texts: Estimation of an orthogonal component for a single-phase PLL

texts:
I'm trying to implement a single-phase PLL, for which operation I need an orthogonal component of the grid voltage.

Let the grid voltage be:

$$v_g(t)=A\sin(\omega t) + \tilde{v}(t),$$

where the latter component is a noise.

I need an estimator that would produce:

$$v_\alpha (t) = A \sin (\omega t), \quad v_\beta (t) = A \cos (\omega t)$$

Now, I've read that it is really challenging to estimate the orthogonal component. Can you tell me why a 1st order filter is not a good idea:

$$G_\alpha(s) = \frac{1}{1+sT}, \quad G_\beta (s) = \frac{1}{\omega}\frac{s}{1+sT},$$

where the filter time constant should be (at least):

$$\frac{1}{T} \geq 10\omega.$$

Note that I have to implement these filters on a microcontroller.

I've simulated the system in PLECS, and everything seems fine.

Here is a response of the estimation error:


texts: Reason for using generally TH type current sense resistors in SMPS circuits

texts:
I'm investigating SMPS circuits and I'm trying to design my own.
In my design, I have a 300mOhm current sense resistor and its power rating must be minimum 177mW so I need a 500mW resistor. I have chosen a 2512 SMD package 1W resistor for it.
When I investigated other SMPS circuits that have same specifications (same output wattage & voltage) I noticed that they have through hole type resistors. Is there a reason for it or any reason to avoid using SMD type current sense resistors?


texts: Difference between bit rate and baud rate and its origins?

texts:
Everyone seems to have different definitions everywhere I look.

According to my lecturer:

\$ R_{bit} = \frac{bits}{time} \$

\$ R_{baud} = \frac{data}{time} \$

According to manufacturers :

\$ R_{bit} = \frac{data}{time} \$

\$ R_{baud} = \frac{bits}{time} \$

Which is the correct one and why? Feel free to give the origins of why it is defined as such too.

Related question: link.


texts: designing a supercapacitor balanced charger circuit

texts:
I'm currently designing a super capacitor based emergency power supply for a system. The operating voltage of my system is around 10~12 V. Therefore I'm using 4 2.7V supercapacitors in
series to gain the required voltage. When the power is available to the circuit, the caps should
be charged and they should provide power to the system in case of a power failure. This action need to be done automatically. The supercapacitors should be charged in balance, in order to be reliable. I have designed the following circuit for the purpose. I haven't simulated or prototyped it yet. I would like to know the flaws or disadvantages of using this circuit.
Also my circuit needs to be inexpensive. So I'm preferred to be my circuit very simple.


texts: Two phase frequency doubling a rotary encoder

texts:
I have a 600ppr quadrature encoder that I would like to get the highest possible resolution out of. I need sub arc/second accuracy for my project.

I saw differential Manchester encoding as a solution but what is the standard way to increase resolution on a quadrature encoder?


texts: STM32F072C8T7 needs hardware reset upon power on to work!

texts:
When the device is connected to the ST_LINK, after firmware upload, it works perfectly fine. When I remove the ST_Link and then turn OFF and ON my device, it does not work, unless I initiate a hard reset.

Also, the device works fine when I chose the internal oscillators as a clock source (both with ST-Link connected and without it).

The problem only persists, when in the clock configuration, I choose the clock source and the HSE (external 8MHZ crystal oscillator). The Boot0 pin is pulled low using a 10K resistor. What is going on?


texts: Question about a phone wall adapter and it's current output

texts:
My phone charger (Male wall adapter to female USB) says it outputs 5V @ 2A on the back. I want to use it to plug a Male USB into.

I guess my question is; is that 2A always being output? Or is it a maximum of 2A?

I have a homemade project, that is simply 10 RGB LEDs with 5V going to the common anodes (parallel), and only the R and B are going to 200 ohm resistors going to ground to show purple light.

I tested this with the USB cable in my computer, but I want to make sure it's safe to use with this phone adapter before I plug it in. Thanks!


texts: In USB 2.0, what's the maximum delay between SETUP and DATA0 packets?

texts: In the setup stage of a USB control transfer, the host sends both the SETUP and the DATA0 packets. Assuming that the device has received the SETUP packet, how long should it wait for the DATA0 packet? I wasn't successful at finding that information in the USB 2.0 spec.


texts:
I have a hob with the touch button but not responding enough. It's a Fujistu Siemens.
The touch buttons are cover by aluminium case.

In the image above that is touch button. If I can say is a touch button, because only when the plate is pressed by any object the hob responds. I try to activate a button with my finger and it works but sometimes it does not work at all.

How can I just put normal switches or make the touch more sensitive? The buttons are powered by a pic16f886.

P.S. Can someone tell me what the heck is this? it is on every button.


texts: Is it OK to run HDMI, etc. through non-standard connectors?

texts:
I have an A/V system which takes two balanced audio inputs, two DC inputs (8.4v and 12v), and outputs HDMI and IEEE-1394.

We frequently plug and unplug the system. Each of those connectors is at a different physical location on the rig. It would be nice to plug and unplug a single cable.

I was thinking of cutting the ends off the existing cables (25 ft) and using a multi-pin circular connector, but I'm worried that using this type of connector will degrade the high-speed interfaces. I know another poster had no problems using other connectors for USB.

HDMI has a max pixel clock rate of 165MHz up through revision 1.2. IEEE-1394 uses a 98.304 Mbit/sec half duplex data transport (roughly 98Mhz per channel?).

Is the inductance and capacitance between pins of an HDMI cable assembly mostly a function of the cable itself, or do the connectors play a significant role?


texts: I have a miniature two wire PT100 and need to extend its leads. Given the temperature at which it may operate, I cannot solder extensions. Is welding an option, and if so how do I go about it?


texts: does NPN transistor allow current to flow when applying +ve to base from diff battery?

texts:
Please forgive me if this is a stupid question, I am not an electronics student but a software developer trying to understand a transistor behaviour.

I just learned about transistor a few minutes ago from a youtube video.

My question is this, if we apply +ve to the base of an NPN transistor from the +ve terminal of a battery A (-ve terminal of battery is not-connected to anything)

will it make the current flow if the emitter and collector inserted into a closed circuit where another battery B is used ?

Edit :
Here is the video that I just watched to understand transistors which lead me to the above question


texts: Calculate voltage of Led driver required for a given amount of led's

texts:
I have built some LED lights for my fish tank using six of these LED lamps:

http://www.ebay.co.uk/itm/261813680886?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I have tried using this power supply:

http://www.ebay.co.uk/itm/291074673667?_trksid=p2057872.m2749.l2649&var=590234643632&ssPageName=STRK%3AMEBIDX%3AIT

When I connected the original six white LED lamps they flashed to indicate the 12v 60w driver was being overloaded. I changed it to four LED's two on each string so the circuit was well within the drivers current parameters; however They still flashed, at this point I took a voltage measurement of between 7 and 8 volts when the lights flashed. It did however work with only two LED's connected.

The driver seems to have a fixed voltage at 12v and from what I have read I need a new driver one that compensates for the drop in voltage.

I asked the person from who I bought the LED lamps what the power requirements if the chip were and he said it would be 12v per chip so around 66V? This left me a little confused because the 12v driver worked with two chips.

Is this the correct way to calculate the voltage of the driver required? Please note I found another source for these chips who states the reserve voltage if 5v; however I believe this may be a typo from the Chinese chap and he probably meant reverse voltage. Also; constant current driver so no resistor suggestions please.

Many Thanks,

Ross.


texts: 24V H Bridge Gate driver - FOD3184 & FQP47N06

texts:
I am trying to design a H-bridge to drive 24V motors. No issue on the low side but I would like to use the FOD3184 Opto/Gate driver on the high side of the H-bridge to drive a P MOSFET and I am somewhat worried about the P-channel MOSFET being pulled to GND by the gate driver.

2 Questions for the community:

Question 1:
On the high side I would like to used a 12V Zener diode to protect the P MOSFET and limit the voltage drop to -12V. I am also thinking about adding a resistor to limit the current pulled through the diode to GND via the gate driver. I am not sure where to place the resistor (which value?) or even if this is the right approach. I already have the gate driver and the MOSFET so i would like to make use of them instead of buying new parts.

Question 2:
I also read threads on adding a capacitor across the MOSFET to control the slew rate but the thread all talked about this in the context of driving capacitive loads. In my case the load will be inductive in nature (Motors). Should i worry about this here?

I am using the Fairchild FQP47P06 and FQP50N06L on each side of the H-bridge with the FOD3184 to drive them. Supply voltage is 24V DC. PWM frequency 10-15 KHz. the motors are small... RC car type of things. I have 2 steeper and 2 BLDC running at less than 1Amp current.

Proposed circuit change based on the answer from Rioraxe:

-12V Negative power supply: (is the polarity of the capacitors correct?). In this circuit the LM7912 makes me think of a normal voltage regulator connected upside down Power to GND Pin and GND to the Input pin... i'll have to test this on a breadboard.

Let me know.


texts: Connecting grounds when using an isolated DC/DC converter

texts:
I am designing a PCB that needs to convert 24V DC to 5V DC @ 8 amps. I would like to use an off-the-shelf converter and virtually everything in that range is an isolated DC-DC converter. Is there any harm in connecting the VOut- to the VIn- and destroying the "isolated" part of the converter (that I do not need in the first place)? I am planning on using a Murata UEI-30W.

I just want to make sure that there is no downside (i.e. power supply blowing up or unstable) if I connect the input and output grounds. The reason the grounds cannot be isolated is that the devices that requires 5V will share a common metal chassis ground with the devices that require 24V. So, there will be no isolation of grounds regardless.


texts:
This is Carlo Gavazzi Power Analyzer, the sticker says

Input 3x380(660)V

Does it means that the maximum input voltage per line must be 380V or 660V?


texts: How to determine the need for a blocking diode

texts:
I am powering an Arduino using a DC/DC converter to the Vin pin. The supply voltage is 32V and the output is 12V with a 500mA limit. The manufacturer recommends using a blocking diode "if current can flow backwards into the output".

How can I determine if such a condition exists? I know the value of the diode should be between 25-50V and 0.625-1.25A.

I'm not powering any motors or other devices that, when shut down could drive current backward. I AM powering a DMX output to LEDs (separately powered) and an RS485 network with 42 transceivers (150 ft. of cable). Each node on this network will have another Arduino attached with an identical power supply.


texts: TTL signal: output impedance, overshoot and other characteristics

texts:
I have an assignment for my Electronic Measurements and Instrumentation course, specifically me and my group were asked to perform time and voltage measurements using reflectometry on coaxial cables. We used an Agilent 33120A waveform generator and a HP 54600B oscilloscope.

One specific task was to measure the propagation delay over an adapted 5m coaxial cable: having plugged T connectors to both the scope's channels, we connected the waveform generator to the first channel, plugged a 5 m coaxial cable to both T connectors, and we adapted the line connecting a 50 ohm plug to the second T connector. This way, we could see approximately the same signal at the start and at the end of the cable, and measure the delay between the two signals. We executed this task using both a 1kHz square wave and the sync signal from the waveform generator, which apparently is a TTL output. From the manual: "For sine, square, triangle, and ramp waveforms, the sync signal is a TTL “high” when the waveform’s output is positive, relative to zero volts (or the dc offset value). The signal is a TTL “low” when the output is negative, relative to zero volts (or the dc offset value)".

Here is a comparison between the generated square wave and the sync signal:

Here is a capture showing a generated square wave at 15MHz (upper limit of the waveform generator), and the related sync signal. Keeping in mind that the scope's f3 is at 100MHz (we will never see a real 15MHz square wave on this scope), you can clearly see that the sync signal and the "normal" output are generated differently.

I'm not familiar with TTL modules (I know they are a BJT technology used in the manufacture of logic gates, but that's it), a bit of searching revealed to me that TTL signals are very badly suited to transmission lines because of their varying output impedance on their "high" and "low" levels. In fact, the displayed sync wave (connecting the sync output directly to one of the channels of the scope, reading voltage over an open circuit basically) is an approx. 4V square wave with a 400mV overshoot (approximately 100us long), and with an approx. 200mV DC offset, which is consistent with my findings (TTL low levels are 0-0,4V, while TTL high levels are 2,2V-VCC). If I read the voltage differential on the coax with the 50 ohm terminator plugged in, the overshoot completely disappears (and of course voltage approximately halves). Why is this? Is this related to that variable output impedance?

Another question is: time measurements are best taken using the ordinary square wave or the sync wave? The sync wave has a much faster rise time, so I'd point to the latter.


texts: Will current flow between the loops in this case?

texts:
Will current flow between the loops through the link BC in this case?

I think no, because on both sides of the 1 ohm resistance, the potential is the same, so current shouldn't flow as there's no potential difference there. (But is this reason correct?)

But now, what if I remove the 1 ohm resistor? Will current flow now? What will happen in this case? (Assuming everything is ideal) Will the current eventually fall in the loop with the lower potential?  Here, there is a potential difference between B and C, so charge should flow in, right?


texts: Why is inductance (L) proportional with turns-square (N²)?

texts:
We start from the Maxwell's Equation

$$
\mathbf{\nabla} \times \mathbf{B} = \mu \mathbf{J} + \overbrace{\mu \epsilon \dfrac{\partial \mathbf{E}}{\partial t}}^0.
$$

We take surface integration of both sides, for the surface (\$s\$) inside the mean path (\$c\$) of the core.

$$
\int_s \left( \mathbf{\nabla} \times \mathbf{B} \right) \cdot d\mathbf{s} = \mu \int_s \mathbf{J} \cdot d\mathbf{s}
$$

We use the Stroke's Theorem to rewrite the left hand side; where \$c\$ is in the same direction with the magnetic flux \$\Phi\$.

$$
\oint_c \mathbf{B} \cdot d \mathbf{\ell} = \mu N I
$$

(The integral on the left hand side results \$NI\$, because there are \$N\$ different wires on the winding.)

The magnetic field density inside these kind of cores are considered to be uniform. So, we can write

$$
B \ell_c \overset\sim= \mu NI \implies B = \dfrac{\mu NI}{\ell_c};
$$

where \$\ell_c\$ is the mean path lenght of the core.

We can find magnetic flux from the magnetic flux density we have found by using the cross sectional area of the core \$A_c\$.

$$
\Phi = BA_c = \dfrac{\mu NIA_c}{\ell_c}
$$

By definition, inductance is the amount of magnetic flux generated per applied current, that is

$$
L \overset\triangle= \dfrac{\Phi}{I}.
$$

So, we find inductance of the system as

$$
\boxed{ L = \dfrac{\Phi}{I} = \dfrac{\dfrac{\mu NIA_c}{\ell_c}}{I} = \dfrac{\mu NA_c}{\ell_c} }.
$$

But, all other sources (example) give inductance of an inductor like this as

$$
L = \dfrac{\mu N^2A_c}{\ell_c}.
$$

What is the mistake I did in my derivation? Please explain in detail.


texts: How to set up ATmega168 timer to turn on LED after x amount of time then turn off after 5 s?

texts:
I am new to AVR programming, what I am trying to do is configure two buttons representing different time delays, so when I press a button it will have a time delay then the led turns on then turns off after 5 seconds. I have one button(PC3) set for 10 seconds and a second button(PB5) set for 15 seconds.
What I have working are the buttons and the time delays. When I press button one, after 10 seconds the led light turns on then turns off after 5 seconds but this only works every other time. after the LED turns off, if I try to press any button again the light turns on immediately with no delay then turns off after 5 seconds. If I press a button again after this failure it will work correctly, so it works exactly every other time. I had tried setting up a 5 second timer but was having no luck at all so I tried using a 5 seconds delay instead so I am at least able to turn the LED off after 5 seconds. Below is the code I am using, help is much appreciated thanks.
#define F_CPU 8000000UL
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
void timer1_init()  //10 second timer
{
    TCCR1B |= (1 << WGM12)|(1 << CS12); //sets up timer with prescaler 256 and CTC mode
    TCNT1 = 0;                          //initialize counter
    OCR1A = 39058;                      //initialize compare value
    TIMSK1 |= (1 << OCIE1A);            //enable compare interrupt
    sei();
}

void timer2_init()  //15 second timer
{
    TCCR1B |= (1 << WGM12)|(1 << CS12); //sets up timer with prescaler 256 and CTC mode
    TCNT1 = 0;                          //initialize counter
    OCR1A = 58586;                      //initialize compare value
    TIMSK1 |= (1 << OCIE1A);            //enable compare interrupt
    sei();                              //enable interrupts
}

ISR(TIMER1_COMPA_vect)                  //Interrupt service routine
{
        PORTC ^= (1 << 0);              //Turn on led
}

int main(void)
{
    DDRC = 0xFF;
    DDRB = 0xFF;
    PINC ^= (0 << 3);
    PINB ^= (0 << 5);
    while(1)
    {
        if((PINC & (0b00001000)))       //If button 1 is pressed, toggle led on after 10 seconds for duration of 5 seconds
        {
            timer1_init();
        }
        else if((PINB & (0b00100000)))  //If button 2 is pressed, toggle led on after 15 seconds for duration of 5 seconds
        {
            timer2_init();
        }
        if((PINC & (0b00000001)))       //If LED is on
        {
            _delay_ms(625);             //5 second delay for 8MHz clock
            PINC ^= (0 << 0);           //Turn off LED
            TCNT1 = 0;                  //Reset timer
            cli();                      //Disable interrupts
        }
    }
}


texts: Boost converter with pulse skipping modulation

texts:
With boost converter using pulse skipping modulation, how is it possible for it to keep output voltage constant when load current increases?
When load current increases, the output voltage decreases significantly and the pulse is switched on. But even the pulse is on with duty cycle fixed, the output voltage will decrease.


texts: Distance confusion about Shuncom SZ05-ADV ZigBee module

texts: I ordered this module looking at the datasheet that it has a range of 2000m LOS distance. But now when I test it, I can receive signal from a maximum of 50m distance! It sends 2.4GHz signals. As far I understand, LOS distance means straight line distance. Am I making any wrong assumption about the datasheet?


texts: Single Suppy Opamp for inverting amplifier produce negative voltage signal

texts:
i made an inverting amplifier circuit using CA3130, the supply just the positive voltage and GND for V- supply. the circuit is used for full wave rectifier because the signal is around 1 MHz and 500 mV and i don't find any good diode for that frequency. the problem is, i expected only the positive voltage signal is produced but then the negative signal was appeared too in oscilloscope, how is this even possible?

simulate this circuit – Schematic created using CircuitLab

Thank you


texts: Function generator directly from power on to use

texts: I'm using a function generator. When I power it on, I need to push a button so I can use it (AFG 3022.) Is it possible to do something (the settings says nothing about this) so when I power ON it directly passes the standby stage and can be used without pressing the button?


texts: Modifying existing PCB design of nodeMCU

texts:
I am looking for a way to modify existing nodeMCU PCB layout. I want to re-build it from scratch and add more components to it namely 0.96dpi LED display and few buttons. I want to also change the existing dimensions of the PCB Board. That means I need a project file, whoes components placement can be modified. I am using Eagle for PCB designing.

P.S I can't use genral purpose PCB for a fully fledged working Prototype.


texts: How does 30W adapter charge faster than 12W?

texts:
One of the popular tablet company claims their product charges two times faster when used with 30W instead of 12W.

What is the relation between charge speed and Wattage of the adapter.

My confusion arises from the fact that imagine you have two 12V supply one with 30W and the other 12W. When you connect 10k Ohm load they will both supply the same current.

How come 30W adapter charges faster assuming it outputs the same voltage with 12W one?


texts: Unable to communicate with Xbee using XCTU, didn't get device serial number

texts:
I am using Xbee Pro S1 modules with Rhydzo labz XBee Explorer Regulated with 3v3 to 5V Converter and XBEE Explorer USB in order to connect them to Microcontroller(Atmega 16)and laptop.To configure them i am using XCTU, but when ever i tried to test the modules, everytime a error comes(I am unable to upload screenshots) but that is similar to this question asked earlier.I didnt get any help from this.I also followed this link but even though it didn't make any changes.

I tried to do it manually.In XCTU in Modem Configuration>Modem type i select XBP24 and then i give the PAN ID(Pan id need to be same in both TX/RX) and then i gave Destination address high and low.Then i checked "Always update firmware checkbox" and then clicked write,it start doing something in my module, the TX LED of my module start blinking a message start coming on XCTU "getting modem parameter" and then Found bootloader active reprogramming firmware and the after some time, a message flashes on the XCTU "Getting modem type....Programming modem...Lost communication with modem
Found bootloader active reprogramming firmware.
Write Parameters...Failed", i cant get what i am doing wrong.I even followed a DIGI document to how to load XCTU bootloader with the help of terminal window on XCTU, Check DTR, Uncheck CST, check Break, then reset module, then uncheck break and write B on terminal of XCTU and it must return a Bootloader menu, but it never happen.

I am not able to get what should i do, i am totally stucked up.


texts: Part Name Identification - PCB mounted wire clamp terminal

texts:
I have a wall outlet that i took apart, and there are mounted wire terminal blocks there. I tried searching for what kind they are, and couldn't find anything. There is a screw that tightens a paddle blade to a mounted wire terminal with a U shape for the screw.

What is the actual technical name of this type of wire terminal clamp?


texts: Why do most PWM LED displays and backlights operate at a relatively low frequency?

texts:
All around me are a bunch of electronics: digital clocks, my laptop, a refrigerator, a dimmable flashlight, and more.
What they all have is perceptible flickering of their displays due to PWM, especially when I make quick eye movements (i.e. normal everyday vision).

I've played around with PWM and LEDs before; flickering becomes comfortably imperceptible at 1000Hz or so, which is trivial for a microcontroller, even perhaps inconsiderable.

I realize some devices may be governed by mains frequency, but as far as I know, a lot of my electronics use filtered DC power.

Why can't every LED display be designed so that no flickering occurs?
I can think of a few reasons for our current situation:

We have a bunch of lazy engineers
Cost reasons -- maybe they're using some absolute worst microcontroller to save a few pennies
Efficiency -- I know PWM is more efficient than constant current, and I guess the higher the frequency the closer it is to constant current (can I assume that?), but I'd be surprised if there was a major difference between 100Hz and 1000Hz.
I am literally the only person bothered by this.

Thoughts, anyone? I do hope I'm not the only one.


texts: What is the use of dual differential amplifiers in audio applications?

texts:
Why do audio amplifiers use dual differential pairs sometimes?

Is there a mathematical justification and not just "the joy of symmetry"?
Any hints, especially with some math would be of great help.

Example of an input stage constructed this way.

From: http://users.ece.gatech.edu/mleach/lowtim/instage.html


texts:
Is this the way this circuit works ?

Vcc = 15v
With vref = 5v on the pin #5, then Vthreshold = 5v, and Vtrigger = 2.5v, meaning that
Vo = 0    when the capacitor voltage on pin #6 is Vc > 5v

Vo = VCC  when the voltage on pin #2 is DCC < 2.5v

The capacitor doesnt start to charge until T/2, when the pin #2 triggers, and the timer puts Vo = Vcc.
When the voltage on the capacitor Vc = 5v for pin #6, the timer puts Vo = 0, and the capacitor discharges through pin #7.

If there´s a constant current of:
 VbaseQ1 = (15*5.6k)/(5.6k + 3.6k)
 VbaseQ1 = 9.1304v

 V330 = 15 - 0.7 - VbaseQ1
 V330 = 5.1696v

 Ie = V330 / 330
 Ic = Ie = 15.6654 mA

Finally the tcharge, with Vc = I*t/c, for Vc = 5v
tcharge = 3.1918ms

If the charging starts at 8.3333ms, the capacitor charges until t = 11.5251ms


texts: I just started mesh analysis, but don't really understand the concept of a loop current. The current in different parts of a loop is not necessarily constant - two parts of the same loop can have different currents. So how can you define one current for the whole loop?


texts: Pre-biased Bipolar Transistor (BJT) Tradeoffs

texts:
If you go to the Discrete Semiconductor category on Mouser.com, there is a section for "Bipolar Transistors - Pre-Biased".

Is this as simple as including a resistor in series with the base?
Are there other nuances about this type of package?


texts:
I need to remotely switch a 48 V battery that is supplying a 15 A load (which is slightly inductive), as part of a low voltage protection circuit for a PV solar system.
Am familiar with the challenges around breaking DC current, have used contactors for 24 V designs, and know what a DC1 rating means. But looking online at various contactor’s data sheets, 48 V seems to incur a much higher price.
Can anyone suggest a low cost contactor that is up to the job? One with DC rated contacts, not just a 400 V AC one that may (or may not) be OK at 48 V DC. There must be ones typically used in 48 V solar designs, but I haven’t found any.


texts: Arduino low power consumption and multiplexer

texts:
I've got a project that uses an Arduino with the LadyAda audio shield and a multiplexer to play sounds in response to button presses.  I'm planning on using a MAX667 voltage regulator which has a low quiescent current, as well as using the ATmega sleep capability to put the Arduino (actually ATMEGA328P chip without the Arduino to bypass its regulator which has a relatively high quiescent current) to sleep.  This is because it will be operating on 4 D-cell batteries.  I'm going to wire the buttons to a multiplexer (TI SN74150N 16:1) as well as to pin 2 which will allow me to wake up the ATmega IC.  I have several questions:

The mux has an average power consumption of 40 mA; average power dissipation of 200 mW at 5 V should yield 40 mA).  I want to put it to sleep.  Can I use a transistor (like a 2N3904) connected to a digital Atmega pin to turn off power to the mux even if the ATmega IC is sleeping?  Will its state be retained in low power mode?
The ATmega interrupt pin requires LOW level to trigger the interrupt to wake up (for the deep sleep modes). I was planning on configuring the buttons (normally open) as pull-up switches.
[2A] Since the interrupt requires a LOW, I will need to make these as pull-down switches. Will this pull-down configuration consume extra power when the IC is sleeping?
[2B] Alternatively, I could use a transistor to form a logic NOT.  Will this consume increased power?
In general, how does one determine the "quiescent current" of a transistor?  In other words, how much power does the transistor take to operate?
Is there a better way of doing this?


texts: Implementing Feedfoward from a Feedback Control System

texts:
In a standard feedback control system, you have a set point, a controller, a plant, and a sensor to enable feedback. The sensor measures the process variable (or in other words, the argument you are actually trying to control).

Now, I want to add a feedforward component. Referring to this MATLAB  example, when implementing feedforward component, you require an additional disturbance model and a feedforward controller.

This is where I need some clarification. When adding a feedforward component, do I have to measure the disturbance separately from the process variable? Or is disturbance equal to my process variable itself? If the prior, in my system, I only have a sensor to measure to the process variable and I have no way of measuring the disturbance. Is it possible to implement a feedforward component into my control system?


texts: Aluminum electrolytic vs. tantalum capacitor for buffering SAR ADC Ref input

texts:
I want to use the ADS8317 16-Bit SAR A/D converter and have read through the datasheet. In there, ti recommend using a low ESR 47µF tantalum capacitor to buffer the reference input. Now, my reference is already buffered with a 220µF low ESR aluminum electrolytic capacitor (Panasonic FR 220µF/16V; 130mOhm ESR at 100kHz), and I'm wondering whether that's enough, or if the tantalum has some important advantage.

As far as I can tell, the important factors should be that the capacitor is large enough and "fast" enough to charge the internal capacitors of the ADC to 16 bit accuracy within the required time, similar to the signal inputs. However, I think the reference input might see a charge transfer for every bit of the SAR instead of only once during the acquisition time - if that is the case, the charge transfer would have to be faster. The smallest time I can imagine for this would be half a clock period - 500ns in my case.

Ok, but - is my aluminum electrolytic capacitor up to the task (perhaps assisted by a smaller ceramic right next to the input)? As far as I know they are not good for "high frequency" applications, but I don't know any actual numbers.


texts:
Is it possible to buy two pre-coupled bluetooth chips? So all i have to worry about is sending USB/Serial data to the master node..

Best regards,
Morten


texts: Li-ion battery charging and cell balancing

texts:
Is there a solution where a single chip can handle Li-ion battery pack charging and cell balancing as well.

I was looking into TI's range of battery management products and their battery charger chips don't feature cell balancing. They do have a seperate range of products that do fuel guage and cell balancing.

So for this application I would probably need to use 1 battery charger chip and 1 fuel guage/cell balancer chip however there are no application notes on their site of how to use both of these together and whether if this is recommended or no.

I want to charge 3 Li-ion batteries (18650) which are in series.


texts: Preventing Verilog module from being optimised away

texts:
I have tried to put lots of inverters to stress test my Spartan 6 power supply as recommended here. Here is the basic module:

module inverter(
  input wire clk
);
  reg [7:0] inverted;
  always @(posedge clk) begin
    inverted <= ~inverted;
  end
endmodule

I was told that because this module only has inputs, it will be optimised away, and indeed ISE is telling me:

 WARNING:HDLCompiler:1499 - Empty module <inverter> remains a black box.

How can I prevent ISE from optimising away my inverters?


texts: ESP8266-12 F/Moisture Sensor Analog Reading Problem

texts:
I am using an ESP8266 12 F Module with 3 x 1,2 V Batteries (3,6 Volt)
I connected a chinese soil moisture sensor like this (LINK) to the anaolog pin of the ESP8266 Module. The Module works from 3,3 Volt on to 5 V.

Problem: The Sensor gives back 1024 every time no matter what the actual moisture conditions are. Dry Conditions = 1024, Fully under Water = 1024

I tried the same with an NodeMCU Module which uses the same ESP8266 Chip and there where no problems with the analog reading.

Question 1: I found out that the ESP8266 12 F has an analoge pin capable of reading only values from 0-1 Volt so this could explain the high reading on every measurement when supplied with 3,6 Volt and under wet conditions.I still don't understand why the sensor returns 1024 even if there are absolutely dry conditions. Shouldn't there be a 0 reading?

Question 2: I know that I need some kind of voltage divider e.g. two resistors and would appreciate some hint which ones I should use. The NodeMCU Module seems to have a voltage divider on board and that's why everything worked with this module.


texts: What chemistry are lithium-ion AA rechargeable batteries using?

texts:
Recently I've seen rechargeable lithium-ion AA's for sale, but I sure don't want ICR in my pocket or anywhere else near me, and they are 1.5VDC as needed for standard AA, which means something interesting is going on.  Anyone know chemistries for any of these, or the best ways to find out?
Please note that I'm asking what sort of lithium-ion: IMR, ICR, INR...?


texts: Preventing corrosion of copper PCB tracks

texts:
I do DIY PCB with the following steps:

1) Apply the circuit diagram on a presensitized PCB via an UV lamp
2) place it into positive developer (NaOH)
3) clean it via water
4) place it into an etching solution (sodium persulfate)
5) clean it via water
6) dry it then clean it via Acetone (to solder easier)
7) drill & solder

I produced several PCBs and noticed that the copper parts are getting corroded in a month or so.

What chemical/material do I need to apply in order to prevent them to get corroded? I guess that procedure should be done after step 6, right?


texts: Good checklist for PCB design to be used by the EE (not by the PCB designer)

texts: I don't do my own CAD work.  I have a mental checklist of what to look for when the PCB is placed, critical routed and routed.  But is there a good checklist you have or can point me to?  I'm not looking for schematic items, that is covered here.


texts: My capacitor is not available anywhere, but there are close ones

texts:
I have a Harbor Breeze ceiling fan that has a buzz to it.
I've been told a new capacitor will fix this problem.
It is a C61 e185116 5 wire 250 VAC capacitor with a 4.5uF then a 6.5uF and then a 6.5uF rating. I'm assuming they are the rated uF for each speed. I cant find it anywhere on the web.
I can find a 5uF + 6.5uF + 6.5uF capacitor.
Can I use it in my ceiling fan without any issues (FIRE is my biggest concern) if it shortens the motors life a bit that is okay. That is to say not shortened by a week.


texts:
Very often we apply to circuits sinusoidal or constant voltages, and we study methods (like the phasors method) to analyze them. Here's a simple question to which, in many years, I have found not yet an answer: how can it be possible that a signal starts from -infinity and goes to +infinity? When studying sinusoidal circuits, every text applies a sinus or cosinus input (which never has a beginning), but there must be an exact moment in which the circuit switches on.

Another question: if I consider amplitude modulation, we know that a generic signal m(t) must be multiplied by cosinus in order to shift its spectrum, then the receiver will build again the original signal in some way, which is now not important. The questions are:

1st: the cosinus which multiplies m(t) in theory starts from minus infinity and finishes in + infinity; in reality every phisical signal must have a beginning, then: how theory would be modified if I consider a "real" signal (=a signal which has a beginning and a stop)?

2nd: In the theory of AM, the signal m(t) is already known (I mean, I can plot the graph of the function, I know m(t) in every instant), then I know for sure its spectrum. But if I think to a radio presenter, when he speaks the signal does not yet exist, I mean: m(t) is a "real time" signal, I don't know m(t) in every instant but it is "under construction". As a consequence, I don't know its spectrum and it seems to me that all the theory of AM is no more valid.


texts: Why do resistors still use color coding?

texts:
I always wondered why color coding is still used on resistors in 2014.

Here is Wikipedia's word on the original reason why :

  Colorbands were commonly used (especially on resistors) because they
  were easily printed on tiny components, decreasing construction costs.
  However, there were drawbacks, especially for color blind people.
  Overheating of a component, or dirt accumulation, may make it
  impossible to distinguish brown from red from orange. Advances in
  printing technology have made printed numbers practical for small
  components, which are often found in modern electronics.

However, like pointed out in this quote, printing small numbers on electronic is now quite an easy thing (or so it seems) and it would, in my opinion, be much more convenient, especially for colour-blind people.

Is there reason why we still use colour coding on resistors in 2014?


texts: Can I place a relay at the output pin of a 555-timer

texts:
I recently remember running across a bunch of articles on web about the 555-timer, it’s my first IC.

I’m getting more familiar with it, and I want to know run it in a-stable mode, with a relay between pin-3(Output) and ground. I will be using the relay to switch between two different LED arrays.

What concerns me is whether placing a relay directly between pin-3 and ground would cause a high current situation in the 555-timer.

Would it be necessary, and or possible, for me to put a resistor in series with the coil to limit current?

I’m just now getting experience with relays to, I know that they require a certain applied voltage to magnetize the coil to a point where it can effectively move the armature. I’m just not sure how this relates to KVL?

At the high state of pin-3 12V would be applied to the coil, I’m not quite sure, but I believe without a resistor, that would probably mean a lot of current would be sinked to pin-3. If I were to put a resistor in series with the coil of the relay, At high of pin-3, would the coil maintain the required voltage across it?


texts: Why should we use LED driver chips instead of much simpler structures?

texts:
For example: I have two led driver chips: bcr321u and RT8474AGSP

And think they both support to same output voltage and same output current etc. My question is about topological differences of them. BCR321U is definetely looks simpler and it is cheaper.

So, why do I need to use RT8474AGSP? When you consider, they both need much voltage supply and they both need an adjusted resistor for proper current flow, but RT8474AGSP configuration takes more area and so more and more expensive. In addition to that, this configuration is also an option:

If we were constrained by supply voltage, we would use boost led driver chips however, they all are buck structured so why we should chose RT8474AGSP over bcr321u and bcr321u over this simple opamp - npn structure? Where does the value of RT8474AGSP lies?


texts: What determines the actual power consumption of writing to a microSD card?

texts:
I'm currently working a project that will feature writing data to a microSD card. Because my project will be battery powered with a 125mA power regulator, I'm concerned that my write operations will consume too much power.

The microSD standard spec document states that a 25MHz write operation can have a maximum current draw of 100mA. This is somewhat concerning. However, my write operations at most will occur at 12MHz.

So my question, what exactly determines the power consumption of writing to a microSD card? I assume clock speed will effect it, would this relationship be linear? Regardless, assuming I were to write at 25MHz per the spec, is this 100mA simply a limit? Would write operations actually be less than this?

Is power consumption dependent on specific manufacturer implementation? A lot of microSD card datasheets don't list specific power consumption...

I appreciate any help!


texts: First PIC Program using PIC16F877A and its configuration bits for Internal clock?

texts:
I have a PIC16F877A and I wrote a program in MPLAB X IDE to blink a LED.

This is my program :

#include <xc.h>
#define _XTAL_FREQ 6000000
void main()
{
    TRISB7 = 0;
   while(1)
   {
         RB7=1;
      __delay_ms(1000);
          RB7=0;
       __delay_ms(1000);
   }
}

I compiled it successfully, but when I load the hex file in PICKit2v2 , it show a warning as below :

And also when I tried to write that hex file on MCU, It show the below error :

So I reopened my project in MPLAB X IDE V2.26 and tried to add configuration data to my code, using the wizard in Windows --> PIC Memory view --> Configuration Bits
But when I click it, I see this below window on the bottom of screen :

Question 1 : Why most of memory is equal to 3FFF in the first and second image that I attached above? Does that mean my program is just about 6 byte? (The first six bytes are different)

Question 2 : The error that I received is about configuration bits? Or it is something else?!

Question 3 : Which one of this optioned must I select for internal clock? I don't want to use any external clock or crystal o RC.

Question 4 : What is the difference between htc.h and xc.h libraries? I some of example code in the internet I saw htc.h included in the above of program? What is it for? Which libraries is for delay() function?

Question 5 : Is the second line in my program mandatory (I mean #define _XTAL_FREQ 6000000) Does it for external crystal? or ...?

I am a brand new in PIC MCU's programming. Pleas shed any light on this issue for me and for future viewers.

Update :

I added configuration setting to my program :
Now this is my program :

/*
 * File:   newmain.c
 * Author: Amir Ebrahim
 *
 * Created on January 3, 2015, 1:42 PM
 */

#include <xc.h>
#define _XTAL_FREQ 12000000

#pragma config FOSC = HS        // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = ON        // Watchdog Timer Enable bit (WDT enabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON       // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = ON         // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3/PGM pin has PGM function; low-voltage programming enabled)
#pragma config CPD = OFF        // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF        // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)

void main()
{
    TRISB7 = 0;
   while(1)
   {
         RB7=1;
      __delay_ms(1000);
          RB7=0;
       __delay_ms(1000);
   }
}

When I load the hex file in PICKit2v2 I received successful load :

But when I want to write the file on the MCU, I receive the same previous error!

Why?! :(


texts: Adding audio-in port to plasma ball with built-in Microphone

texts:
I have a Plasma Ball with a built in microphone and would like to add another switch S1 and an audio-in port to the circuit J1.  How do I calculate the line attenuation R1 and R2 resistors?

My idea is to add another switch S1 so I can switch between using the internal Microphone MIC1 or use the audio-in from an external source J1.  Is this the best way to do this?

Some questions I have are:

1) Do I need to use a shielded wire for the microphone MIC1 when I move it or when I add the audio-in input J1?  I would like the plasma ball not to fry these components or the devices they are connected to.

2) Also how would I calculate the (resistors) R1 and R2 to limit the voltage that comes in from the audio-in jack? J1 my audio input would be around 343mV

See image of circuit board with built-in microphone circled in RED along with schematic of what I want to change / add to the circuit.

Link to circuit

I tried using the built in circuit builder to electronics stackexchange below but it was missing some objects

simulate this circuit – Schematic created using CircuitLab

Adaptor
Model YHGD-1200500
Input: 100-240v 50/60hz, 0.18A max
Output: 12V 500mA

Mic1 is a CZN-15E Omnidirectional Electret Condenser Microphone


texts:
I've got a low power application which will be powered from a Li coin cell.  I've achieved satisfactory sleeping current with my chosen MCU.

The application ADC IC however is a different matter: 900µA while inactive -- way too much for a coin cell application.

So I thought why not isolate the power to the ADC when it's not in use. Two ideas came to mind: a high-side FET on the ADC's Vdd or just connecting the ADC's Vdd (or Vss) pin to one of the MCU GPIO pins (assuming current is within the MCU's source/sink spec).

I assumed there would be plenty of articles, app notes etc discussing this idea, but I've yet to find anything on line. Before I start experimenting, can anyone point me to any relevant articles/app notes online? Or is it just a bad idea? and if so why?

(Ya, know most MCUs have ADCs built in. For reasons beyond the scope of the query, I really must use this external ADC IC.)

Thanks!


texts: LED-driver board with WS2818/WS2811 and PT4115

texts:
I want to develop a board with a WS2818 IC and three PT4115 as high current LED drivers. Input voltage shall be 12-18V. You can easily mount a Wemos D1 Mini ESP8266 board on the top edge, as the pins are in the right positions. The output current of the drivers can be selected by solder jumpers in a range between 330mA and 870mA.

I want to order the PCBs and parts at JLCPCB and LCSC, respectively, the design was made with EasyEDA.

Before ordering, I would like to know wether this design could work...

On the left side of the schematic are the three constant current sources based on the PT4115. The inductor has 75µH and 1.15A, which should be in the specified range for the selectable currents. In the datasheet of the PT4115 it says that the rated current should be 30% to 50% higher than the output current. At 870 mA, it is still a little bit above the specifed 30% buffer, at all other currents it is well above the 50% buffer.

The diode is a RB060M-60, as it has low reverse current and is rated at 2A.

The capacitor is a 10µF/25V ceramic, and an additional wired 100µF/25V electrolytic for each IC, which is not in the schematic, as it is directly soldered to the board.

The DIM pin of the PT4115 seems to be rather sensitive to over-voltage and ESD, so it is protected by an additional resistor and Z-diode.

The three current sense resistors have certain values, so that if you connect them in parallel with the solder jumpers, the specified currents are selected. these currents are 330mA, 500mA, 700mA and 870mA. The 0.3Ohm resistor is always connected.

On the right side of the schematic, there's the WS2818, basically a WS2811 with backup input.

The diode on the voltage supply of the WS2818 has a voltage drop of 0,7 Volts. This makes it possible to run the WS2818 directly with a 3.3V input (like the ESP8266). This trick is taken from Hackaday.
What I'm wondering: Is it still okay to have an input signal with a voltage of 5V. On one hand, it says the maximum voltage on the input pin is VDD+0.5V, and 5V pinut would be VDD+0.7V, on the other hand the WS2818 is specified for 5V pinut. So, can I mount the diode on every board, or should I put a solder jumper in parallel, in case you're having an 5V input (Arduino etc.)?

The PT4115 expects an active high signal on its DIM pin, whereas the WS2818 gives an active low output. For inverting and level shifting the signal, I took the circuit from the PixiFlood project.

The rest of the parts around the WS2818 are the parts recommended in its datasheet.

The three capacitors (2,2µF/25V) in parallel to the LEDs are there to reduce the ripple current, as recommended in the datasheet of the PT4115. I think this makes sense, as there may be a lot of boards on the same voltage supply, with rather long wires between them.

The LDO for the WS2818 is a Seaward SE8550, as it is small (SOT-23), cheap (4 Cents), takes input voltages up to 35V and delivers 250mA, which should be enough for WS2818 and ESP8266.

Next comes the PCB, about which I'd like to know wether it's okay like this.
I tried to get all parts on 30mm x 45mm, so I can order 60 boards with panelizing via JLCPCBs special offer (2*3*10).
I'm especially wondering about the current sense loop and if it's okay to share one part of it with the power supply loop, or if I should have individual traces?

The pads of the electrolytic caps are also the connections between the power supply rails of the back of the board and the LED drivers. The power supply rails on the back are as wide as possible.
The connections on the SW, 12V and GND pins of the PT4115 are made with copper fills to be as wide as possible, too.
The electrolytic caps are bent to 90 degrees and are mounted above the coils.

The LEDs themselves are mounted via cables, so you can easily mount them to a heatsink.

The DIM pin protection parts of the lowest PT4115 have a slightly different position. Otherwise they might collide with the mounting screws.

Will this layout work?


texts:
I'm trying to identify this 30 year old ø24mm 10k log potentiometer so that I can replace it.  The only marks on the rear are "RC-302" and "1348616" but that doesn't turn up anything in my searches so I'm looking for a modern equivalent.

What's the right name for this pin configuration, where the pins are reversed such that the shaft of the pot goes back through the PCB to which it's soldered?

(If I search for "reverse" I just get links pointing me to log pots with a reverse log taper).


texts: How to read and source capacitors on a xbox one x motherboard?

texts: I found out that one of the capacitors on my xbox one x motherboard is blown. I'm totally new to reading capcitors. How do I read these and when sourcing them are they all the same even if the colors are different?


texts: Dynamic resistance of a p-n junction diode

texts: The slope of the graph between current and voltage in a p-n junction diode, under both forward bias and under reverse bias, varies a lot on varying the voltage. Hence, given the graph, how do we decide which two points to take to calculate ΔV and ΔI in order to find \$r=ΔV/ΔI\$?


texts:
This is a front end circuit for capture signal. The signal's highest frenquency is 20 MHz.
Why place a  "Polygon Pour Cutout" area in PCB?


texts: What notation is this? (Boolean/Logic Function)

texts:
I've come across these questions. What notation is being used in the 2nd and 3rd question?

Thanks


texts: Finding current when short-circuiting the terminals

texts:
I am working with the circuit shown below.

I am having trouble with the situation where: if a short circuit is connected between Terminals A and B. what current would flow through the short circuit in the direction, A to B?

I am confused about this question. I thought that is would be 2.7 x 10^-3 A (from the current source), however, this is incorrect.

From this circuit, I have also found that the open circuit voltage (VAB) when V1 is acting alone is 2.92V. And that the open circuit voltage when I3 is acting alone is 9.45V. Open circuit voltage when both sources are acting is 12.4V. And finally, I calculated that the Thevenin resistance between A and B is 3.50E+3. (These answers are approximate, as I was asked to give them to 3SF.) I am not sure if these previous calculations help to answering the question that I am confused about.

I would appreciate it a lot if you could please explain this to me.

Thank you very much for you time and help.


texts:
I am trying to use an integrating op-amp. What I want to do is apply + 0.5 V for 40 us and afterwards apply -1 V for 20 us.

Since the integration sum over one period is zero,  thus if my reasoning is correct the DC offset should be zero as the capacitor is not storing charge over one period.

However, in the simulation the result is different.

What is the conceptual mistake I am making?


texts:
I've been attempting to get this 4-pin brushless dc pc fan working for some time now.
It has a red (+) black (-) blue (PWM in) and yellow (tachometer out).

I only want this fan running at maximum speed and I have seen people run these, like in this video without the PWM blue wire. However, they are still using the tachometer output, which I think it unrelated... I still cannot get it working.

I think I've tried any combination of wires connected to either + or ground.

Any ideas?


texts: What is the function of the capacitor between ground and 12V?

texts: This is a switching circuit used for a switched reluctance motor. In this circuit there is a 47μF capacitor on the right side. What is the capacitors function in this circuit?


texts: I`ve just got a 1.5-9V motor and I know nothing else. I'm using a 9V battery but I want to know how to change the resistance to slow it down but I have no ways of finding the current flowing through the simple circuit. Help please.


texts:
I am trying to interface the Ethenet using RMII at 100 Mbps speed.

The main board is a RH850 F1 evaluation board. Ethernet RMII transciever is a DP83848 chip on a waveshare External Transciever Board

The two boards are connected using an unshielded ribbon connector.

The Management signals are working after adding the pull up of 1.5k at MDIO pin. I am reading the PHYID correctly and also able to set the BMCR.

However the actual packets received on wireshark is corrupted. Even the MAC ID and Ethernet Type fields are being received corrupted.

I have the following questions from a hardware perspective.

Is it even possible to connect with RMII using a ribbon cable? Has anybody else done this?

a. I ask this as the RMII uses a 50 Mhz clock and I want to know If I can send these signals across a 6 inch ribbon cable.
Do I need to add termination resistors to the OSCIN, RxD_0, Rx_D1, TxD_0, TxD_1 signals? Adding these very close to the microcontroller or transceiver is not easy.
Any other suggestion as to how to get this to work.

Edit: Added photo of board and cable.


texts: What do you mean Gear box in Serdes serializer?

texts: I read a statement from a document on Serializer. It mentions no gearbox Serializer.  Do you know what it meant?


texts: My research has indicated that failure in LED lighting (incandescent replacements) results from failure in the support components rather than the actual LEDS themselves.  How can I build and/or modify my final set of lights such that they will fail after I am dead.  (I'm 40 and very healthy.)


texts:
I am reviewing a 6 layer board that has analog signals on the left and right side of the board.

I have always read that analog circuitry should be grouped together for easy plane segmentation. However in the real world that is not always possible, such as this case...

The image labels, in text, where the analog circuitry, power circuitry, and star grounding point are. The star grounding point is where the the Vin/GND terminal block is.

The layer shown is the internal ground plane, with the darker green area being the analog plane and the whiter/lighter green area being the digital ground. All of the analog input traces are covered by the AGND plane area.

Is this is valid grounding scheme if the bottom layer is a complete digital ground pour?

Technically I know the grounding for analog and digital should be on the adjacent layer to the signals, but this is a basic relay output and analog input (8 bit) board and not high speed.


texts: Calculating Wattage for Gate Resistor for IRFP460 MOSFET used in High Frequency [400KHz] Application?

texts:
I am making a MOSFET driving circuit.
Frequency : 400 kHz  [50% duty cycle]
Gate voltage: 12 V
Total gate charge : 210 nC as per datasheet IRFP460
Rise time: 100 ns
[Q=I*t]
Current: 2.1 A
Gate resistor: V/I > 12/2.1 > 5.7 ohm
Peak power: I * I * R > 2.1 * 2.1 * 5.7 > 25.1370 W

1 watt resistor is OK ?


texts:
I try to get a detailed understanding of the following circuit that is from here and is part of a radar motion detection circuit.

Is my assumption correct that the first LMC6484 is a frequency dependant inverting amplifier (with C1) and the diode D2 is limiting the negative drop of the feedback to 0.7V? What's the purpose of this diode?


texts: How do the cassette tape adapters get their energy

texts:
I was wondering where the cassette tape adaptors get their energy, looking at this image

http://car-mods.wonderhowto.com/how-to/hack-your-cars-cassette-deck-into-wireless-bluetooth-music-player-0139843/

there is clearly some electronics. I can't see any dynamo however. Is the energy harvested from the audio signal?

Edit:

As it seems I was too fast in searching for an image. Here is an other one

taken from : http://i23.photobucket.com/albums/b371/2wildthing/CassetteAdaptorInside2.jpg
which shows less of electronics. Maybe the system is all passive. I was somehow assuming that still some kind of conversion had to take place, even though the audio signal and the storage on the magnetic tape is analogue.

If you find better tags, feel free to add them.


texts: Are thermal effects on an FPGA different depending on how it is programmed/configured?

texts:
I am currently on the fence in a debate regarding FPGA environmental testing (thermal cycling).
The question is, can the same FPGA stressed to the same thermal limits yield different results depending on how it is configured/programmed?
For example, data rates, data corruption, etc.
With something like a microcontroller I would say that regardless of how it is programmed the hardware remains the same, so its thermal properties will remain the same. FPGAs are a bit of a grey area, because although the configuration is described in code (i.e. HDL), it is creating a configuration in hardware within the FPGA.
Thoughts and opinions welcome, but if you have any relevant research papers or articles that would be great.
Thanks
Edit: To add a bit of clarity, I will be more specific about the use case. The under test is a system control unit, where the main processor is an i.MX6 Arm CPU, with the main signal processing unit being an IGLOO2 FPGA. There are two builds of software available for it:

Test control software, designed to stress it for design proving activities, but serves no purpose in the real world.
Operational software, the software that will be shipped with the item

The argument is that because the environmental stress testing has been performed with the TCS there is a gap in our proving evidence because thermal cycling has not been performed using the software which it will be shipped with.
The testing is performed in an environmental chamber which cycles between -40C and +70C.
The counter argument is that the TCS is inherently designed to excessively stress the item, therefore the operational software should be fine.
The third argument thrown in to the mix is that regardless of the build of software, the hardware is the same, so the effects of external thermal stimuli should be the same.
Edit 2: Clearly I'm still struggling to explain myself. The product was designed internally but is being manufactured by a contractor in another country. The main qualification testing (environmental and EMC) is being performed by the contractor, however we are unable to ship them the 'real' software as it is restricted and cannot leave the country. With that in mind, we provided the contractor with technical requirements such as thermal environment, bus speeds, and a 'sanitized' functional requirements which were designed to be representative but without breaking restrictions. With this, they created their own software (a.k.a the TCS). The question I am asking is if the code is functionally representative but simply 'not the same' as the software that will ship with the product, then how much of a gap do we really have in our evidence?


texts: Strange I2C Behaviour on PIC and some doubts

texts:
I'm posting the Code here:

    //***************************************************
    void main(void)
    { TRISCbits.TRISC2=0;// configures it as Output
      OpenI2C(MASTER, SLEW_ON); // Initialize I2C module
      SSPADD = 9;               //400kHz Baud clock(9) @16MHz
                                 //100kHz Baud clock(39) @16MHz

    EEByteWrite(0xA0, 0x30, 0xA5);
    PORTCbits.RC2=1;

}

I happen to Burn this Code that i found on I2c App note and Tried to port the Code in to PIC18f.
Well when i burned the code.The SDA and SCL are showing Pulses with 8bits seen on SCL with the help of oscilloscope.Well the Transmission is supposed to End after a Byte Write Function but it shows pulses on both pins even after getting the Byte Write Function is done.

Well as far as from what i learned the I2cBus must be Idle after Writing Bytes!. Well I cross checked whether the ACKSTAT(ACKNOWLEDGEMENT STATUS IS  RECIEVING ) and found it recieving from the slave which is an eeprom chip.

Why is this Strange behavior happening on the I2C? Or is it that because of not so clarity in I2c concepts.


texts: Selecting DC Blocking Capacitors for GPS, LoRa

texts:
I am designing a transmitter and receiver part of LoRa and GPS. It requires DC Blocking capacitors. I was looking for capacitor over digikey and I am amazed most of the manufacturer haven't specified impedance vs frequency curve.

I am interested in RF capacitor which can be used as DC blocking capacitor and pass signal of 900 MHz (LoRa) and 1.5 GHz (GPS).

Even if very few manufacturer have specified the graph but it looks like they have SRF at around 200 MHz and I think they can't be used in my application. Should I ignore SRF and check impedance at my frequency of interest? I am clueless now how to select the capacitor for RF.

The ESR is also specified at 100 kHz or some other low frequency but I want to interpolate it to my frequency of interest. I came across one application note which states that

  If, for example, you are designing for a 900 MHz wireless application, and the ESR is specified at 150 MHz, the ESR at 900 MHz may be calculated by multiplying the specified ESR at 150 MHz by √ 900/150.

Is it correct? Can someone comment on what other parameters I should consider while selecting capacitor for RF application? I have mentioned few of the parameters below. Please someone validate my understanding.

Tolerance- I am looking for capacitor having less than 5% tolerance.
Voltage Rating: I am selecting caps having voltage double of my max RF signal voltage.
Quality Factor: I am looking for high Q.
ESR: I am interpolating ESR to my frequency of interest and trying to select the lowest ESR caps available on the digikey.


texts: Passives used in differential signal lines

texts:
My doubt pertains to the presence of passives in many differential links (say RS422, for eg).

Consider the schematic below -

In the above circuits , I see a capacitor in series with the differential lines. What is the purpose of this ? In many cases I see a resistor and capacitor in series. Resistor and capacitor in series.

Another common methodology is the one shown below -
.

It shows an RC and the junction between the caps being grounded. But, this is more like a single pole LPF to filter out high frequency components, right ?


texts: Why is it impossible to realize elliptic even-order filters with \$R_S = R_L \$?

texts:
Referring to RLC continuous-time prototypes of filters, I have read that an elliptic filter of even order can not have equal source and load termination resistances.

The trasfer function for such filters is

$$|H(j \omega)|^2 = \frac{1}{1 + \epsilon^2 R^2_n(\omega)}$$

which for \$n\$ even and \$\omega \to 0\$ is

$$|H(j 0)|^2 = \frac{1}{1 + \epsilon^2} \neq 1$$

for \$\epsilon > 0\$.

1) Why this circuit  with \$R_S = R_L\$ can't realize the above transfer function for \$\omega \to 0\$?

simulate this circuit – Schematic created using CircuitLab

2) Are there some modified types of elliptic filters of even order feasible with \$R_S = R_L\$?

If the answers would be too long, and you would like to post some link about these questions, I'll anyway appreciate it!


texts: So I have a 3W amp that I want to use, and I've been told that that means each speaker channel outputs 1.5W. If that's correct, I have my mind set on two 1.5W speakers, but I don't know if I need 4 ohm or 8 ohm speakers. I've been told that the ohms shouldn't matter, but I've been told by another that it is what determines volume range. The datasheet of the amp itself says 4 ohms, so should I match the speaker ohm rating with that? Obviously I want to have the widest volume range of the volume knob possible.


texts:
I wanted to play around with some of these addressable LED strips, so I bought one off Amazon.  It's a string of 300 LEDs, comes in a big spool:

The spool has the same connectors on both ends, a 3-prong that has power and control, and a 2-wire power:

I also got their controller - the SP501E.  It seemed like it was relatively popular, and figured I would play with it for a while and then get an Arduino or Raspberry PI and do my own thing:

The controller said it accepted 5-24V so I found a 12V adapter in the basement that had a plug of the right size.  I plugged it into the controller, plugged the controller into the LED strip using the 3-pin connector (leaving the bare wires dangling) and ... the LEDs lit up, not very enthusiastically and only about 1/3 of the way down the spool.  And although the minimal instructions said "Pressing and hold the button on the controller untill the LED flashes in white", I sat there holding that *!&% button for a couple of minutes and never got the white flashing.
These sounded like they could all by symptoms of insufficient power, so I decided to get a beefier power supply.  The package said 18 W/m, and the spool is 5m long, and it's running at 5V, that sounded like 18A to me.  I ended up ordering the Alitove 5V 60A Power Supply which is probably a little scanty if I end up with 3 strings of lights.  Who knows.
In any case, it comes with really no instructions, luckily they did include a picture on the web site of the connections:

So back to the basement I go.  I found an old power cord I could snip the end off and wire into the PSU, and sure enough I got a nice 5V out between +V and -V:

There's a variable resistor to control the output, so I'm sure I could tweak it down to exactly 5.0V.
But now I ran a question due to lack of documentation.  As I mentioned before, The LED spool has 2 connections - a 3-pin and 2-wires - and the controller plugs into the 3-pin, which leaves me with the 2 wires sticking out from the LED spool and the power connector for the controller.  I'm not really sure what I need to do here.
So I performed surgery on my 12V power adapter, cutting off the power block itself, just leaving the wire and the plug.  I then wired it into my 5V power supply, with ground on the outside of the plug:

So now I've got the same 5V supply feeding the LED strip directly, and the controller via its power jack.
That all seemed reasonable - a good amount of amperage available on my 5V supply, same 5V running into controller and LED spool, ready for liftoff.

The first time I try this, a few LEDs on the spool shine green - a nice solid color, power looks good - but holding the button on the controller does nothing.
The next time I try this, the LED spool ignores me completely.  Totally dark.  I am still getting 5V from the PSU.
Where did I go wrong?


texts: Generating 500 kHz sine wave using modified PWM

texts:
I am trying to generate 500 kHz sine wave of varying amplitude using full bridge transformer isolated DC/AC converter.

I decided to use a sine wave table to change the PWM duty cycle. More the values per cycle better the sine wave output. For 256 values per half sine wave, we need to update once every 3.9 ns which means MCU needs to run at 256 MHz rate at least.

Another constraint is that Mosfet driver needs to turn on/off the Mosfet really fast under 3.9 ns. Mosfet driver tc427 need at least 30 ns to turn on/off the MOSFET.

I am really confused on how to go about overcoming the constraints. Any suggestions please?


texts: I need to prototype something quickly as a proof of concept. Is it safe to use mains (UK 230V) on stripboard? It will be going to a transformer so I can control some appliance. Or should I design a custom PCB to do this?


texts: Transformerless rectification is giving out AC component

texts:
I want to convert 240V AC 50hz to 12V DC without transformer.I want the output (12V) to drive 25 white LEDs.The circuit is giving an output of ~14V DC.But the problem is that it is also giving out ~30V AC.Is it OK to use this for my task or is it harmful (for LED's).What should be done to eliminate the AC component?I even tried using an extra 1N4007 diode at the O/P but no use.
Following is the circuit diagram.

EDIT:
My Multimeter shows 0V AC for a 12V 1A power source.So that means my Multimeter is working fine.Is it not?


texts:
I'm a student living in the UK.

I have this great idea for a product that fills a niche market and it interests me. It's a powerful on screen display module with datalogging capabilities, and it's open source hardware and software. See http://code.google.com/p/super-osd/.

I want to start selling these modules. I have PCB designs and I'm ready to order the components, but what route should I take for manufacturing the modules? I see three main possibilities:

Etch my own PCBs and solder components on - pretty much a no go as I'm dealing with double sided surface mount boards.
Order PCBs cheap from China and solder all 40 odd (0603, TQFP44 etc.) components on myself. (Probably the cheapest option but lots of manual labour.)
Get a quote for PCB+assembly.

Any ideas?


texts: Why does my SPICE simulation have a different lambda value from my model files lambda value?

texts:
I'm currently running a few labs here on my own since my university cannot do them in person and I have a SPICE model file in which the lambda value is set for a transistor. When I run a DC sweep on the transistor between the drain and the source and plot the graph and use it to calculate the lambda value I end up with a small discrepancy (1.5e-2 in the model file vs 1.31e-2 in the hand calculation from the simulations DC Sweep results) but I cannot for the life of me work out why? Is it to do with whatever way the simulation converges on the values or is it a case of because I only use a small area of the saturation region to calculate the value the result is off by a bit?
Any help would be appreciated!
Schematic

Model
.SUBCKT CD4007N 1 2 3
M 1 2 3 3 CD4007N
.MODEL CD4007N NMOS(L=5u    W=20u
+VTO    = 1.77          Kp      = 2.169e-4      GAMMA   = 4.10
+PHI    = 0.65          LAMBDA  = 1.5e-2        CBD     = 20e-12
+IS      = 1e-15         PB      = 0.87
+CBS    = 2e-14         CGDO    = 88e-8         CGBO    = 0
+CJ     = 2e-10         MJ      = 0.5           CJSW    = 1e-9
+MJSW   = 0.33          JS      = 1e-8          TOX     = 1.265e-10)
.ENDS CD4007N


texts:
I’m in the process of designing a SMU for part of my senior project, and wanted to get a quick design review in before I did any layout for it. The SMU isn’t advanced in any regard; the only real goal is to force voltage, measure current, and force current measure voltage.

The specs are as follows:

System has a voltage range of ±10V
System has a current range of ±100mA
System is capable of delivering/absorbing a continuous power of 1W maximum
SMU has adjustable output level settings:

Minimum voltage setting resolution is 100mV with a minimum accuracy of ±10mV
Minimum current setting resolution is 1mA with a minimum accuracy of ±0.1mA

SMU has adjustable output limit settings:

Minimum voltage limit setting resolution is 100mV with an accuracy of ±10mV
Minimum current limit setting resolution is 1mA with a minimum accuracy of ±0.1mA

As far as the circuit goes, I found and tested a design I stitched together from two application notes.

http://www.ti.com/lit/an/sboa046/sboa046.pdf (pg 21, 22)

http://www.ti.com/lit/an/sboa052a/sboa052a.pdf

I simmed the circuit in LTSpice and it worked, so I put together a schematic and built it. Everything works fine, I was able to correlate perfectly with sim. OP633 ran hot when delivering 100mA but temp was less than boiling.

^LTSpice Sim

^Voltage Transfer Char with Load = 10kΩ (Voltage Config)

^Voltage Transfer Char with Load = 10Ω (Current Config)

^ LTSpice schematic and DC transfer char. Both the voltage and current configurations are shown, but in the actual design 2 analog muxes switch the connections to change modes.

^ kicad schematic

As far as questions go, I want to use a 0-5V DAC, and can gain that up to 0-10V no problem. The issue is for the voltage source, there is an error generated from the voltage divider of the shunt resistor and load resistor. Because my shunt is large (50Ω - it sets current output), this error is as large as 0.5% for a load of 10kΩ. To fix this, I can use the difference amplifier placed across the shunt resistor and simply account for the voltage drop using software feedback. The only issue is that I need to make the DAC output something like -1-11V (ish). I can cook up an amplifier to do this, but it gets slightly ugly, both hardware and software wise. Currently, a DAC value of 0V is max negative output voltage/current, DAC value of 2.5V is 0V / 0mA, and a DAC value of 5V is max positive output voltage/current. With the a -1-11V output, that nicely valued relationship disappears. Not the biggest deal in the world, but still kind of inconvenient.

Is there a better way to account for the drop while keeping the circuit simple? I want this to be a precision source so an error as large as 0.5% is too much. (9.95V verses 10V @ R_L = 10kΩ).

Besides bypass caps and a ground plane, are there any other layout concerns I should have? Input protection?

Any other large sources of error I can eliminate? I want to use both hardware and software in order to get very precise values. For 100mV/1mA steps, I have to change the DAC voltage by 50mV, which shouldn’t be a problem with a FSR of ~10V and a >12 bit-DAC.


texts: Alternative HLW8012 IC for 220v AC power meter in IOT power outlet

texts:
I would like to create a Power outlet IiT (220V 10A for home typical usages),so I am gathering the circuit which is needed on it. (all can see here)

One part of it is Under-voltage protection, so I decide to use this system:

For the moment, this is the current status of my circuit:

It needs to have some components changed because they cannot be found at my aria.

One of them is the HLW8012 based circuit:

The above circuit has a GND isolation problem also, but I would like to know what other ics, like the HLW8012, are suitable for the task and cheap. Or should I replace it with another 220v power meter circuit?

Thanks.


texts:
I get confused by the knee voltage and Vbe. Sometimes in circuit problem question gives me knee voltage is 0.5 V and sometimes other questions just tell it like Vbe = 0.5V.

Are they both the same?

Please explain.
This is a question that confused me most.
Given IB = 25mA, Vbb = 3V Knee Voltage = 0.5V.Find the dynamic resistance.How do I solve this question

simulate this circuit – Schematic created using CircuitLab

Knee Voltage = 0.5 V and β = 18


texts:
I have acquired high frequency current probes up to 5 GHZ. The current probes have a 50 ohm SMA-type output. The probe has a hole through its center where a conducting wire will be placed for measurement. I also have a signal generator up to 20 GHZthat I'd like to use for test. However i am not sure what the best test setup is. I was thinking to just create a simple series resistor circuit on a breadboard with an AC input. Am i completely on the wtong track ? what is the best way to test the functionality/performance of the probes?

Just for an idea, the probes I have are similar to the following:

http://www.vosssci.com/products/sensors/cp450/cp450probe.html


texts: Using C18 software I²C libraries, is there any smart way to set bus speed?

texts:
After encountering problems with hardware I²C as described here, I decided to try software I²C using MPLAB C18 compiler's library functions. Fortunately, the libraries do generate good-looking signal at the pins, but I'm a bit worried about the timings used by them.

The documentation and source files of the C18 compiler do not explicitly say for which bus speed and oscillator frequency the delays in functions are set, so I'm wondering if there's a better way to adjust them than diving through source files and calculating by hand the number of delays I need.


texts: Does modelsim support shift right arithmetic in verilog?

texts:
I am using ModelSim PE Student Edition, and I am trying to write a module which shifts right arithmetic. After searching online, and consulting a Verilog textbook, I found to shift right arithmetic I can use the ">>>" operator. However when I attempt to do so and simulate the module, it only does a regular shift ie if the msb is a 1, it doesn't copy 1's into the shifted places, instead it is putting 0's. Below is a sample of what I am doing.

module shifter(
input [31:0] shamt,
output reg [31:0] result
);

reg[31:0] temp;

always@(*)begin
   temp=32'hfff00fff;
   result[31:0]=temp[31:0]>>>shamt[4:0];
end

endmodule


texts: The GPIO External Interrupt doesn't work

texts:
I have written this program for GPIO External Interrupt but it doesn't work. look at the program:

/* Includes ------------------------------------------------------------------*/
#include "stm32f10x.h"

/* Private functions ---------------------------------------------------------*/

GPIO_InitTypeDef GPIO_InitStructure;
EXTI_InitTypeDef EXTI_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;

void GPIO_Configuration(void);
void EXTI_Configuration(void);
void NVIC_Configuration(void);

/*******************************************************************************
* Function Name  : main
* Description    : Main Programme
* Input          : None
* Output         : None
* Return         : None
* Attention      : None
*******************************************************************************/
int main(void)
{
    GPIO_Configuration();
    NVIC_Configuration();
    EXTI_Configuration();

    /* Infinite loop */
    while (1)
    {

  }
}

/*******************************************************************************
* Function Name  : GPIO_Configuration
* Description    : Configure GPIO Pin
* Input          : None
* Output         : None
* Return         : None
* Attention      : None
*******************************************************************************/
void GPIO_Configuration(void)
{
  RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOB , ENABLE);
/**
 *  LED1 -> PB0
 */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
  GPIO_Init(GPIOB, &GPIO_InitStructure);

    /* PB2-> Input */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
  GPIO_Init(GPIOB, &GPIO_InitStructure);

}

void EXTI_Configuration(void)
{

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);

  GPIO_EXTILineConfig(GPIO_PortSourceGPIOB, GPIO_PinSource2);
  EXTI_ClearITPendingBit(EXTI_Line2);

    EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
  EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;
  EXTI_InitStructure.EXTI_Line = EXTI_Line2;
  EXTI_InitStructure.EXTI_LineCmd = ENABLE;
  EXTI_Init(&EXTI_InitStructure);

}

void NVIC_Configuration(void)
{

  NVIC_InitStructure.NVIC_IRQChannel = EXTI2_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
}

void EXTI0_IRQHandler(void)
{
    if ( EXTI_GetITStatus(EXTI_Line2) != RESET ) {
        EXTI_ClearITPendingBit(EXTI_Line2);
      GPIO_SetBits(GPIOB , GPIO_Pin_0);
    }

}

#ifdef  USE_FULL_ASSERT

/**
  * @brief  Reports the name of the source file and the source line number
  *   where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t* file, uint32_t line)
{
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */

  /* Infinite loop */
  while (1)
  {
  }
}
#endif

/******************************************************************************************
      END FILE
******************************************************************************************/

and this my circuit:

I have even pulled-down the PB2 but doesn't work, again. the program correctly build and download (without any error or warning).

What's the problem? any idea?


texts: High dielectric strength temperature sensor (2500V)

texts:
I am trying to measure the temperature on a heatsink that is at Earth ground potential, while my circuit ground is at line potential.

Typically I would use something like the Microchip MCP9700 in a TO-92 package, but there is seemingly no way this could stand up to a 2500V hi-pot test.

I found one UL rated NTC thermistor, but it is very expensive ($10) and it is only rated to 600V. No dielectric breakdown data was listed in the datasheet.

What am I missing? Surely this is a very common thing to do.

Note: My MOSFETs are in a TO-220FP package, so they are bolted directly on to the heatsink.

Should I just ditch the FP MOSFETs, go to a TO-220 and just find a TO-220 NTC and use insulation pads for everything? Or is there a better approach?

This is not looking for product recommendations, rather examples of commonly implemented solutions to this problem.


texts:
I'm trying to figure out how to create a driver for a led from the GPIO pins of the raspberry and a NPN 2N3904 transistor. I am currently following what seems to be a good sparkfun tutorial. On this tutorial page is a video. So I tried to reproduce what is explained in this video (but English is not my native language) and here is what I understood at my level, it seems that there are several misunderstandings. I simulate the circuit in falstad:

First of all I would like to know if the value of 5mA (the sparkfun sir chosen 0.005A is 5mA) corresponds to the maximum value visible in the data sheet for Vbe (SAT):

  (IC=50 mAdc, IB=5.0 mAdc) = 0.95V

, but the sparkfun sir chose 0.6V (which he does not name Vbe(SAT) but 'drop voltage as a diode'? So can we say that IbMAX = Vbe(SAT)MAX = 0.5mA (I also keep in mind that the GPIO port of the RPi seems to give 16mA maximum current).
More specifically, does the highest notation for Ib in this form (IC=50 mAdc, IB=5.0 mAdc) in the data sheet actually define Ib MAX? So can we say 'drop voltage as a diode' = datasheet Vbe(SAT) ?
which would mean the part of my calculation based on the maximum current of the GPIO port is wrong in this case.

For Vce(Sat) the sparkfun sir uses 0.3V that is 300mV which seems to correspond to the style sheet: (IC = 50 mAdc, IB = 5.0 mAdc) = 0.3V, but falstad displays 110.163mV ?

The LED used is noted 3.0V, 100mA so I deduce 3@0.1A
Now if we observe Ic its value is 191mA: 191mA < 100mA? FALSE ! So for me the LED is burning. Knowing that he chose a resistance of 330 Ohms in the end for Ib, that means that there is even a little more intensity which is worse. (unless this person specifies at a given time that it really depends on LED used and that I did not understand).

I want to create a program that can find Rc and Rb automatically and make the most of transistor and LED power. I also wish that this program indicates according to the limits of the LED , transistor, GPIO max current, Vcc used and their characteristics any possible errors.

I saw some people do a calculation for Rb with a factor of 10 to make sure the saturation mode of the transistor (Rb = (Vgpio-Vth) / (10 * (Ic / Beta)) if I remember), here the calculation is a little different for sparkfun (Vgpio-Vth / Ib) where Ib come from ? have a limit ? etc... but the transistor goes into saturation mode too.

Thank you for your help and your time.


texts: Importance of phase angles when analysing AC circuit

texts:
Freshmen EE circuit. Resistance, inductivity, capacitance are given and effective value of voltage. No phase angles are given.

When calculating complex power, may I assume the phase angle of the voltage source? Current should adjust accordingly and give me the same power no matter which angle I assume.

Am I right? (I know there are formulas with effective U)


texts: Can high audio input level cause video loss or video distortion in camcorder?

texts:
Today I met with a vendor regarding the installation of a PA system at our facility. We currently record meetings with a handheld camcorder mounted on a tripod, and we're looking to add microphones in order to feed a clearer signal into the camcorder's audio-in jack directly from the mixer board.

This guy is supposed to know audio equipment, and at first he seemed knowledgeable until he made one statement that left me confused:  he said that if we input an audio signal that is too high into our camcorder, the camcorder will stop recording video (i.e. the video will be either distorted or blanked out) until the audio levels are correctly adjusted.

Short of actually zapping circuitry inside the camera with an exceedingly high voltage and causing it to stop working, what on Earth is he talking about??? How could a high audio level affect the recorded video feed in any way?

Note also that he had no idea which camcorder we use because I never told or showed it to him. He was speaking in generic terms and applying this statement to all camcorders.

After he said this, I started seriously questioning if anything else he'd said could be taken seriously.

Any light to be shed on this?


texts:
In the STM32F469-Disco schematics, the MT48LC4M32B2B5-6A is used, which features a 4M x32 (=1Meg x 32 x 4 banks) arrangement for a total of 128Mbits. Now I was wondering if I could attach a IS42S32160F to it, which features 512Mbits of memory in an 16M x 32 (=4Meg x 32 x 4 banks) configuration.
The IS42S32160F has the same A[0:12], D[0:31] and control signals as the MT48LC4M32B2B5-6A.

Can I use the IS42S32160F, obviously with it's full memory range?

During my search I came across this presentation, showing the FMC in a very abstract manner. On page 5 it shows that MCU Bank 1 can use a 64M x 4 configuration.

Does that mean that I can use a single 1Gbit memory chip (64M x 32 x 4), or even two 1Gbit (64M x 32 x 4) memory chips, seperated by CS signals?
If yes, which signal needs to be routed to the CS pin of each chip?
As an extention of the question above, is this also true for the IS42S32160F if we replace the Gbit chip with one of these?

I want to use this ram to later boot Linux from it.
I did found this question on the site, but I can't seem to fit the answer into my questions.


texts:
I am using an STM32F0 to communicate with an SD card over SPI. However, when I send CMD0 after performing the required initialization, the SD card does not respond with anything on MISO. What's strange is that, originally, there was some response, but then I took out the SD card temporarily, and there's no longer any response. I have verified the card still works using a laptop, and I have also tried another SD card (both 32 GB). I am using this Adafruit breakout board, and I have a pullup resistor from MISO to 3.3 V. The following routine is what I use for initialization.

int sd_init(void) {
    int res;

    _spi_init();
    _pulse();
    res = _spi_sendCommand(0, 0);
    if (res != 0x01) {
        ui_writeFormat(1, "%d", res);
        return SD_INIT_FAIL;
    }

    return SD_OKAY;
}

static void _pulse(void) {
    int i;

    //send at least 74 (80) clock pulses following power on
    //NSS remains high
    for (i = 0; i < 10; i++) {
        _spi_sendByte(0xFF);
    }
}

static uint8_t _spi_sendCommand(uint8_t idx, uint32_t arg) {
    uint8_t resp;

    _spi_sendByte(0xFF); //these are optional, tried using them after finding them online
    CLR_CS;
    _spi_sendByte(0xFF);

    _spi_sendByte(idx | 0x40); //send index, prefixed with '01'
    _spi_sendWord(arg); //send argument
    if (idx == 0) {
        _spi_sendByte(0x95);
    } else {
        _spi_sendByte(0x00); //send CRC (N/A)
    }
    while (!(SPI2->SR & SPI_SR_RXNE)); //wait for byte to be received
    resp = (uint8_t)SPI2->DR;

    _spi_sendByte(0xFF);
    SET_CS;
    _spi_sendByte(0xFF);

    return resp;
}

I believe I'm performing the initialization procedure correctly, but I can't get it to work at all. My SPI clock phase and polarity are both 0 (rising edge, active high), although I also tried switching those. My baud rate is 375 kHz, but I also tried lower ones. I am using an oscilloscope to verify that I am not receiving anything, and it shows MISO as always high (due to the pullup). I've tried repeating CMD0 ad infinitum with no success. I am using the 5 V rail on the STM32F0DISCOVERY board as power for the SD, stepped down to 3.3 V on the breakout; I think this should provide sufficient current, although I could be wrong. Can anyone see what exactly I'm missing here?


texts: Hotel keycard switches on 5,000W load when placed in its holder. How does it do that?

texts:
In the hotel room I'm staying, I have to place the keycard in a holder by the door to power up all the electrical applliances in the room. Once turned on by the keycard, the circuit is powering the ar-conditioning, lights, power outlets, hair drier, switching a load of up to about 5,000W.

What electronic device (transistor, triac, scr, relay) is swiching such a large AC load?


texts:
There is a STM32 device which has to detect several signals from other devices. The voltage of these signals can be 12V or 24V. Also these signals can be positive (i.e. 12/24V) or negative (connected to GND).

simulate this circuit – Schematic created using CircuitLab

First question: Does it possible to allow TLP280-4 optocoupler work with 12V and 24V input signals? Or I should use voltage divider wit unique resistor values for each case?

Second question: On some board I see the R2 resistor. What does it do there?

Third question: What is the right scheme to connect STM32 controller to an optocoupler output to allow the controller to detect signals? Is mine good?


texts: Effect of hole conc while doping with donor

texts: Recently i saw a lecture on YouTube there it said that the hole conc is affected by the donor atom and The fermi energy of hole changes due to doping... But since the donor impurity is immobile it cant be counted as a hole(Right?) then how it changes the conc of holes?


texts: Frequency of astable multivibrator built with inverters (NOT gates)

texts:
I've assembled the following astable multivibrator (a.k.a. astable oscillator) circuit:

It generates a square wave (as expected), but the output frequency isn't predicted well by the formulae that I've come across for this circuit.

For example, this circuit appears in Figure 5.30 of The Art of Electronics and its frequency is said to be approximately \$\frac{1}{RC}\$ (presumably \$R\$ is meant to be \$R_2\$, although I suppose it could be the total resistance of \$R_1\$ and \$R_2\$ in parallel) when \$R_1\$ is approximately \$10R_2\$. The same circuit (albeit using NAND gates configured to act as inverters rather than actual NOT gates, not that this should affect the result) appears on this site under the heading "NAND Gate Astable Multivibrators", where its frequency is given as \$\frac{1}{2.2R_2C}\$. No derivation is offered in either case.

How might I go about deriving the output frequency myself? I assume some form of RC circuit analysis involving a differential equation would work, but given the indirect means by which the circuit is powered (namely, though the NOT gates) I'm unsure of how to set up an equation for capacitor voltage as a function of source voltage for this circuit (assuming this is the correct way to proceed).

Any suggestions would be appreciated!


texts: ATmega crystal setup and and power routing

texts:
I have finished designing my first circuit boards and am uncertain about a couple of things. First of all, I know that I should connect both sets of ground pins and +voltage pins on the chip. My question is is the way I have connected them on my two boards ok or was it unnecessary to have two separate cable runs for each one. Shall I just send one power cable to them and link them together.

My second question regards the layout of the crystals. Originally I had them laid out like in the first circuit (Backpack Board). But I am not sure if this is the correct way to do it. I then changed them to the layout in my second circuit(Utility Board). I believe this is the way Atmel suggest laying them out. It has a solid ground plane on the second layer. They are two layer boards. Should the ground plane below the crystals ground area be separated from the rest of the ground plane or not? And should I link it with vias? I'm not sure if it should be made separately as I don't want to create a ground loop in the ground plane. The board is going to be used near an RF module so I want to make it as rock solid as possible.

Thanks in advance for any help.


texts:
I need to connect a sensor with a 4-20 mA loop to a microcontroller.
The MCU operates at 3.3V and the following image is from the sensor's datasheet.

I'm planning on converting the 4-20mA to a 0.6-3V range to be measured with the internal ADC.
I'm trying to figure out if the setup would work if I power the sensor via a 12V boost.
From what I understand it should be ok as the drops would be 3V (in case of max output) + 6V required for the sensor's operation or if just providing 6V would be enough?
UPDATE
Adding sensor's datasheet
https://www.calex.co.uk/site/wp-content/uploads/2015/07/pyrocouple-infrared-temperature-sensor-data-sheet.pdf


texts:
I calculated the Thèvenin equivalent circuit of a given circuit in two ways. I know that one is correct and the other is not (because I saw the result on my book), but I can't figure out why the other is wrong.

This is the starting circuit:

simulate this circuit – Schematic created using CircuitLab

First way :

\$V_{eq}=V_1\cdot\frac{2R}{2R+2R}=\frac{V_1}{2}\$. (this gives the right solution).

\$R_{eq}=2R||2R=R\$

simulate this circuit

Second way: I see the starting circuit as this:

simulate this circuit

That is with an infinite resistance in place of the open circuit.
Now, I get:

\$V_{eq}=V_1+V_1\cdot\frac{2R}{2R+2R}=...=V_1\cdot\frac{3}{2}\$

\$R_{eq}=(R+2R)||2R=...=\frac{6}{5}\$

So,the equivalent Thèvenin circuit now is:

simulate this circuit

Where am I wrong with the second method?

EDIT:

When I calculate \$V_{eq}\$ with the 2nd method, I get this circuit:

simulate this circuit

And here it's true that:

\$V_{eq}=V_1\cdot\frac{2R}{2R+2R}=\frac{V_1}{2}\$

but it's also true that, with KVL:

\$V_{eq}=V_1+V_1\cdot\frac{2R}{2R+2R}=...=V_1\cdot\frac{3}{2}\$.

Where am I wrong with this last one?