texts: What could be causing this interference and how to eliminate it?

texts:
(update: Please also see the major edit at the end)

A sensitive electronic equipment Device 1 below is basically composed of a power line EMI filter at the mains entry, an SMPS power supply which powers a data acquisition board and a USB hub. All this Device 1 is in an enclosure and gets the power through power cord 1.

Any device like Device 2 below if connected to a mains nearby and if switched OFF or ON sometimes it upsets the DAQ. Same problem also occurs randomly.

So Im suspicious of the interference to Device 1 through AC mains.

For a quick solution is there a possibility that an isolation transformer would help right before the Device 1?

Edit:

I tried with an isolation transformer still somehow the AC mains of Device 2 upsets Device 1.

Major Edit:

I cannot verify whether the spike is the scope's probes pickup or really conductive. Because another question's  comments think it is via the scope.

*But whatever it is, the problem occurs if the Arduino output is connected to the DAQ's digital input. So it seems I can solve the problem if I can eliminate the interference between the Arduino on the DAQ's input.

Here is more info about the entire system:

Here is the basic diagram of what is inside the metallic enclosure:

Here are some photos:

The mains power entry is a module which is followed by a switch. The mains power entry module has also a filter. Here are the photos and details:

This link is the line filter used the exact model is called "5707.0801.312 - IEC Filter"

This link is one of the six daq boards installed.

The Arduino's 33Hz pulse train output goes into one of the digital inputs of the DAQ. And the spike is causing the DAQ board upset.
It is because if the Arduino output is not connected the DAQ does not get upset.

The spike is generated when a device is switched in the same mains or a surge ect. So we are not sure how it is happening.
The spike is observed by an oscilloscope both at power supplies and Arduino output. Use of an isolation transformer didn't help.

So my aim is to eliminate this spike instead of finding the root cause since we couldn't. It is enough to eliminate the spike only between the Arduino output and the DAQ digital input.

So how about filtering the Arduino output and using a Schmitt trigger?, I tried to simulate the spike and use an RC and a schmitt trigger with hysteresis as:

Signals at input, output and comparator's inverting and non-inverting terminals:

I put R6 C5 to suppress the spike in the system to not to upset comparator, is that a fine way to filter the spike from Vcc? What do you think about the circuit? Any experience with such issues? I can provide more information if needed.

**I would like to add one more point that the USB plug from the metal enclosure system is connected to a PC which is earth grounded:


texts: Why doesn't a short-circuit immediate consume all voltage?

texts: If we assume a short circuit, with zero resistance (not even within the battery), would this 'infinite current' deplete all voltage within the battery? For example, if I "short" a 9V alkaline battery, it will run for about an hour (though the wire gets pretty hot, if not melts) until it depletes all its power. Is this only because the battery has internal resistance, or why does the battery 'keep running'? Additionally, does a battery ever give its Amp-hours or how long it can run?


texts: Investigating RCD nuisance tripping when ACCL changes power source

texts:
My apartment is supplied with 2 sources of electricity: the grid and a generator in the apartments premises. The change over is controlled by an ACCL. The apartment has an 25A ELCB/RCCB with 100mA sensitivity. The power to individual rooms is further protected by an MCB for each room.
When the generator is switched off, the RCD in the apartment trips. This does not happen when the grid fails, but happens every single time when the generator is switched off. The generator supplies electricity to some 200 other houses, and the RCD tripping issue occurs only at my apartment.
Tests I have done so far:

Switched off the MCB for individual rooms one at time. I was trying to isolate if any specific MCB/room has a fault. The RCD failed every time.
Switched off all unnecessary devices when running on generator. Every single device was turned off excluding my internet modem and wifi router. The RCD failed this time too.
Used a multi-meter to check the voltage difference between neutral and earth. It is 0V when running on grid. It was 9V when running on generator. But when I tried to reproduce this for the apartment's maintenance manager, it turned out to be 0V.
Replaced the ACCL and the RCD with new devices of same specification as earlier. The issue persists.

The maintenance manager recommends changing the RCD to a 300mA sensitivity. But I am not convinced without proving the source of the issue. What can cause such tripping? Are there any other tests I can conduct with simple instruments at home (multi-meter)?


texts:
Duplicate question was also asked by me and the current question has different code

I have a PIC32 starter kit and I am making I2C communication with DS1307 RTC. I have used the functions for I2C Communiation described in this document page no- 221. I am using MPLAB 8 with watch window opened and added all the register of I2C in watch window, so that when I debug my code, I can see which register has what value. Following is my code:

#include <plib.h>

#define SYSTEM_FREQUENCY            72000000L
#pragma config FNOSC = PRIPLL       //Primary Osc w/PLL (XT+,HS+,EC+PLL)
#pragma config POSCMOD = HS         //HS osc mode
#pragma config FPLLMUL = MUL_18     //PLL Multiplier 18x Multiplier
#pragma config FPLLIDIV = DIV_2     //PLL Input Divider 2x Divider
#pragma config FPBDIV = DIV_1       //Peripheral Clock Divisor: Pb_Clk is Sys_Clk/2
#pragma config FPLLODIV = DIV_1     //System PLL Output Clock Divider: PLL Divide by 1
#pragma config FWDTEN = OFF         //WatchDog Timer

#define CCLK  (60000000)
#define PBCLK (CCLK/8)

#define Fsck 375000
#define BRG_VAL (PBCLK/2/Fsck)

int main()
{
  mOSCSetPBDIV (OSC_PB_DIV_8);

  OpenI2C1( I2C_EN, BRG_VAL );

  //*********INIT I2C************//
  StartI2C1();
  IdleI2C1();    //This function generates Wait condition until I2C bus is Idle.
  MasterWriteI2C1(0xD0);  //Address of DS1307
  MasterWriteI2C1(0x07);
  MasterWriteI2C1(0x00);
  AckI2C1();
  StopI2C1();
  IdleI2C1();
  //*********INIT I2C END**********//

  //**********SET DATE**********//
  int i=5, j =5, k =5;
  StartI2C1();
  IdleI2C1();
  MasterWriteI2C1(0xD0);
  MasterWriteI2C1(0x04);
  i = MasterWriteI2C1(0x19);
  j = MasterWriteI2C1(0x10);
  k = MasterWriteI2C1(0x09);
  AckI2C1();
  StopI2C1();
  IdleI2C1();
  //*********SET DATE END*********//

  //**********GET DATE************//
  if(I2C1STATbits.RBF == 1)   //if data is available
  {
   StartI2C1();
   IdleI2C1();
   MasterWriteI2C1(0xD0);
   AckI2C1();
   IdleI2C1();
   StopI2C1();
   IdleI2C1();

   unsigned char val1 = 5;
   unsigned char val2 = 5;
   unsigned char val3 = 5;
   StartI2C1();
    MasterWriteI2C1(0xD1);
   val1 = MasterReadI2C1();
   val2 = MasterReadI2C1();
   val3 = MasterReadI2C1();
   AckI2C1();

   StopI2C1();
   IdleI2C1();
}
if(I2C1STATbits.RBF == 0)    //if data is not available
{

}
return 0;
}

For the time being I am just trying to set date and read it back.

1) My first problem is that, when I start debugging, in INIT I2C after IdleI2C1();     I2C1STAT   (register which gives the status of I2C ) gives value 0x400 which means 10th bit is 1 and if we look into the bits of this register then it says:

bit 10:
  BCL: Master Bus Collision Detect bit
  Cleared when the I2C module is disabled (ON = 0).
  1 =A bus collision has been detected during a master operation
  0 =No collision has been detected

So this means that collision has been detected. But i havent send anything then why it is saying that collision has been detected.?

2) MasterWrite() function is running properly, because when ever this command is executed, i can see the change in I2C1TRN register(this displays the transmitted data) and the values of i j k changes to 0 because MasterWrite() returns 0 whenever the data is transmitted successfully. But when my control reaches the GetDate it doesnt enter because no data is available. So my second question is that when my data is transmitted successfully, why I am not getting any data back??

Any Pic experts please help me with I2C communication. Thanks!


texts: torque of locked gear motor vs gearless motor

texts: Do gears increase the torque of locked/stalled motor ?. I understand that in case of rotation of shaft the gears will increase the torque because of transmission to slow rpm. But what makes difference in case of stalled/locked shaft?


texts: Why doesn't it matter if a resistor is before or behind an LED wrt voltage drop?

texts:
I have read that current is always the same within a circuit, but as far as I understood voltage is not. Every electronic part I use lowers the voltage more or less, even simple wires do this. So far, so good.

Now I wonder why it does not matter if a resistor comes before or behind an LED with respect to voltage drops caused by the parts of a circuit.

Supposed I have a very simple circuit:

9V Battery -> Resistor -> LED -> 9V Battery

Also supposed that the LED has a maximum voltage of 3V and 20 mA. So I need to calculate the desired resistor:

9V - 3V = 6V

So I need a resistor that takes 6V out, and since I want 20 mA and current is the same in the entire circuit, it's according to Ohm's law:

U = R * I
6V = R * 0,02A
R = 6V / 0,02A
R = 300 Ohm

Again, so far, so good.

Now, with a resistor taking out 6V this makes sure that only 3V are left for the LED: The battery provides 9V, the resistor uses 6V, the LED gets the remaining 3V. Everything's fine.

What I do not get is why it also works the same way if I have the resistor behind the LED. Wouldn't that mean that we have a battery providing 9V, the LED getting all the 9V, using 3V, and then 6V for the resistor remaining?

Why does this work? Shouldn't 9V be way too much for the LED? Why doesn't it matter if the resistor is set up before or behind the LED?


texts: Do need to solder on the pin headers panels on the edges of a protoboard or can I just attach them without solder?

texts: I have my first circuit on an Arduino Protoboard, and I was wondering if I had to solder the header pins to the board like the other components?


texts: Converting Power/Watts in DC to Power/Watts in AC?

texts: How can we convert Watts in DC to Watts in AC? for e.g A device needs 1A and 12V DC input i.e (1A x 12V = 12 Watts) 12 Watts DC. If we use an AC to DC adapter/converter to generate 1A,12V (12Watts) DC then What will be the AC Power/Watts that we have to input into the device's adapter/converter?


texts: Adjusting the gain on a 4th Order Butterworth Bandpass fIlter gain

texts:
I designed a bandpass filter with the TI filter designer tool but I initially designed with a gain of 40 dB. However, I'd like to reduce the gain to 20dB but I'm having issues doing trying to figure out which resistors to change for the gain ratio. It's supposedly a Sallen-Key Topology. My electronics knowledge is very basic and I'm mainly trying to design a pre-amplifier for a hydrophone to be passed on to an ADC but the gain on my output suffers from two issues:

Amplitude of the AC signal is 7.8V pp but my ADC can only take up 3.3V.
ADC is also unipolar but I have negative voltages in my signal for this I'm thinking of using a summing amplifier.

Can I adjust the gain by changing resistor values, or is it a bit more complicated than that?


texts:
The real case I am working on: I need to connect a CZT (Cadmium-Zinc-Tellurium) detector to a custom ASIC input (a Charge Sensitive Amplifier of which I do not know the input impedance, if that matters). The recommended way of doing this is through the use of an AC-coupling circuit. I need to dimension the circuit.

The theory: the most simple and straightforward way of connecting the detector to the ASIC would be a capacitor C. In the image below, the current source represents the detector, C is the decoupling capacitor and the OpAmp represents the ASIC (values of I and C are meaningless)

simulate this circuit – Schematic created using CircuitLab

I have a good understanding of why we need it and why it is done like that (or at least, I think I do). My doubts come from an implementation I have from another project.

In a different project, using the exact same detector and ASIC, the people responsible for the project adopted the following solution:

simulate this circuit

The values are the real values used in their schematic.

Questions:

1) why do they use a resistor?

2) why is the resistor placed before the C and not after? If the AC-coupling is basically an high-pass filter, shouldn't it be placed after?

3) what would be the procedure to calculate those values, in any case? My confusion here is deriving from the fact that the input signal is an "unknown" by itself (it can be approximated by a "spike", if you want).

Thanks!


texts:
I've encountered this resistor R12 while trying to understand how a board is working. It seems to be much bigger than the other SMT components and basically just looks like a flat metal tile without symbols.

Do these kind of resistors have a specific name, or present a certain best practice for appliances?

My assumption is that this might be a dedicated shunt for a higher current, but the lack of any symbols got me confused.

Update to provide more context

The device being examined is a socket extension that can measure the current going through the mains. Besides this resistor, the component I wasn't able to identify was this little guy:


texts: Clamping diode current in flyback converter

texts:
In an RCD clamping circuit configuration of flybacks,
Could anyone explains to me how the following relationship is derived ?
$$ \ {I_d}=I_{peak}  \frac{\Delta t - t}{\Delta t}  $$
The equation describes the current circulating through the clamping diode when it conducts (When the drain voltage hits the clamping voltage)
The circuit and graphs are shown below:


texts:
Been using Altium and multi sheet projects for a while.
My latest project involves a lot of signals so I'm trying to keep things tidy using lots of labels, ports, busses.

So I have a bus for enable signals going from the microcontroller sheet, to the stuff that needs to be enabled. And the same for fault conditions, current senses and so on.

I have like 4 of the same for different busses.
Now Altium keeps saying that all the NET labels on the port side are floating.
Nothing I can do about this: I tried everything I could think of, but still I have some 20 floating nets.
In the next pic you can see the multi sheet connections I made: a repetition of a sensor sheet, all 8 of them hooked on a bus, and the bus going to the microcontroller.

So I haven't got anything floating really, yet Altium still sees it that way.
Why is that?


texts: STM32F407 FSMC & ILI9341 – 8 bit bus width works, 16 bit doesn't

texts:
I'm trying to use TFT display with ILI9341 8080 16 bit interface with STM32F407 via FSMC. I'm using HAL. To explain a bit more, for ILI9341 command registers only lower 8 bits of the bus are used, full 16 bit bus width is only used for transfer of image data (in RGB 565 format). I tested the program before with identical display configured with 8080 8 bit interface and it worked flawlessly.

I have image data in MCU memory in uint16_t format and use

HAL_SRAM_Write_16b

for transfer of image data and

HAL_SRAM_Write_8b

for transfer of commands and command parameters.

Now, when I select

hsram1.Init.MemoryDataWidth = FSMC_NORSRAM_MEM_BUS_WIDTH_8;

everything works fine, only image data (colours and resolution) are wrong of course, because ILI9341 has only lower 8 bits of data (blue and half of the green bits) and upper 8 bits are zero. As soon, as I select

hsram1.Init.MemoryDataWidth = FSMC_NORSRAM_MEM_BUS_WIDTH_16;

display shows black and grey stripes for a second and then just goes white – error state.

I use A16 for command / data selection, therefore address of command memory is 0x60000000 and data memory 0x60010000, hopefully same for 8 bit and 16 bit bus width?

Question: Can anybody explain to me, how data transfer in FSMC_NORSRAM_MEM_BUS_WIDTH_16 mode works, more precisely when I use HAL_SRAM_Write_16b (or HAL_SRAM_Write_8b) in this mode, if the data are sent one 16 bit (or 8 bit aligned to lsb) word per time frame, or if the MCU somehow distorts / combines them.


texts: Series and Parallel together for 3 Solar Panels?

texts:
I don't know who to ask about this. I know it works, but don't know if it's a good idea or a safe idea.

I have 3 solar panels, 240W each.

I have a need for 720W max and 60V.

I thought. hmmmmm, put 2 panels in parallel, and then put that "parallel group of 2 panels" in series with the 3rd panel.

This gives me my required voltage, and watts but is this a really bad idea or is it perfectly safe.

All panels are the same type, model manufacturer etc.


texts: Connecting Toslink TORX179L optical receiver directly to S/PDIF coaxial input

texts:
My goal is to convert optical audio signal - Toslink - to S/PDIF coaxial input signal. The frequency is up to 96 KHz. I'm thinking about Toshiba TORX179L optical receiver. According to the datasheet, the output of TORX179L is 0,2V low, and 4V high level voltage. My question is - do I have to use some repeater like 74HCU04 here:

Or can I directly connect TORX179L to S/PDIF coaxial input? The circuit will be built inside the player.


texts: amplify/increase current from 9v battery

texts:
I have a working circuit that generates a signal (a range of slow and fast tones) and sends them to a speaker.  I tried to switch to a piezo driver and speaker and was successful using the MAX9788 as the driver, however I was unable to make it loud enough.

The MAX9788 requires 2.7V to 5.5V.  If I supply it with 5V from a power supply and use a regular speaker then I am able to create the desired volume during which the power supply reads between 250mA to 850mA depending on the speed of the tone, i.e. steady and slow to very fast.

My problem comes from when I supply my circuit with a 9V battery and use a linear DC-DC regulator to send 5V to the MAX9788 (I am using a L7805).  I am able to hear the slower tones but at a much lower volume and never the faster ones. I have been able to increase the volume using a voltage follower with a darlington pair, my current during this time has never exceeded 50mA.

I believe my mistake was using a linear DC-DC regulator and my next step is to use a buck convertor to hopefully get more current to the MAX9788.

TLDR - my systems works if I supply the MAX9788 with a power supply but not with a 9V.

My question is will this work? is there a better way to see the current I need on the driver using a 9V battery?


texts: What is the relation between beamforming design and user scheduling in massive MIMO systems?

texts:
This may seem like a basic question, but since I am a nonexpert trying to do some collaboration with people working in this field, I need to understand the two concepts.

As I understand, beamforming is the process in which the transmitter chooses a direction to concentrated its transmitted signals on, while user scheduling means to choose a subset of all users to serve. Is this right? Which one comes first? Do we first decide which users to connect and then form a beamforming plan, or do we have a beamforming plan first and then do user schduling?


texts: Power supply needs BASED on usage plus 35%

texts:
I'm DIY'ing a RV van. What is the best power supply setup for a 8kW maxed out load plus 30%? I realize that this is a lot of power. I am trying to keep it self-contained and self-powered.
Current Power items:
4kW Peak Inverter(2k steady)
1kW Peak Inverter(500 steady)
Two-Sealed lead acid farm batteries
100W solar panel
100A MPPT Charge controller
10A Battery Maintainer
200/300A Fuses (ON ALL BATTERY CABLING)

Intended 120V Power Usage Items:
-Mini Fridge: 4A Start/1.8A Run @ low *24hrs
-Coffee pot/oven: 15A(1500W)*3hrs
-LCD monitor: 2.1A(200W)*12hrs
-Laptop: 7.7A(AC plugged in)*10hrs
-TV Box: 2A*7hrs
-Hotplate: 9A*3hrs
-Corded drill: 5.5A(used when necessary only)
-Major power tools: x4 12A(used when necessary only)
-AC Unit: 4A(455W)*10hrs (hot days only)

My watt calc runs just under 8kW with all items and tools plugged and running. 5kW max appliances/electronics and 3.9kW "basic items needed" running at 80%.
A) 1k inverter: TV, monitor, laptop, water pump / heater.
B) Appliances and tools

Could someone please suggest reasonable case battery setup to accomplish this?


texts:
I have a APC 1000VA BR Smart UPS.I have noted that the UPS Produces a Humming Sound when running on Battery Power.But my older a normal 500VA UPS(not from APC) seems to produce far lesser humming.The cannot say the humming is loud but you can hear a grrr+hmmm at mid  frequency coming from the UPS.Is this normal for a stepped sine wave UPS.

I have a DSP Sine Wave Inverter at home(powering the house).I have gone near it kept my ear close to hear the sound coming from it(Very less sound)

Why is my UPS Producing such sound.Is this normal.


texts: serial communications and on/off voltages

texts:
I'm writing a program in C to talk to a modem via an rs-232 serial port. Unix supports 6 pinouts in the serial line, including TXD (Transmitted Data), RXD (Received Data), DCD (Data Carrier Detect), DTR (Data Terminal Ready), CTS (Clear To Send), and RTS (Request to Send). Now according to the below documentation, RS-232 actually comes in 3 different flavors (A, B, and C) with each one defining a different voltage range for the on and off levels. The most commonly used variety is RS-232C, which defines a mark (on) bit as a voltage between -3V and -12V and a space (off) bit as a voltage between +3V and +12V

http://www.cmrr.umn.edu/~strupp/serial.html

Why is an on bit defined with a negative voltage and an off bit defined with a positive voltage? Shouldn't it be reversed?


texts: In general, is 5V CMOS compatible with 5V TTL?

texts: Can you in general interface the two without issue?


texts: How does this timed fan controller work?

texts:
My bathroom fan controller recently started misbehaving, so I pulled its PCB out. This is what I found.

simulate this circuit – Schematic created using CircuitLab

LIVE/NETURAL are the 230 AC mains. I think I have a fairly good grip on what's happening here: the upper part of the system is there to generate 5V for the lower part. The lower part is a 14-bit counter whose most-significant output controls Q1 and therefore TRI1. R10, R11, R12 and C6 together with the invertors integrated in the IC provide a clock, whose frequency can be set by R11. D5 stops the clock once Q14 goes high. In other words, the circuit cuts off the power to the fan after a delay selected by R11.

Now, the user can restart the fan by pressing SW1. I guess the idea is that the switch pulls RESET on the IC high, thus clearing the counter. However, the divider formed between R7+R8 and R9 will make the voltage on RESET only 0.21V! (And yes, I've rechecked the resistor values like 100 times. The two resistors say 624, the R9 says 653; they're all 1206 SMDs.) Yet, somehow, it works (at least it used to).

How?

Furthermore, I've not been able to figure out the intended function of some of the components. I'm guessing that R1 and R2 are there to provide a discharge path for C1 if the mains are disconnected. But what are R3 and C4 for?


texts:
I have the LM111P voltage comparator (datasheet.)

I am learning my ropes with electronics, so I am moving thru the easiest topics to more complicated ones. If I understand correctly, when I provide higher voltage to the non-inverting input of the comparator and lower to the invering one, I should get around source voltage at the output. When I do the opposite (lower on the non-inverting and higher on inverting) I should get nearly "ground" voltage.

My source voltage is 9.14V. The emitter (pin 1) is connected to ground, as well as pin 4 (Vcc-), while pin 8 (Vcc+) is connected to source "+". I also have a LED in series with protective resistor (470) connected to the collector (pin 7) to visually verify if there is indeed voltage at the output.

When I use voltage divider (10k, 1k), I provide the noninverting input with around 8.31V and inverting input with another divider (1k, 10k) with around 0.83V. The comparator works as intended - LED shines (with measured voltage almost equal to the source voltage).

I am not sure if it's related to the datasheet or I understand something wrong, but at the worst case, the switching voltage difference should be equal to around 100mV. However, when I connect different dividers:

1k, 10k to the non-inverting, getting around 0.83V,
1k, 22k to the inverting, getting around 0.42V,

and measuring the difference between non-inv and inv inputs I get (obviously) 0.83V - 0.42V ~= 0.41V, so there is indeed a voltage differential there. Even if that is the case, the comparator no longer works even though 0.83V > 0.42V - I get around 0.77V at the output.

I will be grateful if somebody can explain why it is the case, when I've read that comparators are really sensitive to even minimal voltage differences. My first though is that maybe the current is really low and that's why it doesn't work, but that's just my guess.

I attach the "template" of the circuit - it may not be 100% right (probably messed the connections of the amp or resistor placing, but I just wanted to show the principle of "working" case, just for You to see what I am dealing with (I used a part with number LM108A, because I couldn't find my part in the library - assume it's LM111P)).

EDIT: I've added some photos to show my circuit and measurements (too big to upload directly).

inv - GND voltage 8.33V

noninv - GND voltage 8.77V

The circuit:


texts:
I am working on an oscillator circuit. Here's the diagram [See below for output diagram]:

Since it's a bistable circuit I will have to assume two separate conditions that each transistor might be in. Here's my analysis.

My solution:

First, I assume Q1 is saturated and Q2 is cut-off. Therefore I will go and simplify the circuit and prove if my guess was true. Then I will consider the other case and work it out. I just don't want to go through equations I just let you know what I got on paper:

Case I
..........
Part     State
Q1       Saturated
Q2       Cut-off
..........

Results:
I(R1)=1.79mA
V(B1)=Vout=2.39V
V(C1)=2V
V(E1)=1.1V

About Q1 since it has just started to charge up it's certainly in cut-off. As you see my initial assumption looks correct and Q1 is in saturation. Now let's consider the other situation where I assume they change states:

Case II
..........
Part     State
Q1       Cut-off
Q2       Saturated
..........

Results:
V(C2)=Vout=0.2V
V(C1)=3V

If you look my analysis sounds more or less reasonable. The question that I have is when C1 charges up to 3V what would happen to it so that it suddenly discharges to 2V?

Diagrams

A.The capacitor voltage: The green shows the upper end.

B.The output voltage.


texts:
Most Wifi 802.11 standards use OFDM to achieve high data rates wirelessly. However, I was told OFDM is not suitable for uplink as it requires expensive and inefficient amplifiers which are not applicable in phones. Hence, LTE only uses OFDMA in downlink and SC-FDMA in uplink.

What is used in Wifi uplink communication? If OFDM is used, why is suitable here? If not, what else is used?


texts: How to determine value of t when plotting a signal

texts:
I'm trying to implement this model inatlab:

I know that Ri = 2 and Si = -0.05+3j, ignore n(t). I want to plot the signal in time response, this is what I got so far:

   Fs = 1000;                   % samples per second
   dt = 1/Fs;                   % seconds per sample
   Time = 10;                   % seconds
   t = (0:dt:Time-dt)';         % seconds
   y = 2*exp((-0.05+3j)*t);
   figure;
   plot(t,y);
   xlabel('time (in seconds)');
   title('Signal in Time response');

The problem I'm having at the moment is when I'm plotting this in Matlab, I get a warning saying the imaginary part of the complex is being ignored but I'm still able to get a graph.

If my approach is correct, how would I determine the time value?


texts: Substituting multiple resistors with one

texts:
Hi am a beginner in Electronics and I have been working with a LED project. I have a requirement where i need to connect 6 LED's in a way shown in the below diagram. Forward voltage of these LED's are 3v and current consumption around 20mA.

simulate this circuit – Schematic created using CircuitLab

But I felt the above schematic is so bulk due to the presence of resistors, So I am thinking to replace the above one with something like this below.

simulate this circuit
Am i doing it right in simplifying the circuit? Kindly advice.


texts: How do I do indirect addressing in PIC ASM?

texts:
On my 16F628A's I want to iterate of a predefined sequence of values. How do I do this?

In C, I would do something like this:

char vals = {22, 10, 34, 16};

char id = 0;

port = vals[id];
id++

It's the 'vals[id]' that I haven't figured out.


texts:
I have a working 500kbps CAN bus between an Arduino Uno and a RaspberryPi. Both are connected to MCP2515/TJA1050 boards from Amazon and communicating over SPI. The RaspberryPi dumps the CAN data via candump without any issues, and both devices are able to action the data in the CAN frames.
No issues here...
But, I am trying to integrate another CAN device. The new device is a black box, so not sure what controller/transceiver is used, but this shouldn't matter (right?) as both devices implement CAN 2.0b (confirmed). The CAN waveforms of this device also look correct.
When I probe the bus via an oscilloscope, CANH and CANL look correct, idling at 2.5V and changing to ~3.5V(CANH) and ~1.0V(CANL) in dominant state.

When I connect the new device to my original bus, the whole bus stops communicating and the waveform looks mega weird on the scope. Nothing like a CAN frame.
Any idea what's going on in the below waveform when I connect the new device to my original bus?


texts: 7 segment LED display not working when using common pin as cathode?

texts: I am trying to wire up a 7 segment LED display but when I connect the common pin to ground and the LED pins to V+ the display doesn't work. However when I use the common pin as an anode and connect it to the positive rail and use a lower voltage for the LED pins then it works, how do I make it work with the common pin as a cathode


texts:
Does anybody have an idea how to safely get 7-12V from an ordinary LCD computer monitor?

I wish to control the monitor via a microcontroller after the fashion of the guide at lucidscience. I'd like to have the microcontroller draw its power from the monitor, rather than add another power source. (The arduino needs 5V to run at the clock speed prescribed by the guide, so I understand that to require 7-12V preregulated.)

Perhaps I could simply stick a multitester here and there, but I'm green enough that that looks pretty hopeless.


texts: Two diodes connected in opposed way show different results (simulation vs physical circuit vs simulation)

texts:
I am confused about this circuit found in Electronic Devices and Circuit Theory By Robert Boylestad 10th Ed.
1.
I don't understand why D1 (left diode) has a Vd1 = 0v in equivalent circuit:

When I simulated on Proteus ISIS the polarization voltage of D1 is 0.43V:

Even when I made the physical circuit (2 diodes 1N41004,
1 resistor of 73Kohms "Note: I dont have a value shown in the problem but I use this as reference").

D1 shows a polarization voltage of around -0.5V.

Could someone explain to me which analysis is correct?


texts:
I have a question regarding the relationship between open-loop-gain and supply voltage. Using op270 as an example:

We need to operate this device at +-5V.  The datasheet has a plot (Figure 19) which shows Open-Loop-gain (in units of V/mA??) which decreases linearly as the supply voltage drops (from around 3000 at +-18V to 100 at +-5V).  Is this in any way related to the GBP of the device? I'm confused by the V/mA units here.


texts: Different ways of using DSP slices in Spartan 6 FPGA

texts:
I am reading the Spartan 6 DSP slice user guide, and I need to use the DSP slice in a project of mine.

I stumbled upon this question, which basically suggests 3 ways of using the DSP slices

Inferring the DSP slice
Using Core generator
Using the RAW DSP instantiating template

The second option is almost self explanatory, but I somehow don't feel like using it, since it feels somewhat superficial. I am interested in using the first and third options, since those options are the most customisable, but I am having a hard time understanding where to start.

These are the questions I have on my mind :

What are the different ways in which you can infer a DSP slice in your design ?
Where do I find the RAW DSP instantiating template? I have been googling for it, but I didn't find a definitive guide to it.
Building up on my second question, there are a lot of xilinx documents one can read to get information on a lot of things. Since I am a noob, I always get confused about what to read, and I always like to have a mindmap of what all is out there, and so what options I have. Is there a place where all the xilinx documents with their description are listed, or what all documents I can refer for a particular application ?


texts:
This question is related to an electronic devices course. The unit is on diodes.

What do we call the potential difference of the electrical field across the depletion region?


texts: Bus interface for short distances, many device data exchange - CAN, RS485? + characteristic impedance and media capacitance

texts:
I ran into some troubles trying to design a wired bus which will connect in about 64 testing devices. My first choice of mind was CAN bus, known of it's reliability and low EMC interference. However, during my research, I have discovered that there is limitation of minimum distance between CAN nodes, related to load capacitance and media capacitance: http://www.ti.com/lit/an/slla270/slla270.pdf

The nodes are connected through PCB traces and connectors, I have estimated media capacitance of 0.62 pF/cm (single 1 mm width trace to ground plane through 2.1 mm FR-4, is it right way to calculate?) and TJA1040 transceiver has input capacitance of max 10 pF.

My bus layout is:

Node to node distance is about 60 mm. From the graph, minimum distance is about 180 mm.

I also have some problems understanding bus characteristic impedance. In my design, I can manipulate CAN_L and CAN_H traces width and spacing, minimum width and spacing is 0.5 mm. With 2.1 FR-4 thickness, trace width of 1 mm and spacing of 0.5 mm (possible to manufacture for me) I can achieve 120 Ohm differential impedance, which is.. required, yes?

  CAN Bus is a differential bus. Each differential pair of wire is a transmission line.Basically, the terminating resistor should match with the Characteristic Impedance of the transmission line to avoid reflection. CAN bus have a nominal characteristic line impedance of 120Ω. Due to that we are using typical terminating resistor value of 120Ω at each end of the bus.

I am asking this question because I wonder how it's (differential impedance) related to media capacitance. If I could manipulate media capacitance, I could lower minimum distance and maybe it would work with CAN.

How I calculated media capacitance:

Differential capacitance:

If there's no possibility to make it work with CAN, what serial interface would you suggest instead of? Would RS-485 be better choice?


texts: Crystal oscillator replaced with exact frequency for clock?

texts:
I'm repairing my Nintendo Donkey Kong arcade PCB and I have no pulse when tested with my logic probe. I found out that the crystal oscillator (2 pin HC-18U) was not connected to the board, since the legs have rusted completely and broken. The 2 pin crystal is a 61.44 MHz HC-18U model. It generates the clock for the Z80 processor.

Can I use a crystal with a different frequency, without damaging the components or affecting the game?

I can't find any two legged crystals, only 6 legs flat VCXO type... could that work?

Thanks


texts: STM32F407 Discovery Board DCMI to SPI Output

texts:
I am currently attempting to use a STM32F407 Discovery board to display images captured with a OV2640 CMOS detector on a ILI9341 2.2" TFT SPI LCD.  My goal right now is to take a single snapshot and display it on the LCD.  As I understand, an image must be passed through the DCMI to the DMA2 Stream 1.  From DMA2 it can then be transmitted to the SPI ports where it can send the pixel data to the LCD.
However, I am quite confused on how to facilitate the DMA transfer to the SPI interface. Once the data is received in the DMA, is it stored under a specific memory address which I can access?

Does anybody have any methods for transferring pixel data from DCMI -> DMA2 -> SPI1? I have been stumped by this for quite a few days and cannot find any resources online which explain this transfer.


texts: Can I use a single type of capacitor for all decoupling ( 1uF and 0402 )?

texts:
In the past I've tried to use 10nF (0.01uF) and/or 100nF (0.1uF) capacitors for decoupling ICs and micro-controllers.

However, I've heard that when using physically small capacitors (for example 0402), the capacitance of the capacitor doesn't affect the frequency response, and therefore it's best to just use the largest value you can get.

Therefore, I was wondering if it's a good idea for me to just buy a lot of 1uF capacitors in 0402 packaging and always use one of these going forwards (is 1uF too high?).

Specifically I was thinking about this one:
http://datasheet.octopart.com/CL05A105KP5NNNC-Samsung-datasheet-26589000.pdf

It's 1uF, 10V and 0402, it also works up to 85 degrees celsius and is made by a brand I've heard of. It's also pretty cheap at 0.5 cents each.

I'm interested if there's any reasons I'd need other values, or if this is a good idea. Additionally, should I stretch to 5uF in 0402 size? Is there a limit? (I can't solder smaller than 0402.)

Thank you.


texts: Why do LCD Screens ripple through cameras?

texts:
I noticed that when taking pictures of an LCD screen (thank you, laziness to print), that while I look at the LCD screen through the cell phone camera, the screen has both 1) Ripples and 2) Moving waves.

1) You can clearly see in the picture below:

2) You can see them when you look through the camera (try for yourselves) but you cannot take pictures of them. I've noticed two things about this wave:

It follows a certain axis. If you tilt your cell phone horizontally, they will also tilt horizontally.
They move at various speeds. If you slowly move your cell phone closer to the screen, these waves will alter speeds, going very slowly to very fast. The ripples also change dending on the distance, and have different shapes and patterns. This shape appears a lot (I couldn't take a good picture of it)

So my question is: What is going on? What explains all of this? What are these ripples and waves? I'm guessing polarization is probably the phenomenon involved, but I have no clue how.


texts: How to wire/interface a 4x3 membrane keypad

texts:
I followed this example to wire my keypad to my STM32F4 Discovery board. However any way I read data on the pins I keep getting same data which leads me to believe I wired something wrong.

Here is the image how I had it wired:

I the red line (+) on the breadboard is wired to a +5V pin on my STM32F4 and the blue one (-) is wired to GND on my STM32F4 board.

The first 4 wires are for rows they are wired directly yo + line and right after them there are wired wired to pins from 4-7 like the image bellow shows:

I also tried it by now wiring the keypad to +5. Anyhow I keep getting the following output from my pins: 1 1 0 1 1 1 1 Meaning all but Pin 3 are returning 1 (High).

As far as code goes I initialize all pins for INPUT so I'm reading the value from the PINs. I have Pull UP/DOWN resistor set to NOPULL. However it's always this output.

What is the proper way to wire/interface these keyboards ?

Expanded question:

I wired all 7 pins to my GPIO pins.
- I set all 4 rows to HIGH 1
- I set all 3 columns to LOW + PULL DOWN + Input

Now when I read state of all pins I get: 1111 for the output pins and for the input pins I get 000 and when I press a button on the keypad the corresponding column make one of the 000 to 1.

The problem is this only tells me which column is selected how to I find out which row is selected if they are all set to 1.

My code:

void start_clocks();
void init_outputs();
void init_inputs();

volatile int a, b, c;
volatile int e, f, g, h;

void main(void)
{
  // Start clocks
  start_clocks();

  // Configure outputs
  init_outputs();

  // Configure inputs
  init_inputs();

  // Configure abc
  a = -1; b = -1; c = -1;

  e = -1; f = -1; g = -1; h = -1;

  while(1)
  {
    a = GPIO_ReadInputDataBit(GPIOE, GPIO_Pin_11);
    b = GPIO_ReadInputDataBit(GPIOE, GPIO_Pin_9);
    c = GPIO_ReadInputDataBit(GPIOE, GPIO_Pin_7);

    e = GPIO_ReadInputDataBit(GPIOB, GPIO_Pin_13);
    f = GPIO_ReadInputDataBit(GPIOB, GPIO_Pin_11);
    g = GPIO_ReadInputDataBit(GPIOE, GPIO_Pin_15);
    h = GPIO_ReadInputDataBit(GPIOE, GPIO_Pin_13);
  }

}

void init_inputs()
{
  GPIO_InitTypeDef Keypad;

  Keypad.GPIO_Pin = GPIO_Pin_11|GPIO_Pin_9|GPIO_Pin_7;
  Keypad.GPIO_Mode = GPIO_Mode_IN;
  Keypad.GPIO_OType = GPIO_OType_PP;
  Keypad.GPIO_PuPd = GPIO_PuPd_DOWN;
  Keypad.GPIO_Speed = GPIO_Speed_100MHz;

  GPIO_Init(GPIOE, &Keypad);

}

void init_outputs()
{
  GPIO_InitTypeDef Keypad;

  Keypad.GPIO_Pin = GPIO_Pin_13|GPIO_Pin_11;
  Keypad.GPIO_Mode = GPIO_Mode_OUT;
  Keypad.GPIO_OType = GPIO_OType_PP;
  Keypad.GPIO_PuPd = GPIO_PuPd_UP;
  Keypad.GPIO_Speed = GPIO_Speed_100MHz;

  GPIO_Init(GPIOB, &Keypad);

  Keypad.GPIO_Pin = GPIO_Pin_15|GPIO_Pin_13;

  GPIO_Init(GPIOE, &Keypad);

  GPIO_SetBits(GPIOB, GPIO_Pin_13);
  GPIO_SetBits(GPIOB, GPIO_Pin_11);

  GPIO_SetBits(GPIOE, GPIO_Pin_15);
  GPIO_SetBits(GPIOE, GPIO_Pin_13);
}

void start_clocks()
{
  // Start clocks for GPIO B and GPIO E
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOE|RCC_AHB1Periph_GPIOB, ENABLE);
}


texts:
Years ago, I saw a book on how to put together a homebrew Motorola 68000 computer.  One of the specific things the book talked about was grounding DTACK*, to make a very messy asynchronous bus design into a fully-synchronous, very simple design.

Try as I might, I can't find any reference to that book.

Does anyone recognize it?


texts:
I'm dealing now with the different types of time responses of electromechanical relays: instantaneous, definite time lag, inverse time lag, and inverse definite minimum time lag.

My question is: What's the difference between the last two time response? What are the advantages/disadvantages ? Is it "bad" to have a definite minimum in an inverse time lag delay?


texts: Reverse Engineering a transmitter circuit

texts:
This circuit is from a radio transmitter electric gate keyfob. -> http://www.easygates.co.uk/product_info.asp?ProductID=340

I want to make my own keyfob.

How would I go about finding or creating a circuit diagram for this? I've tried to search for the main chip but couldn't find anything.

Cheers


texts: Help with complex power and power factor correction problem

texts:
I'm having a bit of trouble trying to understand what is being asked of me in a relatively basic circuit theory question involving complex power and power factor correction.

Now, part (b) and (c) seem easy enough to answer given enough information but I cannot figure out whether I'm understanding (a) right. Without knowledge of the power S2 drawn by the corrective device, I cannot see how I can determine the PF (power factor) of the source let alone its total power delivered S = S1 + S2. Is it presumed for (a) that only the motor is drawing power here?


texts: Parallel circuit not working as expected

texts:
I have this setup,

simulate this circuit – Schematic created using CircuitLab
There is also a button connected to the Arduino and every time the button is clicked the arduino cycles 3 levels of brightness on the LEDs. The problem is that when the LEDs are at full bright the Arduino no longer has enough voltage to run ~3v down from ~4v when off and so becomes locked at full brightness.

From what I have learned in physics I thought that when a circuit was in parallel the components acted as if they were independent of each other however this is not what I see here.

How do I drive both the arduino and LED strip with the same battery? Is it possible the battery is not supplying enough current?


texts: How to add Mouse Bites or V-Groove to PCB In Altium?

texts:
I know mouse bites are more used to snap off one of many of the same boards in a panelized array, but I'm hoping to put mouse bites to snap off part of the same board if that's possible.

Is there just a standard for how far apart you put centers of drill holes?  Is there a standard diameter for the holes?

V-groove could work as well.


texts: How to fully discharge a battery to determine capacity

texts:
Hey I had another post asking this question but I dont think my question was answered correctly due to me not providing enough information so here is an update.
I am conducting an experiment trying to expiramentally determine the capacity of a lithium ion battery (380mah 3.7V). For this I am trying to discharge the battery under a constant current and time how long the battery would last (so of the current was 20mA and the battery lasted 2 hours I could determine that the capacity was 40mAh). Now on the data sheet it says that to test this I need to discharge the battery at 0.2C which is about 76mA. The reason I decided to use diodes was because I could see when the battery dies and stop the timer accordingly although many people told me to use resistors instead. My inital thought is to get 4x20mA diodes and connect them together in parallel and time how long they will work for. Would this approach work, if not could you guys suggest something. If really new to this field but interested about this topic. Thank you.


texts: Tolerance of voltage dividers with different values for R1 and R2

texts:
If I have two 1k resistors rated at 1% fed by a perfect 10V source then what is the otuput guaranteed to be? 5V ±1% or 5V ±2% or some other value?

I can work out this case easily, assume that R1 is at the minimum, R2 is at the maximum, then the output is 4.95V; for the reverse case it is 5.05V, which is ±1%.

But is there a general rule for differing values? What about differing tolerances - what if one resistor were ±0.1% and one ±1%. While you can work it out by plugging values into the voltage divider formula, I'm looking for some general rule of thumb.


texts: How to find Real circuit diagrams used by computer industry consisting of NAND Gates or NOR Gate

texts: It is said that the circuit diagrams used by computer industry consisting mainly of NAND Gates or NOR Gates. (as oppossed to the text book circuit diagrams which contain the cicuit diagrams with every kind of Gates). Here is my question: Where can i find those real circuit diagrams used in the computer industry on the web (using solely or mainly NAND or NOR Gates)?


texts: How to troubleshoot low-voltage home lighting system from 50s

texts:
My home, built in the 50s, has a Sierra low-voltage lighting system, where low-voltage 24DC switches control relays that power the normal 120AC lights. In the last week, the switches have failed intermittently, and I'm not sure how to diagnose the problem. Different switches fail at different times, so it seems like it must be a problem with the transformer, since it seems unlikely that multiple switches and/or relays would all suddenly go bad at the same time.
This is a rough schematic of how the system is wired:

Assuming that the problem is with the transformer, I took a picture of the transformer box: (If anything is unclear from the picture, I will gladly take another for you. Just tell me what you need to look at.)

If I understand correctly, the parts in the box are...

A. Transformer
B. Fuse
C. Capacitor?? (If so, that's not in the schematic.)
D. Rectifier
E. ??? in-line something or other? Maybe just a fancy connector?

I really just have two questions:
First, how should I go about diagnosing my problem? (I have an automotive multimeter that can test voltage, resistance, connectivity, etc.)
Second, is there a simple way to bypass the system to get a relay to turn on and off in the meantime. (I have a few lights in the house that are stuck on at the moment, and I guess I'll just leave them on all night.)
Edit 1: Failures seem to go away after waiting for a while. After writing this question, I went out and both of the switches that were failing before turned off with no problem.


texts:
How does one deduct the number of poles from a Bode plot? Is it further possible to decide where the poles are? I have not understood this concept even though there is so much focus on Bode plots in engineering.

E.g. for the Bode plot below?


texts: Finding the transfer function of an op amp filter circuit

texts:
I have the following third order filter circuit:

simulate this circuit – Schematic created using CircuitLab
And I know that the transfer function looks like:
$$\mathscr{H}\left(\text{s}\right)=\frac{1}{\alpha_1\cdot\text{s}^3+\alpha_2\cdot\text{s}^2+\alpha_3\cdot\text{s}+1}\tag1$$
Where:
$$\alpha_1=\text{C}_1\cdot\text{C}_2\cdot\text{C}_3\cdot\text{R}_1\cdot\frac{\text{R}_2\cdot\text{R}_3}{\text{R}_2+\text{R}_3}\cdot\left(\text{R}_1+\text{R}_2\right)\tag2$$

$$\alpha_2=\text{C}_1\cdot\text{C}_2\cdot\text{R}_1\cdot\left(\text{R}_1+\text{R}_2\right)+\text{C}_2\cdot\text{C}_3\cdot\text{R}_3\cdot\left(\text{R}_1+\text{R}_2\right)\tag3$$
$$\alpha_3=\text{C}_1\cdot\text{R}_1+\text{C}_2\cdot\left(\text{R}_1+\text{R}_2+\text{R}_3\right)\tag4$$

But how can I use current node analyses to find this transfer function (assuming an ideal op amp)?

My work:
I wrote the current node equations:

$$\text{I}_1=\text{I}_{\text{R}_1}+\text{I}_{\text{C}_1}+\text{I}_{\text{R}_2}\tag5$$
$$\text{I}_2=\text{I}_{\text{R}_2}+\text{I}_{\text{R}_3}+\text{I}_{\text{C}_3}\tag6$$
$$\text{I}_3=\text{I}_{\text{R}_3}+\text{I}_{\text{C}_2}\tag7$$
$$\text{I}_4=\text{I}_{\text{C}_3}\tag8$$
$$\text{I}_5=\text{I}_4=\text{I}_{\text{C}_3}\tag9$$
And of course I know that ideal op amp equation:
$$\text{V}_+=\text{V}_-\tag{10}$$

But now I do not know how to continue using the voltages at those nodes:


texts: How can two separate devices send clock data to a shift register IC?

texts:
I'm using a microcontroller to clock a byte into a 74HC595 shift register and latch it. It then sends a signal to the other device which send 8 clock pulses when it is ready to receive the byte.

So my question is can the two devices share the one shift register clock pin? Should they be insulated from each other?


texts: DIY ATX PSU turns off when attaching load on 12V rail

texts:
I want to convert my old ATX power supply to a simple bench supply for 12V devices. On the label it says it's a 300W PSU where I can use 264W on the 12V rail (see image below).

https://imgur.com/xpOqHZa

Therefore I soldered all cables with the same color together and wired the green (PWR_ON) one to any ground cable.

If I plug the cable in, the PSU starts and you can hear an annoying whirring. I need to mention that the PSU does NOT turn off automatically when there is no load attached.

Then I connect (just to test) a 12V 55W car lamp to the 12V (yellow) cables and the PSU turns immediatly off (the lamp is flashing for half a second). To keep it running again, i need to remove the cable, turn the switch on/off or reconnecting the green cable with the ground.

I measured at which amps the PSU shuts down - that's roughly 50mA @ 12V.

Interestingly, it doesn't make a difference whether the 12V car lamp is attached before i connect the cable or not. Furthermore, if I attach a 5V lamp at the red wires everything works and the PSU stops whirring.

The brown 3.3V sense cable is wired to the orange 3.3V cables.

I also tried putting a 25 Ohm resistor between the red 5V and the black (GND) cables - nothing changes.

For me it seems that the 12V rail is faulty ... do you have any ideas?

Here is an overview of how it looks like: https://imgur.com/DnTi61G


texts:
Hello,
I need to identify two SMD Elec. caps. But I can't find specs that would match the marking on a components.
Top left cap is - 35 10 16f. looks like 35V 10μF 20% Kemet but not 100% sure.
https://ru.mouser.com/datasheet/2/212/KEM_A4002_EEV-1101492.pdf
Bottom right cap is - 47 4s. A23 looks like it Panasonic 4V.DC 47μF.
https://ru.mouser.com/datasheet/2/315/ABA0000C1145-947633.pdf
I hope that someone can help me.


texts: What is the use of the fourth leg, the one with igbt in series with the diode, in the infineon power module?

texts: The circuit shown below is the schematic of infineon PIM module. I am specifically interested in FP15R12W1T4. From the schematic I could understand all elements other than the 4th leg which has an igbt in series with a diode. I am new to this field. I assume, that leg and terminals are provided to feedback the present voltage level under a specified switching frequency.


texts:
Here is a component OTA provided by LTSpice which has inverting non inverting common and output node. I am in process of modelling this OTA behavior form LTSpice to PSpice.
I reffered this link for the description Descriptions of OTA parameters

G=6u Iout=20u Ref=-1m Rout=1Meg Vhigh=0 Vlow=-3

Can anyone share idea to test cases in LTSpice for those parameters.
How to validate those each above parameter that are affecting the output?


texts: Current source with grounded Load and floating power supply

texts:
The following circuit represents a basic op-amp current source and can be found  in the "Art of electronics 3rd edition" in page 228.

\$ I_{load} \$ is easy to calculate in this situation.

The problem with this circuit is that the load is floating (neither side is grounded).

This problem is fixed  by connecting the load to GND and with a floating power supply as showed in the following circuit.

I can't understand how \$ I_{load}\$ is calculated here.

I know that any node in the circuit can be used a reference node (ground node) which, i think, implies that the potential of the rest of the nodes are calculated in function of the new ground node.

When i try to analyse the circuit something goes terrible wrong.
By the expression of \$I_{load}\$ (present in the last figure)

\$ V_{in}= (V_+R_1)/(R_1+R_2)\$

But looking at the circuit
\$V_{in}=v_+=v_-= V_{GND} \$

Shouldn't \$V_{GND}\$ be seen as 0V to the other nodes?

What i am missing?

Thanks


texts: Need help with identifying the function of 3 wires in camera flash circuit

texts:
I have this camera flash circuit from a Ricoh AF-70. I’m trying to identify what function the 1,2 &4 wires does in this circuit?
The blue wire is definitely to trigger the high voltage to fire the flash. The other red and black wires the positive and negative of the batteries. Unfortunately because the circuit is so tightly packed I can’t see the label of the transistors.


texts: Query regarding RF trace width maintenance in a PCB Layout

texts:
I have a query reg. RF PCB design

This image is the "output end of a power amplifier(PA)", which gives 1.5-j1.7Ohm impedance at output pads(12th & 10th) of the PA. And then it is being matched to 50 Ohm single ended impedance using matching circuitry.

From the following link I have understood that "we no need to worry about controlled impedance when trace length is less than 1.6 cm in my RF PCB design."
                  Should we maintain the same impedance for the traces carrying RF signal line?

Note: we have replaced strip-lines in the schematic with inductors.

Questions:
1. Do I need to worry about impedance matching in this design since there is already matching circuitry for achieving 50 Ohm at the end?

Is it OK if I start drawing the trace of 50 Ohm impedance from the output pads of the PA though at that points the actual impedance is 1.5-j1.7 Ohms?
From where to where I have to consider as total trace length whether from output pads(12th & 10th) of the power amplifier to open end(RF OUT - the end point where the antenna is connected) or length of each Trace segment between the pad to pad(or component to component)?


texts:
I'm using ACS712 hall effect current sensor to detect presence of current in the power line of a remote device. I don't need exact current value but rather just want to know if it's above certain threshold (0.2A in my case). 50Hz 0.2A AC current will result in 50Hz 37mV AC voltage signal with +2.5V offset. I'm planning to feed rectified and smoothed output to a comparator so it can trigger microcontroller when it's above threshold.
I've tried to copy schematic from the datasheet of the IC but it doesn't seem to do what I want in the simulator. No matter what I do with voltage source, output at the capaciter upper leg seems to stay at 2.5V. What am I doing wrong here?

Allright, I've played with schematic a little bit and looks much more promising now!
It still gives my only 10mV of detection margin at the threshold but it's better than nothing!


texts: Conventional way to manage and use the libraries in Altium

texts:
I guess I have been always doing it wrong way because I don't have to use Altium so often. Whenever I start a project I create a schematic library (*.schlib) and a PCB library (*pcblib). And then I copy the symbols and footprints from other projects if available, download the libraries from manufacturers and add those libraries to project, and if not available make my own symbols and footprints.

I don't know what is the best way to manage libraries, but what I would like to have is a central location where I keep all the symbols, footprints and models. And whenever I am working in a new project, I would just copy/import them to my project and create components from the symbols and footprints as required. Same symbols can be used for different footprints and same footprint can be used for different symbols. I don't want to import whole library of amplifiers that I downloaded, just to use one amplifier. I just went through some techdocs from Altium, and there are many ways to manage libraries: database library, database link, vault based, integrated libraries, component libraries... After reading few of them, I am still confused what would be the right way.

What would be the appropriate way to manage and use the libraries in Altium for me?


texts:
I'm making a PCB for a personal project using the STM32F205. In my plan, the STM32 only provides USB and SWD interface with the PC. I know that with the help of USB DFU, I can download my program to the system memory through USB.

My concern is whether the initial bootloader of the STM32 chip contains the DFU? I mean the bootloader in the STM32 chip I bought from the ST company. Because if not, I think there is no method to download the DFU bootloader into my board and I have to add another interface, like UART or SPI, to my design which is only used to download the DFU bootloader.


texts: Why there is transistor on LM317 ADJ pin?

texts:
I would like to understand the meaning / function of the transistor on LM317 ADJ pin on the following circuit.

Image source


texts: How do filament LED bulbs work, looking very similar to incandescent bulbs?

texts:
Filament LED bulbs use very narrow strips containing the LED,
which look similar to filaments of an old incandescent bulb:

They look like a normal bulb with large "old-style" coal filaments, and are of about the same size and shape as the common standart E27 socket bulb.

There are two basic variants of these bulbs:

One "plain" as described, looking impressively similar to a classic bulb
The other has a white coating on the glass, about 15mm wide next to the metal socket.

How are these filaments build?
I could imagine the it's "pretty normal" LEDs, but lots of them,
directly bonded to something? (There are references to COB)

How does the heat management work?
Ii have seen speculations about filling the bulb with either helium
or "some patented organic gas" -
could that be enough for cooling?

How does the driver - which seems to be very small - work?

In the variant with white coating - hiding some components, I assume - is already not that much space, and in the plain variant, there seems to be almost no space for something nontrivial.

Below you see some bulbs of the white coating variant, switched on:

(Images with the permission of this supplier at Alibaba)

Note how the LED filament bulbs are not so much similar to the tungsten filament bulbs recently being phased out - they are more resembling the long outdated carbon filament bulbs:

bd® Antike Edison 220V-240V 40W Retro Vintage Industry Style Deko Glühbirne (kl)


texts:
I have the following config values for 18F452 on my code;

#pragma config  FOSC=HS
#pragma config  PWRT = OFF
#pragma config  BOR = OFF
#pragma config  BORV = 3
#pragma config  WDT = OFF
#pragma config  WDTPS = 128
#pragma config  CCP2MX = OFF
#pragma config  STVREN = OFF
#pragma config  LVP = OFF
#pragma config  DEBUG = OFF

Now, I want to switch to the 18F4550, but my code is executed too fast compared to the 18f452. I have the same hardware setup (basically I replace the PICs on breadboard).
And my config values for 18F4550 is;

#pragma config PLLDIV   = 5         // 20Mhz external oscillator
#pragma config CPUDIV   = OSC1_PLL2
#pragma config USBDIV   = 2         // Clock source from 96MHz PLL/2
#pragma config FOSC     = HSPLL_HS
#pragma config IESO     = OFF
#pragma config PWRT     = OFF
#pragma config BOR      = OFF
#pragma config BORV     = 3
#pragma config VREGEN   = ON
#pragma config WDT      = OFF
#pragma config WDTPS    = 128
#pragma config MCLRE    = ON
#pragma config LPT1OSC  = OFF
#pragma config PBADEN   = OFF
#pragma config CCP2MX   = ON
#pragma config STVREN   = ON
#pragma config LVP      = OFF
#pragma config ICPRT    = OFF
#pragma config XINST    = OFF
#pragma config CP0      = OFF
#pragma config CP1      = OFF
#pragma config CP2      = OFF
#pragma config CP3      = OFF
#pragma config CPB      = OFF
#pragma config CPD      = OFF
#pragma config WRT0     = OFF
#pragma config WRT1     = OFF
#pragma config WRT2     = OFF
#pragma config WRT3     = OFF
#pragma config WRTB     = OFF
#pragma config WRTC     = OFF
#pragma config WRTD     = OFF
#pragma config EBTR0    = OFF
#pragma config EBTR1    = OFF
#pragma config EBTR2    = OFF
#pragma config EBTR3    = OFF
#pragma config EBTRB    = OFF

To be honest, one might think this is a good thing because of the increased speed. But I've implemented a software UART and the required delays for my baud rate is based on clock cycles. This speed increase messed up my whole serial communication. Any ideas to synchronize two scenarios ?
Thanks in advance,


texts: Altium error: Net contains multiple output sheet entries

texts:
I'm having a hard time with this problem and cannot figure out how to deal with it. As shown in the figure below, ADC[0..2] is going out from A2 and A3 and in to A1:

In details:

ADC 0 is the output of A2
ADC 1 and ADC 2 are the outputs of A3

All three pins are inputs in A1, this connection seems to be logical, but Altium didn't like it!!

So the question is: How can I get multiple output sheet entries without Errors ?


texts: IR circuits: increasing sensitivity of simple analog receiver IR LED

texts:
I have the following circuit using a TSOP1738 and a simple IR receiver LED (analog):

It's basically:

a TSOP1738 put to my 5V uC pin, its OUT being read directly by the yellow channel of my oscilloscope
an analog IR receiver LED in series with a 3kOhm resistor put to the 3V3 uC pin (shorter leg) which is also being read directly by the blue channel of my oscilloscope

I'm using a 38kHz IR remote and doing some experimenting with this setup.

1) If I'm simply pointing the remote directly above the analog IR LED and keep changing height, both the TSOP and analog IR LED respond: TSOP is digital and thus outputs 0V/5V while with the IR LED I can nicely see how it's analog response increases as I get closer to it, here's a pic of what the oscilloscope shows me:

2) If instead I'm either not pointing directly to the IR analog LED or pointing from a height >~1m the IR analog LED does not respond at all or its response is very very insignificant, while the TSOP1738 responds very well even if I point towards the ceiling from 4m away:

My questions:

1) What makes TSOP1738 so different from the analog IR receiver LED regarding sensitivity?

2) How can I increase the sensitivity of the IR analog LED?

3) Can I somehow make TSOP1738 give me analog output?

Notes:

I'm not sure about the exact specifications of the components as I've bought them a while ago (I'm not even sure that's a TSOP1738 but it probably is)
I'm a beginner in electronics, really just understanding mostly only the basics for now (but I'm good with programming in general, including uCs) :)


texts: Confused as to how implement ALU using structured VHDL

texts:
I am new to VHDL, working on assignment for my Computer architecture class:

implement 32 bit ALU using VHDL, that performs only certain operations: and, shift left, shift right, complementing one of the input, rest of operations will do simple addition. Trick is, code needs to be structured, since instructor provided bitshifter and adder.

I have googled for examples, but all of them use straightforward code(such as result <= a + b). What would be a good way to implement ALU using above requirements ???
Thanks !


texts: Are connectors and pin outs standardised by the MIPI alliance? [Also can anyone name this connector]

texts:
Does the MIPI alliance standardise or are there at least any conventions for connectors and pin outs between devices that use there protocol specifications?

The device I am interested in (Microsoft Kinect One ToF ASIC) reportedly uses MIPI D-PHY configured as 2 x 4-lanes for communication via the connector in the lower left of the board imaged below.

Additionally can anybody name the type of connector used in the image (ignore the green square overlay in the image)?


texts: IR control with Darlington Transistor ULN2003A

texts:
I need a simple circuit to control a IR device. I'm quite a newbie with electronics so I would like to know if this circuit is correct because seems is not working.

These are the datasheets of IR LEDs and ULN2003A:

IR led
ULN2003A

Thanks for your help!

FIXED: wrong LED direction and number of leds, resistor now to 8ohms.

This way I power leds with ~110ma.
Thx for your help!


texts: Upgrading my ebike battery to give more speed and longer range

texts:
I am in the early stages of trying to understand how to do this, so if you're kind enough to reply, please answer in simple terms if that's at all possible.

I want to add cells to my electric bike battery pack to increase the speed and the range. The speed is less important than the range - but a bit more would be nice. I've opened the case and found 5 banks of 8 x 18650 li-ion cells in there. I know that each bank is connected in series, with the cells in each bank connected in parallel. The bike is a Freego Hawk 36v. I have enough slots for another 20 cells (ie 2.5 banks). Would anyone know what is the best way to configure them to get much more range, and a bit of extra speed if possible. The existing cells are Samsung ICR 18650 26H li-ion, 2600mA, 3.65v.


texts: How to test a stepper motor without a microcontroller?

texts:
I'm very new to microcontrollers and stepper motors.

I have an idea to make a CNC based pen, so I got a stepper motor with ULN2003 stepper motor driver, but I have to learn more before using it.

To rotate it I need to make a small microcontroller program but I want to test it without microcontroller.

This is my stepper motor with driver:

So I can supply power to +and - terminal, but I have no idea how to use the 4 pins named 1n1,1n2,1n3,1n4. But I think it's possible to rotate it may be very small angle without a microcontroller. Can  you help me to test it?

Do I need to supply a voltage to n1 and n2 or something like that ?


texts:
I'm working on a project which requires the control of a motor via a +/-10v control signal (which will be fed into an amplifier).

In theory any motor can be used, although it should be attached to a high resolution encoder (1024+ PPR).

A setpoint (theoretical position) is calculated 1000/sec, and the result used within a PID loop. The result is then outputted to an 8-bit DAC. To allow motion in both directions, values under 127 cause a negative signal, and values above 129 cause a positive signal. As such, the resolution is reduced to 127 steps.

Does this seem sufficient to achieve smooth motion, or should I choose a DAC with more resolution?


texts: I2C EEPROM bit-banging: Writes fine, but only if first bit is not set

texts:
I am currently working on an I2C EEPROM project using bit-banging to drive the SDA and SCL lines.

My read function works fine but whenever I write any byte with a leading "1", I always read FF back; even if the byte has been programmed with something else before. Leading "0" is perfect. It is not my read routine; as I can see on the scope it returns FF.

I am looking for suggestions on why this might be. Is there any obvious I could miss which could cause the problem? [I cannot post the code - company confidential... :(]

Every waveform I look at meets the spec exactly. I am decoupling the EEPROM. My pull ups are 2.2k so within spec. I'm clocking at about 500 Hz in this prototype. The chip is sending ACKs to each of my bytes so it recognises them. But it just doesn't work...

I am using a Microchip 24LC256.

Simplified writing algorithm for one byte:

wait
SDA low
SCL low
wait
for each bit
    if bit is set:   SDA high
    if bit is unset: SDA low
    wait
    SCL high
    wait
    wait
    SCL low
    wait
wait
SDA high
SCL high
wait
wait
check ACK status
SDA low
SCL low
wait
return ACK status

Simplified reading algorithm for one byte:

wait
SCL low
SDA high
for each bit (8 bits)
    SCL high
    wait
    wait
    SCL low
    wait
    check and store received bit
    wait
do a NACK or ACK depending on if it is the last byte


texts: Why are my reed relays releasing 10x faster than spec?

texts:
I have Magnecraft W171DIP-25 reed relays (datasheet). They are DPST relays with a built-in coil suppressor (according to datasheet). Their listed response time is 1 ms, and, following the logic of this question (Do reed relays have shorter opening than closing time?), I would expect the release time to be at least 1 ms.

I measured the release time with an oscilloscope: 0.1ms.

I'm not complaining, but why is this? I did it in two distinct (identical) setups: same result.

I don't have a 5V supply available on the board, so I just ran them off of a 8V supply and stuck a 100 Ohm resistor in from of the relay (the coil resistance is 200 ohm like on the Mouser site, NOT 500 ohm as in the datasheet). I used a NPN transistor to switch the relay.


texts: 4-layer video experimenter's board layout, critique sought

texts:
This is a layout for an ADV7184 video DAC, connected to an ADV7341 video encoder. The intention is to allow a microcontroller such as an Arduino or STM32 to generate text and graphics over the video image, by means of the ADV7184's support for SCART RGB overlay. I also hope to use the support for teletext and VBI as a channel for sending digital data to receivers. I have tried to replicate the layout of the ADV7184 evaluation board as much as possible, while removing the FPGA and unnecessary connectors.

I would really appreciate it if some of the experts here would critique my board layout and point out if I'm making any obvious mistakes. My priorities are first to reduce/mitigate crosstalk and second to reduce EMI.

The stack-up is as follows: signal (top) - GND - Power - signal. I have put a copper pour on the top layer.

In particular I would like guidance on the following (related) questions:

Will my use of a copper polygon around the 27MHz LLC (line locked clock) on the bottom layer be effective in preventing coupling with other traces and power/gnd?
Would it be advantageous to put GND "fingers" between the video output traces?
Similarly, would it be advantageous to put fingers separating the LLC from other traces?
Will a copper pour on the top layer as I have done be advantageous or not?
Are there any issues/possible improvements to decoupling?
Any other issues/suggestions?

Below are schematics:

Thanks!


texts:
i have learned that usage of complements simplifies the subtraction operation and is used for logical manipulation....

But , I really don't seem to get it?? how does it simplifies our calculation ?? and why do we even have to find the 9's and 10's complement for decimal number??

I have searched it , but every where it just says its used to simplify stuff and then give the method of finding them respectively....i do understand the steps ....but don't know where and when to use them??

i asked my teacher about it , and she just said its because the computer stores stuff with  regards to 2's complements for any subtraction...but it still didn't clarify my doubt ...i mean why does it has to do that??

someone please clarify it for me..


texts:
I have a DSC-1555 Alarm system that I am trying to wire up to an Arduino-Mega the problem I've run into is that the DSC uses 12v TTL to the Console and the Arduino uses 5v TTL.

I was just guessing to use some resistors but I want to double check before trying.


texts: How can I convert multiple Karnaugh maps into a logic gate circuit?

texts:
I'm designing a 8421 BCD to 84-2-1 BCD converter circuit. The truth table is:

Decimal | ABCD | WXYZ
   0    | 0000 | 0000
   1    | 0001 | 0111
   2    | 0010 | 0100
        .      .
        .      .
        .      .
   9    | 1001 | 1111

Everything after decimal 9 is a don't care. I started by creating Karnaugh maps for each W, X, Y, Z. From the Karnaugh maps, I found the following equations:

W = (A)(~B)(~C) + (~A)(B)(C+D)
X = (~A)(~C)(~D) + (~A)(~B) + (~B)(D)
Y = (~C)(D)([~A]+[~B]) + (~A)(C)(~D)
Z = (D)([~A]+[~B][~C])

Where multiplication means AND, addition means OR, and ~ means NOT. I'm unsure of how draw a circuit with the appropriate logic gates from here. Do I create a circuit for each letter and then AND all of the outputs together? Do I combine all of the expressions (as in W+X+Y+Z or WXYZ) and simplify the expressions from there, then create a circuit using the new simplified expression? I'm not really interested in what this particular circuit will actually look like, I'm trying to find tackle the more general concept of moving from truth tables to circuit schematics.


texts: What happens to the Real and Reactive power when I increase the excitation current in a 3-Phase Synchronous Generator?

texts: Basically my doubt is, for the same load, why does the Real power remain constant when I increase the excitation current?


texts: How to find common emitter current gain (beta) from graph

texts: I am trying to find the common emitter current gain of a bjt transistor I made on ltspice, and I need to use the below graph to find it, but Im not sure how to interpret the graph to find it. Should I find the rms current of Ic and Ib and then just use that in the equation, Beta = Ic/Ib ?


texts: What is the output voltage and PIV of the half-wave rectifier?

texts:
I was analyzing the following circuit, applied sinusoidal voltage at the secondary is 20 Vrms (DVM measurement). My intention is to calculate the output voltage (Vo) measurement when using the DVM and PIV?

EDIT

(i) Output voltage

Following is my calculation.
At diode conducting condition –

(ii) PIV

PIV is the peak of the sinusoidal voltage signal when the diode is not conducting.

PIV = 0.5 * VRMS * 1.414
    = 10 * 1.414
    = 14.14 V

Could you please verify the results.?


texts: Degenerate circuit concept and its theoretical and practical implications

texts:
I came across with the term "degenerate circuit" when I was studying solving linear differential equations with Laplace transform. I have learned that a system is called degenerate when the determinant of coefficient matrix (characteristic polynomial) is zero.

I've searched a lot to try to understand the concept of "degenerate circuit" but I could not fully understand it. Some fragments of what I have searched:

Network Theory and Filter Design (Vasudev K. Aatre)

Electric Circuits And Networks (For Gtu) (Kumar K. S. Suresh)

Linear Circuit Transfer Functions: An Introduction to Fast Analytical Techniques (Christophe P. Basso)

My questions are:

What is the definition of "degenerate circuit"? (I think Basso's book 1st fragment answered it, but I didn't understand)
What are the theoretical implications of a circuit being degenerate, in terms of stability?
In "real life", what does it mean to be degenerate? A degenerate circuit, if built, would not work?


texts: Can two lights be switched between without an "ON-ON" switch?

texts:
The schematic above shows our problem. We need to be able to turn on light A when a switch connected to light A is closed and then turn on light B when the switch is open.

There are a few constraints:

the lights must have a common ground
they must have a common power source
the switch can either connect A to the battery or be open. It cannot connect to B in it's open state
no additional switches can be added, we want to be able to control it with just the single switch (they can be added if they don't have to be actuated by the user, we just basically want one user input)
only "traditional" sorts of electronic components can be used such as wires, diodes, resistors, capacitors etc.

The blue area just signifies that it can be filled with whatever wiring is necessary to achieve this.

Is this setup possible to achieve?

This question has the practical application of being used as wiring for a go kart brake system. I've been trying for a while to look on the internet for answers but I don't think there's much hope.


texts: Single Board Computer (SBC) suggestion for interfacing with DMA

texts:
I am taking over a project where a Spartan 6 FPGA provides the interface between an ADC and a DDR2 memory chip. The FPGA takes 16-bit data out of the ADC and stores it into the RAM at a rate of 28MHz.

I have the option of making the DDR2 controller multi-ported so that a processor can access the DDR2 memory and begin analyzing it. Ideally I would like to find a COTS single board computer ( SBC ) for under $150 that has Direct Memory Access ( DMA ) available for an off board connection to the memory. The SBC would eventually run some type of Linux distribution so it would have to be more powerful than a standard micro controller.

This is kind of stepping out on a limb for me, since I have previously developed using PIC's or Xilinx Microblaze where I designed the entire board. I'd like to move up to running Ubuntu on an established board, which is why I took this project on.

Just hoping I can get some suggestions and let me know if there are any details I am not clear on or if I should be posting in a different forum. Thanks!


texts:
The following circuit is taken from The Art of Electronics book.

Assuming the base-emitter voltage drop of 0.6V for both the transistors, the C1 charges to approximately 4.4V (left-to-right) when the input is low. When the input goes high, the collector of T1 as well as the left plate of the capacitor are pulled to .6V, resulting in right plate going to about -4.4V for a brief period. How can I calculate the pulse width at the output?

I guess the formula to find out the pulse width is

$$ v_c(t) = V_s + \left[ v_c(t_0) - V_s \right] e^{-\dfrac{t-t_0}{RC}}, \quad t\ge t_0. $$ where $$ RC = R3C1 = 100us. $$

EDIT: Waveforms added


texts: How to calculate resistors for transistor driver circuit

texts:
This is related to https://arduino.stackexchange.com/a/36761/13642, I want to find the values for the two resistors so that the led will get 100mA.

Vcc will be 5V and I have either 2N2222 or 2N3904 transistors. Let's say I use the 2N3904.

They mention the equation: hFE(VCC-VBE)/RB. (Is the full equation hFE(VCC-VBE)/RB = ICC?)

I tried to plug in the values: Vcc = 5, Hfe = 30 (from the sheet), VBE = 40*10^-3R since the arduino's pwm output is 40mA and from ohm's law, ICC = 100mA (the desired current for the led).

so we get: 30*(5-40*10^-3R)/R = 100*10^-3 => R = 3.3/(100*10^-3/30 + 80*10^-3) = 39.6.

This is not even close to 1000 like in the answer, so I'm doing something wrong here.

So how are you supposed to find the B line resistor value? Also, how do you find the C line resistor value?

This is the led I will use btw: https://www.vishay.com/docs/81009/tsal6100.pdf

"Arduino" is Arduino UNO for now (Wemos D1 mini later).

I don't think it's a duplicate since my circuit is a little different and what I ask for is different. I also have no idea what is that on their C line...


texts: Advantages of splitting a single NMOS transistor into two

texts:
Can anybody explain to me why in the schematic attached below that using two transistors is better than using only one transistor that is larger (longer)?

I see that these two transistors are the equivalent of one with length = L30+L31, so but why can't we use one transistor that is longer? I think that using two gives you bigger input resistance, but is this the only advantage?


texts: Triggering a camera flash with a microcontroller

texts:
I took apart a "one-way-camera" for the flash part and found a circuit very similar to the image. For a project I need to trigger the flash with a microcontroller (attiny25/45/85v, low voltage version, operates with 1.8-5v). To do that I simply need to bridge the charge switch on turn on and then trigger the flash by replacing the trigger mechanical switch with something else. I am considering several options for this and am hoping on input on what would be the easiest and cheapest option, as I need to produce many of these circuits.

What makes this tricky is that the flash uses more than 1000 volts to trigger and most transistors are not build for that kind of application. Relays have worked fine but especially low coil voltage ones are hard to get/expensive and im wondering if there is a good alternative.

Thank you for your input in advance.

PS: The whole circuit should ideally run on 2 AA batteries (=3v)


texts:
The one on the left seems to work neatly. But the right ones' motor goes way slower.
Though, I did find the right one on the internet (and internet is always true).

My thoughts:

The amount of power presented on the 'input' of a NPN-transistor scales the output accordingly. (And the NPN's have to share the power of Vin)
The buttons are floating when not pressed?
PNP-transistors turn on when their 'input' is low.

My Questions:

Is the first one somehow still 'faulty' in some way?
Should I only use MOSFET's instead of NPN-Transistors? Or why not?
Are my thoughts correct?

I'm not very experienced with analog circuitry... I'm way better off with digital stuff, but I want to know/learn how to make, in example, a motor controller.
This is where I got the second circuit from: https://www.youtube.com/watch?v=CRPNqpKc9yk


texts:
I have a set of battery powered candle lamps on a dining table, in a display cage.

I converted the candles to run through a DC transfers and battery eliminator (due to the amount of AAA batteries we were getting through - rechargeables only seemed to last a couple of days)

Unfortunately the cats play with the cable and keep dragging the lamp off now.

So I had a thought of transferring the power wirelessly through the table to the base of the candle stand and so on from there.

Is it possible to shift about 200mA through a 1" table and make a wireless power transfer coupler?

Thanks.


texts:
I was watching the following Razavi video

https://youtu.be/icrn9cYIPUA?list=PLiDoPUX9nLkIw9EnIv_3K19wlcyJ6msYd&t=1564

At 26:04, he says that no current flows through the resistance Rd as voltage across it is zero. But what's to say that current flows the the NMOS cascode on the left? Voltage across that is also zero?

Here's another example of the same thing except with a PMOS load,
https://youtu.be/icrn9cYIPUA?list=PLiDoPUX9nLkIw9EnIv_3K19wlcyJ6msYd&t=2276
At minute 38:45. He did the exact same thing and he said no current flows through the PMOS part becasue voltage across it is zero but isn't that also the case with the NMOS part in that circuit?


texts: TNY264 - hisses when isn't load significantly

texts:
Recently I designed a power supply based on TNY264 datasheet schematic and tested it.

It works perfectly but at small loads the TNY generates a loud hissing sound.

Only after load of about 100-120mA does the hiss fall to an acceptable level.

At first I thought it is the transformer generating the "hiss". But it is in fact dedicated for this model.

If someone has more experience than me, please tell me what can I change to need a smaller load works correctly without hissing.

Thanks for every help.


texts: It is possible to exist more than 1 color code for same resistance. Can i use all of these color-codes?

texts:
It is possible to exist more than 1 color code for same resistance-value. I doubt, is there any convention about use only one of them (while manufacture) .

Example : Say an 1 ohm resistor could be expressed as Black-Brown-Black (01*10^0) simply, but when i buy  1 ohm resistors, i always found Brown-Black-Golden (10*10 ^(-1)) being sold.

Example of more than one possible codes for same resistor

Now, i want to know, are the all possible codes correct? or there are some conventions about it?


texts: Does the frequency of a crystal influence its height?

texts:
Here is a picture of two crystals:

Does the difference of frequency explain why the 6 MHz crystal on the right has a lower profile than the 5 MHz one ?


texts: I am having a problem with Pierce oscillator designed to work with my SMART Card reader. I am using 3.58MHz oscillator, 74HCU04 gate IC for the NOT gate, and both 22pF capacitor and 1Mohm resistor. I was unable to get any clock pulse.


texts: Calculating the efficiency of an audio amplifier

texts:
I'm looking at the PAM8406 Class-D/Class-AB amplifier and I'm not seeing the efficiency for a 2Ω load in Class-AB mode. The use case for the amplifier is driving mid-range/mid-bass speakers for use with a telephony system (essentially, no music will be output from the amp, and it will only be on for short a duration of time).

From what I've read, Class-D amplifiers are better suited to drive sub-woofers and other bass intensive applications, where as Class-AB is less efficient but more suitable for general audio applications.

How can I calculate the efficiency of this amplifier?
Is there a more suitable alternative to this amplifier for my use case? I need at least 2W into a 2-Ω load.


texts: Why do I get 'Unmatched Nets' in Altium and how do I remove them?

texts:
I'm trying to import a Schematic to PCB in Altium and I get this message that there are unmatched nets cropping up:

The PCB is empty, I've searched in the Schematic for them but I can't find them. Do I match them or is there a way to delete them? I don't understand why they're in the first place....


texts: Demonstrating back EMF on an inductor in LTSpice

texts:
I'm trying to demonstrate back EMF on an inductor in LTSPice with this model:

https://dl.dropboxusercontent.com/u/16979265/Draft2.asc

I'm expecting the voltage on the inductor to have a negative spike on the falling edge but it doesn't happen. What am I doing wrong here?:


texts: How to connect a crystal oscillator to generate Square wave

texts:
I've a 1 MHZ crystal oscillator.

I want to generate a Square wave of 1 MHZ using the crystal oscillator.

How to connect it and what are the needed components?


texts: Measuring Power from Altera Dev. Kit (CycloneIII)

texts:
The Altera CycloneIII starter kit that I have provides a jumper (J6) that is connected to VCCINT of the CycloneIII FPGA core for what seems to be the purpose of measuring the core's power consumption.

Here is the reference page for the kit: http://www.altera.com/products/devkits/altera/kit-cyc3-starter.html

What I had intended to do was to take measurements from this jumper with a scope (voltage across the jumper should be proportional to power) - but I'm afraid that the readings from this jumper may not be as straight-forward as I had originally anticipated.

More specifically - after looking at the pin-out for the CycloneIII FPGA, each "bank" in the FPGA has its own VCCINT. I'm curious as to how these relate to the VCCINT that is said to be tied to J6.

How representative will this reading be?

Any insights?


texts:
I have been running various different ZVS based flybacks for all kinds of uses (jacobs ladders, SSTCs, etc.), however, for some reason, I am now getting mosfet heating, which was never apparent before – so I am unsure as to why no matter what I do, I have this issue now.

With a simple induction coil as load, I used to be able to run indefinitely with 300W, and with watercooling (as opposed to a small heatsink and fan) up to around 900W comfortably.

Now, it seems, I struggle to manage the MOSFET heating at anything over 100W sustained, which results in mosfets that were previously cool to the touch, sitting at 65C even at 100W (6A average load).

I have changed FETS, caps, coils, made new PCBs and played with designs, but I seem limited. I have years of experience with these kinds of circuits but now I am stumped. The waveform presents a perfect sine from the two sides, but probing each side shows strange oscillations that I assume to be switching artifacts.

View a diagram / schematic of the type of circuit here:
https://cdn.instructables.com/F7Y/CH9S/G9NH8XOF/F7YCH9SG9NH8XOF.MEDIUM.jpg

And a video of the waveform here as I change V and I (which upsets my power supply occasionally):
https://youtu.be/vacUYmgCReA

The DC supply is a 900w 30V/30A switching bench supply, so should be up to the job.

I believe the spurious oscillations are due to switching problems. All my components are new and I still get the issue, I only built this to test what was going on and it still happens :-/

Any advice would be most welcome... I simply can't see how or why it's heating up and killing fets, and I am pulling my hair out after building several of these with new components after having built a few dozen years back without any issues.


texts: LDO Voltage Regulator - What happens inside dropout range?

texts:
I’m using this 3.3V LDO (https://www.sparkfun.com/products/526) to power a device which normally takes 2 AAs (3V), using a 3.7V LiPo battery. The device won’t power on without the regulator (it can withstand variance in AA voltages but only until about 3.7V total).

I realized that the regulator I’m using has a 1V dropout voltage, yet the device powers on and works just fine until the battery drains. My question is this: why does it power on when 3.7V is well within the 1V dropout range? It is supposedly not regulated at this point, correct? Is there something else going on that happens to drop the voltage just enough that the device allows itself to power on? (For reference, it’s a Gameboy Advance, and it protects itself from powering on outside its expected range).


texts: In noise voltage equivalent circuit, why are the source and load resistances equal?

texts: Yes I am aware of the maximum power transfer theorem. I don't get though what the lesson meant, especially by worst condition.


texts: How do I heat a wire around a pot to heat up the soil within

texts:
Basically, I'm trying to replicate the effects of a heat mat for soil but I want it to be variable. I'm trying to heat up the soil inside of a pot. The setup I'm imagining is some form of wire (thinking copper) coiled around a clay pot. The temperature for the soil I want is around 25 C. Ambient temperature is 19 C.  I imagined a regular battery attached to the wire with a resistor. Is there a reason why this wouldn't work? If not, how would I go about doing this?
I am very new to electrical circuits and wires, so I apologize if I sound idiotic. Also, if this is the wrong place to ask, please let me know where I could find the answer.
I would love to figure this out myself as well, so if there are any resources that would be helpful, I would love to learn.


texts: UART on my atmega328. Dataregister on the USART (UCSR0A) status never set on

texts:
I'm experiencing a little troubleshooting trying to send and receiving data into the UART of my atmega. I don't know if it's because the clock cycle is misconfigured or if I made wrong assumption of what the code should be, but I took it from an example book.

I'm expecting to write data into the usart then simply read it back.
I 'm just trying to output a LED for the moment, but it never glows, so that i'm assuming my code never goes out of usartReadChar().

I'm working with an atmega328p and the pin / register macro are from iom328p. The clock speed is configured at 1Mh.

The only difference from the book is that he uses an atmega168.

What I don't understand is that I'm not blocked for sending data to the usart (the Usart Data Register Empty (UDRE0) is actually always empty). But
the receive complete bit (RCX0) into the statut register (UCSR0A) is never set either.
As if the status bit are never working at all.

I have tried to change the CPU clock speed without any luck.
By the way i'm not sure how to compute the baudRate of my usart and I'm not sure if it has really an impact on my code, since I'm only sending data from the AVR locally. So does I need to synchronize it with my CPU?

I tried lot of variant of usartInit() setup, but they never work.

here is my code:

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

  void initUSART(void) {

  UBRR0H = UBRRH_VALUE;                        /* defined in setbaud.h */
  UBRR0L = UBRRL_VALUE;
#if USE_2X
  UCSR0A |= (1 << U2X0);
#else
  UCSR0A &= ~(1 << U2X0);
#endif
                                  /* Enable USART transmitter/receiver */
  UCSR0B = (1 << TXEN0) | (1 << RXEN0);
  UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);   /* 8 data bits, 1 stop bit */
}

char usartReadChar(){
    while(! (UCSR0A & (1 << RXC0))){}

    return UDR0;
}

void usartWriteChar(char data){
    while(! (UCSR0A & (1 << UDRE0))){}

    UDR0 = data;
}

int main(){
    DDRB   = 0xff;

    char data;
    initUSART();
    usartWriteChar('a');

    while(1){
      data = usartReadChar();
// actually, never reach

      PORTB  = (1 << 0);
    }

    return 0;
}

When I compile it with a Baud rate of 9600, I don't get any warning error about baud rate.
But if I choose wrong Baud, of course I've got this kind of warning.

  /avr/include/util/setbaud.h:227:4: warning: #warning "Baud rate
  achieved is lower than allowed" [-Wcpp]  #  warning "Baud rate
  achieved is lower than allowed"

So i'm assuming my baud rate is correct. What could be wrong then?
Your help will be greatly appreciated. Thanks.

* edit *

I gave up trying to output something localy into my avr. So in order to debug i have connected my FT232R chip to the rx and tx pin of my atmega, to see if something could output from the UCSR0A status register, and it worked.

What is strange is that actually the debug function to send data into the transmiter register was not working at all, even if the UCSR0A say it is busy to transmit data.

According to the book, the data sended from the arduino program must work, but it was totally not working with me. But from my FT232 the program is nicely working, as if the USART was not actually initialized when i called the instruction to send data to the us art. But since it is all synchrone I know this is not that.

I found lot of topics about configuring USART on avr, but no one tells to test a debug program like in my book. So i'm wondering if it is actually an atmega168 specific feature. Actually i don't understand why this is not woking like the book tells.


texts: Controlling Analog RC Car Remote with Arduino

texts:
I want to take my RC car remote, which uses a potentiometer to control throttle, and connect it to an arduino in order to control the cars speed. The ardunio fits perfectly in the base of the remote.

I want to retain original functionality, however, this can be changed.

I am fairly new to electrical engineering and arduino in general.

TLDR: What would be the best way to "emulate" a potentiometer signal using an arduino that would then get sent into into the part of the remote that transmits signals?

EDIT: This is for a project on self driving vehicles. I will have a desktop PC with Java software that is grabbing images from a camera mounted on the actual car and telling the car how to react. The arduino in the base of the remote will be connected via a USB port. The android / Java part of the software is complete and I just need to get the arduino code working to tell the car "Move Left this much" and "Go forward for x seconds". This is all figured out except for that analog control.


texts:
I volunteer at a club to teach Arduino programming to teens. As part of that, of course, I talk about voltage, current and what not to do. My prime example is taking an LED, putting it directly across the power, and grinning as they jump at the satisfying POP! I then quip that it's no longer "a Light Emitting Diode - LED - but a Dark Emitting Diode - DED." (OK, OK, I need new material...)

I just got a new batch of 100 LEDs for $2 - and these refuse to die, let alone pop! They glow brightly with 9V directly across them; I measured 120 mA! They heat up incredibly such that I can't hold them bare-handed (I wear gloves), and then slowly dim down until they finally turn off. I take them off the power, let them cool down, and then they work again!

Have I just hit the jackpot with this batch? Or are LEDs being built much more ruggedly than before? I know that some have resistors built into them, but I'm pretty sure these aren't those.