remove the C2 capacitor in my case or how should I reimplement the rail-splitter?

P.S. If it is not clear: I've used the same schematic for both tests, the only difference is the C2 capacitor. In both cases I tested the full schematic shown below with both U1 and U2, these are not separate schematics! The input and output are the U2 input and output, U1 only provides the mid-rail voltage. I've just tried to remove the C2 capacitor from this schematic.


texts: Long term effects of operating in Saturation mode of transformer

texts:
What are the long term effects of operating a transformer in Saturation mode? Let's say my transformer can deliver 1VA of power while operating in saturation mode and i consume around 0.6-0.7 VA. Would a long term use (>3 years) of transformer in saturation mode can potentially damage the transformer (it's core or any other part?) when we are operating a const 70% of it's total capacity?

If yes, how can i alter the design (increase it's power capacity?) so that my transformer does not breakdown in long term usage while in saturation mode.

i understand operating in saturation mode can potentially distort sine wave, but it does not matter to my application. i have searched this form but could not find an answer.

Thanks.


texts: How do I add the board of a pre-existing controller to my project?

texts:
I have a DigiSpark board that has the schematics and board files released in their website. I am making a PCB where I need to have that part in my circuit.

Right now I have tried editing the DigiSpark's schematic and add the components I need and work on the board but that doesn't work properly.

Tried exporting the DigiSpark board as a library but it adds every component (as in: resistor, capacitor...) rather than the actual board to the files.

Is there any practical way of making my own project and when I am done with it, import the schematics and wire things up and then work on the board while keeping the original DigiSpark board design?


texts: I have an Arduino UNO Rev3 and need to make sure that once programmed, no more information can be written to it. I'm guessing this can be done by clipping a pin or two on the microcontroller, but not familiar enough with the details to be sure.


texts: can you explain me the working of this circuit in detail?

texts: this circuit is a occupancy light circuit i want to know the working of the transistor regarding base,collector and emitter in the transitor


texts: Isolated buck H bridge control system design

texts:
Any references on how to go about modelling an AC/DC mains isolated H bridge buck converter in s or z domain? All the current resources online point to modelling buck converter with a single switch and in non isolated configuration.

The current process that I use for compensator design is that I look out for the frequency region where the LC low filter cutoff happens and at that region, the phase response drops almost to -180 degrees. Then I would design a phase lead lag compensator with some phase being added in the frequency region where the phase response drops to -180 degrees. Then I use the same compensator in the SMPS design without taking into account other components present. Wanted to know how much off I would be if I make this assumption that other components in the converter doesn't add much to phase response?


texts: Gyroscopes Output Voltage drift when not moving, trivial question

texts:
I don't have good experiences with gyroscopes and i would like to ask the question.

Do the Output Voltage of Gyroscopes, whether analog or digital, usually drift when it is static?

Ideally there is supposed to be no change. I'm programming an Arduino, to take a reading when it is not moving. I plan to use the on-board ADC that leaves me around 4mV error range, input: 0V-5V returns: 0-1023, to be able to determine if the gyroscope is static. Would the theory be correct or would it just generate errors?


texts: Should I connect the analog common ground the earth in this configuration?

texts:
Below is a floating signal source is connected to an instrumentation amplifier.
The floating signal source stays in a metallic enclosure.

To make best out of it for this connection in terms of noise, the circuit should be balanced. Here is what I understand so far:

1-) The source impedance Rs1 must be found empirically so that we should add Rs2 in series to the negative terminal of the source. So I have to measure all source's output impedances and add proper resistors. Rs1 must be equal to Rs2.

2-) We should use twisted shielded pair. This will ensure that magnetic coupling to pairs be L1=L2 because of twisting. And the shield will protect the capacitive coupling of electric fields.

3-) The shield should be connected at one end to the earth. In this case at the receiver since the source is floating.

I'm planning to follow the above procedure. But what I don't know about the following:

1-) Should the point A be connected to the Metallic case?

2-) Should the AI GND be connected to the earth?

3-) Is 10Meg recommended value? I read it from just one document.


texts:
I was planning on getting a RIGOL DS1052E oscilloscope for some radio work. I will be working with the  400Mhz and 900Mhz bands using Amplitude-shift keying (ASK). I know the scope is 100Mhz: 1GS/s. but is this enough for the bands I will be using?

Ediit:
The system I am working with is using AM and no other modulation. I need to look at the the RF output to see that the packets are correct. Is a spectrum analzyer better than a scope for this?


texts:
Lets imagine a Forward/Flyback converter with a zener snubber. How to analyse how this DZ snubber works?

My problem is that how can I know what is the voltage of the common node of the two diodes? What is the right method to approach it?
An example with values would be great.


texts: Help understanding 60 Hz low pass filter behavior in oscilloscope

texts:
I have been testing this circuit in simulation

which is supposed to be a low pass 60Hz filter, as far as i am concerned the simulation  works as intended in simulation starts filtering frequencies above 60Hz and after this the amplitude starts going down, i can use a bode plotter to confirm this and change the frequency of the function generator while i see how the sin wave gets less and less amplitude the higher the frequency

However when building this same circuit in the protoboard and using the oscilloscope at the output of the OPAMP something odd happens, i uploaded THIS VIDEO where you can see its behavior in the oscilloscope

The blue signal is the input while the yellow is the output

I start a with a 5v 30Hz signal, and slowly increase the frequency, after 60Hz the output  starts increasing the voltage up to 10v and only after reaching 300Hz, it starts filtering the signal, why is this happening? is it normal?


texts:
I have

a solar panel that outputs maximum 1.2W (7V, 0.17A).
a 5V 1A USB power supply
a 3.5-9V, 1-3W water pump.

I'd like to have the water pump running all the time using power from (1) and (2), preferably not drawing unnecessary power from the USB power supply... So let's say, if the solar panel gives out > 1W of power then don't draw from USB. Wondering what kind of circuit I'd need to achieve this.

Background: I have very basic knowledge of electronic circuits and can connect components following the diagram... that's about it.

Thanks so much!


texts: Are 1uF NP0/C0G capacitors different than regular 1uF capacitors?

texts: I am reviewing an schematic and it contains several reference to 1uF 0402 SMD capacitors, some of them are marked simply as "1uF" and others as "1u, NP0/C0G" , I think both are the same, is there any difference?


texts:
I have some capacitors that I cant figure out the value ( in farads {pf,nf,uf ect...}) Here are what they say:    (each space shown here is a line down on the capacitor)
capacitor #1
103M
Z5U
2-3KV ARC
GAP KAP
CHINA
capacitor #2
NPO
7.5D
IKV
Capacitor #3
CM
1000M
125L
Capacitor #4
271
2KV
Capacitor #5
Z5U
4700M
IKV
I am still sort of a beginner in electronics, and am only 13, so any information would be great!
Edit- I have a few more caps
I have couple more capacitors, can anybody tell me the value in farads? (pf, uf ,nf)
1
Y5F
221k
2kv
2
CM
Z5U
.1M
100v
3
20 underlined (I am guessing this is 20nf)
4
On frontside- 680 K
On backside- 74-16
Any answer would be great, even if you only know a few of them


texts:
I am planning to build a high luminosity lamp to act as a growth lamp during winter for my plants.

For this, I manage to recycle (upcycle?) a big LED bulb with the following inscription:

LED Corn Light E40
Volt: AC 35-265V
CC1: 6000K
Power: 54W

The bulb was not matching my needs as is (especially since it was providing an almost 360 degree light, while I need a directional light source), so I took it apart.

I saved 8 nice aluminium strips with 19 SMD LEDs each. I plan to power these from an ATX power supply, so I have a 12V 15A (probably I should say something like 10-12A to be safe) source.

The problem is that I can't identify these LEDs (I couldn't find a datasheet), so I'm not sure how much power they need. Based on similar LEDs I've seen around, I think 3V and 250 mA per LED would be a good guesstimate. Which means I should form groups of 4 LEDs in series and add a 3/0.25 = 12 ohm resistor per pair, everything nicely stuck to a solid piece of aluminum for cooling.

Are my calculations correct?

Side question: I was measuring the LEDs with a diode meter and it seems they very dimly light up. Also, when touching them in certain conditions, they produce a very dim light (the LEDs being disconnected from any circuitry). Is there any explanation for this?


texts: Why is FM modulation not used in modern cellular communication?

texts:
Both bluetooth and celular links use GHz level carrier waves. Yet the modulation techniques are very different. I know why FM is more resilient to noise comparing to AM.

But why is FM preferred for bluetooth and PSK, FSK ect. is used for modern cellular communication even though both have similar carrier frequencies? It is a large topic but I was looking for some reasoning behind not using FM for cellular communication.