texts:
I'm working on a project in which LED lights synchronise with audio events. I'm not referring to reactive LED projects that read the ADC from audio amplitude or spectrum, but about having some additional digital data playing along with the audio to indicate several triggers of events.

Initially, the approach I'm taking is that of utilising a stereo file and having a channel for audio and another channel for data. The file is accessed by an SD card module and processed by a codec or mp3 player module. The channel with data has pulses of different sine wave frequencies to indicate different events and trigger specific LED lights.

I managed to do this using a spectrum analyser chip, but it's not the ideal as by using the ADC there are fluctuations, and changes in the volume control affect the signal. I'm hoping to find a digital signal solution, as when the SD card is read and the audio processed, the data from one channel of the file (wav or mp3) must be read real-time in the MCU.

Ideally the MCU would be an ESP32. I experimented with some libraries that can read wav files from an SD card (such as esp32_I2S_player) but I couldn't manage to receive the data for creating the necessary 'if conditions'. Another try was to see if I could do this with a VS1053 codec, but libraries for this chip also don't provide a function to read data off the SD card of a specific channel, and I couldn't find much about this in the datasheet.

So my questions are:

Is there an efficient way for synchronising audio events real-time with LEDs using an MCU? I know how to do this through general Operating System sofware, but now the application requires a bare machine.
If my approach (stereo file = data + audio) makes sense, how can I implement this? Is there a codec or MCU that facilitates this approach? Is there any code example that can help me?

I'm feeling stagnated in this issue so I really appreciate your answers. Thanks.


texts: Why are quasi neutral regions in a PN junction are called "quasi neutral"?

texts:
When  the PN junction is in equilibrium ,the region away from the depletion region is neutral . Now when a bias is applied say forward , then we refer these regions as "quasi neutral ".But why? What results in this small deviation from perfect neutrality ? In analysis of forward I-V characteristics ,

Neutrality is still maintained as shown  in the image. Then why do we get quasi-neutrality ?


texts: First PCB project design critique requested (RF) EDITED

texts:
This is my first ever RF PCB project and it'd be great to receive some guidance to make this project 'first-time-right'.

It's purpose is to transmit and receive signals at two different frequencies: 125khz and 315Mhz. To transmit and receive 315Mhz signals I used CC1101 chip modules and for 125Khz I used EM4095 chip IC. I am trying to implement 2-layer PCB due to lower costs compared to 4-layer PCB. I tried keeping top-layer for DC power lines and connections between ICs, while using bottom-layer for GND, although I was forced to route connections between CC1101 modules and ATMEGA via bottom-layer. This is my first PCB project and I'd like to make it 'first-time right', so any suggestions are welcomed! What did I do wrong and what should be improved? Here's project editor page: https://easyeda.com/editor#id=|cae05dd5d4744d7285097ac5ad078f11|a4b1ecae88b340f59224d628c10a1dfd

EDIT: I have encounted GND routing issues with few components on this PCB, which I fixed by adding solid copper plane to the board and those components seemed to connect with GND. Hovewer this didn't resolve grounding issues for CC1101 components, footprints for which I created myself: U10, U9 and U11. Anyone could offer advice with that? Cheers.


texts:
Trying to figure out how the BJTs would affect the following circuit:

I'm confused overall, but some specific questions include:

If the input is off, the first transistor is effectively off, and VC1 = VB2 ~=12V. This sets the gate of the second transistor to be on/saturated (as the 0.7V needed across VBE2 is present). But how does this affect the output?
Does the voltage divider of the 30k and the 5k force 1.71V at all times on the output, regardless of the input?

Thanks for any/all help and clarification!


texts: Is DC-to-DC (24 V to 12 V) buck conversion typically more efficient than AC-to-DC (110 V to 12 V) conversion?

texts:
While building an online UPS system, I'm basing the choice to eliminate as many AC inverters from the system as possible because of the assumption that DC-to-DC conversion is more efficient than AC-to-DC conversion.

I'm not totally sure that this is the case though. I've read some articles stating that buck conversion might only be 85% efficient, yet many product offerings tout 97% efficiency. Also, one of the big selling points on AC is the efficiency of conversion. I am hoping to get some solid information on this specific efficiency comparison.


texts:
In a problem related to transformer loss I have found a line "AT/cm for a flux density of 1.2 Wb/m^2 in iron to be 5"

I've searched in google for 30 minutes about what is AT and how it is related to transformer losses and found nothing.


texts: External Current Sourcing Sensor parallel to PNP BJT

texts:
I have Biased the transistor Q1 in active region  as shown in the following diagram. I have Sensor which outputs 1-10ma and needs to be connected  across parallel as per the following diagram.
the transistor is biased in such way that for 1-3mA of sensor output  it remains in active region and for 3-10 mA it switches to Saturation region.
Now how do i calculate the current I2, I3 and I4 theoretically ?

Current without the Connection of external sensor I4=  864uA , I2= 72.208uA
 I4/I2(Ratio)= 11.96

Current With external Current sensor for 10 mA source : 10/11.96= 0.8361uA
So I2'= (72.208 + 0.863 ) uA and I4'= [864 + (10-08361) ] uA

This calculation is not precise  and slightly vary from the simulated results .
Kindly Suggest me theoretical Approach to solve this for mentioned Currents. will there by any current flowing  inside 15 V source from the external sensor ?

Thanks


texts: Reading GPIO configuration (Cortex M4 ATSAME54)

texts:
I'm writing some diagnostics for a Cortex-M4 -- in this case an ATSAME54.  I'd like to be able to read the configuration of individual GPIO pins, namely:

bool level
enum gpio_direction direction [IN, OUT, OFF]
enum gpio_pull_mode pull_mode [UP, DOWN, NONE]

I've figured out how to read the level and the pull mode, but I'm stumped on reading the direction.

Has someone out there solved how to do this?


texts: rc circuit for delay to charge android phone

texts:
I have made this circuit such that once switched on it takes about 7 seconds to get to 5Vs. I want to connect my phone to it (replace voltmeter in circuit with phone). Without the phone being connected it shows 5V, as soon as i connect my phone, the voltage drops significantly across the resistors and phone does not charge. What do i need to change so that my phone will start charging after a few seconds when the capacitor charges up to optimum voltage?

Really appreciate all the help. Please let me know if any more information is required.


texts:
I am trying to derive the input impedance for the transresistance amplifier (shunt feedback) on page 119 in the Art of Electronics.

I am considering a voltage \$v_i\$ applied to the input. As described in the book, it is the normal input impedance \$R_i\$ in parallel with something else due to feedback. When  \$v_i\$ is applied, it causes a current
$$I=v_i(1-A)/(R_f+R_o)$$
to flow from the input (so there is really current flowing into the input with A>1).
So shouldn’t the parallel part of the input impedance be
$$v_i/I=(R_f+R_o)/(1-A)$$
rather than what is shown in the image? This is a negative impedance in parallel with \$R_i\$.


texts: I'm not an engineer professionally but I'm interested in. So my question is, how to recognise the wattage of a resister? And how to measure it using multimeter?


texts: Linear Circuit Analysis: Source Transformation

texts:
* source transformation is just a combining and rearranging voltage or current sources. I don't think its a universal term.

and I'm stuck. any hint?


texts:
How does a coaxial cable carry RF, audio and low freq. signals? I understand there must be a difference between all these, for example the return path being through the shield or not.

Can someone explain what happens in each case of the 3 types of signals? In general terms, how the shield is used, etc.


texts: A question about reactive power through a capacitor in LTspice

texts:
Before posing the question I would like to write the assumption I make for the power concept in passive circuits. As far as I know the power dissipated in an RLC circuit is the active power which is actually only dissipated through the resistor R. Power through L and C components are associated with reactive power which means they in average do not dissipate power, they absorb and give back the energy to the circuit continuously.

If the above is true, then I assume a simulation should indicate the average power through an inductor or a capacitor as zero.

Here is a simulation for inductor case  where the input is a periodic pulse (plot shows the power through the inductor):

It seems the integral of the above plot with time is zero.

But below in capacitor case I don't get the expected plot:

In this case the integral of the above power plot with time is non-zero. And it is increasing.

Why in the capacitor case the average power is non-zero unlike in inductor case in this LTspice simulation?

EDIT: Below is the input signal asked as request:

Here are the settings:

Edit 2: Here in case of sine input:

Edit 3:

Capacitor power from beginning to steady state (source is pulse again):

And a zoom section from the steady-state:

And here below the capacitor power in mW(blue line) and its integral(green line) for the first 500 sec:

As you see the integral goes to a constant which indicates the capacitor does not suck energy anymore from the circuit after certain amount of seconds.

Is the energy at the beginning called as dissipated or stored? In other words is the power at the beginning active or reactive?


texts: Increase Microcontroller frequency and Speed

texts:
I am in process of upgrading the micro-controller of our project from Renesas M16C to RX63N. In our current M16C project we use 16HMz crystal. If in the new micro-controller Rx63N if I use the frequency to 196MHz using PLL, what are the points I need to consider specially in the code.

One thing I understand is the delay function used in the code may need to change according to our new instruction execution time.

Do I required to change or need focus on any other thing i.e. do I need to change anything in the serial communication between my new micro-controller and the external IC.

Do I need to change in my ADC logic? DO I need to change in my logic where I communicate to PC through RS232 chip?

Please guide me which area in my code, I need to give attention when I increase frequency and speed of the micro-controller.


texts:
Trying to make an adjustable current source floating on high potential.

Can someone explain why the driving logic should not be also on high potential?

I saw only the variants with minimum parts floating on HV. Driving signals for FET and analog feedback and faulty signal were via optic fiber.

What are the risks or benefits in comparison with having all driving logic floating and only one optic fiber for digital current adjustment?


texts: What is the purpose of the zener diode in this circuit?

texts:
Related: What is the purpose of the resistor on this MOSFET's drain?

This is a circuit taken from a TI reference design (http://www.ti.com/lit/df/tidr687/tidr687.pdf) to drive an LED matrix - it is used to switch on each row of the display in succession. The loads (the LEDs, driven by a current-sink driver), are attached at L15/L16.

From the related question, I can see the point of the 100 ohm resistor, but what benefit does the zener add?


texts:
I am Using an NET-35B SMPS from Meanwell to power a strain gauge type pressure sensor. I am using 24 bit ADC to obtain the output of the sensor.
I am getting Fluctuations and I think that those fluctuations are induced by power supply noise (Ripple= 80mV p-p).
I want to reduce the noise from power supply using a filter.

Questions :
1)How should I design a filter for above-given specs?

2)I have tried adding capacitors(Random)previously and it works, but I want to know how it exactly works and how precise filter can be designed ?


texts: Voltage Sequence in Three Phase System from wattmeter reading

texts: How does one identify the phase sequence of voltages in a balanced 3 phase system solely from the readings of two wattmeters connected properly to measure total power? I am referring to the two wattmeter method and the relevance of sequence in it.


texts: Not getting the absolute voltage output from the op-amp absolute value amplifier circuit?

texts:
I have a circuit that outputs a voltage of -10V to +10V. Then I needed to get all values as positive output voltages from 0V to 10V i.e. I absolute the negative voltage outputs.So, I searched online and got a an "op-amp absolute value amplifier circuit with one diode" from the following links:

Circuit Details : http://www.cirvirlab.com/index.php/tutorials/77-op-amp-absolute-value-amplifier-with-one-diode.html

Circuit Simulation : http://www.cirvirlab.com/simulation/op_amp_abs_value_ampl_with_one_diode_online.php

So, I rigged up the circuit as shown in the figure with the following components and values:

Op-amps - OP177 (Analog Devices)
R1 = R2 = 1k
R3 = 2k
Vcc = +10V and -10V
Diode = IN4007

How I tested:

First I gave a Vin = 5V, for which I got around approx 2.2V output and as I varied the Vin from 5V to around 7V, the output varied from 2.2V to around 3.6V approx.

Then, second, I gave an input voltage, Vin = -5V, for which I got a very low negative output value of -0.8V.

The problem is, I am not getting the absolute output voltage and getting lower output voltages compared to Vin.

I have attached an image of the circuit digram and IC. Please help me figure out what I am doing wrong, is it with the component values? or anything else.Thanks in advance.


texts:
I'm doing an activity and I need help.
So I'm practicing about shift registers...
The goal I want to achieve is I want to light up one by one in sequence all the 16 leds.

But what happens is the second set of 8 leds connected to the 2nd shift register is copying the sequence of the first set of 8 leds connected to the 1st shift register.

In other words, the result of the first 8 leds is also the result of the 2nd 8 leds.  It is mirroring. Why is this so? given that I connected the QS' of the first register to the D of the second shift register. I'm confused. Maybe a Proteus bug?

Anyways here's my code

unsigned char sequence[] = {1, 2, 4, 8, 16, 32, 64, 128};
unsigned char sequence2[]= {128, 256, 512, 1024, 2048, 4096, 8192, 16384}; //added

int latchPin = 8;  //Pin connected to STR(pin 1) of HEF4094
int clockPin = 12; //Pin connected to CP(pin 3) of HEF4094
int dataPin = 11;  //Pin connected to D(pin 2) of HEF4094

void setup() {

  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
}

void loop()
{
  for (int i = 0; i < 16; i++)
  { //added
        if(i<8){
           shiftOut(dataPin, clockPin, MSBFIRST, sequence[i]); //Send the data
           digitalWrite(latchPin, HIGH); //Pull latch HIGH to send data
         }
         else if (i>=8){
            shiftOut(dataPin, clockPin, MSBFIRST, sequence2[i]); //Send the data
          }
  }//added
}

and this my designed circuit.

Any help will be appreciated thanks!


texts: SMD Device and manufacturer ID markings S2

texts:
I have a SMD device that I am am trying to identify.

Can anyone point me to a manufacturer? Probably a resistor but I am not sure.
Any help would be appreciated.

The scale bar in the picture is not correct


texts: All possible BJT circuits relating to polarity

texts:
The BJT can operate in 4 different modes/zones since there are two voltages on it:

Active mode
Inverse/Reverse active mode
Saturation mode
Cut-off mode

Because Emitter and Collector junctions can be represented as diodes (with amplification) there are 4 different operating modes of BJT.

But do all of these modes apply for each of BJT orientation: Common Base, Common Emitter, Common Collector?

Are there 12 (3x4) different BJT circuits regarding to polarity of junctions and orientation of BJT?


texts: How much lead is really on my hands when soldering?

texts:
We have an electronic lab where we test and solder. There is a computer in the room as well. I have been wondering how much of that room is really contaminated with lead. We solder, go touch the oscillope or spectrum analyzer, google something here and there, open up all the drawers and what not etc. In my mind if were to visually see the lead in room I always think everything would be red. I rarely touch my phone while soldering or in the electronic lab but I've recently been doing so. When I follow what I touch when then going to the bathroom to wash my hands and then to my office, I think that lead is everywhere. I'm not talking crazy amounts just that it could be there. Sometimes I touch my keys etc. etc. etc.

So when one is dealing with lead solder, how much is really being transferred to other things when one touches their phone, a doorknob, the computer mouse/keyboard etc.? Or is it such a small amount that one shouldn't necessarily worry about it?

Edit: We use 60/40 solder. I still haven't seen an adequate/direct response to my question.


texts:
I'm etching a double sided circuit board for my project in electrical engineering but somehow the PCB gets these weird marks and turns out bad. I tried different things like washing the PCB before hand, being really careful not to touch it etc. but it still turns out like this. And it's usually one side.

The process I use is to have regular printer paper, front and back on two A4 pages then tape them together around the PCB. UV light for 300 seconds and then remove the film with NaOH. At this point the PCB looks OK but it gets these marks. I then wash it carefully in water before I etch it. I'm baffled what happens here, does anyone have a good answer for what I am doing wrong?

Edit: The problem occurs before etching. When applying NaOH the PCB gets weird marks that kind of resembles water drying on a surface. The UV light is  a dedicated machine with UV light tubes that is tested with these PCBs to work on 280-300s with normal paper at my university. It's highly unlikely this is the source of the issue.


texts: Voltage across open in this diode circuit with two batteries

texts:
Trying to understand how voltage \$ V_{D1} \$ is found.

Here's the original circuit with solution:

Here's how I think it can be redrawn, basically the grounds are just one node:

So to find voltage \$ V_{d1} \$ one first considers what's voltage at point 1, positive side of \$V_{d1}\$ right?

Well, at point 1, voltage is what? \$ -10K \times 1.33mA? \$

How about voltage across 5k resistor? Point 1 is between 10k and 5k resistors...

For point 2 it's 0, since the node of that point is connected to ground, right?


texts: Resistor between vcc and control signal in a rpi controlled relay board

texts: I have been researching to design a rpi controlled relay board and I found these two schematics from two companies. Personally I trust the company in the image above but I am confused about R3 (10k) and why they connect it to the control signal. What function does this resistance have? What happens when the control signal is HIGH? Would the circuit from above work? In the one below they don't use it, would it work too?


texts: Wireless transmission power for multiple receivers

texts:
I have just started learning about wireless systems and for some reason I'm hung up on what I feel is a fundamental idea.

Consider some transmitter-receiver pair with isotropic antennas. The receiver needs some minimum power (say, Pr), and knowing the transmit power (Pt) and the frequency, I can determine the maximum working distance R between the transmitter and the receiver via the path loss and link budget equations.

Now knowing R, I decide to set up two of the same receiver as before, each a distance R from the transmitter. Will my system still work, or does the transmit power Pt need to scale up with the number of receivers? What about for an arbitrarily large number of receivers?

I'm torn between thinking that the system couldn't possibly work because it does not seem to obey conservation of energy, and that it should work because the EM waves are radiating in all directions, so I was not "using" all of the power in the first place. Any clarifications would be welcome, especially if you can link sources. Thanks!


texts: Some advice on charging circuit used in simple UPS

texts:
I have looked around for some way of having a 5 volt power supply that acts like a UPS.

Basically want to use a micro usb connector for +5 have a battery and li-ion or other charging circuit that will maintain uninterrupted power on the output.

I found these 2 that are really what I need- but they charge Lead Acid batteries in cars or something and I do not know how to integrate a charging circuit into this.

6volt UPS with 6 volt input i think?

R1, R3 - 560 ohms 1/4W
R2 - 1 kilo ohms 1/4W
D1 - 1N4736A or any 6.8V zener diode
D2 - 1N4001 or similar diode
LED - red LED or any low power LED
C1 - 47uF electrolytic capacitor rated 16V
Q1 - 2N3440 or similar NPN transistor
BAT - 6V battery

5volt ups with 12volt input for lead acid battery charging

R1 - 39 ohms 1/2W
D1, D3, D4 - 1N4001 or similar diode
D2 - 13V zener rated 1W
C1 - 220uF electrolytic capacitor rated 25V
C2 - 10uF electrolytic capacitor rated 10V
IC - 7805 or similar 5V regulator
BAT - 12V lead acid battery rated 1.2Ah minimum
DC INPUT - 12volt DC

And i have found 2 charging solutions one for ni-cd and the other for Li-ion

Ni-Cd

R1 - 1.2 kilo ohms 1/4W
R2 - see R2 and D2 table below
R3 - 2 kilo ohms 1/4W
Q1 - TIP41C or any NPN transistor min 1A current and 3W power
Q2 - 2N2222, CS9013, or similar NPN transistor
LED1 - Red or any LED with forward voltage around 2V (see LED)
LED2 - yellow or any LED color except Red
D1 - 1N4001 or similar diode
D2 - see R2 and D2 table below
DC supply - 12V to 15V DC supply or battery

Li-Ion (nice single chip solution)

So I can connect the dots- the charging circuits require an input voltage and they are specifically picked to stop charging at certain currents to over over charge.

Would it be as simple as taking the + from the charging point and replace it with the BAT symbols in the UPS designs? I suspect I need to decouple it somehow, to prevent voltage from the always on power going to the + of the battery (and essentially bypassing the charging circuit) would a diode be needed here to stop the main supply (but how do I tell the battery to kick in when the mains is off?) Is there something missing here to switch between supplies as needed?


texts: Searching for a transformer for the power board of an Equipe 2400 studio blitz Power/controller

texts:
This is for a photographer friend, feel it would just be too bad to let this beautiful equpiment stay in the closet because of, as far as I can tell, one blown transformer. The unit is made by Bowens in the UK, model BW-2810, but is now obsolete, they will not fix it.

There was a bang from the unit when it went dead. And there are clear soot marks which seem to eminate from  the secondary side of the transformer, and no other visible marks or damage. The transformer sits close to the input 220V AC, but I do not know its specifications. See the images I have uploaded for details.

It has a label which reads (01993) 883214 L45 G3826/2 and on its plastic casing it is written E138x13.6mm , preceeded with a symbol possibly depicting an M and a P or D. Please see pics for details.
I would be extremely grateful for any leads tracking down the specs of this transformer, as well as, obviously, any pointers to where I could get a compatible one. I have tried searching for the above info with no results.


texts: Calculating the pulldown resistance for a given MOSFET's gate problem

texts:
According to this topic ,how to get this formula, I use RC circuit and can't get this formula

This is my answer, and I don't know where is wrong


texts:
What is the decay setting of a stepper driver?

According to TB6560 datasheet, it has decay setting like this.Explain differences.


texts: How would I design a simple logic circuit for 3 input bits?

texts:
All -

Suppose I have 3 input bits

Bit #0
Bit #1
Bit #2

I need to design a logic circuit has follows:

Input: Bit #0 = 1, Bit #1 = 1, Bit #2 = 0
Output: 0

Input: Bit #0 = 1, Bit #1 = 0, Bit #2 = 1
Output: 1

Input: Bit #0 = 0, Bit #1 = 1, Bit #2 = 0
Output: 1

Input: Bit #0 = 0, Bit #1 = 0, Bit #2 = 1
Output: 0

I know it's going to be a combination of XOR gates, but I'm not able to construct something that works for all 4 cases above.

Is there any software that can generate a simple logic circuit that satisfy the input/output conditions above?

I would appreciate all / any help.


texts: Advantages/Disadvantages of high/low transconductance efficiency (gm/Id) of NMOS/PMOS

texts: From here, it's said that a higher gm/Id results in lower current consumption (which is usually preferred in low power operation) But what other effects does a high gm/Id have? Will it have other advantages and/or does it also have its disadvantages? How about for low gm/Id? Will low gm/Id also have its advantages and disadvantages (aside from high current consumption)?


texts: Attiny85 crashes when I run a motor through an L293D

texts:
I'm trying to run a motor through an L293D turned on and off by an Attiny85. The Attiny85 has the micronucleus bootloader on it, which is why pin 3 is connected to a pull up resistor.

On the Attiny is a program that toggles PB0 on and off every second. I've attached an LED indicator on it, and while the motor is not connected to 1Y, it runs fine. It also works fine if I put an LED between 1Y and ground. But when I put a small motor between 1Y and ground, LED1 flashes briefly and then the Attiny resets.

Basically, how do I get it to not crash when running a motor through it?

I also tried the following, putting the motor directly on the power supply, doing so prevents the Attiny from starting at all.

Specs:

5V wall power supply with up to 3000mA output.
Motor pulls around 300 mA while active.
Also tried powering it through my computer's USB and got the same results.

What I've tried:

Replacing C2 with a 1000uF capacitor. That allowed me to plug the motor directly to the power supply with the Attiny85 running.
Putting the 1000uF capacitor between 1Y and gnd. No change.

Update 1:

The reason I was using L293D is because I didn't have any viable diodes at hand while testing. The only ones I had were too big to put on my breadboard. Connected it through alligator clips for now, and made the following changes, and that seems to be working quite well for now:


texts:
I built a timer for my water heater and have a question about spark suppression. I am using a 120v house timer 1875W to operate a Packard (240B) 2 pole 40A 120v coil relay. The output of the relay contacts are connected to 240v that goes to the water heater element. It worked for about 3 months and then the relay does not release because I think the timer contacts are fused together supplying constant ac to the rly. coil. I think that I may need a spark suppressor across the input of the 120v input of the relay coil. I was thinking about a RC network but I don't know what type of cap and resistor values are needed. I have a drawing but I don't know how to upload it to this post.

Thanks,
doogdoog


texts:
I'm wondering if it's possible to create a solenoid actuator that would be very powerful, and fast enough to keep up with a human's movements, and also relatively long (roughly 7 inches).

I found some info I was looking for on this question:
Long solenoid (50cm stroke)

Of which I learned that it's difficult to create a solenoid that large, as current diminishes over distance.

Is this sort of actuator possible?


texts:
The main goal of this project is to control a servo motor with an Arduino.

I have a 12V 5Ah power supply connected to the Arduino. The servo is connected to 5V and GND on the Arduino.

When using this setup with the Arduino connected via USB, everything works fine. As soon as I disconnect the USB and use the power supply, the servo starts to randomly move.

After searching a bit on the web, I think a solution would be to have a dedicated circuit to power the servo motor and the Arduino.

Thought:

Power Supply --> Voltage Regulator (5V) --> Servo Motor

Power Supply --> Arduino (12V)

Why:

This guy on YouTube

Questions:

Would this work?

Would a simple parallel connection from the power supply to the voltage regulator and Arduino be enough or more components needed?


texts: Why we don't use pull down resistors for implementing I2C protocol ? And why resistance value varies in I2C depending on its speed?

texts:
I have read that we have to pull-up the SDA and SCK lines because the lines are open drain/open collector. But I don't understand why can't we use pull-down?

Secondly why the value of resistance changes for different speed of operation (I think its related to weak/strong pull-up, but I don't know what weak/stong pull-up mean) ?


texts: Variable length timer match outputs on AVR?

texts: Is it possible to set the length of time until the next timer match output while you're in a timer match interrupt?


texts: Are I/O pin internal resistances equal to the Thevenin resistance?

texts:
I'm trying to find the Thevenin resistance of an I/O pin for the ATmega644. I see on the datasheet that there is a 20-50 kohm range of internal pull-up resistance. So with that, I can create a circuit modeled thus (ignore all values):

The voltage source is from the GND and I/O pin and the resistor in the diagram is the pull-up resistor. I only care about this pin when it is HIGH so I am assuming that the Veq=Vcc. Thus Req is the pullup resistance when high.

Am I missing something here? I'm looking for the output Thevenin resistance.


texts: Is it practically okay to use darlington triple?

texts:
I need to control a very high current in my project. I'm planning to use darlington formation with three transistors.

I'm planning to use BQ24450 to charge a group of 12V acid-lead battery.

BQ24450 supplies only 25mA current to control the switching BJT transistor. Charge current will be variable up to 80A. I haven't decided for transistor model yet, but it looks like a darlington pair will not create enough current gain since power BJTs usually have low current gain. Therefore, I decided to make a darlington group with three BJTs.

Is making darlington formation with three transistors practically okay? I have never seen it before in a professional design. Could it cause any problems (like leakage currents always keeping the BJTs on causing them to burn eventually)? If yes, are there any measures I can take?


texts:
I have to design a circuit to count up to a number and return to zero. It must have a carry signal (which I named a_o in my circuit) as flag to show that the maximum number of the counter has been reached.
The circuit is working fine, but it is inferring a Flip-Flop in the a_o signal that I don't want to be there. I have checked all reasons why an unexpected flip-flop can appear but I still can't solve the problem.

Many thanks in advance

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;

entity ej11 is

    generic (N : positive := 4;
                M : positive := 10);
    port (
            e_i :   in std_logic;
            nmr_i : in std_logic;
            clk_i   :   in std_logic;
            a_o :   out std_logic;
            q_o :   out std_logic_vector (N-1 downto 0));
end entity ej11;

architecture Comportamiento of ej11 is

    signal aux  :   unsigned (N-1 downto 0);
    signal acarreo : std_logic;

begin
    Cuenta:
    process (clk_i, nmr_i)
    begin
        if nmr_i='0' then
            aux <= (others => '0');
            acarreo <= '0';
        elsif rising_edge (clk_i) then
            if e_i = '1' then
                if aux < M-1 then
                    aux <= aux + 1;
                else
                    aux <= (others => '0');
                end if;

                if aux = M-2 then
                    acarreo <= '1';
                else
                    acarreo <= '0';
                end if;
            end if;
        end if;
    end process Cuenta;
    q_o <= std_logic_vector (aux);
    a_o <= acarreo;
end architecture Comportamiento;


texts: Guitar to Hammond tone wheel control interface

texts:
I'm new to electronics, but have been working on tube amps for a long time. I'm attempting to make a controll interface that allows me to control a Hammond tone wheel organ from guitar.Tonewheels are like gears with differing amount of teeth on them to create frequency sine waves via a magnetic pickup, not unlike an industrial tach.The signal is then filtered and amplified. I would like to add transistors to switch the signal paths (36 Tonewheels in all) and use the frequencies from my guitar strings/ pickups to close the corresponding transistors, allowing the signal of the corresponding Tonewheels to be played.
I'll bet there are thousands of ways to accomplish this, but I'm looking for a reasonably simple set of circuits that I can implement. My idea was to use a frequency to voltage converter like the lm2907 chip , but that's as far as my limited knowledge will let me go. I know y'all have a vast amount of experience, and I don't want to reinvent the wheel. Any help is appreciated, and hopefully in lay mans terms. Thanks! JB


texts: Controlling a 12V water pump to Raspberry PI fire back

texts:
I need to control a 12V water pump (like this) to a Raspberry PI zero W.

Can I control it from the 5V power out port using a this relay?
I heard that when switching off the relay there could be current coming back damaging my board, do I need to put some components between Raspberry and Realy to prevent it?

Thanks


texts: Can a voltage higher than 5V be applied to the 28BYJ-48 (5V) stepper motor?

texts:
I want to automate my roller blinds by using an ESP (NodeMCU) and I was thinking of using a stepper motor.
I had a 28BYJ-48(5V) stepper motor laying around with the ULN2003 driver it came with.
Unfornltunately the torque is not high enough to roll the blinds up. I tried applying 7.5V to the driver and now the torque is enough.
The stepoer motor does not much hotter than when I'm applying 5V to it.
My question is: how bad or unsafe is it to apply a voltage higher than 5V to the motor?


texts: Astable 555 timer circuit that resets on a heartbeat

texts:
I'm trying to design a circuit that will reset my ESP8266 when it crashes/hangs. It does this by sending a heartbeat to a 555 timer every minute which resets the 555 timer. The 555 timer is configured in an astable configuration which sends a pulse to the reset pin every one and half minute unless received heartbeat. This is the design for my circuit which is based of from here.

However, after simulating this circuit on a breadboard, it doesn't seem to work. I'm not very familiar with 555 timers, the link provided gives a better explanation on the circuit. Any help will be much appreciated.


texts: IC identification - top markings LA50 1XB50

texts:
I need to replace the device in the picture. I believe it's a DC-DC converter IC looking at the circuit around it.
Any ideas what it is or how I identify it?


texts: How is this small drone able to transmit video to such long distances? And that too an HD video?

texts:
I am an amateur enthusiast and a novice, thus please bear with me.

I was having the look at the http://www.proxdynamics.com/products/pd-100-black-hornet-prs drone. It weighs 18 grams and is able to transmit HD quality videos for up to 25 minutes.

From the looks of it the maximum size batter it can contain is 500mAh. With such a small battery, even if we ignore the energy requirements of other sub-systems, how can it capture, encode (in 720p, H.264 format), and transmit the video even theoretically.

What sort of physical encoders can encode such a video, and the transmitters can transmit such a high quality digital video over such a long range (requiring so much bandwidth).

I cannot make any sense of it (even theoretically) of such components with such energy requirements. Could someone please be kind enough to point out, what might be going on that i am missing?


texts: Simple Implementation of BiSS C interface for a position encoder

texts:
The BiSS C DB3 protocol interface for Absolute encoder is an Open Source and Free Communication protocol hardware compatible with SSI interface. It is used widely in absolute position encoders. However, searching for sample codes and implementations yields zero results. Most BiSS master are Closed source FPGA based or ASIC like (ICHAUS.de) or some (TI.com) microprocessors.

I want to replace an SSI encoder with BiSS in my DIY CNC machine, because it contains CRC and i want some kind of checksum to ensure the data read is correct. It is a point to point connection. I am only interested in reading the position. Not all the intelligent functions.

So my 2-part Question :

1- Can i get away with simple implementation (read position only) on the same 8-bit micro-controller that i am using now for SSI that is doing other staff . Or it is mandatory to set certain functions and registers for the device to work.

2- If I want to go the extra mile and implement a full BiSS master on a dedicated 8-bit Micro, is it a one man job ? too complex ? Any advice in this regard.


texts:
have xA, yA, and zA acceleration signals collected from a smartphone and I call it: set A and I also have xB, yB, and zB same acceleration signals from smartwatch: let's call this set B. I need to combine them together because I am trying to find which combination of devices give optimal result in regard to detect the subject's activities. I have more than these two sensors but I just ask about these two and then if I got an answer then apply it on all. I will combine smartphone with smartwatch, smartphone with sensor placed on upper arm and etc. However, I am not sure if this is right to do or doing this is eliminating necessary signals. Also, is this way better than only taking the average of these two sets. (A + B)/2  ?

Thank you


texts: How do I implement a sequence generator using a universal shift register?

texts:
How can I implement a sequence generator that generates the following sequence
0000
1000
0001
0011
0110
1101
1110
1111 using a universal shift register? The shift register I need to use is the 74LS194 model shown below where the inputs S1, S0 controls the shift mode.

If (S1,S0) = (0,0), then the current value is locked to the next state.
If (1,0), it's shift to right. If (0,1), it's shift to left, and (1,1) indicates parallel loading from the parallel data inputs.

I think this would be a simple question if the requirement was just using flip flops of my choice and not the shift register, but with this requirement I don't know where to start. Even though I draw 4 karnaugh maps for each digit I don't seem to grasp a clue. Any help would be appreciated. Thanks in advance!!!


texts: E-paper display working problem- UC8151D driver

texts:
I'm working on e-paper display GDEW0213T5-D product which including UC8151D IC driver.I can communicate with e-paper with SPI interface however there are problems with showing correct things(e.g. temperature value) on the screen.What is the correct algorithm to driving that kind of IC's?In the  example datasheet, there are some info's about proper usage.It includes "init" function as resetting operation, driver "init" function to initilazing driver, and local initialization function as refresh operation.I have also written functions to e-paper screen such as cursoring , putting pixels , chars drawing lines etc.However I'm stuck at initialization, I think I can't initialize the driver correctly.
If there is a UC8151 IC driver which written in C language I will be very appreciated.


texts: What is a programmable power-up sequencer?

texts:
What is a programmable power-up sequencer ?
How to use it in a PMIC to power AM335x TI microprocessor ?


texts: SMD Capacitor - read its values - 3H5 VLPU 330 2.5v

texts:
I have to replace a capacitor from a motherboard, but I can't find any information about the manufacturer, capacitance, voltage, tolerance and ESR values.

I suppose the capacitance is: 330uF (not sure, because I've found online that the coloured band can indicate the multiplier 10^-1, 10^0, 10^1,...) and voltage: 2.5v, but nothing about manufacturer, tolerance and ESR.

Here the image (3H5 VLPU 330 2.5v)

Can you help me please?

Thanks,

Alessandro.


texts:
Let's suppose I have three keytars, such as this model. I want to hook them up to the NES (Nintendo Entertainment System) in some fashion. The NES has a controller port I can use that is wired like this. So, basically, a serial port with three input pins and one output pin. (Many devices use just one input pin.)

There are two ways to hook up the keytar to a device: a MIDI cable or USB. Keep in mind I want to hook up three keytars, not just one, so making a cable that connects MIDI to the NES controller port will not be enough on its own.

Here is one solution I thought of, but I can't help but think it's overkill: the keytars plug into a USB hub, which plugs into an Arduino USB Host Shield. The Arduino's output pins are then connected to the NES controller port. I have not programmed an Arduino before, so I'm making a bit of a wild guess about its suitability to this problem. I am a bit intimidated by the prospect of having to write a USB driver for the keytar if none exists (and I'm guessing none exists), although on the upside the main data stream would probably still be standard MIDI messages. (EDIT: since the keytar's USB is class-compliant MIDI, an Arduino driver might exist already or be easy enough to write...)

There's another minor consideration: there is an issue that the NES has when reading the controller port. The system has a notorious bug that, under certain circumstances (which will definitely apply here), sometimes causes the controller port to be read twice during one read instruction. This causes one bit of input to be lost, since the device thinks there were two reads (and therefore sent two bits), but the NES program only received one. While I think it'd be possible to compensate for this on the NES end, I think I'd much prefer to compensate for it on the device end, since I believe it would be much easier to handle. I believe that the device can compensate by requiring a certain number of clocks to elapse before it will send the next bit. This sounds like a task the Arduino would be good at.

Before anyone brings it up: I am aware there already exists a product called MidiNES that does something similar. I have determined that MidiNES does not suit my needs; for one, it cannot be used with programmable software (since it uses the cartridge slot), and for another, I don't want to be dependent on a tool that might not be easily replaced if it stops working and its maker has gone out of business.

So, that's my situation. How would you approach this problem?


texts: Switching a higher voltage from a microcontroller

texts:
I am designing a battery charger circuit controlled by a microcontroller. Once the battery charges at constant current it switches to constant voltage and hence I need to design a switch that will be controlled by the microcontroller to switch between these two circuits.
I designed the following circuit, where an NPN transistor will act as a switch to control the PNP transistor connected to it. It will basically switch it on and off. However, the circuit works well for up to 0.35Amps. Increasing the current beyond 0.35A, will cause very inaccurate readings. What might bevthe problem? Am I biasing the transistors wrongly or taking incorrect readings/decisions in my circuit that will cause the switching circuit to function badly beyond that certain point? I want my circuit to work up to max around 0.8A.
Thanks in advance


texts:
When designing decoupling capacitors why there are always parallel capacitors arrangements with decreasing values? It seems a redundancy to have this kind of configuration because the equivalent circuit is just one insignificant increase in the single larger capacitor.

Take this circuit as an example: isn't it the same to put only one capacitor 1,100uF? And why does it use a 0.01uF? I mean, the first capacitor tolerance is probably larger than that!

Please some insight!


texts: Eagle Cad - redefining terminals of a component

texts:
I use default BC337 transistor from the eagle-cad's library, terminals are: 1- Emitter, 2 Base, 3 Collector. however, datasheet of the BC337 that I am using defines the terminals differently 1 collector; 2 base; 3 emitter.

how is it possible to redefine the terminals of the component on Eagle Cad 6.0?


texts: Choosing the best approach for data selection in a datapath

texts:
For a university project, I have to design and construct a very simple CPU including the ALU.
In order to select between different data lines that go into the ALU(32-bit data line), I have thought of two different approaches.

Basically, the first method is using a multiplexer, For example, it takes in input from register file and instruction register and gives out the output. This was the method recommended to me by the professor, however this method seems to get very complex very quickly based on the size of the data buses, and the number of operations needed to be performed.

The second method I found was to use tri-state buffers along with a decoder. Rather than use a huge multiplexer, it only requires a decoder large enough for the number of operations. However, with this solution, I was warned that there could be timing issues, where during the transition of the decoder, two tri-state buffers could be simultaneously activated, which would cause a short-circuit. Is there any truth to this, and can it be avoided? This was the method that I thought was used inside most modern architectures, but I could be incorrect.

Also, how is there no timing violation in case of multiplexers


texts: How does an inverter affect the computer?

texts:
I have rampant power failure in my country. So to mitigate, we have an inverter that basically converts the charge from a big lead-acid battery to AC. But as far as i know this doesn't produce pure sine AC. It is something close to sine.
The output voltage is 220V nonetheless so it is hard to find out when the power is out.
Sometimes, i use my laptop on AC. My question is, will using laptop on inverter affect the components since output is not pure sine?


texts: Cascading of S-Matrices using T-parameters messes up S11 and S22?

texts: I wanted understand how cascading works and so I modelled a microstripline of say length 'L' in CST and got its S-params. Then I simulated a line of length 'L/2' and got the results. So, the response of line of length 'L' should be the cascaded responses of two 'L/2' lines right? Anyway, I converted them to T-params and got the resultant S-params. However, only S12 and S21 matches the S-params of line 'L' whereas S11 and S22 vary significantly. I tried with different structures, for example with a mitered bend but in each case S11 and S22 vary significantly. I was wondering if anyone can explain why this is?


texts: Zener Diodes: How are different voltage drops achieved

texts: How do semiconductor makers make zener diodes with a fairly wide range of voltage drops? In particular I'm curious how they get small increments - 3.3V, 3.6V 3.9V, 4.2V, 4.8V etc as I thought the semiconductor material basically always resulted in a fix voltage drop which could not be adjusted.


texts:
Soon, I'll try to create my own PCB with the iron chloride method. I watched a video on that and it seems quite "easy". The only thing that I don't understand is the need to put the PCB on the iron chloride solution. I read on Internet that it will "burn" the PCB but I don't really understand why it needs to be done as after, we remove all the iron particles from the PCB.

Can someone give me some information about that ?


texts: Why does bluetooth (still) only support pairing two devices?

texts:
When bluetooth was first devised there was typically only one device to connect to at a time so it was quite natural to just implement a pairing protocol.
I believe we are now on Bluetooth 5
Why is it that:

Each device may typically only pair with a single other device?
Even in devices that have multiple bluetooth capable chips only one is used.
In contrast with the profileration of usb hubs there are very few bluetooth hubs on sale and they are relaitvely expensive (e.g. the CASSIA which seems to have been discontinued)

I note that there is now "dual audio". Allowing you to pair with up to 3 (which is more than dual!) audio devices but this is not what I'm after.
Referring to this article one bluetooth master can support up to 7 slaves.
However if we consider some basic IoT scenarios this does not match the requirements very well.
Consider:

I have one or more bluetooth speakers in my home

I would like to be able to send music to one from any device:

My phone
My partners phone
A PC

Without having the speaker or the audio source forget the previous connection.
Only one can stream at a time so maybe the devices have a priority or one lends the connection to another.

I have a phone and I want to connect:

a smartwatch
bluetooth headphones
a heart monitor
one or more speakers as above

I might want to lend a device to someone in my household (e.g. the headphones or heart monitor)

To my mind this suggests we want a peer to peer network like we have with WIFI or ethernet. So why hasn't bluetooth evolved in this direction?
It seems it have if I google "bluetooth piconet"
It looks like the second scenario ought to be supported (the phone as master and the rest as slaves) but I commonly find in android at least that pairing one device causes others to be disconnected.
Is this because the slave needs to be a master temporarily to configure it?
How much of this is a 'mere' software issue and how much is down to issues with the protocol and technology itself?
I think the answer is that its down to the software. Any device wanting to act as the 'master' needs to support creating a piconet which is more advanced than you find in the average smartphone software. But this begs the question (as old as the invention of software) why isn't there better software?
I think I've mostly answered my own question here but perhaps someone out there can offer further enlightenment.
Related:

Make two bluetooth modules communicate directly?
Bluetooth Concurrent connection
Pairing to a module containing multiple Bluetooth units
https://electronics.stackexchange.com/a/430258/270158
https://stackoverflow.com/questions/5005253/establishing-a-bluetooth-piconet-in-android

See also

https://en.wikipedia.org/wiki/piconet
https://en.wikipedia.org/wiki/Scatternet


texts:
I need to select a LDO for design with below details

in volt= 15V
Op volt= 5V
op current require = 250mA

I gone through UA78M05IDCYR part (TI), it has thermal data as below
Rtheta JA =53 C/W
Rtheta JC=30.6C/W
Bias current=4mA
Tamb=50C

Pd= (VIn-Vo)Io+ VinIbias= (15-5)*250 + 4*15 =2560mW

Tj=PdXRtheta JA + Tamb= 2.56*53 + 50 =185C

185C is more than 150C limit of IC ( I should consider 125C max for be in safe regin).

Q1) Is my calculation is right
Q2) If yes then I can not use this part in my design , then why they state output current uptp 500mA in datasheet.
Q3) Do I need to add heat sink ( PCB heatsink)
Q4) what size i need to consider for PCB copper area.


texts:
Is there an IEEE or other standard for how Noise Spectral Density is calculated? In particular, when they give a single figure (like \$12.4\,\text{nV
}/\sqrt{\text{Hz}}\$) is that averaged over the whole spectrum, including the \$1/f\$ flicker noise, or is that only a measure of the noise floor?

A follow up to that would be, if that is the case what is the standard for the bandwidth range to use when measuring noise floor?


texts: Why are input logic levels are more tolerant than output logic levels?

texts:
An input 1 is defined from 2V to 5V and an input 0 from 0V to 0,8V while an output 1 is defined from 2,4V to 5V and output 0 from 0V to 0,4V.

Why are output logic levels defined to be more tolerant? Why not the same?


texts: Please help to identify component (From Nest E thermostat base)

texts:
I've just blown the thermostat base by misconnecting wires.
The component marked on the picture is visibly damaged. Is it possible to identify what that part is?

Thanks.


texts: Decoupling on PCB - Filled Zones or Traces

texts:
Which of the two following PCB layouts for the given schematics (7805 voltage regulator) is better? Do filled zones affect filter/decoupling capacitors negatively?
Thanks!
Update: Second layer is a ground plane.
Schematics

Variant 1 (Filled Zones)

Variant 2 (Traces)


texts:
When I send any data from serial port, RX pins are flashing but ISR is not running.
Here is my code.

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

#define F_CPU 16000000

volatile int NUMBER_OF_RECEIVED_BYTES = 0;

ISR(USART0_RX_vect)
{
    NUMBER_OF_RECEIVED_BYTES++;

}
int main(void)
{
    #define USART_BAUDRATE 9600
    #define UBRR_VALUE (((F_CPU / (USART_BAUDRATE * 16UL))) - 1)

    UBRR0H = (uint8_t)(UBRR_VALUE>>8);
    UBRR0L = (uint8_t)UBRR_VALUE;
    UCSR0B |= (1 << RXEN0) | (1 << TXEN0) | (1 << RXCIE0);
    UCSR0C |= (1<<UCSZ01)|(1<<UCSZ00);
    while (NUMBER_OF_RECEIVED_BYTES == 0);
    DDRB |= (1 << DDB7);
    sei();
    while (1)
    {
        PORTB ^= (1 << PB7);
        _delay_ms(999);
    }
}


texts: Broadcast audio to multiple receivers via Bluetooth

texts:
I want to be able to connect multiple Bluetooth devices to a Bluetooth transmitter, and then stream audio from a portable MP3 player, via Bluetooth, to all of the connected Bluetooth receivers. Is this even possible?

I thought of using the A2DP profile to stream audio. But is it possible to stream audio to multiple receivers?

I was hoping I could use a Bluetooth module for this, something like Bluegiga WT32. But perhaps I should use a micro controller, maybe an Arduino, instead?

Any help would be of great use!
/Johnny


texts:
I am getting some strange character displays on hyper terminal, after establishing communication with my GSM modem using the appropriate baud rate. When I type "AT", it appears to get repeated  or display strange characters (as though the baud rate were not correct) on the hyper terminal screen as "AATT". And all other AT commands get repeated as well, but what surprises me is that they all respond to the command. "AATT"(having typed "AT") give me "OK".

What could possibly be the problem? I am connecting the Modem to the DB9 using a MAX232. Below is the response

øatt
OK
aaütø
OK
aatt++ücnnmmiiþ?ø
+CNMI: 1,0,0,0,0

OK
aattþ+ccssccss??ø
+CSCS: "UCS2"

OK

RING

RING

RING

NO CARRIER

øat++ücnnmmii==11<,22<,00,,00,,00ø

OK

aattþ+ccssccss==""GGêSMM""ø

OK

Øaüt++ccmmögæf==11ø

OK

aatt

OK

aaüt++ccþnmii??

+CNMI: 1,2,0,0,0

OK


texts: This question covered it for enclosures. However, from the point of view of the fan attached to a heatsink does it matter whether air is blown through the fins, or sucked through the fins. In other words, is the pattern of airflow different enough to matter?


texts:
I am looking for feedback and experienced insight as I'm new to this world.
I have a 12V 18Ah AGM battery connected to a 300W 110V pure sine wave inverter with the intention of running a 140W speaker and my MacBook Pro which will charge from the 60W USB-C port on the inverter. People have been bringing drum sets and electric guitars to the park here and I'm keen on bringing my bass guitar and/or running ableton in the middle of Piedmont Park, effectively having drums, bass, synths or any other VST.
I'd like to firm up some things since I've been learning as I go here figuring this out. Ultimately I'm wondering how long I can power my speaker and MacBook, although I'm adding a solar panel to the kit for a constant trickle charge throughout the day. But for now lets pretend I don't have the solar charger.
A few outstanding questions:

At what point does a 12V AGM battery drop below 12V? Subsequently what's too low of a voltage to be using the battery?
Is it steadfast the my amperage draw is simply watts per device divided by volts per? In my case this is (140W/110V= 1.23A for the speaker) + (60W/110V= .55A for the MacBook) totaling 1.78 amps total load. Using max 50% of my batteries total Ah's, I get 9Ah/1.78A= ~5 hours of battery-powered playtime. Is it really this simple?
I have a voltmeter hooked up to the battery and was considering an ammeter to be sure of my consumption; but if the amps rule is steadfast, then what's the point?

I'm assuming by adding a solar panel into the mix I can prolong. Given the day is sunny and I'm meeting the panels sunlight requirements, how do I factor these numbers into the equation? Research tells me 25% of the battery's Ah rating is a good amps for charging. 25% of 18 is 4.5 so a 48 or 60 watt solar charger should be great for this? Any tips, advice, or confirmation on this?
Thanks.


texts: How would this transistor diagram be drawn if we draw it with all the closed circuits?

texts:
In a book about computers I have this transistor diagram:

the first two transistors are p types and the second two are n types. I am wondering how it should have been drawn if we close the circuits, because as far as I know we must ahve closed curicuits to get electricity.
1.
The first idea I have is that we must close the the ground with the power supply, is this correct? This part would look like this? Notice the top here, I have drawn the red line above the horisontal line, but maybe it should be just below the horistontal line?

Secondly they talk about C beeing connected to ground or 1,2 Volts, does that mean that we close the curicuit C like this:?

Now I must draw the line in the subtrate in the transistors, here I have two options. I only draw one p transistor and one n transistor. Option 3a)

Or 3b:

Are wither 3a oe 3b correct?
And maybe they would be short-curcuited if I draw it like I did, so maybe I should have added some resistors aswell? If the drawing are wrong, could you please explain how we would draw the full circuit?


texts: Limitations of Arduino Voltage Pulse? (TTL)

texts:
I am new to this forum, and I have a question regard EE and Arduino based boards.

Are Arduino based boards capable of producing pulses in the range of MICROseconds (usecs)? For example, I would like to generate 1 pulse (say 5 volts for 200usecs) given an arbitrary command I send to the microcontroller. This pulse would be used to activate a device it is attached to. Is this possible?

I have an Azteeg X3 Pro board (ATMEGA2560 and RAMPS 1.4 base).

Ideally, this picture is what I am trying to do.


texts:
I want to scale and shift my voltage signal by below relation:

$$
V_{out} = \frac {10} {12} \cdot V_{in} - 10
$$

Indeed my primary voltage is from 0v to 24v and I want to put it from -10v to +10v.

I try to use the below circuit but its gain is always greater than 1.

Image from SLOA097 TI.

Does anyone know how I can achieve my goal? I have ±12v and 5v power lines.

EDIT:
According to the innovative solution by scorpdaddy, I thought it would be valuable to edit my question:

High input impedance is required to decrease load effects. How can it be achieved?
How can I achieve the more and more accuracy?


texts: Why can't we operate at high frequencies (>0.5GHz) when having a resonant inductive coupling circuit?

texts:
I am currently trying to figure out if a high frequency (GHz) resonant inductive coupling circuit would be feasible and efficient when wirelessly transferring power. Through many research papers, researchers suggest operating at frequencies lower than 100MHz.

I have seen people using two coil, three coil, four coil systems, but didn't seen anyone operating at frequencies higher than 100MHz.

Why is that the case? What are the governing laws of such behavior?


texts: How to clean flux from a DDR footprint without ESD risk?

texts:
I could be paranoid, but I have to replace a batch of DDRs from a board. Those are connected directly to the IC, they aren't GPIOs, so I believe the ESD risk is higher.

I need to remove the old solder left behind from the old DDRs and to do so I will use solder wick and no-clean flux. I will then clean the flux using isopropyl alcohol and a brush.

How do I minimise ESD risk in the process?

I will be using an ESD wristband, on an ESD-safe surface, but I'm worried about static charge in the brush.

Am I overthinking it?


texts: Op Amp with capacitive load - Peak Detector

texts:
I have been looking into peak detector circuits for something I am designing and looking through Google, the common method seems to be this:

Quite simple really. But, I have an engineer at my work who isn't a fan of this circuit because he says an op amp will struggle to drive a capacitive load, which I know is a thing. So I built the circuit and have been messing around with capacitor values and different op amps, and I can't seem to get the op-amp to start oscillating as he tells me it will. I like this circuit for its simplicity, and surely if you are careful about component selection, these things shouldn't be much of a worry? The engineer has admitted that analog design isn't their strong point, but is still unsure of this circuit.
From what I have seen, it has been used widely (although maybe not so much anymore) and during my testing, it had no problem driving capacitors into the µF range (I tested up to 4.7µF) although I should only need a maximum of 1µF, so I would think this is fine.
I did a bit of looking into op amps and capacitive loads and sure enough, op amps can go into oscillation if trying to drive capacitive loads, and these can sometimes be small values. So why does it not seem to affect this circuit? Or does it, and I am just in fact not seeing it?
Just for clarification, I am not asking for alternative circuits, I just want to know why this configuration seems to be stable with a capacitive load.


texts: Is there such a thing as an insulated gate SCR or anything fitting that description?


texts: How much gain for optical open-air receiver?

texts:
I am planning to make an experimental communications system.

I will use a high power LED  (≈3watts) Amplitude Modulated with a sound signal and eventually Pulse modulated with digital data for the transmitter.

And a focused lens with some sort of photo detector (PhotoTransistor, PhotoDiode, PhotoResistor, Plain old LED etc.) for the receiver.

To amplify the small AM signal from the photo detector, I am looking at microphone preamp circuits. How much gain will I need to amplify this to around MP3 player output?

(A high impedance output is fine for I will be feeding it into another amplifier stage, I just want the approximate voltage of an MP3 player output)


texts: Doubt about Poles of the Transfer Function

texts: Why shouldn't the poles of a tf be in the RHP. I mean I know in a vague way, but what is the explanation/proof? Thanks.


texts: What for are two resistors and one capacitor when attaching an audio CD drive output to a TDA7318, but not for Line In?

texts:
I'm trying to build a TDA7318 audio mixer chip into my automobile infotainment system. Now I've found a similar project, where the output of the CD drive is attached to the chip by using two resistors (one in series, one in parallel (attached to ground)) and one 2.2 µF capacitor (in series). There are also two Line In inputs, both of them just with a cap in series. The tuner input has neither resistors, nor a capacitor.
Why is it so? The official datasheet of the TDA only mentions 2.2 µF caps, but for each audio input. Will I need the caps or even the resistors when attaching a computer sound output and a DAB+/FM radio board? Sorry for a question, which might sound pointless, but I'm not an audio systems professional.


texts: Serial Flash always returning 0x00 while reading after writing

texts:
Could someone look into the code and tell me the mistake in the code

I am trying to Interface PIC16F877a and AT25SF041 serial flash.

I have pulled up CS pin to 5V using 1K resistor
The flash is powered by 3.5V(Vcc) obtained from LM317. The WP,Hold pins have been connected to Vcc(3.3V)

Coding is done using MPLAB X IDE, using XC8 compiler.

void spiInit()
{
   SSPSTAT=0x00;
   SSPCON=0x20;
   TRISCbits.TRISC2=0;
   TRISCbits.TRISC3=0;
   TRISCbits.TRISC4=1;
   TRISCbits.TRISC5=0;
   SS=1;
}
void spiWrite(char Wdata)
{
   SSPBUF=Wdata;
   while(BF);
}
char spiRead()
{
   while(!BF);
   return SSPBUF;
}

Erase Function:

void Erase()
{
  SS=1;
  SS=0;
  spiWrite(0xD8);
  spiWrite(0x01);
  spiWrite(0x01);
  spiWrite(0x01);
  SS=1;
}

Write enable Function:

void writeEnable()
{
  SS=1;
  SS=0;
  spiWrite(0x06);
  SS=1;
}

Write Function:

void Write(char txData)
{
   int i=0;
   SS=0;
   spiWrite(0x02);
   spiWrite(0x01);
   spiWrite(0x01);
   spiWrite(0x01);
   spiWrite(txData);
   i++;
   SS=1;
}

Read function :

char Read()
{
   char rxData;
   SS=0;
   spiWrite(0x03);
   spiWrite(0x01);
   spiWrite(0x01);
   spiWrite(0x01);
   rxData=spiRead();
   SS=1;
}

These are my functions and all am trying to do is write a character to the flash and read the same

void main()
{
  spiInit();
  RC1=0;
  Erase();
  __delay_ms(100);
  writeEnable();
  Write('A');                         //Write
  __delay_ms(100);
  rx=Read();                          //Read
  while(1);
}

but the value read is always 0x00
could someone point out my mistake.
Here is my Circuit(crystal oscillator, Vdd, Ground have been excluded from the circuit diagram).

Thank you for your valuable time.


texts:
I am developing a logic in an FPGA that will act as a controller for a chip by TI. I got the TI chip IBIS model from the TI website.

My controller is ready and I want to simulate it using ModelSim. But I must have the simulation for  both the controller and the TI chip together.  For this purpose I am trying to use IBIS model of the chip plus my design of the controller in Verilog and simulate in ModelSim. How do I use IBIS model in ModelSim?  Does ModelSim support IBIS? If not then which tool should be used and how do I proceed for this simulation?

Thanks in advance for your precious time.


texts: I bought a cell phone in China (read chinese iphone), that despite the operational system is awful, when I opened to check the hardware and I found a not so bad hardware. I was able to extract microphone, motor, speaker and other interesting things. However there is an ARM processor that I couldn't remove. I'm a computer scientist (I had basic EE in the univeristy) and hobbyist. I'm able to extract components, when there is a solder to melt, but I never played with SMD. I found this tool, but there is any other way to do it?


texts: Whats the purpose of the box in Proteus?

texts:
Like the title suggest, in Proteus 8, there is a box. why is it there?

because we can simulate outside the box and it will work, so whats the purpose of the box ?


texts: How can a PSU be capable of providing more current than it draws from the mains

texts: The supply cable that came with my PSU has a 13A fuse fitted inside it's plug.  However on the side of the PSU it says it's cable of producing 30A of current at 5V. How is that possible when it only has 13A to play with?


texts:
I made a digital input circuit to convert a 120Vac waveform into a digital 2.3V signal. I would like to add a "low-pass" filter at the output to get a low level for higher frequencies than 1kHz. I can't just use an inverter after a classic low-pass filter because I need to keep the high-low sequence for frequencies below 1kHz.

All suggestions are welcome

Edit

What I want below the cutoff frequency :

What I want above the cutoff frequency :

As you know, a low-pass filter will "smooth" v(OUT) until it becomes a 2.3V DC, and that's what I want to avoid. I want my digital input to be inactive for high frequencies.


texts: what will be the resistor to find the time constant?

texts:
simulate this circuit – Schematic created using CircuitLab

What resistance should I use to find the time constant? is it 30 ohm or 1130 ohm?
what if the capacitor is an inductor will I be using the same value for the resistor to find the time constant?


texts: Can anyone tell me why nothing is displayed on the scope?

texts:
This design isn't working, nothing is displayed on the scope.
CODE SEGMENT
ORG 100H

mov al,37h

mov dx,6h

out dx,al

mov ax,1000h

mov dx,0h

out dx,al

mov dx,0h

mov al,ah

out dx,al

        CODE ENDS

END


texts: Driving a fan using a mosfet, do I need a diode?

texts:
I am using this BS170 MOSFET to drive a fan using a pwm signal generated by a 3.3V MCU according to the following schematics:

(I know about the wrong symbol it's just for the packaging on the PCB)

So my gate gets connected to ground using the pulldown resistor and to the PWM signal.

I have two questions:

Should i still use the D1 diode for back EMF protection or i can relay on the internal one in my transistor.
Is my transistor is suitable for a fan using 0.32A. It should handle 0.5A so it should work right?


texts: Confusion between Class B and Class AB Amplifier

texts:
I am reading about output stages of an amplifier and classes of amplifier. The following circuit is named as "Class B" amplifier.

From my understanding, the above circuit should be a class AB amplifier. Because we have a constant biasing, so both transistors would be slightly ON even if the signal is OFF, giving rise to  small quiscient current. The crossover distortion is reduced greatly. But I am not sure why in my notes, they regard it as a class B amplifier.

I understand that if we adjust the battery voltage vbatn and vbatp, then would it become a class AB amplifier.

And I am not sure how the following circuit is regarded as Class C source follower: (This below circuit is actually class B from my understanding)

So, could we operate the circuit in class B or class AB or class C? Are class B,AB,C are terms for "Operation"?

f anybody could assist on the above, it would be helpful.


texts: Lighting either of two LEDs, or none, based on digital input

texts:
I ran into a problem which I tought was extremely simple, and after giving it some thought for more than 2 hours I had to recognise it actually is quite complicated. The problem is the following:

I have a circuit which runs on a +24V power supply, so only discrete components are available (no integreated circuit)
The input of the system is a single digital input that can be either at low level, at high level, or disconnected
When input is at 0V level, I want the first LED to emit light. When the input is at +24V level, I want the second LED to emit light. When the input is unconnected (left open), I do not the LEDS to emit light.
The leds use a high current (25 to 50 mA) so they must not rely on the input to provide this current, it should be buffered with transistors

The solution that does this with the smallest amount of discrete components will be approved.

For some reason, all my solutions could not shut both transistors at the same time, and I always had the rist of having some unwanted current putting them in linear mode, leading to LEDs being partially lit up. I do not want that, I want a current as close as possible to zero through the LEDs when they are shutted off.

Also, last but not least I do not with to be tied to a particular transistor model or whathever, so please use generic component whenever possible.

EDIT : So here is my schematic. It works fine for cases where the input is close to 0V or power supply. It however does not work when the input is unconnected, because current can flow through R1 and R3, and it will put transistors in linear mode and send some unwanted current through the LEDs.

I tried a similar circuit using common emmiter instead of common collector, but the fundamental problem is the same, when the input is left floating, the current can make it's way through the base of both transistors at the same time, putting them in linear mode, and having some current in the LEDs :

simulate this circuit – Schematic created using CircuitLab

(Just trying the builtin schematic for the 1st time, so don't blame me. Please ignore resistor values, they have absolutely no meaning whatsoever).


texts:
I have a 12v cable that sometimes pass (75%on-25%off) and other times 100%on.

What can I put on that cable so if the input is (75%on-25%off) then the output is 0v, and if the input is 100%on the output is 12v?

Is a resistor what I need?

Here i want the purple LED only to be on when the brake light is 100%. Right now if is 75% the purple LED is flickering.


texts: Do FETs have a Maximum Gate-Drain voltage?

texts: I know FETs have a Absolute max \$|V_{gs}|\$, and a max \$V_{ds}\$. So can we assume, say for an N type, that: $$\text{max}|V_{gd}| = V_{ds} + |V_{gs}|\\$$


texts: Simple braking chopper using Zener/TVS diode

texts:
So I'm designing a motor controller, relatively low power (100-150W, 12-48V supply), and I'm thinking about adding a braking chopper. Not strictly needed in this design, but it would be a nice value-add and maybe provide some useful protection for the 60V bridge MOSFETs.

All the chopper circuits I've seen use something fancy like a comparator/opamp to drive the chopper, but I can't help but wonder if there's a simpler solution.

simulate this circuit – Schematic created using CircuitLab

(Forgive the improvised pulse-generator setup; SW2 triggers at 1us and SW3 at 2us. Ideal pulse generators go to 0V after the pulse is over; this way it ends up at Hi-Z so the spike can actually get pulled down by a chopper. I guess I could have run a DC sweep instead of a transient analysis, but eh. Also, don't take the component models too seriously.)

Zeners are slow(-ish, I'd bet they're still faster than my MCU could turn off the bridge) but a unidirectional TVS should be faster than even an opamp; I've run various simulations and it looks like this is a sound idea. The obvious question, then, is why I haven't seen this before: probably because it's a bad idea for some reason I haven't thought of yet.

So, is this a brilliant insight and example of my great engineering prowess, or evidence that I'm clearly not there yet?


texts: What happens when triac terminals MT1/MT2 are switched?

texts: According all literature, terminals MT1/A1 and MT2/A2 must be connected to neutral and phase respectively. What happens if you reverse the wiring? House sockets here are randomly wired, so it's a practical problem.


texts:
I have a question regarding AD conversion in a microcontroller. Before we go on, I use a dsPIC33EP64GS506 (link on its datasheet), 3.3 V power supply, and 12-bit unsigned conversion. The system sample time is 40 us.

My question: is it normal that the standard deviation of a digital measurement is around 2.7 quants*, for a completely steady analog input? Is it normal that ADC modules have an inherent noise of 3 quants, or should I try to find other possible reasons, e.g., a bad power supply for the ADC module etc.?

Just to mention, this analog input has been filtered using an analog filter with a cut-off frequency at 5 kHz. If I apply a digital filter with the same cut-off frequency, the standard deviation is around 0.55 quants.

*I don't know what is a right term for a "quant"; 12-bit measurements have 4096 of what we call "quants". 1 quant corresponds to 0.8 mV in input signal. When someone says that ADC inherent noise is 3 LSBs, does this mean 3 or 8 quants?

Here is an example of such digital measurement: A/D conversion with analog filter in blue, and with digital conversion in red.


texts: How to check for Stack overflow in an embedded application?

texts:
I have run into a problem where I believe my stack is overflowing. The reason I am inclined to think this way, is due to the following:

1) Compile code, dump into the device: - no activity from the device (I am expecting an 'I am alive' message)
2) In this situation, I increased the stack size by 10 bytes, recompiled and dumped to the device, and the problem went away.
3) Tried the above two steps 10 times, back and forth, and can reproduce the problem reliably, and fix it reliably.

I want to see the stack falling over, how do I do this?

I am currently using an M16 Microcontroller, with 2K RAM (30 bytes left), 256 Bytes Stack size.
The IAR Workbench that I am using, does not have the call graph utility.

Are there other ways to do this - check the stack falling over and by how much in code?

Any help will really be appreciated.

Thanks!


texts: Glitches on ring oscillator based on discrete logic gates

texts:
I built a ring oscillator out of discrete logic gates as in the following schematic:

It consists of 6 inverters/NOT gate (SN74LVC1G04@U12-17) and one NAND gate (SN74LVC1G00@U11) so the circuit can be reset.

In addition to that, I added a Schmitt-trigger (SN74LVC1G17@U19) to clean the output and a button to reset the circuit.
At first glance, the circuit seems to work. Here is the output of CHAIN1 (yellow) and CHAIN1_OUT (blue, output of Schmitt-trigger) on my oscilloscope:

However, this circuit sometimes glitches as captured below:

These glitches appear at irregular interval (~every 30-100 cycles). Where do these glitches come from and how can these be fixed?


texts:
I am doing a project to record and log the voltages of an 8 cell lithium battery. The project is based on an STM32 microcontroller, and logging is done on an SD card. I have made the first version of the PCB, and have spent a lot of time testing the board, including tuning the digital filter.

Everything was working correctly, until I moved on to calibrating the RTC. I have discovered that it is out of spec by 200ppm. This measurement was made by using the calibration output on the micro controller. Using a logic analyzer, I can see the output frequency varies between 499 and 524Hz, when it should be 512Hz. Is this indicating some type of interference?

On closer examination, I can hear the crystal audibly whining when I put my ear close to it. As the input voltage changes (the design range is from 4.5V to 32V), the whine changes too. Also, when I am connected to the board using USB, the whine changes again to a different type.

I use a MAX15062A buck converter in PFM mode to power all active components on the PCB. The current draw from this buck converter is about 20mA (measured). I think that the output noise from this SMPS is what is causing my problem with the RTC, and the crystal whining.

The crystal is mounted on a local ground plane, which is stitched using vias to the global ground plane.  X2 is not mounted, while X1 is the RTC crystal.

I took the buck converter out of the circuit and supplied 3.3V directly from STLINK (which is the output of a linear regulator). The crystal whine went away, and now the RTC output is between 511.8 and 512Hz. (I should say I am using a clone Saleae logic analyzer from eBay which may not be completely precise).
I took the buck converter out of the circuit and supplied 3.3V directly from 2 different bench top power supplies set to 3.3V output. Again the crystal whine went away.
I have a second identical PCB of my project where just the buck converter part of the circuit is assembled. I take the output of this buck converter and feed it directly to the 3.3V plane on the other PCB where everything is mounted, and the crystal whine comes back, with the same characteristics. So is it fair to say, that my problem is directly being caused by the output voltage ripple of my buck converter?

So leading on from this, could people please help me verify what the cause of my problem is and how I may solve it? I was thinking I would need an LC/RC filter, or some ferrite bead just after the output of the buck converter?

The output voltage frequency of this buck converter is about 10kHz in the mode I am using it (PFM) and the current draw of my application. The voltage ripple
3.32V and 3.39V (according to the Maxim simulation). I see a stable output voltage of 3.35V on my multimeter.

Layout SMPS:

Note C15, C16 output caps are 10uF 16V X7R.

Edit: Pin 7 of MAX15062 unconnected to force PFM mode in low loads (like my application. From datasheet:

Edit:
Possible source of RTC issue: no return path for SD CLK and SD CMD lines..


texts:
How does a latchup manifest in op amps? We have an LTC1150 that seems to stop working properly. By the latter, I mean it's in a PID loop and the loop just... stops working and sits at a particular voltage. It may well be experiencing input spikes going beyond its rails. How plausible does that sound? What else might I expect, or should I look for?

Here is a circuit diagram. The problem occurs with U9, marked as an OPA227U on the diagram but actually using an LTC1150. The coil sits in a 1T magnetic field and is connected across RED and BLACK. It is part of a PID loop in a microbalance.


texts: PLL versus putt-putt-skip, putt-putt-wait, fractional-rate division, or other approaches

texts:
Many applications use PLL's to generate frequencies where long-term frequency accuracy is necessary, but where a certain amount of short-term jitter might be acceptable.  I've seen a number of devices with very-low-current low-to-moderate-precision oscillators, and was wondering whether it would be practical for device manufacturers to reduce device current consumption by replacing PLL's with other approaches, such as (note some of the following terms are my own invention, since I don't know of standard names for these techniques):

Putt-putt-wait: If the goal is to have a signal that's N times the input frequency, arrange for the oscillator frequency to be at least N times the input frequency; let the oscillator run for N pulses, stop it until the next input pulse, run for N pulses, stop until next input, etc.
Putt-putt-skip: If the goal is to have a signal that's N times the input frequency, arrange for the oscillator frequency to be at least N times the input frequency; allow N pulses of the oscillator through, then stifle pulses from the oscillator until the next input pulse, then let another N pulses through, etc.
Fractional-rate division: If the goal is to have a signal that's N times the input frequency, arrange for the oscillator frequency to be at least N times the input frequency, and provide hardware to stifle a programmable fraction of the oscillator pulses.  Either hardware or software may then adjust what fraction of the oscillator pulses are dropped so as to maintain a consistent phase relationship with the reference wave.
Rate-control dithering: If the goal is to have a signal that's N times the input frequency, allow the oscillator frequency be instantly switchable between a rate that's too fast and one that's too slow, and provide hardware to make a programmable fraction of the cycles be "slow" ones.  As above, software or software could adjust this fraction so as to maintain a phase lock if desired.

All of these approaches would have the restriction that the oscillator rate has to be guaranteed to be slow enough not to violate the device's internal cycle timings, but I would expect that in many cases they would make it practical to keep a precise counter/timing reference alive even during sleep mode.

What advantages or disadvantages are there to using approaches like the above in lieu of a PLL?  I've never seen the latter two approaches used, but I would think that in many cases they'd provide adequate performance while using a fraction of the power of a PLL (perhaps some "digital PLL"'s use approach #3, but I've never heard of such things operating in sub-mA range)


texts: LiPo LED/Fiber job not working correctly after plugged in

texts:
I'm putting LEDs and fiber lighting into a ship model. There's not a ton of room, but I found I could fit two LiPo (3.7v, 2400mAH, DTP 605068) Batteries in series with a single two-prong connector. The connector is plugged into a "SparkFun LiPo Charger Basic-Micro-USB (PRT-10217), and the +/- terminals of the charger board run to the circuit.  Now for the problem.
Everything lit up really well and stayed lit up the first time, but whenever it gets plugged in the battery stops powering the circuit. Not only that, but when plugged in to a micro usb to any power source only part of the circuit comes on at full brightness (The branch with the 2red and 1 white LEDs), the rest of the red leds glow very dimly (except one 2 red branch that doesn't light at all). I suspect most of the white LEDs are lighting dimly, but as they are lighting bundles of end-glow fiber, it wouldn't be too obvious by the outside of the ship.
However, I've found that I could "jump" it by briefly connecting another battery of the same voltage to the leads off the LiPo charging board. When I do that the installed battery runs it just fine, turns off and on and keeps powering the whole circuit, until it's plugged in again, then the problem returns. I'm really hoping it's not the charging board that is the problem as getting it back out of the model will be a pain in the butt. Thanks in advance for any help!
All LEDs are 20mA, the Red LEDs are 1.77Vf (measured) the white are 3.2Vf
Diagram included below:


texts: Adding trigger functionality in for FPGA in ADC capture board

texts:
I'm using the LM97600RB board from Texas Instruments to capture data signals and this board contains an ADC as well as a Virtex-5 FPGA. I'm trying to add a trigger functionality to the board using an external trigger. The way the board works is that the the data is acquired by the ADC and then sent to the FPGA where it is received by GTX Transceivers and stored into internal BRAM blocks. From what I understand of how the trigger works, the data keeps being captured continuously by the ADC, but the trigger functionality would only kick in when the data is being stored. Am I right in that assumption? Maybe I need to keep checking the trigger and only when the board is triggered, I allow the data to be stored inside the internal RAM of the FPGA? Or is there an alternate way to do this?

If my thinking is right, when the the board is triggered, and the data starts being captured, I lose a few data samples due to the delay in the trigger registering and then the data being stored. How do I overcome this? Even a few nanoseconds of data is important in this case.

Appreciate any ideas on this.


texts: How to reverse engineer controller outputs of a sprinkler control box?

texts:
I want to replace the controller of a sprinkler control box with my own design, while keeping the backplane and module(s).  The controller has a 14 pin ribbon cable connection to the backplane and 4 of those pins are feeding power to the controller from the backplane.  The remaining 10 pins aren't powered without the controller connected and show 24VAC when the controller is connected. Using an oscilloscope, I've monitored the pins when changing the sprinkler zones, but haven't been able to figure out the control signals (the pins are always 24vac when I measure them regardless of what zone is on).  Since it is AC, I really don't know where to go from here (if it was DC I might have a better shot). I'm assuming the signal changes too fast for me to see on the oscilloscope. Is there something I can use to 'watch' the connections?  (Maybe cut the cable and add a circuit/monitor??)  Is there a better method?

I've also searched for schematics of the controller, but haven't come up with anything useful.

Controller: The back of the board has traces and a reset switch, but no other components.  On the ribbon cable: Pin 1 is one phase of the 24VAC and pins 2,3,4 are the other phase.  There's a 9V backup battery that isn't present and isn't required for operation.  The 6 pin connector goes to a rotary switch that makes controller selections.

Backplane:  A 24VAC wall transformer feeds the backplane with the two orange and single green wires. The yellow wire is a jumper for an uninstalled rain sensor (rain sensors are a normally closed switch).  I've (poorly) soldered the module to the backplane so it stays connected while it is out of the cabinet.

Module:  The module has 7 outputs.  There is a single solenoid valve wired to the module (the black wire with white stripes going to the screw terminals).  One of the outputs of the module is always on and the other 5 are switched. The seventh connection is for the unswitched phase of the AC.  Three more modules can be added to the backplane.  The controller 'knows' when a module is not installed, but doesn't sense whether or not a solenoid is installed. The smd (transistor maybe??) is labeled 5D with a sideways 'p'.  The triad is labeled PJ 600E BT134 A1449 D6.

simulate this circuit – Schematic created using CircuitLab

Update: I tried to make my first schematic with the module soldered to the backplane and the solenoid still attached.  I've updated the schematic with my second attempt (I probably have the triad oriented incorrectly).  I'm using continuity on my multimeter to figure out connections.  Now that I might have the module schematic close to correct, what makes the outputs turn on (trying to avoid the randomly applying power and burn it up method)?

Just to clarify what I mean by common output, is it is the second leg of the AC.  All other 6 outputs are the opposite leg of the AC.  I'm not sure if I am using common output correctly.


texts: Piezo into 0-5V ADC, with offset center voltage?

texts:
I want my piezos to have a center voltage at 2.5V for a 0-5V ADC input on Atmega328, so it can sense force in both ways - one way would be >2.5V and the other will be <2.5V.

Will this circuit work? Or any improvments?


texts: How to configure a clock rate of 50 Hz with a prescaler with TI Microcontrollers?

texts:
I need to configure a display that updates its values with f = 50 Hz.

Since the CPU works with 16 MHz and the prescaler has a max. value of 256, the min. clock rate I can compute is 62.5 kHz.

How do you go about this? Do you concatenate several timers? If I would take the output of Timer0 and put it into Timer1 with another prescaler of 256, I would get 244.140625. Timer2 and another prescaler of 5, would result in 48.828125 Hz, which would be acceptable. Is this how you do it or is there an easier and better way?


texts:
I've got a request to fix a snafu made by engineering when they designed this layout.  The end-user wants 3 lights that monitor the voltage status on each of their phases to ground (neutral is bonded to ground in the panel).

Since the incoming utility is 208/120Y, they just connected a 120VAC light from each phase to ground and called it a day.

However, we include transformers (labeled XRFMR) for control power in our cabinets for (somewhat) isolated control power.  Most of you will see the issue right away here...  Whenever they lose A or B phase, the voltage will backfeed through the primary of the transformer and keep the phase light illuminated.

I've been wracking my brain here on simple solutions, but I can't come up with anything that gives us individual lights for each phase.  There are numerous phase-loss relays out there that monitor all 3 phases and give you a single NO/NC contact, but nothing with a contact per each phase.

Any ideas?


texts: how to increase input impedance via bootstraping?

texts:
According to theory in order to increase the input impedance bootstrap capacitor is employed…which couples the same output voltage to point B ..and as the circuit is a voltage follower Vin = Vout ..thus the voltage difference across R1 is very small ..which means that no or very little current will flow through R1 ..which can be also visualised as a very high resistance present..

Analysis:

Without bootstrap capacitor Cb:

Zin = R1; figure 1..

With bootstrap capacitor:

Zin = (1+Aol)R1 ....where Aol = open loop gain of opamp.

As its clear from above equation that input impedance increase by a factor of (1+Aol)..

since from figure 1. we have

i1 = V1/R1 = 500mv / 68K = 7.35 mA.

from figure 2 ..we have

Zin = (999.996 - 999.998)mV / 7.35mA (forget Zin = (1+Aol) R1 for the time being)
= 2.72* 10^-4 k

But the value of Zin should be very 2 large ..but is not agreeing with the theory.. why?? please justify..


texts:
Lately I've been doing a lot of work with Intel HEX files. I want a program that can import an Intel HEX file and allow me to view the byte contents at each address.

There are a handful of programs I've seen that do this, but are there any that are good which are free and also allow you to see the contents at an absolute address, not a relative address to the start of the hex file (for example, if the Intel HEX file starts writing at address 200, the application should signify that addresses 0-199 are blank and not show as if it starts at address 0)?

The best tool I've found is not really a tool meant to view HEX files, but Segger's J-Link Flash programming software. It's really meant to program chips, but it reads HEX files beautifully. Find it at J-Link / J-Trace Downloads.


texts: Linear actuator suggestion - fast , powerful and small

texts:
Suggestion for linear actuators?
Some desired specs

Very fast [coompletes forward motion in 10-20 ms
Just a pulse reaction needed - Can move forward with great speed
Backward thrust not needed; can be done manually
Power available: 12 V, 1 A or similar
Can be electrically triggered actuators
Small [About 1/4th of hand]

Suggestions are welcome on DIYs and products.

Thanks!


texts: Physically, what is and how to, make an anti pad?

texts:
Consider the following later stack (it's only the top 3 layers of an 8 layer board)

Top Signal Layer
Plane
Signal Layer

I have a high frequency trace that is being routed on the top layer and I need to route to layer 3.

I was reading in ( I don't even remember which book anymore), that the return path will only be the surface of the plane due to the skin effect, and so the return path for layer 1 is the top of the plane and the return path for the layer 3 is the bottom of the plane.

In order for the return path on the top plane get to the bottom plane when the signal goes from layer 1 to layer 3, I need to provide some controlled way for the return current current to get there.

There were a few ways, but one of them was to use an anti pad. From the image in the book, it looks like a via with a giant hole surrounding the barrel of the via.

What is the physical geometry that makes an anti pad ?
How do I make one in CAD ?

Added

Electromagnetic Compatibility Engineering - Henry Ott


texts: Questions related to the calibration of a VNA?

texts:
I am seeking answers to these two questions related to the calibration of the VNA.

(1) What type of VNA calibration is required to measure the reflection, transmission, and phase of an attenuator?

[My Answer] Full two-port calibration, that is, TOSM type utilizing a calibration kit: "through", "Open", "Short", and "Match". Am I thinking right?

(2) Now instead of an attenuator, I have a termination. Then, what type of calibration would I need to measure reflection and phase?

[My Answer] one-port calibration, like, OSM type utilizing a calibration kit: "Open", "Short", and "Match". Am I thinking right?

Thank you in advance.


texts:
I have a project where I need to talk with 2 devices x & y with 125kbps and 500kbps CAN speeds respectively.
So I selected an MCU (F446RC) with 2 CAN controllers from ST. The BOM cost went up and I'm not able to meet the target cost.
Is there a way to handle 2 speeds on same bus? or please suggest any cost-effective method.


texts:
uC: PIC18F46K20

I want to scan, in a loop, different ports and test different pins on each port.

I have different target boards so I want to be able to quickly configure each board in CONST arrays. So I created arrays like these:

const char my_ports[4] = {PORTB, PORTB, PORTD, PORTA}; // <- this is the PROBLEM causing line
const char my_pins[4] = {3, 7, 1, 4};

in order to be able to scan those ports in a loop:

// NEW version of the func.
void pin_update(void)
{
  for (k=0; k<=3; k++)
  {
    if (my_ports[k] & my_pins[k])
    {
     // and actions here ........
    }
  }
}

But compiler comes up with an error :

        "my_ports[] ... constant expression required"

I used the approach of passing the port name (eg. PORTB) in previous version of the code when each pin was tested individually, eg. :

    pin_update(PORTB, 3);
            // ...
    pin_update(PORTD, 1);

// OLD version of the func:
void pin_update(char prt, char pn)
{
    if (prt & pn)
    {
     // and actions here ........
    }
}

and all was OK and code worked properly. But as you see PORTB is hard coded in a parameter list. And now I want to run the above 'pin updates' in a loop.

So problem came out when I wanted to list port names in CONST array.
I tried various things with casting to ports' addresses etc - nothing worked. Compiler still did not like it.


texts: Why is the brightness of my red LED slowly decreasing?

texts:
I have a RGB LED for photo-detection in my design with each color controlled by a MOSFET to manage light intensity of each color. The green and blue LEDs work great, but my red LED appears to slowly fade out over time. I measured my forward voltage (Vf) to be 2.6V on the red LED at the beginning, but it drops to ~2.56V over the next few minutes (in spec).

Here's my schematic. The left is my tricolor LED and MOSFET set-up and the right is the PWM expander, controlled by I2C:

PCB:

Here are the specs for my tricolor LED (I circled the correct one):

When I measure the light intensity coming from the LED over time, I can see the red intensity dropping while green and blue stay steady. Can a solder joint affect the LED? I wouldn't have thought twice about this, but I have an extra RGB LED so I removed one of my old (dead) ones and connected the LED with wires instead of soldering to my board. I have the LED on 'red' and the intensity isn't going down.

This has happened to 4 LEDs now...