texts: Is it possible to check an Ethernet twisted pair with a multimeter?

texts:
It would be useful to measure electrical parameters (such as I,U,R and perhaps L,C or other) at the end of the cable, when the other end is disconnected or connected, and analyze the physical layer of the Ethernet computer network. For example when you occur problems on a network adapter, packet losses, loops or get an electric shock when touch the metal parts of equipment.

Some clarifying questions:

Is it possible to do this using one or several multimeters?
If it's possible then what and where exactly measure (between the wires or pairs of the cable or relative to ground)?
Could this give some additional and more detailed diagnostic information about the cable or NIC?


texts: Low resistance digital potentiometer - alternatives?

texts:
I've done quite a bit of searching online and can't find a solution to this (probably trivial!) problem:
I am looking to replace a resistive fuel level sensor in a car, with a solution which can be controlled digitally. A digital potentiometer is the obvious solution for this, however it doesn't appear that any exist which match the specifications:
Resistance range is 6-120 ohms.
Current through the resistor during operation is up to 80mA.
The wiper resistance of most digital potentiometers is much higher than the 6 ohm minimum requirement. It seems that 80mA is also too much for most options. I have considered linking 4 or more digital potentiometers in parallel, but I'm sure there is a more elegant solution. I don't want to go down the "stepper motor and potentiometer" route unless I have to.
One thing I considered would be a resistor array, switched using transistors. These could be driven from a shift register, allowing suitable resolution without using too much IO on a microcontroller. After all, this is a fuel gauge, it only really needs 16 levels to be functional.
I imagine that having 7 transistors, each switching a resistor, with values of 1,2,4,8,16,32,64 ohms (or similar), it would be possible to create such a circuit. The issue is how these transistors will react when combinations of them are switched. I can't quite get my head around how to design such a circuit.
Does anyone here have experience with such a circuit? Is there a "cleaner" alternative?
Thanks for your time!
In the image below, L1 and L2 are the motor windings, R5 and R6 are fixed resistors, L7 is the potentiometer to replace.

I guess I should add that this "digital resistor" is driving a fuel gauge directly. The gauge is a pair of motor windings, it appears that one receives a constant voltage, and the other is varied using the potentiometer as one side of a potential divider. These two coils each want to move the fuel needle in opposite directions, they seem to "fight" each other, and the whole affair ends up rotating to a position determined by the strength of the adjustable winding.


texts: Shorting the output of both the channels of L298N

texts:
Suppose I started with a project requiring the control of motors and ended with using L298N in my project, realizing that my motor only takes around 1.5A when on load.
Now, with time I realized that my motors be more powerful for the application I was making my project and hence, I changed my motors. Now with that my motors were now taking around 2.5A when on load.
But since each channel of L298N can only provide maximum of 2A when properly heat compensated, I thought of shorting both the out pins of both the channels (one pin to one output and another to another). This will eventually make the allowable current to 4A but I believe there might be some issues that I might face in the long run.
Could anyone help me point out any of the issues that I might face?

PS: I have done this tinkering because there is an urgent requirement from the client of the product and I don't have enough time to change my core architecture. But eventually, I have been working on shifting to mosfet based H-bridge driver, which I know will not pose me much issue of current demand.


texts: I am replacing all electrolytic capacitors in an old CB radio but can't find a local source for this capacitor. Is there another type I can use in its place? Does it have to be an electrolytic type? Thanks.


texts:
I am trying to get my RC522 to work on the BBB. It works great on my Arduino which is well documented e.g. here or here. My only requirement is to read the serial # of cards which are Mifare S50.

I have tried tried using the Arduino code with elinux.org/Userspace_Arduino libraries but just get gpio issues: (I've tried export/unexport etc.)

Cape loaded BB-SPI0-01
BB-BONE-BACONE: File exists
Pin 48: /gpio/export: Device or resource busy
Pin 31: /pwm/export: No such device
Pin 60: /gpio/export: Device or resource busy
Pin 51: /pwm/export: No such device
Pin 7: /pwm/export: No such device
Pin 22: /gpio/export: Device or resource busy
Pin 5: /gpio/export: Device or resource busy
Pin 4: /gpio/export: Device or resource busy
Pin 2: /gpio/export: Device or resource busy
serial:setting baud rate to 9600

I have the BBB wired up using the SPI0 pins on P9 i.e. 17,18,21,22. These should represent gpio0 5,4,3,2 respectively.

I notice there has been use of the RC522 with Python on Raspberry Pi. github.com/mxgxw/MFRC522-python . Could this be done similarly on Beaglebone (maybe with Adafruit BBIO)? Though I would prefer using C++ as I'll be using it for other related things.

Thank you for any help or to point me in the right direction!


texts: 5V Current Transducer to 3.3V Analog GPIO Input

texts:
I am trying to find 3.3V variant of the 5V Current Transducer LTS_25-NP but so far no success. Is it possible to interface this 5V analog output to 3.3V STM32F407 analog input GPIOs?

Edit: I want to know about the 'FT' (5V tolerant input pins) for the purpose of sensor input when my MCU is powered from 3.3V power supply.


texts:
I've been working on Ethernet schematics, i noticed a network of capacitor and resistors present outside the RJ45 connector. For what reasons these passive components are used? I've attached the circuit.

Thanks.


texts: Can I use this power cord with my charger?

texts:
my original power cord I got with my laptop charger stopped working recently.
It had a power adapter rating of 10A/250V, and the part which plugs into my charger had a rating of 2.5A/250V.
I just got a new power cord and just noticed the ratings:

Here's my charger power rating and details:

Can I safely use this power cord with the adapter, or will it cause issues and cause my laptop/charger to fry?
Edit: I was researching and as I read online, it said it is important to match the voltage ratings. I'm moore concerned about the 300 V rating which will be plugged into the charging brick even though the charger specifies an input of 100-240V.


texts: Temperature sensor reading too high and heavily coupled to input voltage

texts:
I'm building a small battery powered temperature sensor gadget thing. I've bread-boarded the circuit and it worked great. I then proceeded to create small PCB out of it.

I've attached the schematic below but the basic idea was to power an attiny85 from a CR2032 coin cell and display the temperature on two 7 segment displays. The temperature is measured using the attiny85s internal 1.1V reference and is connected to ADC2.

The temperature sensor I'm using is the MCP 9700 from Microchip. It has a 10mV/degC temperature coefficient with a 500mV output corresponding to 0 degrees C. It has an accuracy of +- 4 degC which corresponds to a voltage of 40mV.

After testing all other components on the PCB and flashing the attiny85, I then soldered the MCP 9700 to the board. When I applied power, the reading was around 45 degrees C so I figured it must just be residual heat from the soldering process. I left the board un-powered for about an hour. When I switched it on again, the temperature was reading between 10 and 15 degrees too high still. I thought maybe the MCP 9700 I soldered on was dodgy, so I desoldered it and soldered on a new one. I let it cool down over night and it has the same issue.

I also noticed that when varying the supply voltage from 5V down to 3V, the output of the temperature sensor varies by as much as 10 degrees C or 100mV. The MCP 9700 is meant to be quite constant over supply voltage. The same temperature sensors on the breadboard do not exhibit this behavior.

I got the components from Digikey so I don't think they're fake or anything like that. Also, the same temperature sensors work perfect on the breadboard. The code on the attiny85 is correct. I've confirmed this by checking the raw ADC value against the output voltage of the temperature sensor using a Fluke 87V. This leads me to believe that it must be some type of construction issue. I've checked each trace over and over again, confirmed there are no shorts and that the circuit is correct.

I have been banging my head trying figure out why this is. Any ideas on what could be wrong?


texts: Question regarding Transresistance Amplifier Circuit

texts:
Something that makes me confused while reading a tutorial on the Transresistance amplifier circuit.

Here is the picture of the circuit. It basically measures the current across the photo device and produces Vout accordingly.

My question is that: if the virtual ground rule applies, that is the voltage on the negative termianal is 0V (or very close to 0V) then there is no voltage difference across the photo device. If there is no voltage difference, how come the current flows across the photo device to be measured first place??


texts: Does an antenna's radiation pattern characterize its ability as a receiver?

texts: In other words, would a directional antenna used as a receiver be more sensitive to signals coming from one direction, or be equally sensitive to signals from all directions?


texts: Measuring the capacity of a capacitor with arduino?

texts:
I'm preparing for a little Arduino project that our teacher announced that will most likely be a discharge voltage measurement of a capacitor with some curve fitting in Excel. So my goal is get the exponential curve in Excel, but I don't see how I can do that.

My idea was to charge the capacitor with a battery or whatever, and then plug in the capacitor into the GND and an analog input (A0) and read the digital value with some code.

Can anyone explain the easiest way to do this?


texts: Soft latching with button sensing and controlled power-off

texts:
I'm new to electrical engineering and not yet familiar with all the terminology and methodology, please bear with me.

What the circuit should do

I want a pushbutton to power on the Arduino. Using the same pushbutton I want to send signals to the Arduino (e.g. power off after 2 sec press). Also there has to be a way to programmatically power off after x minutes.

My approach

Below the circuit I build to accomplish this task. My idea was to use a soft latch circuit. Q1 is turned off by the current flowing through R1 and R2 by default. When button 1 is pressed, current flows through Q1, R2, button 1, R3 and to GND. Q1, being activated, in turn activated Q3, which should permanently activate Q1. To "turn Q1 off" I power Q4 to shorten Q3 to GND. sense is there to determine if the button was pressed.

This circuit does not work as it is not latching. Is my approach right, but the circuit wrong, or is there generally a better solution to fulfill my requirements?


texts: What's the difference between USB and non USB oscilloscope?

texts:
I am planning to buy an oscilloscope. I always used oscilloscopes which come with an LCD display. But I found there are USB oscilloscopes as well which can be connected to PC and get data from the PC. Since I already have a laptop I felt like that's a better choice.

But is there any disadvantage in terms of accuracy/efficiency for USB type?


texts:
As I recently learned, LED driver output voltage stands for what the pin can handle after the last cathode of LED strip. However, I am interested in this chip HV5812, that is a high voltage shift register. Do I understand correctly, that the voltage output it will provide on output pins is Vpp that I supply to it? Or are the pins working like a sink?

Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/20005629A.pdf


texts:
I'm trying to input 12v into Ardunio Digital inputs. But since Arduino digital input max voltage is 5v, I would like to use an optocoupler as a switch for 12v input into 5v from Arduino itself.

So I have got P621 Opto, But I' little concerned about the opto handle 12V??

Also for optos both in and out can withstand same voltage??

I'm only a beginner since not much able to grasp the tech jargons from the datasheets..


texts: Arduino Uno and Sonar Sensor - how long can the wire be before performance suffers?

texts:
I am setting up an Arduino Uno with a sonar sensor from Maxbotix (http://www.maxbotix.com/Ultrasonic_Sensors/MB7360.htm). The sensor will be powered directly from the Arduino (5V).

The sensor needs to be about 5 metres from where the Arduino will be located. Will using a wire/cable this long work okay as is? I plan to use a speaker cable or similar. I read the question below, but at no point does the author define what a long cable is...

Long three cables connection: can I use an audio stereo cable?

Am I okay up to 5, 10, 20 metres? What is a "long" cable in this context?


texts: Right way to connect leds to light up when pressing buttons

texts:
I want to connect leds to Cherry MX switches (push switches) so they light up when I press them.

I have 6 switches each connected to a different pin of a teensy 2, basically like this:

The diodes are 1N4148.

What is the correct way to connect the leds and resistors?

Like this?

or like this?

With this one, if more then one key will be pressed, will the leds shine brighter and potentially burn?

The leds are 3mm cheap ones, I measured with a multimeter with single led with 5V and a 200Ohm resistor I get about 23mA.


texts: ATMEGA328P Max Clock Speed Without Divider

texts:
Does anyone know what the max clock speed of the ATMEGA328P is, without the clock divider?
I know that people have been able to overclock the 328 to 30 - 50 Mhz, but I haven't found if those are using the clock divider or not.
I'm working on reverse engineering a project that uses an atmega to interface with an NES's CPU.  The clock on the circuit is a 20 Mhz clock, but the project doesn't mention what fuses to set for the atmega.  Looking at the code, it seems like the intention is to run one instruction on the atmega for each input clock cycle.
Is it possible to run the ATMEGA328P at 20 Mhz with the clock divider turned off?  In my experiments with a simple blinking LED program, the LED will phase in and out of blinking at the correct speed and blinking too rapidly.  As soon as I re-enable the clock divider (and adjust F_CPU) it blinks at a stable rate again.
Am I doing something wrong, or am I running the atmega too far out of spec?


texts: Difference between Lithium Polymer batteries of varying capacity and cell amount

texts:
I was looking to purchase a LiPo batteries online for a side project. Upon shopping around, and reading up on LiPo batteries, I have a fair understanding on what the numbers/letters on the battery packs (i.e mah,S,C, etc).

However, I noticed a wide variety of battery packs on sale, ranging from a 5000mah 3S LiPo battery pack to a 4500mah 4S and 5000mah 6S LiPo batery pack. My question is, is there any rule of thumb when it comes to mah ratings and the number of cells in a battery pack? For example, given the examples above, I would assume that the 5000mah 3S refers to the entire (3 Cells) capacity of the battery pack, with the same applying to the 6S battery pack. However, why then is the 6 cell pack more expensive than the 3 cell battery pack?

If I were to divide the mah rating equally among the number of cells in a battery pack, the 3cell pack would have 1666.67mah per cell, which is FAR more than the 833.33mah per cell in a 6cell battery pack.

OR, am I mistaken and the 5000mah refers to each individual cell in a battery pack, therefore the 5000mah 3S battery pack would have a total of 15000mah, and the 6S battery pack would have 30000mah in total, which would make it's higher price justified.

Could someone clarify this please?


texts: AD625 instrumentation amplifier simulation model

texts: I am using AD625 as differential amplifier since the input offset voltage is very low. I completed the designing part but I didn't find any simulator where  I can simulate AD625. How to simulate AD625 using LTSpice? Or is there is any simulator available where I can simulate AD625?


texts:
For the kids of my electronics tinker club, I thought it would be a great experiment to see how the resistance of a wire is proportional to its length.

Therefore I made a very simple circuit consisting of a single resistance wire with ~1.1m length which can be measured in 10 pieces of ~11cm.

Here's how the wiring diagram looks:

(We'll only use an Ohmmeter to measure the wire, so no other parts are needed)

While the circuit is simple enough, I still try all the circuits myself before I give it to the children. And I find that soldering that resistance wire is really difficult.

The resistance wire is labelled RD 100/0.1 and has a resistance of 62.4 Ohm per meter. The brand is Isotan and the fomula seems to be CuNi44. The German data sheet even says "Isotan is simple to process. The alloy can be soldered and welded easily.".

I'm soldering as a hobbyist for more than 20 years and my solder joints are usually not so bad. However, on this circuit, I really sucked. On some solder joints I couldn't even measure the resistance.

Increasing the temperature seemed to help, but the solder joints still look ugly. How does one solder that stuff? And hint on how the kids will manage to solder this?


texts: How to determine the transfer function of a system including disturbances

texts:
I'm trying to determine the open-loop transfer function of the system below (in order to determine PID gains).

If I account for the disturbance \$(9.81*6700)\$ in the system and use equation 2, I get very different results when I compare a simulation of the simplified function to a simulation of the full network.

If I disregard the disturbances as zero and use equation 3, and I also disconnect the disturbances in the simulation, the results match.

How should I account for the disturbances when determining the transfer function? And why is the method I'm using incorrect?

Thanks in advance.


texts: I am attempting to build a very simple 4 bit counting machine using a CD4029 ic and a 555 timer.  I have built my circuit on a breadboard and everything seems to be working perfectly, however on the power up of the circuit the outputs id the CD4029 seem to be set to random values and not to 0000 as I had expected.  I need my counter to start at 0 for the project I am working on.  How would I manage to achieve this.


texts:
I'm working with some 230 VAC resistive heating elements which are switched by a solid state relay (https://uk.rs-online.com/web/p/solid-state-relays/9045728) and driven by a 4-20 mA signal from an external PID controller. There are 4 x resistive elements and all of them are in parallel. The resistance of the elements (before the initial test) were as follows:
R1 = 86 ohm
R2 = 85.5 ohm
R3 = 85.7 ohm
R4 = 86.9 ohm
The test was then conducted with all 4 x resistive elements inside a stainless steel cylinder bonded with thermal compound and the temperature raised to 600°C and controller via the external PID controller.
I'm having some problems with the resistive elements themselves. For some reason, after around 10-12 hours of testing one of the elements either short circuits or goes open circuit (I've run this test multiple times and I continue to get failures). My questions therefore are as follows:

Is the reason the element is going open / short circuit because the SSR is too harsh on the elements themselves? Should I instead be using a Silicon Controlled Rectifier that will allow a gradual voltage change across the resistive element? Something similar to this: https://uk.rs-online.com/web/p/signal-conditioning/8513563

When one of the elements goes open or short circuits, the resistance of the other elements jumps from around 80 ohm to >200 ohm (Note that I'm not measuring in parallel, I take each element away and measure the resistance). Is the reason for this similar to the thermal runaway effect found in diodes and transistors in the respect that if one element breaks, the other elements will try to compensate by maintaining the same level of current?

For information, the resistive elements are 230 VAC devices and are capable of handling up to 700°C. The chamber in which the elements are installed only reaches 600°C and the maximum temperature the elements themselves reach is around 610°C so the elements themselves aren't overheating.
The elements after their 600°C test and after returning to room temperature changed to the following values:
R1 = 85.7 ohm
R2 = 84.8 ohm
R3 = 85 ohm
R4 = 85.9 ohm
The jacket of the chamber is water cooled by a booster pump that provides more than enough cooling capability to keep the entire chamber at ambient. I would suspect that we're overdriving the elements rather than overheating them.
Thanks in advance for your help. Happy to provide any additional details as required.


texts: T-bird taillight control unit digital logic help

texts:
I am currently working on designing a t-bird tail light control unit. The requirements for the system are presented on the table below:

I have a full circuit made which I'll provide in the screenshot below:

So far, my circuit works for all of the scenarios EXCEPT for when the left/right lights are supposed to flash while the other set of lights is supposed to be on. What happens is when I OR the B input with the output of the AND gates from the state machine, the lights that are supposed to flash do not since B is feeding the OR gate a constant 1, however the other set of lights that are supposed to constantly stay on do stay on as they should. I have been struggling trying to solve my problem here but have not been able to so I came on here for ideas. Any help will be appreciated.
(The circuit works for all of the scenarios except the one mentioned above.)


texts: Mesh current formulas gives two different results for i2. Why does the first loop provide an incorrect current value?

texts:
Mesh current formulas gives two different results for i2. The formula derived from the second loop provides a current of 1A which is the correct answer. However, when I write my equation using the first loop I get a current of 5A. Why does the first loop provide an incorrect current value? My work is below. I also provided a screen shot of multisim verifying the correct i2 value should be 1A.

Multisim verifying i2=1A


texts:
I am using an atmega16 micro controller with a 12MHz external crystal oscillator. But I came to know that the internal clock frequency is 1MHz

I need to calculate UBRR value for serial communication. I need a baud rate of 115200.

If I am using 1MHz in UBRR value calculation by using the formula (F_CPU/(16*baud))-1 then I am getting a negative number greater than -1.
What should be the value of F_CPU?

please do help me as I not an electronics guy.
Thanks in advanced for any help...


texts: Suggestions for 1-5 km range wireless communication?

texts:
I am developing a VOIP application. Most clients use a wired Ethernet connection, but some of the clients need to have a wireless connection. Currently the core board is using:

Cortex-A8 (TI AM3359)
256MB RAM
2GB Flash
WiFi 802.11N

But the range of WiFi is very terrible, compared to ~5Km walkie talkie, I know XBee might work but I have never used it in either production or development. My requirements for the digital wireless communication are:

1-5Km in Range (1Km with minor obstacles or 5Km line of sight)
100Kbps (12.5KB/s) lowest transfer rate condition.
multiple clients (100 clients)
relatively low price.
preferably: support TCP/IP, support simple encryption (so no need to modify software stack much)

So should I use XBee? or any other alternatives? Thanks.


texts: What happen, inside the XBee S2 module, after a Network ACK Failure (ACK timeout)?

texts:
Consider sending a ZigBee Transmit Request frame with a frame ID greater than zero (so, I will receive a ZigBee Transmit Status frame). Suppose I set my timeout response to 200 ms, then, when timeout response is triggered I will receive a ZigBee Transmit Status frame with a status of Network ACK Failure.

I would like to know what exactly happen inside the XBee S2 module: the response can still be received? Or the module block any response that would be received?


texts: I have an adafruit motor with a power supply voltage of 15v (Max) and a output current of 1.2v (ave)/3.2v (peak). I want to use it with a stage table that has two stepper motors. One motor uses 0.6amps and the other is 0.8 amps and the stage table has a driving voltage of 24v DC. Can i safely use these two things together?


texts:
We worked two years on and off on this project at my friend's place. Finally we finish, I take it home. There's a power supply unit but it can't be connected directly to mains, it expects some lower AC voltage. There's a bridge rectifier and a cap directly after the input. I had an 18V AC adapter and connected it. I knew that 18V was an overkill for the 10.5V DC we needed in the end, but the device doesn't draw so much so it wouldn't get too hot, I figured.

The device worked well. I had it turned on for a while and played a bit. Then I started to smell an odd scent. I move closer to the device, smell, and indeed, it's coming from the device. I want to turn it off, but was just half a sec too late and BANG. The big capacitor in the PSU was blown. It was rated 2200uF/16V. Stupid. I can be happy we put the device already in its case, otherwise it would've exploded in my face.

Anyway, what do I do now? Of course, I need to replace the capacitor itself. But I heard once that there's acid inside the capacitor. Can I safely touch the capacitor to remove it or are there safety issues? And what is the best way to remove the small fibers that are everywhere? How should I go about that, a safe way?

Then, do I need to worry about the circuit around it? Everything worked fine until it exploded, so I don't think other components suffered over-voltage or something like that - but could other components be damaged because of the bang? There's some LM317s, the bridge rectifier, some potentiometers, and some small capacitors. A bit further away, what I'm most worried about, the DDS and a crystal oscillator - you can see it on the picture, the DDS is on the green board next to the crystal oscillator.

And then there's the smoke and the smell - is it dangerous? This is my bedroom.

The PCB with the DDS (in the bottom right of the picture) seems to have gotten some damage on the bottom. The copper traces don't conduct anymore when measuring on the copper, there's some kind of foil on it. The parts themselves are still connected though, when measuring from part to part. Would this be a problem?

And finally, out of curiosity. What would have happened if there wouldn't have been a case around it? Now, the case of the capacitor blew against the case of the device, so the cap couldn't 'explode completely'. What would've been the results if it could explode completely?

Here's the circuit diagram of the PSU. The white dot in the center is an alternative ground symbol.


texts:
I have a bunch of diodes of the same type on a schematic in LTSpice. How do I parameterize the diode's type (Value) so that I can change it in one place and it would change it for them all?

The .PARAM statement doesn't seem to be supporting literals, so I cannot use something like

.PARAM DiodeValue=NSPW500BS


texts: Adding the AVR Dragon's HVPP to the Arduino IDE

texts:
I would like to teach my Arduino IDE to use my AVR Dragon's HVPP (High Voltage Parallel Programming) interface to upload compiled sketches to my boards (an ATMega1284P-PU in this case, supported by mighty1284p).

Working setup so far:

Arduino IDE with mighty1284p, I added this to the boards.txt of mighty1284p to support my uC's internal-RC-oscillator clockrates of 1MHz and 8MHz.

avrdude can talk to the m1284p and set the fuses:

avrdude -c dragon_pp -P usb -p m1284p -U lfuse:w:0x62:m -U hfuse:w:0x99:m -U efuse:w:0xFF:m -U lock:w:0xFF:m

I can compile / check a sketch successfully, then upload the temporarily created .hex manually to the 1284 using the Dragon:

cd /var/folders/px/xmf1dygn6p5_fn1hh05c6gyr0000gn/T/build4082512148637729777.tmp/
avrdude -p m1284p -c dragon_pp -P usb -U flash:w:Fade.cpp.hex

This works but includes the manual step of cding into the temporary build directory and manually uplading the .hex.

How would I use the AVR Dragon's HVPP directly from within the Arduino IDE? I have added a section to programmers.txt as such:

dragonpp.name=AVR Dragon HVPP
dragonpp.communication=usb
dragonpp.protocol=dragon_pp
dragonpp.force=false

which I assumed would be correct for the above avrdude parameters.

Within the IDE I choose Tools - Programmer - AVR Dragon HVPP, the Upload. The debug output shows this:

(...correct compiling, linking and such...)
/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/avrdude -C/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/etc/avrdude.conf -v -v -v -v -patmega1284p -carduino -P/dev/tty.Bluetooth-PDA-Sync -b115200 -D -Uflash:w:/var/folders/px/xmf1dygn6p5_fn1hh05c6gyr0000gn/T/build1852336263469118058.tmp/Fade.cpp.hex:i

avrdude: Version 5.11, compiled on Sep  2 2011 at 18:52:52
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2009 Joerg Wunsch

         System wide configuration file is "/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/etc/avrdude.conf"
         User configuration file is "/Users/cts/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : /dev/tty.Bluetooth-PDA-Sync
         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.

So the -p parameter is correct, but -c and -P are wrong.

Any ideas how I could add the Dragon correctly?


texts: Will this high side p-mosfet switch circuit work?

texts:
I have two micro-controllers on a PCB. Both operating on 3.3V. One microcontroller will always be running. I need to cut off the power supply to other micro-controller sometimes. (This is not for power saving. I need to power cycle the micro-controller) For this, I am making a high side switch using p-mosfet. Here is one question I posted earlier. As pointed by some talented members, I can use a mosfet. Here is the circuit that I could come up with:

Load is a microcontroller and some other circuit such as optocouplers. I want the switch to be normally closed. Hence I have used R2. I am planning to use R2 = 10 kohms. Will it be fine? If not, what will be a more suitable value?

Current requirement approx 200 mA. Consider a worse case scenario of 500mA.

Working: Whenever I want to cut off the power supply to the other micro, I will just set the 3.3V_LOGIC pin to HIGH. Once I want to resume the power, I will set the 3.3V_LOGIC pin as an INPUT pin, making it a high impedance pin and allowing R2 to take over, turning ON the power to the other micro. Will this work as intended?

Another doubt point: Both micro-controllers are communicating over i2c. Is there a possibility that other micro draws power from i2c lines and remains alive while I turn off the mosfet? Will declaring the i2c pins as output and setting them LOW ensure that other micro-controller switches off?

I am using DMP2100U-7 p-mosfet.


texts: Why is it beneficial to have a diode in series with a VPP resistor?

texts:
I have found a programmer for the AT89C2051 microcontroller here:

http://www.oocities.org/dinceraydin/8051/index.html

I have created a version similar to it. What's common with both versions is that none have a diode between the VPP pin and 12V. Just a resistor only.

My programmer does work but after several programming attempts (way less than 1000 per chip), the chip decides to no longer be programmable.

I remember that someone suggested that I should use a diode and a resistor between VPP pin and 12V.

So I'm curious as to what diode is best and what makes it so beneficial?

In the future, I want to program the AT89C4051 with the same programmer.


texts: 8 bit PC integrated with VGA video card (similar to ben eater project)

texts:
I'm thinking about making a project like this one and add a graphics card like that one. Using an EEPROM for the video memory and changing its content setting it in write mode and assigning a value for every pixel that need to be change. The problem is that the CPU will run at a very slow frequency, so the change will require some time and in this interval the monitor will show nothing (if I will disconnect the output signal during writing) or constant color lines depending of the value that is being changed (if I will leave the output connected).
Is there a way to "freeze" the image on the monitor during this operation? Or are there better solutions?
Till now my last idea was to use two EEPROM with the same content and change the value in one memory while reading the data from the other, then read from the first memory while writing the same data in the second one (flipping the roles of the two EEPROM); but it seem extremely inefficient to me.
PS: I didn't find any documentation for freezing the image using simply the VGA lines.
EDITS:

I was thinking to use ROM so that I can preload a fixed background and change fewer pixels while running (to save time and memory)
This will be just for fun, without any real practical use, so I didn't think a lot about the frequency, but I can imagine from few Hz (while debugging or for demo purpose) to few kHz, while the "video clock" will probably be 10 MHz, so write in precise, small and synchronized intervals is not a easy  task, I think.


texts: In parallel current sources with capacitors

texts:
I have to get the correct equation of multiple parallel non-dependent current source in parallel with capacitors, as i seem to find the correct solution, the resulted simulation in LTSpice shows different results.
Using Millman theorem and considering that $$I_1=I_2=I_3 = 0.000078cos(31.41t)$$ and $$C_1=C_2=C_3 = 45nF$$ i found that $$I_R(t) = I_1/((1/3)+(3(RCw)^2))$$ which gives me 56µA max at output.


texts: 4-pin 1.27mm pitch ribbon cable - cable to cable conectors?

texts:
I am looking for a connector type that can mate two 4-conductor, 1.27mm pitch ribbon cables together.  Preferably IDC style, but at this point I'm willing to try anything that isn't too ugly.  They can be male-female arrangements or non-gendered self-mating arrangements (or something else I haven't thought of).

Everything I can find so far are wire-to-board solutions where one or the other of the mating connectors are board-mount types.  I need both male and female to be IDC-terminated so that I can connect cable to cable (both cables will be hard-soldered to circuit boards at one end).

In larger conductor sizes these things are ubiquitous so I made an incorrect assumption when I designed the boards that I'd be able to find a connector solution and I am really struggling with this.  I sized the holes on the slave board to fit the ribbon cable directly (soldered into holes), so none of the board-mount connectors will fit.

Does anyone know of a part that might work, or some other kind of solution?

For additional clarity, here is a drawing of my problem:

(I2C Master PCB) X ----- 0 ----- 0 ----- 0 (and so on)
(I2C Slave PCB)  X ----- 0

X = hard-soldered connection
0 = inline connector (free-hanging, attached to ribbon cable)
- = ribbon cable

So the idea is that i want to be able to connect (or disconnect) any number of slave devices from the ribbon-cable bus.  But I am having trouble finding appropriate connectors that will cleanly mate to 4-conductor, 1.27mm ribbon cable.  Anyone have any ideas?  Thanks!

Update
In the end I have just designed a small adapter PCB that lets me connect a 4-wire ribbon cable to a standard shrouded pin header.

I appreciate all of the suggestions.  In the event, none of them could really work due to the odd nature of the application and the small number of them being made (i.e. no custom stuff).  The slave devices are only 14mm x 22mm, so we couldn't put a connector on the board without doubling the size, hence the 4-wire ribbon cable. Thanks again


texts: Need some help in understanding this circuit

texts:
This circuit is taken from this website.
http://www.circuit-finder.com/categories/sensor/temperature-sensor/905/temperature-controlled-switch

What is the purpose of R2 and R3 in this circuit?

I use voltage divider rule to calculate R2 which is R2/(R2+P1+R1) * 5V = 4.6987V
Converting it to degree Celsius , it is 46.987 degree Celsius.

Does it mean that the range is from 0 ~ 46.987 degree Celsius? Only when the sensor voltage rises above the ref voltage level for P1 (which is around 0.06 V = 30 degree Celsius since P1 is set to 10k ohm) , the output of the comparator toggles to the full supply voltage level

The purpose of R3 is it to limit current flow?


texts:
I'm picking through Protective Relaying Principles and Applications by Blackburn and Domin (4th ed), and am currently figuring out distance relaying. Intuitively, I understand their operation. However, I cannot figure out how they derived the equation (6.4) for the mho circle. I expected Zop = (Zr/2 ∠ θr) - (Zr/2 ∠ θ+θr) and tried to see if it was equivalent, but could not.
I also believe (6.3) is incorrect; since the the line before desribed the voltage as line-neutral, there should be no sqrt3 in the denominator. This would also mean that (6.6) and (6.8) are incorrect.
Routledge.com has a pdf of errata available for download, but the link returned 403 Forbidden. I emailed customer service to ask about it. Are these actual typos, or am I missing something?


texts: Concerns using a sound card as an oscilloscope using xosope

texts:
Stated quite appropriately, I am in the "tinker with it and learn about it" stage of electronics.  Have assembled and played with some audio circuits, Arduino bare bones kits, some automotive add-ons, etc.

I have installed xoscope and interested in using it for the learning experience.  I've looked at a buffer / opamp circuit for the probes going into the sound card:

I have also just ordered in these probes to use.  According to the data sheet for the probes, they are designed and calibrated for use on any oscilloscope that has an input impedance of 1MΩ and whose input capacity is within the compensation range.

Now, again, I'm just a tinkerer, but don't want to damage the sound card.

Is such a buffer circuit really required for sound card input ?  I can also see the opamps in the schematic for x10?  amplification, but the probes I've ordered have that built-in.

I cannot foresee ever using the probes on mains, etc...  Just small-scale "peeking at what the signals are doing" kind of things.  Would just a 1M resistor between the probes and sound card suffice ?

Any knowledgeable advice is greatly appreciated.


texts: Turn on voltage by using smaller voltage

texts:
I'm wondering if there's a way to create a current controlled voltage source. At the moment I have a mosfet (NPN, PN2222) connected in series with a positive 5V terminal and ground. I control that mosfet using a ~2.5 V input voltage. What I wanted to do was create a 5V output when the mosfet is on. However, mosfets can only be connected in series, with the voltage on one end being necessarily higher than the other for it to turn on. Is there a way to output a voltage using only a mosfet, A 5V source, 3 volt source to turn on the mosfet, and ground? Basically, if the 3 Volt source is connected, output 5 volts, otherwise 0 V. I only have 2 diodes and 2 mosfets and a handful of resistors to use.

Something like that ^. Obviously that doesn't work because there's no voltage difference and so the mosfet doesn't turn on even when 3V is applied to it, and that's where I'm stuck.


texts: I know that crystal oscillator is a type of oscillator. But why in colloquial terms crystal is different from oscillator and how they are physically different?


texts: Transients in Capacitive Networks (The Charging Phase)

texts:
Our class is dicussing capacitors during the charging phase, steady-state phase and discharge phase. There is a specific problem that I am concerned with. I believe the answer sheet is showing a error. The majority of us have the following answers for this specific problem. The error is the Answer belonging to the first time interval (1T). The other intervals (3T and 5T) were correct.

1T = 16.6465 V

3T = 19.9057 V

5T = 19.9973 V

Again this is for problem 19.C.. Could anyone else comment on what your getting as an answer and if i'm doing something wrong. The answer sheet is saying something different for the first time interval (1T). Again, I believe the answer sheet is showing an error in which I would like some support before I take it higher.

Attached is a photo of the problem and my work for the problem. Again 19.C. is the only part of this problem that I'm concerned with. The picture was fuzzy therefore I redrew the figure 10.94 in my proof of work as you'll see. I did this cause the value of the capacitor (5.6 micro F) is fuzzy.


texts: evaluate number of poles lying on the right,left side of s-plane and on the jw-axis?

texts:
the transfer function is \$\   T(s)= \dfrac {1} {2s^5+3s^4+2s^3+3s^2+2s+1} \$
I solved it using RH criterion by evaluating the columns but results are different when i solved it with by matlab they are different.


texts:
This is "part 2" because my original question has only brought up more queries that i am unable to solve. The first part can be seen here for any who are interested:
"Hot-knife"/Thermal cutter power supply design

I apologize for making two posts for the same project but my other has seemingly died :(

currently i am trying to construct a thermal knife to cut and seal ropes, both to avoid expensive store bought ones and as an educational project. i have bought a blade online to use that is supposed to be 60W, it can be seen here:

==================No longer relevant, see update========================
To obtain 60W of power im going to use a 60VA transformer to transform 240VAC, to 4V 15A output. so now my speedbumps:

I understand 15A is a very large current so will a voltage of 4V be low enough to be safe?
Before building, I wanted to test these conditions using a benchtop supply. When i connect the blade across the two terminals however i cannot get the voltage to go above 0.6V, even pushing the current to the supplies max of 20A. This would only dissipate 12W of power not the 60W i had wanted to test. My theory is that this is due to the extremely low resistance of the blade which according to V=IR would require a very large current to produce a moddest voltage. Any thoughts on another way to test before committing to the transformer?
I have been told a ceiling fan speed control is a good addition to fine tune the current going to the transformer. using Australian mains of 240VAC, would something like this be appropriate?
http://www.ebay.com.au/itm/AC-250V-50-60HZ-Fan-Speed-Rate-Control-Rotary-Button-Wall-Panel-Switch-/301422113787?pt=LH_DefaultDomain_15&hash=item462e2873fb

Thank you for any and all help :)

===========================================================

Edit - Update 1

Request was made for blade datasheet, it can be found here:
http://www.saferight.com.au/_literature_167996/Hot_Knife_Datasheet
Am i correct in assuming a 60W power draw for the blade? It is possible that some of this power is used by other components in the tool, in which case i think my only option would be a guess and check method as I have been unable to find any other useful datasheets.

I have done some measurements to deduce the resistance of the blade (far too small to measure on a multimeter). Set the power supply to constant current (CC) and then measured the voltage across the blade at different intervals. tabulated V/I using excel and I believe the resistance is 8.39mOhm

Using P=VI and V=IR with the data P=60W and R=8.39mOhm yields values of I=84.57A (im going to need some thicker cable) and V=0.7095V

Being on mains of 240VAC, this would indicate an effective transformer ratio of 338 (using N=240/0.7095) i should be able to achieve this by modifying a transformer as shown in the link provided by Bruce Abbott.

Thank you all, The advice (and scolding) have been a great help thus far, please tell me if this new theory is on the correct path before i start asking around for bigger power supplies to test with.


texts: Shift registers, flip-flop, Multiplexer & Demultiplexer with microcontrollers utility

texts:
While i read alot about the popular 74HC595 shift register and its use for multiplexing i can't find anything about the following chips:

MC14053B

Triple 2−Channel Analog
Multiplexer/Demultiplexer

74HC574

Octal D-type flip-flop

The above chips should also be suitable for multiplexing / handling more outputs with less pins, right?
I'm not an electronical engineer.. so my knowledge about those ancient chips is limited.

Anyway i'm curious what was the main purpose of this chips and why noone is using them anymore with microcontrollers.

Said that, i have 2x MC14052B & 1x 74HC574. Those parts where taken out from an old sat reciever. And i assume they where there to drive , at least one of them, a 4 digtit 7 segment display.
This brings me also to ask if somehow i could use them to drive that display again with an arduino using LESS pins.

Note.: i also have some of the following i2c chips with 8 ports. As i already have a 16x2 display driven by a pcf8574, the combination of the above chips with this one would allow me to drive the diplay with i2c.

PCF8574 ch 8bit 8-bit I/O expander for
I
2C-bus

While this appers to be 2 questions, it's just one. If you explain me the use of those chips i'm prolly able to use or not the chips with the 7seg display.At the other side if you explain me how i could hook up the chips with a microcontroller i would understand the usefullness of those chips.

I love IC's, i really want to find something to do with them before throwing them away. I hope you understand me and can help me to undertstand.


texts: Mulitple open-circuit transmission lines

texts:
I'm using a single SPI microcontroller to talk to about 10 boards. Of course, only one of them is actively listening at a time, using chip select (for the unfamiliar, when chip select is high, the SPI inputs are high-impedance)

But, the clock/MOSI lines are going to be connected to all of the boards. There is no end-termination. So when talking to one board, the other 9 are high impedance; so, can I expect 9 back-reflections? If my logic voltage is 3.3V, might I end up with 3.3*9 volts at the source? (!?)

If this is the case, should I series terminate each line according to the transmission line impedance (ribbon cable, so ~100 Ohms)?

edit: Rise times of the digital signals are ~7ns. Time spent high or low is ~20ns.

edit2: My reasoning of 9*3.3 was based on this nice simulation a fellow stack-exchanger made: http://helloworld922.blogspot.com/2013/04/online-transmission-line-simulation.html

If you have no series termination and high impedance, you get up to 2*Vin at the source on the back reflection. That was just one wire; I just scaled that up for 9 more reflections. Is my logic flawed?


texts: Does a transistor amplifier produce negative voltage?

texts:
So I've recently started electroncis and bought this course on udemy ("Electricity and electronics - Robotics by Ian Juby") and I'm slightly confused as to how the circuit that I've attached to this post works.
An AC signal is applied to the transistor base which turns on and off the transistor. I understand how that works. What I don't understand is that the instructor is saying that the voltage on the output swings negative with the AC signal. But surely the output would only go to 0V as the input voltage is DC from collector to emitter and the transistor is on (It's an inverting amplifier) and therefore the resistance is extremely low and therefore the voltage divider output would be 0 and not go negative?
Thanks!


texts: How to control output voltage on a Buck Converter

texts: I'm fairly new to electronics and I have copied the Buck Converter (LM2678) in the picture attached to convert 24V to 5V. After trying it I have actually converted 24V to 9V and my question is if I have done something wrong or if the schematic is wrong? The output voltage is apparently controlled with the two resistors at Vout although I can't seem to figure out how that works, so if anyone could explain that to me I would also really appreciate it, as it would help me troubleshoot!


texts:
I'm making a program for the msp430 using energia launchpad, the first code that I had is the following:

// display flag
boolean flag_display = false;

void setup() {
  // define ISR to activate the display
  attachInterrupt(PUSH2, display_ISR, CHANGE);
}

void display_ISR() {
  clean_leds();
  flag_display = !flag_display;
}

void loop() {
  if(flag_display == true) {

    // prints the number 45 on the display
    pick_digit(1);
    pick_number(4);
    delay(8);
    pick_digit(2);
    pick_number(5);
    delay(8);

  }
}

Basically the program presents the number 45 on the display every time the button PUSH2 is pressed and cleans the display every time the button is un-pressed, the problem is that sometimes (when the button is un-pressed and the program is still on the first delay) the number 5 in the second digit stays present, so I used the following to bypass this problem:

// display flag
boolean flag_display = false;

// delay flag from the display
boolean flag_delay = true;

void setup() {
  // define ISR to activate the display
  attachInterrupt(PUSH2, display_ISR, CHANGE);
}

void display_ISR() {
  flag_display = !flag_display;
}

void loop() {
  if(flag_display == true) {

    // prints the number 45 on the display
    pick_digit(1);
    pick_number(4);
    delay(8);
    pick_digit(2);
    pick_number(5);
    delay(8);

    // if the code runs till the end, un-flag the delay flag
    flag_delay = false;

  }

  // Keeps cleaning the leds until the delayed code is over processing
  if(flag_display == false && flag_delay == false) {
    clean_leds();
    flag_delay = !flag_delay;
  }
}

But I read that over using flags in your program is a bad programming practice and my solution doesn't seem elegant nor power efficient, since the line:

flag_delay = false;

Is going to keep being processed every time the display is on, and the function clean_leds() is going to keep being processed until the delayed code is over.
Is there a more efficient way of using the ISRs and flags in this particular case? Thank you.

The clean_leds() function is has follows:

void clean_leds()
{
  digitalWrite(P1_7, LOW);
  digitalWrite(P1_6, LOW);
  digitalWrite(P2_5, LOW);
  digitalWrite(P2_4, LOW);
  digitalWrite(P2_3, LOW);
  digitalWrite(P2_2, LOW);
  digitalWrite(P2_1, LOW);
}


texts:
Lets say I have a linear circuit with some input and output voltages. Assume this is a block with inputs/outputs. When I connect input of another block to the output of my first block, I observe that my first output will change but I don't want it to change or I want to be able to foresee this change and interfere beforehand to sustain my second block with that original output signal.

What can I do about it?


texts:
this is a series resonant half bridge, used with a loosely coupled coils (so there is significant leakage inductance)
a decoupling capacitor for the half bridge is used (not shown in schema) (maybe it's not well tuned.. the half bridge circuit used is a tiny board with the capacitor)

When we observe the ouput of the half bridge ( voltage and current ) we have this :
 near resonance
 for the second one resonance is at 50 kHz

the magnetic coupling isn't the same for the two experimental tests. i need leads on the cause of the voltage overshoot. stray inductance in the mosfets? i don't thing so for this voltage leve (10V input)
 i am suspecting the recovery of the free wheel diodes?

thank you


texts: Transient power supply with LM317 and LM2576

texts:
I have a power supply to power an 8W LED board and a Raspberry Pi.

I have used a 24VAC (12-0-12V) 2A transformer to feed the bridge. I have also used a LM317 to provide a voltage of approximately 15.8V for the LEDs.  The output is also used by the LM2576 to provide the 5V for the RPi. The V+ socket is connected to the LED PCB through a switch and the return to ground is an unbroken connection. The Rpi is always ON. The LEDs consume 500mA at 15.8V and the RPi consumes a maximum of less than 1A at 5V (measured using an ammeter.)
When I power ON, with the switch connecting power to the LEDs (full load,) the circuit works without a problem. However, when I switch off the LEDs after power ON, soon after a few seconds the RPi also goes down. The 5V output is now 2.3V and not sufficient for the RPi. The V+ reads 2.8V to 3.3V.
Even if I power on without the switch connecting power to the LEDs, the RPi soon shutdowns due to low voltage.
This is really puzzling for me. How can a power supply work fine at full load but fail at lesser loads? Has anyone had such issues before and if so how did you solve it?


texts: 5V LDO blowing up only when testing current draw

texts:
I have a circuit to power some 5-volt logic from a +24VDC source. It has some basic reverse-polarity protection and uses a TI 5VDC LDO.

It all works great during normal operation however, when I use my FLUKE multimeter in amp mode to test the current draw like so:

The LDO blows up immediately. Smoke, sparks, a bright light, all of it.
Anyone know what's going on?

Thanks


texts: Can I connect 5v 1 amp usb mobile charger to power Node MCU?

texts: I am planning to power Node MCU from cable power. Can I connect mobile charger to the micro USB port? Or is it better to connect to Vin in NodeMCU?


texts: Three Phase Rectifier Question (student)

texts:
I am new to this forum. I am an Electrical Engineering student working on a project. I am using Matlab Simulink/Simscape to perform simulations.

Currently, I am working on a three-phase rectifier. (see photo below)

I am not getting the desired waveform on the output. Does anyone have any advice?

I know my input phases are current. I viewed them on the scope and they are 120 degrees shifted.


texts:
I am generating a 5V PWM signal from my MCU (an Atmel ATMEGA1284P). I need to convert this to a 12V PWM signal. For this I designed the circuit below, something very similar to a Sziklai pair, but adapted to match this case.
It uses a bipolar NPN transistor to drive a bipolar PNP transistor. Ideally, I would need V_LOAD to be a 12.0 V PWM.

I ran a few simulations and this seemed to fulfill the purpose really well, until I remembered C_LOAD. Since V_LOAD is not actively pulled down when CLK2 goes low, the fall time is very long (too long, about 25 μs).

Any ideas on how to improve my design? Or should I trash this and use something else?

I apologize in advance if this has been asked before.

Some clarifications: The maximal current I'm going to drive will be around 10 mA. I have some pretty harsh specifications to fulfill: V_LOAD should be 12.0V and the rise and fall times (10%-90% = 1.2V-10.8V) should maximally be 2 μs,

EDIT:
Thanks for your answers. Here's what I ended up using: Simulation.

It's based on Majenko's answer with two transistors added as gate drivers to reduce the time it takes for the PWM to go LO. Furthermore, MOSFET's with low gate capacitance have been chosen (BSS84P and BSS138). The fall time then becomes 3 μs.


texts:
I'm really new in designing PCB(it's my first one) and i'm using Eagle Cad do it, however i have no idea on how to connect an outside wire to the PCB(either in the schematic or in a real circuit board). In this case the wire only needs to be connected to GND don't know if its easier or not.

thanks


texts:
I want to minimize the price of the device (board) with the next functionality: it connects to M2 and supports SATA to internal emmc memory (access to memory through functional block).
That functional block could be as any controller or something -- should be programmable.
So, my question is: what platform can you advise to use as a functional block?
For me, it seems not bad to use TI AM1808.
Also, there is ideas to use some usb-sata bridge, to have something like (with no success for sata-to-usb adapter)
sata host| ] --> [ |sata to usb| --> | (usb) mcu (emmc) | --> emmc ]
   host-side     board-side


texts:
I am doing a project where I have to design a PCB. I am new in this field. I am using EAGLE PCB software.

About my project: I am working on a project where I have to measure the environments temperature. I am using TI's CC2541 Bluetooth soc, temp sensor TMP102, DC DC convertor, SOC debug flash TSW-105-02-S-Q and MURATA's Balun transformer. Whenever I put the battery in my PCB, the temp sensor reads the data and send it to my phone via Bluetooth. For this PCB design I am using Eagle software. I am new to this software and am working alone in this project.

Until now I have the schematic design on software. I am attaching my PDF file here, so you can check the file and tell me if I am going in a right direction or not.

And also how to check the design if it is correct or not? I clicked on the error button, it is showing warnings only not an error.

Here is the link for the PDF file of the TI sensor tag.


texts: How to make blinking led without using any ic?

texts: I want to make a blinking light for my transformer when I charge anything with it. But as an educational exercise, I don't want to use any kind of IC. Can anyone help me?


texts: I got this circuit from internet. I don't know why the capacitors are installed in this circuit. Can somebody tell me the reason of these capacitors..


texts: Altium: Components don't move with their room

texts:
I have a design with several rooms in it. I did a part of the routing and I don't know what I did, but now when I move a room, the components don't move with it.
I found something in the documentation:

Once component(s) have been assigned to a room, they move when the room is moved. To move a room without moving the components, temporarily disable the associated Room Definition rule - either in the PCB Rules and Constraints Editor dialog or in the PCB Inspector panel (with the room in question selected in the workspace).

But I wasn't successful with this help...
What should I do?


texts: what is the meaning of NOP in the schematic diagram?

texts: what is the meaning of NOP in the schematic diagam?


texts: Why don't any countries use 360-volt or higher mains power?

texts:
The vast majority of countries use ~240-volt mains electricity, although a few early adopters (such as the United States and Japan) still use ~120-volt mains electricity.  240-volt power has the advantage of having lower resistive losses than 120-volt power, and, thus, not requiring conductors as large as those found in 120-volt countries; however, countries that electrified early, when 120 volts was still the only game in town, are stuck with their lower mains voltage because switching to 240 volts would be too much trouble.

Since using even-higher-voltage mains power would decrease losses still further, why don't any countries use 360-volt, 480-volt, 600-volt, or greater household mains power?*

*Partial exception: 240/400-volt three-phase mains power is apparently somewhat common in northern Europe, but my question isn't about three-phase power.


texts: Why does more bandwidth mean higher bit rate in digital transmission?

texts:
I understand that similar questions like this one have been asked before on this site, listed below. However, I am confused about the answers. If I explain what I think I understand, can somebody please point out where i'm wrong?

why-more-bandwidth-means-more-bit-rate-per-second
why-do-higher-frequencies-mean-higher-data-rates...

I'll start with what I do know:

Shannon Law gives the theoretical upper limit

$$C_{noisy}=B*log_{2}(1+\frac{S}{N})$$

if S = N, then C = B

As N→∞, C→0

As N→0, C→∞

Nyquist Formula says approximately how many levels are needed to achieve this limit

$$C_{noiseless}=2*B*log_{2}M$$

(If you do not use enough logic levels you can not approach the shannon limit, but by using more and more levels you will not exceed the shannon limit)

My problem is that I'm having a hard time understanding why bandwidth relates to bit rate at all. To me it seems like the upper limit of the frequency that can be sent down the channel is the important factor.

Here's a very simplified example: No noise at all, 2 logic levels (0V and 5V), no modulation, and a bandwidth of 300 Hz (30 Hz - 330 Hz). It will have a Shannon Limit of ∞, and a Nyquist Limit of 600bps. Also assume that the channel is a perfect filter so anything outside of the bandwidth is completely dissipated. As I double the bandwidth, I double the bit rate etc.

But why is this? For two level digital transmission With a bandwidth of 300 Hz (30 Hz - 330 Hz), the digital signal of "0V's" and "5V's" will be a (roughly) square wave. This square wave will have the harmonics below 30 Hz and above 330 Hz dissipated, so it will not be perfectly square. If it has a fundamental frequency at the minimum 30 Hz, (so the "0V's" and "5V's" are switching 30 times a second), then there will be a good amount of harmonics and a nice square wave. If it has a fundamental frequency at the max 330 Hz, the signal will be a pure sine wave as there are no higher order harmonics to make it square. However, as there is no noise the receiver will still be able to discriminate the zeros from the ones. In the first case the bit rate will be 60 bps, as the "0V's" and "5V's" are switching 30 times a second. In the second case the bit rate will be a maximum of 660bps, (if the threshold switching voltage of the receiver is exactly 2.5V), and slightly less if the threshold voltage is different.

However this differs from the expected answer of 600 bps for the upper limit. In my explanation it is the upper limit of the channel frequency that matters, not the difference between the upper and lower limit (bandwidth). Can somebody please explain what have I misunderstood?

Also when my logic is applied to the same example but using  FSK modulation (frequency shift keying), I get the same problem.

If a zero is expressed as a 30 Hz carrier frequency, a one is expressed as a 330 Hz carrier frequency, and the modulation signal is 330 Hz, then the max bit rate is 660 bps.

Again, can somebody please clear up my misunderstanding?

Also why use a square wave in the first place? Why cant we just send sine waves and design the receivers to have a switching threshold voltage exactly in the middle between the max and min value of the sin wave? This way the signal would take up much less bandwidth.

Thanks for reading!


texts:
I wrote a verilog code for a 4 by 9 bit register:

module reg_file(input rst,
            input clk,
            input wr_en,
            input rd_en,
            input [1:0]rd0_addr,
            input [1:0]rd1_addr,
            input [1:0]wr_addr,
            input [8:0]wr_data,
            output reg [8:0]rd0_data,
            output reg [8:0]rd1_data);

    reg [8:0]mem[3:0];
    integer i;

    always @(posedge rst or negedge clk)
    begin
        if (rst) begin
            for (i=0; i<4; i=i+1)
                mem[i]=0;
        end
        else if (wr_en) begin
            mem[wr_addr]=wr_data;
        end
        else (rd_en) begin
            assign rd0_data = mem[rd0_addr];
            assign rd1_data = mem[rd1_addr];
        end
    end
endmodule

but using iverilog to check if there are any issues, it says:

26: syntax error
27: Syntax in assignment statement l-value.
30: syntax error

I can't seem to figure out why I'm getting these errors, can anyone help?

I also need to find test vectors to test every possible outcome of the register file, does anyone have any suggestions on the best way to do that?


texts: Something about the derivation of Telegrapher's equation is really bugging me. When deriving the Telgrapher's equations for a transmission line using a model as shown above, why do we only use a capacitor in parallel, and not a series capacitor? Same goes to the inductor in series: why not an inductor in parallel?


texts:
The text says:

"For the values shown, Vin < +10 volts puts the op-amp output at positive saturation, and VOut= Vin,
When Vin exceeds +10 volts the diode closes the feedback loop, clamping the output at 10 volts. "

My inference:
When Vin<+10V the opamp increases its output in positive direction in order to equalize voltages at the two inputs..thus as a result the diode become reversed biased and Vin =Vout ..
its fine till here...
but when Vin>+10V the opamp has to decrease its voltage ..and as the text says that the diode is reversed bias in this case...that means that the opamp outputs some negative voltage (not sure) ..which forwards bias the diode...and the output is clamped to one diode drop below Vopamp..
my problem is ...for Vin>+10V will the opamp output be a negative voltage ....
and if yes then suppose Vopamp = -10.7V..for any Vin value greater than 10V.. then -10.7V will experience a voltage drop ....that voltage drop is -0.7V ..

-10.7-(-0.7) = -10V..
...i.e Vout = -10 V...
but it should be 10V...as per text..in order to equalize the inputs....?

please guide..

//Certainly for Vin>+10V....Vopamp cannot be a positive voltage ..that offcourse will reverse biase the diode again.....which doesnt seems possible..//


texts: High Voltage NMOS layout design in UMC130nm process using Cadence Virtuoso

texts:
I am required to design an NMOS switch in UMC130nm process which is capable of enduring approximately 10V VDS (drain to source) when the gate is 0V. And a current of approximately 50mA when the gate is open (Vgs = 3.3V). Below are the transistor list in umc130 library to which I suppose none would be suitable for my application.

My question is, given the spec above, is there any way to make a custom layout of such transistor (no matter how irregular it would be) without having them placed automatically by Cadence or would it be too far fetched? Below is a graph of a DC sweep on a single N_12_HSL130E nmos transistor.

It seems when Vds = 10, given Vgs = 0, approximately 40mA current passes through the transistor which I think is an indication of a catastrophe if manufactured right?
I also don't have access to the process documentation, there could be hints regarding this issue. So any help is very appreciable at this point.


texts: Arduino reading data from 82 different sources

texts:
I want to make my own electric darts. Whenever a dart will hit the dartboard I need to get the dart location to my Arduino so I can count the score. The problem I am facing is that the dartboard has 82 different places where a dart can land. For example if a dart hits the bullseye it will trigger the switch and I need some component that will send information into the Arduino that the bullseye was hit and I can add 50 to the score. But since there are so many inputs I don't know any component that can do it. My idea was something like reverse multiplexing, but when I started thinking more about it I don't think that is possible.
Do you have any ideas how I can achieve such a thing? And which component I need to read that much data?


texts:
Can I charge two lithium ion batteries connected in series? What is more efficient, series or parallel in terms of charging?

Thank you for answering this question.


texts:
I am building a robot toy. When a sudden surge of sound occurs, I wish to calculate the approx position of the sound source.

I am going to place 3 analog mics on the edge of my round shape PCB, each facing outward.

Is there a chip can handle my requirement? Or I have to do voltage value integration 3 mics with a period of time on a MCU? If so anyone have done the firmware before?


texts: How does a video entry system send audio and video, as well as ring/unlock over 4 wires?

texts:
I’ve been trying to understand how my door entry system works.

Between the monitor/base station and the bell/camera/speaker there’s only 4 wires:

12V DC
GND
Voice (2 way)
Video (1 way)

I opened it up to find a few ICs. One in the base station seemed to be an ASIC specifically for this kind of device, but the datasheet didn’t say anything about ringing/sending unlock command.

Another IC turned out to be a “voice-switched speakerphone”: https://www.profusionplc.com/parts/mc34118g-s28-r

I’m guessing the ‘dial tone’ detector may be something to do with how the base station activates when someone presses the bell button?

I have no idea though how the relay at the remote end can be controlled by the base? There’s a simple two pin header that completes a circuit with the strike, but it’s not clear to me how that gets activated.

So far as I can tell the video line is just composite - though I’ve read some data can be stuffed in a not visible part. I doubt that would be in the base -> remote direction though.


texts: Count number of rotation of a rotating disc

texts:
I have got a large wooden disc for some purpose which rotates in its center axis. But I need to find the number of rotations or simply stop the disc when number of turns reaches a certain point.
So I tried with a reed switch and a magnet. So the magnet attached to the rotating disc and reed switch at a static position where the magnet comes closer while rotating.
So I connect this setup to arduino and modified the debouncing code and added few variables to count the number of times the reed switch changes its state.
But the problem is when it turns slowly the counter variable increments without any issue. But when moves fast the triggering is not at all happening since magnet moves very fast near to the reed switch.
So which is the best way to count the number of turns of the disc..
I thought about a spring switch.. But had some thoughts will there be any better solution


texts: Electrical difference between Push pull and open drain?

texts:
I made a little boo boo in the code of my STM32F4: for 2 years outputs that I thought to be in Open Drain where actually in Push Pull. It got me thinking a bit more about that, and I have come to the conclusion that actually the difference between Open Drain and Push Pull is not that interesting.

From the spec, in open drain the MCU never opens the floodgates on the top part of the totem-pole. Looking at my circuit, I don't think anybody cares about having the output to 3.3V because of the resistor or because of the P-MOS. It would just make a difference in 5V compatibility and even then, the 5V tolerant Vdd would probably survive.

Am I missing something in my analysis, or did a just uncover a great illuminati conspiracy to keep us busy with stupid stuff while they are covering the fact that ET actually did land?


texts: High temperature of components to joining & soldering

texts:
Please help me to know the best components for the process of welding an electronic circuit to operate it in a very high temperature environment up to more than 600 degrees Celsius?
Note: I do not know if I can use the Ultrasonic welding in my application, and add on it another component to soldering with tolerate the temperature for example 500 ? Is this possible?


texts: PCB simulation of high speed ADC daughter card connected via FMC connector

texts:
A design using high speed ADC is to be carried out involving an FPGA as the master device. To simplify the prototype phase, a daughter board with the ADC shall be designed and connected to the FPGA development board via a HPC connector. This connector is design to be used with high speed links.

I want to have a starting point for investigation on how to complete the PCB design and simulation. I understand the basic theory behind high speed design which is impedance matching and PCB track length constraining. However, as far as I am aware, it also important to have a power supply network that is resistant to noise and is stable for the ADC. The question is, how to go about doing this in Zuken Cadstar or Altium Designer. Certainly, I will need information about the FPGA development board PCB to complete this type of simulation as well.

Any application note or book that can provide practical example of PCB design for a similar problem will go a great length and answering my questions.


texts: How is it possible that if I combine 100 Ohm resistors in different ways, I get _LESS_ resistance than original?

texts:
This is blowing my mind.

Let's say I've a bunch of 100 Ohm resistors, all identical.

How is it possible that if I combine them in parallel, I can get something that has less resistance?

Check this out:

   ----100OHM---
---|           |---
   ----100OHM---

This is effectively a 50 Ohm resistor!

It was already hard for current to get through one resistor (at 100Ohms), but I combined two resistors together, and now it became easier for current to go through!

If I take ten 100 Ohm resistors in parallel:

Check this out:

   ----100OHM---
   ----100OHM---
   ----100OHM---
   ----100OHM---
   ----100OHM---
---|---100OHM--|---
   ----100OHM---
   ----100OHM---
   ----100OHM---
   ----100OHM---

This is now 5 Ohms!!!!!!!!!!!!!!!!!!!!!!! Electricity is no longer having almost any resistance, yet each of resistors is 100 Ohms. If I added even more 100 Ohm resistors, resistance would go close to 0, and current would just flow through with no resistance.

How is that even possible? If I think logically, then it could only have gotten HARDER for current to go through two resistors, but somehow it became easier.

Real life analogy:

Let's say there's a 500 pound bouncer at club entrance. It's hard to get past him right? He's strong and will resist you getting past him. Now if the club adds another bouncer at 500 pounds, it suddenly becomes EASIER to get past both of them??

There's no way it's possible!! Can anyone explain this in simple terms?


texts: How to keep stiching vias away from text?

texts:
To keep automatically stiched vias away ( >=200µm) from tracks, pads, texts on top solder mask and polygon cutout regions on multi-layer, I tried to use a custom query in a seperat clearance rule:

The rule works as desired, expected from stiched vias avoiding texts on top Solder. I tried "Kind='Text'" instead of "isText" as well, but it did not work either:

Has someone an idea what is wrong with my query and how it should be written correctly?


texts: Control a 110v AC motor with a 5v digitally controlled potentiometer

texts: I have a manual variable resistor(turn the knob) connected between 110v and an ac motor that pumps air to make bubbles in my portable hot tub. I have had it for about a year and it works fine to adjust the speed of the motor to vary the amount of bubbles. I however am wanting to have this controlled digitally so that I can use an arduino to vary it based upon other sensor values. Is there a simple 5v digitally controlled device that allows for 110v AC control. I know this is easy with a 5v relay, but I am confused if there is a simple a solution to what I am looking to do.


texts:
I would like to use 50mV FSD signal to sense DC current at a distance of  ~70 feet with a twisted pair cable and then perform signal condition there.

Does anyone have any experience with this?

" Originally asked"
Is it advicible to take lower side shunt 50mV FSD signal at a distance of about 70feet with STP cable , and then make signal conditioning there at remote location. I need to enquire does experienced members do this way?. BTW I am trying to sense DC current.


texts: Inverting regulators and sinking current

texts:
I have a circuit to drive a simple resistive load, and it works quite well. On the high side is 2.5V from a regulator, and the low side is 0V (taken as reference to a battery's negative terminal which supplies the regulator).

I have realized that it would be desirable in my application to have the high side of the load be 0V, and the low side to be -2.5V instead. To do this, I have considered implementing the TPS63700 (link below).

What I can't get my head around, is the fact that the regulator would need to sink current rather than source it in this situation (about 60mA in my case). I would imagine it can, since i can't understand what situation wouldn't require it unless there was an even lower voltage in the circuit to source to. I've gone through the datasheet but the definition it uses is 'output current', and i don't know if that means current at the output or current that the device puts out.

Could someone explain where my thinking is wrong, and give a brief explanation of why the part (or other inverting regulators) would or wouldn't work for this application? Also, how does the current flow if the input side of regulator is connected to a battery (terminals 0V and ~4V), and the output side (-2.5V) is connected to the battery's neg terminal (0V) by a series resistor?

TPS63700 datasheet: http://www.ti.com/lit/ds/symlink/tps63700.pdf

Thanks.


texts: Is multi channel transceiver capable of receiving simultaneously from multiple transmitters?

texts:
We are in the process of designing a system that requires transmission of data from a sensor nodes to receiver at processing node.Later on,the receiver node can send(transmit) certain commands/instructions to the sensor node.There will be multiple(say up to 60) sensor nodes at a time,simultaneously transmitting data to the receiver.Each transmitter will be assigned a specific channel and the receiver will identify the source of the data.The receiver node could be moving at some speed and signals could be Dopplerised. We need to achieve a range of about 15 kms,line of sight in 100% humid atmosphere.Antenna for transmitter will be a simple wire and Omni-directional. There will not be any gain at the antennae antenna.

·         Frequency Range : 160 Mhz to 175 Mhz
·         No. of channels:      60 for the receiver
·         No of channels for Tx : One
·         Data rate:  minimum-225 kbps

Is there any RF multi channel transceiver which is capable of receiving simultaneously from upto 60 transmitters?


texts:
I have a question related to the sub-threshold operation of MOSFETS.

Let's say I have the following setup:

How can I calculate the sub-threshold current ( Id when Vgs < Vgs(th) ) at
Vgs = 0.5V using the data from the datasheet and data from the circuit?

Also what value will Rds have and what will be the value of Vout (Vds) at Vgs=0.5V?

I am very new to the domain of electronics so if I understand it correctly when Vgs < Vgs(th) the MOSFET will not be turned off completely but instead the  "resistance" of the MOSFET (Rds) will be very high (in the range of MOhms) and there will be a very low drain leakage current (in the range of uAmps). I would like to know if there is a way to get a more precise calculation of this  values (Id, Rds, Vds when Vgs < Vgs(th)) using only the available data from the datasheet and the circuit.


texts:
i am an absolute novice when it comes to electronics. i am looking for an (ideally passive) circuit of some sort, that converts voltages from 0V - 10V to -5V to 5V.

i'd be gracious for any hint or places to read up on this. the conversion is for the purpose of a modular synthesizer and therefore needs to be rather precise (e.g. former 4V needs to be exactly -1V and so on).


texts: Arduino issues on reading inputs from some buttons

texts:
I'm building a sort of joystick with atmega328p:

For the moment, I have only written the code to visualize on the OLED display if we press a button or move the joystick. Let's focus on the four buttons at left, whose result is represented by the statements UP, DOWN, R, L. If we press a button, we'll se 1 on the display, else we'll see 0.
All the buttons are correctly connected to atmega328 pins, without "false electrical contacts", but if I press them,

UP works correctly (it is always 0 and if I press it, it becomes 1)
R works correctly
L does not work: it keeps always 0
DOWN partially works: if I press it, it stays 0 forever.ù

Since I have checked the connections many times, I think that maybe I have written a code that can cause some errors or missing input values. So, how do you re-write the code to find a possible solution for making all buttons work?
This is the part of my code that regards the buttons (and the joystick, which you may ignore):
void loop() {

  // **JOYSTICK**
  int x = analogRead(JOYSTICK_X);
  int y = analogRead(JOYSTICK_Y);
  int button = !digitalRead(JOYSTICK_BUTTON);
  display.clearDisplay();
  display.setCursor(0,0);
  display.println("X: " + String(x));
  display.setCursor(0,10);
  display.println("Y: " + String(y));
  display.setCursor(0,20);
  display.println("P: " + String(button));

  //**BUTTONS**
  display.setCursor(60,0); //Set the cursor position for the fist line to
  visualize
  display.println("UP: " + String(!digitalRead(UP_BUTTON)));
  display.setCursor(60,8); //Second line
  display.println("DOWN: " + String(!digitalRead(DOWN_BUTTON)));
  display.setCursor(60,16); //Third line
  display.println("R: " + String(!digitalRead(RIGHT_BUTTON)));
  display.setCursor(60,24); //Fourth line
  display.println("L: " + String(!digitalRead(LEFT_BUTTON)));
  display.display();
}


texts: Why are "ice cube" PCB mount power relays pinned out so that the COM pin is between the coil pins?

texts:
If you have used "ice cube" type PCB mount power relays before, you're probably familiar with the de facto standard pinout for them:

Why is this such a standard pinout though?  It's clearly not an optimal pinout -- positioning the common terminal between the coil terminals forces you to put an isolation slot in the PCB in order to obtain reasonable creepage distances, and severely constrains the clearance distance available as well.  It's also not something unique to cheap Cheese-shop-specials either: the Omron G5LE series uses this pinout, and so do equivalent relays from TE/P&B (ORWH) and Panasonic (JS1).  You need to go to much costlier parts such as a Tyco PCH or RZ or Panasonic JW1 in order to get something that puts the common pin on the same side of the relay as the other contact pins.

Is there some sort of internal construction detailing that makes this type of relay unsuitable for mains isolation to begin with? Or why can't the relay manufacturers bring the common terminal out on the "correct" side of the relay to allow an isolation barrier to be established?


texts: Strange circuit design for driving a fan with PWM

texts:
I've recently attempted a repair on a cooling fan circuit in a hard drive enclosure that has me somewhat baffled. The fan is an AD08012HX207000 with a connection for two wires. The circuit that drives the fan supplies 12V to the positive pin, and the negative pin is driven by the circuit below. The circuit appears to take the 3.3V PWM signal from the MCU, reduces it to ~1.6V to drive the base of a low voltage, high current BJT transistor. The transistor provides a path to ground when the base is driven high, and the fan can spin.
I'm not really sure what the 47uF capacitor is for. Smoothing out the PWM transition when the fan changes speed? When I probe the capacitor I see a square wave at 12V, and my sense is that the capacitor is charging to 12V, at which point the fan is off because the voltage on both sides is the same, and then discharging, allowing the fan to spin again, but I have no idea why it's connected via a 4.7k resistor to MCU power.
Here's a shot of my oscilloscope probing the pin of the capacitor that is connector to the fan negative:

If I remove the capacitor from the circuit, and connect the fan negative directly to the emitter of the transistor, I see this:

I guess my questions in order of importance are:

Why do it this way? Why not just use a mosfet to either drive the 12V positive or the path to ground? Does this save money somehow?

Why the voltage divider on the PWM signal? I checked the datasheet for this transistor and 3.3V seems fine.

What function does the capacitor serve?

[edit] just to clarify a bit, what I'm trying to "repair" is the fact that the fan spins very slowly when connected, and only on the highest setting. I've actually tested this fan with a simple PWM circuit coming from a 555 timer, and it doesn't really seem to like being drive by PWM very much. It basically maintains a constant speed until ~50% duty cycle and then turns off, which makes me think that it has some sort of internal regulation that is interfering. The manufacturer sent me this fan as a replacement, and my growing suspicion is that they sent me the wrong one and the circuit is actually working fine. I've lost the original, so I can't use it for comparison. All of that aside, I want to understand how this circuit works for my own edification.

simulate this circuit – Schematic created using CircuitLab
Turns out the schematic above was incorrect. I've updated it to indicate that the capacitor is connected across the collector/emitter in case someone comes across this in the future.


texts: Can I power 4000 series CMOS ICs from two AA batteries?

texts: The specs (for TI chips) say anywhere from 3 - 18V, and I've measured two alkaline AA batteries at just over 3 volts. I'm wondering if that dips below 3V when the batteries get old, whether or not that would cause problems. Or, if there are other considerations I'm not aware of.


texts:
I have simple co2 meter using atmega328p as uC (Arduino mini Pro board actually). Microcontroller is sending measurements over FT232RL to a PC host (one way communication from AVR to PC), but this part of schematics is irrelevant as you'll see later.
All works quite as expected when I left RX pin floating on AVR side (I'm not reading anything from UART): I can get representative data on the PC side. But when I connect AVR RX – FT232RL TX, I have no transmission over UART. Using logic analyzer I see there is even no start condition on AVR TX pin.
Using scope I figure out that after FT232RL is powered up there is some delay and then both DTR and TX pin of FT232RL show following:

CH1 – 5V power rail powering both AVR/FTDI, CH2 – FT232RL DTR/TX pin (both have basically the same signal)
AVR UART transmitter stops sending any data (there is no start condition on AVR TX pin) after first transition to HIGH at CH2.
At this point I disconnect FT232RL from AVR entirely and figure out that any signal transition from LOW to HIGH on AVR RX pin at any moment stops UART transmitter.
Next using logic analyzer and some "pin toggling debugging" I have confirm following:

UDRIE flag is enabled, so UDR vector should be called (I'm using interrupt based UART);
global interrupt flag is enabled and timer interrupts works as expected
invocation of UDRE interrupt handler stoped right after aforementioned LOW->HIGH transition on AVR RX pin;
USART_RX interrupt handler is never called under any circumstances.

Also I've found configuring PDO as GPIO instead of UART TX solves the problem, which is quite obvious at this point.
What can cause AVR UART transmitter to stop working in such circumstances and what tests can I perform to locate problem further?


texts: Termination resistors in Ethernet in Kilo-Ohms instead of Ohms?

texts:
When working with Ethernet, whether copper or optical fiber, why are the termination resistors always in a few ohms and never in kilo-ohms?

Example: 49.9R on transmit & receive pair of PHY in copper Ethernet, 130R & 82R divider on transmit & receive pair of PHY in fiber Ethernet.

Reference: Page 62 and 63 of this PHY datasheet: http://www.ti.com/lit/ds/symlink/dp83620.pdf

The only reason I can think of is the driving/sourcing current, which would be less in case of high valued resistors causing issues in high speed communication.

Any thoughts?


texts:
How is a majority voter for complex data implemented?
If there is only one integer value which should be compared you can use a discrete circuit but how does it work for multiple datasets and floating values which could be slightly different because of rounding effects.

Is the voter itself a microcontroller and a single point of failure ?
How are the voting results send for example on a can bus?


texts: Damaged Power Supply from USB 3.5'' External Drive Enclosure

texts:
I have a 3.5'' External Hard Drive Enclosure. Recently it stopped working. When I connected the power supply and turned it on I could hear the disk spinning but after about 1-2 seconds the disk stops spinning (the motor turns off) and then it starts spinning again. This happens until I disconnect the power supply manually.

My thinking is that the start up of the disk (specifically the motor) draws too many amps and the voltage decreases.

So I bought a new power supply (12V/2A) and it didn't worked. Same issue again. I measured the voltage of the supply and it was ~10V so I thought the supply was faulty and returned it. Now about 2 months later I bought another one because I needed the drive. Turns out it worked and was happy. But after letting the drive run for about 4 hours the same issue happened again. Somehow it seems like my enclosure damages the power supply (again 10V max).

Is there anything I can do to find out what the issue is or is the enclosure simply broken? Might it help if I buy a 3A power supply although the enclosure says 12V/2A is recommended. Also tried another HDD so it's definitely the enclosure.


texts: Why is 5.1V the standard Zener voltage and not 5V?

texts:
Looking on Digikey there are ~1300 results for 5.1V Zener diodes compared to 6 for 5V ones.

Is there any physics-related reason for this or is it something else?


texts: Multiple power supplies in series: Negative voltage on one of them possible?

texts:
It is common practice to connect multiple power supplies in series to obtain a higher voltage; examples: 1, 2, 3, 4. Many power supplies are designed to handle this application well. However, users are cautioned to check the manual of a power supply if it is really recommended to use it in series with another one.

One issue that might arise is called polarity reversal, i.e. a negative voltage being forced on the output of the "weakest" supply in the chain of series-connected devices. How is this possible?

Note: Same story for batteries. One should make sure that the same type of battery is used together with another, and that multiple series-connected batteries are in equally good (or mediocre) shape.


texts: I have one of these. It's connected to a raspberry pi. It's being mounted against a metal frame, but when it's mounted, i get interference on the touchscreen (the mouse jumps all over the place). How can I insulate it better. I used 1 layer of duct tape and one layer of electrical tape...but it's still having issues. Any advice?


texts:
Just a quick question regarding reverse polarity diodes with respect to linear voltage regulators. I saw some professional designs putting diodes on the output side of the regulator which confuses me because your regulator could still be fried in a reverse polarity hookup scenario and you incur a voltage drop as well. It makes more sense to me to put it on the input. Could someone tell me why you would do that and what I am missing? See the picture below as an example.

Thank you


texts: LTSpice: How to use .meas command to find the fundamental frequency of non-sinusoidal signal?

texts:
I want to find fundamental frequency of a periodic signal (non-sinusoidal) in certain time window using the .meas command in LTSpice.

I was using the following code to calculate frequency (in kHz).

.meas tran T1 find time when V(OUT)=0 rise 1000
 .meas tran T2 find time when V(OUT)=0 rise 1100
 .meas tran  Frequency param 100/(1000*(T2-T1))

This works fine for certain cases, but when I do the parametric sweep, it gives inaccurate readings because of two issues:

Here, I assume at 1000th cycle, signal reaches its measurement window (say from time=4ms) but sometimes it doesn't. Therefor, I want to specify the absolute time for the measurement. from 4ms in this case, I have added a sample voltage waveform as below (with parametric sweep)

The zoomed waveform from 4ms is

My questions is

Is it possible to specify the starting time for the above code so that it will count cycles from the specified time? ( I tried to use trig-trag and from-to commands but failed)


texts: Single-Ended Input operation of Differential ADC

texts:
I am looking at purchasing a 14-bit ADC chip (http://www.farnell.com/datasheets/1882573.pdf) for a battery monitoring project that I am working on, and am using a differential amplifier measuring voltage across a current shunt and then feeding that into an ADC.

Would this potentially work if I just used the output of the diff amp (1-5V) and  into the +in pin and ground into the -in pin? If not, why not?


texts: What do the arrows mean in this schematic?

texts: What do the arrows mean on this circuit diagram? It is for this component: https://lcsc.com/product-detail/Audio-Video-Connectors_Korean-Hroparts-Elec-PJ-399E-6A_C128993.html


texts: Trying to build custom electronics connection to a motorized zoom/focus lens

texts:
I'm a beginner when it comes to electronics, I had some success with pretty simple arduino based projects like blue tooth controlled stepper motor assemblies using well documented drivers and components from places like adafruit.
What I'd like to do is to connect custom electronics to a motorized device like a zoom/focus lens found in many digital cameras. I took the plunge and purchased a Sony DSC-H90 replacement lens which is intended for people to plug in to a Sony camera motherboard if their lens assembly is broken.

However, I'm wondering if it is possible to connect to the flexible ribbon coming off of the camera and send and receive along the individual pins.
I was able to download the service manual for this lens assembly and it seems to provide some idea as to what each pin is supposed to do - I'm guessing with some trial and error one could design appropriate stepper motor drivers for example to run the inner stepper motors that control zoom and focus - maybe even to listen to the sensors that indicate home position for the motors.
Given my inexperience this is a big goal for me but I know I'd learn a lot along the way. I'm embarrassed to say however that I'm stuck on step 1 - I can't figure out what kind of FPC ribbon I'm dealing with.

The width of the conductor strands of this ribbon varies, some are thick, some are thin. I count 35 pins, but it seems that the pitch of this connector is not uniform. How do you connect to a ribbon like this? Is this something that Sony does on purpose to make it more difficult for people like me to connect directly to the electronics assembly?
I may be missing something obvious as to why what I'm trying to do is not possible, I'd love to get any feedback that more experienced may be willing to share. Perhaps some replacement motorized lenses are going to be an easier project than this one given the strange ribbon at then end!
Thanks all in advance


texts:
I was trying out some different designs of constant current loads a.k.a dummy loads and stumbled upon this one on google images search. I do have a question or two to it's operation since on breadboard it's not working at all. I have replaced the parts in the diagram below with what I have in my parts' storage.

My questions:

What is the use of the transistor Q1? I understand that it's an emitter follower but wouldn't I achieve the same using a voltage follower from a spare op-amp?
Are R4,R8 and C1 crucial for the readout or can I just omit them out
Could I use this for a DUT using AC?
I built the circuit as is on breadboard but the current through R15 is not going over 100mA! Even when the reference voltage set at U1 is 5V which should give me anything close to 5A. The MOS-FET I'm using is a logic level FET according to this IRL3705N datasheet. I can confirm that the FET is original since it's from a reputable source and the op-amps are working fine in other constellations on the same breadboard. Maybe I'm overseeing something or the circuit is just baloney.

Thanks for your comments in advance


texts:
These 3 diagrams represent 3 test cases.

Dia 1:

When I perform an analogRead of analog port 0, then I get a high value obviously. According to the manual, the analogRead method obtains the resistance. I expected it would say that it returns the voltage. Anyway, in this case both are directly proportional.

Dia 2:

With a resistor + pull-down resistor, the reading of the analog port 0 decreased.

Dia 3:

However, I would have expected that dia3 would also result in a decreased value.

My reasoning was: The supplied voltage of 5V is constant. So, it must be divided between the resistor and analog port 0. A bigger resistor should result in a higher voltage for the resistor, and a lower one for the analog input. --> But that seems to be incorrect.

Second attempt: The analog port reads resistance and not voltage. Maybe that's important. R = V / I.  Apparently the resistance remains the same. So, applying this formula: if resistance remains constant and voltage decreases, then it could be caused by an increasing current. But it doesn't make sense that the current would increase by adding a resistor.

PS: if I add the analog pin to ground, then I get a low reading.

Where exactly is my reasoning flawed ?

EDIT:

As many people have pointed out. I have indeed wrongfully interpreted the following phrase in this tutorial. Thank you for pointing that out to me.

  in the main loop of your code, you need to establish a variable to store the resistance value.