texts:
I have very old desktop style 3 axis cnc machine. There were 2 dc motors for X-Y axis and a unipolar stepper for Z axis. I replaced the old DC motors with unipolar steppers. I personally made the drivers for X-Y axis , since unipolar motor driver is easy to make using power transistors. Z axis stepper already had its own driver and I continued to use it as it is. I use Arduino Mega to control the motors, lcd, buttons, encoders, etc... The library that I use to drive steppers is Accelstepper library. Everything was very fine and the whole cnc worked very accurately.

Suddenly, both X and Y axis steppers started losing steps first, and then they are totaly failed. Now, they only vibrate and shafts don't turn, at all.

I checked/tested the drivers with an oscilloscope and an am-meter and found that they work as expected. I had more steppers with the same brand/model. I replaced the steppers with new ones for testing the drivers and other staff. Everything is OK! Finally, when I try to turn the shafts by hand, I feel the detent of the new steppers, but the shafts of the failed ones just turn easily like a dc motor without feeling of detent. This situation suggested me that somehow they lost magnetism.

But how? What may be the reason for that? I need to know the reason and solve the issue before I start using the machine with new steppers, since probably they will fail too, because of the same reason...
Thanks.


texts:
What is the difference between a TSOT-23-6 and a SOT-23-6?

I know one is thinner. But in what dimension? I have looked in my PCB editor and they both have the same footprint.

Any clarity appreciated!


texts: Power spliter for Raspberry pi and servo motor

texts:
I have a raspberry pi. I want to control a 12 volt motor (low torque). I believe the motor only has two connectors, and when it is powered it goes. The motor goes off of 12 volts where as the Raspberry Pi is only 5 volts.
I also want to be able to power the motor and the raspberry pi in one unit. I don't know what this yellow box is. For example, do I split the 12 volts DC coming in, and send 12 volts to the motor and then do some resisters to lower the 12 volts to 5 volts to power the raspberry pi? What about the ground for the motor? Can it be connected back to the yellow box too? (what ever the yellow box is)
For more clarification:


texts: What happens to a computer as it is cooled towards absolute zero?

texts:
What happens to the behavior of a conventional circuit using conventional components as it is cooled towards absolute zero?

To make this question more relatable: What would happen as we cool a modern CPU and its power circuits?

In general resistance decreases with temperature, so I assume that initially we would see the device's power consumption drop for the same cyclic frequency.  (Or would the clock mechanism change its frequency as it is cooled also?  If so, let us assume for the rest of the question that the clock is external and not altered.)

Do transistors and other semiconductors begin to fail below certain temperatures?  If so, by what mechanism?

At some very low temperature I assume that various conductors would begin to superconduct.  How does this alter the behavior of the power supply and computational circuits?


texts: How to determine type of through-hole resistor?

texts:
Everyone should be familiar with standard carbon through-hole resistors, but there are of course other types like wirewound, metal film, metal oxide, etc.

The trouble is, how do you identify the type of resistor if you just have a bunch sitting in a parts bin?

I inherited a grab-bag of parts and haven't been able to identify some components. Here is a sample of the resistor-like parts:

The topmost part is a standard 1/4W carbon resistor. Below that, I believe a metal film or metal oxide. Below that, I am simply not sure. (I think the last part may even be an inductor.)

Is there a standard color coding for these parts to identify the component and its composition?


texts: Powering audio codec below recommended spec

texts:
I'm working on an audio project where I intend to use the PCM3060 audio codec (datasheet here). The datasheet says that the chip takes two power inputs :

Vcc (Analog supply voltage) @ nominal 5V (recommended operating conditions  4.5V to 5.5V)
Vdd (Digital supply voltage) @ nominal 3.3V

Providing the 5V will be a pain for me so my question is : Being ok with a reduced analog output voltage range, can I get away with providing only 3.3V to Vcc ?

My naive expectation is that, being for the analog side of the chip Vcc will mostly define the max range of the op-amps that would be involved in the process of generating the signal, and thus reducing Vcc would mostly only reduce the effective ouptut voltage range (and maybe to a lesser extent the dynamics of the output) but nothing would stop working and as I expect to not use the whole rated output range that would be perfectly ok for me.

That assumption is partly based on the observation that  most of the output caracteristics in the datasheet are specified as proportions of Vcc but as I have very little experience in electronics, let alone audio cicuitry, I don't know if typically DACs and ADCs would be that tolerant in regard to power supplies.

Note : 3.3V is outside the recommended operating conditions which is why I'm asking this question. 3.3V is well within the absolute max rating for Vcc so I'm at least sure it  won't damage the chip.


texts:
I wonder if microcontrollers normally have cache or not.

What is the common case?

If not, what could be the benefit behind this?


texts: Issue having 4-20 mA interface with ADS1115

texts:
I need to make a 4x 4-20mA measuring circuit with ads1115 (VDD = 5V) 4 channel 16bit ADC

I set ads1115 PGA to 4.096 gain and set circuit as below.
once I set this 32000 ADC levels--> 4.096V--> 0.128mV

I am targetting to archive 0.128mV resolution.

R1 50ohm and R2 200ohm voltage divider is for regulating 5v to 4v.
also, I set R2 200 ohm to get 4V at 20mA current.

R3 3.3k Ohm is there for reducing current flow into ADC1115 chip.

this is for a 3 wire sensor (24V DC supply, 4-20mA output and gnd)

** is this circuit configuration a reliable method to measure 4-20mA current using an MCU? **


texts: Looking for an AC current sensor for less than 10A measurements

texts:
We are building a voltage and current acquisition system using NI hardware. While voltage measurements are done directly using the NI IO Module, current measurements need a sensor. We have a 100A (ydhc 013-000) sensor with a linearity between 10% and 120% of rated current (100A). But since we are aiming to install the system in households, low current consumption should be taken into consideration and this sensor don't seem to be convenient.

Can you please give me some suggestions for more convenient ones?


texts: What design differences make ram faster than ssd for read/write

texts: I understand that RAM is connected directly to the CPU via a high bandwidth bus, and SSD is a peripheral, but my assumption is that there are also electrical design differences (e.g. memory cell design and layout) that make RAM faster than SSD for reads/writes. If that is true, and with bus bandwidth & latency differences aside, what are those design differences, and how do they affect speed?


texts: What is the meaning of a circle next to a component pin?

texts:
I'm analyzing the schematics of Lenovo_G530_N500_-_COMPAL_LA-4212P_JIWA3_JIWA4_-_REV_1.0Sec. I have across scenarios where there is a circle next to a component pin. What does this circle symbolize? I have attached the screen shot for my question.

I have tried looking for a proper answer on the internet, but no satisfactory answer found.


texts: What is meant by output Leakage Current?

texts:
Is output Leakage Current= Output Current - Input Current?

I encountered the term in a datasheet of the L9938 driver.


texts: A basic question on Current Flow, Voltage, and Power consumption

texts:
Background:

Assume that I have Bulb that consumes 10 watts of electrical energy (power).
The operating values for full brightness are: 5 volts, and 2 amps.
Since Power(p) = Voltage(V) x Current(I) = 5 x 2 = 10 watts

Question:

For a bulb to glow all it cares for is the flow of electrons at the required rate (amps) --> call it axiom.
In the above circuit, assume that I keep the current constant at 2 amps by reducing both the voltage and resistance.

So, by my axiom, I expect the same brightness of the bulb, but the bulb glows at lower brightness.
I know the lower brightness is because of lower power since voltage is reduced, but by my axiom: "For a bulb to glow all it cares for is the flow of electrons at the required rate (amps)",  shouldn't the bulb remain bright?

Or, is my axiom wrong?

Edit: As many of you have mentined, I accept that usage of the word axiom is wrong in this context.
I would rather use the word assumption, however, since many answers to this questions refers to the word axiom, I do not want to change it to assumption, as this would confuse future readers. Thanks.


texts: In DC, for example at 12V, will a longer power wire (lets say 10 meters vs 10 centimeters) cause a high current consumption?


texts: Clarification of solid ground plane (antennas)

texts:
I'd like some clarification on identifying if a ground plane is solid or not. Is the definition for a solid ground plane simply a ground plane with no gaps?

For example, would the antenna below be considered to not have a solid ground plane?


texts: Practical formula/method to predict the necessity of termination resistor

texts:
I am not into high frequency much and just know about ringing caused by reflections due to impedance mismatching in transmission lines.
So I recently saw some non-engineer researchers in a lab that they were measuring 3MHz signal with 1 meter 50 OhM coax cable and the cable was directly coupled to the scope input.
In such electronic instrumentation I am wondering when would a 50 Ohm termination required. Is there a practical way to roughly tell whether 50 Ohm termination is necessary? (Assuming source impedance is negligible, 1 meter 50 Ohm coax cable, and a 3MHz signal, scope input impedance is 100Meg)


texts: Limit the coil's voltage of the stepper motor

texts:
When the step motors are used with a current-controlled driver, also known as a chopper drive. The driver will increase output voltage when the motor runs much faster, because the faster the motor runs, the larger reactance the motor's coil has, the larger voltage is required to maintain a constant current.

I think it will destroy the motor when the motor runs extremely fast in this fashion, its coil's current keeps constant but the voltage is increased without limit, the resulting power dissipation will be very large.

Should I limit the coil's voltage according to the "rated voltage" in the motor's datasheet?  So when I use current-controlled driver with its current set to the motor's max phase current, the motor can't run much faster when the motor's coil voltage reaches the rated voltage.

Am I correct?


texts:
I need a lo-fi way of mounting a PCB (Tessel plus RFID card) under a table.

The easiest method by far would be velcro but I'm worried about static discharge frying my circuitry. Should I be?


texts: when there are 2 opamps in a circuit working simultaneously how do we sketch transfer characteristics?

texts: could you please help me finding transfer characteristic (v2/v1) of this circuit.


texts: How to reverse direction of stepper motor with flip-flop

texts:
I am trying to reverse the direction of a stepper motor. The stepper motor drives a scanner head and when it gets to the end, I want it to reverse direction. I have some photo interrupters that trigger when the signal is interrupted but how do I make it switch direction when they are triggered? Do I use a flip-flop and if so what type. I am driving the stepper motor with a H-bridge that is controlled from an Arduino but I would prefer to switch the direction with hardware instead of programming it to reverse when it gets to the end. So what type of flip-flop do I use had how do I wire it? I have a bipolar 4 wire stepper motor.

Code to make the stepper motor move forward:

#include <Stepper.h>
#define STEPS 96
#define D0 3
#define D1 4
#define D2 5
#define D3 6
const int enab1 = 2;
const int enab2 = 7;

Stepper stepper(STEPS, D0, D1, D2, D3);

void setup() {
  digitalWrite(enab1, HIGH);
  digitalWrite(enab2, HIGH);
  stepper.setSpeed(600);
  stepper.step(7596);
  digitalWrite(enab1, LOW);
  digitalWrite(enab2, LOW);
}
void loop() {

}

Thanks.


texts: ESP32 High Power Consumption in Deep Sleep Mode

texts:
I'm running a Python program on an ESP32 (MicroPython firmware) that fetches online data to save it locally every 5 hours, and then goes into deep sleep mode. The board is powered with a 3.7V lipo battery. The whole HTTP request takes at most 10s to get a response.
I'm tracking the battery voltage as well, and I get a 0.1V daily voltage drop, going from a 3.8V output when fully charged to 3.3V when battery is running low (under that level, the board doesn't seem to be able to send HTTP requests anymore).
I also connected a button to one of the GPIOs that I use to wake up the board (via the wake_on_ext0 method).
I don't understand why the voltage output drops that fast. I thought that in deep sleep mode, an ESP32 drew 10uA to 150uA of current.
Am I missing something? Could it be that the pull-up resistance that I programmatically set for the wake-up button is drawing current even in deep sleep?
Any suggestion to keep power consumption low would be appreciated.


texts:
I use the toner transfer method to create PCBs. By removing the heat fuser from a laser printer and printing on gloss paper gives me wonderful results.
The heat fuser and thermistor sensor is still connected to the printer's board as when the printer turns on, it seems to test the thermistor by tuning on the heating lamp.
I guess they get the temperature, then turn on the heater and monitor the change in temperature. Unplugging the heater before start up, causes an error. Obviously unplugging the thermistor does the same.
I would like to remove the heat fuser completely from the printer. At first I thought that putting in a resistor in place of the thermistor would be enough to fool the system. At room temp the thermistor reads 200 kΩ, and at 180°C it goes to 50 kΩ. But using a 50 kΩ in place of the thermistor resulted in an error.
To test,
I soldered in a pot and resistor, so that I had 50k to 200k swing. When the lamp turns on, I tried to bring the resistance down (turning the pot manually) from 200 to 50k but no luck.
I can only think that the software monitoring the temperature is super advanced. Keep in mind that sometimes the printer is turned on while the heater is still very hot and still tests the thermistor successfully.
Any idea why this approach would not work?


texts: Speed of various prototype systems for digital electronics

texts:
I would like some advice on what digital signal frequencies I'd be able to work with for hobby projects.

I asked this question recently about interfacing to a memory chip from an FPGA as a hobby project. The answers are all very good but have made me realise that I have a little more to learn before attempting some a project. I feel I could probably build the design I want in verilog but I have a lot to learn about physical design first.

I realise this question is rather vague, but all I'm looking for is an order of magnitude answer to get some idea what projects might be viable for me.

I can buy an FPGA on a breakout board so that I can connect plug in wires to a breadboard for experimenting. I imagine that for flashing an LED there would be no issues with this. I imagine that I could likely get I2C working (as I've done similar things with microcontrollers). I could likely get an interface to a static memory chip working at a MHz or so maybe? I imagine that interfacing to a memory chip at 133 MHz would have zero chance of working. Assuming I take some care with connections, wiring etc, what is the highest frequency that it's even worth my time trying to make work for a hobby project on such a setup?

I presume that if I make a home made PCB I could work with somewhat higher frequencies. What sort of frequencies would I likely have to go beyond before I'd really have to know what I'm doing to design high frequency boards?

If I got a professionally made board I imagine I could likely get it to work a little faster still, but beyond that I'd need to educate myself a lot more to know how to make it work reliably with high speed signals.

Again, I'm not looking for exact figures, just order of magnitude figures to prevent me from wasting my time on something that's never going to work.


texts: How to measure biosignals with 1800's technology?

texts:
Say, you are in a 1800's(all of 1800s) setting where you only have inductors capacitors and resistors and you are trying to detect a signal coming from a persons body. How would you design them?

If you already couldn't tell this is a discussion that I am having with peers in my bio instrumentation class. I am just baffled on what to do. How the heck would you mimic an opamp only using 1800s technologies (e.g capacitors resistors and inductors) Picture for the description is shown below. How in the world would you "amplify" signals from the heart without an opamp?


texts: What is the theoretical maximum data transfer rate of a pair of wires in a phone cable?

texts:
Yesterday folks from my ISP came to install a 16 Mbps "Fiber to the Home" connection, but I noticed that the connection still comes in through the same two wires on our phone jack.

Could that same connection handle a 25 Mbps connection? What about 100 Mbps? Is there a no theoretical maximum, but it becomes more and more unreliable?


texts:
I was looking at an instructable and they suggested using "reflow soldering" for a certain section. "Reflow" wasn't a concept i was familiar with, so I did some Googling...

I got a basic description of the process, but I still can't figure out why you would want to do this over "traditional" soldering (not sure of the proper term). What are the pros/cons of this technique, and when would I favor it over other techniques?


texts: How to implement AES Encrypting for ESP8266 implemented on Hardware?

texts:
I need to write a basic encryption program for ESP8266. I did read the datasheet (https://www.espressif.com/sites/default/files/documentation/0a-esp8266ex_datasheet_en.pdf), and them says that existis the methods of encrypt: WEP/TKIP/AES. My main question is: The AES method, is implemented on software or hardware? This module is very simple, (36KB RAM, 90MHz CPU clock), so the algorithm is heavy to process. If AES is implemented in hardware, I think this task gets simpler, but I don't know how to use this. I did read at web, and the examples uses a #include "AES.h" lib, I don't know if this is implemented on hardware or software. The site of ESP8266 don't reply this question. So, I wants know about this and how, or where I found help, to implement this.

Ps.: I don't want use Arduino.

Also, I've already use this, https://github.com/CHERTS/esp8266-devkit/tree/master/Espressif/examples/ESP8266. But, for little jobs.


texts:
it's a theoretical question.
is there any voltage drop when measuring a 12v battery with a multimeter(voltmeter mode)?
so if we get 12 Volts reading near the battery, does this changes if we extends the cables of multimeter to 1 km ??


texts: Piezo Buzzer as analog sensor for ESP8266 Huzzah Breakout

texts:
I'm using Adafruit's Huzzah ESP8266 breakout board (overview & pinouts), and I'd like to take input from a Radioshack piezo on the analog input pin without frying it. (Piezo datasheet, for reference.)

I've found a few people with a similar setup using an Arduino, and it seems like at a minimum I'd need something like a zener diode and 1MΩ resistor, like in the basic circuit from this PDF (page 12). The analog pin on the Huzzah has a 1V max voltage, so my sense is that I've got to make some adjustments to divide down the voltage further, and maybe include a capacitor? Super new to EE, so any advice on including & calculating the proper values for components is appreciated.

The end goal is to take input from the piezo and use it to set hue + brightness of an RGB LED, similar to the Adafruit LED ampli-tie project, but obviously with just a single LED. I can provide more details on that if it's relevant to getting up and running with the piezo input.


texts:
I am taking apart this non-invasive blood pressure monitor to see how it works. The engineer decided to use (what looks like a piezo-electric element to measure the relative pressure from the cuff, only I cannot decipher the circuit and how it works. It appears to be using a quad NOR gate to amplify the signal before it is sent to the MCU. The question I have is how is it able to measure the exact pressure from the cuff when NOR gates output digital signals?

Attached are photos and schematics.


texts:
SE,

I've used the SE:EE forum search and several search engines internet and haven't found a single question similar to mine. But I don't think that it's that complicated, I'm just having a hard time grasping what's going on.

The output from pin 1 is a square wave signal with a peak of 14V. The Scope picture shows the reading at pin 5.

Why is there a diode parallel to the resistor? What does it do? If I'm putting a square wave through this circuit, why is it coming back as saw tooth?

I'm having a hard time visualizing when the diode opens, what happens to the rest of the circuit and why I'm getting the output at pin 5.


texts: Improving load regulation on voltage regulator

texts:
Basically, I'm building a device that powers a number of LEDs; each LED needs to have as consistent a power as possible (each eats 25mA at 3.3V) across the number of LEDs being lit up.

I'm using a L78L33C 3.3V regulator drawing from a 5V wall wart to supply power to the LEDs but I notice that each L78L33C has a load regulation of 60mV from 1mA to 100mA.

Since I need each LED to have extremely consistent brightness (+-20mV), I'm worried about the 60mV dropout.

Is there any way to ensure the power output for each LED stays exactly the same regardless of the number of LEDs I'm powering? Will putting multiple L78L33C in parallel with the LEDs help?

L78L33C datasheet: Here


texts: Finding the energy over the capacitor in DC

texts: I tried using Thevenin to solve this and found Rth = 3 and Vth = 12 but this is way off the correct energy of the capactor (the energy is 4J).


texts: Help identify flexible angled pin component

texts:
Please help me identify these angled flexible pins in the center of this ESP-WROVER programming board. I'd like to add them to my custom boards so I don't need to solder in the ESP32s.
What is the name of these? Where can I buy them? Aiming to find the same or similar one, possible with an available model for EasyEDA.


texts: How do I dead bug solder this SOT-23 to my PCB?

texts:
I swapped the base and emitter of my NPN transistor land pattern. If I flip over the part, the pins are in the correct orientation, although there is a 1mm between the pins and the pads. When I tried to solder one I just made a mess. I soldered wire wrap wire in the vias and then tried to solder the wire to the pins. Is there a better technique?

Here is a photo of the part before I would desolder:

Here is the mess I made of a different one:


texts: In a circuit involving integrated circuits, the documentation for the ic often states that if a pin is in logic 1 or high the circuit will behave in one way, and if the circuit is in logic 0 or low the circuit will behave in another way.  One example i found was experimenting with the 4029 CMOS Counter ic http://www.intersil.com/content/dam/Intersil/documents/fn33/fn3304.pdf on the up/down and dec/bin pins. What i don't understand, is what the pin that is set either high or low should be connected to i would assume it would be the positive supply voltage, the negative supply voltage, or neither, but i can't seem to figure out which one.


texts: Why do opposing magnetic fields in the same core cause the core to heat up?

texts:
I inherited a choke of an odd design, with two windings on the same core. Separately, each winding was about 30 uH. In series, they were about 90 uH. When used in a split-bus boost converter, one winding was in the positive leg, and the other in the negative leg.

simulate this circuit – Schematic created using CircuitLab

When connected with matching polarity (fluxes additive in the core), the choke worked fine. When connected with opposite polarity (fluxes subtractive in the core), the inductance dropped, and the core got extremely hot. Running comparable currents, the core went from 130C to 250C. just with that change. The windings aren't getting that hot, it's definitely the core.

My understanding of core losses is limited, but this doesn't fit with even the little I know. If two identical windings of opposite polarity are on the same core, seeing the same currents, the flux density in the core should cancel out to zero. So where's the heating coming from?

Edit: By request, I've added a photo of the choke.

Two U-cores with a gap between. The upper part of the top U-core is blocked from view by a piece of cardboard. The two windings on the right are in series, and the two on the left are in series, so we treat the right side together as one choke (L1), and the left side together as the second choke (L2). The hottest observed part of the choke when the windings are run inverse from each other is in the middle of the exposed part of the lower U-core. I suspect the upper U-core is equally hot, I just can't measure it as easily.


texts: MOSFET Selection criteria considering conduction losses, switching losses and working frequency

texts:
I am trying to choose a suitable MOSFET for my full-bridge resonant converter for wireless power transfer. The circuit topology is something like the following.  Specifications: rated power \$-~500 W\$,  DC supply \$-~50 V\$, switching frequency \$-~200~kHz\$

I need some help to determine the best-suited MOSFET for high-efficiency considering conduction and switching losses.
Here is my approach so far:
I have been following MOSFETS Selection guide by Infineon

Decide the range of MOSFETS based on \$V_{DS}\$ and \$I_{D}\$ (selection \$V_{DS}=100V\$ and \$I_{D}@T_A=25^0C>20A\$)
Select the package type to have sufficiently low lead inductance at switching frequency.

Question 1 - What are the suitable package types at \$200~kHz\$ switching frequency? For example, Is \${\rm D^2PAK7pin}\$ good enough, or should I go with something like TO-Leadless/QFN? What is the rule of thumb for package selection at different frequencies? see below picture.

Next, I look at the specifications such as \$R_{DS-on}\$, \$Q_{g}\$, \$C_{oss}\$, \$FOM=R_{DS-on}\times Q_{g}\$, etc. For example, the following is the comparison of six different \${\rm Infeneon-OptiMOS^{TM}5}\$ MOSFETS (This list can be very long!).

This is where I am lost.
Question 2 - Can I just chose only based on the above \$FOM\$? What are the other criteria for setting up the boundaries? For example, What will be the maximum allowed \$C_{oss}\$ for these specifications (i.e., at 200 kHz)? I can only find generalized claims about these relationships in the literature.
PS. I have been trying to simulate my circuit with LTSpice, but the simulation was not successful with the available spice models - It takes a very long time to simulate and return an error. I am working on getting the simulations done, anyway I am interested in a faster method for such comparison. Therefore, I want to rule-out the answers "just simulate it and compare the losses"


texts: Why is an inductive load presented as a resistor on schematic diagrams?

texts: The presentation of a resistor load, such as a light bulb, as a resistor on a schematic diagram makes sense to me. However, why do we present inductive loads as such, seeing it isn't a resistor as such?


texts: Can NiMH type AA battery charger be used for other types like AAA, C, or D (all NiMH)?

texts:
As the title states, I would like to know if a battery charger for AA NiMH batteries could be used to charge also AAA, C and D battery types (all of which also of NiMH type).

I am aware of that physically they won't fit in, therefore I would need to connect them with wires. I am asking more voltage and charging algorithms wise. Would it damage the batteries or would the charger get damaged itself? Why?

I think all of them are of same voltage.

Thank you!


texts:
I'm working on a portable battery-powered device with a shielded I/O connector for sensors, but I'm confused about how to properly ground the shield and ESD array. Here is a block diagram of my conceptual device:

I'm assuming that grounding the USB connector and it's ESD array to the chassis ground is the right way to go, but should I also ground my I/O connector and it's ESD array to the chassis ground? If the device was running on USB power, the chassis ground would be connected to earth through the host PC. But if the device was running on battery power, the chassis ground would be floating. In this case, should the chassis ground be connected to the system ground somewhere? Wouldn't this cause some of the ground current to flow through the USB cable when it's connected?


texts: Different voltage differences for a UART signal (when tested from one microcontroller, vs when tested between two microcontrollers)

texts:
I have a question regarding UART signals.
I am doing a project where I press a pushbutton (BTN0, BTN1, BTN2) it registers at a microcontroller (MSP430FR6989), transmits a signal to another microcontroller (PIC24FJ1024GB610) and it in return toggles one of the LEDs (LED0, LED1, LED2).
both micros have a High logic of 3.3V.
I programmed the MSP430 to transmit a signal via UART, and the PIC24F to receive a UART signal. Tested them separately both were working properly.
I debugged the MSP430 Tx pin with reference to the ground with an oscilloscope, when I press a button I get this signal:

However when I connected the TX pin of the MSP430 to the RX pin of the PIC24, pressed the button I get this signal:

I thought maybe the problem was the grounds weren't connected together only the MSP430's TX pin was connected to the PIC24's RX pin, like in the figure below:

However when I connected the grounds together (like in the figure below), the problem didn't go away:

Can someone help me with my issue.
PS I am using Explorer 16/32 development board for the PIC24 and MSP-EXP430FR6989 for the MSP430
EDIT 1
This is the code relevant to the PIC24 UART pins FYI
UART_Setup.h
#ifndef XC_HEADER_TEMPLATE_H
#define XC_HEADER_TEMPLATE_H

//code

#define CONFIG_U1TX (RPOR2bits.RP4R = 3)//RP4 -> U1TX -> P69
#define CONFIG_U1RX (RPINR18bits.U1RXR = 3)//RP3 -> U1RX -> P70

//code

void setup_UART_Pins (void);

//code

#endif

UART_Setup.c
#include "xc.h"
#include "UART_SETUP.h"

//code

void setup_UART_Pins (void)
{
    TRISDbits.TRISD10 = 0;
     //just changed TRISD10 from 1 (input) -> 0 (output)

    TRISDbits.TRISD9 = 1;
    //just changed TRISD9 from 0 (output) -> 1 (input)

    CONFIG_U1TX;
    CONFIG_U1RX;

    asm volatile    ("MOV #OSCCON, w1   \n"
                    "MOV #0x46, w2      \n"
                    "MOV #0x57, w3      \n"
                    "MOV.b w2, [w1]     \n"
                    "MOV.b w3, [w1]     \n"
                    "BSET OSCCON, #6");
    //this is for the PPS
}

 //code

in main.c
#include "xc.h"
#include "UART/UART_SETUP.h"

//code

int main(void)
{
    //code

    setup_UART_Pins ();

    //code

    while(1);

    return 0;
}

EDIT 2
Thanks to the advice I got here, I fixed the issue, it turned out I wrongly configured the UART pins of the PIC24, I fixed the code and the issue was gone.
Here is the new relevant code:
UART_SETUP.h
#ifndef XC_HEADER_TEMPLATE_H
#define XC_HEADER_TEMPLATE_H

#define U1RX_INPUT (TRISDbits.TRISD9 = 1)
#define U1RX_CONFIG (RPINR18bits.U1RXR = 4)

#define U1TX_OUTPUT (TRISDbits.TRISD10 = 0)
#define U1TX_CONFIG (RPOR1bits.RP3R = 3)

//code

void setup_UART_Pins (void);

//code

#endif  /* XC_HEADER_TEMPLATE_H */

In UART_SETUP.c
#include "xc.h"
#include "UART_SETUP.h"

//code

void setup_UART_Pins (void)
{
    U1RX_INPUT;
    U1RX_CONFIG;

    U1TX_OUTPUT;
    U1TX_CONFIG;

    asm volatile    ("MOV #OSCCON, w1   \n"
                    "MOV #0x46, w2      \n"
                    "MOV #0x57, w3      \n"
                    "MOV.b w2, [w1]     \n"
                    "MOV.b w3, [w1]     \n"
                    "BSET OSCCON, #6");
}

//code


texts: Do the RAM modules use Flash as the USB keys and SSD?

texts:
USB keys and SSD use the flash technology for their memory ; I don't have a great knowledge in electronic but I think RAM modules use this same technology. Could you tell me if I'm right please ? More precisely : do you know if the flash used by RAM modules (if it's the case) is totally the same than USB/SSD's one or if it's a bit different ?

If RAM modules use exactly the same Flash than USB and SSD, it would be possible to use these hardwares rather than RAM modules no ? (if USB ports are replaced with other stuff)


texts: Square wave, triangle wave etc. not defined in International Electrotechnical Vocabulary (IEV.) Are they not standard terminology?

texts:
Why are there no definitions for typical terms like square wave, triangle wave etc. in the International Electrotechnical Vocabulary (IEV)?
Are these widely used descriptions not defined by international standards?
And if so:
Why?
Is there a more correct terminology one should use instead?
I have also searched through German standards and did not find any mention of terms like "Rechteckspannung" (square voltage) and the like.


texts:
I’m trying to find out if a device only draws the watts it needs to run or if it takes all available

For example

I have led light that’s says max 0,75 watts and the led controller says output 144 watts will the device received 144 watts or will it only take 0,75

So I’m wanting this https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F113084461265 to work with the rgb one of this https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F121282462726


texts: Latch-based sense amplifier design using CADENCE Virtuoso 65 nm technology

texts:
I am trying to design a latch-based sense amplifier to sense about 55mV voltage difference using 65nm technolgy, it takes differential input, and should get from it differential output too where it drives one input to VDD and the other to gnd. I don't know why the pass transistors are always in region 0. These are the waveforms I get I don't know where the problem is or what solutions should I think of..

]2


texts: Laplace Domain Transfer Function for Feedforward System

texts:
I am trying to obtain the overall transfer function of this feed-forward system which consists of an oscillating input being mixed with a local oscillator to create a mixed signal as the output. G1 and G2 represents the transfer functions for some filters, amplifiers, etc.
My question is, considering that the transfer function for some component is given by the output/input signals \$\frac{OUT(s)}{IN(s)}\$, how is this represented for the mixer, and therefore for the overall system? Is it correct for me to break up the overall system into 3 parts such as
$$\frac{U_{g1}}{U_i}\left(\frac{U_m}{U_{g1} + U_{lo}}\right)\frac{U_o}{U_m} = G_1T_1G_2$$
Where \$T_1\$ is the mixer's transfer function? I think my confusion may be coming from a misunderstanding of block-diagram algebra... any clarification would be greatly appreciated.

simulate this circuit – Schematic created using CircuitLab


texts: Where to plug LED on Arduino due for blink demo?

texts:
so, I got a Arduino Due, but I am somewhat confused about the pin layout.

As a simple setup, I want to have some LEDs blinking. On my host laptop, I use Node and Johnny-five like here: https://github.com/rwaldron/johnny-five/wiki/Getting-Started

But when it comes to the Arduino board, I am confused.
I found a board schematic here: http://forum.arduino.cc/index.php?topic=132130.0

But how and where should I connect the LED to have some basic strobe.


texts: Why do we need bulky filters at the input stage of SMPS designs?

texts: I usually see costly and large filters at the input stage of switch mode power supplies. Isn't the AC signal already filtered by the large capacitor (the 100\$\mu\$F one in this example) after the bridge rectifier? What is the necessity of such an elaborated filter network encircled in red?


texts: Relation between stability and overshoot?

texts: Is there any relatonship between stability and overshoot? I mean, can we say that a system if it is marginally stable, it will not have overshoot?


texts: LT3081 Precision Current Limit Programming

texts:
I am trying to precisely control current limit of the LT3081 IC following this paper, page 12, schematic on page 14, but by using a microcontroller.

I'm controlling the output voltage with a 10kOhm, 8 bit, digital potentiometer, which I feed with 1.2mA constant current to make it regulate the output voltage between 0 and 12 V.

I'm trying to limit the output current from 1 mA to 1A, idealy with 1 mA step, without using more expensive 10 bit digital pots. By using a similar configuration as shown in the schematic for higher accuracy (pot + paralel res + series res), using one 10k, 8 bit, digital pot and considering the wiper resistance, I got to a point where I can control the current limit with a 7 mA step at lower values, and 2 mA steps as I get closer to 1 A limit.

Spreadsheet for 10k 8b values: link

Equation for current limit(from datasheet):
RILIM = ILIMIT/360mA/kΩ + 450Ω

Simplified equation: RILIM = ((ILIM*1000)/0.36) + 450

Simplified schematic:

simulate this circuit – Schematic created using CircuitLab

My question is: Is there any other way for a more precise current limit control without using a higher step count (bit) digital pot?


texts: How is it possible to create a stable DC generator?

texts:
A permanent magnet moving in and out of a coil will produce an AC power source (much like a microphone), but in order to produce a DC power source, you need to move that magnet in one direction only.

The only way I can think of to do this is to have coil or wire in a circle with the magnet moved inside the center of coil going around the circle, but there's no way to get a mechanical connection to the magnet without destroying the coil?

Is it not possible and one must have "pulsed" generators with commutators to switch the polarity of what would otherwise be AC generation?


texts: How to connect ATTiny45 to Arduino via serial/spi/i2c and send data?

texts:
I am trying to create a smart alarm system for my house. I want to have one arduino as the master and several other AtTiny's as slaves to collect data as temperature, moisture, gas concentration, opened doors etc.

How do I connect multiple wired AtTiny's to a master Arduino? Which is the most clever way to communicate between them ? I have read that AtTiny's do not support spi or i2c but you can "hack" it somehow.

EDIT: the distance between the master and the slave can be 1 to 10 meters.


texts: Component / design to pass voltage when two inputs have continuity

texts:
I am trying to make a test box that you will plug up a RJ45 ethernet cable into and it will have 4 green LEDs that will light up independently if each of the 4 pairs of the ethernet cable are shorted/have continuity. The ethernet cable will not have voltage across it. I need each color pair in the cable (blue/green/orange/brown) to trigger the LED to light if it has continuity. I am not sure how to accomplish this since there won’t be voltage (or any signal) on the cable.  It will either be in an open or shorted state. I plan to use a 9V battery inside the box to power the LEDs.
Note: This is not being used for any network type application. It’s just checking for a closed or open state on an RJ45 connector.


texts: Do an Op-amps supply pins need to have the exact same nominal voltage?

texts:
By power supply unit should ideally output +12 and -12V, however the readings are closer to 12.2V and -11.8V.

Is this likely to cause a problem, even though I only need an output range of 10V to -10V?


texts: More on standing waves in a dipole antenna

texts:
I have a background in physics and I'm trying to get into antenna theory for a personal project.
I had some questioning about standing waves, and reading Standing waves in Dipole antennas and the  enlighting answers of @Vinzent, I would try to summarize and to point out some yet not-so-clear points:
The antenna is a continuation of the feed line coupled with vacuum by mean of an altered geometry. This alteration bring in impedence and reactances that can be modeled by an RLC circuit. Such circuit are know to resonate and store energy exchanging it between the C and the L component, the role of which in the antenna is played by E and H components of the induction field and by current and voltage standing waves. The resistive losses and radiative losses are restored by the feed-in voltage and current which are in phase and thus actually carry power.
What I still don't understand well is why the waves reflected from antenna tips do not propagate back across feed line. Maybe an impedance missmatch, as seen from antenna towards line, prevents this to happen?
If so, such mismatch would not simmetrically affect line signal and reflect it back to source?
Also, the statements:
Resonance however is not to be confused with standing waves.
I would advise you to read up on resonant circuits, I think it can help you understand what happens to the wave inside the antenna (it is roughly equivalent to a parallel RLC circuit) are highly confusing. A standing wave is a physical phenomena that occurs everywhere there is a oscillations susceptible closed system, bounded by some boundary conditions. Resonance is the response of an oscillating system to some forcing term. Eg: A guitar string oscillates by mean of standing waves and can be in resonance with a sound source. Both these aspects are present in an antenna. The equivalence with an RLC circuit can be invoked because of some real analogy, but the antenna is a physical system and thus each statement, Eg. "standing waves do not propagare back to line" must have a physical explanation, which, at the moment, I was not able to find even in literature.
Thanks for any comment.
As pointed out by @user287001
the wave equations must be solved simultaneously around the whole rods to get any idea what happens. this is clear. Also, you are affirming that the standing wave is a consequence of the solution of this equation (precisely the induction field part) not of the reflection by antenna tips. This make sense. However, I would like to note that if the standing wave assumption works good in describing the current, voltage and the field also outside the antenna (e. g. there is a derivation of the radiation lobe for the short dipole based on this) probabily it is because there is really a standing wave in the antenna, so there must be a reason why this oscillation does not propagate back to line, and the only possibility seems to me an impedance mismatch towards the line. This is not asking a miracle, is simply asking physical consistency to a model.


texts: Avalanche Breakdown Noise as digital input

texts: I am trying to develop a true random number generator using reverse biased transistors avalance breakdown noise as a input for pic microcontroller. How can i turn the noise in to a digital input ? Is it possible ?  If i program the pic for make a digital input read , shall i say 100 times in a second , is it possible to digitize as 1 and 0 ?


texts: Can a laser display numbers like an LCD 7 segment display?

texts:
Possible Duplicate:
  Is there a way to convert a 7 segment display to be displayed by a laser beam?

I am a 12 year old child with a growing interest in electronics. I want to have a laser project numbers like a 7 segment display. Is there a way to hook a 7 segment display up to a laser to have the laser display the numbers onto a flat surface?

The design needs to be as compact as possible. Do you know if maybe there is an electronic converter or way that can be used to hook it up in place of the 7 segment display? Like this:

Binary for the 7 segment display -> ??Mystery part described above??? -> Laser display module.

I just started electronics a few days ago, I've got some grasp on the basic stuff, but I could really use some help here. I have a very limited amount of resources available and needed to ask people who know what they're doing.


texts:
In widening Karnaugh map, what Mirroring means?

I can not understand the name of Mirroring, could you explain?


texts: What would happen if a negative voltage is given to an op amp adder circuit?

texts: Would it subtract that voltage because it would reduce the total current going on the feedback resistor ?


texts: How does grounding prevent electric shock?

texts:
I understand that an electrical appliance will be connected to ground to provide a path back if there is a fault and a live wire touches the case.

However if a person is also touching the case at this point then surely there will be a current through both paths? Because a person is like a parallel resistor to the ground connection. The current won't be as great, but it will be enough to be dangerous.

Do we just hope that the breaker will blow quick enough to prevent the shock happening for too long?


texts: Step up DC-DC converter for powering Raspberry Pi from batteries

texts:
I will power a Raspberry PI with 4 NIMH batteries, but they quickly lose charge, and end up at 3V instead of the 5V needed. I was wondering about a DC-DC step up converter.

I want a converter that will have a fixed output and will not be affected by the input voltage. E.g. This may transform 3V to 5V, but when the batteries are fully charged at 5V, I want the converter to output 5V too rather than 7V for example which will damage the PI.

I was thinking of using this converter, would this work?
XL6009 DC-DC Step Up Boost Voltage Converter Power


texts:
Asked the question here :

I would like to understand Complementary Code Keying. How modulation and demodulation is done ?
How higher data rate is achieved using CCK modulation in IEEE 802.11b ?

What is Hadamard transform encoding specified in IEEE 802.11b spec ? How demodulation can be performed on the received samples.

https://stackoverflow.com/q/5551869/630661


texts: Avrdude refuses to flash ATmega328p due to wrong signature

texts:
I have a bunch of defunct arduino boards that I'm trying to restore - Arduino Uno with ATmega328p chips. They do not respond to the usual flashing commands, so I'm trying to flash via the arduino ICSP headers, through an intermediate bus pirate.

The process fails due to an invalid signature, like so:

$ avrdude -c buspirate -P /dev/buspirate -p m328p -v -F

avrdude: Version 6.0.1, compiled on Sep 21 2013 at 11:40:49

         Using Port                    : /dev/buspirate
         Using Programmer              : buspirate
         AVR Part                      : ATmega328P
         Chip Erase delay              : 9000 us
         PAGEL                         : PD7
         BS2                           : PC2
         RESET disposition             : dedicated
         RETRY pulse                   : SCK
         serial program mode           : yes
         parallel program mode         : yes
         Timeout                       : 200
         StabDelay                     : 100
         CmdexeDelay                   : 25
         SyncLoops                     : 32
         ByteDelay                     : 0
         PollIndex                     : 3
         PollValue                     : 0x53
         Memory Detail                 :

                                  Block Poll               Page                       Polled
           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
           eeprom        65    20     4    0 no       1024    4      0  3600  3600 0xff 0xff
           flash         65     6   128    0 yes     32768  128    256  4500  4500 0xff 0xff
           lfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           efuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           lock           0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           calibration    0     0     0    0 no          1    0      0     0     0 0x00 0x00
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00

         Programmer Type : BusPirate
         Description     : The Bus Pirate

Attempting to initiate BusPirate binary mode...
BusPirate binmode version: 1
BusPirate SPI version: 1
avrdude: Paged flash write enabled.
AVR Extended Commands not found.
avrdude: initialization failed, rc=-2
avrdude: AVR device initialized and ready to accept instructions
avrdude: Device signature = 0x881608
avrdude: Expected signature for ATmega328P is 1E 95 0F
BusPirate is back in the text mode

avrdude done.  Thank you.

(this is just running -v but trying to set fuses or flash fails the same way)

Weird thing is that the device signature changes slightly on each attempt, so something is definitely not behaving correctly.

I tried the same process by hooking up to the atmega328p pins directly (and not via arduino board ICSP header pins), but with no success.

Is there any salvaging the atmega328p or is it beyond repair?


texts: How to power my 12V Kinect from an 11.1V LiPo battery?

texts:
I'm wanting to connect my lipo to a computer for use in a remote area. I have to use a lipo and I have an idea but I want to make sure I'm not going to blow anything up.

Lipo to car cigarette lighter socket
Car cigarette lighter socket to small dc/ac inverter
inverter ac outlet to computer

Will this work? Can I be more efficient without cutting wires? Do I need to add a low-voltage alarm?
Also, what if I want to power another device on the same lipo?
** EDIT **

(1) And what computer is using a 12 V AC supply?
(2) Have you calculated your power budget? Use P = V x I.
(3) Then figure out how many watt-hours (Wh) you need.
(4) Then calculate the Wh capacity of the battery.

I'm powering a 12v Microsoft kinect via an AC/usb adapter.
Power budget is roughly 6400mAH x 20C (= 128.00A)
I don't completely understand Wh but I'd like to get at least an hour out of the battery.
Wh of the LiPo battery is 6400 x 11.1 = 71.04

** EDIT **
I'm finding out that my current Kinect adapter converts the power from AC/DC in the first place so I can skip that by going straight into DC power, the steps of which are mentioned is this battery to kinect adapter tutorial


texts: I have to replace Renasas M30853 MCU with STM32F407 MCU in a circuit. The earlier MCU uses power supply Vdd = +5V as well as all the analog and digital circuit that is connected with it. How can I use STM32F407 MCU or any of its variant to use +5V power supply?


texts:
I'm trying to detect small current pulses (~1.5mA). Currently I'm generating a ~20mV pulse on a sense resistor and feeding that to the input of an opAmp with some hysteresis. I'm having a bit of trouble where the output of the OpAmp will sometimes latch low and not return after the pulse passes and would like to try to use a comparator for the circuit. The problem I'm having with that is that my supply and my input are both at 6V.

Can someone recommend a good comparator that has full common mode input range with no more than 10mV of hysteresis? Or instead a better design overall?

I've found this part that seems to come close but the hysteresis might be too much.

*Based on some of the replies so far, I should mention I have a 3V3 rail available as well on the board if that helps.

EDIT: Redesigned circuit based on below suggestions- yet to evaluate


texts: Are there other quantities besides voltage and current that can be expressed as instantaneous values in AC circuits?

texts:
https://www.electrical4u.com/emf-equation-of-transformer-turns-voltage-transformation-ratio-of-transformer/
I got really confused when all of a sudden they treated flux with the time domain equation notation. This is my first time seeing this. My question is simple, are there other quantities besides voltage and current that can be expressed as such in AC circuits? I just got curious would like to be exposed to the idea or not confined that only voltage and current exist in such a manner.
This is in the context of AC circuits because in general probably you could put any quantity in the y-axis and make a sinusoid and say it can. I want to see quantities that are related to AC circuits and may have some application.


texts:
I recently came into possession of two large (approx. 3x4 ft) copper-clad fiberglass boards from a junk sale. These boards are consistent with typical printed circuit board material (thickness, flexibility, internal appearance, etc.), save for a blue coating on both sides. Here are two small pieces I cut off for testing:

Here I've sanded off some of the coating to reveal the copper underneath (the cuts are from me testing my PCB mill):

The copper is conductive (unsurprisingly), and the coating is not.

Any ideas on what the coating might be? The boards are probably around 5-10 years old, and were covered in a thin plastic sheeting when I obtained them.

Specifically, I'd be interested in knowing (a) how to remove the coating without damaging the copper (solvents? acids? photoexposure?) and (b) if I could use the coating in some way to help make printed circuit boards (as a resist material? ablate with a laser cutter?).


texts: How does a ball mouse know the direction?

texts:
Foreach axis on a mechanical (ball) mouse there is an IR transmitter and receiver pair with a wheel that looks like having only simple slits.

How is the direction calculated?


texts:
I have a TFT which requires SPI Communication interface to get it configured.
My questions :

When we say, "configure the tft", what do we actually do? Do we set some bits or erase some bits inside he tft? If so, what purpose do they serve?

The TFT also has LVDS Data and LVDS Clock lines. Then why does it require a separate SPI interface to configure instead of using the LVDS Data to send the data and do the configuration?

I have a microcontroller and a deserializer. Can I use the Microcontroller with SPI interface for the configuration part and use Deserializer for sending LVDS Display data?


texts: What are the purpose of C38 to C51 in this design?

texts:
I came across a BLDC drive circuit design and you can find the design here (https://danstrother.files.wordpress.com/2011/01/danstrother_mtrdrv1_20080629.pdf), and here are the picture of the finished PCB.

Basically, it is a simple design, but I couldn't understand the purpose of C38 to C51 in this design. It already has a electrolytic capacitor for DC link. If a bypass capacitor is needed, why are there so many 10uF capacitor?
If they are used to help the electrolytic capacitor to filter out the switching noises in the inverter part, what kind of calculation should be used to get the proper capacitor values or the number of capacitor in parallel?


texts: Creating a ZigBee Light Link Compatible Light

texts: I've seen lots of talk about using arduino/pi/etc and a zigbee board to talk to existing ZigBee Light Link compatible lights such as the latest Phillips Hue bulbs. But I want to go the other way... I want to make the light but be able to use that with any existing ZigBee Light Link supported hub device (Samsung SmartThings, Wink, etc). But sadly, aside from the official ZLL spec doc, can't really find anything.  Maybe this just isn't done outside of large corporations? I'd really love to be able to just use, for example, and arduino compatible chip, ZigBee radio, and then appear to a home automation hub as a ZLL compatible light.


texts: WWVB antenna interferance from AC/DC converter supply

texts:
I'm working on a design that uses a WWVB antenna receiver....

The WWVB antenna is a small (~ 1/4" x 4" rod). Size is not a constraint so I could make it much bigger if a I half to.

The design is powered by AC/DC converter w/ SMPS. Its an unenclosed module I got off digikey. Whenever the Supply is on and near by the antenna receiver cannot pick up a signal.

The antenna & Powersupply have to be able to operate together in a small enclosure. How can a shield the Antenna from the noise?

Design a receiver that has better filter?

Use ferrite RF shielding sheets?

Design a larger antenna?

Position the Powersupply so that it emits noise perpendicular to the antenna's sensitive direction?

Thanks


texts: My collpitz oscillator doesn't oscillate

texts:
I wanted to understand how colpitts oscillator works and so I tried to simulate one in proteus.
I have a common emitter amplifier with a gain of -10 (inverter) and a the tank circuit with the 2 capacitors has a gain of -0.1 at resonnance so I would expect to have some maintained oscillation at the output of C6, but I don't get oscillations. Why is that? (don't pay attention to the oscillation on the left figure, it is for an other circuit).

edit

strange, I added a 10uF decoupling capacitor between the emitter of the BJT and the ground and now it seems to oscillate. Do you know why?


texts:
The ground clip for an oscilloscope lead is normally connected within the instrument to the power supply earth, and there are surprising circumstances where this could matter. The situation is very well explained in "EEVblog #279 – How NOT To Blow Up Your Oscilloscope!"

Leads with galvanic isolation are very expensive, so, is there a good home-brew design or kit available? I realise that protection against high voltages might put this outside the home-brew area, but one for lower voltages would protect against dangers, such as that, described by Dave Jones in the EEVblog, of destroying the on board regulation of an Arduino via the ground connection of a USB lead.


texts: how do I make a solenoid operate after a random number of switch presses

texts:
New to the forum because I am stumped. Im building what I am calling the "water table" for my kids. It has a series of spigots, and channels that funnel into a kiddie pool. Then I got creative and added some solenoids to make some quirt guns that run off of line pressure. They are SWEET!

I have 2 solenoids left to find a function for. My oldest wants me to get a push button that will randomly shoot the person standing in front of the button. So, you can press it anywhere from 1-10 times before it goes off and every time its a different number of pressure. Kind of like Russian roulette... but for kids lol

I just spent the last hour googling things with no results, but I found this page and thought someone would be able to point me in the right direction. Any thoughts or input would be great!

Thanks!!


texts: How to mitigate common mode noise introduced by the (LF) RFID antenna driver (on un-earthed SMPS)

texts:
When powering my RFID reader board using a SMPS without GND-PE connection, I can observe quite an amount of common mode noise:

~340Vpp from mains.

~4Vpp @ resonant frequency of the antenna. (This vanishes when disconnecting the antenna)

This common mode noise (4Vpp) is I believe the cause for read-range degradation. With a GND-PE connection, the common mode noise is eliminated as well, but I'm interested in addressing the issue on the board rather than at the Power supply if possible (especially since low-power PSUs rarely include a GND-PE connection).

Experimental setup:

The power supply used is of a rather cheap variable voltage type product link and has settings from 3V to 12V rated @ 1A. I currently use it, set at 12V. Power draw is between 40-65mA.
It is of the "double insulated" type, with two connectors for the power sockets L+N, and no PE connection.

The Scope is set to AC coupling, the little crocodile-connector from the scope-probe is disconnected/removed and the measurements were taken using the tip of the probe at various points on the board, all exhibiting a similar common mode noise pattern as seen above. Regardless of GND/+5V/+12V rail.

I probed differential noise as well, which is in the oder of a few mV synchronous to the Antenna driver and is exhibited stronger closer to the Antenna driver power input pins.

P.s. this Question is in continuation to: RFID reader sensitivity/read range - How does a "hard" ground increase sensitivity/read range?


texts: Level shifting with BSS138 - weird values

texts:
I need to connect 5V and 3.3V devices via I2C as follows:

I've connected 3.3V and 5V pull-ups and tried to measure the voltage. There is 5V on HV and TX_HV but 4,7V on LV / TX_LV.

Putting TX to LOW generates LOW on the other side, but I have a problem with 3.3V - I see cca 4.7V.

My PCB:


texts: How to discharge the pn junction capacitance

texts: Suppose the pn junction is reverse biased, so the width of the depletion region is large as shown. Now I disconnect the battery. What happens to the ions in the depletion region ? I think the depletion region tries to get back to the width corresponding to its barrier potential. But I have difficulty in visualizing how exactly this happens. Any help is appreciated. Thanks!


texts:
I have build a circuit as follow. From 5V a 220 Ohm resistor to a LED to a 2N3904 transistor to 0V. The base of the transistor is connected to a 10K Ohm resistor to a switch to 5V.

When I measure the voltage across the transistor from collector to emitter with the switch open I measure 3.43V and with the switch closed 73.4mV.

From what I have read I expected a somewhat higher voltage drop with the switch closed. Is this low voltage to be expected with a circuit like this?
And the part I don't get is why I measure 3.43V with the switch open. Also with the switch open I measure 3mV over the LED and 0V over the resistor. That doesn't match the 4.98V measured from ground to +5V.
Is my voltmeter affecting what I am reading?


texts: Spartan 6: How do I use my differential clock?

texts:
my SP601 Evaluation Board comes with one 2.5 V LVDS differential 200 MHz Oscillator. Until now, I have only been using the single-ended clock provided with the board. I am having trouble with how to format the user constraints file to use the differential clock. Here is what I have in my user constraints file so far.

NET "clk_N" LOC = "K16"; ## 5 on U5 EG2121CA, 5 of U20 SI500D (DNP)
NET "clk_P" LOC = "K15"; ## 6 on U5 EG2121CA, 4 of U20 SI500D (DNP)

What I had before, when I used the single-ended clock, was:

NET "clk" LOC = "V10"; ## 5 on X2 USER OSC Socket
NET "clk" TNM_NET = "clk";
TIMESPEC "TS_clk" = PERIOD "clk" 37 ns HIGH 50%;

In addition, after I successfully include the clock in my user constraints file, what changes do I have to make to my code to switch from the single-ended clock to the differential clock? Originally, I have one signal called clk, and I trigger off the rising edge of this signal. Now that I have two signals, the rising edge method doesn't seem like it'll work. Should I make a new signal that is clk_1 - clk_2, where clk_1 and clk_2 are the two differential signals? I don't know if changing my clock source should affect how the rest of my code is written.

What I am saying is that I am new to FPGAs, and I have an idea of how differential signaling works in theory, but I'm not sure how it works out in practice. I'm using VHDL.


texts:
I have the following setup...
A laser-pointer pointing downwards at an angled 45 degree mirror which is rotating at about 600-2200rpm on a high speed electric motor.
As the mirror rotates the laser dot is reflected outwards around the room and moves sideways along the walls of the room in a large circle.
I want to be able to detect this laser dot when it passes a point with an optical sensor on the wall but the speed at which the laser moves means it doesn't focus on a photodiode with a circuit long enough to saturate it and turn it on.

The main solutions I've researched so far have been avalanche photodiodes and transimpedance amplifiers to increase the sensitivity and response time however I haven't found many reference circuits built for similar applications; I'm also concerned about other light setting it off but one problem at a time I suppose!

Can anyone recommend an area to research or material that would be worth reading or if possible a circuit solution to the issue that might be of use?

Many thanks for any help offered


texts: Composite HID gamepad descriptor works on Windows but not on Linux

texts:
I am building an USB adapter for an old game controller. So far everything is working fine. My HID descriptor looks like this:

0x05, 0x01,  /* USAGE_PAGE (Generic Desktop)       */
0x09, 0x05,  /* USAGE (Game Pad)                   */
0xa1, 0x01,  /* COLLECTION (Application)           */
0xa1, 0x03,  /*   COLLECTION (Report)              */
0x85, 0x01,  /*     REPORT_ID (1)                  */
0x05, 0x09,  /*     USAGE_PAGE (Button)            */
0x19, 0x01,  /*     USAGE_MINIMUM (Button 1)       */
0x29, 0x0e,  /*     USAGE_MAXIMUM (Button 14)      */
0x15, 0x00,  /*     LOGICAL_MINIMUM (0)            */
0x25, 0x01,  /*     LOGICAL_MAXIMUM (1)            */
0x95, 0x0e,  /*     REPORT_COUNT (14)              */
0x75, 0x01,  /*     REPORT_SIZE (1)                */
0x81, 0x02,  /*     INPUT (Data,Var,Abs)           */
0x95, 0x01,  /*     REPORT_COUNT (1)               */
0x75, 0x02,  /*     REPORT_SIZE (2)                */
0x81, 0x03,  /*     INPUT (Cnst)                   */
0xa1, 0x00,  /*     COLLECTION (Physical)          */
0x05, 0x01,  /*       USAGE_PAGE (Generic Desktop) */
0x09, 0x30,  /*       USAGE (X)                    */
0x09, 0x31,  /*       USAGE (Y)                    */
0x15, 0x00,  /*       LOGICAL_MINIMUM (0)          */
0x25, 0x64,  /*       LOGICAL_MAXIMUM (100)        */
0x75, 0x08,  /*       REPORT_SIZE (8)              */
0x95, 0x02,  /*       REPORT_COUNT (2)             */
0x81, 0x02,  /*       INPUT (Data,Var,Abs)         */
0xc0,        /*     END_COLLECTION                 */
0xc0,        /*   END_COLLECTION                   */
0xc0         /* END_COLLECTION                     */

Now I want to add support for up to 4 of these controllers. If I understand the
HID spec correctly, one way to do this is to repeat the descriptor 4 times, each time with a different report ID. (I know I could probably just have multiple USB interfaces with the HID class, but I'd rather not do it that way; my USB code would get a great deal more complicated.)

When I tried this Linux refused to recognize the device as a gamepad. The HID
driver (hid-generic) is loaded, and the descriptor seems to be parsed correctly, but there is no device file in /dev/input/.

EDIT:

I tested my code on Windows 7, and it looks like this problem is indeed Linux specific. So I am reformulating my original question:

How do I need to modify my HID descriptor, so it works on both Windows and Linux?

When plugging the device in, dmesg reports this:

usb 3-6: new low-speed USB device number 8 using xhci_hcd
usb 3-6: ep 0x81 - rounding interval to 64 microframes, ep desc says 80 microframes
input: XYZ Adapter as /devices/pci0000:00/0000:00:14.0/usb3/3-6/3-6:1.0/0003:16C0:05DC.0009/input/input20
hid-generic 0003:16C0:05DC.0009: input,hidraw4: USB HID v1.01 Gamepad [XYZ Adapter] on usb-0000:00:14.0-6/input0

This is identical to what it says when plugging in the working 1-controller version. The device appears in lsusb, with the correct IDs/descriptors.


texts: How to limit starting current of a SEPIC based LED driver?

texts:
I have designed a SEPIC based LED driver which gives 60 V, 350 mA constant  output with a good power factor. It is connected with 220 V AC source.Then I have used full-wave rectifier.After rectification I have used SEPIC converter for desired output(60 V, 350 mA) with good P.F. But here I feel the problem of its high starting current in the SEPIC converter.The starting current through MOSFET and inductor L2 is very high (18 A). Steady state current of those branches are within 2 A. I want to make the circuit in hardware. How can I limit the starting current of those branches around 2A? For better understanding fig. is given below-

Thanks. 18 A found in simulation.My requirements is to make an LED driver which is connected 22o Volts supply line and will deliver 350 mA constant current at 60 volts output voltage. I have used SEPIC converter here for step down the output voltage to 60 volts from 220 volts and to maintain a good power factor.  Here I am giving the circuit-

[![sepic based LED driver][3]][3]


texts:
I didn't have much input with the original post, so I'm taking a different approach now. How do I model a transient/lightning source whose output looks like the shown waveform when connected to the load (a filter that contains TVS diodes/transorbs that clamp the voltage)

Additional info: As seen in the output waveform of an actual transient generator, the output voltage hits plateau, stays constant while the current rises and falls in a parabolic path. enter image description here![enter image description here][1]![enter image description here][2]


texts: How to get UL approval for lamps and pendants

texts: I'm a glass artist and designer and would like to make lamps and pendants. I'm told that I need UL approval for the electrical part. That is all the wiring etc. I know I can have an electrician who can do that part but I'm concerned about the approval. Is that correct? If so what's the simplest way to do it since I'm a one person company.


texts: Need Help with the transistor configuration? Biasing methodology used in circuit?

texts:
I am confused about how this circuit works, the circuit is the instrumentation for IR sensor even I have never encountered the such biasing, the IR led is activated with the pulse of 150 us the output is attached as seen the image of scope
Blue trace - IR led pulse
Yellow - RX/output


texts:
How to select the type of capacitor for certain application? What are the parameters other than the voltage/current rating which should be considered while selecting a capacitor?
For example:
If I am designing a snubber circuit or a circuit for gate driver, how would I know whether I need a ceramic capacitor, a film capacitor or some other type?


texts:
Can I run a robo-car (with battery for electrical stuff) using this mini Air Stirling Engine ?

Using this engine, I can never power my motors. So I am looking to run my Robot directly on this engine (altering my chassis) ? Is it possible ? Whats are things I need to keep in mind ?


texts: Particularly for highly complex, digital ICs. Is it bottom up or top down? In particular, for top-down design designs the actual logic gates?


texts: 5 V from power bank not constant when supply circuit

texts: Now I'm working on my project which contains Arduino, LCD, electromagnetic lock, 6 channel 5v relay and 500V isolated converter. My project was designed to power by using a power bank. Now I use eloop E14 20000mAh power bank which can provide 5V 1A and 5V 2.1A so, I use 5V 1 A to powering the Arduino via USB and 5V 2.1A power the circuit. In the circuit part firstly the LCD consumes current about 200-300 mA and the voltage must maintain around 4.75 to 5.25 V. Next the electromagnetic lock consumes 12V 200mA so, I increase 5V to 12V by using a 5-12 converter that can withstand around 1-2 A and the 500V converter that uses the input of 12 V then boost to 500V and this converter consumes 8mA. And the last one 6 channel 5 v  relay which consumes around 70mA when power 1 channel and I only power 1 channel in a time The question is when I started to supply my circuit the voltage will drop to less than 4.75V so that the LCD will shut down. Can anyone tell me why is this happen?. I have calculated the total current of 5V 2.1A port which is about 508mA ( less than 2.1A). According to my understanding, I reckon that the 5V will start to drop when we supply the circuit that exceeds 2.1A, so why is this happen. Lastly, I power my circuit via USB-micro USB. Any assistance will be appreciated. Thanks


texts: Are these inductors or resistors and what function do they serve?

texts:
Some context: I'm trying to learn about ways to reduce EMI's effects on microcontrollers. I've got a Telemecanique logic module and decided to open it up to investigate.
I found myself with these:

Are those inductors or resistors rated for higher power consuption? When I measure them with the multimeter they turn up 5.6kOhm, but that's with them soldered to the board so the measurement is not very useful. they're paired with SMD capacitors and resistors.
They are in series with the input terminals.
What function do they serve?


texts: Replacement 100 ohm resistor for differential scope probe?

texts: I'm trying to use a P7504 ($$$) "TriMode" scope probe, and unfortunately the resistors eventually break. Does anyone have recommendations for a 100ohm resistor that would replace the ones on the probe? A new set of just ends is $1600


texts: What are the square holes for in most electronic project boxes?

texts:
I'm new to the electronic scene and lately I been purchasing a lot of project boxes for the stuff I make, I've noticed in about 75% of the boxes I purchase they come with small square shaped holes on both the base and the lid, I assume these are for some kind of mounting or for pillars. I've looked online and on here and I can't find any details.

Below is an example of one of the boxes I recently purchased of eBay.

What is the technical term for these and what do they do?


texts:
Please explain to me the working of this metal detector circuit.

Also,I have constructed this circuit but the problem is that I am getting the output(speaker) even when coil is disconnected from the circuit.
Where would the problem be occurring?

Additional information:The two coil terminals are having high impedance(from continuity check).

C4 with much lower impedance(is that normal)


texts: Are there any good references on advanced PCB design/layout/routing?  There seems to be a large wealth of circuit design books, books about RF PCB design, and books dealing with high-speed digital design. None of these books are what I'm talking about. The type of book I am looking for is along the lines of PCB best practices for general digital/low speed analog/power supply layout & routing. What is the de-facto standard book they use in college classes for this topic (similar to the way that Oppenheim et. al.'s Discrete-Time Signal Processing is used in many DSP classes, or Sedra & Smith's Microelectronic Circuits is popular in many Circuit Design Classes)?  Can anyone recommend a good PCB design/layout/routing book for this type of design?  Would a high-speed design book be a sufficient in that it would be overly-strict based on lower speed designs?


texts: What does KF mean next to a resistance value?

texts: I was browsing schematics for SC8915 and on the drawing many resistors are labeled with KF next to the resistance value. What does it mean?


texts: Work library is empty after compiling Verilog source file in Modelsim

texts: How I can solve this problem: my Work library is always empty after compiling a selected file in Modelsim?


texts: Relevance of amperage in a voltage divider circuit

texts:
I'm not very competent on the electrical engineering, so forgive me if this is a dumb question.
I'm trying to make a voltage divider circuit to monitor the battery level of a project I'm working on. It utilizes a 12v scooter battery and will be monitored by an Arduino and I'm going to be using the circuit defined here (also attached below) using the table values for the 15v max voltage to do it. I don't want to fry my Arduino because I cant really afford to replace it. This battery is pretty big; does its amp/hour have any effect on whether it'll fry my Arduino?


texts:
In an exercise I have an un-doped silicon I find that p=1.80e+11 ,n=6.60e+10 , should the numbers be more close to each other? (for example in GaAs I find 1.10e+14 and 1.60e+14)?? (also p number of holes and n number of electrons)

T=300 Temperature in K
Nc=2.8*(10^19)  (density of states I guess in English)
Nv=1.04*(10^19)
Eg=1.12  eV Band Gap

Am I missing something?


texts: Why are there 2 clock rates (core vs memory clock) in the GPU?

texts:
I learned at school that the clock rate inside a computer is the signal that keep switching between 0 - 1 (or active - inactive). There's also another delayed clock with the same frequency. These 2 clocks are then AND and OR together, and the out put is the enable-clock and set-clock.

When data is transferred inside the computer, it run from the original-register (inside the processing unit or on RAM) through the bus when the enable-clock is turned on, then set to its destination-register when set-clock = 1. Therefore, I thought that there's only 1 clock speed that run through the entire computer.

Back to the GPU, with its own processing unit and memory. Retailers' product pages always state 2 clock rates for a GPU: core clock and memory clock  (which is several times faster than core clock). Which of those 2 clocks refer to the clock I've described above ? And what is the other clock.


texts: Am I on the right track with the 16F1704?

texts:
I am 100% new to PICs and I know I have a lot to learn. My end goal is to have a DC motor controller that will operate a motor in one direction only and with the push of one button have the motor run at approx 80% (of the nominal speed) and with the push of another button have the motor run at 30% (of the nominal speed).

In addition when the speed changes I would like to acceleration and deceleration of the speed. I have ordered up a PICKIT 4 and one of their Curiosity boards to try on the 16F1704.


texts:
In the Adafruit PCA9685 board schematic, there is a 220 \$\Omega\$ resistor on every PWM output. What is the reason for this resistor? Is this for current limiting with LEDs?
I guess you can skip out these resistors when using MOSFETs?
Is it necessary to use a pull down resistor when driving MOSFETs?
Thank you all for the input!


texts:
I found this formula to calculate the value of the capacitors for a crystal,
C(1,2)=2(CL-Cstray). C1 and C2 will use the same values. How do one choose the Cstray? I read that it ranges between 3pF~5pF.


texts: Help understanding a heating iron circuit component

texts:
I am trying to understand a soldering iron PCB circuit.
I am trying to use a different range circuit for my prototype.
Can someone please elaborate how it is controlling the temperature?
Secondly, I am unable to get any details of D8 (blue component near LED) as C32 written on it.


texts:
Hi i am trying to find a way to determine the range of the drain source resistance (RDS) for a N-JFET only with the parameters given on its datasheet.

I know that the drain source resistance is related to the drain source voltage and the drain current or the source current that is the same, because no current flows through the gate.

This is where things get a bit confusing to me, I found this equation:

I don't remember where I got it from, and I don't even know if it is true, I have this written on some old notes I found.

I know VGS is the rating for the maximum voltage that can be tolerated between the gate and source terminals.

I know VGS(off) is the gate source cut-off voltage, this is the voltage at which the device turns off and starts working on the ohmic region.

I know IDSS os the maximum current that can be handled by the device.

So given the following datasheet:

I assume:

But on the datasheet this parameter indicates the absolute maximum voltage that the device is able to withstand, but I read practically this should be used up to around 60%.

Then VGS(off):

I don't understand how VGS(off) could be lower than VGS max.

And at last IDSS:

I don't really understand how to use the datasheet values to calculate the range of RDS given a range of voltages for VDS.

I plotted RDS against VGS(off) and IDSS, using VGS = -2.5V and the ranges given on the datasheet and got this:


texts: Is body wearable antenna same as directional antenna?

texts:
I find that some product use a body wearable antenna, which is used as a directional antenna.
See pki "direction finder" here using directional antenna:
http://www.pki-electronic.com/products/interception-and-monitoring-systems/gsm-direction-finder/

But I don't understand how such antenna can be directional antenna, it is not directed to anywhere as far as I understand.

Another image of body antenna:
http://www.pharad.com/330-380-mhz-wearable-antenna.html


texts:
I'm using an ST Microelectronics LIS3DSH accelerometer to detect tilt over an extended period of time.  I have the accelerometer securely mounted to a stationary object away from any vibration.  Over the course of two and a half days, I've found the readings slowly change in value. I've made sure it's not a defective accelerometer by performing this experiment multiple times using different accelerometers but the same exact manufacturer and part number.

Below are graphs of the type of drift I see over time.  You'll notice a change of about 0.006G on X, 0.009G on Y and .05G on Z.  Note in the final graph below, the magnitude continually drops over time. I have no idea why this is. It should always be 1 or very close to 1.

Two questions:

Is this a common or known phenomenon with accelerometers?
Could anyone recommend an accelerometer similar to the LIS3DSH where this undesirable behavior would not occur?

Thanks in advance for any information anyone might be able to provide.


texts: What kind of computer do I use to program an atmega?

texts:
What kind of computer (Mac OS X, Ubuntu linux, or Windows) Would I need to compile an program/operating system for an atmega microcontroller? I want the microcontroller to be stand alone at some point (has a battery and does not need to be plugged into a computer to run its tasks)

Thanks


texts: Is this the correct way to wire my transformer?

texts:
I am building a 12 V dual power supply. Since this is the first time I will be using mains (230 V). I would like to make sure that I am not going to burn down my house.

The transformer I want to use is this one in the 2x15 V, 30 VA rated version:

For my power supply I would like to turn this into a 15-0-15 center-tapped transformer by:

Connecting the primary windings together (grey + violet).
Connecting the secondary windings together (yellow + black). This would be the center tap.
Putting a 100 mA fuse before the primary winding (either blue or brown).
Putting a 1 A fuse on each of the secondary windings (orange and red).
Feeding these secondaries into a bridge rectifier, filter caps, and regulators.

Is there anything that I missed, or should be aware of before I get myself electrocuted?


texts:
I simulated a boost converter on LTspice and have measured the steady-state output power to be 80.49 W and the average power drawn out of the input source during steady-state operation of the converter to be 84.7W. Yet when I calculate the efficiency, \$P_{out}/P_{in}\$, I get 0.95, which seems to be incorrect according to a Coursera homework assignment.

Am I missing something? Does the average power consumption of the gate driver matter?


texts: dsPIC30F - Silicon versions (?) and system integration registers

texts:
I see different documentation on the Internet about the dsPIC30F family. Especially I am interested in System Configuration registers.

http://ww1.microchip.com/downloads/en/DeviceDoc/70071E.pdf - document from 2008. It lists the following registers:

FOSC: Oscillator Configuration Register (Note 2) (0xF80000)
FWDT: Watchdog Timer Configuration Register (0xF80002)
FBORPOR: BOR and POR Configuration Register (0xF80004)
FBS: Boot Segment Configuration Register (0xF80006)
FSS: Secure Segment Configuration Register (0xF80008)
FGS: General Segment Configuration Register (0xF8000A)
FICD: In-Circuit Debugger Configuration Register (0xF8000C)

While another document http://ww1.microchip.com/downloads/en/DeviceDoc/70271b.pdf (from 2009) shows different set of registers:

FBS: Boot Code Segment Configuration Register
FGS: General Code Segment Configuration Register
FOSCSEL: Oscillator Source Selection Register
FOSC: Oscillator Selection Configuration Register
FWDT: Watchdog Timer Configuration Register
FPOR: Power-on Reset Configuration Register
FICD: In-Circuit Debugger Configuration Register

The lists themselves and descriptions of the bits (ex the FICD register) differ in significant details.

Both documents do not tell anything about part numbers or silicon revisions they describe.

Does anybody know what doc is better/more accurate? Is there any way to check what config registers are really implemented in the chips that I have in my hands?


texts: Replacing a Li-Ion battery with a capacitor and power supply in a bluetooth speaker

texts:
I have a Philips BT3500 speaker with a dead Lithium Ion battery.
I want to be able to use the speaker without the battery - using just the power supply. It used to work for some time with the usb charger plugged in, but recently the speaker has trouble starting even with the charger connected.
I suspected that the old battery was pulling all the power and thus the speaker didn't have enough to work with. I thus removed the battery completely, and now the speaker works when the charger is connected - which was my goal.
The only problem now is that it shuts down/restarts, when the music is too loud - and I assume that is because there is no battery that can provide a power buffer for sudden spikes in demand.
Hence I am wondering if it would be feasible to use a capacitor for this purpose? How would I go about this?
The Li-Ion battery was a 3.7V 2200mAh cell.


texts: How to document protocol changes across firmware

texts:
I have updated the firmware on my device to accept new commands. How do I make it clear to other developers that the new protocol document is specific to this recent version?

Should I make it clear which commands are reverse compatible in the new protocol doc, or should the other devs be expected to look up the old protocol?

I think putting the applicable firmware version in the title makes the version number seem to apply to the documents itself ie the the read thinks the protocol is at rev 2 instead of apply to rev 2. I also think release notes should be their own doc.


texts:
I'm trying to galvanically isolate a device which is controlled by ethernet (1000base t) via computer. I've been looking and apparently the ethernet standard provides some isolation, but after I connect the cable to my otherwise isolated device to my computer, my multimeter reads short between its ground and earth ground. So clearly it's not isolating enough.

I'm wondering how I should proceed; according to wikipedia, gigabit ethernet is 8-bits, so a digital isolator won't work. Can anyone suggest a kind of chip that would work? They don't seem to make 8 bit digital isolators. In any case, it seems the ethernet signal can go below ground, so I'm not sure opto couplers would be a (direct) option, although I suppose I could bias them before and remove the bias after with a cap? It also seems like they are not fast enough for gigabit ethernet...


texts: Eliminate mains common mode ripple from external power supply with poor isolation

texts:
I've got a number of battery powered devices which require periodic recharging. I'm using notebook chargers to provide for the input voltage and they work fine... most of the time. Occasionally they fail (produce all kind of strange behaviors).

I've isolated the problem to a missing earth connection. Approximately half of the chargers has two pin mains inputs (no earth), while the other half has three pin mains inputs (including earth). The problem only shows when we use the two pin (unearthed) power supplies, or when we purposedly leave the earth pin unconnected on the three pin power supplies.

The three pin devices are Lenovo brand, the others are unbranded. All of the power supplies are switching and give 19V 3A output, since they are intended for notebook charging. Breaking them apart they look similar enough; we see the expected two stage switching (high voltage, transformer, low voltage), linked by a feedback optoisolator AND some capacitor, which is the culprit for leaking a small amount of the mains voltage into the low voltage section. The three pin models have earth connected directly to this capacitor in the low power section, in order -I think- to eliminate the common mode voltage. Which it does... provided earth is connected properly.

In short, the power supplies give the expected output voltage plus a common mode mains voltage (220V here) which is occasionally picked by different sections of our devices producing erratic behavior including internal charger circuitry burning up, li-ion protection FETs jumping in the air, etc. Unfortunately, my device has a rather big metallic case which is connected to circuit ground! My guess is that parts of my device (its case, internal cables, even ground planes) are picking up the other part of the 220V signal, creating potentials in areas that can not be prevented by the usual TVS I/O protection.

I need to deploy these devices to rural areas where there is little chance of having a proper earth connection, so I'd need some strategy to avoid the problem outright.

I'd like a simple hack that I can apply to all my devices to prevent this kind of weakness. That would be the perfect scenario. A less desirable scenario would be something I could do to the power supplies... for instance, why do they have a capacitor connecting the high and low voltage sections? Can I remove it? The least desired solution would be replacing the power supplies entirely for others with proper galvanic isolation: a lot of money! and no warranties that a new one would not have the same problem. Finally, there's no way I could completely cover my devices with shields, since they have RF antennas which could be in part responsible for the mains noise picking.

Thank you in advance.


texts: Low-pass filter on PDM data provides data that does not have a FFT

texts:
I'm trying to convert PDM data into analog form by passing the data through a low-pass filter in Matlab. My approach is fairly simple and matches the answer given in this Electrical Engineering Stack Exchnage thread: How can I convert an audio PDM bitstream into analog form?
However, the result of the filtered PDM data looks like this:

Running an FFT doesnt work on this analog data. What could I be doing wrong?
I've tried a butter filter (various orders) and Cheby 2 filter and elliptic as well. Here's what my FFT chart looks like for reference:


texts:
I have just started designing the embedded systems. While designing the CPU and thinking from the reliability point of view I actually had few curiosities

For the unused pins which are tied up to Vcc using a pull up resistor - Lets say there is and fault and we have two conditions a) that is in floating state b) if its short then tied directly to Vcc. I would like to know the effect of both this conditions on the working of CPU and system?

Similarly for the unused pins which are tied up to GND using a pull down resistor - Lets say there is and fault and we have two conditions a) that is in floating state b) if its short then tied directly to GND. I would like to know the effect of both this conditions on the working of CPU and system?

I am using SM320F28335PTPMEP microcontroller for my purpose.


texts: non-linear load (rectifier) and power factor

texts:
I read that power factor shows how much there is the apparent power, which circulates between power lines and the load and does nothing but heats up the transmission lines and transformers in them. They say that this is due to the current being out of phase with voltage. Particularly, power flows out of the load when voltage is positive but current is negative.
Also, I see that diode rectifier conducts only at the short moments of peak voltage, when input voltage exeeds the load voltage (rectifiers have an output capacitor = load voltage). So, all the power is consumed during these short bursts. I have read one an article saying that people do not understand anything and the whole problem is not power factor but these bursts that overload the transformers in power lines (it is not allowed to make large currents in transformers because of danger of magnetization loss). But, when you consume all power during very tiny fraction of the sine, huge current happens. Obviously, the current is not proportional to the voltage as it should in the reference (resistor) load with power factor of 1. But, I do not see any negative power here! The rectifier precludes having positive input voltage and negative current. All current is positive under peak positive voltage. So, how does the non-linear load produce the apparent power?
In other words, Wikipedia says
http://en.wikipedia.org/wiki/Switched-mode_power_supply#Power_factor

Simple off-line switched mode power supplies incorporate a simple full-wave rectifier connected to a large energy storing capacitor. Such SMPSs draw current from the AC line in short pulses when the mains instantaneous voltage exceeds the voltage across this capacitor. During the remaining portion of the AC cycle the capacitor provides energy to the power supply.
As a result, the input current of such basic switched mode power supplies has high harmonic content and relatively low power factor.

How do they conclude that harmonic content produces the low power factor? Where the apparent power comes from?
I understand that current has harmonics (frequency components) which means that it oscillates forth and back while voltage remains of single polarity. It might be that these high-frequency oscillations of current produce the apparent power. However, the net flow is still positive, the current still flows only in one direction, corresponding to the voltage polarity and oscillations do not make it flowing in opposite direction to cause the apparent power.


texts: Should you not go above max VGS for a Nmos?

texts:
I wanted to switch a relay with a raspberry zero, which uses 3.3v,
after looking at my 16 years old electronic engineering notes (I'm in IT now), I moderatly re-understood how nmos works (controlled by tension only, once activated is equivalent to a resistor, RDsOn).

They are tension operated not current operated so less math to do, that is why I choose them.
After some quick googling I found that some people use IRLZ34N.

So I did this :

In order to switch on a waterpump for 15 seconds each day.
It has been working for 2 months now.

My question is, why doesn't it blow up? since I exceeded Max VGS.

Thanks.


texts: Instrumentation Amp design for breaking ground loops between systems

texts:
We're in the midst of designing a device for measuring analog signals and have been testing our initial prototype. We had a single-ended gain stage before the ADC, but due to the connections in the rest of the  system we are experiencing ground loops through the signal cable. These are causing offsets and throwing a heap of noise onto the signal.
Our initial solution has been to use an instrumentation amp as a pseudo-diff amp with a pulldown on the inverting input, as shown below.

I understand R3 prevents the inputs from floating when no device is connected while allowing the GND of the two devices to be at different potentials. I'm having a hard time figuring out why the value is so low though (the design is recycled from an older device). The signal we're interested goes down to a few mV and offsets of 0.1mV are acceptable. With input bias currents in the nA range for IN-amps I would think R3 could be much larger.
This comes about because there is a use-case for having numerous (10-20) of these amplifiers in parallel. With 10-20 R3's in parallel the impedance between the two system grounds will drop to 5-10 Ohm and the 'break' in the ground loop will be much less effective.
What might be the reason for keeping R3 low? I'm hoping to optimize it for some larger value but first need to understand the trade-offs.


texts:
This question may also be asked in physics stackexchange, but I'll try my luck first here. I want to set up a water temperature sensor system. My temperature sensor will most probably be DHT22 due to its availability and its good performance with ESP8266.

The problem is DHT22 is not water resistant. Three solutions came to my mind:

Coating the DHT22 with hot silicone gun. Hot silicone shouldn't really damage an electronic devices, supposedly to operate perfectly between -10 to 85 degrees celcius. However, it is a lumpy solution at best and there is no guarantee water won't sneak in, in some time.
Making a probe out of metal and fit it to DHT22. II'll dip the probe into water and it will have  a very large surface area like a large sphere, inside water. The probe and DHT22 will be in contact with a thermal gel. I can then coat the DHT22 with tape or hot silicone to avoid any damage due to splashing water. I can then calibrate the DHT22 reading with actual water temperature to get rid of any bias due to it being out of water. I can even coat the DHT22 with polystyrene to reduce bias from air temprature.
Making a metal box and fit the DHT22 in it and dip it into water. Now DHT22 will be in water. Again, it will be in contact with metal via a thermal gel. I can then screw the box, tape it with water resistant tape and then hot silicone over the tape. This time, it will again be lumpy but I'll have time to change the once a month or so and water resistant tape will offer extra resistance against small leaks.

I wonder which one, or some other solution, would be best for such a task.


texts: how to reduce current without changing voltage?

texts: In my car there is a  charger it is producing 5v/2amps,but there is a clock in my car, this clock is connected to this car charger it need only 5v/500ma,how can i reduce the current to this clock?


texts: Can anyone identify this white board component in an electronic air filter?

texts: Electronic air filter circuit board component?


texts: Some example models that are included in the Simulink library, there are some variables that their value is not visible. For instance, in the model power_PVarray_grid_det the sample time of the powergui is defined as Ts_Power. I can not figure out the value of this variable. Is there a way to find these hidden variables, have access to them and change their value?