texts: Reversing Direction of a DC Motor with Delay

texts:
I am making a kinetic sculpture and the movement of it requires a reciprocating motion. I have made the designed such that a dc motor powers the movement of the sculpture, and a rotating beam that hits a DPDT switch. What I want is that when the beam hits the DPDT switch, it will reverse the direction of the motor, and it will go until the beam hits the DPDT switch from the other side. The mechanical design is all fine, but I have encountered a problem. When the beam hits the DPDT switch, it momentarily switches the motor off, and sometimes, the inertia of the motor is not enough to push it further so it reverses the switch.

I am not the best at electronics, but I have tried putting a bipolar capacitor across the motor:

simulate this circuit – Schematic created using CircuitLab

The idea is to have the capacitor store a residual voltage that will power the motor for a few moment when the DPDT switch is at the off/middle position; however, it did not seem to work. I do not know if this is because of the fact that the polarity is reversed. If that is the case, I might try putting two series of diode and capacitor in parallel, each facing the other direction:

simulate this circuit

I have also bought a 555 IC but I do not know how to incorporate it with a reversing polarity like this.

Any help with the circuit design would be much appreciated. The motor runs on 9V, and I need the motor to run when it is disconnected from the switch for approximately 0.5 to 1 second. I also prefer the circuit to be small since I want the circuit to fit inside the base of the kinetic sculpture.


texts: If I step up 9V to 12V with a boost converter, what happens when the input goes to 12V?

texts:
I want to use either a 9 V or 12 V power supply. If the input is 9 V, I want to step it up to 12 V with a boost converter. But if the input is 12 V will the output still be 12 V or will it be boosted to 15 V or so.

The boost converter is the XL6009.


texts:
I found this circuit on internet looking for a "ON when dark/OFF when light" circuit:

When I mounted it, it worked as expected, the only problem is that voltage between A and B is 8.71v instead of 12v.

What can I do to get the 12v between A and B?


texts: Op-amp driving mosfet changes hystheresis thresholds?

texts:
I have a non inverting push-pull output op-amp with additional hysteresis (Maxim MAX9015) that should drive an N-Mosfet.

I calculated the resistor values for the op-amp(R5, R6, R7) for an older version of the circuit, when there was no mosfet yet and the "OUT" of the op-amp was going directly to an other IC.

Now I am not sure if the resistors that I have to put for the mosfet, R8 and R9, are going to modify my hysteresis thresholds. Do I need somehow to isolate the hysteresis part from the mosfet?

See part of the circuit below.

Thanks in advance for your help.
Cheers


texts:
I am using this Differential In/Out Opamp circuit as ADC driver and to provide some gain(G=6.4).

The component values are R53,R52=100, C28, C27=1.1uF, R56= 1K, R57=open, R55,R54= 2K7, U6=OPA2211.

At ADC input I have simple RC filter.

Component Values are C10,C11=Open, C7=1uF, R26, R27=100.

Now the problem I am facing is My opamp output seems to have some noise like this,

But as I expanded the time scale I saw this,

I don't understand where this is coming from, I powered my ckt with linear supply but saw no improvement. Sensor connected to OPamp Inputs is a wheatstone bridge Pressure sensor and it looks cleans. kindly help me.

Edit: I am using MCP1640 Boost converter to get 5v from 1 cell Liion.
And using MCP1702 to get 3.3 V from 5V.
I thought it was switching noise but I also tried with Linear supply.


texts: My phone has a battery that supposedly contains around 3000mAh. It's also horribly hungry, and when in heavy use can easily eat the battery in under 3 hours. My question is about the fact that discharging a 3000mAh battery in 3 hours means sourcing a current of 1A continuously for that period of time. 1A is enough to melt wires considerably thicker than those on the circuitboard inside my phone. Why is my phone still working?


texts: How is transfer impedance of a cable different from its characterstic impedance

texts: i have been given a task to measure the impedance of a coaxial cable. i was doing some literature study and i came across two terms : transfer impedance and characterstic impedance. i am not able to understand the diference between these two terms for a cable.


texts:
I'm currently reading through Introduction to Computing Systems: From Bits & Gates to C & Beyond and I'm a bit confused about the outputs of this OR gate (which is not an OR gate):

And here is the provided text:

I guess I could imagine, that there is something like "voltage drop" in the case when either or both of the inputs A, B are 1.2 volts. That is, the nMOS transistors connected in parallel act like a "closed" switch and they will be "on", but because of the "transmission voltage", the output at C will be 1.2V (from the source) - 0.5V (the "voltage drop") = 0.7V.
I'm not even sure if this is the correct interpretation, but so far the book provided only this kind of abstraction as "closed" or "open" switch.
Why I don't really understand is that, when the both inputs A and B are at 0 volts, how come the output is 1.0 volts? If the input is 0V, then both nMOS transistors connected in parallel in the upper part of the diagram will be in the "off" state, meaning that they will behave like an "open switch". No current will pass through them. In the case of pMOS transistors, if the input is 0V, they should be "on" and act like "closed switch", so that means there will be path from C to the ground. How come the output is 1.0V?
If I may ask so stupidly: pMOS is connected to the ground, on the input there is 0V, and the source is "disconnected" (since the nMOS will act as open switch), how come there is "magically" 1.0V at the output?
Thank you all very much!


texts:
I designed a circuit that is similar to the circuit on the picture below. The main difference in my design is that I am using a 3V battery and more LEDs.

I am using UNPOLARISED capacitors because I am aware of the oscillating voltages on the two capacitors. I also manufactured the PCB and it works like a charm.

Because unpolarised capacitors are large, expensive and I found only THT (I want SMD), I am interested in using ELECTROLYTIC POLARISED capacitors - and assuming that it is not dangerous since it is a low voltage circuit (3V battery is used, so the reverse voltage on the cap should be max around 1V).

I have already tried the circuit with polarised electrolytic capacitors (specifications 330uF, 16V) and it works just fine, and the capacitors are cold, so it seems safe. But I would like a comment from more experience guys before I make 20 PCBs and than realize that after 5 days the capacitors cause a fire or something...

Thanks!


texts: Is it possible to use conditional statements to modify parameters at compile time in Verilog?

texts:
This question explains how to use Verilog parameters to combine constants from different modules at compile time. I am wondering if it is also possible to use conditional statements to modify parameter values at compile time.

Specifically, if the calculated total of the parameter values exceeds some maxLength, I want the parameter to 'wrap around' maxLength and be left with the remainder instead.

Pseudo-code example:

module toplevel {
    defparam myPole.offset = 95;

    pole myPole();
}

module pole {
    parameter offset = 0; // default value, overwritten by 95

    localparam x = 1;
    localparam y = 2;
    localparam z = 3;
    localparam maxLength = 100;

    localparam transitionConst = x + y + z + offset; // total is 101, this works as expected

    if(transitionConst > maxLength){
        transitionConst = transistionConst - maxLength;
    } // transitionConst should wrap around 100, and be left with 1
}

I looked at compiler directive tutorials at asic-world.com and TestBench.in, but the only if statements they describe are ifdefs. So, I suspect that Verilog does not support generic compile-time conditional statements. Is there a different approach I could use to accomplish this?

(P.S. I've seen Verilog Q&A on both EE.SE as well as StackOverflow. Which is the more appropriate community?)


texts: Can 300 ADC damage a battery wire (4AWG) rated for 60VDC, 150ADC if 300ADC @5VDC is passed for 2 seconds?

texts:
I would like to know if there is a risk of damaging a 4AWG Battery wire (worst case fire hazard) which is rated for 60V, 150ADC if 300Amps @5VDC is passed for only 2 seconds? I am working on a test solution that will supply the UUT with 300 Amps in the production environment and current will be routed through the cables for 2 seconds max, at least 10 times per UUT test run. The situation is similar to starting a car as the starter motor takes a lot of current from the car battery.
The Length of the battery wires is going to be less than 10ft.
Each unit is expected to take 5 minutes however, the high current application is not expected to last more than 15 seconds overall. The current will be applied as a step response for a maximum of 2 seconds.
The test will be conducted at ambient temperature.
The cable has polyvinylchloride (PVC) type insulation.


texts: Measuring 0.1mm accuracy of very short distance (< 5 or 10mm)

texts:
I need to measure a very short distance (< 5 or 10mm) of a rotating shaft which will eventually move to one side by a few mm.
I would connect this to an Arduino or similar.
Could someone recommend a cheap option and a more professional option for the sensor?


texts: Switches and functions of microwave oven unresponsive on cold start

texts:
I have an old microwave oven which performs most of its functions, considering its age.
There is a slight problem that the switches go unresponsive and the LCD display fails to operate correctly if I do not use it for a couple of days continuously. The switches become responsive once I plug it in for half an hour or an hour. (And I don't mean operate it. Just plug it to the mains and turn on the supply.)
Why does it require such a plugged-in time to warm-up? Reminds me of the cold blooded animals that need to warm themselves in the sun for some time before they can become fully operational. Why do the electronics and the circuits inside the appliance need such a warm-up before it can operate properly?


texts:
In Jal, it's possible to do something like this:

var word the_var = 0x1234
var byte the_array[2] at the_var;

Now you can easily access the bytes of the word the_var with the_array[0] (0x34) and the_array[1] (0x12). Can something similar be done with the C18 compiler?

I have an unsigned int the_var and want to access the separate chars in that variable using an array.


texts: When shipping electronic components, can I reduce static by using dryer sheets or sprays?

texts: Can I use dryer sheets, or anti-static spray on polyurethane foam to reduce static between the foam and the polypropylene container the foam is in? I need to ship some ESD sensitive electronics overseas by air freight. The most sensitive electronics are in ESD bags, then placed in custom-cut holes in the foam. But it isn't feasible to enclose all the electronics in ESD bags. I wanted to further reduce static by using anti-static foam, but that isn't available in my area and I would have to wait weeks to have it delivered. So do you a reasonable substitute could be lining the inside of the container with anti-static dryer sheets (then putting in the foam), or spraying the polyurethane foam with anti-static spray (e.g. Downy Wrinkle Releaser)?


texts: Circuit with switch - express the current for different times

texts:
Consider the circuit below consisting out of a capacitor C and two identical resistors R. For \$t<0\$ the switch is open and the capacitor is uncharged. At \$t=0\$ switch is shut and the circuit is connected to the voltage source with constant voltage U.

  a) What's the total current in the circuit immediately after the switch is shut? What's the charge of the capacitor and the total current after a very long time?

  b) Determine for \$t>0\$ the total current in the circuit and the charge of the capacitor as a function of time by setting up a suitable differential equation and solving it.

I'm practicing for my exam in physics and I have always been weak concerning even the easiest circuits and I found this one in my textbook.

Here are my thoughts so far:

a) I suppose that in this type of circuit the current and the voltage are in phase, meaning that immediately after the switch is shut the current should be \$I=0\$?

But I don't seem to find an approach getting expressions for the current and the charge after a very long time. Can't I just assume that the capacitor will be fully charged, meaning \$Q=C\cdot U\$? About the current: Since at every part of the circuit there should be a different current, meaning at $R$ the current should be \$I_R=\frac{U}{R}\$ and I was thinking that since \$Q=C\cdot U\$ and the time derivative of \$Q\$ is \$I\$ and since \$U\$ is constant, does that mean that the current is \$0\$? Seems kind of unlikely.

b) I'm kind of lost here. I'm supposed to set up a differential equation which then would give me a function with which I can find \$Q\$ and \$I\$ at certain points?

I would appreciate any help. I seriously need to get better with circuits.


texts: Adding an adjustable constant current option to a LM5175 circuit

texts:
Disclaimer: I'm no electronics engineer and I have no experience in this kind of circuit! I do occasionally design simple analog circuits and PCBs, barely messing with opamps.
Context:
I'm about to build an open source general purpose modular DC UPS. Meaning, it will switch between a DC input and a battery accordingly, charge the battery and regulate the battery's voltage. It will be MCU monitored and it will be able to talk to a host, if wanted. It's modular because the input voltage and current, the output voltage and current and the type of battery are meant to be arbitrary and the user may re-design, populate or configure in whatever way he needs. This circuit is meant to be as robust and efficient as possible (limited by me design skills), as it will be on for long periods.
The question is regarding the battery charging circuitry.
I'll be using the LM5175. My design is highly based on its typical application design (p. 20, fig. 24) and I'm using the webench to adjust it to my needs.
Here is the schematic so far. This is incomplete and the values are not yet chosen.

I want to implemente a smart, but not so smart, charger, using CC/CV method for lead-acid or lithium batteries. All battery's safety features should be handled at battery side.
The CV is easily configurable my adjusting R2 and R3 but now I need the CC.
What I know I can do:

use the internal current limit circuit (ISNS+ and ISNS- pins);
messing the feedback (FB pin) so it can act as both CV and CC, whichever happens first;
anything else?

My main concern here is the stability of the system. I mean, I don't really care if it charges the battery at 0.9A or 1.1A. But whatever value the user got it adjusted, it should stay there. Also, I assume the user may use a dummy load, short the output or measure some specific TP to set the CC limit.
Option 1.
I believe this would be the correct way to go but I have no idea how to make this work. Usually the pins ISNS+ and ISNS- are connected across R1 (current shunt). Obviously this shut cannot be a trimmer.
These pins are connect inside to an amplifier and to a comparator such that when voltage across the current shunt resistor is higher than 45 mV the IC limits the output current, by lowering the output voltage. The functional block diagram is on p.13.
Question: is there a way I could add some circuit here so I could tune current with a trimmer between around 0.5A and, say 2A? How?
EDIT:
I came with this solution based on GreatScott's idea and adapted to my problem. However I have no idea if it makes sense to use the internal comparator like this.

Option 2.
I thought I could implement something like some Chinese designed switched mode regulator boards do. I have some idea that, by visual inspection, it looks like they mix the voltage feedback with a current shunt resistor and a trimmer. An amplifier is used to amplify the voltage across the shunt and a comparator to compare it to the trimmer.
GreatScott added this CC circuit to a board which only had a CV trimmer. Here is the whole project and the schematic regarding this addition:

Question: if this a good option to my problem, will this work here? Can you please give some help adjusting it to here?
Option 3.
Anything else I could do you remember? I found what looks to be two other approaches to this problem.
I found that the TI's reference design around LM5175 has a CC setting to 11A but it's using something more around ISNS+ and ISNS- pins which I don't understand. The schematic is here.
There is this thread on e2e where it looks someone is trying to do the same using the COMP pin. I also don't understand the idea.
Thank you for your help!


texts:
I feel really dumb asking this, but why is a resistor always a drop in loop analysis?

For instance, in the picture the KVL #2 equations are the correct ones, but why? Shouldn't the resistors keep the sign convention you assign to it with the first equation?


texts:
I have to say first of all that I'm not an electronics expert, but I have some basic knowledge.

I want to connect the ADS1115 circuit to my uC using I2C, and measure the "battery level". My problem comes with the powering: ADS1115 is powered by the uC and because of that when the uC turns off it does too, but obviously the battery I'm trying to measure doesn't and keeps applying energy to ADS1115 which is of course not desireable and could burn it.

Of course I can use a relay and cut the connection between ADS and battery but I'm wondering if can make up something using 2N2222 transistor that I already have.

I'm thinking on something like the foloowing but I'm almost sure that it will not work.

simulate this circuit – Schematic created using CircuitLab

Reading through my own post I have to say that is really confused, let try to explain my porpouse better and adding some extra info that could help.
I have some circuits in charge of stabilize the battery power, output of this circuit is connnected to the uC and ADC is sharing this output (that is what I mean when I said power by the uC and not using a PWM, GPIO or another uC output, I know not clearily explained). I think that this part is clear now, lets continue with my problem, when power supply is off, the previously mentioned output is not suppling energy, but the ADC is still connected to the battery and this cause the ADC to get hot and may end burned, because of that I need a way to cut the connection between ADC and battery when power supply is off, I was trying to avoid using relays and use 2n2222 because I already have a bunch of it and I was thinking on something like the picture above, I know it won't work but hopefully some modifications over it could get it working.

Any ideas? What can/should I do?


texts:
I am working with VFD (CT-2002ES-A75). It shows output frequancy on it's seven segment display. However It has a parameter(Cd46 on page 27 in the manual) for display the current RPM of the motor.

For display the current RPM need to enter some factor as parameter input.
How to calculate that scaling factor for my motor?

This is the nameplate of the motor that controlled by the VFD.
Motor is connected as star system. Working on 230VAC supply.


texts:
I am designing a circuit for maintaining constant voltage for an unknown load and measuring current through R5. Following is image for reference:

I had done some simulations on Tina before making the PCB with the components. The simulation worked as expected. After that I selected the OPA197 to drive the load and LMP7702 to give feedback to the control op-amp.
Now I have assembled the PCB. For testing purpose I have shorted the 100   ohm resistor and input of LMP7702.
When I apply for example 1V at the Input_Signal, Vout comes out ~536mV and output of LMP7702 comes at around ~884mV. This should obviously not happen as the LMP7702 is acting as buffer.
I have also tested both op-amps with +-5V supply and similar results are observed. I have changed the op-amps and tested again but same results.
I am not sure what to check. Power and input signals are within specs as per the datasheet. I am not sure how to troubleshoot this problem. Any suggestion what the fault maybe and what to check?


texts: Getting bottom row of black boxes with LCD Display on atmega32 MCU?

texts:
I need some help with this, I am a completely new to programing MCU's but I am trying my best to get this working and I could relay use some help. I am using the Sparkfun Basic 16x2 Character LCD along with a atmega32 MCU. Basically, the bottom row is full with black boxes and I cannot figure out why!
Here is my code:
/*
 * LCD.c
 *
 * Created: 11/29/2014 5:12:36 PM
 *  Author: John August
 */

#define F_CPU 16000000UL // 16 MHz clock speed
#include <avr/io.h>
#include <util/delay.h>

// Define LCD I/O Pins (8 Bit Mode)
#define LCD_PORT PORTD
#define LCD_PORT_DDR DDRD

// Define LCD Command Pins
#define LCD_CMD PORTC
#define LCD_CMD_DDR DDRC
#define RS PINC7 // Register Select
#define RW PINC6 // Read = 1 and Write = 0
#define EN PINC5 // Enable

void isBusy_LCD(void);
void Awaken_LCD(void);
void Send_CMD (unsigned char command);
void Send_CHAR (unsigned char character);

int main(void)
{
_delay_ms(50);
LCD_CMD_DDR |= 1<<RS | 1<<RW | EN<<1;
_delay_ms(50);

Send_CMD(0x01);  // Clear the screen 0x01 = 00000001
_delay_ms(50);
Send_CMD(0x38); // Put LCD in 8-bit mode
_delay_us(100);
Send_CMD(0b00001110); // Control Cursor
_delay_us(50);
Send_CHAR(0x41); // Display "A"

while(1)
{
}
}

// Check if the LCD is busy
void isBusy_LCD(void)
{
LCD_PORT_DDR = 0;
LCD_CMD |= 1<<RW;
LCD_CMD &= ~1<<RS;

while(LCD_PORT >= 0x80) //D7 is "HIGH" when busy, D7=0b1000000 (check read busy flag)
{
    Awaken_LCD();
}

LCD_PORT_DDR = 0xFF; // 0xFF = 0b11111111
}

void Awaken_LCD(void)
{
LCD_CMD |= 1<< EN;
asm volatile ("nop"); // asm = Inline low level assembler
asm volatile ("nop"); // "nop" = NoOperation (for delay)
LCD_CMD &= ~1<<EN;
}

// Send a command to the LCD
void Send_CMD (unsigned char command)
{
isBusy_LCD();
LCD_PORT = command;
LCD_CMD &= ~(1<<RW); // Set R/W to 0 (write)
LCD_CMD &= ~(1<<EN);  // Set Enable to 0
Awaken_LCD();
LCD_PORT = 0;
}

void Send_CHAR (unsigned char character)
{
isBusy_LCD();
LCD_PORT = character;
LCD_CMD &= ~(1<<RW);  // Set R/W to 0 (write)
LCD_CMD |=  (1<<RS);  // Set Enable to 1
Awaken_LCD();
LCD_PORT = 0;
}

I messed around with the V0 contrast pin, but adjustments will either turn the black boxes "transparent" or turn the whole screen full of black boxes. I think this is a code issue.
Here is a picture of the circuit:

Basically it follows this schematic. With the exception that I am using port C for RS, RW, and Enable. Port D is for DB0 through DB7 of the LCD.
AVR        LCD
PC7-------> RS
PC6-------> RW
PC5-------> EN

PD0-------> DB0
PD1-------> DB1
PD2-------> DB2
PD3-------> DB3
PD4-------> DB4
PD5-------> DB5
PD6-------> DB6
PD7-------> DB7


texts: How can I protect my amplifier, MCU, and laptop from damage in my application circuit?

texts:
I am trying to integrate a few devices for a laser stabilization system. I have a tentative circuit diagram that I'm asking for more expert guidance in implementing. I am using an MX200 from PiezoDrive, a Teensy 3.6, my laptop, and a Meanwell 150W 24V Supply. I feel as though it should be straightforward, but I am relatively inexperienced and have broken an amplifier by accident. After plugging in a speaker to my laptop to simulate vibration, it became earth referenced, and after probing with an earthed oscilloscope I most likely destroyed the amp (rookie mistake, I know). I have purchased a USB Isolator for my speaker and audio interface, which should fix that problem.

I follow the most basic setup posted on PiezoDrive's website, and my load is this mirror mount, with 350nF capacitance.
Thanks, and any advice and/or questions would be appreciated. Here is the block diagram and basic application circuit for the amplifier (bimorph load not applicable).


texts:
I am going to choose an op-amp as a buffer for my pH sensor. How much slew rate of an op-amp is important in choosing my op-amp?

The slew rate of op-amp that I search range from 0.02 V/µs to 12 V/µs.


texts: Serial resistance for SPI bus (33 ohms, 50 ohms....)

texts:
I have a question about SPI communication. I learnt that we should place a 33 or 50 ohms serial resistance in MOSI/MISO lines for the adaption, and overshot. My question is how could we find these values (33 or 50 ohms)?

I want to calculate it. I have a little knowledge in transmission line, but I never see the proof.

Could you say how to find it?


texts:
I'm pretty new to electronics. I've however recently used mechanical and solid state relays successfully. Now, I am just started trying to use latching relays. I am currently trying to create a set up whereby my raspberry pi would trigger the latching relay to both set and reset positions, thereby switching the main circuit on and off. However, I am encountering some problems as the relay does not seem to latch when the appropriate current is applied to set and reset coils. The schematic of my relay is:

The datasheet can be found here: http://docs-asia.electrocomponents.com/webdocs/1398/0900766b8139805d.pdf

Pins 1 and 6 will be connected to GPIO pins of my raspberry pi, while the main circuit that will be switched on and off will be connected across pin 10 and 3. Since I read that the operate voltage of a latching relay is 3.75V (based on nominal voltage of 5V), I used an adjustable voltage regulator to convert my 9V power supply to around 3.75V. I applied this 3.75V voltage to pins 1 and 6, one at a time, and the GND of pins 12 and 7 to the emitter pin of my transistor which drains to my raspberry pi GND. I also applied 9V across pins 10 and 3, where pin 3 leads to GND of the circuit. When I ran my looping raspberry pi script to cease the voltage across pins 12 and 1, I verified with my multimeter that the voltage dropped to zero from around 3.75V before rising back up again after a few seconds. I expected that current will pass from pin 10 to pin 3. However, the latching relay did not work and I confirmed with my multimeter that no current passed from pin 10 to 3 when set voltage is applied, and I did not hear any expected clicking noise during operation. I then activated the reset coil instead and find that there is still no current passing from pin 10 to 3, or any latching sounds produced. Could any advise me on this issue?

I've also drew a schematic as well. The schematic for the relay is not the exact one I used, since there are limited options on the circuit lab sketch, but this diagram should otherwise be about the same as my current set up with one GPIO pin used.

simulate this circuit – Schematic created using CircuitLab


texts: Wrong data displayed from UART connection

texts:
I have trouble displaying a certain hex string on an LCD. The hex string comes from a external display device that communicates with a serial display.
With the oscilloscope, the data from the display looks like this: 5A A5 20 81 00 80 28.

I have an USB-RS232 connector like in this datasheet:
https://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_US232R-10_R-100-500.pdf
With this cable, I could see the correct hex data in the RealTerm serial terminal on my PC.
However, when I want to display the hex string on a LCD display with a PIC microcontroller, to test if the connection is correct, I get the following hex string: "58d5eefdfdd7 0a9..." (I'm not sure if more data is following, because the LCD doens't have more space to display).
The display wires are connected directly to the PCB with the PIC and the LCD.
I use MCC. The baud rate of the PIC matches the display (9600). I get the same result regardless of the choosen data polarity in MCC(inverted or noninverted). I think that is all the relevant settings.
I use the following code fragment:
while (1)
{
    if(EUSART1_is_rx_ready())
    {
        volatile uint8_t tmp = EUSART1_Read();
        char hex[2];
        sprintf(hex, "%2x", tmp);
        Lcd_Write_String(hex);
    }
}

So I get data coming from the display. Those 58 and D5 seem to be related to 5A and A5. It is as if there is some pattern to the errors, but I fail to see it.


texts: Possible to take 110 down to safe level to run LEDs?

texts: I'm working on a lamp project that I found online. It's a DIY lamp with a whiskey bottle for the base. The project itself just uses a standard 110V plug that goes right in to the wall, but I wanted to modify this just a little to include some LED's and maybe a timer chip or something, and I was wondering what's the correct way (or if it's even safe / possible) to run a smaller dc circuit somehow off of power taken from the 110 AC? How would you go about doing something like that? I imagine I'd need some kind of rectifier?


texts: SPI: effective payload throughput per clock tick?

texts:
Let's say I'm clocking a SPI bus at 30 MHz.

What payload throughput can I actually expect? 30 Mbps, or less?

(E.g. are high overheads imposed by pauses, control packets, packet headers, packet checksums, etc? SPI noob here.)


texts: How to calculate RMS power of an offsetted sine wave

texts:
I know when it is centered at 0, Vpeak/sqrt(2) gives the RMS.

When I do FFT on LTspice, it gives a peak at -17dB which is equal to 0.141254

On the FFT page, program says that it shows RMS values. But, I don't think the RMS of this wave is 0.14 W. You are also welcome to answer for this question involving LTspice.

However, main question is : I actually don't think this question is specific to power calculation, anyway, what is the method to calculate RMS of such sine waves?


texts: Why Are Ethernet/RJ45 Sockets Magnetically Coupled?

texts: As the title says really, why do ethernet sockets need to be mag-coupled? I have a basic understanding of electronics, but mostly, I can't figure out the right search terms to google this properly.


texts:
I am working with relays similar to this:

The mounting tabs along the bottom surface (circled red in the photo) have what look to be scoring marks. The one I have in front of me has several more of these on the underside as well. Each mark is present on the top & bottom surfaces.

Is it correct to break off the tabs at the scoring lines that aren't being used / are in the way?

Or are those metal indentations for some other purpose?

Edit: Just some more detail - these are HVAC fan relays. I'm using them for exactly that purpose but not as a replacement part; there is no existing mounting location to compare against.


texts: Alternative to relay (switching 12V with 12V accesory in car)

texts: What are the other alternatives to relay would be for switching 12V battery power rail with accesory (ignition) power? I'm trying to find an alternative, because the relay is too big for my application, I'm looking for something what's is more compact than the relay. Power load is about 150mA. I can't connect my application directly to accesory, because max rated power load for accesory is 150mA.


texts: Stereo Microphone Output into Mono Input

texts:
I'm not at all familiar with microphones, so sorry if this is a very simple issue. I have a Sony XAV-AX1000 headunit in my car and the standard microphone included with the kit. It's very similar to this cheap unit and has a simple 3.5mm TS output. I'm trying to replace it with a Rode Video Micro, a microphone with a 3.5mm TRS output in what the datasheet calls 'dual mono'. When I plug the Rode microphone into the headunit I get no microphone input unless I play with the positioning very lightly and leave it maybe 2mm out from being totally plugged in. It's crystal clear in that position.

How do I fix this and what portions of the barrel do you suspect are connected in this position? Would this work?


texts: What is sense terminal/pin in differential amplifiers?

texts:
I sometimes encounter a connection terminal called AISENSE in some data acquisition boards. I also see a pin called SENSE in diff. and Instrumentation amplifiers.

An example(look at the pin called SENSE at the upper right corner):

Another example:

1-) What is the SENSE pin shown in the circuits above and what is it used for?

2-) Is SENSE same thing with AISENSE?


texts:
With regards to RF directional couplers, I'm trying to understand the precise usage/definition of the "directivity" specification especially with its relationship to "coupling factor".

The "coupling factor" is seemingly straightforward.  A 20dB coupling factor for a device means the coupled port will output a signal that is 20dB lower than the signal presented at the device's input port. (This would be useful for, say, monitoring the characteristics of the input signal)

The "directivity" seems to be an indication of how much signal will come out of that same coupled port relative to signals present at the device's output port.  So a device with a 20dB directivity spec means that the coupled port would have a signal 20dB down from any signal coming into the output port.

These example specs are from http://www.minicircuits.com/pdfs/ZFDC-20-33+.pdf. Note that the device's "directivity" spec and "coupling factor" spec are nominally identical.

So just how "directional" is a coupler that allows the same relative signal (-20dB) at the coupled port? It seems not "very".

-Mike


texts: Depletion Mosfet as current source to power load

texts:
I came acros the following application note for a Depletion Mosfet (https://www.infineon.com/dgdl/Infineon-Application_Note_Applications_for_Depletion_MOSFETs-AN-v01_00-EN.pdf) and i got intrigued.

In the above image, the depletion mosfet is being used as a current source to power a load with a constant current (the best it can, since this type of current source as some oscilations in the output current - from what i read).

My question is, how can you calculate the power that is being dissipated in the depletion mosfet (couldn't find the answer from my search)? It's Vds*Ids?

The objective would be to use the depletion mosfet + a power resistor to dissipate the energy from a set of capacitors (constant current discharge). The objective is that the depletion mosfet dissipates the less possible and that the resistor (load) dissipates the energy.

Best regards


texts: Most efficient adder structure for adding many terms

texts:
What is the most efficient digital adder circuitry for adding up more than three terms?
The question stems from my effort to implement the multiple term addition required for SHA256 on an FPGA in a single clock cycle. In SHA256 the critical path is the addition of several terms for the RegA path.
The synthesis tool was infering a tree of carry ripple adders which did not meet timing. I went on to implement a carry save adder tree which I found to be much faster and helped me meet my required timing.
Is there an architecture which is faster for adding multiple terms? I saw in my research Dadda and Wallace trees, do these apply to adders? Or, is there some other architecture I may have missed in my research?


texts: Are there any SOT-23 BJT's with swapped Base and Emitter pins?

texts:
The standard NPN BJT in SOT-23 package has the following arrangement of pins:

Do you know of any transistor that has pins 1 and 2 reversed? So that 2 is the base while 1 is the emitter (Doesn't matter if NPN or PNP, i.e. Emitter or Collector). I truly can't seem to find such a device.


texts:
I am working on a project that needs a custom camera capable of MJPG over WIFI. The project is a solar powered camera on a track the tracks objects walking past. The device should transmit the images back to the computer that controls the device so that it can process them and send instructions back to the device.

Unfortunately due to mounting/size constraints I am unable to just rip the sensor board out of a cheap security camera (trust me, I would if I could!). This leaves me with building my own.

I started the design phase, however I can not seem to find the parts that I need, or what those parts may be called.

From my limited understanding (note that I have no experience with image processing) The block diagram should look like this:

simulate this circuit – Schematic created using CircuitLab

My questions are as follows:

What should I search for when searching for a camera sensor? I was able to turn up the OVM7690, however, that was the only sensor for under $50, which tells me I am definitely searching the wrong thing. -- ("image sensors" on digikey/mouser)
What do I use to process the raw RGB data into a JPEG, and is there any in between steps? What is a device like this called?


texts: What is the squiggly trace on this power rail?

texts:
The image below is a D.C. power rail from an IDE ZIF connector inputting to various components (my crude diagram displays the connections).
    component power inputs connect in between
                      ||
VCC => squiggly trace => various capacitors => GND

I assume the caps are decoupling capacitors (from what I've read), but I don't know what the trace is there for. I measured a resistance of 2 ohms, so it surely isn't intended as a resistor. I looked at other answers mentioning serpentine traces, but this is a power rail, so why would that be necessary?
If any of you know what this could be for, I would appreciate any answers given.
Cheers


texts: Silicon Controlled Switches: applications&suppliers

texts:
I came across this description of what are called "silicon controlled switches." I always look to balance n/p-channel electronics for stability, and using these silicon controlled switches seemed like the perfect way to do so. However suppliers seem few and far between, and the few products I could find were >=$50 a piece!

I could find very little information on these devices online, so I am wondering what technological niche they fill, and if anyone sells them at a reasonable price--i.e. on the order of the price of the components an equivalent circuit made out of regular transistors. If not, why are they so expensive?

I am beginning to suspect that they are more commonly known/sold under a different name.


texts: Set GPIO low while being drawn high from external source

texts:
I have a 3.3V GPIO that I am configuring to an output and settings its value to low during startup. But what happens if the Pin is also being set to high from another source(i.e another GPIO)?

So basicly

GPIO1 Output and set to low  <-------> GPIO2 Output and set to high

during startup

I know this is probably just basic electronics but I really have no clue.

My guess is that the voltage will be high between them for as long as they are connected and when they are not, GPIO1 will go back to being low. But please enlighten me so I can get this out of my head


texts: Could I get a basic description of a 2 to 4 line decoder? I've tried looking online but they make it too complicated for me to understand.


texts: Explanation results of RC simulation wih LTspice/Micro-cap

texts:
I built a basic schema with resistor, capacitor, ground and a battery in LTspice and MicroCap.
I used transient analysis mode.

I expected to see on a chart decreasing current and increasing voltage during launch fixating at 0A and battery voltage eventually correspondingly, but I got flat lines where capacitor voltage is battery voltage from time = 0 and current 0.

I wanted to prove time to charge rule for capacitor where T = 5RC.

I played with various time ranges and time steps and no luck.

What I am doing wrong?


texts:
The I2C manual by NXP allows Clock Stretching (holding SCL low) by slave devices in order to have the master wait for them to process data, interrupts and the like. This is all fine and well, although not having a timeout seems questionable.

Now, I wonder whether a master controller can use the same method for example when waiting for the host processor to provide/collect data. For simplicity I only consider a single master setup, although it should not matter.

Edit: For the sake of clarity I am concerned about cases in which during a multi-byte transfer the host processor is not able to provide/collect data to/from the master controller. Issuing a STOP and possibly resetting the slave's state machine (auto-increment counters, 32-bit internal registers, etc.) is not feasible.


texts: Is the GPIO speed involved in the baud rate of my USART?

texts:
I am working with am ARM Cortex M3 where two GPIO pins are configured as Alternate Function for use as USART pins. When setting the pins as Alternate Function, I have to set the Output Speed of those pins. (I set them at 50Mhz.)

Reading the reference manual (available here) on pages 613 and following, the baud rate of the USART seems to only depend on the APB1 clock rate f_CK.

Does the set GPIO speed influence the USART baud rate?


texts: What is the meaning of current at infinite time for a series RLC circuit formula

texts:
I am reading this doc.

At one point, the author says the current equation form a critically damped series RLC circuit when a step function is applied is:

\$ I_L(t) = I_{\infty} + (B_1 + B_2t)e^{-\alpha t} \$

As far as I know, on a critically damped RLC circuit current will oscillate and  be like this

\$ I_{\infty} \$ will be an equation, not a value, right?

What is the the meaning of this \$ I_{\infty} \$ on the current equation and how do I find it?


texts:
Based on the example in here, I tried a very similar example (but instead of multiplying two matrices I just multiply all the elements in a matrix by 2.0).

However, when comparing the results of multiplying a 32x32 matrix by 2.0 in the ARM (after the optimization -O3) with the results in the Hardware (i.e. FPGA side) I noticed that the first took me 1425 clock cyles where the second took 3654 clock cycles. So basically, the FPGA is almost 3 times slower. (accelaration_factor=0.389)

See this to check the accelaration factors that I'm talking about in the matrix mult example.

I already tried changing the port that connects the ARM and the AXI DMA block to HP instead of ACP and the results are the same.

I'm using AXI DMA also to transfer data rom and to the DDR and I measured the MM2S (Memory-Mapped to Stream) transfer to 1343 clock cycles to transfer 4096 bytes, which results in a transfer spped of 290.8 Mbytes/second. The S2MM transfer in turn has a velocity of 167.2 MBytes/s because it transfered 4096 bytes in 2336 clock cycles.

I have multiple questions in which I hope you can help:

Why is my FPGA design slower than the ARM when multiplying a matrix by 2.0 but not when multiplying two matrices??
Do these AXI DMA velocities look okay to you? By comparing them to Sadri's video it seems that I can transfer way faster. What can I do to improve these transfers speeds?
I saw somewhere that S2MM transfers are expected to be slower than MM2s transfers in the Zedboard. Can you tell me why and if this big of a difference makes sense?
I measured the time in my PC to do a 32x32 matrix multiplication by 2.0 and it's 3.84x10⁽⁻⁶⁾ seconds. Knowing that the same multiplication takes 1.42x10⁽⁻⁵⁾ and the FPGA one takes 3.85x10⁽⁻⁵⁾ one can notice that the CPU is almost 4 times faster than the ARM and almost 10 times faster than the FPGA. If my objective was to design an FPGA model that accelarates software why am I so far off when I'm following an example?

Note: My frequency is 100 MHz so each clock cycle is 10ns.


texts: Cutoff frequency of a second order low pass RLC circuit

texts:
L = 25 mH, R =1 kOhm, C = 10nF and Vs(t)=sin(wt)V, freq = 500 Hz
I am trying to calculate the cutoff frequency of a second order low pass RLC circuit

I don't know if I can still apply the formula of simple RC circuits which is: $$f_{c}=\dfrac{1}{2\cdot \pi\cdot RC}$$
Is there another formula?


texts: Fingerprint scanner fails when magnetized

texts:
Question: Why does a fingerprint scanner fail to work when magnetized?
I took the fingerprint scanner out of an old LG V30 phone because it is a scanner and a push button and is pretty. I added it to my project and it worked fine. Then, when I packaged it all together, the fingerprint scanner is right next to the wireless charging pad, which creates a rather weak, but persistant magnetic field. I found that if the charging pad is powered for a few seconds, the fingerprint scanner fails to work. After turning off the magnet, the fingerprint scanner takes a good ten minutes to start working again.
If I take it all out of the enclosure and keep the fingerprint scanner well away from the charging pad, it works without trouble.
So, I tested magnets. If I put a magnet near the fingerprint scanner, it quickly stops working. If I take the magnet away, it continues to fail for a long time. Degauzing fixes it quickly. This tells me that the scanner is becoming magnetized and then failing to work.
I searched LG support forums and I found that many people reported that their LG V30's fingerprint scanner failed to work if they used a wireless charger for their phone. Note: On the LG V30, the scanner is centered on the back of the phone, which would be in direct contact with a wireless charger.
More experiments. I tested this in the back yard in 30 degree temperatures. It fails quickly and takes many minutes to fix after the magnet is moved away. I tested this inside in 70 degree temperatures. It still fails quickly, but fixes itself faster. Again, this tells me that it is some form of magnetizing.
So, to the question at the beginning. Why does the fingerprint scanner get magnetized and fail? What exactly is happening? How do I keep it from happening - other than keeping all magnets very far away from the scanner?
Note: I can't find a category for identity scanning devices, so I think identification circuits is as close as I can get. If that is wrong, please recategorize this.


texts: Interfacing NT7605-based LCD with MSP430

texts:
I've spent the last week or two trying to get my MSP430 to communicate with an NT7605-based LCD.

I found this post with a very similar problem: Debugging initialization of LCD with NT7605 driver
I've followed every step of this post and even directly copied their code (adjusting the pin connections accordingly) but to no avail.

The specific LCD module I am using is NHD-C0220AA-FSW-FTW (datasheet: http://www.newhavendisplay.com/specs/NHD-C0220AA-FSW-FTW.pdf)

I have used a logic analyzer to verify that I am sending the correct data and that my pins are connected correctly, at least as far as I can tell.

At this point, I have attempted to verify everything that I could suspect to be wrong (incorrect voltage levels, incorrect pin assignments in software, in correct wiring, etc), and I don't really know what to try next.

If anyone has working initialization code along with a pinout that I could try to ensure that my device is not broken, that would be great!


texts: Regarding behaviour of a branch between two independent meshes

texts:
I'm trying to understand how a branch not part of loops affect the circuit.

In the following, I can apply KVL on the two loops (supermesh and the one on the right) and I get the correct answer. The two loops are independent, since one's mesh current doesn't affect the other.
But then what role does the 12.2V source plays?

Similar is the case for this one, the two loops are independent. Solution manual states that KCL assures us that no current flows through either the 1Ω or 6Ω resistor., but I don't see how.


texts:
I am designing a boost converter with the help of this TI app note
My output load current is 300mA and output voltage is 28V.
I need to calculate the output ripple current. But in the app note, no formula for output ripple current is provided. How can I calculate the output ripple current? I also need help with the input ripple current calculation.
I need help with the concept of output ripple and input ripple for currents and voltages.


texts:
The Below mentioned circuit switches 12V when the OPTO sense high voltage

The Strings of LEDs is connected to OUT1 and also an SPST switch is also connected externally (not shown in image). The Switch is connected to 12V on side and another side to OUT1.

When Switch(SPST) is ON, i.e 12V is short with OUT1 for short time, the OPTO senses High-level voltage and MCU turns on the MOSFET producing flashing effect at OUT1. The moment MOSFET is turned ON, there will be high voltage at the OPTO as well as at the OUT1. This won't have any effect until the OPTO continuously senses High Voltage for 5 secs and MCU will turn off the MOSFET, which will happen only when the switch (SPST) is short for 5 secs, the output from MOSFET will in switching state (1sec on/off), so it can't be continuous of 5 secs.

The 5 secs delay in sensing is used to differentiate between the Actual high voltage from the switch(SPST) and the output from MOSFET.

Now the issue is with 5 sec delay which is undesirable, 1sec can work but with the kind of switching pattern, it will overlap and the everytime pattern starts the MCU will shut it off.

How can the circuit be modified with very fewer components so that, the voltage from the MOSFET side does not go to OPTO and only goes to the OUT1 ? And Whenever Voltage comes from the OUT1 Connector, the Opto should sense that.


texts:
State diagram of the sequence network S looks like the following for a jk flip-flop:

Is this the right truth table for it?

           In1   I0
q1q0 -0   0-   -1  1-
 00  00   00   01  01
 01  11   11   01  01
 11  10   10   10  10
 10  11   00   00  11


texts: I'm looking for a specific replacement PCB module connector

texts:
I wonder of anyone here may be able to help. I've been looking for some time now for a replacement for an old (c. 1980s or early 1990s) PCB module connector. I'm looking for anything similar in order to connect these modules to the PCB. I've tried looking for the part no. and also tried image searching. What I am trying to do is connect these modules to updated and modified PCBs, but to do that I need to find a similar connector type.

The actual connector.

The module.

Detail of connector showing terminal block.
If anyone can help me identify and find a replacement for this connector, I should be very grateful. Many thanks!


texts: Why can a UHF RFID antenna read a LF tag?

texts:
How can a RFID UHF (Ultra High Frequency) antenna read a LF (Low Frequency) tag?

I have a antenna designed for UHF made in China, but it can read every tag I have tried (UHF, LF, HF), I don't know why.

The model number of the reader is L6012-L.


texts: How do I determine if a battery will adequately power an electric motor

texts:
I have searched the bowels of the internet for an answer to this question. If I already have a motor, how do I identify what battery(ies) will be sufficient to power it.
For instance, this is one of the motors I am interested in:
http://www.jobymotors.com/public/views/pages/products.php

Construction: inrunner
Nominal Voltage: 40-450V
Poles: 22
Nominal RPM: 6000
Maximum RPM: 9000
Diameter: 154mm
Mass: 1800g
Length: 53.1mm
Continuous Torque: 13N-m
Continuous Shaft Power at Nominal RPM: 8.2kW
Peak Torque: 20N-m
Peak Shaft Power at Nominal RPM (15s): 12.6kW

And here is a battery I am looking at:
http://www.evwest.com/catalog/product_info.php?cPath=4&products_id=263

Capacity: 160Ah
Height: 279 mm (10.98 inch)
Width: 71 mm (2.80 inch)
Length: 182 mm (7.16 inch)
Weight: 5.6kg (12.35 lbs)
Bolt Size: M8
Voltage nominal: 3.2V
Charge voltage cut-off: 3.6V
Discharging cut-off: 2.5V
Life Cycle (0.3c Charging-Discharging, 80%DOD): 2000
Maximum Discharging Current (10 sec.):8C - 1280 Amps

It seems like it may be able to supply more than sufficient capacity and current, but the voltage is tiny compared to that of the motor, can someone please help explain how I can know if a battery will be sufficient for a motor and what are the important specs I should be looking for?
Thank you very much,
Leland


texts: What supplies power to the error amplifier in the LDO voltage regulator?

texts:
I'm trying to design my own low-dropout voltage regulator and am doing some preliminary research. Please forgive my novice question, but one thing that I'm having trouble finding answers for is, what supplies the VDD for the error amplifier in the LDO? Take a look at this simulation, for example: http://www.falstad.com/circuit/e-opamp-regulator.html.

It's not clear to me how the op-amp is being powered. Similarly, check out this schematic from "CMOS" by J. Baker:

It's unclear to me where VDD originates. I thought that VDD would come from the voltage source I'm trying to regulate and that V_ref would be a separate reference voltage to dimension the output, but I don't see this explicitly mentioned.


texts: How to identify V-in V-out pins on Lineage Regulator?

texts:
I botched a soldering job and burned off the V-In pin of a micro FPV camera circuit. Luckily, I identified a lineage regulator next to it, which I see has a V-in pin from schematics of similar lineage regulators. Since I couldn't find the exact part online I was wondering if you could help me identify the v-in pin.

From testing continuity, I figured out that pin 2 is ground. That leaves 2 other pins, assuming v-in is on the side with 3 pins. I am inclined to say that v-in is the pin closest to where the V-in terminal of the circuit board used to be (pin 1) but can't be sure. Is there a way to identify v-in ?


texts: AM437x ZDN (N491 BGA) Footprint Dimensions

texts: I have downloaded and studied the layout that TI provides for the TMDSEVM437X AM437x Evaluation Module. After calculating some distances, I concluded that the pad size used for the ZDN footprint is 0.28 mm x 0.28 mm. It is a 0.65 mm pitch BGA. However, the recommended from TI pad size is 0.4 mm x 0.4 mm. Would 0.28 mm be ok?


texts: Advice on getting a stable analog reading of capacitance

texts:
I would like to detect the presence of a person's hand in a project.

I am aware that one can use a capacitive touch system to do this. I have used a TTP223 module in the past and this works great for switches (it gives a digital output) but I would like to get an analog reading which tells me the proximity of the hand.

I have experimented doing this with an arduino library but the readings are quite unstable.

Are there any dedicated ICs which give a stable analog output of capacitance or approaches which could achieve this?


texts: High-Side P-Channel MOSFET Won't Turn Off!

texts:
I'm using the attached circuit to control the power supply of my battery-powered product. This is the 8th version; the newest addition is Q1 which I'm using for reverse supply protection. All previous versions work just fine.

The issue is no matter what I do to the latch node, the second FET will not turn off. I've removed C7 to rule it out, and tried to swap R7 for a 1k resistor. I've also cut the trace so that LATCH is floating and then directly applied both VBAT and GND to the latch node, neither has any effect. Measuring the supply pin of Q4 shows 4.62V, at LATCH it's 4.58. I've also removed the diodes.

VIN is going directly into an LDO and nowhere else.

Is there something obvious I'm missing here? I've swapped out Q4 for another MOSFET (still an AO3401 but from a different reel).

How do I get Q4 to turn off?


texts: Change all Off Sheet connectors to Ports

texts:
I´m new to Altium Designer. It seems like AD can´t use Off Sheet Connectors for hierarchical design, so I want to change all Off Sheet Connectors to Ports.

Is there an easy way to do this? Btw: There are a lot of Off Sheet Connectors in the design.

How can I use NetLabels in the hierarchical design? Somehow only Ports appear as Sheet Entries.

Thank you.


texts:
i was wondering how i could write a delay function in the STM8 - IAR Embedded Workbench?
I used the search-function inside the IDE, so i found the "__delay()" function but if i try to use it i get:

"no definition for '__delay'"


texts: Is a 25 amp SSR safe to use in a circuit that draws 25 amps?

texts:
Specifically, my circuit consists of a 5,500 watt hot-water heating element on a 220 volt circuit. I am controlling the heat output using a PWM signal - the heating element is turned on/off with a solid state relay. The PWM signal runs at a 0.5 Hz frequency with a duty cycle typically ranging between 80% and 100%

I have found a relay that is rated for 240V, 25 AMP on the control side. Is it safe to use this relay in my circuit? By 'safe' I mean do I risk a fire hazard or other life-threatening condition by using this relay in this manner?

Here is a link to the Data Sheet Link.


texts: Average output voltage of single-phase thyristor-controlled bridge converter

texts:
This question is highly related to this one but I don't find the answers satisfying.

I'm a bit confused about the equation for the DC output voltage of phase-controlled bridge rectifiers.

\$V_{o_{ave}} = \frac{V_{m}}{\pi}\int_\alpha^{\pi+\alpha}\sin\theta d\theta = \frac{2V_m}{\pi}\cos\alpha\$

\$vs.\$

\$V_{o_{ave}} = \frac{V_{m}}{\pi}\int_\alpha^{\pi}\sin\theta d\theta = \frac{V_m}{\pi}(1+\cos\alpha)\$

I see both in books. Apparently they are both valid. So which one is used when? Does it depend on the kind of load? How can the bridge converter still conduct after 180\$°\$ as indicated in the first equation? I'm just looking for a clear distinction between the two in terms of usage. I'd also very much appreciate a thorough explanation.


texts: How critical are the input and out capacitor values in a linear voltage regulator?

texts:
7805's datasheet recommends a 0.33uf and a 0.1uf capacitor for input and output respectively.

For a clean input voltage and a resistive load, I've used this kind of regulators without the capacitors and they worked just fine.

In cases with a noisy power supply or if there are motors in the circuit this capacitors start getting more relevant but it's hard for me to get a sense of what's happening there, I know they are acting as a low pass filters but I've no idea of why are those the recommended values and if in some cases other values could be better or what will happen if I select a too big capacitor for either the output or the input.


texts: Itead Sonoff RF WiFi & 433MHz switch: Identifying an unknown chip on the 433MHz card

texts:
I have the Sonoff RF which is a mains relay switch which is activated by either WiFi or a 433MHz remote.
The particular Sonoff RF's I have arrived from China on 21/9/2017.
I flashed these Sonoff RF's last week with the lastest tasmota firmware. The firmware version I flashed was sonoff.bin (there are many other tasmota firmwares available).

I understand that Sonoff RF firmware for the WiFi card (which is I beleive ESP8266-01 based), and the firmware for the 433MHz card are different and seperate. This makes sense becasue a Sonoff vesion is sold without the 433MHz card. Sold without the 433MHz card it is called the Sonoff Basic.

So by flashing new firmware to the ESP8266-01 card the 433MHz card is unaffected.

This I have confirmed through use of the 433MHz card since flashing the tasmota firmware: the 433MHz card behaves in the same way as it did with the original OEM Itead firmware. In any case the author of the tasmota firmware states that his firmware has no impact on the 433 MHz card.

I am interested in the 433MHz card becasue I beleive it could have a better firmware.

Currently a 433MHz remote paired with the card can only toggle the relay  switch.
For more useful functionality the remote needs to be able to set the switch to OFF or ON as well as having TOGGLE functionallity.

As part of my initial investigations of this card, I am trying to identify the chips on the card. I've used Google quite extensively with no luck in regard to one of the chips, so am wandering if anyone on here has some working knowledge of such a chip arrangement.

Below is a picture of what I call the front of the card

The picture above shows the SYN470R 1631 chip. The data sheet is here http://img.ozdisan.com/ETicaret_Dosya/453934_1928180.pdf

Below is a picture of what I call the back of the card

The above photo shows the can with 6.7458 stamped on.

I am unable to identify the 16 pin SMD chip, with 4 pins per side.
As far as my eyes can see the chip text reads
BB1 0 F 2 G A  GOGA4 1620 A,
but I may be wrong and your eyes may be better than mine.
I've googled various possible permutations of this with no success.
May be I missed something obvious.
Eg I tried 8810 instead of what looks to me like BB10, etc.

Do you know what this chip is?

Perhaps you can shed some light on how this 433MHz board can be programmed for ON / OFF as well as Toggle switching functionallity. If so please post up.

PHOTOS ADDED BELOW IN ATTEMPT TO CLARIFY CHIP IDENTITY

Below photo shows side view. Seems to show 20-pin package

Below photo shows 5 tracks coming in from left. 4 lower down and one appears to go to the top corner pad. QFN20 has corner pads. So this potentially accords well with the package being a QFN20.

Below is from pg 48 on datasheet linked in the answer. Shows 4 pins at edge of chip & two corner pads.


texts: Is open circuit voltage of the supply important for Lithium battery charging process?

texts:
Is open circuit voltage of the supply important for Lithium battery as long as we guarantee that the maximum allowed voltage will not be exceeded when the supply is connected to the battery?

Suppose we have a normally discharged (say 3.1V at that moment) single cell  (3.6V) lithium battery and a high internal resistance voltage source, say 12V. If we guarantee that the terminal voltage will drop to some value under 4.2V, is it safe to connect the battery to the source? Would the initial terminal voltage give any harm to the battery, or the damage due to the excessive voltage is only related to the electric field inside the battery, meaning that the damage state is a function of "state of charge" and the current?

  Of course, the terminal voltage MUST be monitored in order not to exceed 4.2V limit while the battery is getting close to the fully charged state. However, this safety precaution is beyond the scope of this question.


texts:
I am working with an electrochemical device which (I guess) harvests power. How can I be sure that I harvest power ?

My first idea was to plug a battery on my system. The problem is that my device products mW with a open circuit voltage of 600 mV, so it's impossible to load a battery by just plugging.

My second was to put a resistor in water and to study the temperature difference to follow the increasing but I guess this temperature gap is too small.

Any other ideas ?


texts: If I connect a schottky-diode to the DC converter output, why doesn't sense the voltage?

texts:
Why doesn't work the second version? If I try this version no voltage on the output. Why?

I would like to make a reverse polarity protection, but the problem with the first version: in idle mode there is a voltage e.g: 12.00V, but when I connect a variable load the voltage decreases when the current increases, because more voltage drop on the schottky-diode. I would like to use a reverse polarity protection but I don't want that voltage drop vs current increase.
I can't use a mosfet because I use 1V output voltage too.


texts: How does an MPPT charge controller control the input voltage?

texts: I understand how buck/boost converters change the output voltage, but how is an MPPT converter able to control the input voltage/current while keeping the same output voltage? I understand the theory of MPPT, but not the implementation, and every search for "how MPPT works" leads to how the theory works.


texts: Strange ADC sampling frequency / clock frequency on STM32F401 board

texts:
I use a timer to trigger ADC sampling on STM32F401, and the interrupt service routine of ADC will toggle a GPIO pin so that I can measure the ADC sampling frequency using an oscilloscope (which should equal the timer frequency). However the results I get from two scenarios, one being on a Discovery board and the other on my own board, are different. I am wondering if it has something to do with the crystal connection.

In both cases, the CPU frequency is set to be 84 MHz, and the timer frequency is scaled down to 16 kHz. A 8MHz external crystal is also used.

I first test on STM32F401 discovery board which uses STM32F401VCT6. The GPIO pin toggles with 16 kHz frequency. So I think the code is working.

After that I make my own board with the MCU being STM32F401RBT6. I can program and debug the code via SWD without problem, but the GPIO pin toggles with ~5.1kHz frequency. The code is largely same -- the only difference is I use a different ADC pin (thus the corresponding change in the firmware) which should not matter.

The STM32F401 part of schematic of my own design is shown below:

The part of layout related to crystal connection on my board is here:

The 8MHz crystal on my board is ABLS-8.000MHz-B2-T which needs 18pF loading capacitor. I use two 5% 18pF capacitors. I have probed the oscillator pin with an oscilloscope (despite the probe capacitance may play a role). I can see 8MHz sine-wave like voltage signals, but the amplitude is not from rail to rail.

The crystal part of schematic of STM32F401 discovery board is:

You can see it has a 220 Ohm series resistor on the PH1-OSC_OUT pin, which I don't have on my board.

Could anyone please advise what I may have done wrong?


texts: I would like to know what are the available (industry standard) CCD sensor resolutions for cameras in the visible light. What is the highest CCD resolution that can be found in the industry?


texts: Can you help me with a way to step up a voltage of about 3.29 to 4.5/5V? I need a simple and efficient circuit to implement this.


texts:
For a project, I want to have two microcontrollers talk to each other via an SPI interface. I wrote the following code for the target microcontroller:
volatile uint8_t data;

void spi_init_slave (void)
{
 DDRB=(1<<PINB4);               //MISO as OUTPUT
 SPCR=(1<<SPE)|(1<<SPIE);       //Enable SPI && interrupt enable bit
 SPDR=0;
}

uint8_t SPI_SlaveReceive(void)
{
  /* Wait for reception complete */
  while (!(SPSR & (1<<SPIF)))   ;
  /* Return data register */
  return    SPDR;
}

ISR(SPI_STC_vect)
{
  uint8_t y = SPI_SlaveReceive();
  PORTD = y;
}

int main(void)
{
    DDRD = (1<<PIND0) | (1<<PIND1) | (1<<PIND2) | (1<<PIND3) | (1<<PIND4);
    spi_init_slave();                             //Initialize slave SPI

    sei();
    while(1)
    {

    }
}

The master is sending a number which the target displays using the LEDs attached to port D.
I'm using an Atmega8P for this project.


texts:
What is the proper zero orientation for a SMT LED?

According to screaming circuits and IPC-7351, the cathode should be on the left for a molded diode. HOWEVER, when I use Altium's component wizard to create a diode, it places the cathode (K) on the right! I would assume that IPC-7351 would be correct, but I don't understand why the Altium default would be backwards.

Does it depend on the manufacturer? How does the assembly house know which way is correct?

For reference, I am looking at the OSRAM LS R976, which has the cathode towards the holes on the tape.

Unrelated: Why does the search in the top right corner return different (and in this case, worse) results than the search that comes up when you click ask question?


texts: Why do we connect neutral and ground at the transformer?

texts: Why do we connect neutral to ground at the transformer, why can't we just connect that neutral to the ground at our house?


texts: I came across this 7805 voltage regulator. In the datasheet is mentioned the current vs voltage graph. What is Input to output diferrential volatge?


texts:
When two or more of these modules have their 5v pins hooked up to a common 5v rail (power off) and I connect an 4-pin SWD st-link to the programming pins of one, I'm finding that all modules (and peripherals attached to them) power up. In other words, the 3v3 from the st-link is powering everything. The voltage on the rail is 2v6. Would it be better to have a diode between the 5v pin of each module and the 5v rail?  Thanks for your thoughts.

This shows both the mcu board and the swd st-link board:

https://www.dx.com/p/cortex-m3-stm32f103c8t6-stm32-development-board-w-swd-socket-st-link-v2-programmer-emulator-395848#.W_vs7RgTE0M--


texts: Can I calculate how much time it will take for an electrical signal to propagate through a TTL circuit?

texts:
Given a particular circuit of TTL, can I calculate how much time it will take for an electrical signal to propagate through some section, or all of, the circuit?

If I wanted to know how long it takes an electrical signal to move from a point A to a point B in a given TTL circuit, how would I calculate that?

If I have a circuit with a system clock (very basic TTL computer architecture), can I calculate how long it will take an electrical signal to move through the entire system after a single CPU clock pulse?

I'd really like a way to calculate this theoretically rather than only testing a circuit to somehow derive this information, but I would also appreciate knowing how I could test a circuit to find this information.


texts: Should I always put a low-pass filter on an ADC input?

texts:
I'm a recent hobbyist EE and new to micro controllers.

I've built a test circuit to make measurements with a type K thermocouple, a PT1000 as well as an oxygen sensor. The weak signals go through a low-pass filter to remove high frequency noise and are amplified by OPs before they go to the ADC inputs of an Atmega328p (not Arduino).

In my code I am doing noise cancelling with CPU sleep/ADC interrupt, 16x oversampling and creating a moving average.

The measurements are stable if the circuit is powered via the USB of a laptop and particularly stable if the laptop itself is connected to AC. But when the device is powered with a wall-wart, the readings are very unstable unless I ground the circuit. The readings are also stable with no sensors connected, i.e. the PT1000 with its 4m cable replaced by a resistor.

Putting a low-pass filter with a cutoff frequency of 1.59 Hz in front of the ADC input helps a lot and stabilizes the measurements, so I guess my circuit suffers from 50/60 Hz noise.

So my question: For such slow signals, is it a good idea to always put such a low-pass filter in front of the ADC input or would I just connect the device to ground? Which would be strange when powering the device with batteries or a non-grounded power supply.


texts:
I started using Altium Outjobs to generate assembly files.  Great change, should have done it sooner.

I understand how to use the custom parameters in the Outjob file; however, I've only found that you can link to the parameters in the Project Options.

Are there any other places where you can define parameters, that feed back to the Outjob?

I was orignally hoping you could update the board version (rev #) in the .SchDoc, so as you update the schematic the revision number changes.   I am using SVN for version control, so it is a little wonky updating the Project Parameters.


texts:
Possible Duplicate:
  What exactly does a diode do?

What happens in a diode to make current only flow one way around a circuit? My physics teacher said it was something to do with the metals in it and the impurities in them. Can anyone give me a detailed explanation. Any help much appreciated.


texts:
V_p(rect) is the rectified unfiltered peak voltage

V_r(pp) is the peak-to-peak voltage after filtering by a capacitor

Here is a picture:

V_r(pp) is given by the expression:

Which I have no problem with its derivation.

Now, as you can see with the first picture, the book shows that V_dc = V_p(rect) - 1/2  V_r(pp)

Why is that?

When he derives an expression for V_dc , this is what he does:

In short, why is V_dc the difference between the peak rectified unfiltered voltage and the peak-to-peak filtered voltage?

Here are also the circuit diagrams:


texts: On a microprocessor with hardware TLB management (say an Intel x86-64) if a TLB miss occurs and the processor is walking the page table, are these (off-chip) memory accesses going through the cache hierarchy (L1,L2,etc.)?


texts:
I bought a DVI-I male to DVI-I male (dual link) cable, and found out that there is no conductivity between the both ends of analog pins. Particularly, in the following diagram, the pins C1, C2, C3, C4, and 8 on the two ends do not seem to be connected to anywhere.

My understanding is that  DVI-D cables do not have analog pins, and the purpose of DVI-I is to be able to connect to any kind of DVI devices as long as the devices on the both ends are compatible. Is my understanding wrong? If I am wrong, what is the purpose of a DVI-I cable where there is such thing as DVI-A and DVI-D cables? If I am right, I am planning to complain the seller about the cable.


texts: How to use LBO on Powerboost 1000C as input for Arduino

texts:
I am using a project which uses an Arduino Uno and a powerboost 1000C. in the manual it says,

  LBO - not a leveraged buy out! this is the Low Battery Output. By default it is pulled high to BAT but when the charger detects a low voltage (under 3.2V) the pin will drop down to 0V. You can use this to signal when its time to shut down or alert the user that the battery is low. There is also a red LED connected to this pin.

I understand what is going on but I don't know how to hook it up to the input of an Arduino input in order to do other things when the battery is low.

I had an idea of hooking up an optocoupler (with current limiting resistor of course) but I can't help but feel that is unnecessary. I have some PC817s so if that would work (with 5V and arduino input connected to one side and a 220ohm resistor in series with LBO and Bat on the other end (anode connected to bat)) I'm fine with doing it, but is there a better way?


texts: A MOV (metal oxide varistor) fell on hard floor. Could it be damaged?

texts:
If a varistor falls on hard floor without any visual damage
that can be seen after that, can it still be damaged inside?

Are varistors sensitive to that situation?

How can I do a simple test to check that the varistor didn't
get damaged from the fall?

Thanks


texts: Plain English explanation of the Space-time Code Block by Alamouti

texts:
I checked about the Space-time code block online, but all of the explanations are either short or too simple, or too mathematical and complex

Could anyone here provide an explanation of what Space-time Code Block is. How it works, where it is used and what is the main idea behind it?


texts: Is there any standalone IC do the same job this 5mm Led (standalone flasher and builtin control IC)  does?


texts: Control 12V pump with Raspberry Pi through relay

texts:
I'm building a small project where I will control a 12V water pump with my raspberry Pi.

I have made a small sketch of what I imagine should be a correct setup, but have been reading about the need for a flyback diode.

I'm new to electricity, so I'm not sure how to connect this. I just bought a pack of 1N4007 diodes. How should I connect it so that it protects my Raspberry Pi/relay from any arcs?

I have the following relay:

Should I remove the jumper between COM/GND to separate the two power sources through the optocoupler?

Appreciate any help on this, thanks!


texts:
I have gone through the following circuit provided by microchip technology and I get trouble in understanding the circuit circled in red the the image!!

As I understood, this circuit is used as a current sensor with an external ramp compensation.

The current is sensed through the transformer T1 and goes through the diode D2, this current is converted to voltage through resistors R37 and R38.
The Vext of MCP1630 which is a square wave signal feeds or charges the capacitors C28 and C5 to construct a ramp generator signal
the two signals are added through a very small signal R5 to feed current sensing pin of MCP1630.

Am I right ?????

Pleas give me a deep explanation of this circuit


texts:
We all know that, there are two assumptions that can be made whe analysing ideal operational amplifers, which are:

V+ = V-

I+ = I- = 0 (no current flows through op amp inputs)

but my question is: "Under what operating conditions are these assumptions valid?"

i am not sure if I'm right, but i said that the input resistor being infinitly big and the output resistor being infinitly close to 0, is this correct?


texts: Where to put the switch on a power supply? 5V/12V or 230V?

texts:
An arcade videogame power supply supplies +5V, +12V and -5V (see JAMMA). They usually don't have a switch.

If I were to put a switch on such a power supply, what are the (dis)advantages of interrupting current on the 230 volts versus the +5/+12/-5 volts sides? I probably want to have one for 230 volts, but does it make sense to have the others (or maybe one for all three low voltages) as well? One does often just want to cut power for a few seconds to reboot the arcade system. (As a side note, whether -5V is actually used differs from system to system.)


texts: Interfacing dual supply op-amp with microcontroller

texts:
I have an dual op-amp amplifier circuit (LM833) to amplify a signal with a +-10V dual-supply rail from a 22V supply with a resistor voltage divider. The output is rectified into a 0-8V output, for which I simply require a logic output above a certain threshold (about 3V).

The problem is that the Arduino micro is powered from the same 22V supply through a switching regulator. So the ground references of the op-amp output and Arduino are at different potentials, therefore I cannot use a simple MOSFET to interface between the two circuits.
Is there another way to safely connect the circuits without using a relay which would be too big and potentially too slow for the switching application.

simulate this circuit – Schematic created using CircuitLab

This is a simplified schematic showing my main problem, since the arduino ground is with reference to the -10V point of the opamp.


texts: Does the body diode of the high side n-channel FET in a buck converter turn on during switch node voltage spike time?

texts:
A typical synchronous buck:

The normal switch node spike that people typically see when the high side FET turns on:

In the past i have been fairly negligible on this part. When the switch node spike occurs, Switch node voltage - VIN is always more than a typical body diode drop, so why doesn't the body diode of the high side FET conduct?
Thanks!


texts: Base current and Vce relation in NPN transistor output characteristics

texts:
Regarding the active region of an NPN transistor and output curves, for a fixed Ib when the Vce is increased the Ic increases; namely Early effect.

The reason if Im not mistaken is that the increase in Vce makes the base thinner.

How can we logically derive the rest from here?

Here is what I assume when I look at the output characteristics:

  Vce increases--> Base gets thinner ---> The recombination in the base happens less
  hence Ib tends to decrease---> To keep the Ib same Vbe is
  increased-->Ic increases because it is directly a function of Vbe

But there is a part in my logical arguments which is: "The recombination in the base happens less hence Ib tends to decrease".

But the base current is not only occurring because of the recombination but also because of the holes in base diffusing into the emitter. And to me if the base gets thinner the diffusion should be easier and Ib tends to increase.

So my confusion is when the Vce is increased Ib tends both to decrease and increase. That then invalidates my logic.

Where am I wrong?


texts: Obtaining Accurate Measurements from Strain Gauge

texts:
Background  I have a strain gauge that I need to obtain measurements from. The product page indicates that the sensor is a half bridge configuration (one active/one compensating element). The sensor has three wires: White (common), Red (active) and Black (compensating). I have never used a strain gauge before, so I may have some fundamental misconceptions about how it works.

My Understanding of the gauge is that I need to measure the resistance and use the equation:
\$strain = (R - R_0)/(G*R_0)^2\$, where \$R\$ is the measured resistance, \$R_0\$ is the gauge resistance, and \$G\$ is the gauge factor. I do this for both leads (active and compensating) and subtract the two to find the actual strain.

What I have Tried Using an Agilent Data Acquisition unit, I have successfully measured the resistance of both leads as ~120\$\ \Omega \$, which is expected, and calculated a strain of essentially zero.

My Problem started when I tested the sensor by heating the it (attached to a metal plate) to 50C. I expected the strain to increase, but was surprised to see that it actually decreased. Now I am questioning my basic understanding of how this sensor works. The change was very small, but distinct from the noise (below image).

Additionally, the noise I am getting from the sensor is less than ideal. I suspect some of it is caused by the furnace I am using, as there is a noticeable increase in noise when I turned it on (below image). Update The increased noise level remains even after de-energizing the furnace, so I now believe the increase is caused by the temperature.

Questions

Shouldn't strain increase as the temperature increases?
Is this level of noise normal? How can I reduce it?
Am I using the strain gauge correctly?


texts: How to estimate force caused by a strain in a material from a strain guage?

texts:
So, I am learning about how strain gauges work and I understand that through stretching or compressing resistance of the staring gauge can be changed which can be measured in resistance accurately connected to a wheat stone bridge or some kind of bridge and the voltage difference is amplified by an op amp.

Okay, so far sounds good.

But with the values of resistance and voltage difference, how do you exactly use this information to calculate the force caused by the strain. I couldnt find where to look for this equation or information in general. Maybe I am asking questions about mechanism too much but was just curious to know exactly how strain gauge could be used to calculate force in a load cell for example.


texts: I'm hosting a LAN party and could use some help mitigating power concerns

texts:
As mentioned, I'm hosting a LAN party for ~10 people in a few months. I've layed out a rough idea of what gear we'll have, where it will go, etc. However, I'm wondering if so many devices (TV, Xbox, Laptops, Monitors) will be too much.

Below is a diagram of my expectations as far as each piece of equipment that will require power. Additionally, I've included all outlets. The numbers beside them indicate which circuit they're on.

Can anyone let me know if this is safe and/or practical? I apologize if I haven't included enough information; I'm quite out of my element, but will do my best to edit this question and provide any missing detail.

Circuits are 15A each, 120V outlets.

After some research, the numbers below are what I believe to be correct. Perhaps someone can acknowledge that they're "realistic", as I've gone off of what I could find online, but am not entirely certain how to apply the information I've gathered.

Laptops:         11  x   80W  =  880W
Monitors:         7  x   90W  =  630W
Televisions:      3  x  170W  =  510W
Xboxes:           3  x  110W  =  330W
Network Switches: 2  x    5W  =   10W
                                 ----
                                2360W (?)


texts: I've been working a few days on this and have still come up with nothing.  I am trying to make an AM radio using a silicon diode, but all of my attempts have failed.  I believe my latest attempt most likely came closest, but it did not work.  Does anyone have any plans for making a radio using a silicon diode I can look at?  All of the plans I have seen have all used germanium or some other low voltage drop diode.  The plans I've come up with have not worked.


texts: Why is 433 MHz used widely in RF modules?

texts: I was planning to interface an RF module to my PIC16F877A microcontroller and was exploring the web. I came across many modules which use 433 MHz as the standard frequency. Why is it so? Can't we change the frequency as per our requirements?


texts: SPI interface is working, but there is no power, what could be wrong?

texts: I have an ADC attached to my uC on a custom PCB. The traces are just directly connected between the uC and the ADC. Here is a photo of an oscilloscope trace of SCK and MISO. SCK is Blue, MISO is Red. I see my clock and my data, but they are only about 940mV of the 3.3V range. I have a bypass cap on the ADC (and the uC). Where did my voltage go? Its a hobby oscilloscope. I can try a better one tomorrow.


texts: Actual/theoretical benefits of round or flat outlet prongs

texts:
What might be the reasoning for European connectors having rounded prongs while USA and UK connectors are primarily flat pronged?

Please correct any mis-tagging.


texts:
simulate this circuit – Schematic created using CircuitLab
This simple circuit is causing to the resistor to overheat. How do I fix this?


texts: How to give input to microcontroller from a 3.5-mm stereo jack

texts:
I need to connect a 3.5-mm stereo jack to atmega8 microcontroller, and to lit an led if any music is played in the stereo device. Could anyone tell me about how to connect the 3.5-mm jack to the microcontroller?

I dont have any idea on electronics. So any help on the circuit will be appreciated.


texts:
I have 2 x 2N2222 BJTs powering 2 relays of 200mA each.

I am using 2 output pins with 500ohm resistors to power the transistors.

After powering it the circuit not working well, while replacing the relays with LEDs works well.

So I want to try and replace the 2 BJTs with 1 power FET. I have an IRFZ44N.

But after reading articles about the transistor, it seems like I cannot use it at all - looks like the gate needs +20V to work, while my AVR output 5V.

Is this true, and if so, what can I do?


texts:
I need help in learning derating analysis for a vienna rectifier circuit (may be anything). Do you guys suggest any material to do the derating analysis by hand for each component understanding the voltage current and power at each component.

Practical example based material wold be good so I can learn it quickly and apply to my circuits.


texts: What do I need for a portable 12V deep cycle battery?

texts:
I'm going to buy a 75 Ah 12V deep cycle battery soon, and I'll need to use it as a portable 12V power supply. The build should be quite simple, but I'd like to ask a few questions to make sure I'm doing everything the best and safest way I can.

So I'm planning on getting some sort of battery box, so it will be easy to carry and have all the cables sorted inside of it, I thought of having the following cables: I'd have 2 cigarette sockets, 1 for the main 12V output I'd need, and one more extra in case I'll need it in the future, 2 USB outputs, and a voltmeter so I'll know where I stand.

I'll also want to connect an on/off switch, for more safety etc. The last thing I'd maybe want to have, and I don't know if it's even possible, but some sort of charging port. I have a battery charger, but it has those crocodile clips, which means I'll need to open the box and connect it directly. That's not really hard or even messy, but I think that if I'll manage to make some sort of charging port, it will be easier, safer, and better overall.

Now I can sort of see in my head how I want to connect everything, doesn't seem too complex to me, but what I want to know is if there's something else I need, maybe a fuse? Or just anything else that you can think of that I might need for that, some general tips it's important to know, and just everything else that pops to you mind. Thanks!


texts:
When I select some components in file ".sch" and then in file ".pcb" Altium will focus them and remaining components are still diplayed normally.
But I only need to display the ones I selected and remaining components should shaded, which help me to focus the selected ones clearly.

Do you instruct to change option in Altium to do this function?

Ps You can see below picture which I get from Fedevel's course "Advance pcb layout"


texts: Hooking up a 3 wire load cell and measuring the output on an ADC

texts:
I am trying to get 4, 3 wire load cells connected together in the form of a wheatsone bridge correctly to measure weight. I have the following schematic used from this http://www.nerdkits.com/forum/thread/900/:

I am giving e+ 3V and e- to ground. I am measuring the difference between the S+ and S- terminal. When I put pressure on each of the load cells I see a deflection which goes postive for 2 cells and the voltage goes decreases(but not below 0 (stops at 0) ) when I put pressure on 2 other cells. When I place the load, the weight is uniformly distributed across all 4 cells and as a result the voltage is constant. But I know that this works because I tested it out before opening it up. What am I doing wrong and how exactly do I read these inputs from s+ and s- using an ad620 or LM307?


texts: Is there a typical 'ferrite' for use in a PCB?

texts:
I have a circuit diagram that I am trying to replicate (actually the Teensy 3.0/3.1 circuit diagram shown here https://www.pjrc.com/teensy/schematic.html) and there is a component called simply 'ferrite'. On the board it is a SMB component, maybe in a 1206 package but with no markings.

Is this a common component such that there is a 'standard' value for it? (e.g. 'pullup resistors' are usually around 10kOhm or specified according to the internal resistance of the driving pin)


texts: RF transmitter interference to a GE electric stove

texts: I have a GE Stove with electronic controls which malfunction when I transmit 500 watts of RF on the 1.8 mhz Ham radio band. I suspect the transmitted RF is getting into the AC lines and causing the malfunction of the stove controls. Would an AC line filter installed at the AC supply box help the problem ? Any recommendations for a filter ? The stove draws 35 amps on each leg of a 220 vac 2-phase line.


texts: ATMega328 attenuated potentiometer voltage

texts:
I've just got this problem:
I have a potentiometer with resistance of 50k and i have an arduino nano which has an ATMega328 IC on it.

I attached the potentiometer normally: two pins for source and gnd and one pin going to the arduino nano's analog pin.

If i turn the knob slowly, the potentiometer increase its reading linearly and nicely. But if i were to turn the knob rapidly, say from medium to low, the potentiometer momentarily jumps up to the source voltage and return to its normal reading after 2 seconds or so. I'm suspecting that's because the arduino nano's analog pin attenuate the voltage so much and momentarily give me wrong readings. I checked ATMega328's datasheet and they have an internal resistance of around 60k which makes sense perfectly.

I'm using the potentiometer in an alarm clock to set the time precisely whenever i turn it and it always momentarily jumps to the highest reading or to the lowest reading. I can always wait a moment to make the values stable again but that takes too much time.

I could have simply lower the resistance of the potentiometer to around 10k or 5k but do you guys have another solution for this?

Thanks in advanced.


texts:
What is the capacitance of this circuit if S is closed? AFAICS, Rules for capacitors in series or parallel can only help to simplify the problem down to

     |--||--|
A -- |      |------|--- B
     |--||--|--||--|

, but this weird parallelism with nothing for the third capacitor is what confuses me.


texts: How to synchronize a generator on the electrical grid?

texts:
I've read many articles about paralleling two portable generators or synchronizing a power generator on the electrical grid.

I have the theoretical background about that topic and I know the four conditions that must be met:

Phase Sequence
Voltage Magnitude
Frequency
Phase Angle

What I know is just theory. I would like to know how to do it practically? What is the name of the device that make the synchronization process? and How to use it? I searched on YouTube for practical tutorials but I did not find useful information. Does anybody have?

Thank you very much,


texts: Calculate necessary attenuation (in dB) to achieve a given output voltage

texts: I need to connect an audio unit with an output of 2V (and an output impedance of 560 ohms) to an amplifier with input sensitivity of 0.985V. Since the 2V output is too high for the amplifier, I need to attenuate the signal, but I'm having trouble calculating how many dBs would be necessary to lower the signal from 2V to, say, 0.9V. How should I calculate this?


texts: LTspice, plotting a node voltage problem

texts:
Edit: The question is answered in a such way that I am happy now, however for the interested ones, the mystery of the question is still on.

These two are the parts from my circuit, related to the question.

Now, I want to be able to plot V(pnp_c), however it does not allow me to choose it. You can see from the above list that there is not such quantity as V(pnp_c). If I remove -9v label, then it allows me to select it. You may say that "they are essentialy the same point, they are at equal potentials, why bother?". My answer to that is, while simulating the power of the pnp by ALT + left click, Ltspice formulates it so that it will depend the value of -9v label as follows:

Please note that npn power expression is independent from V(+9v) instead it is related to npn_c which is nice.

The problem starts here, If I want to change the power rail to another value, by directly connecting a voltage source, or by changing it with another label, then I also have to replot the power on the pnp. However, if it were be using V(pnp_c) instead of V(-9v) then this problem would have been eliminated.

I wanted to think that it just don't accept two nodes with different names and it chooses the constant voltage one, however as you can see from the above picture, for npn, the arrangement is the same but it does not create a problem and recognises npn_c as a node. Things get more confusing at that point.

So, why I am able to choose npn_c as a node but cannot choose pnp_c ?


texts: Closed-loop pole moving to RHP - less stable or more stable?

texts:
I was reading Razavi's Design of Analog CMOS ICs book and came across this in the Stability and Freq. Compensation chapter,
What the book says
The closed-loop transfer function of a system is given by the following:

It then goes on to say that,

Okay, that makes sense to me. As loop-gain (beta or Aol) increases, our pole moves further into the LHP, making any oscillation die out much quicker. Now, a few pages later, the book has this,

He says here that by reducing the feedback factor (hence loop gain) our system is more stable and this makes sense to me from the bode plot.
My Question
The two bolded statements above contradict each other. If I reduce my feedback factor (hence loop gain), my pole will move towards the RHP and thus from the s-plane perspective, the system is less stable but from the bode plot perspective, the system is more stable. Why does the s-plane and bode plot contradict each other?


texts: General wiring questions: high power LEDs, relay and microcontroller

texts:
I think I understand the Raspbery Pi GPIO pins and most of how this diagram below works, at a high level at least.

First question, it's not clear to me exactly how the middle part with the resistors and transistors works.  Can anyone help explain how this works in another way? This is essentially flipping the high/low logic from the GPIO pins so a low output from the pi is non-zero voltage to the relay input?

source

another reference for the middle section

To power the LED's on  the other end of the relay, I have a wall AC adapter to 28VDC, .9A that will power a 700 mA driver.  The driver will connect each of the relay terminals to the LEDs.  I will only need one led/relay active at a time.

My second question, if I run 8 wires from the relay terminals to power each LED, can I connect them all to the same wire for ground to return?  I'd like to have some sort of quick disconnect for the LEDs so they can be easily unplugged, can you have multiple quick connect terminals spliced into a shared ground or is that a bad idea?  Any recommendations for quick disconnecting plugs?

Still pretty new to all of this so I feel like I could very easily miss anything from "common sense" and "good practice" to "just completely wrong".

Here's the LEDs I was planning to use in a series to justify the 700mA current.


texts: STM32L432KC: Why is the output of the DAC looking like this?

texts:
Just had a quick question as to why the output of the DAC looks different at varying frequencies.

Using a STM32L432KC that has a 12-bit ADC and 12-bit DAC.

Figure 1. Initial Start

Figure 2. I just zoomed in just to show what it looks like for later on

Figure 3. Almost looks like figure one but at a much higher frequency

Figure 4. If zoomed in looks like Figure 2

My point is I guess, using the same time sample why does it go from looking nice to pretty bad back to nice at certain frequencies?


texts: Circuit or Equipment to delay high speed square clock signal?

texts: Hi I have a ttl clock signal that id like to change the phase of to see if it changes effects the unit under test (not relevant but its a digital transmitter and an automated testing setup) this way I can see if longer bnc cables would cause issues (because of how it changes phase). What sort of circuit would I need to make or what equipment would I need to buy to achieve this? It is fairly fast like 50 MB/S.


texts:
I'm currently designing a carrier board on which is integrated a PLX PEX 8750 PCIe switch connected to several PCIe connectors.
The problem occurs when routing PCIe lanes, since I can't route them without having to “criss-cross” the lanes. Thereby, I consider using the lane reversal capability.

The PEX 8750 supports dynamic Lane reversal as mentioned on its datasheet, but it also indicates that "If the wiring of Lanes to a device is reversed (on both Transmitters and Receivers), only one of the two connected devices must support Lane reversal."

I also read a paper published by Intel which says: "Unless you are certain that lane reversal is supported and guaranteed by at least one of the devices in question, do not rely upon this feature."
Taking Advantage of the PCI Express Specification - EDN

So, which of the two sources should I believe?