texts: Address-free communications between microcontrollers in any topology

texts:
Suppose I have 9 microcontrollers each on their own PCB, connected in a square grid. Is there a way I can get a single node to communicate to all the other nodes, be able to address them individually, but with no explicit setup for addressing?
For example, the master node broadcasts over the bus "Hello! I am the master!".  The master node is initially designated as master by toggling a switch.
The slave nodes generate a unique ID based on their serial number and broadcast over the bus "Hello! I am serial XXXXX".
The master node can then 'discover' all of these slave nodes, and send instructions to each of them individually.
I was initially leaning towards CAN bus as it is theoretically possible to do this, but the problem is topology and termination. CAN requires a bus topology with minimal stubs, and termination resistors at either end. In my application, I do not know which node will be at the end as they are in a grid, or even which board specifically connects to which other board.
Is there some kind of protocol that allows for this?


texts: Model train incandescent (wheat grain) bulb to LED

texts:
I watched and was inspired by the following video.
Add Directional Lighting to a Bachmann BIG Hauler using Diodes and 1.5V Grain of Wheat Bulbs
I have a Bachmann 49 Santa Fe locomotive. It's older yet is largely the same as the 4-6-0 models. I am also very much a novice when it comes to components and electronics. I am mostly self taught via various personal projects and tinkering with LEDs and Arduino.
I understand the concept of using diodes to create directional lighting. I purchased SMD Leds (0603).

LED is heavy duty & Super Strong, Resin cover to protect the LEDs, LED size: 0603 LED (0.060.030.03 in.)
LEDs work in 3-3.3Vdc directly, 5V/9V/12V resistors are available for different voltage battery or power supply used

I corresponded with the fellow that made the video. He had this to say:

LEDs are quite a bit different than old-fashion incandescent lights.  Two keys - the LED needs a certain voltage before it will emit decent light (3V for example), but an LED also needs to have its current limited (somewhere in the 10mA to 20mA range).   The simple method is to add a resistor in series to 'drop' the rest of the power supply voltage and to limit the current.   The problem with trains (using simple variable DC power supplies) is that the voltage varies so much.  IF the supply voltage was fixed at 12V, then a 1K resistor would drop 9V and limit the current to 9mA (I=V/R = 9/1,000 = .009A or 9mA).   The question is, what about when the loco is going slow?  You could decrease the reactance to 500 or 400 Ohms.

I understand his points yet I do not know how to move forward. I'd like to at least be able to use the LEDs, even if I do not have directional lighting. Please advise what method or components I might need.


texts: Why does 4 wire SPI read operation need me to read MISO line on every transmit operation?

texts:
I wish to read a SPI slave device. Here's what I thought the procedure would be like :
CS_LOW

SPI_Write(slave_address)
SPI_Write(register)
SPI_Write(0x00)            //dummy byte
data = SPI_Read()

CS_HIGH
However, this doesn't work. To make it work, here's what I have to follow:
CS_LOW

SPI_Write(slave_address)
temp = SPI_Read()
SPI_Write(register)
temp = SPI_Read()
SPI_Write(0x00)               //dummy byte
data = SPI_Read()

CS_HIGH
Why do I have to read the data on MISO line even when I know there will be nothing desirable?
PS: The SPI Read() and Write() functions are just my own implementations, nothing particular to a single MCU.
Edit : As requested, I am providing some details on the MCUs.
I am using two MCUs - STM32F303VCT and TI TIVA123GH6PM. Both the MCUs require me to follow the said procedure.
Here's my implementation of SPI transmit & receive function on STM32
uint8_t SPI_rdwr(uint8_t data)
{

    *(__IO uint8_t *)&SPI1->DR = data;              //send data

    while(!(SPI1->SR & SPI_SR_TXE));                // wait till TX buffer is empty

    while(SPI1->SR & SPI_SR_BSY);                  // wait if SPI line is busy

    while(!(SPI1->SR & SPI_SR_RXNE));               //wait till RX buffe is NOT empty

    return *(__IO uint8_t *)&SPI1->DR;          //return data if data received on MISO line

}


texts:
I'm using a TPS63060 regulator and according to its manual there should be typical 66uF capacitance on the output, please see this screenshot:

In order to achieve that I'm planning to use three 22uF capacitors plus one 1uF cap (as per TPS63060EVM, usually I use 100nF but in that EVM they're using 1uF for some reason, so I just follow that). My question is simple - should I put them all in one line and then connect load past these capacitors, like here:

Or can I arrange them in this order ("checkerboard") to save some space? Would that affect any output characteristics? Thanks!

UPD. After all the answers my final layout is this:

And 3D view is here:

Having this board tested I've got less than 15mV ripple! Thanks to everyone!


texts: Inexpensive switching regulator with internal inductor & diode

texts:
I'm trying to minimize part count and cost of my project.  It needs to have a 6V power rail with about 1.5A peak current from a 12V input.  I'm shying away from a linear regulator because of the power dissipation but I would like to keep cost and part count down.

Do switching regulators exist with internal diode and inductor to match these parameters or would it be less expensive to have a linear regulator with a big heatsink?


texts: Why can Ohm's law be used in a linear circuit with multiple equivalent resistors without being given current?

texts:
I'm exploring voltage dividers and am puzzled by the conclusion made by the YouTuber in this video:

"If you apply Ohm's law, you find that 1 V spread across two equal-value resistors gives you 0.5 V in the middle [. . .] and as you would expect, four equal-value resistors would give you 0.25 V, 0.5 V, and 0.75 V."

https://www.youtube.com/watch?v=XxLKfAZrhbM&feature=youtu.be&t=13s

I'm trying to work this conclusion out mathematically to try and make sense of it, but am not having much luck. Could someone please explain?


texts: How does a selection logic for Conway's Game of Life work?

texts:
In this implementation of Conway's Game of Life, they talk about using two layers of PIPO shift registers to select the the current and surrounding cells. I can think of somethings like this:

Suppose the cells are:

 1  2  3  4  5
 6  7  8  9 10
11 12 13 14 15
16 17 18 19 20
21 22 23 24 25

Then the there are three arrays of input, i.e. 25 21 22 23 24 25 21 (extra entries for wrap around), 5 1 2 3 4 5 1 and 10 6 7 8 9 10 6

Let the logic work on first three cells of each  of arrays, i.e. on 25 21 22, 5 1 2, 10 6 7 to get the ouput of 1 and latch using D-flip flop and so on.

I believe in some way we could shift the rows altogether from 5th 1st 2nd to now 1st 2nd and 3rd using another shift registers maybe?

Note that the logic unit can be implemented fairly easily and I have already made one so it is no big problem.

There has to be some way to not make 25 logic units (each 8-9 ic's).
What do you people think?

I have also thought about using some shift logic like this which looks very promising with a decade counter for the rows.


texts: Get -50V to 50V range from battery output

texts:
I have the following problem: on the system which is battery-powered(4S1P Li-ion battery, 14.8V) I need to create outputs from -50V to 50V. The system has microcontroller on-board.

I am baffled on how to do it. Initially, I planned on using bipolar DAC which would give output of +/- 5V or so and then amplify it with gain of 10 to get total +/- 50V.

The problem is, how to get power supply with range from -50V to +50V from the 4S Li-ion battery? I am familiar with concept of having two 50V sources, then connecting the + of one source to the - of another and using that point as common ground. Total current needed at +/-50V is 300mA. Loads are resistive.

Am I allowed to connect in this topology using two boost converters(switchers)? Would it work?

Thanks;
D. Petric


texts:
I am trying to simulate an RS master slave flip-flop in Logisim, and I have encountered the "Oscillation apparent" error. What does this error mean and how is it resolved? I am required to use two nor gates for the basic RS latch implementation and two of the basic latches with a clock signal for the master slave flip-flop.

RS master slave flip-flop

RS flip-flop (latch)


texts: Help understanding practical transistor considerations?

texts:
So first, sorry if I make some incorrect assumptions or statements. If I do, just correct me and forgive my ignorance.

It seems like everything I've been taught so far in classes about transistors and CMOS circuits utilizes an idealized model to get the concepts across, but I still feel like I don't have the tools to design a circuit for myself, where certain parameters aren't provided to me beforehand. I'll try to list exactly what it is I don't understand:

How do I decide the timing variables for a circuit implementation? I understand its application specific, but how do I know if I should choose components with relatively low delay or if I can afford high delays? How do I quantify my delay requirements? Maybe I start with, say, what I want my throughput to be at the circuit output, and work backwards down to the transistor level?
Related to the timing thing, how do I know what scale I should use for my transistors? My assumption is its some combination of allowable space, monetary cost, and the delay tolerances needed for the application. That seems like an awful lot of things to juggle. Are there any rules for determining this?
Finally, what about non-ideal effects like input capacitance? It seems like I'd I just use this as a guide to make sure that my desired clock frequency does not suffer severe attenuation from parasitic effects. Or do these non ideal effects have a much different role in choosing parameters for the circuit?

I think that each point is related enough to warrant making only one question, though I can split this into multiple questions it turns out each point requires deeper explanation than I initially thought.

Thanks in advance for any help you can provide.


texts: Can I control multiple stepper motor drivers from one controller?

texts:
I need to drive 6 stepper motors in open loop with 1/4 microstepping. The application requires all 6 motors to move by the same number of steps at the same time.

There are no sensors of any kind on these stepper motors. They are homed by commanding the maximum number of possible steps in order to run the actuators up against a stop. Therefore I don't need any feedback on the control side.

Can I use a single-axis stepper controller to control 6 drives in parallel?

The diagram below shows 3 parallel drives and one controller, in the configuration I would like to use:


texts: How to simulate Wi-fi signal strength indoor environment?

texts:
I want to simulate Wi-fi signal strengths received by a mobile moving around in X m3 that contains N access points. I must take into account the effect of walls and if possible the effect of moving humans.

What tool can I use? Free if possible?


texts: Is there a SSR like device that can switch at kHz frequencies?

texts:
I'm designing an industrial control system that incorporates several peltier devices.

As I understand it, these devices are more efficient when driven with a constant voltage, vs being cycled every few seconds.

What I would like to do is drive the peltiers using PWM in the kHz range, and run the power through an inductor to limit the current ripple.

The issue is that my go-to device for high current control is an SSR like this: AD-SSR6M12-DC-200D
Afaik, these will not work at kHz frequencies; and at lower frequencies the inductor becomes excessively large.

So here's what I'm wondering. Is there an industrial type device similar to a SSR that will work at kHz frequencies? Ideally I would like to keep the isolation feature as well.

I know I could build my own MOSFET circuit to accomplish this, but a reliable off the shelf device would be preferable. Does such a thing exist?

My peltiers, and the PLC outputs are all 24 volts. The peltiers draw 4.2A at 24V

Link to Peltier Assembly.


texts: Is there any difference between the assembly instructions of ARM MCUs from two different corporations?

texts:
I'm curious to know, are there any differences between the assembly instructions of ARM MCUs from two different corporation? For example between an Cortex-M3/4 of NXP and TI or ST or other corporations.

Some of my friends say me that they have no difference. Is that correct?


texts: Inverter Design - What DC input voltage for most efficient DC to 120VAC inverter

texts:
I have seen several online circuit diagrams for a DC to AC inverter.
Commonly many inverters use a transformer to step up 12V to 120V.  I understand that inverting from DC to AC requires additional components, and that the transformer only induces 12V to 120V, so it doesn't make AC out of DC (that is done by the rest of the inverter circuitry).

The question is, given a choice of any possible voltage into an inverter without a transformer, what voltage would result in the inverter producing 120V RMS naturally?  Is it 170VDC?

So once again, in an inverter design without a transformer, what DC input voltage would result in 120VAC naturally?

Ultimately, what I am trying to determine is what is the most efficient design for a DC to AC inverter.  If by inputting a specific voltage, one can omit the transformer normally found in a DC to AC inverter design, then that reduces the number of components in the design (and naturally increases efficiency since the transformer isn't 100% efficient).

However my question isn't intrinsically about simply being able to remove specific components (such as the transformer) from the design.  I am looking for the most efficient design, with or without any specific componentry.

What would the (DC) input voltage for that DC to AC inverter design be?


texts: why does FLASH_ErasePage reset my STM32F103C8?

texts:
Here is my program to write with EEPROM emulation in my stm32f103 flash memory.
void WriteEEPROM(char State){
uint32_t startAddress = 0x8019000;
FLASH_Unlock();
FLASH_ClearFlag(FLASH_FLAG_EOP|FLASH_FLAG_PGERR|FLASH_FLAG_WRPRTERR);
FLASH_ErasePage(startAddress);

    switch(State)
{
    case 1:FLASH_ProgramWord((startAddress+(0*32)+2),MainInfo.AZ);break;
    case 2:FLASH_ProgramWord((startAddress+(1*32)+2),MainInfo.EL);break;
}

FLASH_Lock();

}
but after calling this function it resets my MCU. I need to know why erasing the page 100 makes my MCU reset.


texts: Designing a haptic feedback motor vibrator circuit

texts:
I'm having a Vive Virtual Reality device which has one digital output pin.
Here is the specs for the digital output pin:

My plan is to use a 2N2222 transistor connected to that digital output, with a reverse diode parallel to the vibrator motor to protect for reverse back current from the motor inductance.
Is it sufficent ? is there any other alternatives circuit diagram that would work ?
I plan also to connect several motors, is one transistor like 2N2222 enough for driving 3 motors, which one motor consumes 300mA at peak, motor voltage 12V ?


texts: Is there a point in adding a 1 Ohm resistor to this LED circuit?

texts:
I am trying to figure out an appropriate resistor value for the following circuit.

simulate this circuit – Schematic created using CircuitLab

Input voltage - 3.3v
Blue LED, forward voltage 3.3v
LED : APT3216VBC
My maths tells me that driving that LED at say 12ma, means that the resistor should be:

3.3-3.3/0.012 == 0

Checking with some LED resistor calculators, they suggest a 1 ohm resistor : http://led.linear1.org/1led.wiz

Given my voltage drop, and input voltage, what does the addition of this 1 ohm resistor actually make to the circuit?

Thanks


texts: ADC value always display 2.1v when no load connected, how to resolve?

texts: I have an ADC and connect the ADC to a piezo. When the piezo did not generate voltage or no voltage supply between Vin+ and Vin- the ADC always display 2.1v. I tried to put a 10 megaohm resistor between Vin+ and Vin- but it's doesn't resolve my problem. How to resolve this problem ?


texts: Few questions about basic concepts in electronics

texts:
So I'm rather new to electronics and I'm struggling to understand some basic concepts because I picked up little information from many different sources so it's starting to get confusing :/

Why does current flow from positive to negative when electrons flow negative to positive? I thought current was the flow of electron
I think question 1 will answer this but why do you need to connect both sides positive and negative in order to power something? i.e. led
Why does voltage keep on rising and falling in an ac circuit?
I heard that ground is basically the negative side of the power source as it has 0 volatage(potential) but I thought when powered by a 1.5 volt battery the entire circuit had 1.5 voltage all around.

thank you :D


texts: doubt on taking vertical pitch for dip packages

texts:
I have one doubt on taking terminal row spacing from this below picture.
In this picture, which one have to take — eB or E?


texts: The RX of a BLE device needs to be on to wake it up via BLE?

texts:
So some BLE devices have sleep mode which allows it to consume less power (significantly less, in the order of uA). In this state (I think) the radio (RX and TX) is off. So there's any way to wake it up from sleep mode via BLE?

OBS: Just for CONTEXT, the devices which I'm referring to are these CC2541,nRF8001,nRF51822...


texts: Why do the Sparkfun and Adafruit Eagle libraries use smaller footprints than the manufacturer's recommended land pattern?

texts:
I'm comparing two datasheets from Micron and Infineon to the Sparkfun and Adafruit footprints for TSSOP-28

Both the footprints use an SMD pad size of 1.0x0.3 mm, while the manufacturers recommend something closer to 1.3x0.4.

Why would they do this? Should I undersize my own footprints?


texts: Oscilloscope makes my mains (fuse box) group go down

texts:
(Don't know if I should make a new question, but it's partly related to my previous question).

I bought an old second hand oscilloscope (see Is my oscilloscope working or not?), a Philips PM 3253.

After some initial problems (and help of Electrical Engineering) I got it to work, however, except for the first half an hour, now every 10 minutes the mains group of the house goes 'down'... I don't know the exact English term... It means I have to go to the 'fuse box' close of the house to turn on the group switch back on.

Is there some easy solution for this or things to check on the oscilloscope, or is it some setting causing it?

(My electrical knowledge is not high)

At the end of the day I could have the power on for half an hour on without having the computer (on the same group on). Today I used a separate power mains outlet for the oscilloscope; maybe I put too many devices on an extension box. I will leave both on for an hour to see if it helps.

Update: I did some more testing and the solution was putting the power of the oscilloscope directly to a wall outlet (and not running through extension outlets).

Also I have added a cable to ground from a wall outlet to the oscilloscope GND input on the back.

I still have some problems with the oscilloscope but I will spend another post to it after I did some more tries to fix it myself. Thanks for your help!


texts: Battery charging- Float mode and boost mode

texts: Based on my knowledge on batteries (AGM), the initial battery charging (for ex. a 12V, 200AH battery and a 24V, 20 amp charger ), takes not more than 2-3 hours for the first 70% charge and then it takes like 4-5 hours to charge to 100%. Why is that the initial charging happens so fast ?


texts:
For the circuit given below the voltage across the resistor is definitely 5V. If we add more than two sources the voltage will remain same as before.

If we try to analyze the circuit with superposition then first we have to make one of the source inactive. If we make one voltage source inactive then we can find the voltage 0V.

After that we have to make inactive the another source. At that time the voltage remains 0V.

So if we add the two voltages according to superposition theorem the voltage across the load is 0V. How???


texts:
I'm working on a project to make a wristwatch similar to this one:
Now I have the ability to make flexible PCBs since I accidentally bought some crazy thin copper clad. I obviously want to use SMD LEDs since they're pretty small. What type of \$\mu \$C package should I look for that will be nice and thin but still DIY solderable (the only one I know of is QFP but I'm not sure I could solder one of those)?
Lastly, are there any other common pitfalls when making flexible circuits? I can imagine people bending the PCB all over and accidentally touching traces etc.
EDIT I'm thinking about not making the circuit flexible, but storing components inside each little compartment of the watchband. Then I just need flex cables to go between the parts of the watchband for communication and power. Probably only need a few traces... this would lessen (almost eliminate) the stress on any solder joints and place it only on the material the communication traces are put on. Whether I decide to make that out of polyimide or just my thin FR4 is yet to be determined. Does this seem reasonable?
Thanks


texts: Why are MOSFETs used on the battery gauge lines?

texts:
This is from the iPhone 10, previous models didn’t have MOSFETs on the gauge lines so I’m wondering why they’re used now.

Is it so the phone can’t boot with just a voltage present from external supply without gauge lines, protection, or?

iPhone 10

iPhone 6s


texts: Drive very long WS2812B RGB strip (80 meters)

texts:
I have to drive an 80 meters long RGB strip. 100 LEDs/m. What's the best option?
I read Arduino hasn't enough RAM to drive them all so I was thinking about split the strip in slices and every slice be controlled by a Raspberry Pi. And having all the Raspberries internal clocks synced by an Ethernet cable.


texts:
Recently I've designed a PCB for the ESP8266EX-chip. With my amount of knowledge, I thought it would be smart to stitch vias into pads. To be specific, not only the ground pad of the chip, but also the small pin-pads (It's a QFN Chip).

After soldering everything using a reflow oven, the PCB wasn't working -> I couldn't upload anything to the chip. So I tried soldering the PCB in a reflow oven without any parts on the solder paste. This time I saw, that the vias suck up almost all solder off of the PCB pads. This could also be an effect because I don't  have any parts on the solder paste, but after searching the internet about my problem, it seems that my open vias are the problem.

I tried filling the vias with solder paste, and then putting solder paste on the pads, no success.

Is there a way to make this work? I received 35 boards from a sponsor (couldn't go lower), and it would be incovenient if I have to throw them away.

Soldering using a solder station is not an option, I tried. Looking for a solution on the internet was also not helpful.


texts: Relationship between input voltage and output voltage for an active filter

texts:
I'd like to know if I understood correctly the relationship between input voltage and output voltage for an active filter.
I study in French, so please understand if my glossary doesn't accord with English ones.
Say, [Av] is the coefficient of amplification(10^(Gain/20)). [Vi] is the input voltage and [Vo] is the output voltage.Φ is the phase shift between [Vi] and [Vo].
So,
Vo = Av * Vi(ω*t+Φ)
Isn't it right?


texts:
I just brought a LED board with 220V AC from here http://www.amazon.co.uk/Enjoydeal-Hydroponic-Plant-Light-Panel/dp/B00V5Y2FWG

I looked inside the board, and am curious about how so many LED are connected together, from my observation there are total 4 Parallel connections， for each parallel connections， there are 4* 14 = 56 led serial connected.
1. Is the circuit designed like that
2.and if one LED light is dead, then the whole parallel connection will be dead ?
3.is this circuit based on constant voltage or constant current？
4. the led light is about 9 w, so how much light lumen it could draw for these low power consumption led light?


texts: How to choose the right Metal Oxide Varistor (MOV)

texts:
I would like to protect the input of a transformer against high voltage surges but I don't understand how I have to proceed to choose the right MOV despite what I read so far about them.

Below is how I tried to do to pick the right component.

The circuit

simulate this circuit – Schematic created using CircuitLab

The needs

I have a 115V / 60Hz power supply and I supply a load with 24VDC through a 24V/52VA transformer and the rights filtering capacitors. The value shown are the nominal ones but my system can work up to 160V(RMS) at the transformer input.

I would like to protect my system against high voltage surges (1000V max). I have often used TVS diodes in my previous circuits but the environment was different (surges value, dc...). As far as I understood, MOV are well fitted to protect system against voltage surges either in a AC or DC powered system. In fact I often see them at the input of transformers, that's why in this specific circuit I would like to use a MOV (plus I will learn how to use them).

So I would like, even when a 1000V surge appears, the voltage at the input of the transformer doesn't exceed 160V. Is it something achievable with a MOV ? From what I have read, yes. From what I have understood so far, no. Maybe this is not the right component to use.

What I understood

Just to be sure I am not in the wrong, a varistor is a voltage dependant resistor. Its electrical resistance decreases with the applied voltage. It has two functional operation modes : when the applied voltage is below its clamping voltage, the MOV is non-conductive (normal operation). Above, it becomes conductive and the voltage across it is limited to a value just above the clamping voltage value (from what I have read here).

Why I am stuck

Well, just because I don't understand. To me, the clamping voltage is the voltage value from which the MOV will become conductive and thus, the voltage across it will not exceed this value (or just a little, like a zener diode in fact). But then I read this post. This designer states that his system could work with 520V(RMS) max at the input. But in his calculus, he chooses a MOV with a 1500V clamping voltage. Does it mean that if ever in his system a voltage surge of 1200V appears, this spike will not be suppressed and the system will see it ? Or do I have to think differently and take in count the Maximum Allowable Voltage that seems to be the reverse stand off voltage according to Peter Smith in this post ? In this case, does it mean that the MOV starts clamping at 550V (which a little bit more than the 520V wanted by the OP) and the voltage accross the MOV can raise up to 1500V ? In this case, how a MOV can pretend to protect an equipment ?

If I use my case and think the same way as the OP's other post : The nominal voltage at the input in 115V(RMS) but can go up to 160V(RMS). If I use this datasheet, I guess I have to find a MOV with a maximum allowable voltage close to 160V(RMS). But what about the Clamping voltage max ?

I am missing something, I am missing how a MOV can protect an equipment against voltage surges. Can you help me ?

Thanks !


texts:
I want to use in my project an isolated optocoupler like this one to switch an IGBT.
In the following schematic, taken from this Vishay application note there's a "floating supply" in Vcc1 as you can see:

I'd like to understand what it means. Should I connect the positive of my power supply in Vcc1 and let the common of the supply disconnected? Or the common should be connected to the emitter of the IGBT?

Another question: This same circuit would work well driving a SCR too? Like this:

Again, 12V and HV power supplies should have the same common?


texts:
Is there a very cheap way to measure several voltage differences of 0.1V to 10V (to ~1% accuracy at 10Hz, say), where each pair of measurement terminals may be tens of volts away from the ground of the circuit that needs the measurements?

As far as I can see, one either isolates each analogue signal before it reaches the ADC (using one isolating amplifier per channel - not cheap), or has one serial ADC per channel (not cheap -- I was hoping to multiplex a single ADC), each floated at the appropriate level, with optoisolation of the ADC output.

Are there any other strategies? Isolated DC/DC power supplies are themselves not enormously cheap (~£3/unit) so ideally I would want something that doesn't require a power supply floated at the level of each measurement input. Is this possible?


texts: Understanding voltage levels on 3.5 mm audio output

texts:
In the hope of using the standard 3.5mm audio output found in your average PC/smartphone to control (not power) a DC motor, I was measuring the voltage between GND and Tip and noticed the following:

When no audio is playing, there's a voltage of about 2 mV.
When I output a constant audio signal, the voltage rises initially to 0.5 V, but drops back to 2 mV after 2-3 seconds.

What purpose does this 2 mV bias voltage serve? Does audio output circuitry usually contain DC blocking capacitors, or is DC blocked via some other means?


texts: Why does smart card antenna follow a "snake" pattern when approaching the chip?

texts:
This image is from this post which shows MasterCard plastic card being dissolved in acetone to have the circuitry extracted for further analysis (TL;DR further analysis failed because of chip protective features). Wires are a bit off because acetone made them unbind from the plastic.

Note the area close to the chip - two wires approach the chip and each of them follows a "snake" pattern - down, then up, then down, then up again, that repeats at least four times.

What's the purpose of this "snake" pattern?


texts: What causes these peaks in the output voltage of a CMOS inverter?

texts:
The figure is taken from https://ece.uwaterloo.ca/~mhanis/ece637/lecture7.pdf
There is no significant inductive element in a CMOS inverter, so what is the cause of these peaks while switching?


texts:
I understand that having an capacitive load at the output of an op-amp can potentially make the circuit unstable. However, how can I go about calculating this?

For instance, I'm trying to design a constant current sink (upto 1A at least) using the parts I have lying around: LM324, IRF840 MOSFET etc. Here's the schematic:

The supply for the LM324 is +9V.

The IRF840 has an input capacitance of about 1225pF, which I assume is quite tough for an opamp to drive. My question is: how can I compute that I need a resistor at the output of the opamp to compensate for the capacitive load?

LM324 datasheet

IRF840 datasheet


texts: Powering laptop from 12V sources without inverter

texts:
This question has two parts:

1) How inefficient is it to boost 12V to 120V and then back to 12V as in using a traditional car power inverter to power a laptop (i.e. the 12V car battery power is boosted to 120V by a power inverter and then back to 12V by the laptop's power supply)?

2) Is there any way to power a laptop directly from a 12V car battery? This would be useful not only for use in a car, but also for a solar-powered home that runs on 12V batteries. If there is a significant gain in not going through the boost/buck cycle of power inverters, then it would seem wise to power laptops and other 12V devices directly from battery power. I realize that laptops have different power supply ratings and some require more than 12V, but it seems rather wasteful to boost everything to 120V before bringing it back down.


texts:
RJ45 to 8 pos board connector.
Board connector width: 12,4 mm
Pin pitch: 2 mm

Found inside a plastic card printer.
Somewhere to purchase cable?
Identification of the board connector?


texts:
I am using a SPF240D25R Solid State Relays - PCB Mount PCB SIP 240VAC, 25A load current and 4-15VDC trigger voltage. This is being triggered from a ULN2003A and used to drive a motor (pump).

On the same board I am driving a 5V coil relay which has 12VAC across its contacts with no load, this two is driven from another transistor with the same ULN2003A device.

When I fire the relay the SSR is firing. When I turn off the relay the SSR turns off. This ONLY happens when the load (motor) is connected to the SSR. For example, if I fire the relay and the measure the O/C load on the SSR it does not fire.

I cannot figure out the problem. I have a 100 ohm || 1uF capacitor snubber on the input to the SSR. I have a 1N4001 flywheel diode across the relay coil (even though the ULN2003 has them).

The main thing which is confusing is what does it not fire in error when no load is connected to it?

EDIT:

This is part of a large system and the schematics are over multiple pages. I have provided the various snippets below.

This is the SSR circuit. Please note that the SSR is a SPF240D25R (ignore the name on the schematics). Also note that the "pump relay" is not the offending relay. In fact when this relay is fired the same problem is NOT witnessed.

This is the lighting relay (recently added flywheel diode not shown)


texts:
We have this really strange problem with a regulator on a circuit we have.

Usually it outputs a good 3.3V , from an input source of 5V.
When we consume more current from the 5v source (not the REG output) , we get a voltage drop from 3.3V to 2.8V on the regulator output itself.

This happens only when we pass the 1.5A from the source itself.

The 5v source is capable of 4A , and it happens when we consume about 1.6A from the source. The source stay at 5V when the REG drops.

Please check the REG schematics here (c14, and c15 are in place) :

EDIT:

the regulator output is consuming less then 100mA.
I found out that the transformer source is indeed 4A output, but it says 0.68A maximum input - is that changes things ? how is that possible ? we replaced a few of them, non worked.


texts:
I was studying about 3-phase power supplies. After going through several searches, i found this formula of three phase bridge rectifier's output voltage:

Vdc = ( 3 x sqrt(2)/pi ) x Vrms

Vdc = 1.35 x Vrms

So, in the figure given below, should I take 200 Vac as a phase voltage or line voltage. Is it Rms or peak voltage. what should i put in the equation.


texts: How can a Switching diode act as a level shifter?

texts:
I am following a schematic about a one-way logic 3.3->2.8 level shifting circuit.

The hardware in question is a MCU output that drives 3.3V and the input of the  UART interface of a SIM800 GSM Module.
Im trying to simulate the circuit but can't figure out why it's supposed to work connected as it is.
The Hardware design document  of the input module doesnt specify what kind of input it is. And gives other circuits as recomendation:

The specific questions are
why do the circuits work like this?
How can I emulate the internal components to simulate and check the proper behaviour?

The design reference  comes from Adafruit's FONA  and Feather FONA boards.


texts: Tracking Sun with Solar Panel - Need Photosensor

texts:
I'm trying to build a structure onto which I can mount a solar panel where the structure will be able to turn and track the sun - to maximize solar energy input.

Can anyone suggest a photosensor that can be used to accomplish this? I looked online on some sites and they advertise photodetectors, however I'm not sure how good they are for this kind of an application (whether or not they'll just be dumb and happy with ambient light).


texts:
Hi,
I would be very grateful if anyone could shed some light on the below diagram as I'm trying to calculate the total resistance between A and B in this series parallel configuration.

10 and 20 are in parallel and 90, 70, and 80 are also in parallel but then I get confused with it as it then looks like two series circuits connected in parallel between A and B when you re-draw the diagram???

Thanks.


texts: Recharging NiMH cells after long period (18 months) of self discharge

texts:
I have seen information supplied with branded NiMH cells (e.g. Duracell) saying "do not leave cells for more than 6 months without recharging."

I have some AA size cells which were fully charged around 18 months to 2 years ago, but have since been left unused. During that time they have not been installed in any battery powered devices, and kept at normal household temperature and humidity levels. They have no visible damage.

Attempting to recharge them with my usual charger doesn't work - I assume their voltage is so low that the charger protection circuit is cutting in to protect the charger. If it's relevant, the charger is designed to fully charge either 2 or 4 cells, either AA or AAA size, in about 2 hours.

Is there any relatively simple (and safe!) way to recharge them to the point where a commercial charger will at least try to recharge them fully?

It wouldn't cost a huge amount of money just to replace them with new ones, but my natural inclination is "don't scrap stuff unless you really have to!"


texts: How do processors control their clock speed?

texts:
I recently came across an STM processor with 2 oscillators on the circuit - I suppose one for high-speed operation and the other for low power.

For something like a desktop processor where the clock speed can be changed to any desired frequency (within reason) - how does it physically do this?


texts:
I'm working on Lattice HDR-60 board which is pre loaded with a default program. When I try to load a program it disappears on restart. Recently I downloaded a design which downloaded successfully but didn't work. I restarted but now the INIT led is flickering and when I try to erase or download the default program it fails with the following error:

Error: Programming failed.
Failed to Open FTDI USB port. Make sure to select the right cable type.

Does anybody with some experience with lattice boards has any idea of where the probelm is coming from. I've searched through lattice website but no answer and as there are very few discussions on lattice products i thought i'll ask the question here and hope some kind soul will answer it. As I'm new to FPGA programming the problem is blocking me and I have no alternatives.


texts: Best possible specs for a MEMS mic in 2014?

texts:
I want to use the best MEMS mic that's on the market today (June 2014) in terms of audio quality.  Since I know that "shopping" questions are forbidden, I'll phrase it like this:

What are considered top-of-the-line specs for the best MEMS mics currently available, in terms of signal-to-noise ratio, sensitivity, and other key specs?  Is the state of the art better or worse for analog mics compared to digital mics?

Thank you!  Please let me know if you have a suggestion for how to phrase this question better instead of just downvoting.


texts: I can't understand why is 2Rpi in equation 375/376. It looks like the current ib1 goes through Rpi of first stage and through Rpi of second stage but it must go through first Rpi to ground and back to signal source. Why it's so?


texts: My amplifier produced a negative gain when it should be positive. Why?

texts:
Disclaimer: I am a Mechanical engineering student and I don't have a huge background in electrical engineering.

In on of my lab classes, we just dealt with the response of amplifiers to a variable DC voltage source. The lab consisted of DC power supply as the variable voltage source, an amplifier, amplifier power supply, and an oscilloscope. We varied the DC power supply from -12V to +12V in 2V increments and we had to record the output voltages and plot the final results. At 0V there was a offset of 2.54V caused by the amplifier being powered by the DC power supply.

After we plotted the results, the graph of input voltage vs output voltage looked as expected with lower saturation limits, then a linear increase in voltage and high saturation limits. Our results showed an amplification factor (the slope of the linear region) of less than 1, which caused the gain of the amplifier to be negative. My TA said the setup looked fine and could not explain any reasons why we got a negative gain.

Does anyone have any reason as to why the amplifier would produce a negative gain, thus defeating the purpose of the amplifier?


texts:
I'm currently working on a simple driver for a DC motor, only one rotating direction with PWM control. For information, PWM frequency is 1kHz.

I have some problems with overvoltage at the terminals of MOSFET. Those overvoltages are very short and I can not attenuate them. I tried with zener diodes in parallel to power supply but they do not seem fast enough.

This voltage measurement is taken between the drain and the source of the MOSFET.

Is there a solution to smooth this voltage spikes? Or is it something acceptable? I used this circuit with a labo power supply.

Thank you in advance for helping me to improve this circuit.
Regards.

Edit 1:

I did some tests in order to increase the turn-off time. This is the new diagram, I changed the value of the resistor R2 and I found that a bigger resistance decreased the overvoltage spikes! I need to continue to search but that may be a solution.


texts: How do you figure out the decoder inputs for a memory expansion?

texts:
How do you know what the two inputs will be for this 2-to-4 decoder? Also, what changes would be made to the circuit if the 2 data lines are not the same?
The original problem:

I drew the circuit, but I'm confused about the two things mentioned prior.


texts: Calculating the power lost per foot from “\$I^2R\$ losses"

texts:
I am currently studying The Art of Electronics, third edition, by Horowitz and Hill. Exercise 1.6 says the following:

C. Power in resistors
The power dissipated by a resistor (or any other device) is \$P = IV\$. Using Ohm’s law, you can get the equivalent forms \$P = I^2 R\$ and \$P = V^2 / R\$.
Exercise 1.6. Optional exercise: New York City requires about  \$10^{10}\$ watts of electrical power, at 115 volts (this is plausible:  10 million people averaging 1 kilowatt each). A heavy power cable might be an inch in diameter. Let’s calculate what will happen  if we try to supply the power through a cable 1 foot in diameter  made of pure copper. Its resistance is \$0.05 \ \mu \Omega\$ (\$5 \times 10^{−8}\$ ohms)  per foot. Calculate (a) the power lost per foot from “\$I^2R\$ losses," ...

So we have that \$P = \dfrac{I^2}{5 \times 10^{-8} \ \Omega} \$, which means that we need to find the current \$ I \$. I sought to use Ohm's law: \$I = \dfrac{115 \ \text{V}}{5 \times 10^{-8} \ \Omega} = 2.3 \times 10^{9}\$. Have I done this correctly? If not, then why is this incorrect, and what is the correct way to do this?


texts: How to design a soft switch controlled by USB connector?

texts:
I have to design a powerbank. I want the DC-DC boost converter (Texas Instruments TPS61090) ENable PIN set to 1 when the user plugs in the USB male connector into the female one. When the user disconnects the cable, the IC shuts down. I thought this design in order to remove the need of a switch that controls the power.

Is a µcontroller needed for this application?
If so, can you suggest one that has µpower needs?


texts:
I created a simple power supply as shown below that results in an unregulated 50VDC which is what I desire. The transformer is rated for 1000VA. It works ... but only if you're lucky enough to turn it on at the right time of the AC cycle to not pop the breaker. Clearly I need to limit the inrush current on those capacitors.

I was looking at putting an NTC Termistor in series, probably between the transformer secondary and the bridge rectifier. Specifically SL22 5R012 which is 5 ohms at room temperature, can do 12A at steady state, and can survive 100J.

The problem I foresee however is the load connected to this supply is not constant. The load is DC solenoids that could not be activated for a significant amount of time (minutes to hours). That would mean the NTC would likely cool down correct? I don't know if the capacitors would be enough for the NTC to reheat when demand is needed. There would never be a constant load on the supply, aside from the bleeder resistors which is pretty low.

I've heard of having a relay or MOSFET to bypass an NTC or regular resistor after X seconds, but unsure how to implement it with only the 50V available.

simulate this circuit – Schematic created using CircuitLab


texts: At the slack bus, there is a generator that can change his output instantly. I was wondering if exists in the grid this generator. We use it to study power flow problems but I don't think that there is a generator in the grid (that of the slack) which is able to change his output instantly. Can you give a physical representation of the slack bus?


texts: TL431 LDO series pass transister heating up

texts: I designed a low drop out 5v voltage regulator from 24v input. Works fine. But the series pass transistor heating up more than 100 degree Celsius (with heat sink). Is it normal? Or how to reduce heat? Consumption is 150 mA, running a dsPIC30F2010. Explanation or correction or suggestion most appreciated. Resources I am stuck with TL431/MJE13003, cuz other ready made LDO products not available in the local market. Circuit included.


texts: Current amplifier with Mosfet and Op-Amp: Output resistance

texts:
In the following circuit, why is \$R_o\$ given by:

\$R_o=(R_1//R_2)+r_{o2}+g_m .r_{o2}.(R_1//R_2)\$ ?

I dont understand the \$g_m .r_{o2}.(R_1//R_2)\$ parcel


texts: Watts - I think I'm getting free energy from a circuit?

texts:
Imagine I have a 10V battery with a capacity of 1Ahrs connected to a 100 Ohm resistor.

I'll get 0.1A (V/R) at a power of 1W (current x voltage) for a total of 10hrs. As a watt is defined as J/s my battery produces 3,600J (1x60x60) in total.

Now, imagine I get a second, identical battery and connect it in series to the first one. I will effectively have a battery of 20V with a capacity of 2Ahrs, all connected to the same 100 Ohm resistor.

I'll get 0.2A at a power of 4W (current x voltage) for a total of 10hrs. This will generate 14,400J (4x60x60).

So, from doubling my energy source I have quadrupled the energy output!

I've obviously made an error somewhere either in my calculations or conceptual understanding, and I would be most grateful to anyone who could set me right.

Thanks!


texts: What's the difference between µF and µFD?

texts:
A datasheet is referencing "CAP SMD0603 CERM 1.0UFD 16V 10% X7R ROHS" which is calling for a UFD. But I have a uF cap C1608X7R1C105K080AC which is "CAP CER 1UF 16V X7R 0603". Should that work fine? Is µF and µFD the same?

https://www.digikey.com/product-detail/en/tdk-corporation/C1608X7R1C105K080AC/445-1604-1-ND/634399


texts: Can I increase the power rating of a film resistor if I increase the cooling?

texts:
I am trying to apply 1 kW of heat to an area of 10x10 mm and I am considering using a panel mounted film resistor.

One that meets my power requirements doesn't exist so I am wondering if I can go above the normal power rating if I sufficiently cool the resistor.

Could I use a lower powered one as long as the heat was adequately removed?

(I should say the point of this is I am developing a heat sink for high powered electronics and the temperature of the resistor wouldn't go above the normal recommended temperature)


texts: Suggestion for a power on/off system circuits

texts:
In my last projects, I've used a usefull circuit that I found on the web for power on/off my electronic systems:

It works very well: I connect the output to the enable pin of the main voltage regulator so to turn on the system you have to press the buton and to turn off hold the button for abount 3/4 seconds.
Now I want that the microcontroller of the system shuts down properly some peripherals before the whole turning off.

Do you have any suggestion to modify this circuit or another one for this scope?


texts: Table jitter on 40 ft planer mill at certain low feedrates with new 40 hp 3-phase motor and 50 hp ABB drive

texts:
The display on the drive shows 26 amps with little variation at all speeds.

At 176.14 RPM it shows -9.2% motor torque, 25.63 amps.
At 977 RPM it shows 26.04 amps and 2.4% torque.

The motor spec shows a max of 178 ft-lbs torque, 460 VAC at 1182 RPM, 53.5 amps, 6 poles. The table jitters at speeds less than 300 RPM.
I am trying to determine if this is a problem with the parameter torque settings in the ABB drive or some kind of mechanical problem.
Additional informetion:
ABB ACS880-11-065A-5 37KW 50HP DRIVE, Motor is a Marathon Blue Max model WD 364THFS8391FU W 40HP 230/460 VAC 3 PHASE. Had other techs set it up but are still mystified as to the jitter. This planer has a combo chain drive thru a two speed transmission setup where it uses this drive and can be disengaged to use a 75hp dc direct drive for high speed planing. Has two 20' 10,000lbs tables bolted together. Runs fine with one table but attach the other and there is jitter, so torque, inertia etc could be a factor


texts:
In the simulation, the input is made from using two complementary signals.

RI and RF of the difference amp are controlled via voltage controlled resistors; they are ideal resistors and perfectly matched for each case of 100, 500, and 1kOhm.

Here are the results.

Why does the output signal's THD and Vos get worse when RI and RF resistance decrease?

I am not sure how to explain why changing the input & feedback resistance of a difference amp affected the THD and offset since the resistances are perfectly matched.


texts: Does Tesla coil use near field or far field?

texts:
According to Wikipedia a Tesla coil

  transfers energy (via loose coupling) from one oscillating resonant circuit (the primary) to the other (the secondary) over a number of RF cycles.

which I don't quite get. RF is likely opposed to near field and the near field spawns about 1 wavelength from the source and that's 30 meters even at 10MHz, so looks like it's a plain old near field transformer, just with an air core and with coils separated rather far from each other.

So does Tesla coild use near or far field for transmitting energy?


texts: Equal and opposite Voltages applied across 2 resistors of equal Value

texts:
Take a look at this picture here:

Please note that the two resistors are equal in size.

Here it says that the voltage at Point TP3 is zero volts. I do not understand how that is.
The creator of this image says in a video that this is because the Voltage at Point TP2 (-6V) and TP8 (+6V) cancel each other out.

Is he right? Do they cancel each other out?

Here is the link to the youtube video: watch?v=tsrAP8EgcbQ

****EDIT****

So here is my scribble:

My understanding is that the Voltage "AB" (the voltage above R2) will be feed to the amplifier. In the first picture i posted that would be the voltage "TP3TP8".

So the voltage between the point A and the point B will be 0 volts?

Edit

Thanks for the help. Something must be wrong with my understanding of voltages. I have now something to work with.

Again thank you!


texts: Precision Current Measurement Using Arduino

texts:
We are designing a circuit to measure the current consumed by a Ultra-low power communication module. The requirement is below:

Min current = 0.2mA
Max current = 100mA
Resolution = 0.005mA (5uA)

We do not need to measure dynamic current, just want to measure average current at a specified working condition such as Active, Sleep, Shutdown
we will use a sensing resistor in series to the load.
I have some questions, please provide clarifications.

The sense resistor value selected is 500 mOhm. According to my understanding to get 5 uA resolution ADC’s 1 LSB must be less than or equal to 2.5 uV (RsenseCurrent step, ie (500mohm5uA). Please correct me if I am wrong.
Do I need to use a pre-amplifier after current sense resistor? Imagine I am using an ADC with 24bit resolution and 5V reference then my 1LSB will be 0.3uV, less than the required resolution. Is it possible to connect a buffer after Rsense and connect its output directly to ADC input?

May I know can I use Arduino for this application


texts:
I would like to know how much power does a flash memory chip consume, and whether it is viable for use when the device is switched off since I will require R/W access to the chip when switched off. Device in question is a cell phone, about 2000 mAh.

Is there any other power-saving alternative available other than flash memory? I want the chip to eat only as much power as a cell phone's clock requires, or lesser, since it has to work when switched off as well.


texts: Does the 969973-3 SMD receptacle need mounting holes?

texts:
I am designing a board that uses a 969973-3 wire-to-board receptacle. In its drawing there are specified six 1.2 mm (mounting?) holes.

Does anybody know what are they used for?

I've seen pictures and 3D models for this connector and have not observed any body plastic parts that may be present on its bottom side, that may fit in those holes.


texts: How to view the implementation on Vivado

texts:
im very new to FPGA programming.
Is there a way to view the implementation of a digital logic design on the selected hardware device?
For example exactly how an arithmetic operation is implemented using look up tables and arithmetic circuits on the FPGA?


texts: Why are microcontroller WiFi modules expensive compared to USB WiFi adapters?

texts:
I recently bought a WiFi adapter for my Raspberry Pi for about 8 USD. At the same time, WiFi modules for Arduino and similar microcontroller boards cost several times as much.

What is fundamentally different between a USB WiFi module and one sold as a peripheral to micocontrollers? Is it just the economics of high-volume/low-cost, or something fundamentally different in the hardware?

(I've heard about the TI CC3000 WiFi chip that is supposed to be under $10, but I haven't found any place that sells just the chip.)


texts: Mini PC received higher voltage (19V instead of 12v) what hap

texts:
It was dark behind my desk and I've plugged in the wrong cable 19 V, 3amp instead of the dedicated 12 V, 3amp. The 19V adapter was from the monitor, and after I accidentally plugged it into my mini PC, it sparked and didn't turn on again after I've plugged the correct 12V adapter.
Further, when I now plug in the 12V adapter, the LED on the adapter goes away.
Can someone explain to me what happened? I'm not savvy in this area, but need to find an Answer to find peace with myself. And is this damage repairable or are the capactiors fried and more? I didn't smell much, just the typical Nintendo smell.


texts:
I am looking at buying a DC motor with reasonably high torque characteristics that is essentially going to be for the joint of something like a robotic arm.

I came across several worm drive DC motors that fit the requirements, however I am a bit confused by some terminology. They give the stall torque, stall current but also a hold torque which is 80% of rated load. For a motor that's holding a weight on an arm at some angle, wouldn't the stall torque be the same as the hold torque? My understanding was that stall torque is produced at near zero rotational speed, which is the case for a static system.

Secondly for a worm drive motor, I didn't think that kind of gearbox allowed rotation from the load to the motor by way of the worm drive design. Wouldn't the hold torque of a worm drive motor be the breaking point of the gearbox?

Motor in question: https://www.motiondynamics.com.au/worm-drive-motor-12v-50w-45-65-rpm-5-29nm-torque.html


texts: Excited diode allow flow opposite direction, possible?

texts:
I searched for some information regarding LED's and found out that they can only go one way because of the two metals inside of the LED have 2+/- electrons making it easy to go one way but difficult to go the other way. This got me thinking about valves. When valves are open you can also squeeze to the other side! So I was wondering if it is possible to excite an LED(through a laser beam or something similar) to allow current to flow to the opposite "allowed" direction.

Setup:

**+** = **+**
**|<|**= LED
**-** = **-**
--- = wire
LOAD=LOAD

I'm so clever. I know.

Laser beam shooting photons at LED

**+** --- **|<|** --- LOAD --- **-**

I tried googling this kind of information but it appears that no one has really thought about it. Or I'm a bad googler.


texts: one device with two power supplies connected different voltage outlets

texts:
DISCLAIMER: I know little to nothing about electronics. :-(

We are in the US and the bulk of the Data Center is running 110-120v devices and outlets.
Our Data Center's large central UPS system is being worked on this weekend.  We have been told that while it's unlikely there will be any power issues, if commercial power goes while the UPS is down, devices will go down.

One particular older device has my manager worried.  It has dual power supplies that can "automatically" switch between 120v and 240v.  Both are presently on 120v.

We have a portable UPS but it is for 240v.  What my manager wants me to do is to move the device from its 120v source to the 240v source WHILE IT IS STILL POWERED ON -- meaning that at one point, one power supply will have theoretically switched to 240v while the other is still running 120v.

Again, I know little or nothing - but the very idea made alarm bells go off.  However, I couldn't tell him with any certainty that this would end badly.

I understand that it may depend on the hardware, manufacturer, the zodiac sign it was built under or whatever - but what is the general opinion here on what the outcome might be?

Thanks for any response, and I am sorry for my ignorance.


texts: How to protect power supplies and pulser in DC bias + high voltage pulser combined circuit?

texts:
I am building an electric circuit in which a DC bias power supply and a high voltage pulser are mixed. I need to save each one from the other with proper safety measures. I have researched several papers to grasp examples of circuits being used, however, as being not familiar with general high voltage circuits, I am struggling with what would be the best way for me, and need helps.
First, let me introduce what I know. The followings are the general schematics for the high voltage pulser(commercial equipment) which generates several kV in a few nanoseconds when triggered, either positive/negative polarity pulse.

simulate this circuit – Schematic created using CircuitLab
Understanding the above pulser circuits was ok to me. However, when it was together with a DC bias component, I start struggling to understand.
The following is an application example I found from a paper, 1 D. F. Opaits, A. V. Likhanskii, G. Neretti, S. Zaidi, M. N. Shneider, R. B. Miles, and S. O. MacHeret, J. Appl. Phys. 104, (2008).
Thankfully, it explained each role of the circuit components, as

a 470 pF capacitor in series with the actuator to shield the pulser from the bias voltage.
the 220 kOhm resistors did not let the pulse go to the power supply.
The 10 MOhm resistor in parallel with the actuator for safety reasons. It discharged the high-voltage electrode after experiments.
a noninductive 250 Ohm resistor in parallel with the actuator to minimize the pulse reflection.

So, I think the safety components to protect the pulser and the DC supply from each other are; the 470 pF capacitor to block the DC to pulser, and the 220 k resistors to block the pulses to the DC. So far, so good.
--
Another example I found was in the following configuration. It doesn't give an explanation for the components and their values.

simulate this circuit
I wonder whether this circuit has a proper safety components. One big difference to the previous one is that in this appliction, the DC circuit has a current(~5 A) flowing. So, I somehow think, this example should have different configuration (probably because it cannot use the 220k Ohm to protect the DC supply from the HV pulse?).
My questions are

Does this circuit have a proper safety component for the DC bias and the pulser?
What would be the role of the inductor(L1) and the resistor(R1), and how can I decide the values for them?

And, finally, my application is similar to the second one but could have even a high current ~50 A in DC bias (20 V) circuit, and I have a positive HV pulser (the above examples are negative HV pulsers). Referring to the examples (if the R and L in the second example does a certain safety work), my design is as follows, but I wonder

Whether it is a good or OK design, and how to improve,
What values or part components should I use for C1, D1, R1, L1. or what I should consider and pay attention on deciding.

simulate this circuit
Thank you for reading my long question.
It would be very grateful if you could share your idea, comments, suggestions.


texts:
So, I purchased a NJM2360D boost converter from Mouser. Using two 6V batteries in series to create a 12V supply, I'm trying to obtain a 40V output.

The "typical application" circuit from the datasheet is shown below:

Can you guys offer any insight into the design of such a circuit?

How are the capacitor sizes chosen?
What size inductor will I need?
What type of inductor will I need? (when I try to find a simple "inductor", there are many options)
What does the voltage at pin 5 do? How do I select the resistors for the voltage division?

Any help would be greatly appreciated!


texts: Emulate many-pole, dual throw switch with transistors

texts:
How can I use transistors and other discrete components to make a circuit that functions like a DPDT (double pole double throw) switch, and can be extended for any number of poles required? For examples assume an input voltage of 12VDC, required current of 200mA per pole and use general transistors and standard values where possible.

Note: it must act as double throw; i.e. power goes to two separate outputs, not one output or floating. Please include some form of schematic.


texts: Unused MCU pins, better to tie to GND or use software to prevent floating?

texts:
Possible Duplicate:
  General “rule of thumb” for unused IC pins

I read thru couple of questions & answers in here regarding the proper usage of unused MCU pins and all of them discussed about setting them either inputs with internall pull up/down or as output from the embedded software.

However, nobody mentioned the obvious: wiring the unused pin to GND or VCC. Is there any reason why one should not do that and use the software methods instead?


texts: Problems triggering opto-isolator with logic gate

texts:
I should start by saying I'm fairly new to electronics so bare with me as I struggle with some basic issues.

What I'm trying to do is trigger a 5V opto-isolator from the output of a series of logic gates, with the last one being an SN74LS08 AND gate. When I try to do this however, the opto-isolator doesn't seem to be triggering regardless of the AND gate being high or low. I've attached their datasheets and a schematic

AND gate: https://www.digikey.ca/product-detail/en/texas-instruments/SN74LS08N/296-1633-5-ND/277279

Opto-isolator: https://www.digikey.ca/product-detail/en/vishay-semiconductor-opto-division/VO4661/VO4661-ND/1738670

simulate this circuit – Schematic created using CircuitLab

When I hook the opto-isolator directly up to a 5 V supply, it works fine. This leads me to believe it's because the AND gate cannot supply enough current when logic high.

High level output current: -400 uA.
Low level output current: 8 mA

Yet, the opto-isolator desires a high level current of 5-15 mA and low level current of 0-250 uA.

I don't know how on earth I'm supposed to satisfy both of these current ratings, or maybe it's something else entirely. I received this design from an undergraduate thesis that supposedly said this worked.

Any help is greatly appreciated! I will try to respond quickly if more info is requested.


texts:
I've been using a halogen oven with a home made controller as a simple reflow oven. The controller uses a thermocouple to measure and control the temperature profile.

The problem I have is that I'm getting inconsistent results depending on the component. As a test I made a simple board with 8 resisters and 8 LEDS. In this case I've put a little solder on the pad using a soldering iron, positioned the components on the pads and then re-heated in the oven. I cleaned the board with liquid flux before applying the solder and again after applying solder (In one case - I had similar results when I didn't do this second clean)

The resistors have all come out fine. They are positioned well and the solder looks good. The LEDS however all come out terrible. They all just about have proper electrical contact so the board "works" but they are very poor indeed.

The components are all about the same size and have similar contacts. There was no difference in the preparation. The LEDS are very slightly thicker I suppose. They are within 1cm on the board and I don't believe would have significantly different temperatures.

I'm wondering if anyone has any explanation or suggestions about how to improve? Maybe I need to increase the temperature? Or hold the temperature a little longer?


texts: Ethernet Trace Layout with PoE & Integrated Magnetics

texts:
I'm a hobbiest & I've put together a simple PoE board using a LinkIt Smart Duo, the AG9050-2BR and a Bel Fuse 0813-1X1T-57-F. The power circuit works but the Ethernet signal wont work.

The LinkIt has a PHY ethernet output and can be hooked up via traces to a RJ45 Jack. I have tested the LinkIt on its breakout that the Ethernet circuit is working.

Schematic:

The AG9050 is not pictured here.

PCB Layout:

Ethernet Traces are these four just here ^^^^

I've read through this website on tips regarding Ethernet traces. I wish I had done my research prior to getting the board cut. I'd like to know if it is just a trace length/coupling issue or if there are other issues at play.

What do I need to do to ensure the integrity of the ethernet signals on a PCB?


texts: How do you protect a Li-ion / Li-polymer battery from over-dishcharge?

texts:
I'm setting up a power regulation system for a lithium polymer battery, but I'm aware that my LDO will continue to draw current from the battery even after it's fallen below an acceptable level of charge.

Is there anything I can do to shutdown my LDO after a certain input voltage?

My understanding is that it will continue to draw current, but output a lower voltage until it cuts out around 2.5V, which is much lower than the battery voltage should go.

I'm using a MCP73831 Battery management IC with the LD3985M33R LDO.


texts:
I have a DPST emergency push switch. I want to use this switch to power and disconnect power for a device. But additionally I would like to have leds as indicators.

This is a schematic I drew for what I'm thinking but w/o leds. The pins at the end are the the vcc/gnd pin for the device being powered(switch is actually 1NC 1NO):

Is this the best way to approach this problem? What is the easiest way to include leds into this design? Should I provide an external power for the led instead?


texts: Diagram validatation for two motors connected with On-Off-On Switch

texts:
I want to connect two motors on an On-Off-On switch. On position 1, I want motor 1 to me active, on position 2, I want motor 1 and 2 active.

Here is the diagram I was thinking of implementing

My second question, if this work, what kind of Diode should I be buying? on the circuit lab I've just used the basic diodes.

My motors are 12V 25W water pumps


texts: Calculation of varistor parameters for AC line protection

texts:
There is a task to choose a varistor to protect the AC circuit, controlling several coils of magnetic starters.

Characteristics:

Mains voltage 230-240V AC
Frequency: 50Hz
Starting current of coils of magnetic starters: 3A max

For these purposes, I want to use the LA series varistors from LittleFuse.

Model: V275LA20AP

Characteristircs:

Vm (AC): 275V
Vm (DC): 369V
Varistor voltage: 387V (min) - 473V (max)
Clamping voltage: 710V

Questions:

Vm (AC) - Is this a normal mains voltage?
Do I need to find the peak voltage amplitude to select Vm (AC)?

For example:

Mains voltage: 230V

I must multiply this value by √2 and add 10% margin.
230 * 1.41 = 324.3V + 10% = 347.3V


texts: Turn on and let LED stay on if value is over threshold in main while-loop

texts:
I'm totally stuck with this rather trivial (?) problem, i've got this pseudo code that i will convert to C (i'm programming a ATmega8 MCU):

Include libraries
Threshold = 40 //Celsius

While true
    Temp = Read_temp_from_sensor()

    If Temp > Threshold
         Turn on LED
    Else
         Turn off LED

Is there a way to make the LED stay on for the duration of the While-loop but only as long as the temperature read from the sensor is higher than the threshold value?

I'm guessing that i don't want to evaluate the values in the If/Else block at every cycle, am i on the right track here?


texts: Powering multiple WS2812B strips from different sources, are all grounds connected?

texts:
I'm looking to confirm if I need to connect the ground of 2 LED strips which have different power sources.

Adafruit says

  The key is to have all of the ground pins among the strips connected in common, but the +5V from each power supply should be connected only to one length of NeoPixels — those should not all be joined.

A response to the question When I connect chain of LED strips to power from both ends, do I need to make the power line disconnect in the middle? says:

  For a 6m long strip, you will need to power from both ends. It is recommended that you use one power supply (10A should do depending on your LED density) and allow the ground wire to run through the entire length. The power lines in the led strips themselves are not thick enough to carry 10A over 5M without enough loss to cause dimming or color change.

However, Branden's answer in the Powering a WS2812B strip question makes it sound like I should contain the ground to each strip. (Unless I am reading his answer wrong):

  So as a suggestion, make sure you power each 1m strip individually instead of tying them all together and having every LED in parallel (and the strips themselves in series). What I mean by this is, tie the +V of all the strips together to one power wire, and then tie all the grounds together. Don't just line up all the strips in a single line, end to end, and solder them. Just the data line should be like this.

I may have confused myself into a corner so I am just looking for a confirmation that the ground needs to be shared across the whole project/all LEDs and all power sources.

Edit: Title change for clarity


texts: As a sort of weird side project, I'd like to make an oven timer that has selectable food stuffs and associated timing information. Now while this device would be simple to make I would like to stick it on the oven which means it would have to deal with some significant but not ridiculous temperatures (gas oven, metal structure). Has anyone has any experience heat proofing things like HD44780 LCDs, AVRs and other delicate components or do I have to go and get hold of those military grade parts?


texts: Single FET Bus Switch schematic in EAGLE

texts:
I've added a SN74CBT1G384DBV into my schematic in Eagle (which I want to use to enable/disable a logic signal line). Once placed into the schematic there only appear to be connection points for VCC and GND and nothing for the A/B and OE pins.

What am I missing? Looking at the board diagram it is complete with all connections present.

Here is the schematic icon as shown in Eagle (as you can see the board package is complete).

Background to problem

I'm guilty here of asking how to do 'X' in a very specific way even though my real problem is finding out how to do 'Y'. If there is a better solution to the problem I'm trying to solve then I'm interested to hear it. My setup looks something like this:

Master talking I2C ---> AtTiny1634 with switching logic ---> Slave listening to I2C

I need for the AtTiny1634 module to be able to enable/disable I2C communication (I'm assuming just enabling/disabling the SDA line is enough, no problem to leave the clock signal passing through) to the slave device.


texts:
I need to create 3 circles in Layer 20 in eagle, of witch one should be in the center of my board and have a diameter of 10 mm and the other 2 should have  a diameter of 4,8 mm. The two circles should be symmetrical spaced from the circle in the middle (the one that is 10 mm) and the distance from center of either one of the circles to the one in the center should be 40 mm, also all the centers of the circles should be on (x= z, y=0).

Thanks!
Mihai


texts: I'm trying to understand what the following symbol is for. It's found in this schematic.


texts: How does a cross-over BJT's damp the distortion with help of negative resistive feedback in an analog audio amplifier?

texts:
I found an expression that explains how a circuit with op-amp responses to a distortion:

$$y = \frac{1}{\beta}x + \frac{\delta}{A\beta} $$

Now consider the circuit:

Here, the green, blue and red waves represent input, op-amp out put voltage and out put voltage respectively.

I know, the cross-over transistors introduce distortion, equivalent to the \$\delta\$ in my expression. I expect to get as the maximum voltage of about 5.7 volts at the out put (node N1), but i observe the maximum voltage of exactly 5 volts. So no distortion at the output at all. And i can't explain it. I mean the voltage at N1 is equivalent to voltage y at my initial circuit, and y includes the distortion, however that's not the case at the second circuit.


texts:
I need to obtain 5V stable week power supply from a 230VAC power line. I need this as cheap and as small as possible. Fortunately I don't need galvanic isolation and required current is as low as 1-2 mA.

There are no available linear regulators which I could connect directly to rectified mains (the most voltage resistant ICs has up to 450 volts when I need at least 616 volts: 400 * 1,41 + 10% - the device should survive phase to phase connection).

Now I came to this solution:

This schematic works very will.

However I will need conventional linear regulator anyway to provide stable Vcc (output of the schematic above is depends on consumed current and has 100Hz ripples).

If I'd able to put an external switch to regulator I could find the switch with necessary voltage strength and I'd get needed stability.

Is there any solution?


texts:
I'm using a P-Channel (DMP1045UQ) and an N-Channel (BSS138K) FET to pull a 12v Logic line (12v @ 5mA) high (from GND) from a Logic Level(3.3v) MCU I/O pin.

Here is the schematic, where VIN = 12v, MCU_TEL_ON = MCU Pin and TEL_ON_IO is the line that is being pulled high.

My questions are:

Have I done anything egregious here?
Is R17 even necessary? Seems to work fine with it in the circuit, though.

Additionally, the circuit does not need to switch quickly -- TEL_ON_IO is meant to be kept high for long periods of time.


texts:
I have two options for input filter having ferrite bead and reverse polarity protection diode as shown below

simulate this circuit – Schematic created using CircuitLab

The input supply is from 9 - 16 VDC. This is meant to protect the solution from EM immunity requirements as per ISO 7637.

I am also unsure about the values of the capacitor to be used in option 2.

The input current is around 1.5A.

Which of the above two options fits the best?

Also, how should I place these components on the PCB.


texts:
In LTspice can I convert the units of an FFT which by default seem to be shown in dBV to dBµV?

Cause of reason:
The reason for this is that I've a modeled a LISN in LTspice where I want to simulate what is seen on the output, hence in real life what the Spectrum analyzer would see.

My first approach was to use FFT of waveform, then look at it in Linear mode so I could read out the voltage at one specific emission top then apply 20*log10(V)+120 then i got 86.6 dBµV, when applying 20*log10(Trace in LTspice)+120 i got 87.2 dBµV at the same top.

It can also be seen that I get a lot more noise where there shouldn't be any when applying LTspice math.

My LISN where MP1 and MP2 is the measuring points


texts:
How do high power LEDs with forward current of 350mA compare to bright 5mm LEDs with forward current of 20mA?
If forward voltage is the same (same color) does that mean light output of 17.5 of 5mm LEDs equal 1 power LED? Which type is more efficient?

And one more question, in datasheets why measure of light output of power LEDs are given in lumens (luminous flux) but standard 5mm LEDs are given in mcd (luminous intensity)?


texts: 24V LED Strip Circuit - Switch, Breaker & Wiring Size Requirement

texts:
I am running a long LED strip (24V, 21 meter, 0.6A per meter, so technically 13A).

The 24V PSU supplying power to the strips is to be connected to a switch that is rated 240V, 10A & 2400W.

Questions:

1) Will that be a problem? 24V x 13A is technically 312 watts which is well within the rated watt. But the switch says 10A max.

Having said that, i understand that 10A calculation is based on the 240V voltage but i still want to be sure that this will not cause a problem.

2) The LED strips are in the same circuit as the LED ceiling lights which are also connected to the same switch.

It's usually the practice here to use 10A MCB for lighting circuit (1.5mm2 wire) but the 13A from the LED strips is already over this limit.

So do i separate the circuit for the LED ceiling lights from the LED strips circuit in order to use different breakers?

3) Does the max current for a wire remain the same for low voltage circuit? For instance, 1.5mm2 wire's max current for 240V is roughly 10-13A. Does that change when it is running 24V circuit instead?

For example, 10A x 240V = 2400W / 24V = 100A which means 1.5mm2 can safely power the led strip circuit that requires 13A?

I came into the above conclusion because 1.5mm2 = AWG#16 which has roughly 21A max current. 10A x 240V = 2400W / 110V = 21.8A.

Thanks in advance!


texts: LC Oscillator in Capacitive Divider Mode

texts:
Hi,

In oscillator circuit, I have faced such LC topologies where between two capacitors, the wire is grounded as shown above.

What I don't understand is why I should ground it. Clearly at the ground point, the current can take either path A or path B (as in diagram). Now at resonance both path offers zero resistance/reactance. Though path B offers zero resistance in all cases. Assuming my inductor is ideal, why should I allow it to be grounded because if current leaks through path B, it means I am having non zero reactance around the circuit. Lets assume the input impedance of the top amplifier with a gain of $$a$$ is very large.

I though on it a lot, but still I don't  have any convincing answer for this. Can someone please drop some clues here.


texts: Converting a variable voltage to s stepped voltage

texts:
I want to design a circuit that takes a variable voltage (0 to 5v) and outputs a stepped voltage — 0, 1, 2, 3 and 4 volts. So that the output voltage snaps to the closest whole number. It doesn't have to snap precisely — just provide a stepped range.

Thanks in advance!

James


texts: Do AM radio broadcasters pick frequencies that are picked up as interference on purpose?

texts:
This is not meant to be a political question, rather a historical one, USA based.
Every place I have lived, if I have an amplifier with a long enough input wire, I will start picking up AM radio if I don't have a signal going through. Now I've lived in 4 places in 4 different states in the US and in every single state, 99% of the time the radio station you pick up is a Christian Broadcast owned by the Salem Media Group in the 530-570kHZ range.
Did Salem Media Group do this on purpose? Did they want people to accidently pick up their broadcasts, or is it just a coincidence that a single company seems to own all these bands?


texts: How to get from theory to a working Industry Control System?

texts:
EE Student here who recently finished the classical control theory class. I was wondering the process of how the industry or anyone goes from drawing block diagrams to actually implementing in hardware.
For example, I'm trying to design a system that keeps a battery from reaching a threshold temperature without having the battery reduce its power output. I'm having trouble visualizing how I will go from a PID controller in theory to the actual hardware system.


texts:
I was looking at the specifications for DALI drivers and apparently the nominal current usage is 2mA/driver for the dimming signal. Does anyone know what the minimum current is?

I have a 12V/1mA supply and am wondering if this would work.

Thanks!


texts: How to increase current drive of Charlieplexed LED array?

texts:
I am driving 15 LED's with a Charlieplexed circuit (using an Atmel ATTiny13). I've reached the current limit per I/O pin of 40mA and would like to drive the LED's higher (they're rated at 50mA).

Is there a way to incorporate transistors into a Charlieplexed array, or do I need to grab a micro with more pins and convert to a tranditional Multiplex?


texts: Ethernet NIC architecture: Function of loopback circuit

texts:
(source: flylib.com)
I want to make sure my understanding of the function/the needs of loopback to detect collision is correct.

There is frame to transmit from Ethernet controller.
TX transmits to wire, loopback and collision detector.
RX receives from wire and loopback.
RX transmits to collision detector and Ethernet controller.
Collision detector compares whether the voltage it receives from TX and RX is same or not.

Is this correct?


texts: High thermal load PCB for short duration

texts:
I got 30 buck converters on 4 layer pcb (70x130mm). Each will dissipate ~2W for typically 30 seconds followed by a very long break >10min, and I'm worried about overheating. Although it is not a safety issue (the chips are protected) i would like to avoid running into these problems.

My approach:

2 Layers full copper with a lot of thermal vias. The other 2 Layers are ~90% copper.
The thermal mass of the large inductors should help
A 120mm fan directly above the components
The airflow should increase Rca (thermal resistance case to ambient) a lot

If this is not enough to get rid of the 60W of heat, I could add an aluminium block on bottom side.

Question: Do you think this is a viable solution?


texts: Transmitting multiple data streams as one signal to multiple stations

texts:
I'm thinking of a system that would take multiple data streams in, encode them into one signal, and then broadcast it out to multiple stations that could then decode the information in the signal for the one stream that station wants. I apologize for the roundabout description of the problem as I don't know what this set up is technically called; as best as I can think of it, like a reverse of CDMA.

simulate this circuit – Schematic created using CircuitLab

My question then is, is this possible, and if so, does a standard already exist?


texts: Is miniaturization of office device A/C adapters feasible?

texts:
Today I looked upon my desk: as you can see in the screenshot below, there are three plastic boxes containing A/C adapters for (I think all in the 12-20V and 1-2A range):

screen device
notebook
notebook docking station

Altogether they are worse almost 2 kilograms metal and plastic.

My question is: are these dimensions already optimal, or could be same functionality put in significantly smaller size (like more than a half, or even 1/10?)

Or is this is by physics already mature technology which is not expected to improve?

Note: with keyword "feasible" I mean the fact that I understand that miniaturization would cost more: "not feasible" means in this context like a 10-100x fold price increase.


texts:
I thought making this would be simple, but I've found it a lot harder than I anticipated!
What I mean is that I have one screen/monitor, and two video players (all video is through RGB component, RCA cables). What I need is a system to be able to switch which of the two devices is connected to the monitor, and thus has it's signal displayed.

I am aware that numerous devices such as this exist already, however I require one that can be operated wirelessly from a RF remote (since the signal has to travel through a wall). To be clear I don't mean that the video signal itself travels wirelessly, I just mean I can change the state of the switch remotely.

My current plan is to use a "wireless relay" which I found on eBay, but I'm not quite sure how these devices work, and most of the documentation for them is in Chinese so it doesn't make life easy... Here is a photo of what I'm talking about:

I'm worried that these things don't actually join a circuit, they just supply power to it when it receives a signal.

Additionally, since my video is in RGB format, (therefore it has 3 cables: Red Green and Blue) I was concerned that I would need a relay with 6 inputs, (while the one pictured only has 2). However I came up with a scheme which I think will allow me to use the two input relay, but I'm not sure... Here's a diagram of it (assuming a relay works the way I think it does)

So in one state the relay will only have IN1 connected to OUT1, and in the other state the relay will connect IN2 to OUT2, whilst closing IN1 and OUT1. I dunno... will this work or am I crazy?


texts:
I attempted to design a low-pass 2nd Order Sallen key filter that exhibits a butterworth response. Unfortunately I'm getting confused in the math that describes the response. My design has a quality factor of approximately 0.707 and a cut-off frequency of 2kHz, which to my knowledge this is equivalent to a butterworth response. I looked up the tables for a 2nd order butterworth response and obtained the polynomial:

$$s^2+1.414s+1$$

Does my pole frequency wn have to be equal to 1 for my design to exhibit a butterworth response? Thanks.

Circuit


texts:
Is there any symbol for electrical insulation?

Is there any symbol for insulated wire? is there any symbol for non-insulated wire?


texts: What limits native color depth of cheaper LCD panels?

texts: Many cheaper LCD panels have native color depth of 6 bits per channel. This makes manufacturers of monitors implement dithering to avoid banding. But what actually limits the panels in their color depth? Isn't it simply a matter of using 8-bit DACs instead of 6-bit ones? Are the latter significantly cheaper or what?


texts: Calculate Inductance of a three phase transmission line

texts:
I was trying to solve the above problem. As I have done many similar problems, I attempted it in the following way

But I was shocked when I checked the solution given in my workbook.

Please help me to understand this problem.


texts: How voltage is related to frequency in CPU?

texts:
I have a question that what is the relationship between CPU frequency(Clock Speed) and voltage. Does decreasing or increasing the voltage effects the frequency(mean frequency incrases or decreases with voltage). How frequency(Clock Speed) of CPU is inceased or decreased if it is not related to voltage? And what is the relation of V in this equation with frequency(Clock Speed):
P = CV2 f


texts: 20kg digital servo not working, probably because my frequency calculations are very wrong (raspberry pi)

texts:
summary
I changed my servos for a more powerful one and cannot get it to work, I believe it is because I can't get the right duty cycle calculation in the code
explanation
I have a robotic arm that I started programming for fun, got everything working but the servos that came with the arm where way too weak, someone recommended this one which sure look more robust, today it arrived so I thought it would be just about replace it, for my surprise it doesn't work at all.
after investigating I think it'S because I didn't set the right duty cycle, I never heard about it before but I tried to calculate it with information I found on internet, but after hours I still couldn't get it to work properly.
sometimes it moves but definitely not to the right angle and it is not consistent, but because I'm new in all of this I don't even know if that is the reason.
I'm unsure if I only need to update the SERVO_MIN_DUTY or if I must change the hertz when I set up the GPIO PWM, too.
Servos
This is the old servo:

Operating Speed : 0.17sec / 60 degrees (4.8V no load)
Operating Speed : 0.13sec / 60 degrees (6.0V no load).
Stall Torque : 13 kg-cm (180.5 oz-in) at 4.8V;
Stall Torque : 15 kg-cm (208.3 oz-in) at 6V.

this is the new servo:

Item: DS3218 20KG Large Torque Digital Servo
Stall Torque (5V): 19 kg/cm (263.8oz/in)
Stall Torque (6.8V): 21.5  kg/cm (298.5 oz/in)
Speed : 0.16 sec/60°(5V) / 0.14 sec/60°(6.8V)
Operating Voltage: 4.8 ~ 6.8 DC Volts
Dead brand: 3μs
Weight: 60 g
Motor Type: DC Motor Gear
Type: Copper & Aluminum
Working frequence: 1520μs / 333Hz
Size: 40 x 20 x 40.5 mm
Features:

High performance digital standard servo
High-precision metal gears with hard anodizing
CNC aluminium middle Shell
Dual ball bearings

The original code (I tried to update it using the data I found around without success,mostly from this guide)
import RPi.GPIO as GPIO
import time
OFFSE_DUTY = 0.5        #define pulse offset of servo
SERVO_MIN_DUTY = 2.5+OFFSE_DUTY     #define pulse duty cycle for minimum angle of servo
SERVO_MAX_DUTY = 12.5+OFFSE_DUTY    #define pulse duty cycle for maximum angle of servo
servoPin = 12

def map( value, fromLow, fromHigh, toLow, toHigh):  # map a value from one range to another range
    return (toHigh-toLow)*(value-fromLow) / (fromHigh-fromLow) + toLow

def setup():
    global p
    GPIO.setmode(GPIO.BOARD)         # use PHYSICAL GPIO Numbering
    GPIO.setup(servoPin, GPIO.OUT)   # Set servoPin to OUTPUT mode
    GPIO.output(servoPin, GPIO.LOW)  # Make servoPin output LOW level

    p = GPIO.PWM(servoPin, 50)     # set Frequece to 50Hz
    p.start(0)                     # Set initial Duty Cycle to 0

def servoWrite(angle):      # make the servo rotate to specific angle, 0-180
    if(angle<0):
        angle = 0
    elif(angle > 180):
        angle = 180
    p.ChangeDutyCycle(map(angle,0,180,SERVO_MIN_DUTY,SERVO_MAX_DUTY)) # map the angle to duty cycle and output it

def loop():
    while True:
        for dc in range(0, 181, 1):   # make servo rotate from 0 to 180 deg
            servoWrite(dc)     # Write dc value to servo
            time.sleep(0.001)
        time.sleep(0.5)
        for dc in range(180, -1, -1): # make servo rotate from 180 to 0 deg
            servoWrite(dc)
            time.sleep(0.001)
        time.sleep(0.5)

def destroy():
    p.stop()
    GPIO.cleanup()

if __name__ == '__main__':     # Program entrance
    print ('Program is starting...')
    setup()
    try:
        loop()
    except KeyboardInterrupt:  # Press ctrl-c to end the program.
        destroy()

So what exactly do I need from there to know exactly how to update the code for any servo?
The item description says 0.16 for 60° so I expected to be able to get it with a rule of 3 (for 180° I could do a 0.16 x 180 / 60 = 0.48s, but that result seems to high for my little understanding).


texts:
I have a tiny embedded system build around a Holtek HT48F06 microcontroller to monitor RFID tags (RDM630). Unfortunately it only detects the arrival, not the removal of a tag. As a workaround, I want to reset the microcontroller periodically (say once per second), since that triggers a new attempt of detection (or does that seem like a bad idea?). Using a 555, I found some suitable values (22µF, 4+100kΩ) for a timer to trigger the reset.

However, in order to delay the power-on-reset, the low-active RESET-pin of the microcontroller is connected to a RC net like the following:

simulate this circuit – Schematic created using CircuitLab

So my question is, what would be a good way to connect a timer to the reset pin, preferably without making any changes to the existing circuit (I am not to keen about fiddling with the tiny smd pcb).


texts: Programming ATMEGA328P using FTDI Failed

texts:
I have a couple ATMEGA328P. I have the FTDI Module; now I can't get the FTDI to program the 328P.
I tried all connectivity schematics; I tried with different capacitors and I can't understand why I keep getting on IDE an error Message that it can not find the board or communication on assigned port.
I would like to know if there is anyway to test if the ATMEGA328 is actually in good condition. Is there a test I can do to verify?


texts: I am experimenting with making a PCB and have created some short circuits when wiring everything up which have fried one of the traces. i was wondering whether it would be a good idea to put a fuse in the next iteration to avoid breaking the whole PCB if i should make another mistake. could anyone recommend whether this is a good idea and if so, how would i choose the right fuse? the circuit runs of a lithium battery so 4.2v -3.3v thereabouts and i am not expecting current draw about 0.5A. Many thanks.


texts:
I am not able to understand what a load resistor is and how does it relate with a load.

Can anyone explain how the load resistor works and how is it different from the general resistor.


texts: XST Verilog - Casting real to integer constants

texts:
When I try to synthesize the following Verilog code using Xilinx XST, I get the error, "Unsupported real constant".  If I try wrapping that expression in an $rtoi function, XST gives a different error: "Unsupported System Function Call".

Using the Xilinx synthesis tools, is it possible to cast a real constant to an integer constant?  If so, how?

module example(clk, n_rst, tick, done);
  parameter CLOCK_HZ  = 50_000_000;
  parameter BAUD_RATE = 3_000_000;
  input clk, n_rst;
  output reg tick, done;

  reg [31:0] counter;

  always @(posedge clk, negedge n_rst) begin
    if (!n_rst) begin
      counter <= 32'h00000000;
      tick <= 0;
      done <= 0;
    end
    else if (counter == (0.5*CLOCK_HZ/BAUD_RATE) ||    // ERROR:Xst:850 - Unsupported real constant
             counter == (1.5*CLOCK_HZ/BAUD_RATE) ||    // ERROR:Xst:850 - Unsupported real constant
             counter == (2.5*CLOCK_HZ/BAUD_RATE) ||    // ERROR:Xst:850 - Unsupported real constant
             counter == (3.5*CLOCK_HZ/BAUD_RATE) ||    // ERROR:Xst:850 - Unsupported real constant
             counter == (4.5*CLOCK_HZ/BAUD_RATE) ||    // ERROR:Xst:850 - Unsupported real constant
             counter == (5.5*CLOCK_HZ/BAUD_RATE) ||    // ERROR:Xst:850 - Unsupported real constant
             counter == (6.5*CLOCK_HZ/BAUD_RATE) ||    // ERROR:Xst:850 - Unsupported real constant
             counter == (7.5*CLOCK_HZ/BAUD_RATE) ||    // ERROR:Xst:850 - Unsupported real constant
             counter == (8.5*CLOCK_HZ/BAUD_RATE) ||    // ERROR:Xst:850 - Unsupported real constant
             counter == (9.5*CLOCK_HZ/BAUD_RATE))      // ERROR:Xst:850 - Unsupported real constant
    begin
      counter <= counter + 1;
      tick <= 1;
      done <= 0;
    end
    else if (counter == 10*CLOCK_HZ/BAUD_RATE) begin
      counter <= 32'h00000000;
      tick <= 0;
      done <= 1;
    end
    else begin
      counter <= counter + 1;
      tick <= 0;
      done <= 0;
    end
  end
endmodule


texts: How to swap one single LED for two color one that will change color depending on state

texts:
I have a display for an alarm system, which drives LEDs with 7mA current source.
It will toggle between on and not connected, according to the state of the alarm system.
What I'm trying to do is to build an add-on for the LED, that will make it drive a second LED when first one is off (and use one two-color diode for that if possible, but two separate LEDs will do)
The driver uses constant current, so I think that a not gate won't work in this setup.
I'm trying to do this as simply as possible, since there is few dozen LEDs that I would like to replace on the panel.
How do I achieve that?


texts: Routing considerations of analog signals on twisted pairs

texts:
I'm designing a part of a system that will receive 4 analog signals carried on 4 twisted pair cables which are input to an ADC. These signals are low speed (probably in KHz) bipolar ranging from -10V to +10V that should be sampled every 30us. The maximum allowed error is 15mV.

What are the routing consideration of these signals on my PCB? Should they be treated as differential pairs?

Any links with detailed technical info are much appreciated.


texts: Can a Surge Travel on a Residential House's Wiring that is higher than 6kV and 3kA?

texts:
IEEE has stated that the highest voltage and amperage that a surge can travel on home wiring is 6kV and 3kA.  Anything higher, the wiring would melt.

If this is so, how does a surge from direct or indirect lightning travel through home wiring and literally blow up electrical equipment?

I don't get it.


texts:
I am trying to find the voltage across R4 in the following circuit:

It confuses me that there are 2 voltage sources. I am not sure how to approach it, so I tried this:

First, I use Kirchoff's voltage law for the upper right loop,
$$-5(V) +20(\Omega)I_2+10(\Omega)I4=0$$ and applying the current law for the upper node, $$I_1+I_{fromVs2}=I2$$

After that, I don't know how to proceed.

How can I find the current that comes from Vs2? If I knew its resistance I could use Ohm's Law, but I don't know it. I (think that I) can find the current accross V1 from Ohm's Law, but I am not sure how to approach it. Any help is appreciated

EDIT: This is what the currents look like: