texts: Non-isolated power supply regulated transistor LED driver circuit Reactance

texts:
This is a very interesting and simple classical Non-isolated power supply. Before asking the my question, let me try to list the things that I think I know about this circuit. correct me if I am wrong.

C1 is a 274 (270nf) capacitor, with a 120vac/60hz input, it's equalivent to 9.824k ohm resistor. (XC = 1 / (2pfC))
D1-D4 is a AC rectifier to convert AC into DC.
D5 (ZR) is a 24v Zener diode to stabilize the voltage at that point to 24v. Because the current at that point is about 1mA (120v-24v/9.8k+.68k)=.9mA, the zener need to be at least 24v*1ma= 0.025 watt.
The 8050 NPN is used as a switch here. Ib is about 0.75mA and with a DC gain of 120, Ie should be about 9mA
The 4 white led have a 14.4v voltage drop.

Question 1, what is the purpose of R4 680? Since we already have c1 and it's 9.8k.

Question 2, Since there is a 1mA current limit by the C1 and R4, what exactly is the current for LED1-LED4?

Question 3, what is the current going through D5? less than 1mA I suppose.

Question 4, if I want to increase the brightness of these LED, which are way too dim, which component do I have to change?

Question 5, I know this is very dangerous circuit because it's not isolated, but since there is a 24 zenzer diode, so the voltage at the led leads are probably less than 24v. How dangerous is it to touch those led leads? 1-10, 10 being the most dangerous.


texts: Normally Closed, 24V DC, 1/4 NPT Female, 1.4 Cv solenoid valve power supply

texts:
I have a solenoid valve of Normally Closed, 24V DC, 1/4 NPT Female, 1.4 Cv, 500mA max current drawn.
Can somebody verify the power supply requirement.
would this be an ideal power supply unit for the above mentioned solenoid valve?

POWER SUPPLY.
SOLENOID VALVE


texts: is it safe to have coaxial cables set up like this?

texts: Wondering if this set up poses any harm or anything


texts:
Here is a picture of a circuit I built. I'm a novice in building amplifiers, but I'm interested in building a simple circuit that picks up music using a condenser microphone and transmits it across some distance using cable with headphones attached to the other end. The output is taken from the emitter of the Q3 transistor.

There is a simple audio pre-amplifier that I found online, connected through C2 capacitor to a common emitter amplifier of my design, which in turn is connected to transistor Q3 serving as a current buffer. Again, I have little to no experience in building audio circuits, so I just put together what I thought would work.

The circuit does work: When I play music from a phone near the mic, the music can be heard from the headphones in another room (I connected a long wire to the output, across R8 resistor). There is a lot of noise though. The sound is clear enough so that I can hear the lyrics, but quite barely. I would like to hear suggestions on how to improve this circuit. The sound quality does not have to be good at all, but I'm would very much like to hear what I'm doing wrong. The CE amp has quite a high gain which I thought might lead to clipping so I've tried to limit its gain by inserting an additional resistor in series with C1 capacitor and it has helped a little, but not much.

Rather than pointing me to another, more advanced circuit, I would like to hear what is wrong with this one and how to possibly improve it. I've tried finding information on Google, but most sources deal with reducing noise on professional, bought audio amplifiers instead of simple electrical circuits.

EDIT: There was a mistake in my circuit schematic.

EDIT: Here is a picture of the headphones.


texts: Why aren't ferrite rod antennas used in WiFi?

texts:
Does it have something to do with soft ferrite's low coercivity, still not low enough at gigahertz frequencies?

See, I'm putting together high gain receiver antennas and transmitter antennas. Space is an issue. So maybe the same as ferrite rods allowing for antenna meters and meters long to be coiled around said ferrite rod just a few inches long, ferrite rods will do it for WiFi antennas.

Am I wrong? If so, in what aspects?


texts: Learning about security of UART and RS232

texts:
I'm trying to learn about UART and related problems and solutions.

IIUC, UART is a hardware, RS232 is an interface and hyperterminal is a program. Would these parts be able to work together?

I asked a knowledgable professor in CS who illustrated it with an application use case where I understood some but not all.

I attach the illustration of the description where I understand some but not all.

I want to understand it all. Please correct me if I'm wrong

Why is a message-queue relevant? It looks like an array of msg?
Why is S (memory size) relevant?
Why is the difference between DMA and MMI relevant? Is it because DMA bypasses the CPU and therefore the CPU can't be relied for security?
Is ETH ethernet and could be via UART or only UART? Is the hyperterminal and standard i/o and tty examples of UART?

I will read more online sources of course.

K means a key file that should not be accessible and the ethernet connection, IIUC, is example of peripheral connection via UART.

P is supposed to mean a pointer. I vaguely hypothesize that it's about getting a pointer to a part of the RAM that is supposed to be secure.

Can you help me understand?


texts: Basic rules to calculate the equivalent resistance of a resistor circuit

texts: I have a certain circuit only containing resistors of different values. There is one 'input' and one 'output' for the current. How do I calculate the equivalent resistance of the circuit? Are there any basic rules to follow?


texts: Create array of std_logic_vector in VHDL with increasing bit-width based on generic parameter

texts:
I have following scenario

I[n] = nth Data Input, where n=1 to N
W = bit width of I[n]
A[k] = output of a signed adder, where k = 1 to N-1

I want to use my signed adders in following way:

A[1] = I[1] + I[2]
A[2] = A[1] + I[3]
A[3] = A[2] + I[4]
...
A[N-1] = A[N-2]+I[N]

As we are doing signed addition, bit length of output of each signed adder should be 1+(bit length of data input to the adder)

Thus the bit widths of adder output A[n] should be follows

A[1] W+1
A[2] W+2
A[3] W+3
....
A[N-1] W+N-1

My question is if N is a generic parameter, is it possible to declare in VHDL an array of N std_logic_vector's with bit-widths as W+1, W+2, W+3,... W+N-1 ?

The simple workaround to the problem is to have bit-width of each A[n] to be equal to maximum required bit-width i.e. W+N-1. However, this would mean that on synthesis same maximum sized signed adders of same bit-width are generated for each pair of input, potentially wasting circuit area.


texts: Why are there different ways of winding a common mode choke?

texts:
Below shows two types of CM choke winding:

Is there a difference betwween two in applications? They are both used in literature, yet I havent seen a single sentence abou the digg


texts: What should be the typical gain of an nmos only LC VCO? Should it be more than 100MHz/V or 200MHz/V or lesser than this? Which is more useful - keeping the gain high or low?


texts:
I have been working with AVR microcontrollers for the past 2 years and I am now quite comfortable with them. Like most people started with arduino but quickly felt limited by the options it provided and hence moved to working with AVR without arduino code on it.

I feel now the time has come to move to ARM architecture. From what I have seen they provide a lot more power and functionality  and it seems like the logical next step.

However I am finding it difficult to find the right point of entry into the ARM world. The internet is filled with resources and it's quite daunting.

I am hoping someone experienced can point me to the right way in terms of reading, tutorials, links etc. to get me started.

All I know about ARM at this point is:

Unlike AVR they license their design to third party companies that actually fabricate the chip.
There are many families/vendors of ARM  from various vendors each having their own feature set, development boards etc.

Some of the main questions I have in mind:

What are the most popular vendors of ARM that are easily available and have low cost of entry? Also is there a link or list compiled by someone which lists all the arm families available?
If I buy ARM from a particular manufacturer, am I bound to use their development tools (free?) or I just like AVR gcc, free ones are available?


texts: Voltage Measurement with ST Microcontroller

texts:
I want to measure DC voltages from 1mV to 10V.

I will be using STM32L053C8T6 Discovery board.

I want to use 3.3V reference voltage. I know that if you want to measure voltages bigger than reference voltage, you need to use voltage divider.

But what about if I want to measure voltages like 1mV? Do you have any suggestions how to do it?


texts: What transistor if they are needed do I need to drive 5 blue LEDs on a lm3915 and how should I hook it up?

texts:
I am using an  LM3915 LED driver in dot-mode. I would like to drive 5 blue LEDs (3.3V forward voltage @ 20mA per LED) per output.  What type of transistor should I use to make this happen?
And how do i put the transistors in the circuit i was thinking to use 18 volts as power supply I don't think the IC can handle 5 LED's by itself thanks

Original question: what i want to do is 5 leds all blue per output
with the lm3915 in dot mode the leds have a voltage of 3,30 V the current of the leds each are 20 mA   i want to put them in a analog vu shape <<< something like you get like simulated needle movement
but with leds thanks


texts: Measure voltage of 2 different batteries on Arduino

texts:
Currently I'm using a resistor divider to measure the voltage of a 6v battery that is connected to an Arduino via a 5v power regulator. I also want to be able to measure the voltage of another battery (7.2v) on a separate circuit with the same Arduino.

The issue is that the batteries will be on separate circuits, and thus, have no common ground (batteries are not in series or parallel). Is this possible?


texts:
I need to know the type and value of these two diodes, in order to buy two equivalent ones. Can you help me to find it out please?
The diode with the yellow stripe has no markings, while the other one is marked 5.1 B2.


texts: Microcontroller Memory reliability : Info Memory vs External Flash

texts:
I had a small query which I couldnt find a short answer in google.
for storing small amount of data ( say 8 bytes ) in an embedded system (containing an external Flash too), is it preferred to store in EXTERNAL FLASH instead of the controller's INFO MEMORY ( MSP430 in my case).

My query is not specific to MSP430, but in general.

I was told by my lead that INFO Memory is not reliable and External Flash should be used. I am not convienced.

I was hoping if there is any technical reasoning as to which memory is more reliable (considering that proper care is taken while writing to memory).

Thanks in advance.


texts: Is there some standard way to get information about BJT (Bipolar Junction Transistor) rise and fall times (the high power ones) ? In essence a IGBT is a BJT being driven by a FET, so there should be some high-power, medium-speed BJT.


texts:
I am just wondering if there a way to attach a motion sensor rated for 2.5 amps to a fog machine that requires 4 amps?
I’d like to replace the manual switch on the fogger with the motion sensor. At this point if I just hook it up as is the sensor will trigger the fogger but then gets stuck in the on position and will not shut off.
I assume it’s because the fogger is drawing too much and won’t allow closure for whatever reason.


texts: Transmitting data over inductive charging coils (or boosting RFID/NFC power supply)

texts:
I know that data can be sent over power lines through various different types of modulation - that is as far as my knowledge ends.

I have a small D.I.Y. project (a board game) that requires some form of wireless data transfer.

The range is insignificant, depending on implementation it will be either a maximum of 2cm or 30cm.

The problem is not only do I have to transmit data to the pieces (this would be simply achieved with some nrf24l01+ RF transceivers otherwise), but the data has to be modified depending on the pieces location on the board.

I intend to power the pieces via inductive charging loops. But due to the amount of power required in the pieces (5v, ~150mA (24 individually addressable RGB LED's running at a low intensity and an ATTiny)), there won't be much space left for NFC/RFID tags or possibly an IR transmitter.

As I only need to send a couple of bytes of data at a time, I was thinking I could either use an NFC/RFID module and somehow boost the power it induces.

Or more likely, to use the induction could that I plan to power the pieces with and send the data at the same time (and in the same direction as the power) with some form of modulation.

My knowledge of circuits and this sort of stuff is extremely lacking, but I'm willing to try things.

Are there any off the shelf chips or low component count circuits that will do this?

This caught my eye, but I don't have any idea whether it would work once the now modulated 5v DC signal had been converted to AC by the induction coils and then rectified back to DC at the receiving end. Also, I'm not sure whether the receiving circuitry would be significantly different or just reversed.

http://www.audioscientific.com/45_Circuit_makes_simple_FSK_modulator.jpg


texts: Manufacturing of Translucent LED Indicating Symbols (e.g. router indicator lights)

texts:
I've been researching how manufacturers create custom LED-illuminated symbols such as those seen on the router in the image below:

I haven't been able to find any information online from custom enclosure manufacturer websites or discussion websites such as this. I found a somewhat related thread in the 3dprinting Stack Exchange but it never led to any real conclusion on the generally accepted method of creating these LED effects (LED Indicators with 3D Printer).

Based on my observations of these physical products, my best guess is that they are using some type of translucent material, possibly tinted acrylic, and using some method to print the negative symbol shape on the back side of the acrylic. Then a light pipe or direct LED lighting can be used to illuminate each symbol.

Could anyone confirm if this is the method that is used? If so does anyone have more details on specific materials, printing processes, and manufacturers which can provide this service?

Thank you all for your consideration.


texts: Circuit simulation for audio equalizer not working need help debugging

texts:
For a personal project I was designing a basic audio equalizer circuit using this online simulation tool called TinkerCad.
I managed to build the circuit but for some reason I really can't get it to work.
I think it has to do with the fact I connected multiple breadboards and I may not have connected them properly (I had to do this because you cannot shorten the lengths of resistors on TinkerCad.)
Attached below are the screenshots of the circuit diagram, and a snapshot of the breadboard.


texts: Simulating Altera FPGAs with an old version of ModelSim?

texts: I'm hoping to do some development work on Altera FPGAs that will likely be larger than is supported by the free edition of ModelSim.  I have an old copy of the full version hanging around (version 6.5, I think) -- is this likely to work for designs with modern FPGAs (e.g. Cyclone IV), or do I need to upgrade?


texts:
There is a device called a JTAG programmer. This device is typically used to programm MCUs or FPGAs.
My question is do you actually need this device to program a MCU or FPGA with JTAG? Are simple wires/jumper cables not enough for the JTAG programming?
I mean to program a evaluation board you don't need this kind of device. Most of the time you can use a micro usb cable to program it.


texts: Is the circuit a Parallel RLC if there is a voltage source in between capacitor and inductor?

texts:
simulate this circuit – Schematic created using CircuitLab

As the schematic shows, there is a voltage source in between capacitor and inductor. Is it a valid Parallel RLC circuit. For example: can we say that we can use the standard equations like:

Alpha = 1 / ( 2 * R * C)
W0^2 = 1 / (L * C)


texts: Is a diode's forward voltage stable enough to be used as a reference voltage?

texts: Assuming a resistor is in series with a diode (say, a 1N4001) so that the diode has around 1mA of current, will its forward voltage be usable as a voltage reference to within 1% (relative to itself over time and with ambient temperature changing by 10F max)? The voltage doesn't matter, as long as it doesn't change to a noticeable degree.


texts: Different amperage with a normal and a hook Multimeter?

texts: I am measuring the electric power (P = VI) in a gear-motor. I measure it of two ways. One way is measure with a multimeter the resistance of the motor, then with V=RI, I measure the current, then I multiply that by the voltage and a obtain something near 2000 watts. In the other hand I have a multimeter hook that measures high values of current, but with it I obtain a different amperage and that leads to an electric power near of 600 watts. Why is this? I think is a big difference, which is the real one?  Since I am controlling it with AC current, Is AC resistance or amperage Different than DC? Thanks in advance


texts: How do I create "beveled" T-intersection traces in Eagle CAD?

texts:
Frequently it is convenient to route traces on a PCB such that some other traces or pads are at right angles to a common bus. However, this creates "T" intersections which have 90° angles, which can potentially create problems during the copper etching process. (Such as acid pockets that decrease the effective trace width.)

Using the "Route" tool, I can't add additional traces at 45° angles to create a "beveled" intersection, and Eagle doesn't seem to have any option to adjust how intersections are handled.

How can I create a "T" intersection that incorporates some sort of bevel to avoid the 90° angles?


texts:
Thanks in advance for any assistance you provide.
My system does everything correctly as expected, but its performance is abysmal.  The lift of the pump is very poor, it manages about 50cm before cutting out and the best flow I can get is far less that the pumps rating, I'm guessing a litre/minute.  The system spends more time charging the battery than it does pumping water during daylight hours.
The controller has an extra input for another solar panel, and a friend has some old panels they can give me, but they live 100km away, so haven't been able to explore this angle of improvement.
I haven't measured pump flow, pump current or voltage, so apologies in advance
The components are below
Lithium Battery
https://www.solarking.net.au/batteries/lithium-battery-cb-7-12-5
Solar Panel
https://www.supercheapauto.com.au/p/kt-cables-kt-cables-12v-40w-solar-panel/572271.html
Controller
https://www.kogan.com/au/buy/wholesalegateopeners-1224v-10a-solar-regulator-black-casing-reg10abkk/
Bilge pump.
https://www.bcf.com.au/p/bowline-500gph-bilge-pump/563499.html
Float Switch
https://www.bcf.com.au/p/blueline-automatic-float-switch/329215.html


texts: Modify circuit to turn motor on/off multiple times per switch press

texts:
I purchased a timed air freshener kit which makes the motor spin when the switch (SW1) is pressed. I have created a schematic based on the diagram in the instructions (pdf).

simulate this circuit – Schematic created using CircuitLab

At the moment the circuit will run the motor once per switch press. How would I modify the circuit to make the motor "turn on and off" multiple times per switch press?

Requirements:

Continuous "on and off" motor cycles when switch is in ON state (currently the switch is a push button, thinking I should replace this with a toggle to make sure it is either ON or OFF)
Motor should turn on for 1 second
Motor should turn off for 5 minutes

If it's possible I would like to control both these periods using a variable resistor. R3 in the diagram is actually a variable resistor which controls the length of time the motor stays on for.


texts: Improving brightness of multiplexed 7-segment led display

texts:
I have a two digit 7-segment LED display which is driven multiplexed by a microcontroller. PORTA is for the anodes. In my code I shift a 1 through PORTA. On PORTB I say which segment should light by setting it to 0. My problem is that the display isn't very bright although I don't have any resistors connected infront of the 7-segment. How can I extend this circuit to get a brighter display? Maybe with transistors or MOSFETs? I've also attached a simplyfied schematics of my circuit.

Thanks for the help in advance.

Solution: 4 NPN transistors.


texts:
From what I read on the internet we should respond to interrupts as quickly as possible, when programming microcontrollers; and that flags should be avoided because they tend to compound over time.
But the quickest way to respond to an interrupt is by using a flag (just need to change the boolean value of the variable and continue the code inside the main function). How to solve this problem? Should a state machine be used in any interrupt to avoid flags or that doesn't matter?


texts: What does "Collector Power Dissipation" mean on a transistor datasheet

texts:
I was looking at a datasheet for a transistor here, but I didn't know what Collector Power Dissipation meant. It's value is 1 watt.

Does this mean that this part is rated 1 watt? They already have the maximum voltage and amperage, so that makes me question what this means. I couldn't find anything on Google either so I am confused as to what this is.


texts:
I've been looking around the web about placement and proper net routing of decoupling capacitors for ICs. In this example I have a pic micro-controller using internal clock at 80MHZ, with the decoupling caps placed closed to it on the same layer (top). The only difference between them is the way the nets are routed.

This is a four layer PCB:

------Top Signal-------
------Return Plane-----
------Power Plane------
------Bot Signal-------

What I've found from my searches is that everyone agrees on placing the decoupling cap close to the IC and on the same layer when possible, also if going to planes vias should be as close as possible to cap pads and use as small a cap size as possible. but then when it's about making the connection with the IC pads there are different versions. Of course on my design I have the room to move the caps around and place them wherever I want.

I've read things like the following:

Sequencing the caps, so that power comes in first through the cap and then a trace to the IC pad. (Example 1)
No vias in between IC pins and cap to join with a trace, vias must be on outsides. (Example 1 and 3)
If more that one decoupling capacitor, the smaller cap should be closer to the IC pin. (Examples 1-4)
No traces between cap and IC pads when possible, always preferred method is to use vias when power planes are used. (example 4)

I hope that someone can shine some light on this topic.
If I where to pick one, it would be Example 4. Caps are reversed, opposing vias are close which should minimize inductance loop.


texts:
I have been trying to find laser level detector components.  I took apart one on hand, see what looks like basic photodiodes and a light tube.  Note the 3 photodiodes visible in the center part.

Could these be off the shelf photodiodes?

Any ideas how they are determining location?

Laser level type = https://en.wikipedia.org/wiki/Laser_level


texts: problems using atmega644pv jtag pins as gpio

texts:
I've been trying to use port C pins on an atmega644pv as gpio, and have been running into some trouble. as far as i can discern, it seems like the middle four pins (PORTC 2,3,4,5) are stuck in a high impedance state (used a screwdriver to short them the outer four pins, and the later mentioned leds behaved as desired). digging a bit it looks like these are the JTAG pins, but i disabled JTAG via the fuse bits. the code below (should) make the attached leds light up sequentially, sort of like a cylon/knight rider project but only going in one direction, but when i run it the four middle leds only light dimly, whereas the outer ones hit full brightness. for reference, the leds are attached between PORTA and PORTC, and have a resistor series with them on the PORTA side. I can't use only PORTA and ground, because i need to reverse bias the leds in my actual code, and then monitor their voltage.

-U lfuse:w:0x62:m -U hfuse:w:0xd9:m -U efuse:w:0xff:m

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

int setup(void)
{

    DDRD = 0x7F;
    MCUCR |= (1 << PUD);
MCUCR |= (1<<JTD);
PORTD=0x00;
DDRC=0xFF;
DDRA=0xFF;

}

int main(void)
{
DDRA=0xFF;
DDRC=0xFF;
PORTA=0x00;
    PORTC=0xFF;
    while(1){
    if (PIND&0x80){
        PORTC=0xFF;
        PORTA=(0b11111110);
        _delay_ms(10);
        PORTA=0b11111101;
        _delay_ms(10);
        PORTA=~0b00000100;
        _delay_ms(10);
        PORTA=~0b00001000;
        _delay_ms(10);
        PORTA=~0b00010000;
        _delay_ms(10);
        PORTA=~0b00100000;
        _delay_ms(10);
        PORTA=~0b01000000;
        _delay_ms(10);
        PORTA=~0b10000000;
        _delay_ms(10);
        PORTA=~0b00000000;
    }
    else{
    _delay_ms(10);
    }
}

return 0;
}

many thanks!

EDIT: forgot to call setup() at the beginning of main()  =(
more coffee was required


texts: Replacing Multimeters with Megaohmmeters

texts: Standard Digital multimeters can measure up to the ranges of 20 Megaohms. Then why should we use Meggers at all?


texts: Why is there a maximum time for length of write pulse to write on an EEPROM?

texts:
I am still just learning about electronics on my own, so please bear with me.

The EEPROMs that I have come across (for example this one where the t_wp max is 1000 ns.) all have a time limit for the write pulse (I think this is called the Write Pulse Width). I am just curious, but

1) What is the reason that EEPROMS have this upper limit?

2) Are there any parallel EEPORMs with no upper time limit?

Please note that I am not asking about the limit on the number of times one can write to an EEPROM.


texts: Powering a Raspberry Pi + a display using phone battery

texts:
This may be a rookie question and if it is, I apologize.

I want to power a circuit with Raspberry Pi Zero + ILI9341 2.4inch Display with backlight using a phone battery. Intention is to boost phone battery voltage (3.8V 5350mAh with Charging Limit 4.35V)  to 5V using WeMoS Battery Shield (https://wiki.wemos.cc/products:d1_mini_shields:battery_shield) , then power the circuit. However, the circuit doesnt work / rpi doesn't boot up correctly. If I simply plug USB port, the circuit works well.

Any pointers as to how to solve this problem is greately appreciated.


texts: How to attach (safely?) an o-scope to various sources

texts:
I've heard of course that probing mains can ruin your oscilloscope, so that is out of the picture. There are a few situations I do not quite understand however:

Is probing an i.e. 10:1 transformer safe if I were wanting to see mains signal? Even if it is not an isolation transformer?

If I cannot do the above, how does a wallwart make the situation different? Is ground being part of the linear regulator the device of which makes it safe to probe directly? Just anything that is not "earth" referenced?

Can I probe something that is on battery (silly question) with no earth referenced ground?

I've heard people mention something about the ground clip, and if it is not properly placed somewhere it could damage the alligator clip with large currents, however I have no clue what that is referring to, or how massive current could flow through the o-scope to the ground clip or something.

I am sure I could answer the before with some various manuals, however the ones before that I am just completely unsure of.


texts: Temperature coefficient of a voltage source

texts:
Is the temperature coefficient of a voltage source related to the internal resistance of the voltage source?
Why does the voltage increase/decrease when the temperature is increased or decreased?
In case of a band-gap reference, how is this temp coefficient related to the change of temperature to get the PTAT and CTAT? The figure below shows 2 dependencies and I didn't understand from where the temperature coefficient comes in order to cancel the linear effect of the sources.


texts: How to build a sequential logic circuit with transistors on a breadboard

texts:
I'm helping out a student with his homework, which includes building logic gates with transistors on a breadboard, and so far I've successfully built NOT, NOR, NAND, and NOR/NAND logic circuits.

However, the last question is to build this sequential logic circuit on a breadboard, and so far nothing is happening (the LED doesn't light up):

simulate this circuit – Schematic created using CircuitLab

For the above schematic, Node 1 and Node 2 are inputs (either 0 or 1 depending on whether a switch button is pressed) and Node 3 is the output, which is an LED (so presumably it should light up on some kind of combination of inputs).

  My NOR gate (which works correctly) is wired up like this:

transistor 1 left: gnd

transistor 1 middle: switch > 10k resistor > 5v

transistor 1 right: connected to the right of transistor 2; connected to 1K resistor then 5V; connected to LED then gnd

transistor 2 left: gnd

transistor 2 middle: switch > 10k resistor > 5v

transistor 2 right: connected to the right of transistor 1

I then made two NOR gates which I need to modify to make the sequential logic diagram above. Right now I have it wired like this, but it's NOT working:

  NOR gate 1:

transistor 1 left: gnd

transistor 1 middle: switch > 10k resistor > 5v

transistor 1 right: connected to the right of transistor 2; connected to 1K resistor then 5V; connected to LED then gnd; connected to NOR gate 2 transistor 2 in the middle

transistor 2 left: gnd

transistor 2 middle: connected to NOR gate 2, transistor 1 right

transistor 2 right: connected to the right of transistor 1

  NOR gate 2:

transistor 1 left: gnd

transistor 1 middle: switch > 10k resistor > 5v

transistor 1 right: connected to the right of transistor 2; connected to 1K resistor then 5V; connected to NOR gate 1 transistor 2 in the middle

transistor 2 left: gnd

transistor 2 middle: connected to NOR gate 1, transistor 1 right

transistor 2 right: connected to the right of transistor 1

If none of my description makes any sense, can someone just tell me what the expected output for the LED should be? I have two switches, so I can put in 00, 01, 10, and 11 as inputs. What should happen to the LED in those cases?

Edit: Here's my best attempt at a schematic for the sequential logic circuit. Transistors may be flipped around, not sure, but the sides I picked should be consistent (I know which side is which on my breadboard.)

simulate this circuit

simulate this circuit

Tidy-up of schematic edited in by @transistor. I have assumed transistors C and E were reversed in each case.


texts: How can I convert an input with the 16-bit Sigma delta A/D converter

texts:
Could you help me with this question?
I have some difficulties to answer it.
The question is from the PIC24FJ128GC010 family datasheet and after some research I just know the meaning of the different values :

SDGAIN value is that the S/D Gain Control bits equal to 2.
SDREFP ( S/D Positive Reference Source Select bit) is on SVref+ pin.
SDREFN (S/D Negative Reference Source Select bit) is on SVSS pin.

EDIT : The reference voltage source pin is VREF+, so we need to know this voltage. And the answer that can be eliminated is the one that mentions SVDD.
But I still don't know how to make the conversion result.


texts: Correct way to define propagation delays in VHDL

texts:
I'm currently learning VHDL. As an exercise I decided to implement some of the 7400 series chips. Below is the 74153 and while testing it with ghdl/gtkwave it seems to work.

But I'm sure this implementation is naive (lots of repetition, use of extra delayed (*_d) signals, etc). What would be the clean way to implement such a device?

--
-- 74153 implementation
-- Dual 4-Line to 1-Line
--

library ieee;
use ieee.std_logic_1164.all;

entity TTL_74153 is
  port(
  c0, c1, c2, c3: in std_logic_vector(1 downto 0);
  sel: in std_logic_vector(1 downto 0);
  g: in std_logic_vector(1 downto 0);
  y: out std_logic_vector(1 downto 0));
end TTL_74153;

architecture behav of TTL_74153 is
  signal c0_d, c1_d, c2_d, c3_d: std_logic_vector(1 downto 0);
  signal sel_d, g_d: std_logic_vector(1 downto 0);
begin
  -- delays
  c0_d <= c0 after 11 ns;
  c1_d <= c1 after 11 ns;
  c2_d <= c2 after 11 ns;
  c3_d <= c3 after 11 ns;
  sel_d <= sel after 20 ns;
  g_d <= g after 18 ns;

  -- logic
  y(0) <= '0' when g_d(0) = '1' else
       c0_d(0) when sel_d = "00" else
       c1_d(0) when sel_d = "01" else
       c2_d(0) when sel_d = "10" else
       c3_d(0) when sel_d = "11";

  y(1) <= '0' when g_d(0) = '1' else
       c0_d(1) when sel_d = "00" else
       c1_d(1) when sel_d = "01" else
       c2_d(1) when sel_d = "10" else
       c3_d(1) when sel_d = "11";

end behav;


texts:
I have a transformer that I've taken out of scrap. I'm trying to discern it's electrical specifications. In my setup I have a function generator hooked up to the primary winding, and an oscilloscope hooked up to the secondary winding.

When I apply a 1V P-P sine wave across the primary winding @ 10Hz, I get 80mV P-P on the secondary winding

When I apply 1V P-P sine wave across the primary winding @ 100Hz, I get 740mV P-P on the secondary winding

When I apply 1V P-P sine wave across the primary winding @ 1KHz, I get 3.6V P-P across the secondary winding

I'm confused because shouldn't the transformer produce an output that's a constant multiple of the input amplitude (Vprimary * turns ratio)? It seems to effectively be acting as a high pass filter. Is this normal or expected behavior? How can I properly measure the turns ratio, a physically-derived, frequency-independent property?

The line impedance of the primary winding is 1 Ohm.

Thanks.


texts: What is the difference between transresistance and differential resistance?

texts: Transresistance is defined as the change in output voltage over change in input current. While differential resistance is defined in the same manner. So what is the difference ?


texts: Designing a Power signal plane to draw heat from a PoE Module

texts:
I am designing a PCB that would be powered by this PoE Module. The PoE module provides 5V output and drives a microcontroller, ethernet interface controller and other lower power
circuitry. I do not see the power consumption to be more than 100mA.

The PoE module's datasheet recommends connecting the output pin (+V DC) and the ground pins to their respective signal planes to draw heat from the PoE module. I am designing a 2 layer board and I always make the top as well as bottom layers to be ground layers.

In order to draw heat from the PoE module, I created a polygon for the DC voltage output as shown in the figure below in the top and bottom layers and connected them using vias. Is this sufficient enough to draw heat from the boards? The polygon is about 0.5 sq.inch in size while the board is about 9 sq inch in size.


texts:
Please help me find the output function, with \$V_{REF}\$ as reference, and \$b_5-b_0\$ as the digital input for this circuit (1):

I'm kinda confused with this Series capacitor that's splitting the array. It it weren't for that capacitor and all parallel ones were scaled normally, the output would be:

\$\displaystyle V_{OUT} = V_{REF}\frac{C\sum\limits_{b=0}^{B-1}b_i 2^i}{C_{TOT}} \$,

I think, but with this series capacitor I'm really not sure.

Reference:

(1) DAC Design Lecture, EECS dept, UC Berkeley, CA, 2009


texts: Calculating kW of rotational power required by an engine to generate 3 phase power when phases are unbalanced

texts:
With respect to phase balance -- or lack thereof, if one phase is much higher than the others (for example 75, 100, 75) the total power according to my generator's display is 46 kW, but would the diesel engine be loaded more? Maybe as if they were all 100 A, trying to spin and make the force required for largest magnetic field? (I'm not sure if my terminology is correct), or is it an average of them? Or root? Or something else?
The goal is to quantify the energy (fuel) being wasted (or not) by unbalanced loads on my generator. I'm not necessarily looking for an all encompassing equation to calculate the exact kW of power the engine output needs to produce 46 kW of electrical power given the unbalanced phases condition, but I would like to understand the major variables' proportional effect on the power required to make more power. ;-)


texts: What is the meaning of 1N, 2N, 4N, 6N (and probably others) in the semiconductors name?

texts:
There are many discrete semiconductors with names like 1N4148, 1N4007, 4N35 or 6N137...
And they can be produced by many manufacturers. So it looks like it is not a marketing names.

Looks like 1N are diodes of any kind, 2N - transistors, 4N and 6N optocouplers...

How does they appeared hystorically?

What means the first digit and the N letter?

How is it possible that these devices have the same parameters while comming from different producers?

Answers for Numbering of Diodes and Transistors question does not explaining the meaning of 4N and 6Ns and does not explaining the background of these naming conventions. I'd like to have more reading on this. Reference to JEDEC made by winny is very useful. I think that I will be able to find something there.


texts: High current plasma jet striking circuit

texts:
A little background:  I'm a mechanical engineering graduate student with a focus in materials, so electrical engineering is not my core background.  I'm conducting research on plasma surface treatment of metals and there's a lot of variables I'm trying to control reliably, but when it comes to the electrical aspect of the project I'm struggling a bit.  Here's a rough schematic of the electrical aspect of my text fixture:

Starting with the left box, from left to right:
DB1: wall power, 110V, 60 Hz, 20 amp breaker
Bridge rectifier, full wave, single phase: 50A max forward current, 1000V reverse voltage
C1: 500uF capacitor
L2: Self wound inductor/choke 50 turns high voltage side, 50 turns low voltage side, 55mm OD x 35mm ID x 14mm H, wound with 12 gauge magnet wire (I haven't measured the inductance, sorry!)
D1: 6amp 20kV diode
V2: spark gap, basically two 12 gauge copper wire "rails", sandwiched between insulating sheets (PTFE), and two grade 52 neodymium magnets. High voltage ignites a plasma between the rails, and the lorentz force accelerates the plasma, out of the gap and onto test samples.
R1: Power resistor bank to avoid tripping the breaker

Right now the box on the right is a cheapo AA battery powered High voltage boost converter (~20kV).

The circuit on the left provides a (relatively) high current-low voltage DC power supply, and the circuit on the right strikes the spark gap with high voltage and ignites the plasma.

The issue I'm running into is that I really need to push the current level of the plasma jet to continue pursuing my research.  The diode was $40, and I've burnt out 3 so far due to overcurrent(1 single, and then 2 in parallel).  I'd like to get the current to around 50 amps, but the high voltage diodes are extremely cost prohibitive.

So here is my question:  Is there an equivalent or similar circuit, free of high current high voltage diodes, which can ignite a plasma with a high voltage/low current source, then immediately dump current into that plasma from a low voltage/high current source.  The boost converter results in a pulsed system, it would be a bonus to have a semi-steady state system.

Thank you!


texts: Question regarding to LTspice diode simulation :

texts: While simulating using .op analysis for the forward bias of a diode in LTspice, it showing the source current Iv1 in negative sign. But, all the other currents are in positive sign. What does it mean?


texts: Interfacing many camera modules using a single DVP bus

texts:
I need to create a circuit that will have many cameras. Possibly the OVM7692. I will connect this array to my host processor via DVP.

The cameras are controlled via SCCB which seems to be a name that Omnivision gave to I2C. They will act as slave devices while the master (host processor) issue the commands (no problem here so far).

Now, to my question:

is it possible to interface a bus of DVP lines from all cameras (connect all outputs in parallel with each other) so I don't have to use one processor per camera? The idea is that only one camera will be used at a time. So control-wise: camera 1 to 6 are off and camera 7 takes a picture.

According to what I have seen on the image sensor datasheets, pins are in high-z while the device is set to low power mode.

However, I think adding some series resistances (22 to 51ohm) will be good in order to prevent an odd timing event and avoid a short.

Also, what about clock lines? will it be better to put some kind of buffer such as a NOT gate in between?

Thank you


texts:
I'm trying to make my own sensorless speed controller and I need to know the speed and the position.

What are the basic techniques used to determine the speed and position of a BLDC motor from the Back-EMF.


texts: I designed this power supply and simulated in Multisim 13.0, and noticed that the output of the full bridge was higher than that of the input to it. Would this have anything to do with the electrolytic cap in parallel with the out of the bridge? I'm unsure to why this is happening. Any help is appreciated. Thanks!


texts:
I'm trying to build an audio circuit using an WM8960 chip from Cirrus Logic based off a 2 mic Raspberry Pi board from Seeed studio. The chip outputs 1W per channel into an 8Ohm load but I'm finding the output volume to be on the low side when using 1w-8Ohm speaker.

Is there any way to amplify the 1W to increase output volume?

Can the output be fed into another amplifier? How would I go about increasing the volume?

For reference I've linked to the relevant documents below.

Datasheet for the WM8960 chip: https://www.mouser.com/datasheet/2/76/WM8960_v4.2-1142184.pdf

Schematic of board Seeed studio board I'm basing my design off: https://github.com/SeeedDocument/MIC_HATv1.0_for_raspberrypi/raw/master/src/ReSpeaker%202-Mics%20Pi%20HAT_SCH.pdf


texts: Thanks for your help on the previous question. I set up my wheatstone bridge to pins 2 and 3 of the amp. When I use a voltmeter, I see differences over the bridge as a function of resistor change. When I put my voltmeter on the output of the INA128, I see a constant voltage of ~100mv. I am supplying with 3V with the reference pin directed to ground. The voltage is 100mv even with NC at pins 2 and 3. I would have thought it should be at 0. Any advice would be appreciated.


texts: Resource recommendations for DSP beginners

texts:
I was searching around and I have had some trouble finding some decent resources for an engineer first entering the world of DSP.

What resources (books, tutorials, DVDs, online courses, etc) do you recommend for a Software Engineer (with a basic background in EE) who is entering the DSP world?

I've been reading wikipedia for a while so I've got a fairly high-level overview of what DSP is and how some of the functions work, I'd like to get a bit more in-depth with a lot of the topics though.


texts: Two mono microphones on a single stereo input jack?

texts:
I would like to know whether it's possible to record sound from two different sources on a computer with a single stereo jack input (I'm not sure whether this is a "line in" or "mic" input).

Each microphone would be at most at about 6m (20ft) from the input jack, but possibly at different length (one could be 1m away from the computer and the other one at 6m).
I don't have any specific microphone in mind at the moment, but they could be of different type.

Are there any problems I should expect? In particular, would soldering the two mono wires onto the same jack (sharing the same ground) cause any problem, or should there be a circuit ahead? If so, what kind of circuit?


texts:
I'm interested in making the following resistor-divider circuit where I can tell 'POLL' to be high by my Arduino and then sample the voltage reading. The battery will have anywhere from 6-10volts. I have quite a few 2N2222A's on hand and I was wondering if I could use it as Q1 as the voltage specification says 40v 500mA (I don't expect a load to be on this), similarly, I was wondering if I could use J176 as M1 or if there are other options? Due to size constraints I'm trying to use all TO-92 packages.

J176:

  This device is designed for low level analog switching sample and hold
  circuits and chopper stabilized amplifiers.


texts: Meaning of "Degrees of Freedom" in control system?

texts:
I have been searching google for "degrees of freedom," but it shows results relevant to statistics and physics.

I am interested in answers in the context of electrical engineering, especially control systems.


texts: 220V AC to 12V DC transformerless and main isolated converter?

texts: I am trying to build a 220/12V AC/DC max 100mA converter without transformer. I tried so much and burned some circuits. at the end I decide to write here. I searched but couldn't find and answered question here. Could you please help me to achieve that. Thanks


texts:
I have an L298N motor controller module, rated at 5 amps. I'm using it to control two 12 volts linear actuators, and I'm using a current sensor per motor to learn when the motors have reached a high current load (~2.26 Amps) then stop them once they reach that threshold.

One of the actuators shaft bent on an accident, and now it requires 3.4 Amps (instead of the 0.9 Amps "no load" current) to move. The thing is that the current draw never goes above my threshold, as measured by my current sensor (therefore, the actuator never moves when a signal is sent). But now the channels (Out 1 and Out 2) on the L298N where the bent actuator was connected to don't work properly:

when nothing is connected to those two channels, I read and output closed to 12V.
But as soon as I plug in any motor on those two channels
(whether good or bad), those channels send 0V.

What exactly could have caused the failure of these channels? And is it a short that might have happened and something burned?


texts: Why "-1 + 0j" is critical point on Nyquist plot?

texts: I am reading about Nyquist plot from this (http://www.cds.caltech.edu/~murray/books/AM08/pdf/fbs-loopanal_11Nov18.pdf) chapter. On page no. 10-2 its mentioned that "-1 + 0j" is critical point on Nyquist plot. Can someone explain why is it critical point?


texts: How to represent a variable DC supply potential difference on a circuit diagram

texts:
I have a circuit diagram for a physics experiment.
On the diagram I have represented a variable DC supply, but I would like to know where do I write the potential difference selected on the variable DC supply.


texts:
I am trying to make an electric DC motor, with brushes. For that I am using copper enameled wire. Wires are available by max. current they can carry.

How can I calculate the current the motor will draw.


texts:
i'm still working on my usb meter.

I still have a problem in my design, I would like to implement an external power supply and a battery. I was looking for a circuit that would switch automatically between the supplies.

When the external supply is plugged in, i would like it to run on that supply, else on the battery. Also the battery can't depleet when the device is running on the external supply.

I lookded some circuits up on the internet but they were always controlled by a microcontroller, which is not an option in my circuit.

Anyone have any ideas?

Kind regards


texts: Is a flyback diode necessary with a relay module for operating a Solenoid valve?

texts:
Assuming I have a relay module (I'm not sure about its features) that is connected to a 12 V DC solenoid valve and should be operated by a microcontroller.

Do I need a flyback diode connected with the relay module?
-Do relay modules usually include flyback diodes?
What about the solenoid valve - does it need its own flyback diode or is it unnecessary?
Finally, do I need to make sure that opto-coupling is provided?


texts: A x10 oscilloscope probe means that the voltage is attenuated 10 times?

texts:
I have a digital little oscilloscope that can handle up to 35 [V] in the input.
As far as I know, we use x10 probes for high frequency circuits and that stuff but my doubt: if I have a x10 probe, does it mean that I can input to my oscilloscope up to 350 [V] p-p (because it would be attenuated to 35 [V] p-p)?


texts: Why is wired Ethernet losing its speed advantage over wireless?

texts:
This has been bugging me for a while now. I did a couple wireless transmission courses back in my university days and it's a known fact that wireless transmission is hard. Partly because it's a shared channel, physical objects can be in the way, air provides quite a bit of loss, etc.
So why is wireless transmission catching up to Ethernet in terms of transmission speed?
We see MKBHD in this video going to some street with a phone and getting over 1Gbps. Surely a reserved and shielded Ethernet channel should give us 1Tbps right?
I feel we are just not trying enough on the Ethernet side of things. Is it the case?


texts: (cantilever) gas sensor with MOS technology - How does it work?

texts:
I'm having trouble understanding how the gas sensor with MOS technology works. I cannot find a study material with the basic principles of operation. I can find some subjects, but with information such as too deep knowledge, I have no in-depth knowledge on the subject.
Could someone please explain give me a link, document (PDF) that talks about this subject in a fundamental way how it works?


texts:
What is this component?

Can someone link me to an equivalent replacement, haven't been able to find anything

D5SV17


texts:
I was just wondering if there's any way for me to write VHDL code, that I can then upload to the Mojo V3 board?

The Mojo V3 IDE is Verilog/Lucid friendly, both languages that I'm unfamiliar with.

Thanks in advance.


texts: I have connected a 6a silicon diode to my psu and i supply 12v dc current trough that diode to my car audio head unit,But why is this diode is over heating? please anyone answer me.


texts:
I have circuit that has an audio connector that has the following diagram.

Audio connector is one that I am not familiar with. What I gather is that the rectangle on the left is the sleeve (entry point).

The tip    is pin 2.
The ring   is pin 3.
The sleeve is pin 1.

Is this correct or did I misunderstand how to read this symbol ?

Added:

Link to product page

Datasheet


texts: Connect multiple MPPT charge controllers to a single solar panel?

texts:
I have a small 18V/80W solar panel and some old lead-acid UPS batteries (that I got for free). About half of them are one brand and the other half are another, so I don't want to connect them all in parallel.
Is it possible to connect multiple MPPT charge controllers to the one solar panel? My understanding is that MPPT charge controllers try provide the optimal amount of load to get the maximum power from the panel, so I'm not sure if connecting multiple chargers to the same panel might result in the chargers essentially "fighting" each other, and if there's any delay in the chargers deciding the best load they might end up oscillating back and forth.
My understanding of MPPT controllers might be completely wrong, though.


texts:
Maybe it's my fault but I kinda dislike the design of the ESP8266 when it comes to wakeup from deep sleep via an interrupt.

AFAIK (without an external circuit) the ESP8266 can not distinct between a WakeUp and a Reset. Especially not if the WakeUp signal is bouncing (alternating in very short periods).

Question 1: Is that true?

To state my problem in more detail:

My WakeUp signal is HIGH in general - so the ESP8266 will not wake up and that is okay. Then suddenly my WakeUp signal will start to bounce, so it will be LOW, HIGH, LOW, HIGH, LOW, [...] (for seconds or even minutes) until it will be high continuously again. I want to use that bouncing as ONE wakeup but since the pin for wakeup is the same as for reset it will reset the board over and over again.

What I read about ESP32 is that I'm able to choose the pin I like to use for my wakeup signal and so I can use one that isn't a Reset pin.

Question 2

We are in deep sleep on an ESP32 and there is bouncing on my choosen WakeUp pin (!= Reset). Does the following holds true:
The first LOW will wake up the board and all following switches from HIGH to LOW will be ignored by the board until it goes to sleep again.

Question 3

Is there some simple external circuit or even some code to achieve the behavior of Question 2 also on the ESP8266?

Thank you so much!


texts: What is capacitance required for this 3 phase rectifier

texts:
In the diagram above I want to know the value and the rating of the capacitor that should be used for good rectification

The Line to Line voltage is 400 , and by relation
 Vdc =(3√2 VL)/pi=(3√2 x 400)/pi = 540 V

The ballast load has the power rating of 32KW .

This gives me the current of 55A dc .  How can I translate this to the capacitance value ?

One other Question . The generator has 3 phase wires and one neutral but the rectifier takes in three phase wires . Should I connect the neutral to this rectifier ? probably at the anode side of lower cathodes ?

Reference Link

Thank you


texts: Inductor burning out in a GPS bias tee circuit

texts:
I've got a tracking device that uses a Telit GE864-GPS combined GSM/GPS module. The GPS antenna is connected to the Telit module via a bias tee circuit, as shown below:

http://upload.wikimedia.org/wikipedia/commons/6/6c/Bias_t.png

The RF only port is connected directly to the antenna input on the Telit module. the RF+DC port is connected to the GPS antenna itself (A Siretta Alpha 7 -> Datasheet: here as you need to login to download it from their site.), and the DC port is connected directly to the board's 5V PSU (a 5V, 3A switching regulator). The capacitor is a 22pF 50V NP0 cap (Farnell) and the inductor is a 47nH, 400mA inductor (Farnell).

I'm running into a problem on several units where the inductors are failing due to overcurrent and burning out. Unfortunately, I'm having trouble determining what the cause of the overcurrent it. The antenna itself only draws 22mA max at 5V according to the datasheet so in theory, the inductor should be more than capable of handling that.

I've had a couple of units running continuously on the bench and out of 9 units, one failed after a week of continuous running. I then transferred that antenna to another working board, which worked fine for a few weeks. Then the system was powered off for a few days, then turned back on and the inductor failed a few minutes after powering on (glowed red for a few seconds then died). I've since transferred that antenna to a third board and the antenna continues to function. The remaining boards have all worked fine during this period.

I'm struggling the figure out what is causing the inductor to fail. It could be the antenna, but it's odd that I get  this momentary power surge (which lasts for a few seconds until the inductor burns out) but the antenna then continues to work fine.

I could potentially prevent the problem by sticking a resettable fuse in front of the inductor to prevent any surges from blowing it, but I'd love to find out what the cause of the problem is.

Any thoughts?


texts: Explanation for stability criterium microwave amplifiers

texts:
Given a general microwave amplifier circuit

For this amplifier (transistor) to be stable the the magnitude of the input and output reflection coefficient must be smaller than 1.

But why? What is an intuitive explanation for why the magnitude of the input and output reflections need to be smaller than 1 for this amplifier to be stable?


texts: Power amplifier - why is NF decreasing with freq. and I-V curve doesn't attain saturation?

texts:
Attached are the schematic of a PA with some relevant technical data, and simulations I ran. I'd like to ask a few questions concerning my results. Hopefully one of you will be willing to provide some insight, for which I shall be very grateful.

1) In the attachment NF vs. freq. the NF is shown to be decreasing as freq. increases for \$2<freq.<3GHz\$. Why does the noise figure decrease with frequency in this frequency range? Is this a normal behavior? What are the possible reasons in any case?

2) Why are there such strong fluctuations in gain for \$7<Vgs<12V\$? Why isn't saturation attained for \$ Vgs>7V \$ (I-V curves)? What are the possible reasons for that (fluctuations and not attaining saturation) and how may I determine the actual cause?

enter image description here


texts:
It is given in STM32 system memory boot mode APP note that bootloader stored in the internal boot system memory is programmed by ST during production.

Does this mean that if I buy a new STM32 microcontroller and want to load my programs into the microntroller I don't have do the initial in-circuit programming(ICP) for updating flash memory using jtag/swd programmer, and I can directly update the flash memory using USART or USB protocol using Flash demonstrator or DfuSe software?


texts: On some devices, the DC polarity symbol uses diamonds or squares for the poles instead of circles. Do these two styles represent any electrical of mechanical difference, or is it purely cosmetic?


texts:
https://www.allaboutcircuits.com/technical-articles/the-i2c-bus-hardware-implementation-details/

I read from this article that for the open drain there's nontrivial power consumption when the input is HIGH and the output is LOW.
The current flows from power supply, through the resistor and through the nmos to GND.

How is this non trivial power consumption when compared to the push/pull configuration where the inputs are HIGH and Vout is connected to GND through an NMOS?


texts: PCB base copper weight vs plating thickness

texts:
I am using Saturn PCB Design to help get the trace geometries to implement PCB differential characteristic impedances. I have some dimensions from the board house:

But I am confused on how to input the 1.4 mil copper thickness into the tool. It asks for both "Base Copper Weight" and "Differential Layer," and I'm not sure what these mean. Is base the thickness of the ground plane, and plating thickness the thickness of the traces (so in my case, both would be 1.4 mil?) Furthermore, there is a text image that says "Total Copper Thickness", and I'm not sure how that's being calculated.

I plan on using the outer layer for my traces (as shown in the bottom left "preview" picture).


texts: What does a multimeter read when you measure unstable DC-voltage

texts: When I have a Fluke True-RMS multimeter. Does the meter measure DC-RMS voltage or the average voltage?


texts: What type of Boolean logic circuit is this?

texts:
I need help confirming some hunches.  I'm trying to figure out what type of circuit this is:

Any ideas?
Also, I think the logic expression for this is:
D = (A AND B) OR (NOT(B) AND C)


texts:
Suppose you take a 2*10^2 resistor and a 0.40 inductor and make a series circuit with a voltage source that has voltage amplitude 30 and an angular frequency of 2.5×10^2 .

**Part F (The part that I need help on):

Construct the phasor diagram.

Draw the voltage and phasors with their tails at the origin of the coordinate system. The length of the voltage phasors is given in volts; the current phasor is not drawn to scale. The orientation and length of your phasors will be graded.

Previously found in other parts:

Impedence (Z) = 224 ?

Current (I) = 0.134 A

Voltage across the resistor (VR) = 27 V

Voltage across the inductor (VL) = 13 V

Phase angle with respect to the current (?) = 27 degrees

The source voltage leads the current

**Also, I don't know if this is fully important but the length of the source voltage vector (V) in the diagram is 30 (no units) and its angle is 48 degrees wrt x-axis. The vector for the current (I) is at angle of 21 degrees wrt x-axis and its length is not given.

I need the length and the angle of both VL and VR


texts:
I have an MCP4725 12 bit DAC from Sparkfun and i  am trying to interface it with raspberry pi 3

Connections :

Vcc -> 3.3V/5V of Rpi

Gnd ->Gnd of Rpi

scl and sda -> to scl and sda of rpi

out -> to DMM

and I tried to run this code: ADAFRUIT

What else i tried :
I tried to short addr pin with vcc and then with Gnd
I also tried to cut the tracks from pullups thats are given on the back side of the board
Problem

Even though I tried the connections ,The circuit does not seem to work .

Questions :

1)Is it possible to interface MCP4725 with Rpi ?
2)do I need to use level shifter for I2C pins ?


texts: Serial Communication via Mosfet using UART instead of PWM

texts:
Is it possible to send a uart signal to a mosfet driver instead of a PWM signal. I would like to establish wireless communication with a receiver and send it a data string using amplitude shift keying.

Can someone help me?


texts: Reason to Have an Air Gap in an Inductor

texts:
Why do we have the airgap ? Is it just to store energy?
I did find an explanation online, but it was hard for me to understand.


texts: Sequence multiple IR remote commands (button presses)

texts:
A bit of a story here: I would like to be able to quickly and easily turn on/off captioning on the cable TV box. Normally this would require 10(!) button presses.

It's hard to be sure, but I expect that no commonly available universal remote control can be programmed to automate 10 button presses.

Having formal training in electronics, I easily used an Arduino to record all the necessary IR signals (via a sensor/demodulator) to accomplish the function.

My first attack on this problem was to make a program running on an Arduino that would accomplish this function.  It worked, but it's such an over-kill...  Also, you need to wait for it to boot (1? second).  Edit: I could try modifying the board to shorten this boot time.

I don't have an EPROM burner, otherwise I would wonder about clocking a counter at 38 kHz and addressing an EPROM and using 1 bit to operate an IR LED (via a 2N2222).

If I were to stick with an Arduino, I think I would use the PWM to make the pulses.  (Before I enabled a 555 astable which did the driving).

What is the easiest way to get this done?


texts: I recently bought a 12V small computer fan(about 1"X1") and it was running rather slow when I checked it with a 9V. The package says that the fan requires 12V to run at an optimized speed, so is there a way/circuit that I can use/make that increases the voltage from 9 to 12?


texts:
For a project I am working on, I want to build a 9x9 monocolor LED matrix also with 9 push buttons to control the LEDs using the PIC. So far I have gathered that I think I will be needing shift registers to drive the cathodes and shift-register chips to drive discrete transistors for the anodes. I will also require shift registers for the push button inputs as well.(Please correct me if i'm wrong).

I am having trouble looking for relevant information online (e.g. what components to choose), can anyone give me some ideas to research or any relevant advice would be most helpful!
Thanks


texts: How do I measure the voltage across R3 (Va) in this circuit?

texts: This circuit has been troubling me for a few hours, I've been able to measure Vout and the Thevenin Resistance, however, I haven't been able to calculate the voltage (Va). Any help would be appreciated greatly. Thanks in advance


texts:
The meaning of the letters J and K in "JK flip-flop" was previously discussed here, and the meaning of the letter D in "D flip-flop" was previously discussed here.

What does the T stand for in "T flip-flop"?


texts: Reversible Constant Current Source (CCS)

texts:
I need a current source, that can work in both directions.
To make it simple, I need to generate a square signal in current.
I am currently using a simple H-bridge, but without any current regulation. All the current regulators that I found don't work for both negative and positive parts.

voltage range: up to 30 - 40 V

current range: few mA

period range: few ms

Do I need to use diodes and use separate regulators for the negative and positive part of the signal?

Can I find a H-bridge controlled by PWM that can deliver a regulated current?

Any other idea to solve this problem?


texts: What's the difference between an elastic buffer and an asynchronous FIFO? Are those just two different names for the same circuit?


texts:
I'm using AD7190 with STM32F103 for data logging. The datasheet of the ad7190 said that the DOUT/RDY falling edge can be used as an interrupt to a processor since it will go low to indicate the completion of a conversion. I'm using the continuous conversion mode of the ad7190, so I need to continuously monitor this pin. The DOUT/RDY pin of the ad7190 is connected to the MISO pin of the stm32f103.
How can I set the MISO pin of the stm32 as an external interrupt pin to detect the falling edge while it was set as MISO pin?


texts: Probe at low current load to measure voltage using oscilloscope

texts:
I have a circuit with a load where i'm measuring the current across the load with an ammeter and the typical current consumption of the load is typically within 10uA range.

When I connect my oscilloscope probe at the load in parallel to check the voltage response, the current consumption load is hitting my the current clamp (50uA) as set in my ammeter and everything back to normal once i disconnect my voltage probe from the load.

Can anyone please explain why?

Thanks in advance.


texts:
The title says it all.

I'm currently working on an Arduino project. The project involves connecting 3 - 6 different shields non which is a "Motor Shield".

They are VR, brain wave reader, GSM, GPS, TFT screen, and a camera.

What is the right way to calculate the power needed to be supplied to the total project by batteries?

What I know is that I have to calculate the amound of current withdrawn from each module in their highest peaks. Accordingly, I will choose the capacity of the battery that can operate the the amount of time I want.

Is  this the way it is done? Or am I missing something?
Is there any other concerns I have to keep an eye on?

Regarding the voltage, It shouldn't matter right? The shields are made specifically for Arduino, so if I powered it in the recommended range of voltages (7-12) I should be fine right?


texts: I'd like to hook up an LED to a cell phone's headphone jack. When there's audio, turn on LED, when there isn't, turn it off. Is the best way to go about this just using a npn transistor? Any links to a complete circuit? I know I probably will have to supply external power using 5v.


texts: How to stabilize this op-amp/MOSFET control system

texts:
I am creating a constant-current source and am having troubles stabilizing the control loop around U3, this is the circuit:

This next picture represents the plot of loop-gain of U3:

I've tried adding capacitor across R3, capacitor from U3 output to its non-inverting input and a series resistor between U4 and U3. I've tried experimenting with some values, but dont seem to get it right.

The phase margin is -57° and gain margin +43dB. Both values indicate instability as does transient analysis.

So, how do I know what to do to stabilize the control loop? I need to insert a pole somewhere below 2.5MHz to decrease ROC to 20dB? But then again there is a problem with gain margin.

I've also uploaded the LTspice files for anyone to try the simulation, they can be found here.


texts: What resistor type is best suited to constantly dissipate 10W?

texts:
I am trying to decide on the best resistor type for a 50V system with ~470 Ohm resistance.  This resistor will constantly be dissipating power.

Is a wirewound resistor the right choice?  Should I be looking into planar resistors?  And how can I determine when a heatsink is necessary for a resistor.


texts:
This is a two-part question:

Why do the so many projects that I see that use basic linear transformer power supplies (i.e., mains->transformer->rectifier->regulator) not have any kind of input protection beyond a fuse?  Is a fuse really going to help prevent damage to the circuit?  Are they assuming that it's going to be plugged into a surge protector, so it doesn't need to worry about excessive input voltage?
If it is a good idea to include more protection in a simple power supply, is a simple crowbar-type arrangement like this appropriate?

My thought process was that I just want the fuse to open and the whole thing to become inactive if anything goes out of spec, so during an overvoltage, I basically just want to short-circuit and blow the fuse.  The rule of thumb that I have heard is that your device should be able to tolerate during normal operation anywhere between 100-140 volts from a 115v nominal mains supply.  This means a peak AC voltage of ~198, hence the 200v TVS diodes.  The clamping voltage of common 200v TVS diodes seems to be in the 320-330v range, so a 300v gas discharge tube was chosen to take up the larger surges a little bit before the diodes reach their limit.  Anything more than the GDT can handle would probably just arc across the component leads and trip the mains circuit breaker or blow the power supply's fuse instantaneously, right?

Is this enough?  Should I also fuse the mains neutral and use a lower voltage TVS diode for D2 in order to open the circuit in the case of reversed hot and neutral?  It seems like it might be over doing it to try to protect against grossly incorrect mains wiring like that.  Also, now I'm starting to ask myself if it isn't even more dangerous to risk opening the neutral side of the circuit before the hot side fuse blows...


texts: Colpitts Oscillator Current and Frequency

texts:
Apologies if this has been asked before, but I couldn't find answers to my specific questions.

I built a transistor based Colpitts Oscillator and I've been confused by the difference between the standard formulas and circuit behaviour (both real and simulated).  The circuit is given below:

Originally, R4 wasn't part of the simulation - I added it after I built the circuit and measured the frequency on the scope.  The resonant frequency of the tank prior to R4 was approx 70kHz.  This, I can calculate using the standard 1/2*pi*sqrt(LC) and spice agreed.  However, the circuit on the breadboard measured 83kHz.  I reasoned that the breadboard contained quite a bit of resistance and I added 10 ohms to the tank.  Viola, spice now reported a frequency of 83kHz - exactly right.

So, my questions are:
1) How would I go about calculating the frequency considering the effect of the resistor?  I've seen other formulas that take account of the resistance, but when I tried them the frequency was reduced.  Also, intuitively, I would have thought that the damping effect of the resistor would reduce the frequency, not increase it.

2) I've noticed that the current circulating within the tank according to spice is roughly 12mA.  See image below:

I tried to calculate this current myself using complex impedance calculations, but I couldn't get the right answer.  The best I got was the following:

Here, I took the sum of all the complex impedances and the 9V peak reported by spice to arrive at the current.  Obviously the answer is wrong, but it looked suspiciously like twice the (spice) reported current.

The problem with a lot of the books I read is that they talk about resonant circuits where the driving voltage is sinusoidal.  With the Colpitts, the driving voltage is DC topping up the tank.

Any assistance would be greatly appreciated.


texts: Is it worth going to so much trouble with Ethernet differential tracks?

texts:
I am laying out a PCB containing an Ethernet connector with integral magnetics, and a Micrel KSZ8051MNL Phy. This is for a 100mbps application.

In an attempt to reduce EMI, and make the Ethernet data tracks as perfectly balanced as possible, and to match their lengths as closely as possible, I have ended up routing them in quite a curvy way.

Question 1: Is it worth going to this effort for such short tracks? The trivial way to lay out these tracks would have resulted in a difference of about 1.7mm.

Question 2: Is there any downside to this almost 360º loop?

(BTW, the Phy has integral terminators, which is why they don't appear on the PCB.)


texts: Is there any way to inhibit this latch circuit from locking up at startup?

texts:
Using an opamp (in+ is fixed 4V ref, in- is a square wave 5/1V), I have an NPN-BJT in the feedback network, and this BJT acts like a latch; once the output goes "high" the BJT pulls in- to ground, effectively latching the opamp to high output until power cycle.

Works perfect in a simulator.

But, in Real Life(tm) there is a quirk that the simulator misses; immediately after power-up, before the power rails and all inputs are stabilized, in+ is higher than in- (which takes some time), so the latch-up happens immediately, which is quite bad.

I've pulled my hair trying to slow down in+ a bit, but realized it's simply not possible. What I need to do is grounding the opamp-output for about 0.5-1us (i.e. disallowing the latch) until all is stabilized.

Is there anything I can do to achieve this? Board space is limited, so if I need an IC + discretes it should be about an SO8 in size.

(I was thinking about a monostable 555 but that short a pulse is a bad idea I think)

Schematics:

Explanation

The opamp (OPA2132) is connected as a comparator. In+ is a fixed reference to which in- is compared to. The whole circuit is a voltage monitor, so the output of the opamp is connected to a PMOS-gate (which is controlling the power line to the application).

The RED area: a TL431 voltage regulator sitting on a 5V Vcc-line. R1/R2 sets the working point to 5.5V, meaning that if Vcc rises to above 5.5V, the output (pin 3) is pulled down to 1V. If Vcc is below 5.5V, pin 3 is essentially following Vcc.

Now, disregard the BLUE area for a second and consider RED area + opamp; this works just as expected. When the voltage is tripped (> 5.5V), pin 3 goes low, meaning that in+ is higher than in-, and opamp goes "high".

So far, so good.

Now, the BLUE area is a latch feedback. When voltage is not tripped, in- is higher than in+, opamp is "low" and the BJT is cut-off, i.e. no latch. But when the opposite is true, when the voltage is tripped; in+ is higher than in-, opamp goes "high", BJT gets saturated and pulls down in- to ground. That is, the BJT permanently latches the opamp to "high" state.

This worked perfect in the simulator, but as I wrote above, it does not work in Real Life because - I think - the voltage rails hasn't been stabilized so in+ is initially always higher than in-, making the BJT latch immediately.

If I in this premature latch disconnect the BJT-emitter from ground and then re-connect it, the latch is gone and the whole circuit works as expected (latching only when the voltage is tripped).

For this voltage monitor to work as I want, I need the latch. That is; once the voltage is tripped, the only way to release it should be to power cycle the whole unit.

I yet haven't measured for how long it takes until the power rails and all inputs are stabilized, but is there any way to make the latch work as I want? Like, pulling the opamp output down to ground, once, for time X during the startup? Or delaying in+ for a while so in- manages to reach its initial level?

Or anything at all?

(If I sound too desperate it's because I am; I've been pulling my hair for days)


texts: MATLAB Simscape: modeling variable load with varying DC voltage

texts: I have a model for a solar array and a battery in MATLAB Simulink (simscape). and I would like to model a load given the power consumption over time. The load is connected to the battery the voltage of which varies due to charge and discharge. How can I do that?


texts: What is the minimum connection required to power a digital camera externally?

texts:
I have a Canon compact digital camera Model IXUS70 which I want to use for time-lapse photography.  The battery doesn't power it for long enough so I propose to gut an old battery and turn it into a power connector so I can externally power the camera indefinitely.

The battery has three connections:

labelled +, - and the third is unmarked, though I understand that this is a thermistor connection.

How should I connect this third pin, assuming that I am feeding 3.7 VDC into the + and - connections?


texts: How susceptible to ESD damage are JFET gates?

texts: Are the gates of JFETs protected against ESD transients? Is it best to include back to back zeners like with MOSFETs?


texts: what is the use of ultrafast diodes in wireless battery charger ckt

texts:
Instructable

I am working on a wireless charger that uses a ZVS Driver circuit for the transmitting end. This is its circuit diagram:

I have attached the instructable where this came from. Wireless Power Charger here


texts:
I bought a cheap SSR relay (SSR-40DA) on ebay and like to connect it directly to arduino,
Schematic on website (http://www.fotek.com.hk/solid/SSR-1.htm)  shows that LEDs already have resistors in the circuit, do I need to add additional 220R resistor to output pin or not?

Thanks.

P.S. It's not clear from this answer Wiring SSR with Arduino how to correctly connect this relay, sorry if duplicate.


texts: Decoupling capacitors upsetting 74HC74 output

texts:
I'm using LM331 to convert 0-10V voltages to frequency and a 74HC74 sets the pulses ON OFF time more equal.
The circuit below works in simulation:

(left-click to enlarge)

But I tried several times with breadboard from scracth and have the following problem:
When I add C7 or C6 for the regulator, LM331 still works but 74HC74 outputs zero voltage.
So any cap between Vcc of 74HC74 and ground makes its output zero. Without any cap the circuit works. But I want to add caos to regulator and Vcc pin for noise issues. I find this very peculiar why it doesnt work.

What can the problem be here?


texts:
I'm designing a pcb with a Sub-1GHz chip and I'd like to add a chip antenna on my design.
I choosed one of the johanson technology products, especially this one
https://www.johansontechnology.com/datasheets/antennas/0900AT43A0070.pdf
In the datasheet I see many references of matching network close to antenna.

The question is: Is really needed to place a matching network if the anntena's feed line has exactly the same impedance as antenna's input? (50 Ohm in my case).


texts: Programmatically switch betwean ground, power, signal for input port

texts:
I have this idea on creating a Atmel-based board with PS/2 connector for testing of old keyboards.

So I'm looking for a way to assign 5V, ground or signal to each pin of the connector after board has been manufactured. All 3 lines do exist - also I have 6 digital pins to control all this - but I'm not sure what is the best solution here.

My original idea was to have logic gate and then set of NPN - but that sounds a bit too complicated.

Any feedback is greatly appreciated!


texts: Elenco Digital/Analog Trainer XK-700K Output voltage off

texts:
A week ago, I was given a project by my professor to do part of it and then give it to another student.  After soldering the power supply section of it and testing the resistances/voltages, I get a voltage of -10.11V as an output of a -20V voltage regulator(LM337).  The regulator is connected up to a variable resistor, although I get a voltage range of 0.729 to -10.11V on it.

I am not able to ask my professor what might be affecting this , as I don't have class until next Thursday.
The assembly manual is here.

Edit: I was tired yesterday, and as such, wasn't really thinking about what to do.  I had gone through the troubleshooting guide on page 19 under "No voltage at variable output", and all of the causes were not it.  This morning, after studying the board, I realized that two diodes below VR2 were soldered with the opposing polarity.  I just soldered it, and I got a voltage of .7V CCW and -22V CW, which is within the 30% tolerance.  Thanks you for your answers!


texts:
I’m try to make a wideband noise source up to 150MHz, around 0dBm and as flat as possible, based on diode’s avalanche mechanism, plus some buffering and amplification stages. My questions:

What is pros and cons to use zener diode or B-E junction of a transistor.
In case of zener, what is the impact of breakdown voltage, bias current and junction capacitance (or any other characteristics of diode), on noise bandwidth, level and spectrum.
In case of transistor, is should be an RF/low noise one or a general purpose it is adequate?
Can I simulate this project on LTspice, since spectrum analyzer currently it is not available?


texts: Guidelines for sizing solar-powered electronics?

texts: Does anyone know of sizing guidelines or calculators for solar powering electronics? i.e. given power consumption, latitude and allowing for bad weather, accumulated dust and bird poop etc, calculate the size of solar cell and amount of storage to ensure that the electronics never run out of power?


texts: Different Voltage Battery Backup Circuit

texts:
I saw a circuit on a website to make a backup battery circuit for a rechargeable 12v battery circuit.

However, I don't anticipate regular power outages, so I believe that one non-rechargeable 9v battery will last for more than the life of this project.
I came up with the following circuit modeled after the first circuit (And a voltage regulator circuit I saw):

simulate this circuit – Schematic created using CircuitLab
Is it dangerous to mix different voltages like this? I heard it could be for transformers, but what about a battery? Would the circuit only use the battery if the transformer is disconnected, and finally, does it look like it would work?

Thanks!


texts: Does transmitting break over FTDI chipset yield a binary 0 received on the receiving end?

texts:
I send breaks (using Tx) over FTDI FT232R chipset using two ways:

a. Using the BREAK command in the operating system (Windows 7 and Ubuntu)
b. Gating the Tx line for an arbitrary period

I connected the Tx pin to the Rx pin of the FT232R (loopback test) and used a variety of serial consoles to read the Rx input

I always got a binary 0 in both case. Each case individually behaved so:

i. Using the BREAK command, I recieved binary 0 when the BREAK command was made active (BREAK is active low)
ii. When gating the Tx line, I recieved binary 0 when I forced the Tx line low

This does not seem right to me.

The only time when the UART Rx can get "confused" between BREAK and a binary 0 transmission, is when the BREAK switches the line low for exactly 9 bits duration and then brings the line back to high (making the Rx side misinterpret as a stop bit), but this breaks a definition of BREAK which requires the line to be held low for at-least 10 bits duration.

So my questions are:

Is this expected behaviour ?
If you do a loopback test on your FTDI chipsets can you reproduce this behavior (implying I have bad drivers/faulty chipset)


texts: What other standards are there than IEEE 315 and IPC?

texts: What other standards are there than IEEE 315 and IPC for creating schematic symbols and component representations??


texts: How do use use an Arduino with a Stepper Motor?


texts: Why is it a wrong practice to calculate voltage drop across current source?

texts: I understand that an ideal current source always delivers the same current regardless of voltage applied across it. However, in a circuit with no switches, voltages and currents do not change over time so the current source should maintain a constant voltage across it. Why is it wrong to consider voltage across it when doing KVL in meshes?


texts: Turn on/Turn off circuit using one momentary button. Also, turn off the circuit using a command from NodeMCU

texts:
I have this 5v and 3.3v voltage regulator circuit using 12v input voltage. This voltage regulator circuit is used to powerup my NodeMCU and several sensors.
Now, I'm having problems creating a circuit that:
1.) If plugged in, button hasn't been pressed yet, circuit is OFF.
2.) If plugged in, button is pressed, circuit will TURN ON.
3.) If plugged in, button is pressed again while circuit is Turned ON, circuit will be turned OFF.
4.) Turn OFF circuit when a command is received from NodeMCU.
So far, only 1-3 is the circuit I have. Your answers will be a great help especially circuit diagrams. Thank you.


texts: How to find the power delivered to the load?

texts:
I'm trying to solve a homework problem to find the power delivered to the 10Ω load.

So far I found the total resistance, which is 12Ω.
And I think I have the right formula to work out the power, correct me if there's another way or if I'm wrong.

My calculations so far

My next calculations

Any help will be greatly appreciated. :)


texts: replacing disposable lithium-thionyl batteries with rechargable lithium batteries?

texts:
I have a device that takes 2 disposable 3.6 V 1/2AA 1100 mAh lithium-thionyl batteries and I would like to replace them with rechargable ones. It is a device that measures angles in wireless mode, and I only get a life span of 10 hours for 2 disposable batteries, not nice for the environment at all.

I understand I need to make sure the voltage matches.  But what about the mAh that it outputs to the device?  Does it have to be the same?  Can they be higher?  I'm having problems finding an exact match...which is what brought me here.

And also does it have to be a lithium thionyl chloride rechargable or can it be a different type? I am clueless when it comes to electronics...


texts: Why does microwave test equipment use N connectors?

texts:
Almost all of the microwave test equipment I've ever seen and used has N connectors, with exception of some scopes that use either custom fancy BNCs (keysight does/used to do this)) or SMA.

Exceptions that I know of are VNAs which seem to use special connectors (but the ones I've used are also rated up to 110 GHz and used 1mm-based connectors).

Of course, there is nothing wrong with the N connector - in fact I like it, it feels rugged and like it can take a good bit of use (is this the reason?).

However, every single occasion I've worked with the instruments, or seen someone work with them, the first thing they do is put on a N-to-SMA (or 3.4mm or 2.4mm) adapter. So why not just put those connectors on the equipment in the first place? Is it really just the ruggedness, some other reason I'm missing, or is this some silly "because it used to be that way and nobody likes change"?


texts: Sallen-key second order bandpass filter low frequency response

texts:
I have designed a Sallen-Key bandpass filter with a centre frequency of 5000 Hz, a Q factor of 2 and an H0 of 5.

I am trying to figure out why it responds as seen here to square wave with a frequency of 200 Hz

My interpretation is something like this
but I'm really struggling to figure why it ripples instead of just spiking and why it looks more like an impulse response


texts: Poor RF communications : looking for advices

texts:
I am in charge of a temperature monitoring and controlling project in a new building with 7 floors and 14 rooms by floor.

I installed last week thermostats devices in each rooms permitting to send user set point temperature to a master device (2 by floors located in corridors) which are driven the underfloor heating.

The system works fine, but sometimes, I have some communications problems between thermostat and its master device due to the fact that the building is a bit too long for a good communication.

All communications between devices is done by RF 868MHz.

I am looking for ideas helping me to improve the RF communications between devices

HoneyWell Devices list :

Thermostats DTS 92 : http://www.honeywelluk.com/products/Temperature-Controls/Temperature-TPI-Control/DT92E/
Master Evotouch : http://products.ecc.emea.honeywell.com/france/ecatdata/pg_evohome.html
Heating driving HCC80


texts:
I am making a large prototype of a device that requires a large PCB (about 15x20inches).
I am able to etch my own circuit board in copper laminates, but I cannot find large enough laminates.

Is there a good source of buying large copper laminate? Is there a way to make my own out of copper foil?

I have checked Alibaba and aliexpress and they only have a few suppliers that make laminates that big.


texts: Need help identifying and finding similar SMD variable resistor

texts:
The component appears to be damaged, but the datasheet for the board in question shows that this is a 47k ohm variable resistor. Looks like a trimmer, but not 100% sure.
However, I've been trying to find a similar looking component with the same rating to no avail. Most SMD trimmers that I have found with a similar rating have two terminals in one side, and one terminal on the other. The board in question is a controller board attached to a LCD panel.
Datasheet: https://datasheetspdf.com/pdf-file/762847/AUO/M200RW01-V0/1


texts: Differential emission of LED die under changing current?

texts:
This is going to be a bit too specialist for most people, but here goes...
Normally we treat LEDs as point sources. However, they are actually flat chips that emit light from the surface. I am assuming that the emission is not uniform across the chip. If this is so does the uniformity of the relative emission across the chip remain constant under varying current? Or do changes in current result in different areas of the chip lightening or darkening relative to each other?


texts: In a transistor radio, what gets amplified? Is it voltage? Is it possible for a transistor to amplify voltage? I looked at the transistor Wikipedia web page, but it didn't say anything about whether a transistor amplified voltage.


texts: Does position error from accelerometer still build up quadratically when using Kalman filtering?

texts:
I want to implement an inertial navigation system that uses a basic IMU for indoor position tracking. From all the things I've read you need to assist the IMU with something like GPS or other means of position sensing since the error in position grows quadratically with time.

I looked into Kalman filtering and am confused why this doesn't fix the issue of quadratic position error. Since youre sensors only measure acceleration and gyro (and maybe magnetic field), you must get position from your estimated state, not from your estimated sensor reading. If this is the case then you update your position state with only the error on the accelerometer each time and not the double integration of the accelerometers past errors, right?

I may be just confused but I feel like Kalman should get rid of the quadratic error.

If this is not the case, then why? And what techniques do people use for reliable indoor position tracking with IMUs?


texts: Transmission via RF433Hz Transmitter/Receiver pair failing AVR

texts:
I am trying to send data wirelessly through a RF433Hz receiver/transmitter pair, but nothing seems to want to work.I want to the transmitter to continuously send a number (0x81) to the receiver when I press an active low button, I am expecting to see Ox81 on the receiver side but I am not seeing that.

int main( void )
{
        //initializeUART ( BAUD , DoubleAsync, DataBitLength, Parity, Stopbits )
        iniUSART0( 1200 , 0 , 8 , 0 , 2 );

        //Code for transmitter
        if(Transmitter)
        {
            DDRA = 0xff;
            while(1){
                        if( bit_is_clear(PINB, 0) )
                        {
                             data = 0x81;
                             TransmitData(data);
                             PORTA = 0x81;
                        }
                     }
         }

      //Code For receiver
      if(Receiver)
      {
      DDRA = 0xff;
        while(1)
        {
                     while(!flag)
                     {
                        data = ReceiveData();
                        PORTA = data;
                     }
        }

}

The methods have been put in a separate header file and can be seen below

 unsigned char ReceiveData(void)
    {
        while ( ! UCSR0A & ( 1 << RXC0)) //Check if there ids data waiting for you
        {

        }
        return UDR0; //return data
    }

    void TransmitData( unsigned char data)
    {
        while( !UCSR0A & ( 1 << UDRE0)) //Check if uC is ready to transmit
        {

        }
        UDR0 = data; //Transmit Data
    }

    void iniUSART0(int baud, char doubleAsync, char dataLength, char parity, char numberOfStopBits)
    {

        int UBRR_Value = lrint ( (F_CPU / (16L * baud)) - 1 );

        UBRR0H = (unsigned char) (UBRR_Value >> 8);  //Upper Baud number
        UBRR0L = (unsigned char) UBRR_Value; //Put remainder in lower bits

        //Enable reception and transmission
        UCSR0B |= (unsigned char) (1 << RXEN0) | (1 << TXEN0);

        if(numberOfStopBits == 2)
        {
            UCSR0C |= (1 << USBS0);
        }
        else
        {
            UCSR0C &= ~(1 << USBS0);
        }

        //Use an 8-Bit length data bit
        UCSR0C |= (unsigned char) (1 << UCSZ00);

        //Double Asynchronous mode?
        if(doubleAsync) UCSR0A |= (1 << U2X0);

        //Set the data bit length

          if ( dataLength == 6) UCSR0C |= ( 1 << UCSZ00 );
          if ( dataLength == 7) UCSR0C |= (1 << UCSZ10);
          if ( dataLength == 8) UCSR0C |= (1 << UCSZ10) | (1 << UCSZ00);

         if(parity == 2)UCSR0C |= (1 << UPM10); //Sets parity to EVEN
         if(parity == 1)UCSR0C |= (1 << UPM10) | (1 << UPM00); //Sets parity

 to ODD
}


texts: How to make use of 'Power ON Reset' while there is noise in Power?

texts:
I'm using Nuc240LE3AE(Cortex M0) to run a code that is developed.
I want to run the code on startup for which (POR)Power On Reset facility is used.
Normally this is Enabled in the Micro-controller and as per the datasheet;

  When powered on, the POR circuit generates a reset signal to reset the whole chip function, but noise on the power may cause the POR active again. User can disable internal POR circuit to avoid unpredictable noise to cause chip reset by writing 0x5AA5 to this field.
         The POR function will be active again when this field is set to another value or chip is reset by other reset source, including:
  nRESET, Watchdog Timer reset, Window Watchdog Timer reset, LVR reset, BOD reset, ICE reset command and the software-chip reset function

The code works perfectly on Development board during startup but in the target board so developed, is restarting itself after sometime as mentioned in the datasheet due to noise(assumption).
But if I disable POR in the code, does the Micro-controller fails to execute the code at 'Power On' from next time onwards (In case of power failure)? if so, How can I overcome this situation?


texts: What audio sampling rate should be used for a toy?

texts:
I'm trying to work with my overseas vendor and they are not really providing a lot of information.

We are working on an educational toy that will give you facts and then asks questions.

We will have A LOT OF human speech and a handful of sound effects.

I'm trying to fit as much audio on the chip as possible.

What sampling rate should I use for voice?  11.025 KHz? 22.5 KHz?
What sampling rate should I use for the sound effects? 22.5KHz?

The speaker is a 'cheap' toy speaker...not high fidelity.


texts: How to replace a SMD capacitor on a raspberry pi?

texts:
(Note: also posted first in raspberrypi stackexchange, but not a single answer yet)

While desoldering the GPIO, I accidentally broke the capacitor C13 of my raspberry pi model B (2011.12 Rev7).

It is the capacitor between RG3 and the GPIO pins.

Looking up the schematics, it appears this cap is a 10nF cap connected on the 2V5 line to ground, parallel with C15, which is a 10µF. So it looks like this is a decoupling capacitor, but why the low value ?

I spent about two hours searching for a similar cap in various salvaged components. I finally found one on an HP dv6000 internal wifi board. (I had to check every value I desoldered, one by one, kinda tedious).

I did not solder it back yet, but i'll soon do.
I also did not tried powering my pi with the cap missing.

I wanted to know if there was any way to know that everything was back into order. What is the exact purpose of that cap, and how can I test that I soldered it correctly ?

Also, do you have some advice about how to solder it ? That piece is about half a millimeter long, maybe less than that. I got tweezers and head-mounted magnifying glasses, but I feel like I'm going to struggle a bit, especially because I only have 1mm thick solder.


texts: Output 2 PWM waveforms with 90 degree phase shift

texts:
So far, I was able to get two outputs at the correct resolution (35 kHz-75 kHz at a resolution no worse than 0.7 kHz) using the code below. I'm wondering, now, how I can get a phase shift between the two PWM outputs (which both use the 16-bit Timer1 and ICR1).

I tried writing the line TCNT1 += 1/freq/4; in between the last and second to last lines of code (OCR1A=... and OCR1B =...), but this did nothing.

   //set port B to output
   DDRB |= 0xFF;

   // wgm mode 1110 (fast pwm w/ TOP = ICR1
  TCCR1A |= 1<<WGM11 ;
  TCCR1B |= 1<<WGM12 | 1<<WGM13;

   //set OC1/A and OC1B on compare match w/ ICR1 , clear them at bottom
   TCCR1A |=  1<<COM1A1 | 1<<COM1A0| ;
   TCCR1A |=  1<<COM1B1 | 1<<COM1B0 ;

   //pre-scaler = 1
   TCCR1B |=  1<<CS10;

   ICR1 = 16000000/freq; // input compare value = (clock freq) / (desired freq)

   // 50% duty cycle on OCR1A/B
   OCR1A  = ICR1/2;
   //TCNT1 += 1/freq/4; //this line did not do anything
   OCR1B = ICR1/2;


texts:
Why does CAN Bus represents signals with an inverted logic, high voltage for a logic 0 and low voltage for a logic 1?
Is there any advantage in doing so?


texts: Operational Amplifier (op amp) with different in

texts:
I have this circuit:

It's a basic op-amp that V_out will be like:

$$V_{out} = -V_{in} \frac{R_2}{R_{in}}$$

but I can't find V_{in} and R_{in}.

Simulating, I know that, if R1=R2=R3, then V_out = V_1 + V_2, but what happens when R1 is not the same than R2 or R3?

Thanks!