texts: Why can a charger handle more watts at a higher voltage?

texts:
Why is it that my charger that has a rating of 100-240 volts and 1.3 amps can handle/input more watts at a higher voltage when doing the formula watts=volts x amps?
In addition, why can't it, at a lower voltage, handle the same amount of watts that it can at a higher voltage?


texts:
While studying about amplifier, I came across the AC equivalent circuit of the an amplifier.
While calculating the output resistance of the amplifier, the input signal was put to zero and the load resistance was removed as shown in the figure.

What is the reason of doing so?
Link of the PDF which I was referring is here.


texts: MSP430 Launchpad connection of photoresistor and concerns regarding Launchpads protection

texts: I am using the MSP430 Launchpad and I have a question regarding photoresistors. The thing is that when you connect a LED with a pin in Launchpad, which you have configured, as output I read that you must use a resistor in series as not to damage the LED. When trying to find how to connect the photoresistor every source said that one must connect a 10kOhm resistor in series as not to damage the Launchpad. Regarding both the LED and the photoresistor as a simple resistor why in the first case we connect the resistor for the protection of the LED and in the second for the protection of the Launchpad? Also why can the Launchpad be damaged by its own voltage? I mean if a pin is configured to input and one tries to use an extremely large voltage then sure it will be damaged, but when you try to use 3.3V generated from its own Vcc whay may be damaged?


texts:
simulate this circuit – Schematic created using CircuitLab

Setup

Only one IN can be set HIGH at a time by a micro-controller

Requirement

If IN{i} = 1, LED {1 to i} should be ON

Problem

I use too many diodes here. Is there a simpler solution to convert one number to a sequence of numbers (1 to N)? I need the lights to be something like a digital meter.


texts: This is from a key telephone system and im wondering what these connector blocks are called. Also, what type of tool should you use for these things?


texts: Specifications of a motor which will light an led (momentarily) from hand-spinning?

texts:
EDIT: I feel I might have placed the emphasis wrongly in my original question so I'll try to revise it here.
In the video cited the demonstrator can be seen spinning a small "hobby" motor with her fingers and lighting an LED. Can anyone suggest what the specifications of that motor might be ? Or an actual motor which I could buy online. (I have tried reading the model number off the screen but no joy ;-). I am also interested in more general information but that's the main thing I would like to know. Thanks

In this video an LED is lit by spinning the rotor of a "hobby" electric motor.
I have tried doing just that with a number of motors and not seen the same effect (tried with LED in both polarities).
A couple of the motors used were ones I had lying around and I've no idea of their specs. Another one was this one the specifications of which can be seen on the 'specifications' tab of this web page.
The description of the motor used in the video and provided by the video maker is "Small hobby motor, 6-12 volts" but I suspect that's an insufficiently detailed description of the motor used to ensure the effect shown is seen.
What are the specifications of a motor that would work as shown ?
Secondarily, what is a useful text which outlines all parameters of such motors and what their effect would be when using the motor as a generator ?


texts: How do i navigate RC car with a gps module on it from point A to point B?

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I want to navigate the RC car from point A to point B. The gps module is used to find the current location coordinates i.e point A. The user enters the point B coordinates based on point A. I am wondering what algorithm i should use to move the rc car i.e this algorithm should tell the robot to move forward or turn right until it reaches point B.

I've been looking at kalman filtering algorithm. Is there a another algorithm out there which i can use.

Environment: The robot should navigate indoors. I have to use the GPS because it is a requirement. The GPS is the only navigation sensor present on the robot.


texts: Emitter follower: Icq and Vceq calculation

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I have problem with understanding how to calculate \$ I_{cq} \$ and \$ V_{ceq} \$ of this circuit.

Q1 has these details:
\$ h_{FC}=150 \$ and \$ h_{fc}=100 \$

As I understand it I should find \$ V_{B}=V_{cc}(\frac{R_2}{R_1+R_2})= 6V\$ then calculate \$ V_E=V_B-V_{BE}=5.3V \$

\$ I_{cq} =\frac{V_E}{r_E}\$ where \$r_E=R_E||R_L \$.

then

\$ V_{ceq} = V_{cc} - I_{cq} \cdot r_E \$

What am I doing wrong?

Is it possible to find \$ V_{ceq} \$ and \$ I_{cq} \$ with the small signal parameters \$ h_{FC} \$ and \$ h_{fc} \$?

BTW: this is NOT homework, but preparation for exams.


texts:
When I'm doing the connection, and I want to switch the layers (TOP to BOTTOM via Via), Altium automatically select some default values of Via size. I made my own Via Template, but the "Via Template" listbox is disabled.

After I create the Via, I must select it again and change the sizes to my template.

How can I enable the Via Template listbox, or set the default sizes of Via?


texts: Thickness of thermal relief on copper pour

texts:
I am working on designing a pcb that will have a copper pour. I have selected to use thermal reliefs to connect the pour to pads, but I am a little confused on the thickness. Should each spoke of the pour be as thick as a trace (assuming current will take a direct path, using only one spoke) or should I make it so the sum of the spokes equals the track thickness (assuming the current will only flow to max of a trace, then find another route)?

My current at max will be around 1 amp (and I am using traces of .035" to be safe). So with this example, should he spokes each be .035" or should each spoke be .00875"?


texts: Current Transformers and Energy Harvesting

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Current Transformers (CT)s work like any other transformer: through Faraday's law of induction, the changing magnetic flux (from the AC current flowing through the conductor) induces a proportional voltage on the secondary coil. In this case, the primary is a single winding: the conductor through a core. Typically, the CT's are used as a measurement device, and the secondary is "burdened" with a known resistance value. So, reading the voltage across the resistor gives an accurate representation of the current you're measuring.

I see CTs as sources for "energy harvesting", and have even experimented with them myself, but my question is: does a CT technically load down the original circuit?

In other words: if I have an AC circuit drawing 20A and clamp on a Current Transformer and use the CT as part of an "energy harvesting" scheme to eventually power a 10mA LED, microcontroller, or what have you... where does that 10mA come from?

Is it 10mA more being drawn from the mains, on top of the 20A? Or is the 10mA coming from an otherwise non-utilized magnetic field being converted to energy I can take advantage of (truly energy harvesting)?

Edit:

So, to sum up, a CT is simply adding a series impedance, which actually reduces the current. This actually reduces the power consumed.

simulate this circuit – Schematic created using CircuitLab

So, per the circuit above, if we were to add a CT with N = 500 turns, and put a 2 ohm burden resistor on it, the resistance (in series) placed on the conductor would be 2 * (1 / 500)^2 = 8 uOhm

Power used by the whole circuit is reduced when adding a CT. Before adding the CT, the power consumed was Vs^2 / Load. After adding the CT, the power consumed is Vs^2 / (Load + 8uOhm)

Please correct me if you feel I'm wrong


texts: Best way to send sensor readings over simple RF connection

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I have bought a pair of simple 315MHz TX/RX modules. I want to use these to connect a battery powered ATTiny85 to an Arduino base station. The ATTiny needs to regularly wake up and send a sensor reading to the base station.

In theory I should be able to simply write data to the TX and read it from the RX module. However, how do I ensure that I write/read at the correct rate? What code do I need to use to transmit at a particular speed (bytes/second)? What is the best way of doing error correction/detection?

Since I want the transmitter to be battery powered could I use a transistor to turn off VCC to the TX module when idle. What will the RX module receive when the TX module is powered down?


texts: Wha't the difference to use the junction to case thermal resistance instead of the junction to lead thermal resitance?

texts:
In case I have a diode, and I want to know it could dissipate the power, I have two values, but I can't choose between them:
- Junction to ambient thermal resitance \$R_{ja}\$
- Junction to lead thermal resitance \$R_{jl}\$

Which one should I use to know if my diode is good for my application?

Thanks


texts: What parts can I use to make 110V DC from 4 D-size alkaline or NiMH batteries?

texts:
I need help with choosing DC/DC converter parts.

I want to build D-size battery powered lantern working with typical E14 or E27 compact fluorescent lamps.

Here is my awesome idea :)

It will be supposed to work on D-size NiMh or Alkaline batteries.

Typical compact fluorescent lamps work normally with DC (there is rectifier bridge at the input anyway). I was experimenting with some old compact lamps and most of them start at 80V DC. All lamps I tried work normally at 100V DC.

I've been messing around with some low voltage easy to use converters (like step-down LM2574), I have oscilloscope, I'm able to tune-up simple converter efficiency for specyfic load needs. However I'm not inverter expert, I don't know integrated chips to build such thing.

Converter requirements:

output power at least 10W about 4W due to D-size alkaline capabilities
efficiency at least 80%
minimum input voltage 4V (3.2V would be awesome)
output voltage 110V (it may be 230V)
not complicated (i need to build this in a week - gift for sister)

The question is:

Are there any easy to use parts to build affordable DC/DC 3...7V to 110V converter?

It may be 4V, I wrote 3V because its possible to deep-discharge alkalines to 0.8V, thats 3.2V with 4 cells.

I know that LED lamps are more efficient, I'm considering using them too, but I want to stick to "typical home light sources".

I saw alkaline D discharge charts, it looks like single D size Duracell Procell can deliver 1W for 5 hours.

GP 700DH NiMh battery with 7Ah capacity can deliver much more power (14A discharge for 30 minutes or 7A for 1hour).


texts: Minimizing voltage drop across SSR when using it to pull down a TTL digital input on another device?

texts:
I have a situation that I've run into a few times. I have a digital output card in my system that uses SSRs. I'm trying to interface to a device (referred to as my DUT from here on) that has TTL digital inputs that are internally pulled up to 5 volts. To active the input, I need to short the input to ground.

However, using the SSR to connect the input to ground results in around 40 mV across the SSR and the DUT doesn't report this as ON.

I don't want to confuse the issue, but the DUT appears to be doing an analog measurement on the pin because there are certain functions on the DUT that are triggered by this pin being pulled low, and those functions do occur when I pull it low. However, there's a STATUS command I can send to the DUT to ask if this pin is low and it reports it as HIGH unless I actually short the input and ground with a piece of wire. This leads me to believe there are a couple different functions that query the status of this pin and that they must have different thresholds.

So my real question: is there an electrical way to minimize the voltage drop across the SSR in this scenario so the input of my DUT sees something closer to 0V?

Edit: I realize this is a hard question to answer without links to specific components, but in this case the SSR is a part of a digital output card (and thus I don't know real details about the specific implementation) and the DUT is a new device that might as well be a black box. I suspect the answer to my original question is "no" but thought I'd check to see if there was some general approach to making an SSR look a little more like a relay contact in certain specific applications.


texts: Can a solenoid have its magnetic field "focused"?

texts:
Imagine a solenoid generating a magnetic field. Can this field be focused so that it exists only in a certain section of that solenoid at a given time. If a typical solenoid looked like:

//////////////

... and then had current applied and generated a field around it:

~~~~~~~~~~~~~~
//////////////

I would like to adjust, say, a dial all the way to left to generate a field like:

~~
//////////////

... and then dial it to the right:

            ~~
//////////////

... or anywhere in between:

     ~~
//////////////

Is this possible with a single solenoid, or would I have to use a number of different solenoids each given current independently?


texts:
I'm sorry if this has been asked before and I know its such a broad answer but i'm confused about some parts of VHDL. The part that is confusing me is does the VHDL go on the platform or is it merely a prototype of how the design will work?

Then we have FPGA which can be changed and to change you need VHDL (correct me if i'm wrong). So does that mean that the VHDL is stored somewhere on the device\SOC or am I completely wrong in my understanding.

For example we have the following package for AMBA here.


texts: How do I choose IF for a GPS/GNSS RF Front-end?

texts:
This is a follow-on from this fascinating question on selecting a TCXO (or entire frequency plan) for a GNSS SDR RF front-end. (I also have another follow-up question here).
The MAX2769 and MAX2771 EVKs both use 16.368MHz for their reference, which is a nice easy multiplier to GPS L1 = 16.368 * 96.25 = 1575.42MHz and L2 = 75 * 1227.6MHz for the mixer.
However, from the answer to the referenced questions, there are two comments that stand out:

Different frequency plans allow you to reduce beating from quantization noise, on the other hand they may introduce spurs in the IF from the fractional PLL. If you want to squeeze out the last decibel, I would try to avoid the prime factor 1023 in XTALS and go for a more elaborate setup.

Why is this the case, and what might a more elaborate setup look like? I've noticed that U-Blox (at least in past generations) use 26MHz for their TCXO, and NovAtel use a 20MHz VCXO, implying that they do have a more sophisticated frequency plan.
Similarly, what are the implications for choosing an ADC sampling frequency that is/isn't synchronous to the GPS chipping rate?


texts:
I'm looking at the datasheet for the Bel 0ADKC /0ADKP fuses.

In it is this:

These curves don't seem correct. Notice that the curves for fuses with >= 800mA asymptotically approaches a value that doesn't match their rated current.

Is there some assumption I am unaware of? Or is this graph in error?

This isn't the case with other curves that I see, but those were fast-acting fuses and these are time-delay fuses.

For comparison these are the curves for the fast-acting Bel 0DAC/0ADAP fuses and the curves do approach the rated current.


texts:
I'm working on a PCB design homework in PADS and I've come across a symbol that I have never seen (circled in red below).  It is of a filled in rectangle with a triangle below it.  I'm thinking it might be a type of switch but I'm not sure.

What is this symbol?


texts: Which glass encapsulated component is this?

texts:
I'm trying to reverse engineer this Chinese power supply and I came across this component:

Here it is on the circuit board:

And here's a close-up:

It has a glass packaging, similar to a diode but it isn't polarised. It also has a red strip on the middle.

At first I thought it was a thermistor, then I tried measuring it's resistance while applying heat but it didn't change (always open loop).


texts:
I have heard (I'm not sure how valid it is) that EPROMs could be erased by exposure to UV light. My professor had mentioned it in my Microprocessor Design class; however, I'm not sure if he's bluffing or not.

Can anyone verify if this is true? If so, how long does it take to erase the chip, and why would one do it this way instead of erasing the chip through a programmer like it can be done today?

EDIT: My professor did in fact say EPROMs.


texts: Wireless power transmission circuit component functions description

texts:
I came across this circuit diagram above and I want to implement it but I really need an explanation on the function of the components used in the circuit diagram especially RFC and the diodes (D1 and D2).

Your inputs will be greatly appreciated.


texts: What could be the reason for this RS422 wiring?

texts:
I usually follow the following wiring scheme for RS422 wiring:

As seen above R+ to T+; R- to T-; T+ to R+ and T- to R-. So for each point to point wire R and T coupled but the signes are same i.e + to + or  - to -.

The above wiring scheme was working with different type of converters.

But recently I needed to use this converter hub.

For each port it has the pin assignments as shown:

But when I wired this as RS422 as usual it didn't work I didn't receive or send data through Hyper-terminal. But when I wired it as following it worked:

  DB9 port pin -->Instrument pin

  pin1 TxD- -----> TxD+

  pin2 TxD+ -----> TxD-

  pin3 RxD+ -----> RxD-

  pin4 RxD- -----> RxD+

  pin5 GND to  GND

It works as above but this is very different than usual wiring. Im really confused what could be the reason?


texts: BJT-piloted MOSFET circuit: Feedback requested

texts:
I had the idea to make a power converter, and I would like some feedback. I can take constructive criticism.

The basic idea was to make something where a microcontroller could drive a power MOSFET, with some isolation from the gate capacitance in the form of a pilot BJT. There are also manual start and stop buttons, in addition to the microcontroller input.

The BJT is pre-biased to save board space. I've built and tested this, and it works. However, I feel someone better than me could pick it apart, and guide me in the right direction.

I have the Eagle files in a GitHub repository: https://github.com/gregkrsak/kriner-pc

Thank you.


texts: How to get 10bit data of ADC using SPI protocol

texts:
I am doing Single master multiple slave implementation.
Master - PIC18F4550
Slave - PIC18F4520

A potentiometer is connected to the Slave. Slave will convert the Potentiometer value to digital and communicate with the master using SPI protocol.

I am getting 8bit data (ADRESH -- Left justified)correctly from slave. But I have to get 10bit data (ADRESH - 8bit, ADRESL - 2bit).

How can I get 10bit data?

Master code

OpenSPI(SPI_FOSC_64, MODE_01, SMPMID);   //SPI configuration

SSPCON1bits.WCOL = 0;    //Clearing SSPBUF
LATDbits.LATD0 = 0;  //Slave select
WriteSPI(0xFF);  //writing 0xFF to slave
for(mdelay = 0; mdelay < 10; mdelay++);
var1 = SSPBUF;
LATDbits.LATD0 = 1;
highbyte = var1;
highbyte = highbyte << 8;    //deselecting SS
for(mdelay = 0; mdelay < 100; mdelay++);

SSPCON1bits.WCOL = 0;
LATDbits.LATD0 = 0;  //2nd time slave selct
WriteSPI(0xAA);
for(mdelay = 0; mdelay < 10; mdelay++);
var2 = SSPBUF;
LATDbits.LATD0 = 1;
lowbyte = var2;
for(mdelay = 0; mdelay < 100; mdelay++);

highbyte = highbyte | lowbyte;
result = highbyte;

Slave

int Count;
unsigned char ch1,ch2,data;

ADCON0 = 0x01;   // AD Control Register 1: Enable (turn on ADC)
ADCON2 = 0x3C;   // AD Control Register 2: 20 TAD (accuracy), FOSC 4 (freq/4)
ADCON2bits.ADFM = 0;     // ADC result left justified (D10 - D2 --> ADRESH, D1 - D0 --> ADRESL)

TRISCbits.TRISC3 = 1;    //SPI pins(PIC18F4520)
TRISCbits.TRISC4 = 1;
TRISCbits.TRISC5 = 0;
TRISAbits.TRISA5 = 1;

TRISDbits.TRISD0 = 0;    //Configuring PORTD as output
TRISDbits.TRISD1 = 0;
TRISDbits.TRISD2 = 0;
TRISDbits.TRISD3 = 0;
TRISDbits.TRISD4 = 0;
TRISDbits.TRISD5 = 0;
TRISDbits.TRISD6 = 0;
TRISDbits.TRISD7 = 0;

SSPSTATbits.SMP = 0;     //Configuration of SPI register
SSPSTATbits.CKE = 0;
SSPCON1bits.CKP = 0;
SSPCON1bits.SSPM3 = 0;
SSPCON1bits.SSPM2 = 1;
SSPCON1bits.SSPM1 = 0;
SSPCON1bits.SSPM0 = 0;
SSPCON1bits.SSPEN = 1;

while(1)
{

ADCON0bits.CHS0 = 1;     //Selecting AN0 as analog input
ADCON0bits.CHS1 = 0;
ADCON0bits.CHS2 = 0;
ADCON0bits.CHS3 = 0;
ADCON0bits.GO = 1;   //Start analog to digital conversion
while (ADCON0bits.NOT_DONE);
ch1 = ADRESL;
ch2 = ADRESH;

data = SSPBUF;   //loading the SSPBUF value to some dummy varible(Previous data in SSPBUF)

//First time slave select
SSPCON1bits.WCOL = 0;    //Clearing SSPBUF register
while(PORTAbits.RA5 == 1);  //wait for slave select
SSPBUF = ch1;    //Loading ADRESH value to SSPBUF
while(SSPSTATbits.BF == 0); //wait untill the buffer is full

for(Count=0;Count<10;Count++);  //delay

//Second time slave selct
SSPCON1bits.WCOL = 0;    //Clearing SSPBUF register
while(PORTAbits.RA5 == 1);  //wait for slave select
SSPBUF = ch2;    //Loading ADRESL value to SSPBUF
while(SSPSTATbits.BF == 0); //wait untill the buffer is full

for(Count=0;Count<10;Count++);  //delay
}


texts:
I'm writing an embedded app for ATtiny88 - one of its task is to measure voltages of serial connected two 12 V car batteries.

The microcontroller is powered from around 4.5-5 V (LM317), measured voltages (~24 V and ~12 V) are connected to two ADC channels via proper voltage dividers. In my application I have to use internal bandgap reference theoretically equal to 1.1 V.

I should probably do some kind of calibration procedure, so right now I figured something like this:

Apply exact 24 V (12 V) from an external, stabilized power supply to the voltage divider.
Calculate gain coefficient for each used channel (24 (12) / mean value from ADC channel)
Store these coefficients in EEPROM and use it as a scaling factor for calculating measured voltages.

I tried to measure the internal bandgap reference - one of the ADC channels is internally connected to it - but it always returns 1023 - maximum value for a 10-bit ADC.

My question is, how to measure the voltages most accurately? The bandgap reference voltage probably varies between different chips (datasheet says 1- 1.2 V). Is there any better way to do calibration than the one I'm doing it right now? Please help.


texts:
I am building a +/- 45V power supply to drive a master-slave amplifier for a sonoluminescence experiment.  I am following a stock design, and am having massive sag problems.  The circuit powers up fine, but if I engage the LED indicators (each draws about 0.015 A), the supply starts to sag, and the voltage drops to around 10 V.  Hooking up a power resistor is much worse - 75R 100W should draw 0.6 A, but the voltage plummets to less than 1 V almost immediately.  I tried disconnecting the Varistor network, but that didn't fix the problem.  The bridge is rated at 6A 600V, so that shouldn't be the problem.  Diodes D1 and D2 are 5 1N4001 diodes in parallel, to allow more current (and because I had them laying around).

I am using the schematic shown below, based off of standard circuits in the data sheet for the LM317HV and the LM337HV (HV = high voltage versions, these can handle +/- 45 V), and Rod Elliott's Bench supply, found at: https://sound-au.com/project44.htm.

So here's what I'm using:

I plan on adding protection diodes to the output, to prevent external voltages from feeding back into circuit, but I haven't done so yet.

I would be happy to answer any questions or perform voltage/current tests to try and track down the problem.


texts: Region of Operation of MOSFET and current cutoff frequency

texts:
The current cut-off frequency for a MOSFET is defined as the frequency at which current gain (ratio of drain to source and gate to source current) is unity. Can we use MOSFET as an amplifier at frequencies higher than current cutoff frequency? If not, why so?
Should we also need to consider MOSFET gain (ratio of Vds and Vgs) while we consider frequencies of operation in MOSFET?


texts:
I was reading about H-Paramters and how they were essentially defined and couldn't quite understand this bit in the picture below.
Here are my questions:

Shouldn't Δv_BE = Δv_be as V_BE is constant (DC) and Δv_be is variable (AC), how did it become just v_be (same for the other currents/voltages).
In each paramter why did the condition variable (ex: v_CE = constant in h11) go from being a constant to being 0.
Shouldn't the variables shown on the circuits be the total ones not just the AC variables (v_eb should be v_BE)?


texts: IR LED won't turn on, but white LED will in IR repeater circuit

texts:
I have this soundbar in front of my TV, and I need to stretch my arm to operate it with the remote, so I decided to make a IR repeater as a starting analog-only (no programmable MCU) electronics project.

Link to Falstad circuit
The input is a TL1838 IR receiver 3-pin package with active low.
If I put a white LED in, it works, the LED flashes; but if I swap the LED to an IR LED, it doesn't work. If I use my camera, I can see the remote, but not the IR LED on the board.
Any help, and comments on my first circuit appreciated.


texts: Boost converter in series with buck LED driver

texts:
What I want:
Drive a 17V, 600mA COB LED from a 5V 3A USB powerbank.
Approach 1: Use a boost LED driver.
I have looked through Digikey as well as manufacturers' parametric searches to find a suitable boost LED driver. Unfortunately, the few parts that would work (e.g. the LT3477, almost 7€/piece) are either comparatively expensive, require lots of auxiliary parts or both.
Approach 2: Boost converter in series with a buck LED driver
If I were able to use a regular boost converter in series with a buck LED driver, the selection would not only be far greater but the parts would also be cheaper. Based on a forum post, connecting boost converters in series is only possible if they are of the isolated type (the boost converters I have looked at didn't mention isolation, so I reckon they are non-isolated). Does that limitation also apply to me, as I would connect a boost in series with a buck converter, not two boost converters (as buck/boost converters are very similar, I suspect it does)?
Question: Is approach 2 viable, or do I have to bite the bullet and go with approach 1? Do you have an alternative approach I haven't thought about?


texts: Safe assumption for AA and C battery current draw

texts:
I have 5 LED candles with built-in timers, but they eat batteries, so I'm hoping to use an AC adapter to power them instead.  They are all different with some using AA batteries and others using C batteries, but each of them use a pair of batteries, so I'm thinking about getting a 3V AC adapter and connect all of these candles in parallel.

What I'm unsure about is how much current is being drawn by each of these candles to make sure I get a sufficiently powerful AC adapter.  Since it changes throughout a 24 hour period, I don't have the equipment to measure and log that for even one cycle.  Are there numbers where I could safely assume that the candles won't draw more than x mA from a AA battery and y mA from a C battery?


texts:
(Image source - Edited from Figure 3 of "SUPERNODE Circuit Analysis | Step by Step with Solved Example")

In the given image why aren't the node voltages of nodes marked 1 and 2 same? There isn't any component between them and they are connected by a wire so shouldn't they be at the same potential?


texts:
A PCIe expander allows to have more PCIe slots from a single one available in the computer.

How exactly is the performance affected? Are the output slots in parallel, and therefore the bandwidth decreases by a factor of 3?


texts: Does gauge size of a signal wire has an effect to its susseptability to electromagnetic interference?

texts: Let's say you have the option to use a lower gauge wire size (i.e. thicker wire) for a signal wire that happens to be run along power wires. Will it pick up more electromagnetic interference than using a "normal" size wire for that application? And i'm not talking about high frequency signals, or other signals that require shielding. Just a genuine physics based question which i suspect it has to do with the magnetic flux passing through the conductor which in this case it will have more surface area exposed and therefore it will be more susceptible to an emf..Am i right? Thanks!


texts:
I am following a book: Data communication and networking (Behrouz-Foruzan).

It says that modulation means building a bit stream from an analog signal. However as far as I understand it's the opposite: modulation modifies a signal in a way that is able to carry information, so it converts data to a signal.

The book seems to be contradictory, and when it talks about pulse code modulation, it says it converts an analog signal to a digital signal. A figure shows a signal being transformed into a stream of data, but I thought that this job was done by a demodulator. Could someone clarify this: what does a modul


texts:
I want to run a laser diode from a battery with a minimal setup.

Suppose that I add a capacitor in parallel with the laser diode as to prevent any voltage spikes and a series resistor as to limit the current flowing through the LD (taking into account the maximum input voltage).

What problems could be expected from such setup? Would adding a fan make a difference?

It would not really matter if the input voltage causes the LD to lower its light intensity as battery drains.


texts:
I have front end module (915MHz freq band) in circuit Which is having 30dBm output power. Between This FEM and antenna I have to insert filtering circuit.
I came across few SAW filters from Murata, Kyocera, Abracon but all those are having having max. 15dBm input power specs.
So let me know how this can be taken care .

Thanks


texts: How to measure what impedance speaker to use

texts: I have an old cassette player, which doesn't have a speaker (it was taken out before). Can I measure somehow, what impedance speaker should I connect to it?


texts: Peak Current vs RMS Current when calculating Reactance

texts:
I am having a hard time getting a grip on AC circuit analysis. I have been taking my peak voltage/current and converting it to RMS current and RMS voltage so I can use ohms law and things like that to calculate values.
I just got introduced to Inductive Reactance and Capacitive Reactance but am confused as to how it relates to RMS and Peak values. Should I still make sure I am using RMS values with these equations or do I use peak?
For instance:
What inductance draws a 160mA RMS current when connected to a 110V, 25Hz source?
Assuming I want RMS values I first solve for the resistance of the circuit.

R=V/I, R=110V/160mA, R=687.5 OHMS, R=X

So my Inductive Reactance will be 687.5. I can sub this into the equation and solve for Inductance

X=2πfL, 687.5=2π(25Hz)L, L=4.3H

So my answer would be 4.3 Henries. However I began to second guess myself and wonder if I should be using peak current instead. That makes the current from 160mA to around 226mA.

Calculating resistance with peak values.

R=V/I, R=110V/226mA, R=486.7 OHMS

Calculate Reactance with 486.7 OHMS

X=2πfL, 486.7=2π(25Hz)L, L=3.1H

Just wondering if anyone could provide some insight into this, been looking all over for answers. Most places don't go into great detail.


texts: Buck converter AP65111A gives no power when bootstrap capacitor is connected

texts:
I'm using AP65111A buck converter and it works fine. It has typical beginner-level ripples, somehow manages to keep the voltage under moderate load and so on.
However, following the schematic 1:1 for 3.3V output yielded literally no power output under load.
Output capacitor is 22uF MLCC cap and input voltage is 6.5V (kind of non-negotiable factor in my use).
After I removed the capacitor C5, the converter started outputting power normally, but it gets massive voltage drop when 0.4A load is applied. It drops about 1.2-1.5V and doesn't recover even though feedback voltage is too low.

My problems being:

Why adding bootstrap capacitor causes converter to not output any power?
The IC is rated for 1.5A continuous current but gets hot and cuts off at ~1.4W (0.4A@3.3V). Could it be fault of improper value of inductor or output capacitor?
Could input voltage be a deciding factor here?

Cheers


texts: Return Paths of Signals on Flat Flex Cable

texts:
I have a 4 layer PCB with a typical stackup (signal-gnd-vcc-signal) and on the top layer there's a CMOS sensor connected with a flat flex cable...

I was wondering, since there's no reference plane underneath the cable, What would the return paths for those signals look like ? is there a chance for coupling between the signals here ?

And how to minimize that loop ? if I add a reference plane just under the cable and connector on the top layer, would that help provide a low impedance return path for those signals ?

Update: a photo of the cable


texts: What is the switching pulse pattern for FC based ANPC converter?

texts:
I am performing simulations to estimate power losses under steady state condition. The converter that I had to choose was 5 level Flying capacitor based ANPC converter. I am using PD-PWM technique for generating switching pulses. The switching pulses generated are as follows:

Can anyone please tell, if possible explain which pulses (in the figure shown above) goes to which switches (shown below) so that a 5 level output waveform can be generated during inverter mode of operation of the converter?


texts:
I was measuring the current through current mirror, when I experienced a problem. But first, I want to mention that I measured this with two ammeters of same manufacturer and same model (Mustool MT826 Digital Multimeter). Both were set to mA (milli ampere) setting of measurement and through both of them, the current measured was about 0.5 mA for both collector currents through Q1 and Q2. Then I thought that it would be better to set both of meters to uA (micro ampere) setting of measurement, and so I did. But only one at the beginning; AM1 was set to mA setting while AM2 was set to uA setting - there I spotted a problem. Suddenly, the current through AM1 was around 2.5 mA while current through AM2 was decreased to 300 uA.

So this got me thinking for a while and I came to conclusion that at different settings for current measurement, the ammeter is "seen" as different load to the emitter of Q1 and Q2. So, my question is:

Is it normal for ammeter to change its internal resistance, when we switch between different settings of measurement (uA, mA, A) or is this due to bad measuring equipment bought?

simulate this circuit – Schematic created using CircuitLab


texts:
Sometimes I read things like "This amplifier has 30dB of feedback", what figure is that refering to? the \$\beta\$ of the amplifier? or the loop gain \$1+A\beta \$? or the negative feedback factor \$\frac{1}{1+A\beta}\$?

I know that the general closed loop equation for gain is \$A=\frac{A}{1+A\beta}\$

But if the figure quoted refers to \$\beta\$, then a \$\beta=1\$ is maximum feedback, but \$20\log(\beta)\$ with a \$\beta=1\$ would mean 0 dB of feedback which doesnt make sense, because I believe that a feedback factor of 1 should give an infinite dB of feedback. So which one is it?


texts:
I am trying to understand working principle of the circuit given in the link below :

http://kripton2035.free.fr/Resources/lcmetersch.pdf

I realized that the circuit is basically relaxation oscillator with LC tank circuit attached to its non-inverting input. I know that when the output of the comparator becomes HIGH (5V) capacitor in the negative feedback path charges and and after reaching some point, voltage on the inverting input of the comparator becomes higher than the non-inverting input and the output of the comparator becomes LOW. And then the capacitor in the negative feedback path discharges and the voltage on the inverting input becomes smaller than the voltage on the non-inverting input, causing the output to go HIGH again. It goes on like that.

But the thing is I am not able to understand the effect of LC tank circuit here. I don't know how come the output frequency is equal to LC tank resonance frequency. And I am not able to understand the function of the resistance between output and non-inverting input of the comparator.

A comprehensive explanation of the circuit is the given in the link below :

http://www.vk6fh.com/vk6fh/lc_meter_vk6fh.htm

Thanks in advance!


texts: How does this circuit cause the lights to blink and after another?

texts:
I was toying around with electronic component and came to an interesting circuit. That's how it looks on my breadboard:

And this is a snippet from a simulation of an equivalent circuit:

As I understand, it's all about supplying the base of the transistor with a sufficient voltage and at the same time, reducing the base voltage at the other transistor. I'm not sure how the resistors and the capacitors together are doing that coordinated work.
What is the trick here that achieves this behavior?
More generally, I'm interested in using resistors/capacitors/transistors to create various blinking patterns with LEDs, and I feel that this circuit has the core idea to be able to do so.
Thanks in advance!


texts: How do I mount that DB9 Connector on this GPB? Any tricks?


texts: Automotive protection: TVS, thermistor, or both?

texts:
This is a follow up question regarding my previous post where I was informed my issue was due to inrush current.
I have a DC1601B-C buck-boost converter outputting 12V and up to 20 Amps. It is hooked up in an automotive circuit that is powered on with a key switch. The key switch turns on power from a 12V lead acid battery. There is also an alternator to charge the battery. I have a SLD8S17A TVS diode as protection on the input line for automotive load dump.
The regulator is supposed to be able to output up to 20A, and under my normal conditions I am running it at about 11 amps with various sensors, single board computers, and an ethernet hub. I can't go into specifics on the exact devices.
At the time of the board catching fire (as described in the post linked above) it was only powering the ethernet hub and a few of the sensors and should have only been outputting 2.25 amps maximum (could have been much less). The board was working fine, then the switch was keyed off, then back on, and that's when the fire happened.
To protect against inrush current I was thinking I would add a fuse leading to an NTC thermistor. Would this be a good solution? Should it go before or after the TVS diode? Would the thermistor work if the device was only briefly unpowered? In my research I can't seem to find a schematic of a thermistor being used with a TVS diode.
Another question is does my TVS diode need a resistor or capacitor (and what value)? I only have the TVS diode, but after some reading I have seen that some designs include a resistor before the diode to limit current.


texts:
I am wondering if there is a way for a device to receive power from both USB-C and lighting connectors. They would obviously be connected individually.
I was also wondering if it is possible to wire it so that when the Lightning cable is connected, a maximum of 5V will be delivered, and when the USB-C cable is connected, voltages of 1V and 3V can be delivered.
The device layout:


texts: Could I switch a 1/4W resistor with a 1/2W resistor?

texts: I have a Fender/Sunn SX4150 mixer and it has two resistors blown out and missing, I didn't remove them. I asked another question regarding the schematics that called for a 22 Ohm cc, which I got my answer for but the answeree also noted that instead of a 1/4W I should just make it a 1/2W. Could I do this with little to no consequences, and if so, could I just replace the 1/4's with 1/2's? What would happen if I did such a feat?


texts: I was in college 18 years ago and saw a classmate's project that had a very large DIP IC on it (roughly 1"x4" !) which he said was a digital multiplier IC. (I assume it was 32x32 -> 64) I'm curious what part that might have been and was wondering if anyone might be able to help me find it.


texts: What is the best and simple circuit diagram for a radio receiver to receive radio waves in Citizen's Band

texts:
I am building a two way radio system using the citizen's band in India.
The transmitter is using a 555 timer IC clocked at a frequency between 26.957-27.383MHz to transmit AM waves.
Can you please suggest a possible circuit diagram (with components mentioned) for an AM receiver which will be able to receive requencies between 26.957-27.383MHz ?
The circuit diagram i am following so far is :


texts: How to calculate internal generator resistance?

texts:
What's the formula for calculating generators internal resistance in a circuit with a load?

I am given the load resistance and the voltage sources voltage. What's next?

simulate this circuit – Schematic created using CircuitLab

I have tried number of ways in calculating the internal resistance of my power supply and I always get different values at different voltages.

For example:

First I measured open loop voltage of PS (Ug) then I measured voltage on output with load applied (Ul). The voltage drop on internal resistance should then be equal to: Urg = Ug - Ul  , then I measured the current drawn from PS and put it in equation: Rg = Urg / I

But it doesn't seem to be the right formula, because when I apply different voltage I get different internal resistance, which should be the same all time...


texts: Getting out of a pattern in Arduino IDE - Ultrasonic + Motors Using Arduino

texts:
I am doing my final-year project of an autonomous river cleaning robot. I seem to have a problem with my code.. For now, i want to read my Ultrasonic Sensors (HCSR-04) while getting my DC motors to move and find a route once an obstacle is detected. Since my robot is driving freely in an open water, i have program my motors to run in a specific pattern (although the pattern is not complete yet). But my problem is, once my Ultrasonic detects an obstacle, my motor does not immediately stop and find another route.. Instead, it finishes my pattern first before finding another route.

Please help me with my code and if there's any suggestions.

//Code starts here

void setup() {
//Setup program here
}

void loop() {

frontsensor();

leftsensor();

rightsensor();

if(cm1 > object){

forwardpattern();
}

if(cm1 <= object){

  findroute();
  }
}

void forwardpattern(){

forward();

delay(5000); //Move Forward for 5 second

halt();

turnright();

forward();

delay(5000); //Move Forward for 5 second

turnleft();
}

void forward(){

//motor code here
}

void findroute(){

halt();

if (cm2 < cm3){

Serial.println("Turn Right");

turnright();

}
else{

Serial.println("Turn Left");

turnleft();

}
}

void halt(){

//motor code here
}

void turnright(){

//motor code here
}

void turnleft(){

//motor code here
}

void frontsensor(){

digitalWrite(trigPin1, LOW);
delayMicroseconds(5);
digitalWrite(trigPin1, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin1, LOW);

pinMode(echoPin1, INPUT);
duration1 = pulseIn(echoPin1, HIGH);

cm1 = ((duration1)/2) / 29.1;
}

void leftsensor(){

digitalWrite(trigPin2, LOW);
delayMicroseconds(5);
digitalWrite(trigPin2, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin2, LOW);

pinMode(echoPin2, INPUT);
duration2 = pulseIn(echoPin2, HIGH);
cm2 = ((duration2)/2) / 29.1;
}

void rightsensor(){

digitalWrite(trigPin3, LOW);
delayMicroseconds(5);
digitalWrite(trigPin3, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin3, LOW);

pinMode(echoPin3, INPUT);
duration3 = pulseIn(echoPin3, HIGH);

cm3 = ((duration3)/2) / 29.1;
}


texts: pulled down io protection from overvoltage

texts:
I need to protect my IC's io form overvoltage(default is 5v). The pin has the capability to source 10 mA and sink 25mA

I tought of using a tvs diode(between pin and gnd) and a resistor(330r from pin to output connector).

The problem is i also want the pin as low when there are no input. So i used a pulldown resistor(10k).

I have the schematic here

Is this a good idea? If not how can i make it better. Any ideas?


texts: I'm attempting to calculate optimum solar panel tilts, and the best way to do this seems to be by latitude. However all i can find is calculators, i wish to be able to calculate this myself, is there any formulae for calculating the optimum tilt?


texts: Can an OR gate be made using 2 XOR and 1 and gate?

texts:
Hello i was wondering if an OR gate can be made using 2 XOR gates and 1 AND gate.
as i got this question in one of my exams a few days ago.


texts: Transient Spice Simulation of Flyback Converter

texts:
I have created a simple model of a flyback converter using the PWM switch model by Vatche Vorperian. The simulation should be transient showing the switch events. In the picture below you see the Schematic and Simulation output of V(out) and V(Switch) node. There is quite a high voltage spike over the primary winding, which I guess is caused by parasitic inductance of diode, which acts as stray inductance. This is causing the output voltage to be lower than expected (19.5V).
How can I avoid this spike?


texts:
The Wikipedia article is very short and doesn't explain the concept very well, and there aren't any other sites that I can find that give a simple explanation. What does it mean by 100% modulation? I understand the basic concepts behind amplitude modulation, frequency modulation, and pulse width modulation, but I have never really understood what is meant by the "amount" of modulation or modulation depth.

Can somebody please shed some light on the subject?

Thanks!


texts: Circuit with dual power source: Replacing diodes with MOSFETs

texts:
I'm modding an already built circuit which can operate from the current of a USB port about 90% of the time but in some specific cases it needs to draw more than the 500 mA the USB provides (it is also smart enough to shutdown itself if there's not enough current available).

I want to add an external Power Supply to it, on that case, 5V @ 3 A. Both power sources will eventually end being connected in parallel at the same pins (the idea is having the custom circuit powered from either one of the power sources or even from both at the same time). Given the constraints (also for safety reasons), power from the external PSU must not leak on the USB plug nor vice versa (but very low voltage -- in the mV scale -- are acceptable). I used diodes and ended with something like this:

While it works good enough for what I'm trying to achieve, the drop-out voltage from the diodes are causing some stability issues in the custom circuit (even when using low drop-out Schottky diodes), and in this particular scenario I can't increase the voltage from either power sources, so, with some research I discovered the possibility of using a MOSFET to achieve the same but with a very small drop-out voltage when compared with the conventional diodes approach.

The linked article explains how to do that on the Vin line with a p-MOSFET, however I couldn't achieve the same in the GND line. I tried using n-MOSFET on those lines, and while it somewhat worked, I were still getting leakages in the power sources. So, how it's done? Are there any better approach to this?


texts: ASCII value error during communication (UART) in AVR

texts:
I am trying to implement following program in Atmega328P.

#define F_CPU 1000000UL
#include <avr/io.h>
#include <uart.h>
#include <util/delay.h>
#define BUAD 9600
#define BSR ((F_CPU/16/BUAD)-1)

void initUart()
{
    UBRR0H = (BSR>>8);
    UBRR0L = BSR;                                    /////// setting the baud rate
    UCSR0B = (1<<TXEN0) | (1<<RXEN0);               //////// Enabling the transmitter and receiver
    UCSR0C = (1<<UCSZ00) | (1<<UCSZ01);         //////// Setting the frame of 8 bit for character and 1 stop bit.
}

void sendByte(uint8_t data)
{
    do
    {
    } while (!(UCSR0A & (1<<UDRE0)));
    UDR0 = data;
}

uint8_t receiveByte()
{
    do
    {} while (!(UCSR0A & (1<<RXC0)));
    return UDR0;
}

int main(void)
{
    char share;
    DDRB = 0xff;
    initUart();
    while (1)
    {
        share = receiveByte();
        sendByte(share);
        PORTB = share;

    }
    return (0);
}

What this program basically does is take a character from the terminal (I tried Bray's terminal and Tera term), display it within the terminal and show the corresponding ASCII value of the character in 8 LEDs connected to PORT B.

I can't state my problem in words so please bear with me. The problem is as follows:

When I send 'a' , I expect the LED to light up as (0b01100001). But my LEDs show up 0b11100001. The last bit is the first bit to be off in the upper nibble but that's not what I am getting.

I send 'a' but I receive á (0b11100001). Similarly when I send 0 (0b00110000), I receive 'p' (0b01110000). The first bit to be reset in the uppper nibble always sets whenever I send something. Then the wrong character is displayed in the terminal and the wrong LED representation.

I feel like there is something wrong when I receive my character into the chip from the terminal but can't figure out what exactly.


texts:
As a first step towards learning VHDL and using FPGAs, I want to implement a simple UART transmitter which only transmits a constant bit-sequence according to the UART protocol with 9600 8N1 configuration.

I'm using a Altera Cyclone II EP2C5T144C8N board which has a 50MHz clock.

The transmitter is supposed to cycle through all the bits in the bitstring repeatedely on every rising clock of the 9600 Hz clock, which is generated by a counter beforehand.

The VHDL code is as follows:

uart_test.vhdl:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.numeric_std.ALL;
use IEEE.std_logic_unsigned.ALL;

entity UART_TX is
    Port (clk9600: in std_logic;    -- 9600 Hz clock
            TX : out std_logic      -- TX pin
    );
end UART_TX;

architecture Behavioral of UART_TX is
-- dummy data
-- idle (1) for a 3 cycles, start bit (1 to 0 transition), 8 bits of data ('A'), stop bit (=1)
constant bits_to_transmit : std_logic_vector (0 to 12) := "1110100000101";
signal current_bit : std_logic :='1';
signal current_index: integer range 0 to 12 := 0;

begin
    process (clk9600) -- on every clock tick
    begin
        if rising_edge(clk9600) then
            -- grab the current bit (in first iteration current_index = 0)
            current_bit <= bits_to_transmit(current_index);
            -- increment index by one (automatically overflows back to 0)
            current_index <= current_index + 1;
        end if;
    end process;
    -- assign TX the current bit
    TX <= current_bit;
end Behavioral;

Top level entity blinky.vhdl:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.numeric_std.ALL;
use IEEE.std_logic_unsigned.ALL;
use WORK.all;

entity blinky is
    Port (clock50: in std_logic;        -- internal 50MHz clock
            TX_out : out std_logic;     -- transmit pin
            clock9600: out std_logic    -- 9600Hz clock out for debug
            );
end blinky;

architecture Behavioral of blinky is

-- counter for frequency dividing 50 MHz to 9600 (Clk period is 50000000 / 9600 / 2 = ~2604)
signal c : integer range 0 to 2604 := 0;
signal internal_clk9600 : std_logic := '0';

-- component prototypes
component UART_TX is
    Port (clk9600: in std_logic;    -- 9600 Hz clock
            TX : out std_logic      -- TX pin
    );
end component;

begin
    process begin
      wait until rising_edge(clock50);
      if (c<2604) then
          c <= c+1;
      else
          c <= 0;
          internal_clk9600 <= not internal_clk9600;
      end if;
   end process;

    clock9600 <= internal_clk9600;
    my_uart_tx : UART_TX port map (clk9600=>internal_clk9600, TX=>TX_out);
end Behavioral;

The output on the TX pin is not what I expect. It transmits the 'A', then 3 garbage characters, then 'A' again. I captured the signals with a logic analyzer:

This does not correspond at all to the bit sequence I have programmed above. It seems that it inserts 0 bits after it has cycles through, which throws off the UART decoder? The 9600 clock looks however right.

Question: What is wrong with the code that causes this?

Side note: The RTL viewer shows a circuit which looks okay to me.


texts: Best kind of battery for electric motorcycle?

texts:
I want to try and build a DIY electric motorcycle, but am having issues finding the right batteries to use.

I've tried searching for this online but there is surprisingly little information about the batteries themselves.

Ultimately I am aiming for a range of 60km, top speed of 80kph for a payload of 200kg (rider and bike). I am looking at a 48V/150 amps DC motor.

Would anyone know what kind of batteries I should be looking for (doesn't have to be a brand, just the right type, size and number)?


texts:
I have this circuit.

The input for the INA is +- 5uV.

Can somebody tell why there is a giant offset at the noninverting amplifier. Especially if i connect two non-inverting amplifiers in series it results in an +4 v offset if meausere just before the rectifier. I've tried to place buffers before the amplifer, but it doesnt seem to fix it.


texts: Is it safe to use 1/8 watt resistors in this circuit?

texts:
If I have the following circuit is it safe to use 1/8 watt resistors?

My details are as follows :

5V at 800mA == it is an old phone charger! I assume the voltage is constant but the current will depend on the load ( I don't know how to prove this, just am assuming this to be the typical behaviour of phone chargers? ) The charger itself is a Nokia AC-15X - https://www.amazon.co.uk/Nokia-AC-15X-Compact-Travel-Charger-BLACK/dp/B004I647J2
The resistors are rated at 1/8 watt.
The led draws I think 50mA.

simulate this circuit – Schematic created using CircuitLab

I know that P=IV, so if this is the case,

P=0.050A x 5V == 250mW - suggesting that this is over the 0.125 watt rating of my resistors.

If this is the case, can you recommend a decent set mixed value 5 watt resistors (just so I am safe) -- seems to be loads of little selections on 1/8 or 1/4 watt but I cannot find a nice range on higher power ranges!


texts:
I have been looking the number of methods to measure inductance of a coil if you don't have an LCR meter available, and I have had some difficulty. I designed and built a coil and I would like to confirm its inductance, which theoretically is ~\$2\mu\mathrm{H}\$.

One method is putting a resistor in series with the inductor and applying a signal. I've seen two things in regards to this one is to adjust the input frequency so that the voltage across the resistor is half the input and then work out \$L\$ using

simulate this circuit – Schematic created using CircuitLab
$$
L = \frac{R}{2\pi f\sqrt{3}}
$$
And the other is to instead adjust the input frequency until the signals are \$-45^\circ\$ (degrees) out of phase and then work out \$L\$ using
$$
L = \frac{R}{2\pi f}
$$
I've tried both these on a inductor of known value and I do not get close to the expected value. So I figure I am doing something wrong, but I am not sure what as it is a pretty simple setup. More importantly, I do not fully understand the formulas used and how one gets to these to work out the inductance.

The known inductor is \$\sim 1.5 \mu\mathrm{H}\$ (tolerance 20%) and the resistor I used was \$6.75 \mathrm{k}\Omega\$. So I also wonder if perhaps the inductor value is too low for this type of setup for measurement as I have typically seen \$\mathrm{mH}\$ in the results of the examples I have seen? Or if I choose an inappropriately valued resistor?

I then tried the LC trap, with \$10 \mathrm{nF}\$ capacitor and my inductor, and that worked for me. Pulsing the input signal and then looking at ripple frequency.
$$
f = {1\over 2\pi\sqrt{LC}}
$$
At least it appears to have as I was able to work out the inductance of the known inductor to within its tolerance. And got near to what I expected with my built coil.

simulate this circuit

Mostly I am curious about the first methods using the series resistor, as this is one of the first things that comes up when looking at how to measure inductance, And I would like to understand this better and get it to work for me if possible.


texts: Count cycles from oscillator clock to get time

texts:
first time on stackexchange, hope I'm in the right place. I am working on a project where I need to timestamp an event (which will be detected from an electrical pulse) down to a few tens of nanoseconds and synchronized with GPS (because there will be a couple of those modules that need to be synced together). I looked for a simple arduino/raspberry solution but it seems it won't do better than 1-2 us, far from ~30 ns.

I was thinking of using the 1PPS output (1Hz) of the GPS to get a very accurate time and then find the time interval between this pulse and the sensor's pulse by counting cycles of an external, high precision clock. I have found a clock which will get me under 30ns innacuracy over the 1s PPS(40MHz, 10ppb, 1ps jitter).

Now, the problem is how do I go about counting these clock cycles? My experience on the subject is very close to 0 and so is my teammate's. Any help is very much appreciated.

EDIT: It seems this is very complicated for someone who's only experience with microcontroller is sending data through serial. The perfect product for my application would be something like this: http://www.ti.com/product/TDC7201/description Just connect the two pulses to START and STOP pins and it returns the time interval. The only difference is I would need a 1s measurement (vs 8ms) but with 10-50ns precision (vs 50ps). Basically 1000x longer measurement with 1000x less precision.


texts:
I would like to measure the battery usage of my ESP32 device. As my device runs in deep sleep mode 99% of the time, it's important that the battery monitoring circuit does not add too much to the current usage while the device is asleep (I will only check battery level during the once a week that the device will be switched on).

I have followed this guide which describes a low power battery usage circuit using a p-channel mosfet to allow current through the voltage divider only when a digital IO pin is turned on.

I have attempted to simulate this circuit here, however it does not behave as expected. When I switch the digital IO to HIGH, the p-channel gate is not opened. If I replace the capacitor with a wire, it seems that the circuit at least switches on and off, but it seems there is probably an important reason for including the capacitor here.

Is there something wrong with the circuit shown in this guide? Is there something wrong with my simulation of the circuit?

(Note: I've also successfully simulated the circuit given in this answer but I prefer the jeelabs.org version simply because it uses fewer components. This question is to find out whether it will work for me.)


texts: Is impulse response always differentiation of unit step response of a system?

texts:
I was trying to solve a question in which the transfer function of a system was asked, its unit step response being given:

$$ c(t) = 1 - 10^{-t} $$

The method that the book followed was to first find out \$ C(s) \$ i.e.

$$ \mathcal{L}(c(t)) = \frac{1-9s}{s(s+1)} $$

Then find out the Laplace Transform of input i.e. \$ R(s) = \frac{1}{s} \$ (since the input was step input) and finally the transfer function =

$$ \frac{C(s)}{R(s)} = \frac{1-9s}{s+1} $$

(Answer).

But I tried to find out the transfer function by first calculating the impulse response of the system, which is equal to the time domain differetiation of unit step response. so, impulse response = \$ \frac{d}{dt}(1-10^{-t}) = (\delta(t))+10^{-t} \$ now transfer function will be Laplace Transform of Impulse response, So Transfer function = \$ 1+\frac{10}{s+1} \$

I can't figure out where is the mistake, why the answers differ when we apply a different approach.


texts: Measured Q factor of LC circuit does not correspond with calculated and simulated

texts:
Still having a problem with measured value of Q factor of parallel LC circuit. My measurememt setup looks like on the picture below. I use Function generator SFG-1003 and Oscilloscope Rohde-Schwarz RTB2002.

My LC circuit consists of:

L= 33,4 uH
R= 0.3 Ω
C=32,63 nF

Using equation, we get Q factor of 106.

I also simulated my LC circuit and using equation

getting the Q factor of 101.

But problem is with my measurements. I followed this ring down tutorial to get a Q factor:
https://www.giangrandi.ch/electronics/ringdownq/ringdownq.shtml

but my results giving me the Q factor almost nothing. I also tried to get on the resonant frequency with my signal generator, and did a measurements of bandwidth (0.707 multiplied by amplitude) but it is the same as with ring down method. I attached my results.

In my opinion, the problem is just with measurements setup, but I do not know how to use a function generator for LC circuit, which has variable impedance. In parallel LC circuit the impedance is pretty high in resonance, so how can I measure Q factor of LC circuit correctly? One idea came to my mind to use an operational amplifier to solve a problem with impedance matching. Or the problem is something else?

Thank you

!!!EDIT!!!

I edited my circuit. Put another coil on the primary side with generator. Then I placed secondary coil with capacitor (where I measure Q factor) nearby, to have loosely coupled system (10 cm). Primary coil inductance is 3.5uH and secondary coil inductance is 187uH. I did few measurements with different values of capacitor to get resonant frequencies (60kHz - 300 kHz).

With this measurement setup I did the same experiments (ring down method + ratio of resonant frequency and bandwidth)
I got results attached below:

Used capacitors [32nF 13.3nF 5.6nF 1.5nF]
As you can see measured values of Q factor and then calculated values of Q factor using ONLY DC resistance of coil(2,1ohm). With increasing resonant frequency also difference between calculated and measured values increase. This is probably evidence of AC resistance (caused by skin effect, proximity effect, etc.)

Coil with 187uH, length=6m, Diameter=0.3mm, copper wire, 3 layers.

I did another measurement setup as shown in the picture below. With L=187uH and C=1.5nF. It gives resonant frequency around 300kHz. Signal generator was tuned to 300 kHz. And I measured VPP2 and VPP1.

When reactance of coil and capacitor is equal in magnitude then parallel LC circuit in resonance is purely resistive. So when I see on my oscilloscope VPP2=2*VPP1 (2* because of impedance matching), then I get parallel resistance of LC circuit Rp.

My resistor was adjusted to 9.9kOhm. Using equation (parallel RLC circuit) Q=R*sqrt(C/L), it gives Q = 28 (measured value using bandwidth method was Q=30)

In my opinion coils were loosely coupled so damping effect of the primary coil was not so significant.
Do you think that AC resistance of LC circuit can be 5 times higher than DC resistance in frequencies around 300kHz?


texts: I have 48 new CALB LiFePO4 batteries coming in.  I want to build a 24V bank in a 8S6P configuration. I have enough room to build the 6 sets of 8P and connect the 6 sets together using the same bus bars I used to connect each 8P.  My total load from the bank will be under 150A.  My question is do I need 6 BMS's (1 for each 8P) or do I use 1 BMS to monitor each 8P bank?  If the answer is 6 BMS's, what is the amp rating for the BMS?  150/6 or 150?   Thanks in advance!


texts: Symetric power supply from two isolated supplies?

texts:
I'm trying to power a voltage transducer such as this one LEM CV3-1000

It needs a symetric +-15V supply.
I can't seem to find a +-15V supply on a DIN rail (for a reasonable price) and thought I'd do one out of two 15V supplies such as this one : MeanWell 15V

Now, I found this thread which seems to confirm that it is not a problem at all.

I'm just wondering, would a 30V power supply fit the purpose? There'd be no common ground though but would that be OK anyway? The output would be completely floating in that case, am I right?


texts: Low Pass filtering in Delta Sigma modulation

texts:
I was reading about delta sigma modulators. I read that to make the data more accurate it performs digital low pass filtering on the quantized data. So like, if we have a one bit quantizer which is pushing data out at some rate, let's assume that its a DC signal,and we take average after every four samples we increase its accuracy to 2 bits. Similarly, if we take the average every 16 samples we increase it to 4 bits.
For a single bit quantizer, it makes sense since adding 4 one bit values would result in 4 different results which could be expressed in 2 bits. Firstly, is this reasoning correct?
But suppose instead, I have a 2 bit quantizer, and I average every 4 samples, what should be the resolution of the resulting output data?
Here is the link from which I was reading:
http://ewh.ieee.org/r5/denver/sscs/References/2002_07_Analog_AN-283.pdf


texts: what would the drain voltage be if NMOS source voltage is not ground?

texts:
Hi I'm a beginner trying to learn CMOS cuicuit.

Let's say we have two NMOS connected as shown.
Given: A, B, C are connected to Vdd = 5V;
VtM1 = 0.6V is the threshold voltage of M1;
VtM2 = 0.5V  is the threshold voltage of M2.

Could someone please explain why the voltage of node "y" is Vy = Vdd - VtM1 - VtM2 ?
(which means if the input of M2, Vx = 5V - 0.6V = 4.4V, the output of M2 is Vy = 4.4V - 0.5V = 3.9V ?)


texts:
I was asked to deploy a wireless sensor network and due to some requirements I already decided to use Zigbee/802.15.4 as my networking protocol. Also, I will be measuring air quality and taking some low-res pictures with a camera.

But when it comes to the sensor nodes I'm not sure which one should I use. I already have Crossbow TelosB nodes and although they have humidity, temperature and pressure integrated sensors I think adding more sensors could be more difficult than doing so with an Arduino, since lately we can find lots of tutorials out there as well as tested configurations.

Being complexity my main criteria, which sensor nodes would you use?

Thanks, p312z


texts: What is topology of feedback for circuit?

texts:
I am confused between Voltage Shunt and Current Shunt Also mention why R2 shouldn't be considered as feedback as it is emitter degeneration resistance

Consider the above circuit why can't I consider the current being one sampled the only problem I see in doing that is that there is no load but if I consider the amplifier to of type series series that should not be a problem as current is going to considered as output quantity and why will I need to  worry about load for its measurement.


texts: Marking 3U board size on a 6U board in Altium

texts:
I have an Altium design of a board which is 6U size. I want to mark 3U size on it using some line-drawing. As I don't have hands-on on Altium so struggling to do it.

How to know the size in Altium as I need to draw 100mm x 160mm 3U board?
How to draw line for marking the above size?


texts: Where can I find a 110V/60Hz to 220V/50Hz voltage converter

texts:
I'm debugging a power supply issue with a product made for a 220V/50Hz power source.
Most made-for-USA step-up convertors provide 220V/60Hz (from a 120/60 USA mains supply).

I'd like to try providing 220V/50Hz (from a 120/60 USA electrical supply). Where can I buy such a converter?


texts: What is the purpose of this pull up resistor in totem pole?

texts:
That's a mosfet driver circuit (taken from here), I understand the operation of the circuit but i don't know what the purpose of R5 is.
Is it a pull-up resistor?. Also, would it change anything if i pulled the base of Q1 down to ground instead of pulling it up?


texts: Down sides/Cons to Dual-Sided USB connectors?

texts:
Do dual-sided USB connectors have inferior qualities compared with single-sided e.g. less mechanically reliable or reduced speed?

From reading Why do USB connectors only fit one way? it seems that this is breaking the USB specification but I have used them without problems in the past and they seemed quite robust.


texts: Is it possible to build an AND gate from a NOT gate?

texts:
I'm reading through an old physics book and the author is speculating how could he build logic gates using black holes. Taking aside the "black holes" thing, I have stumbled upon his definition for how to build an AND gate that uses a NOT gate first for one of the inputs.
It doesn't make sense to me how to build it with his procedure. Did the author make a mistake or am I missing something?

To make an AND gate using black holes, we start with the concept of the NOT gate constructed earlier. The first input stream of black holes is passed through a NOT gate so that the output stream of that interaction is “the opposite” of the original input stream. This processed stream is then put into a collision course with the second input stream. The remaining portion of the processed stream, after the collisional interaction with the second input stream, becomes the output stream of the whole AND gate (see the figure on page 141).
Let’s see how this gate works. Consider a given position in the stream. If input stream number one has a black hole in that position, then its processed opposite has a space at that position. This space then interacts with the second input stream. If the second input stream also contains ablack hole, the output stream will have a black hole. Both streams must thus have a black hole in the given position in order for the output stream to have a black hole. Although these operations are simple, with enough logic gates a computing machine of enormous complexity can be built.
In practice, a black hole computer constructed from these logic elements will be compromised [...] - The Five Ages of the Universe: Inside the Physics of Eternity, by Fred C. Adams, Greg Laughlin

P.S. The figure mentioned on page 141 is just a normal picture of the AND, NOT and OR gates.


texts:
I'm considering replacing this 16x2 LCD module found in an early '90s E-Mu synthesizer with a modern OLED equivalent.

However, apart from the Solomon name I can't find any reference to any of the markings online anywhere.  The only other identifying marks are "AC358 REV.A QIS 1793" on the 14-pin ribbon cable.

Dimensions wise, the Winstar WEH001602C range (at 85mm x 36mm) appear to be a perfect fit and are supposedly (mostly) compatible with the HD44780, but without the pinout of this board I can't tell how "plug and play" it might be, or indeed if it's even possible.

FOLLOWUP:  The WEH001602C was indeed completely compatible with my E-Mu Proteus 1 range of modules and the E-Mu "Vintage Keys" module.  I did find however that it would sometimes fail to initialise when installed in a later Proteus FX model.   It was however slightly thinner so I designed and printed a 3mm thick standoff to bring the display bezel out to the correct position.


texts: Trouble getting AL8861 LED Driver to illuminate LEDs

texts:
I am trying to get a AL8861 LED driver hooked up. Right now I've connected it to a single LED (this one) to test (see circuit below). I eventually intend to connect it to a DAC5578 Digital to Analog converter to communicate via I2C. For now, I'd like to test if the lighting circuit works.

UPDATE:
I found the primary issue - my board had an error with GND not being connected to the driver for that channel. Now I have light, but not very bright. Connecting VSET to GND or 3v3 doesn't seem to do anything. CH1+ reads 2.54v and CH1- is 0v. Still stumped...

I've connected the components and supplied 24v. As soon as I plugged it in, the LED flashed and then went dark. I've also tried connecting VSET to ground, and it begins to glow slowly but remains very dim. I tried connecting VSET to +3v and +5v (probably a bad idea) and it flashed again. Now when I connect VSET to ground I get no glow.

I get some weird results when I check the test pads voltages. Here are the readings:

(+24v) 24.30v
(VSET) 23.93v
(CH1+) 24.30v
(CH1-) 24.27v

I thought VSET would float. When I connect it to ground, it has ~60mA of current running through it.

Is my circuit wrong in some way? I appreciate any help. Thank you!

Edit:
Here's a picture of the circuit board, if that helps. I haven't yet added the indicator LED / resistor:


texts: IC for Trickle Charging vs. Fast Charging a NiMH rechargeable battery using solar and wall charger?

texts:
I want to use a solar panel to extend the use time of 3 NiMH AA's in series to power a microcontroller.

The solar panel is rated at 1 W with a max load voltage of 6.4 V and the product page is here.

The battery capacity is 2450 mAH with a nominal 1.2 V per cell and the datasheet is here. (I plan to use three, for ~3.6 V to power a microcontroller that needs 3.3 V)

My confusion is about trickle charging the battery vs. fast charging it.
I know that the trickle charging rate for a NiMH is between C/10 and C/40, which comes out to 245 mA and 61 mA, respectively, and fast charging is between C/2 and 1.2C.

My problem is finding an IC that can do both, specifically for NiMH batteries.

For slow charging, I want the input to be solar panels (varies between 0 to 5.5 V max).

For fast charging, I want the input to be a wall charger (fixed at 5 or 9 or 12 V).

Is there an IC that can take an input voltage between 250 mV - 5 V (at least, but up to 12 would be even better) and output a current between C/10 and C (but between C/40 and 1.2 C would be perfect), with automatic charge termination and switching between the two modes I mentioned above?

If such an IC doesn't exist, how can I modify an existing one to do this?


texts:
I am new to BLE mesh. I have a doubt that in BLE mesh as per  Bluetooth SIG mesh 1.0 spec , if there are hundred unprovisioned nodes, should these nodes be within direct radio contact of the provisioner? so that provisioner will be able to get unprovisioned beacons from these nodes and do provision?
What will be the case an unprovisioned node is not in direct radio range of the provisioner but within direct radio range of one of the already provisioned nodes. does Bluetooth SIG mesh 1.0 spec supports this scenario?


texts: Generating pulses via timer match output or timer ISR?

texts:
I'm using LPC1778 uC for a project and want to know what is the difference between generating pulses via timer match output and via toggling a pin in a timer ISR. What are the pros and cons of both the approaches? Which one would generate more accurate pulses? Or is there no difference between them?

The only downside I can see to generating pulses via match pins is that uC's generally have only few match pins and hence only a few pulses can be generated via a timer match, while it's possible to generate pulses at any GPIO from a timer ISR.


texts: In this Amplitude Modulation circuit, what is the purpose of the diode load (L2)?

texts: In this circuit i know that the diode mixes the signal. I know that after the diode it is a half-wave. I know that the capacitor reproduces the lost signal. I have a feeling L2 is maybe plays a part in this signal regeneration?


texts: Op-amp for pulse width modulation, 5v single rail supply

texts:
For experimental - hobbiest purpose, I'm trying to control one 3-color led with the following circuit:

Power: single rail, 5v.
Signal generator: triangular 0-5v, 500 Hz (in
next step, signal generator should be replaced by an op-amp circuit, could be a rectangular generator followed by integrator).
operational amplifier in comparator configuration. v- from signal generator; v+ from variable resistor (0-5v input).
red led with 160 ohms resistor at op-amp Vout (in next step it will be replaced by 3-color, using 3 op-amps and related variable resistors).

In this way, triangular signal is converted to rectangular with pulse width selectable via the variable resistor.

Problem: using a 741 op-amp (the one most used in the time when I studied electronics, a lot of years ago) its low and high limits restricts the valid margin to more or less 1.5v-4v.

Do you think MCP6004 is a better alternative for this application than 741 ?

Thanks a lot.


texts:
Considering an N-type semiconductor, when we talk about carrier density, it means number of electrons per unit volume. But, when we define current density(J), it is measured as total current per unit area.
Why?
Why not volume?


texts: This LM317 diagram doesn't make any sense to me

texts:
So this is the basic wiring for an LM317 as a voltage regulator, and very little of it makes sense to me. First off, if one pin is for my adjustment, why do I need \$R_1\$? \$R_2\$ will give me just about any value I need to send. Is \$R_1\$ really necessary?

It's always been my understanding that in a voltage divider circuit, you're using INPUT voltage to supply the potentiometer. Why are we using the positive end of the output voltage to supply our pot? Isn't \$R_2\$ wired wrong? If someone tells me to vary voltage to my adjustment pin, I'm going to create a voltage divider with a pot and send THAT output to the pin. But here the V+ input to the pot is the same wire as the wire going to the adjustment pin, AND the same wire coming from my V out of the 317. If I'm trying to send differing amounts of voltage to my IC, how is that supposed to work when I'm ramming a steady V out into the same location?

Lastly, forgive my ignorance of caps but if a capacitor isn't a load, isn't \$C_1\$ creating a short circuit?


texts: Hallway light switch makes bedroom light brighter

texts: In an older North American home, when I turn my bedroom light switch on, the ceiling light turns on and seems fine. When I then turn the switch for the hallway light on, then the bedroom light becomes brighter. Is the bedroom light somehow now getting 240v instead of 120v? And what would cause this?


texts: Discrete component FM radio receiver circuit - explanation needed

texts:
I have built an FM radio receiver from a kit. I'm very happy with the results! It is the Sinclair Micro FM.

My goal is to learn about discrete electronics (NO IC's.)

The radio works great, but I am having trouble understanding the very first stage: Q1.

Q1 and it's supporting components act as an RF (LO) oscillator, as well as an antenna and "RF pre-amp", as well as a mixer (to multiply the incoming RF and the LO to get the IF.) If there was a separate RF pre-amp, a separate LO, and a separate mixer, I think I would understand this better. But I like the idea of using fewer components (and NO IC's) so I hope someone can assist me.

I have attached the original version of the schematic,

And a redrawn version:

If I am doing my calculations correctly, it seems the collector of Q1 will sit at about 0.2v DC, the base at about 0.8v DC, and the emitter at about 0.1v DC. If this is correct, then the base/collector junction is forward biased. Again, if this is correct, I don't see how Q1 will amplify transient noise to begin and sustain oscillation. I also don't see how it can amplify incoming RF.

The only thought I can come up with is... incoming RF and transient noise should show up at the collector. This will affect the base to collector voltage. As the base collector junction is FORWARD biased, a small voltage change across this junction will induce an exponential current change. I am guessing this current change, maybe through the feedback capacitor from the collector to emitter, will act with regeneration and magnify the original voltage change at the collector? This seems unconventional, but I really want to understand how this circuit oscillates! When I run this circuit in a simulator, it indeed does oscillate!

Further, I am trying to understand how this circuit mixes the incoming RF with the LO. For this to happen, the two signals need to go though a non-linear circuit. At first I was told by the designer this circuit will run near cutoff. But I see this running in "saturation". Any ideas to clear this up for me?

Lastly, why is the resistor above the coil 8.6k? Is this the best value to extract the IF (about 100k)?

Thanks so much!

In response to TimWescot, Thank you Tim. If R2 was not in the picture, I understand how the common base configuration, with positive feedback, in it's active region, oscillations start and build and become self limiting. But R2 throws me off. I know it's to extract the IM (100Khz), but placing it there seems to lower the saturation current, putting the transistor into "saturation" - the base/collector junction is forward biased. All I can imagine is a small voltage increase at the collector, from thermal noise, lessens the forward bias, and the small voltage increase is passed down to the emitter (reduced), and is inversely reciprocated back to the base, reducing the forward bias on the base/collector even more, thus increasing the collector voltage even more. I see regeneration until the base/collector comes out of saturation, into active mode, limiting the growth. Am I (way) off base?


texts: Virgin Atmega32u4 USB ISP initialization failure

texts:
I custom made my own PCB to use Atmega32u4.
It's really a clone of PJRC's Teensy 2.0.
Unfortunately I cannot initialize any of my Atmel Store purchased Atmega32u4 using USBTinyISP. The schematic is below:

And the exact message is

  "avrdude.exe: initialization failed, rc=-1"

I tried 3 MCUs. All the same problem.
I have omitted all the by-pass capacitors, including UCAP.
I tried with and without any of the XTAL components installed.
Connections between my ISP and the PCB are checked.

Any pointer will be much appreciated!


texts: How to measure the component value on a PCB?

texts:
I have faced a few instances in which I need to measure resistor or capacitor value which is soldered to the PCB board (SMD component). These are very small and difficult to look the value written on it. When I measure using a multimeter I am not getting the correct value (maybe due to other components connected to it).

Is there a way by which I can measure the component's value without desoldering it?


texts: Why is wireless power transfer done between two coils at their self-resonant frequency?

texts:
I was reading this paper about wireless power transfer via strongly coupled magnetic resonance:

http://www.ijirem.org/DOC/1_Wireless%20Power%20Transfer%20via%20Strongly%20Coupled%20Magnetic7a7f01ee-bd3f-43bc-a14d-3309f1040291.pdf

I understand that power is transferred more efficiently between two coils - the transmitter and receiver coils - when they are at resonance, i.e., when they have the same frequency. I am fine with this.

But then the report mentions that the two coils operate at the self-resonance frequency, which is when the inductive component of a coil is equal to its stray capacitance. Doesn't this mean that the inductive and capacitive components of the transmitter coil cancel out each other, and no magnetic field is produced by the transmitter coil?


texts: What is the effect of the rated current for a breaker when a 230V 6A rated circuit breaker is used in a 24 V DC circuit?

texts:
I want to use a normal household breaker for connecting to a 24V circuit. The input supply is a 230V AC to 24V DC SMPS. The output of the DC converter is connected to a load (rated 180 milliamps @ 24 V) in parallel with a battery bank having two batteries of 7.2 Ah each.

If I use a normal AC MCB, and if there is a short circuit in the above circuit whereby the battery supplies a higher current, will the MCB trip?


texts: Presence of voltage in Mega+Ramps GPIO pin

texts:
I am using Arduino Mega + RAMSP 1.4 with Marlin firmware to control my machine(not exactly a 3d printer). Marlin has gcode
M42 P20 S255 ==> Turn on 20 the pin of Mega
M42 P20 S0 ==> Turn off 20 the pin of Mega

I am using this command to turn ON a MOSFET switch connected to pin 20.

When i have not put the RAMPS shield on top of mega,  this works. Pin goes high only when I send code to turn it ON.

But when I place shield on top of Mega (No 12V power is given to RAMPS, only 5 V from USB), when I first connect USB to it, I find around 2 V on Pin 20 even with out sending ON command. when sending M42 P20 S0 this goes away (0V) and get 5V for M42 P20 S255. With out shield there's no voltage when connect USB to Mega, With shield there's 2 volts on the pin and this cause MOSFET switch to turn on. Where does this voltage comes from.? First I thought this must be some noise, so added a 10K pull down resistor (since that is the common value I have seen many circuits), but it didn't work. But placing a 100 ohm works. I am not sure it's safe???

Edit:

Mega 20th pin

Ramps 20th pin

MOSFET circuit

LED on drain is to represent load, in actual circuit, power supply will e 24 V and load is fluid dispenser. My purpose is when I I send M42 P20 S255 mosfet will turn ON and give 24 V signal to liquid dispense controller. Upon receiving 24 V signal, liquid dispenser controller will dispense liquid for a set duration

No need for MOSFET switch, connect and led to pin 20 of Mega. When only mega is connected to US, LED turns OFF

with Shield on Top, LED turn ON (Not fully)


texts:
I am generating a video signal using an AD724 and a microcontroller, which is genlocked to another video signal from a camera, and am using an SN74lVC2G53 analog switch to switch between signals.

I'm using a parallel bus 7 bits wide from a GPIO port, to control the switch and generate the RGB input to the AD724.

The issue I'm having is that the output from the AD724 is delayed relative to the output from the bus, I estimate the delay to be about 250 - 300nS. As a result, the overlay video is switched in and switched out "early" as you can see from this picture below where each of the 5 vertical bars to the right has a black shadow next to it. (Ignore the 5 bars to the left which is a single overlay and only switched once).

I need to introduce a tunable delay to both the rising and falling edge of the switch signal, of around 250nS. I attempted to do this using an RC network. I found that 47pF / 4K gave approximately the correct delay, but since the delay is less than the switch toggle time in some cases, the capacitor doesn't fully charge and the switch doesn't activate. It's also introduced a blue "halo" effect, possibly because the signal isn't a sharp square edge anymore.

Here is a scope trace of the switch signal, delayed and undelayed.

My question:
What is the best way to delay this TTL switch signal, while preserving the edges and voltage levels.

Best in this context would mean with the fewest number of components, ideally avoiding an extra IC on the board.

Edit I'm also open to doing it in software. I'm using an STM32F413. It seems it ought to be possible to use the SPI to drive the switch, and clock the SPI using a clock in sync with the pixel DMA but delayed. If only there were some clever way to have the SPI read only the 7th bit out of each byte in the frame buffer.


texts: Which contactless temperature sensor/thermometer to use?

texts:
I want to measure the temperature of a liquid which is running inside a steel pipe. The temperature can be, at most, 200℃. I want to measure the temperature of that liquid using a sensor/thermometer placed on the outer surface of a pipe, and i need to connect this sensor/thermometer to an Arduino.

From the Arduino, I need to get temperature data which will be shown in a web application.

I have heard about the MLX90614 infrared Thermometer, but it supports only up to 125℃. I need an industry grade sensor for my requirement. Can anyone suggest any other options?


texts: Determining Ambient room temperature from IC's die temperature

texts:
Nowadays many IC's have inbuilt temperature sensor which probably gives the die temperature. According to my knowledge this junction temperature is always on higher/lower side respective of cold & hot environment - it never gives room temperature.

Is there any method or technique available to find ambient room temperature from the available die temperature of ICs?


texts: I recently immersed a small, 10 volt D.C. motor underwater for experimentation purposes. When I turn on the power, always to the same power level, it SOMETIMES spins effortlessly, and other times it doesn't. I had believed that it would either work or not work, period, without any "sometimes" being involved. The water used is always the same, in the same container. No variables at all exist, as far as I can determine. Any ideas why this is happening, and what if any variables am I not taking into consideration? Also, if I want it to always work underwater, what must I do?


texts: How much power can a 20AWG USB cable safely handle?

texts:
I recently got a device that uses a USB cable (USB on one end and a power connector on the other end) as a charge cable.  The device draws 16.5V, 3.65A Max.  I want to extend the charge cable by using a USB extension cable.  I tried using a 26AWG USB cable and it started to get warm so I unplugged it.  My question is, will a 20AWG USB extension cable handle that power?  Here's a link to the cable:

http://belkinbusiness.com/products/f3u134b06-usb-aa-extension-cable-mfdstp-6


texts: Information (datasheet) about stepper motor?

texts:
I've got stepper motor from a friend. But unfortunately, neither my friend or I know what kind of stepper motor it is, how much current it needs and on what voltage it operates.

Do you have any idea how I could find something about that stepper motor ? Maybe datasheet ? Anyway, here are pictures ... I think that at least someone experienced could tell me something about it based on the wires :)

Thanks !!


texts: Please see attached image. I struggling to understand why Rs is negelected in the input impedance; should'nt the total input impedance be the parrallel combination of the capacitor impedance with the Rpi plus in series with Rs?


texts: Red for +ve, black for 0v, ...which colour for -ve rail?

texts:
I'm bodging together a bench PSU from an old server PSU, about to order a mixed bag of terminal posts for the front panel but then tripped over the problem that I'm not sure what's the correct or most common colour to use for the -ve rail on a split-rail supply.

Obviously there's red for +ve, black for 0v, green for earth... but what for the -ve rail?

Commonly available terminal colours are yellow and blue, and I'm aware that blue is used in -48v telecomms supplies (either as 0v or -48v depending which side of the EU standard you are, headdesk), so it's the front runner at the moment... unless you guys know different?

I thought I'd check here before I make a hideous faux-pas.


texts: Why would metal from a pad be *underneath* the solder mask in a footprint specification?

texts:
One of TI's new regulators has a rather unusual footprint, with several pads (7-13 in this instance) requiring that the pad metal extend under the solder mask.

This is in contrast to the usual case where the solder mark starts some distance outside the pad, as is the case of pads 1-6, 14 and 15 in this instance.

What would be the purpose of having a footprint designed like this?  My guess would be heat dissipation, but it would be far more common to have a centre pad in this instance.


texts: How to lock one (or more) layers in Eagle?

texts:
I am designing a PCB using Eagle software, and the PCB has a specific shape. The shape is little complex so that it includes a number of curves, and it is really impossible to move the shape segments (layer-dimension) one by one.

But 'block' command is also hard for me in this case, since it selects components and copper traces as well.

Is there any ULP or any way to completely lock other layers and move only one layer at a time. And i cant hide the other layers while moving, since other layers convey me the position to where i should move.

there is 'Lock' tool for components, but is there any lock tool for layers ?


texts: Does this type of Dual Voltage AC Drive exist?

texts: The goal is to run a 3ph AC motor with either high or low voltage inputs.  The motor would be wired for a specified voltage and the controller drives a single output regardless of the line voltage.  I looked at VFDs but I can't seem to find a unit with a variable line input.  Does such a device exist?


texts: I know that MOSFET is in active mode. But how can I make v0 = 2.5 V?


texts:
We know that light is an electromagnetic wave. So is a radio frequency wave. From what I understand, the 50 Hz power frequency wave in our 230 V supply at home (60Hz and a lesser voltage in countries other than India) is also an electromagnetic wave. But this power frequency wave requires a medium to travel
It does not travel in free space. But light and radio waves can travel in free space.Why is this? Or, is my assumption that the the power frequency 50 Hz/60 Hz wave is electromagnetic,incorrect? Please Help....


texts:
The voltage regulation is I(Rcosa -Xsina)/Vr
For leading pf
Here %of regulation=(VRcosa-Vxsina)/Vr ×100 %=((4×0.8)-(6×0.6))/100 ×100% =-0.4
Where I am doing wrong?


texts:
I am a student working on my graduation project, which will need an Ethernet interface. For such job I choose a microcontroller with built in MAC (STM32F777BIT) and for the PHY, the LAN 8740. I have seen many schematics and reference deisgns, which helpd me deisgn my own. The interface between MAC and PHY is MII and the speed is 10BASE-T.

The problem is specially in the receive path, although I am having problems understanding the transmit timings as well. In the receive, the PHY will send a pulse clock and 28nS after (max) the data and signal lines will be driven, but from the MAC perspective it must have a Tsetup time of at least 1 nS, how can that be? In the transmit path to make the timings are also a bit strange to calculate, so a put another diagram for this.

I thought a lot about it and this is how I think it works.

Timing Receive Flow

All units are in ns, the top grey arrow is the RXCLK line and the bottom one represents the data and receive signals lines. It is assumed the propagation delay time of the clock and the data and signal lines are the same. Everything in blue is PHY related, the blue circle is the PHY itself, in red is the MAC and everything related to the MAC, except for the arrows going from bottom to top, those represent to which clock edge the bit or signal is referenced AT THAT MOMENT!! As you will see those arrows can change given the circumstances.

In the first step the clock line will be driven and after a Tval (PHY datasheet) time the signal and data lines will also be driven, at this point the “Bit x” is synchronized to the “Edge x”.

The “Edge x” and the “Bit x” will travel through the pcb with the Tval time relatively unchanged. While that, back into the PHY, it has sent another clock pulse.

Now, because the "Edge X" was generated first and the propagation time is the same relative to the data and signal lines, it arrives first at the MAC, but if we see in the MAC datasheet, it says it needs at least 1 and 1.5 ns setup time for the data and signal lines respectively. This means the “Bit X” will “miss” it’s edge clock. Now the clock edge that will latch the data and the signals into the MAC will be the next one, namely “Edge Y” and now we have a positive Tsu because before, as the clock edge was in front of the bits we had a negative Tsu.

Now the “Bit X” is waiting, “inside” the MAC, for a clock edge so the MAC latches the data. When the “Edge y” arrives it latches “Bit x” and the Tval time from the “Edge Y” to the “Bit y” will ALSO* be the Thold time for the data that was just latched. Note that the “Bit y” also missed it’s edge reference and now the clock edge that will latch it, will be the “Edge z”.

*Tval = Thold I haven’t represented both because it could confuse people, think of it as the blue arrows are behind the red one.

From now on it just repeats.

Timing Transmit Flow

•   Ttc = Time the clock takes to go from the PHY to the MAC

•   Ttd = Time the data takes to go from MAC to PHY

T0 = 0 ns       // moment the PHY drives TXCLK high;
T1 = T0 + Ttc       // propagation time of TXCLK from PHY to MAC;
T2 = T1 + Td(TXD)   // Td(TXD) delay time from the TXCLK high until the data lines are driven, as from the MAC’s datasheet;
T3 = T2 + Ttd       // total time from the referenced rise edge of TXCLK until the bits of information arrive at the PHY. Let it be Ttotal.

While all of this was going on, the PHY continued to drive the TXCLK line. How many cycles have been sent since the first one?

N=Ttotal/Tclkp = X,Y Cycles

Where TCLKP is the clock period, which for 10BASE-T is 400 ns. X is the number of full cycles and Y is a fraction of one. So to meet the Tsu  requirement of the LAN 8740:

Y*Tclkp =< Tclkp - 12ns

12ns because it is the minimum setup time for the LAN8740.

Is this way of thinking correct?

PHY Datasheet

Microcontroller Datasheet