texts: How does length affect current carrying capacity

texts:
Will a wire have increased current capacity if the length is sufficiently small?

The reason I'm asking is that when doing PCB layout the vias often has thermal relief, which are small traces going from the via to track/fill around. But I've heard that because it's so short it doesn't really matter.

Is this true and can it be further extended to very short wires, or must you follow the rating of the wire?

If possible, how would one 'prove' that the wire can actually handle the current?


texts: Connecting a LED between two 74HC595 without current limiting resistor

texts:
I am trying to control RGB LEDs using 74HC595s. Three of them determine the input voltage and one of them determines the ground.
Here is what I found while seeing the answers to a slightly similar question

The 74LS04 have internal resistors to reduce the shoot-thru current.
When that pin is driven high, the Vbe and Resistor limit the current. Is that
resistor designed for permanent heating? Those pins are short-circuit-proof

I want to connect the two 74595 together with a LED in between without a current limiting resistor since I believe the buffers have an internal resistor connected to the upper MOSFET in the totem pole

simulate this circuit – Schematic created using CircuitLab
LED ratings:

Max current = 25mA
Typ. Vforward R = 1.95V
Typ. Vforward G = 3.3V
Typ. Vforward B = 3.3V

I have searched through the documentation but none of them shows the internal structure. What is your opinion about not using the current limiting resistor?


texts: I have an alarm clock that beeps at a known    time. I wish to power a motor every time it rings, but the problem is that there isn't enough power to turn the motor. I attempted to connect a wire in parallel to the wire that connects the circuit to the beeper though that still doesn't work. When power is applied this way , there is still somehow a voltage drop and the beeper cannot beep as loud and the motor is unable to turn (I tried in series as a desperate attempt). What I am trying to achieve is to power an AC motor from a weak "signal pulse". Any suggestions how to do this? Do I need some form of relay?


texts: Why must USB low-speed devices use a captive cable?

texts:
The USB 2.0 spec says: "A low-speed device is required to have a captive cable." However, I can't find a good explanation for why this is the case. I have seen hints towards two possible explanations:

To prevent users from accidentally using a (non-captive) low-speed cable with a full-speed or high-speed device. However, there is an error in this logic: To achieve that, the spec would only have to demand that low-speed cables must be captive. It would not have to demand that low-speed devices use a captive cable, the difference being that a low-speed device could use a non-captive full/high-speed cable.

Differences in cable capacitance. Section 7.1.2.1 says: "A low-speed device (including cable)
may have a capacitance of as little as 200 pF and as much as 450 pF". Unfortunately I found it hard to find numbers for high-speed cables. Things get more complex because different cable lengths exist, but then, I don't understand why the spec disallows using these cables altogether instead of saying, if a low-speed devices has a B-receptacle then it must handle all standard cables, and only if it can't do that a captive cable is required. Also, in case standard cables have a capacitance that already exceeds 450pF (as noted, I don't know the actual numbers), then hub drivers are strong enough to handle that because they must (for fullspeed), so they could do the same for lowspeed -- and for the device, again, a captive cable could be required only if its driver is too weak for the capacitance range of standard cables.


texts: How to build impedance over frequency bode plot (LTSpice)?

texts: I need to build a bode plot that would show impedance curve of a simplest circuit for a frequency range of 0 to 20kHz. Apparently the x axis should be frequency, y axis should be impedance. I'd like to build one plot for impedance value and another for the phase. I'm using LTSpice IV at the moment.


texts: Solar panel system - figuring out the right specifications

texts:
I'm building an off-grid security system, based on a smartphone as a 24/7 security cam and an arduino nano for several sensors. A pretty interesting build in my opinion, maybe I'll post about it sometime.
But I'm struggling trying to calculate the required values for my system. The three things I need to find are:

Battery capacity
solar-panel wattage
charge-controller

Information I have:

The smartphone running in camera mode is the main load, the arduino is pretty negligible. I'm using a Samsung Galaxy S4 with a battery of 2600 mAh capacity. I tested it and found that it lasts 3 hours for a full charge. The phone's regular wall-charger is 5v\2A.
I actually tried to run it with an old solar panel system I got from a friend, which uses a 12v 7Ah lead battery and this set of 10W panel and a 3A pwm charge controller. I used a car-usb-charger (to convert from the 12v on the load output pins on the charge controller) and it didn't hold very long, only for half a day or so.
I live in Israel so at the very least 6 good strong sunlight hours a day.

Here is my attempt for some calculations:
2600mAh battery consumed in 3 hours can be rounded up to a 1Ah load (or, since it is in 5v, to a 1Ah*5v=5Wh load), so overall the system consumes 24A daily (or, 120W). Therefore a battery with 30-50Ah capacity is suitable, and a 30W-40W solar panel will do (since 30W*6h = 180Wh daily output). If this is correct, I'm thinking about buying a 30W solar panel, a 10A PWM charge controller (with 5v/3A usb outlet which is really good for my needs) and a 12v 40Ah Deep Cycle Lead Acid Battery.

Am I doing it right? Is this correct?
Please share your knowladge.

All the best,
Roei.


texts:
Here I am not using any RS232 or RS485 protocols. I will transmit analog square signal of -12 to +12V and also receive the -12V to +12V signal. So I have a circuit which can transmit and receive the signal individually.
2 circuits are constructed the schematic is attached below.
The process is
First setup-1 will transmit the signal for T1 time period then after T1 period it will not transmit it will be in idle state i.e. 0V for T2 time period, in this T2 time period, the setup receive the signal and transmit the signal to setup-1 for T1 period in T2 period only. After that the setup again transmit the signal for T1 period and Setup transmit the signal for T3 period .. so on it will continue.
In this testing i have  faced a problem that when both setups are connected each other and while doing the above testing process , the oscilloscope was connected between 2 setups for observing the voltage.. here the voltage which should be -12V to +12V it was dropped to -6 to +6V ..
can anyone please suggest any solution to this issue i.e, voltage dropping issue


texts: I have this multiplexer and decoder that I want to draw their truth table

texts:
I have this circuit where I want to draw it's truth table. In fact I am new to this, I used to have the truth table and make the circuit. Can someone give me hand in how I should do it?
I drew the truth table with the inputs and since I have 4 inputs and a 4-to-1 MUX I should divide the output of the truth table in 4 groups. If I had only the MUX it would have been easy for me, but putting the decoder there, things got a bit complicated there.

This is my truth table and that is what I meant by dividing the output(neglect the 0's). Each part of the output, I guess, is dependent on each input of the decoder. So any help would be appreciated. Thank you.


texts:
I have an LD1117V33 connected to a 12V powersupply. When I plug the output to my osciloscope I see about 280mv peak-to-peak voltage, sometime more.

Is it normal? Is there anything I can do to improve it?

My circuit is pretty simple. 12V - LDO - Output with 2 capacitors in parallel in input and output. 100nF input and 10uF output.


texts: Can binary code such as an embedded OS or user application code be stored using silicon physical gates

texts: Hello as the questions describes I'd like to know whether it's possible to do this ? Can binary executable code which is executed by a processor core possibly be stored using physical silicon gates ? I understand that a device's OS or user application code can be stored in ROM or EEPROM or in flash memory but is it possible to store using physical silicon gates only ? Similarly can a ROM Boot loader be stored using physical silicon gates instead of ROM or flash memory ?[UPDATE] Can binary code be stored on the same area of the die used to represent the core (CPU) design structures ? So using logic gate transistors but not using combinational logic gate transistors (ROM) and not using floating-gate transistors NAND and NOR logic gates (flash memory) and not using floating-gate MOSFET (EEPROM) ?


texts:
i'm searching for a specific answer about the writing personal data to RFID TAG (mifare 1k). But i could not find anything.
Does the chip perforfing a "read back" verification after writing a block? Or it is something that must to do myself?
If not, how can i verify if the writing method of arduino library does it?


texts: Types of Magnets to use for Bluetooth and electronics circuits

texts: I am working on a project requiring Bluetooth capability. In order to make it convenient, it would be great to have a magnet in order for it to stick to things. I was just wondering if it is possible to use a magnet without damaging or affecting the electronics. Is there a magnet type that could be considered?


texts: Why is there an additional resistor in this phototransistor circuit?

texts:
I'm currently working on a phototransistor that is part of a reflective optical sensor.  Now I saw a circuit, which looks like this and I'm wondering why there is the (additional) resistor \$R_3\$ ?

In my understanding the usual phototransistor circuit is a voltage divider between \$R_2\$ and the resistance of the transistor (i.e. low illumination \$\propto\$ high resistance and bright illumination \$\propto\$ low resistance). Then the analog output of the circuit will read a value between \$VCC\$ and almost zero (determined by the dark-current).
However, here I cannot explain to myself why we have the resistor \$R_{3}\$ in front of the analog out?
Thanks for your help!


texts: Will a capacitor draw charge/current if it's not feeding a load?

texts:
I have a number of capacitors connected in parallel, as in the following circuit:

simulate this circuit – Schematic created using CircuitLab

If the switch is open, will the caps still draw charge/current?
Will this only happen when the load draws current from/through them? (Is the load required for the caps to charge?)

I have a basic understanding of how caps work and don't have an LCR meter or scope with which to test this.


texts: How can I reduce the size of an AVR ethernet bootloader?

texts:
I am writing an ethernet capable bootloader for an AVR ATmega328 MCU. I am currently running over the 4k size limit and need some design advice.

Bootloader requirements:

Needs to be able to update the application via a simple UDP based messaging protocol (similar to TFTP).
As the device operates in a variety of LANs, it should support DHCP.

With my current code, I need about 4k for the Ethernet driver, DHCP, ARP and UDP support.
Plus 1.5k for the actual messaging and app programming.

Compiler optimizations are turned on.

My current considerations to proceed are:

The code is not particularily optimized, so I guess I could save some bytes by following AVR035. I doubt I can save enough code size going this route though.
I could simply extend the bootloader area by reserving 2k from the top app memory area for the bootloader. I need to be extra careful then to not overwrite that area when programming though. And, I would end up with a large, complex bootloader which probably has bugs, which I cannot update in the field.
I could move some functions from the bootloader to the app. DHCP could be a good candidate: The app obtains a IP address via DHCP and stores it into EEPROM. The bootloader then can simply use the stored IP address and does not need to do DHCP itself. This could be dangerous though if the app fails e.g. by software bug or random corruption.

Which route would you suggest? Are there other ideas I should consider?


texts:
I am making an IMU for 6DOF which has L3G4200D 3-Axis Digital Gyroscope.

I've checked so many Blogs, Forums, Application notes and have programmed accordingly to get the proper reading/information from my gyro.

Though I am very near to solve it - a single problem has made me mad since last two nights!
I've 16 bit digit - 1 signed bit + 15 bit value

Suppose I want to measure an angle with respect to X-axis at 2000 dps, for that I am doing the following:

while(1)
{
     for(g=39;g<42;g++)
    {
        r = I2CRegRead(I2C0_MASTER_BASE, 0x68, g);  // read the reg. no. g
            switch (g)
            {
                case 40:
                l = r;             // LSB part of X_Gyro
                    break;
            case 41:
                h = r;            // MSB part of x_Gyro
                x = 0;
                x = h<<8;
                x = x|l;
                x = x*70/1000;
                        UARTprintf("Gyro_X : %5d\n\r",x);
                    break;
                }
         }
}

I am getting some values most probably <800 when I move gyro in counter clock direction with respect to X-axis and getting >4000 for the opposite direction!!

I want to have positive angle values while rotating it on counter clockwise direction and negative angle values for the clock wise direction... For that what I should add on my calculations?? [Angles should be in degrees 1 to 180 & (-1) to (-180)]

// in code 0.007 is in mdps which is the value of each LSB of gyro's data

What I should add in could and why I am having >4000 & <800 values right now?

Could anyone please help me with this?

Thank you so much for your valuable time.


texts: Why does my wave signal from AD9850 / AD9851 DDS get cut off?

texts:
I have the AD9850 and AD9851 version of this board.

I have written the necessary code to interface these with my microcontroller.

However, when I sample the sine output signal from the DDS it gets cut off like this:

I have connected the wires like this:

GND <-> uC GND

D7 <-> uC GPIO

WCLK <-> uC GPIO

FQUP <-> uC GPIO

REST <-> uC GPIO

Vcc <-> 3.3V (Tried 5V as well)

V-ADJ <-> uC GND, Not Connected and different values between 0V and 3.3V has been tried.

I have been trying with and without jumper J3 and J2. Trying to change the potmeter etc. But there is no change except for when I use a DAC and send a few hundred millivolts signal in on V-ADJ, then the signal gets attenuated and eventually zero. I have not been able to increase the signal amplitude or change its offset so the signal don't get chopped.

The sine signal is directly connected to the microcontroller ADC pin.

I am running out of ideas and are therefore asking for help/tips/experiences.

I should have had an oscilloscope for debugging this signal, but none available at the moment.

The schematic is:


texts: Switching Between PoE and Power Input of DC 8-36V

texts:
I am Planning to use PoE+ PD in my design. I have a DC power input option other than PoE which will be in range of 8-36V DC. I am planning to use one PD module with Integrated DC-DC converter which will give me an output of 12V DC Via PoE. The DC input (8-36V) of my board is connected to a wide range input regulator (Buck) and it will give 5V output. From this 5V, I will be powering all the peripherals in the board. I am also planning to connect the 12V from PoE to the same regulator Input.
In the above situation, IF DC input alone is there, then board will work fine and PoE alone is there then also board will work fine. If Both DC input and PoE voltage is available to board, then it will get short the both rails. I want to add one switching mechanism to select the voltage source either from DC input or PoE. I will get Power detection signal from PoE PD module if Power is getting from the PoE.
Can anybody suggest one switching mechanism with below functions

When DC Input alone is there, Board will be powered from DC input
When PoE alone is there, Board will be powered from PoE
When Both PoE and DC input is there, it will be powered from DC input (PoE power path should be open)

Regards,
Shafeeq


texts: Battery with high risk of being exposed to fire

texts:
I'm currently working on an electronic design which has a high risk of being exposed to temperatures up to 500°C and possibly more.
The specifications indicate that once the product is exposed to more than 80°C it needs to be replaced by a new one, so the electronics don't need to be qualified over typical industrial range temperatures.
I still have a problem with the energy source. I don't have big hopes that the client will let me design a system with a wireless charger linked to the standard power network, so I need to come up with ideas about batteries that will not explode when exposed to fire.
I need 2.5V or more, for 1 Ah.
Do batteries which won't explode exist/are currently publicly available or should I ask for help about thermal isolation to slow down the temperature rise for hours?
My electronic device is supposed to sense different parameters (like pressure, shocks,...) and log data  locally to be gathered regularly through NFC. For the enclosure, I could say based on the mechanical model I got 50x100x100 mm. Expected operating time is 6 months.


texts:
I am working on a project where I am using a microcontroller to control a 5V DC relay to control a mains device (an airconditioner).

In this circuit, I would need to connect the AC wires to my PCB at sereval points:

as an input to a 12V transformer -> 5V voltage regulator
to the 5V DC relay

My questions are:

How to ensure the safe connection of the mains wire. After soldering them to the PC is there some kind of glue or something i can cover the solder with to ensure safety ?
Do i connect all the grounds (AC ground , micro controller ground) together or should they remain separate?
while designing PCB what do i need to keep in mind for the track widths for tracks handing AC current/voltage ?

Sorry if these questions sound newbish .. first time handling AC/DC together.


texts: MAG3110 and MPU6050 on one I2C bus connected to a Raspberry Pi

texts:
I am trying to use separate pre-built breakout modules containing a MAG3110 (Magnetometer) (module) and a MPU6050 (gyroscope) (GY-521 module) on one I2C bus connected to a Raspberry Pi. Although both devices have different addresses (0x0e) and (0x68), I cannot get them both working at the same time.

If I connect each of them alone, both work perfectly. If I connect each of them together with another module (PCF8591 ADC + DAC) on the I2C bus, everything is fine.

However when both MAG3110 and MPU6050 modules are on the same bus, I only see the MPU6050 (0x68) using i2cdetect.

Does anyone have an idea what is happening here?


texts: I found this question  is a very interesting one but I don't know how to approach it since I never dealt with inverters. Can someone give me hints ? I found it very confusing that two switches has switching frequency that is different than the other two switches. Also what is the purpose of the inductors at the output side? I am not looking for answers to this question. I just want ideas on how to approach this question so I can research more on them.


texts: 2's complement only works in one direction with the LSM303DLHC

texts:
In java I have the code

public void readAccel()
{
  int l, h;

  l = i2c.read(0x28);
  h = i2c.read(0x29);

  int x = ((h) << 8) | (l);
  System.out.println(x);
}

in java. The accelerometer I have connected is working and communicating over i2c, the problem being that the two's complement number that is generated only seems to work in one direction; when I turn he device to one side the values scale from 0-256, but past zero the value jumps to 4096-3840. What Am I doing wrong?


texts: How to connect Arduino Uno to an energy meter

texts:
How do I connect an energy meter, such as the L&T (Larsen & Toubro) Quasar Intelligent meter (datasheet,) which uses Modbus RTU protocol with RS485 communication to an Arduino Uno?

I am using MAX 485 to convert RS485 to TTL and I have written my program using the ModbusMaster library.

I always get a Time Out error or Slave Id error. Please help me out of this situation.


texts: Evaluation of the dominant mode in a waveguide

texts:
In a waveguide, the dominant mode is defined as the propagation mode with the lowest cutoff frequency.
Now let's consider a structure in which the lowest cutoff frequency occurs for two different propagation modes (for instance TE10 and TM10): in this case, which is the dominant mode? Will exist both simultaneously?


texts: How to draw a circuit diagram to check a 4 bits number is odd or even

texts:
Like the title, anyone know how to draw a circuit diagram to check a 4 bits number odd or even ??
Update:
Here are my truth table for my solution:

A B C D Output
0 0 0 0  0
0 0 0 1  1
0 0 1 0  0
0 0 1 1  1
0 1 0 0  0
0 1 0 1  1
0 1 1 0  0
0 1 1 1  1
1 0 0 0  0
1 0 0 1  1
1 0 1 0  0
1 0 1 1  1
1 1 0 0  0
1 1 0 1  1
1 1 1 0  0
1 1 1 1  1

Due to the output is odd or even is depend on the LSB. So D colum = output. Im i right? If so how can i draw circuit base on this truth table? Im gonna use Sum Of Product method but not so sure how to use in this case 0 and 1 and 0 and 1......


texts: Big code in interrupt freezes main function

texts:
I'm writing firmware for an ATSAM4S (runs at 120 MHz)and I noticed a strange issue with ADC interrupt handler.
I set up ADC at 20 MHz, 5 enabled channels, and DMA transfer complete interrupt. According to calculations interrupt timing is fine. It triggers when 5 conversations are completed.

I don't have any code to post at this moment but my question is quite clear.
I have a print function which prints out to a UART port the result of ADC (for debugging), in an infinite while loop.
I noticed that main function (print out function) freezes completely or slows down when I put too many lines of code into the interrupt handler of ADC.
By too many lines, I mean further processing of ADC results like calculations of mean value, calculations of mean value above and/or below of a specific threshold, in all channels...

Does that mean that ADC takes too much machine cycles that once it's finished, another interrupt is waiting to be carried out (due to next conversion) and it fires immediately the interrupt handler before any piece of code executed in main function?


texts: FTDI ft232rl 3.3V logic interfacing PIC microcontroller

texts:
I want to interface a ft232 with PIC16F73. I am using the circuit below:

VCCIO is connected with VCC which is 5V. Then I think all logics from TXD,RXD will be 5V, isn't it?
If I connect VCCIO with 3V3OUT then what will happen? will RXD,TXD be 3.3V logic?
Is there any problem if I connect VCCIO with 3V3OUT, PIC16F73 is powered from 5V. I am newbie in electronics so forgive me if the problem is too easy.


texts: Why does my multimeter capacitance measure not show up until I lift the probe?

texts: I am testing a simple homemade parallel capacitor with tin foil. My plate distance is about an inch. the plates are hooked up to a battery. When I touch my multimeter probe to the plates nothing shows up. However, when I pull one of the probes away, an nF reading will show up for a brief moment. I have to continually touch and lift the probe to get the nf reading. Why do I have to lift the probe to get the reading? What is going on?


texts: Deriving The transfer Function of a high Pass active second Order filter

texts: I have recently been trying to solve this transfer function an my professor keeps saying I have been doing wrong and I finally need help. I know my Gain is \$1+ \frac{R_A}{R_B}\$. but I keep getting extra stuff in my numerator. also I need to design it to 1 kHz cut off frequency. I test the transfer function out by using Matlab and seeing where the highest dB it can reach.


texts:
I have a hand-wound coil I'm using in an LC Tank circuit. Using my multi-meter, I found out that the coil is drawing .6mA at 9v. Using Ohm's Law...

$$R = V/I$$
$$R = 9/.0006$$
$$R = 15kΩ$$

Is there a way to calculate the inductance of my coil from the DC resistance?


texts: Why usb to serial port converter can’t program avr microcontroller?

texts:
With a serial port or parallel port in pc programming avr microcontroller is very easy and cheap. Problem is, no modern computer come with serial or parallel port. So, usb to serial converter should be the solution but unfortunately not.

There must be a difference between the actual serial port and converted serial port. What is it?

Another related question would be, how USBasp communicate almost directly with pc? I thought most or all of the microcontroller of ATmega series microcontrollers are without usb support.

I have checked this link-
AVR programmer with serial to USB converter

I know there are several question like this but being new to embedded programming I need an easy explanation to get the concept. Thanks.

Edit:
I want to use a circuit as below with the converted serial (possibly, RS232) interface.This circuit is designed for actual serial port.With a converted serial port, I might be able to reduce some complexity of the circuit.

The detail can be found at Simple Serial Programmer for AVR


texts:
There is a 24V 50Ahr battery unit.

An smps voltage regulator converts it to 5V and couples to a device. This 5V drives 100mA constant current.

So to calculate battery life roughly, should I use currents or powers delivered?

Is the answer: using current transfer 50A/100mA or using power transfer (24V*50A)/(5V*100mA)?


texts: Will a trickle charge lead-acid battery system last?

texts:
If I were to implement a simple battery backup system like this to power several WiFi radios in a field situation, how would the battery handle it? Would trickle charging it like that wear it out after several months? Or years?

For example, the system could have power for perhaps three or four months, and then need battery backup for half an hour if the mains power went out.

I have seen some battery systems that monitor the battery's charge, and when they do charge it, they use a pulse system.

Do I need something like that? Or will this simplistic approach be effective?

BTW, this is a standard 12v Lead-Acid battery like from a UPS.

simulate this circuit – Schematic created using CircuitLab


texts: Use a TRIAC to connect/disconnect a capacitor to a PSC motor

texts:
In the image above, we see a PSC motor, with its 3 terminals, connected to a control board.
This board has a RUN capacitor always connected to the motor. When the motor has to turn, the board applies 230V AC between the COMMON line and either the FORWARD or REVERSE line. The relevant winding is powered directly, and the other winding gets powered via the RUN capacitor, with about 90 degrees delay. This makes the motor run in one of the two direction.

What I want to do is to connect, in parallel to the first, a second capacitor in order to boost the torque (when the motor is starting). After a little time the motor is started, this added capacitor should be disconnected.

I would like to use a TRIAC instead of a relay. Can anyone point me to choose the correct device, and give any warning I may need? I've already tried, but the TRIAC fails in short-circuit without heating or other signs (the real schematic is not simple as the one above, but the concept is exactly that).

The motor is about 1kW, @230V; the capacitors should be about 25 uF each. The current is about 1A continuous but it can rise to 4A when the motor starts or when the load gets heavy (I'm using a workbench brake for testing).

EDIT: The driving part is like this:

Basically, the 2nd capacitor has a series triac; the triac is gated by a MOC, taking current from A2 (MT2); the resistor from gate to A1 (MT1) is optional.

The Triac goes short-circuit, but the MOC keeps to work. The capacitors, which are normally used and considered reliable, are rated 470V. My triac is an ST, snubberless, rated 1200V and 16A (continuous). There is something I don't grasp...


texts: How to tell if a printed capacitance is the actual value or a capacitance code?

texts:
My confusion was inspired by this question.  The OP asked to identify an electrolytic surface mount capacitor and its ratings.  I answered assuming the pictured capacitor's capacitance was a three digit code.  I made that assumption from previous purchases I've made where the printed markings were three digit codes.

Other posters said that the markings were the literal values.  I looked it up and indeed many electrolytic surface mount capacitors are marked with the actual value.

My question is for electrolytic surface mount capacitors how can one tell when the value marked is a three digit code or when is the mark the literal value?


texts: Is a pull up/down resistor really necessary?

texts:
Logical reading (1 or 0) of a micro-controller input GPIO pin may float if it is neither connected to VCC nor GND; someone said it is because of surrounding RF interference.

When a floating GPIO input pin voltage is affected by RF interference  that makes it fall in the undefined logical range (i.e. 0.8V - 2.2V for Raspberry Pi), it can cause the logical value of a floating pin to change.

I wonder if this problem could be solved by how a microcontroller is designed. i.e. Enlarge the logical voltage range, say <6V for low >6V for high. Since interference may seldom reach such high level voltage.


texts: Bluefruit ezlink is not accepting my sketch

texts:
I have recently purchased both a new Arduino Uno and a new Bluefruit EZLink shield.  I am able to upload sketches to the unit via USB (with the selector set to "soft").  I can pair with the unit and use the serial monitor to send data back and forth (with the selector set to "direct").  What I can not seem to do is upload a sketch to the unit over the bluetooth link as described in the features for this shield.

The response from avrdude that I get is this:

avrdude: Version 5.11.1, compiled on Apr 28 2013 at 18:46:46
     Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
     Copyright (c) 2007-2009 Joerg Wunsch

     System wide configuration file is "/usr/share/arduino/hardware/tools/avrdude.conf"
     User configuration file is "/home/growlf/.avrduderc"
     User configuration file does not exist or is not a regular file, skipping

     Using Port                    : /dev/rfcomm0
     Using Programmer              : arduino
     Overriding Baud Rate          : 115200
avrdude: Send: 0 [30]   [20]
avrdude: Send: 0 [30]   [20]
avrdude: Send: 0 [30]   [20]
avrdude: ser_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding

avrdude done.  Thank you.

I have tried setting the baud rate to 9600 via upload over commandline, but that does not change the response much.  It almost seems like the shield is not resetting, but I am not sure.  I do see the lights for TX/RX flicker rapidly for a moment on both the shield and the Uno itself, indicating the sketch was sent and some sort of response was given.

I have also (as I have seen suggested in my Googling) pressed the reset button just before and just after transmission - no difference.

Any suggestions or pointers on how to upload using this shield are very welcome and apreciated.


texts: Difference between the following two very basic circuits

texts:
What is the difference between the below two circuits?

I know the bottom circuit has 'ground', but what does that mean exactly? Why would someone want to construct the second circuit over the first? And, what would be an example of doing the bottom on a breadboard -- where does ground 'go'?

Finally, when doing the above in EveryCircuit, the first example doesn't even work, or allow current to flow through it. Why is this? (The same circuit works on my breadboard).


texts: Does mobile charger and buck converter have any basic difference?

texts:
I have a 2 cell(4.2V)/12Ah deep cycle flooded lead acid battery that i usually charge by 5V/2A smartphone charger. By using this charger it takes 200mA current for charging.
Today i got my CC/CV buck converter(laptop charger as source) i set it to 4.6V/1.2A and that charged battery starts to charge at 1.2A.
So how is possible that higher voltage GENERIC smartphone charger charges battery slower?


texts:
Im building a VGA (640x480@60Hz) adapter for my homebrew project but i dont have enought memory to store a framebuffer. Since im using 8 bit memory i plan to do 8 bit color, but 8 colors would be enought for my project.

How is the most efficient way to implement a character mask (8x8 pixels) using only memory and TTL? I was thinking about using a memory bank (6264) to store the character mask, another bank linked to that to select wich mask i want to use in a sequency using binary counters. Then using a PISO Shift Register (74166) at 25MHz to feed a multiplexer (74157) that selects background or foreground color stored at another memory bank. But this seems overcomplicated.

Since only the 74166 and the 74157 would be running at 25MHz i can get off with HC ones? Or better to run with another model (they are harder to find here).

I want to avoid FPGAs. Use only TTL, SRAM and microcontrollers.


texts: How to get a 1 clock period pulse from a constant input?

texts:
I want to make a digital circuit that produces a pulse 1 clock period in duration whenever I see the input to the circuit go HIGH. I only have a flip-flop, an AND-gate, and an inverter. How do I achieve this?

I'm familiar with edge detector circuits like the ones seen here, but such circuits don't necessarily produce an output that lasts for 1 clock period.

My first attempt at a solution was the Rising Edge Detector circuit found in the linked above document. Here's the picture:

However, this circuit will not produce a pulse of sufficient duration:

The stage after this circuit is a counter that should increment when it is enabled by the pulse generated in the circuit to be designed.

Edit: This problem cannot be solved by a traditional edge detector circuit since it doesn't produce a 1 clock cycle duration pulse.


texts: Difference between Shadow register, match register and capture compare register in a timer module

texts: On page 704 of the data sheet of the Texas instrument Tiva C TM4C123GH6PM....it has these three registers in its timer module.i searched about these registers and found that shadow register is a register that holds the copy of a register , match register holds a value and compares the value with timer value and  ccp register also do the same it captures and compares the value with the timer. if what i understood is right then i don't find any difference among these register but they are present.  What is the difference between these registers?


texts: Help me in understanding a flashing LED circuit

texts:
Now we have two circuits one with single npn lets take it as first circuit and another circuit with one npn and one pnp lets take it as second circuit.
when i tried out both the circuits. the first circuit has no output in the sense the capacitor does not discharges.
coming to second circuit the output is the led blink so it means the capacitor discharges
can anyone explain how the capacitor discharges in second circuit and why it does not discharges in the first circuit?


texts:
I'm trying to drive a DC motor using an external voltage source and control it using a transistor switch. It doesn't seem to be working during the simulation though. I know I must be doing something incredibly stupid.

I have it built in circuitlab here.

Thanks


texts: Questions regarding messages for SPI protocol

texts:
I want to use the SPI protocol to communicate between an STM32 and Arduino.

So I made up some message structure where the first byte is the 'command' byte, and  data bytes following. The number of data bytes depends on the command byte (so not all messages have the same length).

Now I have a few basic questions regarding defining those messages:

Can I assume SPI is kind of 100% reliable? (meaning no bytes are lost, the Arduino/STM32 will be within max 10 cm/4 inches difference) ? (if yes, the following questions might be less critical). I don't need a super fast speed.
Is it a good way to have messages of different length? Rationale: When the command byte is not read correct, the number of data bytes is incorrect, and all consequent bytes will not result in valid messages.
To prevent this, should I add some 'end bytes'? Or is there a better way to solve the problem of misreading (e.g. the command byte)? And if the end bytes would be e.g. 255, should I make sure 255 is not used in the command or data bytes?

Or maybe in other words:

What should I change to a simple message structure Command byte - Data byte(s) where the data bytes are varying on the command byte, in case the command byte is received incorrectly?


texts:
How do I read diode numbers. I read that the numbering system for US diodes is the JEDEC system. But I don't think the JEDEC system applies to diode numbers after 1N. Everywhere I look I cant only find a way to interpret the first 2 letters/numbers, and I cant find anywhere to figure out the 4 numbers at the end. Plus, I cant know if the range of numbers I would be choosing is an available part anyway.
Update:
So I now know that the serial numbers on the part number dont really mean anything. So Is there any kind of table that shows a diodes varying currents, reverse voltages, etc... with the part numbers attached to it? If so please include a link. I have not found a table like that anywhere.
If not, how do others go about looking for diodes without any charts or tables.


texts: Precautions when connecting both an inverter and solar panel to AGM deep cycle battery simultaneously

texts:
I am a complete novice with batteries, inverters and solar panels / regulators. I have purchased a 130Ah AGM deep cycle battery, a 500W pure sinewave inverter and 2 x 100W solar panels with built-in solar regulators to take camping.

If I connect both the inverter and the solar panels to the battery's electrodes at the same time (to draw and replenish battery charge simultaneously), are there any precautions that I should take? For example, is it OK for both electrodes to be touching each other?

Is it OK to leave the solar panels connected to the battery after the battery is fully charged or is this one of the purposes of the solar regulator?

UPDATE:

It is a 12V battery. The specifications of the inverter are detailed in this link:

Inverter Specifications

Here is some information on the solar panels both of which are identical:

Here is some information about the built-in regulator:

Here is some more information about the regulator that makes mention of a temperature sensor. Does this appear to serve the purpose that you indicated it should?

Here is some more technical information about the inverter:


texts:
One of the maxwell equations state that the magnetic field induced around a closed loop is proportional to the electric current plus displacement current (rate of change of electric field) it encloses.

It means that either current or change in electric field or both can cause a magnetic field.

My question is that if both current and change in electric field cause magnetic field
then whether the magnetic field induced by a current and the magnetic field induced by a changing electric field will reinforce each other, cancel out, or combine in some other weird way. Please avoid mathematical explaination. Just tell me in simple words the answer of my question


texts: How do you calculate what to frequency to use in the Local oscillator for a 2.4Ghz Transciever

texts:
I am designing a 2.4Ghz transciever and there is a confusion regarding the frequency of the Local oscillator to be used. Should the value of it be somewhere close to 2.4Ghz itself or should be in the Mhz range?
And secondly will this value of the local oscillator change for the receiving part( where down conversion is reuired) and the transmitting part ( where up conversion of frequency to 2.4Ghz is required) ?


texts: Powering a modem over extreme distance (~2k feet)

texts:
We live in a rural area and have about a 2000 foot run from the end of our driveway to our house. The cable company wanted quite a bit of money to run internet to our house, but there's a drop at the end of our driveway, so we convinced them to put a modem there, and are sending the signal over a directional parabolic antenna to our house (which is being picked up by a repeater at the house using a second directional parabolic antenna). That all works great!

The modem itself is 12v, 1.5a, and originally I thought I could get away with having a marine battery and a 30w solar panel. That works fine during the day, but at night, the battery is drawn low enough that the panel can't charge it back to full and power the modem at the same time.

I could upgrade the panel to something which would handle it (around a 230w panel), but I wondered if I could get away somehow with running power from our house to the end of the driveway. I only need to end up with 12v / 1.5a, so I'm wondering if I can somehow get away with 14 awg. I am (obviously) not an EE, but I didn't know if I could use a step up transformer to reboost the signal at the end over that far of a distance.

I'm open to other ideas - we've already called the power company about doing a service pole, since we're about 30' from a transformer. Just trying to understand the calculations on running power long distance, or what else is out there.


texts: An LC-unstoppable noise in a USB-powered device

texts:
EDIT: I found out the cause, see my answer. I would like to thank the commenters.

I am making a USB powered device with a 12 bit ADC, from which I want to get a 8 kHz signal with a precision of about 10 bits. Yet, there is a quite complicated noise in the obtained digital signal, of different frequencies in the audio range, which limits the precision to about 5 bits.

As it turned out, there is also a ~ 100 mV, >= 1 MHz noise on the USB power line, which I guess is the cause of the problems:

So this is yet another question about a USB noise, like this where a DC regulator is recommended or this where an inductance is suggested.

Seemed easy. After a ceramic 1 uF which was there from the start, I tried the following serial sequence:

NCP380LSNAJAAT1G (limit charge current to 500mA).
A large electrolytic capacitor, 3300 uF, too large but it was at hand.
L1117 to trim the voltage to 3.3 V.
A small ceramic capacitor 1 uF.

It reduced the noise on the power line by about 20%. The other effect of the filtering above was, that in the data from the ADC some low frequencies ~ 50 Hz disappeared, but some higher-pitched noise is left:

The precision is now ~ 6 bits, a single bit better than before.

I did not yet try an inductance, but this guy did and it reduced the noise from 100 mV like in my case to a sparse 50 mV. I am not sure if this will help in increasing the precision from 6 to 10 bits. Also, see p. 1 in the list below.

Can it be that this signal does not really come from the power line? There is an off-the-shelf microcontroller board with MK20DX256 in the same circuit, working at ~ 100 Mhz, and the power line noise is present only if it transmits the digital signal to the host. And thus it can be some interference in the cable and/or in the device, picked by the power line but also individually by different parts of the device.

Here is the simplified circuit:

Inputs of LM358 are connected as follows now: plus to a voltage divider, minus to an analog signal with a floating ground.

As seen, the microcontroller board is connected directly to the USB power, but:

The board has an LC filter and a 3.3 V regulator, but despite that, its Vout is about just as noisy as that from my filter.
Its ADC has internal Vref. I do not know, though, if it helps with such a power line.
My power filter is not effective anyway.

I could use a special, external, shielded ADC together with a more complex LC than that in the link above, but I only want 10 bits of precision. Would it all be really necessary?

Is there a compact solution to the problem? Or should I just power the device from another, clean source?


texts: I have designed a circuit by System Generator to implement on FPGA. The output signal is a sinusoidal with changeable frequency. I need to read the output signal by oscilloscope. I should put a DAC at the output since the output of FPGA is parallel and digital. I do not know how should I do this, since I am not familiar with DAC. My FPGA is Spartan3. Can I design the DAC by FPGA itself or it must be a physical circuit implemented by resistors, capacitors etc.? Can anyone show me a circuit or program for a DAC which is applicable for me?


texts:
I would like to measure muscle tension with a sensor. When I'm sleeping sometimes a shoulder muscle cramps and I would like to make something (for example with an Arduino board) to wake me up. The problem is to measure the muscle tension.

A EMG sensor uses three pads. The Myoware EMG board can be used for DIY projects. I have not tried it yet. I think it is not easy to attach it every evening and I don't known where to attach the three pads to select a specific shoulder muscle. But so far this is the only thing that comes close.
[ADDED] I wonder what happens if I attach the pads to a muscle that has already a high tension. Would the EMG be able to measure the absolute tension ?

A ultrasonic liquid density sensor is big, they can not stay attached while sleeping. It could also be a safety risk. Perhaps the ultrasonic could harm tissue and blood cells.

The best way to measure muscle tension is to pinch or press it. Perhaps something small that mechanically pushes into the muscle and measures the strength could work. I have no idea how to make this.

With dry needling, a relaxed muscle does not react, but with a muscle that cramps or has a high tension, then the muscle reacts a lot. However, I can't push needles into my body while sleeping, that would be silly.

If you know a way to measure muscle tension in a practical way, please let me know.
A similar question was asked in the Health section as well: How can I quantify muscle tightness?

[Update] First tests with a EMG sensor.
I have been testing a EMG sensor. The Myoware 4th generation EMG sensor is easy to use for DIY project. To prevent grounding or noise, I used a battery and it is not connected to the computer.
Sadly, it is not near to what I want.
With my fingers I can feel how much tension a (shoulder)muscle has, when I move my back/head/shoulder a little I can feel what is going on. The EMG sensor is more like a lie detector. It detects the tension of a muscle, but that is mostly relative tension and it depends a lot on where the pads are located an how well they are attached. When I use it the next day, I want the same tension to result into the same numbers. That is not possible.


texts: How to find the current's phase given the period?

texts:
I asked a question earlier, and it only made me have more questions. I'll just show you a real example and maybe someone can help me with a quick answer.

I need to write the sinusoidal expression of the current if I = 2 [A], and f = 100 [Hz]. The initial phase of the current should be 1/4*T.

I know that:

T = 1/4 = 1/100

γ = 1/4 * T = 0.25 / 100

i(t) = √2I* sin(ωt+γ).

My question is the following: Is this how you find the period's value?

T ..... 2pi

γ ......xpi , resulting γ = 0.5 pi


texts: Why are length-prefixed fields considered hardware unfriendly?

texts:
One criticism of GENEVE (a network encapsulation protocol) is that it uses tag-length-value fields, and these are hard to process in hardware.

Why is this considered hardware-unfriendly?  What approaches would be more friendly to high speed hardware implementation, and why?


texts: Is anyone aware of a LIDAR solution including a horizontal angular sweep of >10 degrees and up to 10-20 meters of range?  I've looked but can't seem to find the just right solution.  Anyone who has made a comprehensive tabulated list of current LIDAR offerings out there?


texts: Why does an increase in capacitor ESR make the capacitor hotter?

texts:
According to what I have read online, if a capacitor's ESR increases, the capacitor temperature will also increase and this has me left a little confused.

Consider the simple single resistor circuit below:

If my resistor value was 100 ohms, I would be dissipating 0.25 watts of energy. If I was to replace the 100 ohms resistor with a 200 ohms resistor I would be dissipation 0.125 watts of energy. We can clearly see here that a higher resistance value produces fewer watts and fewer watts equals less heat.

So the question is why is the same principle not occurring in a capacitor when the ESR of the capacitor increases? I would think that more ESR means more resistance, more resistance equals less current, less current equals fewer watts and fewer watts equal less heat. So more capacitor ESR equals a cooler capacitor.


texts: The PIC model I have is PIC24FJ128GA010. My question how many clock cycles does the RETURN instruction consume?  The datasheet says 3(2), what does that mean?


texts:
Can I "break" an always blocks in Verilog? I would like to rewrite

  always @(posedge clk_i or posedge rst_i) begin
    if(rst_i) begin
      // Do stuff
    end else begin
      // Do stuff
    end
  end

as follows (which I find cleaner):

  always @(posedge clk_i or posedge rst_i) begin
    if(rst_i) begin
      // Do stuff
      break;
    end

    // Do stuff
  end


texts: Why use an input resistor in this current sense circuit?

texts:
In the Linear Technology AN 105 on current sensing one can find the following circuit.

I am wondering what the purpose of the 200 ohm resistor on the inverting input is. It appears to have no effect.

Note that in the following paragraph a virtually identical circuit is presented that is lacking said resistor:

As a side issue: is there any downside to sizing the 200 ohm input impedance resistors significantly larger, e.g. 10k? (Keeping gain constant.) The aim would be to reduce the current the opamp draws from its supply to drive the BJT.

Edit 1: Need for Q1

In the comments it was questioned whether the output transistor Q1 was needed. See my comment below on my interpretation.

Edit 2: Johnson noise

The Photon's back of the envelope calculation suggests that the input resistor's Johnson noise is not likely to be an issue even for large values if 0.1% (of output range) noise on the output is acceptable: $$ Vrms = 10\times \sqrt{R}\sqrt{\Delta f} \times 10^{-9}\text{in Volt}$$

For Vrms = 0.005V and 70kHz: $$ R = (\frac{Vrms}{1.3\times\sqrt{\Delta f}}\times 10^9 )^2 = 211 G\Omega $$


texts: Motor Discharges Boost Converter Too Quickly

texts:
I am trying to step 3V up to 9V via a boost converter, the idea being I have the current but not the voltage to drive a DC motor. I used this this website to calculate the parts values I would need, and assembled the boost converter on my breadboard. I noticed two things:

Increasing the duty cycle with which I was PWMing the transistor barely increased the voltage. I was led to believe it would do so more greatly.
The capacitor would charge until I provided a load across it, at which point it would reach an equilibrium. This makes sense to me (the capacitor charges when the switch/transistor is off, and discharges if there is a load when the switch is on), but placing the H-Bridge that drives my motor in parallel with the load resistor results in an immediate discharge of the capacitor and the voltage drops from 9V to 4.5V, not enough to power the motor. Placing the H-Bridge in series with the load resistor does not result in it being powered but as if the load was disconnected.

I unfortunately do not remember the model number of the diode off the top of my head and won't be able to get to the lab to check it until later in the day. It is some type of fast switching Schottky diode.

simulate this circuit – Schematic created using CircuitLab

Am I doing something wrong in particular, or is this just something a boost converter cannot do? Should I be using a different circuit of some type?


texts: What software makes magnetic circuit diagrams such as the one pictured?


texts:
I have made an IR proximity sensor which works fine when an LED is connected.

Figure 1: This is the IR receiver and emitter part of the circuit. The white LED is connected to ground via a 270 ohm resistor and is connected to pin 1 (the output) of the LM358
I want to connect the output from pin 1 of the LM358 to an NE555 timer which is in astable mode (with a potentiometer) so the LED blinks whenever any object is near the IR sensor.
Could anyone please help me with setting up the NE555 timer in astable mode with a potentiometer?

Figure 2: Here the LED lights up when the pencil is sensed by the IR proximity sensor

Figure 3: IR sensor schematic, to connect to the NE555
I have a 20 k potentiometer, please tell me how and what I need to connect to get a 1s or shorter time period for the blinking, whenever the IR sensor detects the proximity of an object.


texts:
I have lame question. How does digital pullups work? I'm asking because I don't understand DHT11 driver code.
Sample code:

bcm2835_gpio_write(pin, HIGH);
  usleep(500000);  // 500 ms
  bcm2835_gpio_write(pin, LOW);
  usleep(20000);

It will send start signal to DHT11, but it needs to be LOW for 500ms and then HIGH for 20us, but here signals are inverted. So, why how pullups works?
Schematic:


texts: What is the difference between testing and verification?

texts:
Every textbook I've seen makes a big deal of the fact that testing and verification are two different concepts. Yet none of them provides a clear (or clear enough to me, at last) distinction.

To provide some context, I'm interested in the verification of digital hardware designs using hardware design languages (HDLs).

I've seen some explanations that resort to a "physical" or "tangible" difference: if it is about a manufactured device, then it's testing. Is this the whole story? If so, why does the word "test" come up so often in verification (especially in functional verification, we talk about testcases, testbenches, DUT (device under test), directed tests, random tests, etc...)


texts: Power BJT Transistor in motor driver keeps burning

texts:
The power transistor 2N3055 keep getting damaged after connected for a couple seconds to this circuit. I would like to know what could be the cause.

I soldered this circuit for a 6-wire stepper motor (every coil has measured 2ohm resistance) in a perfboard. So the full system is basically this one replicated 4 times (since two wires are driven to +12V, the coils are intented to be connected to GND by the opposite end, and this connection to GND is performed by my circuit. Before making the circuit, I manually tested the motor with a 12V, 5A DC supply and its working fine.

The circuit was working fine with 4 little power transistors TIP31, which are rated for a current of 3A, but they were heating too much and also the datasheet shows they can drive an IC of 5A pulse current which is less than the 6A that this motor is needs (since the voltaje is 12V, and the coil resistance is 2ohm). So I replaced the TIP31 with big 2N3055s, but those keep getting damaged as soon as I connect the digital outputs of the Arduino (which also got damaged). The motor stops spinning without completing a single rotation and when I measure them with the diode function of the multmeter, the emitter seems to be damaged. I can see 0.6V between Base and Colector but 0V for Base-Emitter. So they are definetively out of operation a few seconds after circuit is energized. I am using pulses of 100ms width from the digital outputs for every coil, following the sequence I already manually tested .

The 2N3055 are attached to heatsinks I got from computer, and I am pretty sure is not because of overheating, because I used good thermal paste and also I am sure they are not shortcircuiting thru the heatsink, which is cool all the sime since I am paranoid and keep my hand close to them to check.

The circuit works good with a small 5V motor from toy car, but cannot work with powerful motor and I dont know why. These are my theories:

a. Overheating => but the heatsink is cool, I dont feel in my nose the odor of heating - also it takes a while to burn down a transistor.

b. Freewheeling diode not working => but I measure the anode-catode voltaje with diode tester of multmeter and it indicates 0.7V. I havent changed the diodes since I made the board first time.

c. The 2N2222 => but they seem to be ok too. I havent replaced them from the first time I soldered them.

d. A special thing that I havent taken into account.

I wonder why do they get roasted while the tiny TIP31 worked well. I also wonder why did digital outputs of arduino died, if they are driving the 2N2222 so no direct connection to power transistor.

Adding new info

Current gain is 20-50 for TIP31 and 20-70 for 2n3055, thats the reason cause I need the 2n2222 as predriver.

About supply bulk capacitance, I dont know how to measure it. Im using one of those universal laptop charger that have a voltaje selector. I guess its switching type. The bulk capacitor must be laaarge, since the power led stays on for almost a minute after I unplug it.

Edit #2: adding pictures of the circuit


texts: Things to consider before baking components

texts:
I will be using my own baking oven for components/ICs. What I only know is the baking conditions of MSL devices as per Jedec or as per required baking conditions as per MSL label of the part.

For example, MSL 3 devices needs to bake for 24 hours @ 125 deg C.

Do i need to heat my oven first until it reached 125 deg C and put my parts and count for 24 hours or I can put the parts straight away and wait for 24 hrs to complete the baking?


texts:
I found USB Flash drives on aliexpress.com up to 2 TB. So much people bought them, and I'm reading feedbacks and 90% says: "It works perfectly, thanks", just a few customers have left a negative feedbacks. Is it possible that flash drive with 2 TB of memory space exists nowadays? Why not, and whats the maximum flash drive storage capacity? Which type of formatting do they use, FAT32, NTFS? What is this all about?

Here is the link


texts: Help to translate jitter design constraint in a frequency synthesizer design with 4046 and 4017 ICs

texts:
I'm trying to design a frequency synthesizer with the old-school 4046 and 4017 ICs, with a scaling factor N = 1,5,7,10.

The input signal is a square wave with adjustable frequency from 1 kHz to 10 kHz.

I want to get a time jitter < 1% of the period.

I'm a newbie in PLL design, so I've done the only possible thing: study. I already knew control theory, filters, loop gain, stability and so on but I still can't understand where to start in the design to achieve the desired performance. Many books state that the design should start from the closed-loop bandwidth, but how do I relate this to jitter? I've read about calculating RMS time jitter from phase noise, but the datasheet of the 4046 has no data about VCO phase noise (for example) and I have zero info about the source phase noise (the project is for college and the professor didn't give me any other information).

Please if you could help me, I literally have zero ideas on how to go on.


texts:
I would like to make a threshold-temperature on-off switch (a.k.a. a thermostat). Short of buying a commercial sensor like an LM335Z (I know that it's super cheap) and figuring out how to use the output, I thought that it could be a fairly simple task to design something that would turn on an electrical device below a certain temperature.

Imagine a two-layer long narrow "wafer" made of two materials with dissimilar thermal expansion coefficients, perhaps rubber and very thin steel. This would be a physical action arm that engages and disengages a switch by its position. I would calibrate the switch to turn on at the right temperature with a separate temperature gauge, and have a working thermostat.

My current plan is to make a device that will help maintain an environment suitable for bread to rise (anywhere from 85 to 105 F). It could also be used to make yogurt. Or keep a lizard cage at the right temperature. The possibilities are many.

As a bonus, I'd like to teach my son some science and handicraft, so this has additional purpose beyond the practical.

It's just a vague idea at the moment, so I wonder if others with more experience in DIY projects of this type could offer advice. I have some wiring experience and am willing to purchase parts if needed (even if that raises the total price beyond what I could simply buy). I also have a fairly large store of random electronics parts and pieces that I may be able to use.


texts: PCB layout for shunting RF common-mode current to chassis

texts:
I am laying out a pcb with a number of external connectors that will have RF common-mode filters at each connector, shunting any common-mode signals to the chassis. However, I'm not sure what is the best way to connect the filters to the chassis to minimize radiated noise within the enclosure.

There are a number of standoffs that could be used for this, but should all of the CM currents from each filter be run through traces and to a single chassis connection? Or should I use small isolated ground islands and connect them to separate, local standoffs that way?
If I should use a trace to a single point, should it be routed in a particular way (I was thinking along the edge of the board)? Any tips on how to do this?


texts:
I'm trying to figure out how to determine what frequency an electrodeless conductivity sensor needs for accurate measurement.

An inductive sensor consists of two wire-wound metal toroids encased in a
corrosion-resistant plastic body. One toroid is the drive coil, the other is the receive coil. The sensor is immersed in the conductive liquid. The analyzer
applies an alternating voltage to the drive coil, which induces a voltage in the liquid surrounding the coil.

The voltage causes an ionic current to flow proportional to the conductance of the liquid. The ionic current induces an electronic current in the receive coil, which the analyzer measures. The induced current is directly proportional to the conductance of the solution.

EDIT: Added picture to question. Picture taken from: http://www2.emersonprocess.com/siteadmincenter/PM%20Rosemount%20Analytical%20Documents/Liq_ADS_43-018.pdf

However, how do i calculate the frequency of the AC signal?

Regards


texts:
I have a very simple circuit as follows

simulate this circuit – Schematic created using CircuitLab

when the motor is connected in this fashion, the netduino activates the transistor, but nothing happens. If i swap the motor with an LED, the LED does light up, so that incidates that the motor isnt getting enough power...

So i connect the motor direct to power and gnd, and it spins. Does this mean that the transistor is drawing so much current that it is stopping the motor working?


texts:
In all designs that I could find they used two LM317, one for CC and another for CV. Is there a reason why no one used a circuit like this with only one LM317?

simulate this circuit – Schematic created using CircuitLab

it's based on dave jones design, he used an LT3080.

Assuming we have a negative voltage for adjust pin and output voltage actually goes to 0V.


texts: How is using a transformer for isolation safer than directly connecting to the power grid?

texts: How is using a 1:1 transformer safer than using the mains straight off? Is it because you can limit the current coming from the transformer whereas straight from the mains its not current limited? I fail to see how its "safer" when playing with electricity is dangerous. Could someone please explain why it is considered safer to be isolated by a transformer.


texts: Which material enclosure to avoid impeding signal of Bluetooth and wifi?

texts:
I’m making an enclosure for:

https://www.digikey.in/product-detail/en/ESP32-PICO-KIT/1904-1030-ND

I read that Bluetooth signal can be impeded by 37% by a plastic case. If that is so, then how does one design a case to protect the esp32 from dust , water , etc, without impeding the signal?


texts: Sane default for Altium pastemask expansion?

texts:
I am rather new to layout work. I am asking this question to sanity check that:

The pastemask expansion is supposed to be negative (paste area smaller than the pad), right?
My vendor said to use "0.1mm expansion" (I assume that means -0.1mm), but for minimum-size 0402 pads (0.6mm x 0.58mm), this causes the paste area to be only 44% of the copper area! Whereas people online say that the paste area should be 80% of the copper area. What's a better strategy -- a fixed -0.1mm expansion regardless of pad size, or doing it by area and manually setting it up a different expansion for different pad sizes?
Is it a better idea to specify pastemask gerbers myself (and risk specifying the wrong amount of solderpaste), or leave it up to the assembly house (and risk them messing up special features like golden fingers)?

Thanks!


texts: STM32F405 Internal vs External Oscillator

texts: If the frequency stability over a temperature range is not a concern in a project instead it's reliability in continuous long time operation is a more important factor then which of the two oscillators would be preferable, internal RC (16 MHz) or general purpose external crystal oscillator (8 MHz) to get a SysClk of 160 MHz using the internal PLL?


texts: Is there a component with a simple 2-digit number on it (00...99) that can be mounted during standard board assembly process (i.e. pick-and-place machine and reflow)? Something like Molex track-it Traceability Pad but just with a very short human-readable number.


texts: Should I multiply by time to determine Watt-hours?

texts: I have done an experiment with solar panels over the course of the day to determine the total power output in Wh. I measured voltage and current through my solar panel circuit using a multimeter every half an hour. I multiplied these together to find the power being generated each half hour of the day. Assuming the power rises and falls linearly between each measurement, I determined the energy for each half hour is equal to 30 times the power at the mid-mark (either 15 or 45 minutes into the hour). Now, to determine the total energy in Wh the panel produced during the day, do I multiply the result of the previous operation by 0.5 hrs and then add all the interval's power together or can I just add them all together without multiplying by 0.5 hrs?


texts: Is this TL072 stereo opamp circuit functional? Can it be used for LM833 too?

texts:
I modified opamp circuit a little bit and I hope it will work. I am not EE, so any advice is welcome. Can this schematic be used with LM833? And if i could, do I need to change values of some components?

I found advice on some other thread that says: There is one issue with this topology. Frequency-wise, C1 is acting with R1, but the DC level that C1 will eventually stabilize at is filtered by R1+R2 and C1. That is a filter at 1.6 Hz, which means this circuit will take a few seconds to stabilize after power is applied.
 Not sure if this means C1 and C2 should be replace with 1uF.


texts: ST L4 series datasheet specifications and 1 wire

texts: When you open STM32L476 specification on the The DFSDM peripheral supports (42/232) it says that "Manchester coded 1 wire interface support". Does this means it supports 1-Wire bus like for DS18S20 or it can support some sort of communication on 1 wire?


texts: Solar panel system with as minimal reliance on the grid

texts:
I am not sure if this is the best place to ask, but I am trying to make a solar panel system which will charge batteries with excess energy and will be connected to the mains (i am going to try the lights circuit initially).

I also want a backup from the grid if the batteries run out and I am not producing electricity (like at night).

I am starting with a 300W panel http://www.naturalsparx.co.uk/product/2500638030/LG-Mono-X-Neon-G3-300W-Mono-PV-Module-Black.

I would need to connect this panel to a 3 phase MPPT charge controller, then batteries, then a True Sine Wave inverter to 230V mains to the circuit breaker.

Is there an inverter that will allow me to charge batteries when needed and power the mains when needed and take power from the grid when needed?

Is this a solar hybrid inverter?


texts:
I'm following the wiring diagram for a digitech fs3x guitar pedal footswitch.

For the third SPST switch, it's wired from the other two switches connected by 2 diodes, both in the same direction. Can anyone explain why a single diode wouldn't work here (with both wires connected to it)


texts: 8085; why we can't reduce number of T-states in opcode fetch machine cycle

texts:
In the above timing diagram for opcode fetch machine cycle , can we not do the entire operation in just 2 T states like this :
In T1 state we first latch the lower order address by making ALE high for some time .Then we make READ signal low in the same clock period .Data is available on lower order multiplexed address/data bus .At this point we make enable input of instruction register(IR) active so that at the end of first clock cycle the data will be loaded into the IR.Then the process of decoding can be done in T2 state i-e., Second clock cycle .
Doing the fetch part in 3 clock cycles seems unnecessary to me and a waste of time .


texts: Micro rectangular heating element for thin layer heating

texts:
The purpose

The main goal is creating a little hand-held device that would heat a thin film (locally) to \$50-70°C\$ by sliding over it. The film area is \$<150cm^2\$.
A secondary goal would be to create a device with the same parameters that would cool the film down (locally) to \$<-28°C\$ to reverse the process.

Problem domain

The problem that I need help with

Reasonably sized case within the range of units of centimetres.
\$1mm \times 20mm\$ heating element (1mm or less if possible to increase efficiency)
A circuit serving the heating element
Battery

I don't want to heat the material itself (or I do, but very superficially, maybe 0.001mm in depth). This device has to be powered with a low capacity battery (e.g. 1700mAh, 1.5V) for as long as possible.

I came up with a couple of ideas, but I can't figure out the specific parameters and components to use.

1. Termistor

As a self-regulating heating element, thermistor seems to be just perfect for this purpose. But what exact parameters should it have? Will it be effective enough? And where can I buy a thermistor with those specific parameters?

2. Peltier Module

Another solution that comes to my mind is using a Peltier Module. It uses a lot of power, but maybe if I make it small enough (by splitting a ready-made Peltier Module into separate rows?), maybe the input power wouldn't be so high. The questions about the thermistor apply here as well.


texts:
I hope someone here can help me understand a dilemma that I'm facing.  I have a design that incorporates two limit switches to limit the ends of travel of a slider plate.  My circuit uses the switches in series, either of which will break a conductivity path, such that the path 'defaults' to a resistor pulling the path to ground if either limit is reached.  So, I'm looking for an angled 'detector' (see attached) switch that is NC when not actuated and NO when actuated.  However, among the HUNDREDS of NO 'detector' switches at Digi-Key for example (many of which are available singly) when not actuated, not a single ONE can be found with a NC circuit in less quantity than several hundred.  Can anyone help me understand why the world of electronics manufacturing/distributing has arranged itself into that triple witching?

Does it just make more sense to pass a signal/voltage when activated rather than break a circuit when activated for implementing a 'detector' function?  Safety or reliability issues?  My design seems efficient and does the job with the fewest possible parts and potentially the least cost.  Why does the switch manufacturing/distribution world seem so insane?


texts: Can I detect 0.8 volt with a relay or something?

texts:
I have this currently
It's the ISD1820 voice recorder and it's working as expected, kind of.

I have connected as in the schematic above but I want to turn on a LED when the recorder palays the message.
The obvious would be to connect to the 12 v reed switch, but something is very odd with the play-pin.
A dead wire makes the message play. I mean a wire not connected anywhere just touches the pin, and it plays.
The way it's currently working is when the state of the reed switch (and relay) changes the message plays meaning I can't detect it on the relay (or can I?).
Meaning it plays the message no matter if the relay is open or closed. It's the change that makes it play.

I found out that R4 on the top right of the board has 0 v when nothing is playing, but as the message is played it has 0.8 v.
Is that something I can detect? I don't know of any relay that can get triggered on such low voltage.

Sorry for the tag, I'm still new here and don't yet know what tags to use.

EDIT: Dorian has pointed out that it's not appropriate to simply connect something to the pin.
With that said, let's say add a timer relay that I set the time perfectly on to match the message lenght/time, how can I make it get triggered on the state change of the Reed switch or relay.


texts: AUX input outputting +4v Causing reset of connected smartphone

texts:
I've added an AUX input to my Mercedes Audio 10 casette radio using an online tutorial. Essentially hooking up a 3.5mm jack direct to the output of the audio processor.

I'm familar with this procedure having done it with some USB-only Harmon Kardon soundsticks and other devices.

It works well with my ipod, music plays in the car at the correct volume with no ground buzz or artefacts I can hear.

When I attach my phone however, the phone immediately hard-resets.

I've poked around with a DMM and there seems to be about +4v DC between each signal wire and ground.

As a comparison the AUX-input wire I soldered onto the Soundsticks puts out about 2.2v DC between each signal wire and ground. The phone works fine with the Soundsticks.

Could it be that the phone doesn't like this extra voltage and is resetting to protect itself?

How should I go about lowering this voltage? Pulldown resistor to GND? perhaps a shunt?


texts: In a 240 V "2-phase" wiring, how does current/amps get distributed?

texts:
It is my understanding that if I need to draw, for instance, 30 Amps from a 240 V circuit (Live-Live) then there will be 30 Amps running from both wires, not half and half. So, the AWG sizes for the wires should be something accord to that.

The question arose from the installation manual of an electrical oven I am buying for a my home. It is a 240 V oven, with 4 wires (L, L, N and ground), and it says it needs a 40 Amp breaker. The specs says it draws at most ~31 Amps. So far so good. But then we get to the wiring size recommended and it says "12 AWG". I would expect at least 8 AWG for that load. But as I'm not quite sure if my understanding of currents/loads in a L-L circuit are correct, I rather ask.

In any case, I'm going to use 8 AWG wire, but this got me curious about this subject.

The manual with the recommendations is this, the oven model is WOS92EC0AS.
https://www.whirlpool.mx/content/dam/global/documents/201506/installation-instructions-W10351242-RevC.pdf


texts: Linux PCB with support for GPU accelerated X Windows

texts:
I'm looking for a Linux PCB (ARM or Intel)
with a GPU that can run debian linux and use the GPU in X Windows.
Preferably with an HDMI output or at least a DVI output.

Something that is available on the market today.
I'm located in China, so I should be able to find just about anything,
but I have no idea what to look for.

Any suggestions?


texts:
I am trying to get an infared signal being sent from an emitter (think along the lines of a remote control). I know I can use a fotoransistor on a breadboard to capture/detect the signal, but I have no idea how to get the code being sent out of it. I need the hex so i can re broadca st it. How can I get this info?

There are websites that have IR codes like the one I'm looking for but they don't have particular for this device


texts: Audio amplifier power supply transformer problem

texts:
I have been using this old audio amplifier for some time now and recently it stopped working - music was playing and it suddenly went out, you could only hear the 50 Hz buzz, magic smoke coming out and the thing was warm.

After changing a bad fuse and powering it up, I found out that the transformer was heating up so much its wax insulation melted. I tested the output with a multimeter and it roughly checked out, but when I disconnected all secondary wingdings and powered it back up it still got hot, so I figured that it was faulty.

Since it was pretty specific (2x20V with center tap plus 16V) there were no replacements available online, so I decided to replace its wingdings manually. I measured the primary winding to be 70Ω, 0.2mm copper wire and calculated that it has to be roughly 130m long. After taking the core and old coils apart, I winded 960 turns of the same wire type onto it, then 10 turns secondary so I could measure its voltage per turn, and carefully powered it up with a fire extinguisher nearby. It didn't trip any fuses, but it buzzed pretty loudly and heated up to 80 degrees Celsius before I disconnected it.

My question is: what did I do wrong? Although I never built a transformer, I have been playing with electronics for over a decade now, so I thought I could handle this.

For reference, the sockets here are 230V 50Hz.


texts:
I am mostly doing development on devices that have ported Linux so the standard C library provides lots of it's functionality through implementing system calls which have a standardised behaviour.

However for bare metal, there is no underlying OS. Is there a standard related to how a c library should be implemented or do you have to relearn peculiarity of a library implementations when you switch to new board which provides a different BSP?


texts: optimal resistor for TP4056 with AMS1117 input

texts:
Finally finished this board for my 12v led strip light power backup. It works like this: When 12v main power is on, it will charge a 3.7v lithium battery using the TP4056 ic, and when power is out, a relay will turn on to power a dc-dc step up circuit to power the 12 led strip. Everything works fine, except that when testing the power input with 18V, the AMS1117 is overheating and hot to touch (and yes, I use my finger as a testing instrument.). TP4056 can output 1A-130mA, and I am setting it to 580ma using a 2k resistor. according the datasheet of AMS1117, it can output 800ma, so here are my questions regarding this circuit.

1, why it's over-heating? is it because of higher voltage drop?

2, what should be the optimal resistor value (or current) for the tp4056 so that the AMS1117  won't over-heat when powered with 7-15v? (I think max input for AMS1117 is 19v, but I can't find it anywhere in the datasheet I got. It only states input as 15v.)

3, How many watts will be wasted in this AMS1117 if my input is 12v and I am charging a 4000mah 3.7v battery?


texts: ESP8266 detect LED flash with photoresistor Schmitt trigger?

texts:
I made some experiments with ESP8266 to detect when an external LED is on or off (I need to log this activity).
This is the test-circuit I used till now:

simulate this circuit – Schematic created using CircuitLab

I have a lot of programming experience, but every time I need to deal with the electronics circuits I have some difficulties, so the above schematic may be wrong.
All resistor values are empirically calculated. I used a wave generator (5Hz) to simulate LED flashes, and on the oscilloscope I get:

LED on: ~3.22V on (-) OAMP pin
LED off: ~1V on (-) OAMP pin
On (+) OAMP pin I set ~2V

Now I would ask:

How can I improve this schematic?
How to reduce power consumption?
Does exist a better OAMP (instead of LM358) specifically designed for low power circuits?

Here there're some glabal tech spec:

VDD: 3.3V
Max led frequency: 2Hz
low power consumption
I need to measure the time interval between two pulses to detect system (which LED belongs to) state. For example: 1sec between two pulses mean state A, 0.2sec between two pulses mean state B, etc..

NOTE: in the final circuit I cannot interfere with LED and its circuit, I can only watch its light.


texts:
Today I have started to encounter strange problems with SWD debugging.

The debug only works if I keep my finger on the SWD pins. To be more interesting I have the same problem with the boards I was working in the past without any problems. All Vdd and Vss are connected correctly - checked many times.

I am trying to sort this problem for two days and have run out of the fresh ideas what actually can cause this problem.

Any help appreciated.


texts:
I've implemented a division algorithm on an FPGA using the long division algorithm. My implementation does not use pipelining, but works iteratively and requires very few logic elements since the algorithm mainly consists of a single subtraction and some shift registers.

For a signed version of the component I just use the absolute values of the inputs and negate the result as required. This works as expected, but negating two's complement numbers does require adding '1' after inverting all bits, which results in 3 full adders in the design. This results in roughly twice as many logic elements for a signed divider compared to an unsigned one.

Is there a way to adjust the long division algorithm, so it directly works with negative numbers? I've already figured out that I can include the '+1' for the denominator during the main subtraction by using a borrow bit. I haven't found out how to handle the numerator or how to directly produce a result with the correct sign.


texts: How to attach a wire to something small and conductive (< 5 mm connection area)

texts:
I have two problems where I have a small area to make a connection on a material that is unsolderable.

The first material that I need to solder on is annodized aluminum, on a 5mm x 3mm x 2 mm rectangular prism. Yes, you can solder on annodized aluminum, but it is not ideal. It seems like the connections break very easily, at least using standard solder and soldering irons.

The second material that I need to solder on is conductive plastic. Conductive plastic cannot be soldered on. Again, I have about 5 mm of space to work with.

I have tried wire glue, but, if I decide to get my product manufactured in China, will they want to use wire glue to attach to my product? Is this the best option? It seems very unprofessional, and a lot could go wrong (connections breaking, glue not being stirred enough prior to application, conductivity drying out over time (i.e. after a test procedure)).

What I would really like is something small, and clamping, almost like 5 mm aligator clips. Or, even a small, solderable paper clip.

What weapon am I missing in my arsenal?


texts: What causes these different behaviors in my amplifier?

texts:
I fabbed the gerbers of the eval board for the SKY67153-396LF and used the component values in the datasheet for the 2300 to 2700 MHz band. I tested it yesterday and got some interesting results. There are several different regions of behavior that it has, most of which seem wrong. Here's a video of me sweeping the input power and you can see what's happening: https://www.youtube.com/watch?v=IT8x9wOr9ag Here's a version where you can see the current being used by the amp: https://www.youtube.com/watch?v=eZGxI3nrgM8

It's kind of hard to see the spectrum analyzer, but the marker is at 2.52 GHz, the same as the input freq. The span is from 0 to 6.5 GHz. The amp has very little gain until the input power gets up to a few dBm, and doesn't get close to the correct gain spec until 7 dBm. That's also when all the mixing products (or whatever those spurs are) go away.

Can someone help me understand what's going on in these different regions? What causes those mixing products? Why doesn't amplification begin until a particular input power level?


texts: Using the PORTB interrupt on change feature with XC8

texts:
I'm making a program to learn to use portB interrupts on the PIC18F2520.

I made a program, but it's not working correctly. The program is all time lighting and turning off the led, and the led's state should be changed only with a change in some portB pin (I'm using a button).

I show you my code:

#include <xc.h>

#define _XTAL_FREQ 4000000
#define LED_OUTPUT LATC3

unsigned char config1;
unsigned int timer_value;
unsigned int tpr;
int counter=0;

void main(void) {

TRISCbits.RC3 = 0;

   ADCON1 |= 0b1111;

   EnablePullups();

   INTCONbits.RBIE = 1;
   //RCONbits.IPEN = 0;
   //INTCONbits.PEIE = 1; // Enable Perpherial Interrupt

   INTCONbits.GIE = 1; // Enable Global Interrupt

   INTCON2bits.INTEDG0 = 1;
   //INTCON2bits.NOT_RBPU = 0;
   //TMR1 = 0;
   while(1)
   {
       __delay_ms(100);

   }
}

void interrupt isr(void) {

// Was it the port B interrupt on change?
if (INTCONbits.RBIF) {
    // Dummy read of the port, as per datasheet

    // Use XOR to toggle the pin, saving a variable
    LED_OUTPUT ^= 1;

    // Reset the interrupt flag
    INTCONbits.RBIF = 0;

            if (PORTB) {
        asm("nop");
    }
     __delay_ms(100);
}

}

Here I show you my schematic in Proteus!.

The button is attached to pin RB0. Let's see if we can find the mistakes together.

Greetings!


texts:
I am making my own little power-failure warning system. So when the power goes off a LED and buzzer goes on.

Right now it looks like this:
http://imgur.com/a/oc8vy (Sorry for not making it the right way)

But... The coil is not moving. It's in "off" mode the whole time. And that is kinda strange.

So when I was searching for the error I connected the coil to a 9V battery (even if it's a 5v relay). Then the coil was suddenly moving. So I changed the voltage on the adapter to 9v. But still no reaction.

And YES the current is going trough, because I placed a LED after to see if there was current at all. And it was.

So what could be the problem?

Best regards
fiskarn

And well again I connected a LED to the relay-circuit and it was lit. So there's current. Also measured the voltage to 4.9 wich would be enough? But as I said I even tried with 9V and 12V.

Also tried on 3 different relays with the same results.


texts: How to detect pulse duration with CMOS circuit

texts:
I have created a circuit where I want to detect a pulse width, but unfortunately I can't get what I want. I think my circuit is totally wrong. I am looking online to find a solution, but the closest solution which I found was the Duty Cycle Adjusting Circuit for Clock Signals, which is not what I need.
I need a circuit that will output a voltage proportional to the pulse width of the input voltage.
I want to get this output.

But all I get is triangle wave generator.
So I have changed the circuit a little bit and I have got a result closer to the desired output. With the proposed solutions is a little bit hard to understand what I should do to achieve my desired output.

Here is the output that I get:

I want v(net2) to start from 0 and be more linear after the pulse. I have also designed another circuit but there I get something completely wrong.
Here is alternative circuit:

And the output of this circuit is:

Which is not even closer to the first solution.
Help me to achieve the desired solution given in the first picture.


texts:
I am trying to generate a square wave on 50% Duty Cycle using my PIC18F2550. The signal is to be outputted through a loudspeaker. The frequency does not really matter, as long as it is in the hearing range (a few Khz should do).

This is my rather simplistic code;

#include "xc.h"

void PWM_init(void);
void Chip_init(void);

void main(void){

Chip_init();
PWM_init();
while(1);
}
void PWM_init(void) {

/****Set All PWM Registers*****/
PR2 = 0b11111111;
T2CON = 0b00000111;
CCPR2L = 0b01111111;
CCP2CON = 0b00111100;
}

void Chip_init(void){

/** Initialize all outputs ****/
LATCbits.LATC1 = 0;
TRISCbits.TRISC1 = 0;
LATBbits.LATB3 = 0;
TRISBbits.TRISB3 = 0;
}

This should give me a PWM signal of about 3Khz on either C1 or B3, atleast to my understanding. But i am getting nothing, unfortunately. Can anyone tell me where I went wrong?


texts:
Figure 1 and 2 shows a rising-edge triggered JK flip-flop (JK-FF). When CLR = 0, the value of Q after rise is determined by the values of J, K and Q at the rise of the clock pulse CK . However, when CLR = 1, immediately without regard to J, K, CK values Q = 0 and Q - 1. Connect this JK-FF as shown in Fig. 3, and show the outputs Q1 and Q2 when giving each signal as shown in Fig. 4
i really havent learn anything about counters, is this problem related to counter? or only flip flop, can someone give me hint what this problem related to?
thankyou so much!!!!!!!!!!
fig 1

fig 2

fig 3

fig 4

My attempt after someone gave me hint:

more precise

is this true? the question want me to draw the diagram(?) or find exact value of q1 and q2? thanks!!


texts:
I would like a way to limit the current of a circuit to exactly 100mA (+/- 2-5%).  This is on a relatively high voltage circuit (100V to ground), and the current is normally pulsed with pretty fast rise times (let's say 1-2 microseconds) using another circuit (low-side) as a switch and pulse shaper.  What I need is a way to limit the current in case the other circuit malfunctions (fails short-circuit, in the worst case).  I would like to limit it within also a few microseconds (ie: not more than a few microseconds of overcurrent).  I would like this part of the circuit to not use much power when it is not actively limiting the current.  In case of overcurrent, the current can either be clamped it at 100mA or possibly disconnected until things reset, but clamp would be ok.  What is the best type of circuit to use in this case?

(Background: this is on a very compact board, there are less a few tens of mm^2 to fit this in).

(The average power available is limited to less than 0.3W at the source, even in a short circuit, so power dissipation is not as big of an issue as it might seem; the source will drop pretty quick from 100V to around 3V if there is sustained 100mA, but that takes milliseconds not microseconds)


texts: Steering wheel controls with zener diode?

texts:
I am looking at my steering wheel schematics and trying to find what are these zener diode doing there?

I want to be sure there's no problem feeding 5V from an Arduino to check the ADC values without having 12V from the control backlights backfeeding into the resistor network.

I measured with a multimeter I could get any voltage at all which is good.


texts:
I want to use FSMC of STM32F429 to read external FIFO implemented in an FPGA MAX10. Since no mode of FSMC can fit the FIFO interface precisely, I try to use the modified synchronous multiplexed PSRAM mode.

My plan is like this

A[25:16]: Ignored, don't connect to FIFO;

NEx, NOE, NADV: Implement a simple logic in FPGA that when NEx is valid and the NADV is data valid, connect the inverted NOE to the RD port of FIFO;

NWE: ignored, only read operation is needed;

D[15:0]: Connect to the output data port of FIFO;

There may be also some logic in FPGA to adjust the timing between NOE and D[15:0], but that is not a big problem.

My questions are:

Is this plan feasible? Is there any problem with this plan?
How can I extend the reading burst as long as possible? Since there are 2048x16bit in one frame, ideally, I want to read them all in one burst if possible.

Updated:

I've implemented the design which read FPGA FIFO through the FSMC interface in sync PSRAM Non-multiplexed mode successfully. Currently, each burst can only transmit 2x16bit data but it's already fast enough for my project.


texts: How to charge a USB-C host with ACA alternative?

texts:
For old some micro usb devices, you can wire the ID pin so it is connected to the ground pin with a resistance of something like 36.5 kΩ. When the device is in host mode and connected to a device, this would allow the android host device to receive power from an external source when it was connected to the Vbus pin.

Basically, this allowed a device to be charged, while in host mode and still be in control of the peripheral device. I believe this kind of connection was known as accessory charging adaptors (ACA).

My question is, is there an alternative wiring to this for USB-C, can I buy some sort of adaptor, or even design some sort of board myself to go between a USB-C phone and a peripheral device?


texts: Are USB 2.0 hubs required to disable downstream VBUS when upstream VBUS is removed

texts:
I'm using a Microchip USB2517 7-port USB hub in a self-powered application, and I'm interested in the behaviour of the device if the upstream VBUS detect signal is removed.  I'd like to know if the downstream VBUS is disabled when upstream VBUS is removed.  The datasheet mentions that power to the differential pins must be removed when upstream VBUS is no longer detected.  The datasheet isn't clear about the port power signal, however.

My reading of the USB 2.0 standard gives me an answer that's open to interpretation.  From section 11.5, it's clear that the port enters the powered-off state when external power to the hub is removed.  11.5.1.2 says "If a hub was configured while the hub was self-powered, and then if external power is lost, the hub must place all ports in the Powered-off state."  Unfortunately, it's not clear whether "external power" refers to the upstream VBUS detect signal being de-asserted, or whether it refers to the IC's external power (Vcc).  Under the former interpretation, if there is no upstream devices the hub will not supply power to any downstream devices.  Under the latter, the device will still supply some power (also not clear.  One unit load?  The negotiated number of unit loads?  Without power on the differential pair, the device obviously can't request more than one unit load if plugged in after the fact.)

TL;DR: Is there any power available on the downstream ports of a self-powered hub if the upstream port isn't connected?

Related: Does USB Host always supply power on VBUS? (doesn't describe behaviour during powered-off state)


texts: EE-Student Electronics problem ( Diodes)

texts:
I'm studying, at the moment, at university, Electronics 1, and struggling to understand how to solve this circuit. I tried to solve it, and these are my results and thinking.
The forward voltage drop for the diodes is Vz = 0.65(V). D11 and D10 are the same.
I need to find the voltage across D10 and D11 and the current through them.
This is how I solved it.
The current is obtained from the formula I = (V1+V2)/R1 = 8.55(mA).
Because the D11 is inversed polarized is not conducting current, so it's 0.
The current through D10 is the same current through the circuit, 8.55(mA) and the voltage is 0.65(V)
I don't know how to find the voltage of D11.


texts:
simulate this circuit – Schematic created using CircuitLab

I would check that in the Wien bridge sinusoidal oscillator the gain A_V=1+(R5+R4)/R3) is actually A_V=3 as the Barkhausen stability criterion requires. So I build this circuit whit a potentiometer of 10k instead of R4 and I obtain that for R4=6.38K (so R3 becomes 13.7k) the oscillation starts.
 With this configuration the circuit should have a gain A_V=2.2  (with the formula mentioned before)but I observe a gain of 2.9-3. How can I consider the contribution of the diods to the gain formula?


texts: Integrating USB C Power Delivery into a PCB

texts: I am aware of USB C Power Delivery trigger boards that uses PD protocol to output the desired voltage from a PD source. But I was curious if it would be possible and feasible to design and integrate a USB C Power Delivery protocol into a PCB design. If I were to do it, how difficult would it be and what would I need to know? Thanks.


texts: Performing Mesh Analysis on h-parameter transistor models

texts:
So I'm fairly comfortable with Mesh and Nodal analysis with numerical values, but I am having problems solving this circuit involving an alternative h-parameter model of a transistor:

simulate this circuit – Schematic created using CircuitLab

First as a note, I could not incorporate subscripts in the editor. Everything including hi, hr, v2 etc is subscripted at the second digit.

The question is to find the voltage gain (v1/v2) and the resistance (Req =v1/i1)

So I have establashed two meshes I1 and I2. These meshes are in the clockwise direction of both loops:

I1

-V1 + hi(i1) + hr • v2 = 0

I2

(hf/ho)•i1 + (1/ho)i2 + v2 = 0

So I simply solve for V1 and V2 on each mesh and then get the answer

V1 = i1•hi + hr•v2

V2 = -(hf/ho)•i1 - (1/ho)i2

So V1/V2 would simply be

-(i1•hi + hr•v2)/((hf/ho)•i1 - (1/ho)i2)

This doesn't really help me on finding Req, and I think I need more simplification. Am I on the right track with this problem? What am I missing to solve this problem properly? Thanks


texts: Being able to toggle a 24V battery bank to 12V

texts: I was asked to make a 24V battery cart with eight 12V batteries to boost some of our equipment on site. No big deal. Now they want to be able to flip a switch and get 12 volts out of the cart without a DC to DC converter. I don't want to pull 12 volts from just one or two batteries. So I was wondering if anyone could tell me how to wire up these batteries so I can get 12 volts from all of them with a flip of a switch. They also want just one cable reel for both 24V and 12V.


texts:
I'm looking at wind turbine current - power trends, and there is a phenomenon I need help to explain!
The data I'm analysing is from a 3-phase generator. Below is a scatter plot of current (x axis) against power (y axis).

Can someone help explain or suggest reasons for the 'tail' at the bottom of the graph?
I don't understand how there can be significant current output, but no power.
Many thanks for any help!