texts:
it,s me... Again. I tried almost everything but i can't make it work properly. This is my code:

library ieee;
-- Import all the declarations in a package
use ieee.std_logic_1164.all;
entity Octal is
port
(
--Puertos de entrada
    B8  : in  integer range 0 to 17;

-- Puertos de Salida
    Binario : out std_logic_vector(3 downto 0)
);
end Octal;
--Empezamos con la arquitectura
architecture comportamiento of Octal is
begin
process(B8)
        begin
            if B8 = 0 then
                Binario <= "0000";
            elsif B8 = 1 then
                Binario <= "0001";
            elsif B8 = 2 then
                Binario <= "0010";
            elsif B8 = 3 then
                Binario <= "0011";
            elsif B8 = 4 then
                Binario <= "0100";
            elsif B8 = 5 then
                Binario <= "0101";
            elsif B8 = 6 then
                Binario <= "0110";
            elsif B8 = 7 then
                Binario <= "0111";
            elsif B8 = 10 then
                Binario <= "1000";
            elsif B8 = 11 then
                Binario <= "1001";
            elsif B8 = 12 then
                Binario <= "1010";
            elsif B8 = 13 then
                Binario <= "1011";
            elsif B8 = 14 then
                Binario <= "1100";
            elsif B8 = 15 then
                Binario <= "1101";
            elsif B8 = 16 then
                Binario <= "1110";
            elsif B8 = 17 then
                Binario <= "1111";
            end if;
    end process;

end comportamiento;

I don't know why, but it's something wrong on the waveform. This is an octal to binary VHDL code. Thank you.

EDIT:
I change the value from B8 to "range 0 to 17" but it mismatched in the waveform:


texts: Buck Converter Capacitor and Inductor Characteristics

texts:
I'm trying to make a buck converter with this mickey-mouse MC34063A chip that will step-down +5V to +3V3 up to 500 milliamps. I've gone through the calculations by hand and validated them with an online calculator as well. My PCB works great with small loads, but with loads of around 300+ milliamps the voltage starts to taper significantly.

Considering this, I'm guessing that the ESR and ripple characteristics of the output capacitor were chosen poorly by me. My question is about the output capacitor and inductor characteristics: what ESR values should I be looking for in the inductor and capacitor? People keep saying "keep it low", but what is actually "low"?

For reference here is the capacitor and inductor that I used:

Capacitor: https://www.digikey.com/product-detail/en/panasonic-electronic-components/EEE-FT1V680AP/PCE5015CT-ND/2652070

Inductor: https://www.digikey.com/product-detail/en/bourns-inc/SRP1250-6R0M/SRP1250-6R0MCT-ND/3767942

//------As requested, here is the schematic, PCB layout, and more context------//

// Frequency - 100KHz
// Peak Current - 1A
// Input - DC bench power supply (30V/10A max)
// Load - Various loads drawing anywhere from 0 - 500mA.

My scope shows 200mV pk to pk ripple on the output, and the switching waveform on the inductor side looks like pork and beans.


texts:
I have a problem with LI-ION technology.

I'm planning to use four 18650 cells in series, and I want to build a circuit for charging them. The final application is a sort of small UPS; I should keep the 18650 batteries charged and, when the main power goes off, switch to the 18650 batteries; when the power comes back the power switches back to the main adapter and the batteries can be charged again.

As far as I know, the four cells should always be balanced, but I haven't found any IC producer (TI, Analog, Maxim, Linear, Microchip) that offers a charger with cell balancing.

So, here are my questions:

Is there any IC capable of charging four li-ion cells in series keeping them balanced?
I found some cheap balanced charger on ebay (just search for BC-4S15D). Will this fit my needs (so charge and balance four 18650 batteries and keep them charged until needed)?

Thank you

EDIT: Another idea came to my mind: could I use "floating" grounds to charge each battery separately? I mean, one single battery assemble is

one 18650 battery
one 5V li-ion charger (e.g. one based on a TP4056)
one step down converter (e.g. this)

Then these assemblies are attached in series, and all the positives (only positives) of the step down converters are attached to a 24V supply.

I mean something like this

simulate this circuit – Schematic created using CircuitLab

Since the max voltage on the "last ground" is 12.6V, the 24V input has enough room to generate the 5V voltage.

Do you think this design can have some problems?


texts: Improve the frequency of Current Source Howland effect Op-Amp

texts:
I need help on a Howland Effect circuit with a current source purpose with an output of 600mA and a constant gain throughout a range of frequencies starting in 0Hz to 1Mhz. I am currently using an OPA564 with 17 Mhz response but my cutoff frequency is around 87kHz.

Figure 2 represents the Gain and Phase resulting of the circuit shown in figure 1 with the OPA564 Op-Amp with a +/- 6,2 V supply and the current limit flag of 10 kOhm.
So my question is how can I improve the performance to get the response with a dropoff only after 1MHz?


texts: How to find the equivalent resistances for each filter so that the cutoff frequencies can be found?

texts:
Hello i am having trouble for this following circuit. (Top circuit in diagram1) The problem i am having is finding how to calculate the cutoff frequencies for the highpass filter and lowpass filter. This is since i am not sure on what equivalent resistance to use for each formula for each filter (fc=1/(2piRC)). For the highpass i just did that R9 was in series with R8 and then in parallel with R7, then in series with R6 to find that eq resistance so:

Req_highpass=((R9+R8)||R7)+R6

However i am not sure if this is correct for one but also i am not sure i can just ignore C6

Although for the lowpass filter i am unsure as how to find the equivalent resistance for the cutoff frequency for the lowpass filter?

Note: I understand i can just place a buffer between it so interaction does not occur between them but i want to know how to calculate it doing it this way

As you can see when V is probed on the bottom half of circuit diagram 1 when using my equivalent resistance for the high pass filter i get what the cutoff frequency is. Note i have tried different resistor values an i always get it matching (for the example below the circuit values used are below this diagram in the bottom circuit)


texts:
I want to use the MCP4922 with my STM32F411RE microcontroller. I am working on the data that will be sent over SPI. A write command to the MCP4922 consists of 16 bits. First 4 bits for the configuration and the last 12 are data bits.

uint8_t data[2];

This is the decleration of the data variables
I put a 1 in the SHDN configuration of the MCP4922 -> 0001 0000 = data1.
At the end I want to generate a sine wave, so I implemented a sine table like this:

    uint16_t sine_wave[] =
{
0x800,0x900,0x9fd,0xaf1,0xbda,0xcb3,0xd79,0xe29,
0xec0,0xf3c,0xf9b,0xfdb,0xffb,0xffb,0xfdb,0xf9b,
0xf3c,0xec0,0xe29,0xd79,0xcb3,0xbda,0xaf1,0x9fd,
0x900,0x800,0x6ff,0x602,0x50e,0x425,0x34c,0x286,
0x1d6,0x13f,0xc3,0x64,0x24,0x4,0x4,0x24,
0x64,0xc3,0x13f,0x1d6,0x286,0x34c,0x425,0x50e,
0x602,0x6ff,0x800
};

Now I want to put my sine table values in the data bits of data1 and data[0].

    void MCP4922_SendByte(uint16_t dac_data)
{

  data[1] |= (0x01 << 4);
  data[1] |= ((dac_data >> 8) & 0x0f);

  data[0] |= dac_data;

  HAL_GPIO_WritePin(GPIOA, SPI1_LDAC_Pin,1);

  HAL_GPIO_WritePin(GPIOA, SPI1_CS_Pin, 0);

  HAL_SPI_Transmit(&hspi1,data, 1, HAL_MAX_DELAY);

  HAL_GPIO_WritePin(GPIOA, SPI1_CS_Pin, 1);

  HAL_GPIO_TogglePin(GPIOA, SPI1_LDAC_Pin);

}

But the values I have on my SPI line are not as expected.

For example the first value 0x800, I want to send 0x1800
-> 0001 1000 0000 0000

The transmit function is initialized as 16 Bit so data1 and data[0] getting transferred. Somehow my bitwise operations are not working but I don't know why. I found exactly this way here. https://github.com/murjay/MCP4922-DAC-Driver/blob/master/MCP4922_DAC_driver.c


texts: What are the jitter characteristics of PLLs internal to Stratix V FPGAs?

texts:
I am interested in knowing the deterministic and random jitter characteristics of PLLs internal to Stratix V FPGAs. I have looked through the Stratix V handbook but could not find numbers quantifying the jitter of their PLLs.

What are the jitter characteristics of PLLs in Stratix V FPGAs?


texts: What does 0 and 1 mean in logic gate (NOT gate to be specific here)

texts:
When the input to a NOT gate is 1, the output is 0. When the input is 0, the output is 1.

Now, does the input being 0 mean that no current is flowing into the gate and then out of the gate towards the load? And does the input being 1 mean that current is flowing into the gate and then out towards the load?

If it does mean this then i have a question. When the input of NOT gate is 0 i.e current is not flowing into the NOT gate then how can the output be 1 i.e current is flowing out of the NOT gate.


texts: Inductor core permeability much lower than expected

texts:
I am interested in creating an inductor with a large inductance/large mag field in core.  However, when empirically measuring the inductance of the wound core, I calculated a relative permeability ~1000x less than expected (2-6 vs 2000).  My question is whether this is due to an error in my setup/calculations/understanding, or due to receiving a core not up to spec.

The ferrite rod has stated relative permeability of ~2000 and B_sat of .49T (4900G).  The physical dimensions are 25.66mm height x 6.32mm diam.  http://www.ebay.com/itm/5-ea-Ferrite-Rod-Core-0-25x1-00-Fair-Rite-4077276011-2000u-Perm-Plain-Slug-77-/251653543001?hash=item3a97b85459

Given that this is ferrite, the permeability should be fairly linear.  The datasheet for the material can be found here: http://www.mouser.com/ds/2/150/4077276011-476454.pdf

I wound the core with ~100 turns of 28AWG mag wire (.321mm diameter), with a DC resistance of 1.0 ohm.  The result is quite messy, but the length of the coil extends 11.6mm, and the outer diameter goes up to 10.3mm:

The inductance of the coil was measured experimentally by creating an RL series circuit fed by a signal generator, and increasing the frequency until the Vpp across the RL circuit was twice the Vpp across the resistor alone.  See http://www.daycounter.com/Articles/How-To-Measure-Inductance.phtml for an explanation of this method.

For a 100 ohm 1% tolerance resistor, the required frequency was 77kHz, resulting in a measured inductance of 358uH.  I used the following equations to calculate relative permeability \$\mu_r\$.  The geometry is neither a loop or solenoid, but the equations only differ by a factor of 2-3x in this case.

\$B_{loop,center} = \mu_0\mu_r\frac{NI}{2R}\$

\$B_{solenoid,center} = \mu_0\mu_r\frac{NI}{l}\$

\$L_{loop} \approx \mu_0\mu_rN^2R(ln(\frac{8R}{r})-2)\$, r = wire radius

\$L_{solenoid} = \mu_0\mu_r\frac{N^2A}{l}\$

Because there is at least 150 ohm in serial with the 2Vpp source, the most current that could flow in one direction is 1/150 = 6.7mA.  Assuming the relative permeability is 2000 as stated, there shouldn't be any concern of saturation, as the magnetic field in the center of the loop/coil is at most .28T (\$B_{loop,center}\$ with R=3mm).  (Also, the scoped sine waves were clean.)

Given the dimensions from above and the measured L of 358uH, \$\mu_r\$ comes out to 2-6, much less than the expected 2000.  Why is this?


texts:
Is there any benefit to measuring joules in a smart battery in addition to/instead of coulombs?

I'm currently integrating:

microjoules <= milliamps * volts * milliseconds

But the standard seems to be more:

microcoulombs <= milliamps * milliseconds

I guess the latter approach makes it easy to count nominal cycles?  So for a 100mAhr battery:

nominal_coulombs_per_charge = (100mA * hr) * (3600 s / hr) * (1 A / 1000mA) => 360C

approx_num_charge_cycles = accumulated_coulombs / nominal_coulombs_per_charge


texts: How to model a one-port (reflection) measurement in SPICE?

texts:
I have the equivalent circuit for an antenna and I would like to use SPICE to simulate the \$S_{11}\$ (reflection coefficient) response.

I know how to simulate two-port measurements (like shown here), but how would I simulate a one-port measurement?


texts:
I have MPPSolar PCM5048 MPPT which is connected between the solar panels and the batteries. It was working well until yesterday as a sudden it reads negative amps on the battery current. it keeps changing values between (-0.5 to -4 amps at 8 am. while this read should be the same but positive).

Note: I get the negative read on the Battery Current display

MPPT IN and OUT reads:

note: these reads at 8 am while the inverter is off. "no loads on the battery bank"

voltage input: between 90 - 100v
Voltage output: between 24 - 27v
Amps input: between 1 - 3 amps "positive" (depending on day time and battery State of charge percentage).
Amps output: between 3 - 5 amps "positive" (again depends on battery SOC and load).

Things I did.

1- I switched off the power inverter to make sure there is no load on the batteries. the result was getting a read between (-6 and -10 amps).

2- I switched off the breaker between the MPPT and the batteries. The result was getting a read between (-18 and -22 amps).

3- I unplugged the batteries and turned off the breaker between the panels and the MPPT and let them for 6 hours. the result was the batteries voltage was 13.1v each. (the batteries are in a good condition)

4- I re-plugged the batteries and switched on the breaker and the problem still the same.

Questions

What could cause this issue?
Is it possible that the mppt gets a faulty read? what to do if it does get a faulty read?
Anyway to reset the MPPT other than unplugging it?
Could something else other than the MPPT cause this problem?


texts: Connection between MDB Peripheral and Arduino

texts:
I'm working on making a custom vending machine controller using an Arduino as the master. The bill acceptor I'm using implements the MDB communication protocal, which is (I think) a variant of RS-485.

The MDB specs say that the communication is a current loop system. (https://reaktor23.org/_media/projekte/mate_dealer/mdb_version_4-2.pdf section 4.2 page 53) I've successfully sent the reset command using an Arduino's serial port and a transistor to handle the current. However, I am not receiving any information back from the peripheral when I should be receiving ACK (0x00).

I have a transistor with the base pulled high to 5v and connected directly to the peripheral's transmit line. The collector is connected to 5v and the emitter is connected to the Arduino's Rx pin and pulled down to ground with a 1k resistor. The Arduino's ground is tied to the communications common on the peripheral. According to the recommended setup on page 60 of the MDB spec sheet, this setup is what should work. However, I'm still not getting any data back from the peripheral.

The only reason I know the reset is working is because the status LED resets and the motors start up.

If anyone could look at the MDB spec sheet's recommended circuit and reccomend a new or improved setup or just point out anything I missed, that would be great.


texts: IGBT(Insulated-gate bipolar transistor) Latch-up

texts: What will happen if the Parasitic transistor turn on?


texts: what is typical car alternator inductance?

texts: Anyone know the typical line-to-line inductance of a car alternator? I'm looking for a cheap stator to use as a 3-phase high-current inductor.


texts: Measuring mOhm resistance using LT006 precision amplifier and 4-Wire Method

texts:
I am trying to use the 4-wire method to measure the resistance of small strip of carbon steel, which will have a resistance of about 0.3 mOhms. I am currently trying to test my circuit with a known 0.3 mOhms resistor. I am using the Arduino to make the measurements. I have a 5V supply and the circuit has a resistance of 150 Ohms, giving 33 mA current. The potential drop across the 0.3 mOhms resistor is expected to be 9.9 uV. This is amplified by the LT1006 by a gain of 1000. I am using oversampling (https://gumroad.com/l/eRCaGuy_NewAnalogRead) to achieve a resolution of 16-bits, so I a gain of 1000 should be sufficient.

A schematic of my circuit is shown below

I expect the resistor of the sensor to be given by V_sensor/V_100 * 100 Ohms.

I have used the circuit to measure 100 Ohms and 220 Ohms resistances successfully, using a gain of unity on the LT1006.

However, the issue is that the V_sensor I am measuring with the 0.3 mOhms is equal to my input offset voltage (0.002), i.e. its the same value as when the inputs of the LT1006 are shorted together. I have used a 10k pot to null the offset. But it only reduces it to 0.002 V.

Also, is it possible to achieve a higher gain on the voltage across the sensor, by replacing the 10 kOhms resistors on the LT1006 inputs by 100 Ohms. I read here (Kelvin "4 Wire" Resistance PCB Design Questions) that the input resistance for the 4-wire method should be 10 k.


texts:
I am working on a project that will output either NTSC or PAL video.

The video is mainly text (color and Hebrew text) on top of a background image (that I need to download to the microcontroller).

The board has a UART input and a PAL/NTSC output and according to the UART input different text is displayed (very slow rate).

If it wasn't for the background requirement I would probably try to implement the many hobby projects using a resistor ladder to output composite video using a simple microcontroller but that is not an option.

I did not find much information on making a cheap and relatively easy solution on the internet so what components would you recommend for this circuit?


texts: What is the purpose of irregularly shaped SMD pads?

texts:
Looking at a this buttons recommended footprint, I found these irregularly shaped pads:

The protrusions from the pads are way to small to act as solder thieves, and the button itself has gull wing pins that don't mimic the form of those pads in any way:

What is the purpose of the odd shape of those pads? Is there any reason why I shouldn't just draw those pads as rectangles on my PCB layout?


texts: What is the value of Va,Vb and Vc by using nodal analysis?

texts: Can i directly put the Vb value as 12v or is there any supernode in there? I tried applying KCL at Va,Vb (which i put as 12v) and Vc but got the wrong answer.


texts: Charge at 24v and discharge at 12v for battery system

texts:
Is my thinking correct.

Below is a simple diagram of the concept I want to check.

Is this:
1: Possible
2: Feasible? I.E are there any concerns or foreseen issues with this design?

Edit:


texts: A question on single-sided baseband signals

texts: Can anyone provide insight on whether a radar is able to exploit a real baseband signal that has a single-sided spectrum?


texts:
I'm looking for a multiplexer IC with 128:1 or more inputs (256 would be quite nice). I would have thought such a device would be quite common yet I'm having a tough time locating it. It could be that I'm looking at the wrong places but somehow I think I'm missing something - perhaps large input multiplexers are not used that often? If so, what is the alternative?

The max. I was able to find is the trusty ol' 74150 with 16 inputs.

I understand that I can build a large multiplexer by combining multiple 16 input mux - but I'm hoping for a more integrated solution.

I'm designing a circuit thats able to test for open and short circuits in an automotive wiring harness. A typical harness can contain 200 or so wires. Currently, the circuit uses 16 multiplexers to handle 128 wires.

The multiplexers are connected to a single 16-input multiplexer and that in turn is connected to a uC. Similarly, on the other end, there are 16 demultiplexers. The demultiplexers switch the wires onto a voltage. At the same time, this wire is switched onto one of the uC input via the mux.

If the wire is OK, the uC should see a high at its input. The uC then checks all the other wires. If any of them is high, it means there is a short between those two wires.

Note: this circuit was not designed by me. This was done in 2003. I am just looking to improve this circuit. Also note that none of the wiring harnesses contain a CAN data-bus or any other sort of bus. Its just simple wires for power and signals.

Here is a very rough block diagram that I quickly made just for this post. I hope this makes the problem clearer as English isn't my first language and I have trouble explaining things via text. Even though the diagram isn't very good, I hope it makes things better. The lines going side-ways into the demux and mux from the MCU are the address lines.

Note that one of the wires is split into 3. I made this intentionally to show that some connections are one-to-many and not just one-to-one. The most complex one I've seen is a wire split into 60 junctions. This is why the demux and mux have separate address lines. The demux could be at input no. 20 whereas the mux can switch between 20,21,22 etc. Check all the lines that are junctioned from line 20.

If you feel there is a better way to design this, please let me know.


texts: How much capacitance do I need in the input of LM78L05

texts:
I want to use LM78L05 as a fixed output voltage regulator as shown in the datasheet, as I cited below. My regulator is 2 meters away from the power supply filter. My input voltage is 24V, however this is an automotive application, so I have a transient voltage suppressor  of 33V in the input too.

Edit:

I thought I wrote about the current, but I was wrong. I am going to pull at most 5 mA of current. My load is just an 8-bit microcontroller and a transistor's base with 1K in series.

I know that I need at least a 10nF capacitor load in the output to limit high frequency noise, as per Note 4 in the electrical characteristics table. However, I am confused if I need a low value (220nF to 1\$\mu\$F) capacitor in the input for decoupling (or bypassing?) purposes, or for just bulk purposes. I saw only those values in the datasheet, not  higher.

This stated, can I use only a 10\$\mu\$F electrolytic capacitor in the input and a 150nF polyester capacitor on the output as shown? If I do, will I encounter any problems?


texts:
For my Engineering class we were tasked with building something to improve safety. My partner and I chose to build a faulty light indicator to tell you when your cars lights weren’t working, or when they were faulty. I just wanted some input on what type of circuits we should use or what components we could use to build this?

We wanted our Faulty Light Indicator to have to have a warning light to tell you when one of the lights in the car wasn’t working. So something like a current sense amplifier to tell you when there was no current flowing through the circuit, and it would alert you by turning on an LED. Any help would be appreciated, thank you.


texts:
The Voltage thresholds \$V_{OH},\ V_{OL},\ V_{IH},\ V_{IL}\$ as far as I understood, they represent,

\$ V_{OH}\$ ~ The sender must produce a voltage above \$ V_{OH}\$ for sending a \$1\$
\$ V_{OL}\$ ~ The sender must produce a voltage below \$ V_{OL}\$ for sending a \$0\$
\$ V_{IH}\$ ~ The receiver must treat all voltages above \$ V_{IH}\$ as \$1\$
\$ V_{IL}\$ ~ The receiver must treat all voltages above \$ V_{IL}\$ as \$0\$

Questions:

(Notations) Shouldn't the subscripts be the other way? (i.e) \$V_{OH}\$ must be \$V_{IH}\$, since \$V_{OutputHigh}\$ is associated with sender, it must be  input high, not output high, similarly for all the others.
In this lecture (48:00) (MIT OCW Anant Agarwal), he checks the standards for a NOT gate that he constructed using a MOSFET as a switch. I don't understand how he checks the standards. Which one is the sender, which one is the receiver? He compares the \$ V_{OH}\$ & \$ V_{OL}\$ with \$V_{out}\$ curve and \$ V_{IH}\$ \$ V_{IL}\$ with \$V_{in}\$ curve, which again takes me to the first question. Don't the thresholds apply only to the interval in which the signal pass from one input element to other, so how does he check the standards with the curve (v_out) that is obtained after processing the signal given by an element.


texts: verilog program will only work if sensitivity list is (posedge clock)

texts:
I have a program in Quartus Lite 19.1 that will only work if a particular always block uses posedge of clock sensitivity. If I try to use an (star) sensitivity list then it does not, even though this makes more sense.
My program takes in 32 bits of data and a write signal. The Fpga takes the 32 bits where [31:24] are an op code and [7:0] are the actual data, and stores them in wires. Another always block decodes the top most bits (opcode) and writes according to the opcode. This is the block that needs to have the posedge clock sensitivity. I do not understand why this is the case. I originally had it as a (*) sensitivity list and it took me forever to realize that this was the problem.
I think there is some fundamental reason that this does not work and I cannot see it. I have posted a part of the code below. Note the last always block does work without posedge of clock sensitivity, which confuses me even more.
assign opcode = temp_op[31:24];
assign write_data = temp_data[7:0];

always @(posedge clock) begin
    if (write) begin
        temp_op <= D;
        temp_data <= D;
    end
end

//decode input
always @(posedge clock) begin //has to be posedge clock otherwise it will not work
      if (opcode == 8'b00000010) Enc_delay <= write_data & delay_mask;
      else if (opcode == 8'b00000001) mode <= write_data & mode_mask;
      else pulse_width <= write_data & pulse_width_mask;
end

//decode delay
 always @ (Enc_delay) begin
      if (Enc_delay == 8'b00000001) delay = 250;//5us
      else if (Enc_delay == 8'b00000010) delay = 500;//10us
  else if (Enc_delay == 8'b00000011) delay = 1000;//20us
      else delay = 8'd125;    end //2.5us

Update:
I have not simulated, which I know is bad but I am monitoring the outputs which I have routed out through pins (using DE10 nano development board). My program is a pulse width generator with variable delay, pulse width and different modes for triggering the pulses. When I say it does not work, I mean I get no signals at my outputs.


texts: Improve my “From NAND to Tetris” ALU in VHDL

texts:
I'm following the course From NAND to Tetris, but instead of using the author's software, I'm trying to directly program a Spartan 6 FPGA. I'm now solving the ALU exercise, and ended up writing the following code (disclaimer: I started learning VHDL yesterday):

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity alu is
    Port (x  : in  STD_LOGIC_VECTOR(15 downto 0);
          y  : in  STD_LOGIC_VECTOR(15 downto 0);

          zx : in  STD_LOGIC;
          nx : in  STD_LOGIC;
          zy : in  STD_LOGIC;
          ny : in  STD_LOGIC;
           f : in  STD_LOGIC;
          no : in  STD_LOGIC;

          output : out STD_LOGIC_VECTOR(15 downto 0);
          zr     : out STD_LOGIC;
          ng     : out STD_LOGIC);

             constant zeros: STD_LOGIC_VECTOR(15 downto 0) := "0000000000000000";
end alu;

architecture Behavioral of alu is
begin
    op: process(x, y, zx, nx, zy, ny, f, no)
      variable px: STD_LOGIC_VECTOR(15 downto 0);
      variable py: STD_LOGIC_VECTOR(15 downto 0);
      variable po: STD_LOGIC_VECTOR(15 downto 0);
    begin
      px := x;
      py := y;

      px := zeros   when (zx = '1');
      px := not(px) when (nx = '1');
      py := zeros   when (zy = '1');
      py := not(py) when (ny = '1');

      if (f = '1') then
        po := (px + py);
      else
        po := (px AND py);
     end if;

      po := not(po) when (no = '1');
      output <= po;

     if (po = zeros) then
        zr <= '1';
      else
        zr <= '0';
      end if;

      ng <= po(0);
    end process;
end Behavioral;

I'm now wondering if there is a simpler way to achieve the same thing, considering:

(VHDL) Good practices;
(VHDL) Code size;
Using as little sequential logic as possible;
Synthesis size.


texts: Soldering specific wire, solder won't stick + makes iron tip black

texts:
When I solder a specific wire, solder won't stick and it leaves my iron tip black.

With many years of hobby electronics, I have never experienced this before.
The wire is from a silicone encased LED strip and is dull silver in colour.  I stripped back the silicone so that the wires were sticking out in free air.  On attempting to solder them, I have the following issues:

The solder won't stick.  I've tried scraping the wire to remove any coating, rubbing with my flux pen etc, but no luck.  The wire has been hot enough to melt solder when touching only the wire, so plenty of heat.
The iron tip goes black.  It appears as though anywhere that the solder "blob" has touched the iron and wire, the tip ends up black (not happy).

I'm not using any exotic solder.  And like I said, I'm not new to this, but this has me stumped.

Has anyone seen this before?  Can you offer any suggestions?  At this point I don't want to go near it again without an idea of what I'm up against.

Additional info:

Solder type: Rosin core
Flux type: No clean? (http://www.newark.com/itw-chemtronics/cw8100/flux-dispensing-pen-no-clean-9g/dp/00Z1870)
Wire is NOT magnetic


texts: ARM Programming interface and tool chain

texts:
I have acquired a RM48L952 that is an ARM Cortex R4F from TI and I would like to start learning ARM development with this chip. My question is can I use any JTAG programmer to program it? Something like a Open DIY JTAG Programmer or does it have to be a brand specific one? The same applies for the tool chain, can I use gcc or do I have to use brand specific compiler?

Thank you


texts:
I've seen a couple of very similar questions but the answers don't answer my question:

DDR2 CAS Latency - is it fixed to clock-cycles or time?

What limits the lower bound of DRAM CAS latency

In my current understanding once a row in DRAM bank has been activated then it's just a matter of the values registered on the amplifiers to be latched out to the output and this process is synchronized by the clock, so it should be specified in clock cycles how long it takes to read a column from an active row.

Yet it appears CAS is time-based, e.g. this datasheet has CAS=1 for 166MHz, CAS=2 for 100MHz, CAS=3 for 50MHz and has CAS configurable, which in my understanding should be a constant number of clock cycles regardless of the clock frequency.

What is wrong with my understanding? What analog process the column reads in DRAM depend on?

Edit: researching on this a bit more I've found there's t_CAC, the time between the CAS pin is driven low and valid data is available on the data pins. Then t_CAS is always measured in a whole number of clock cycles and should be t_CAS >= t_CAC.
This makes me think the read process is actually asynchronous with purely combinational logic in between the sense amplifiers and the CAS pin and the data pins. Is this correct?


texts: M2S150 Smartfusion2 SPI Flash Format Issue

texts:
I am currently using the M2S150 Development kit (from microsemi), and am trying to get the SPI Flash to work as a USB mass storage device when I plug the board into my computer.
I am running through the code provided by microsemi from the libero IDE (CM3_EWARM_usb_device_msd specifically) The code compiles correctly, and the board shows up as a Flash Drive on my computer. I can even see that the drive size is correct (1GB) in diskpart. However, when I double click on the drive in windows explorer to format the drive, or attempt to format the drive via diskpart windows says it is unable to complete the format after getting through the entire format (format percent gets to 100, but after windows throws an error) Would anyone know why this problem is happening, or how I could begin to debug this issue?
I've tried using diskpart to clean the Flash, and then format the drive, but the issue persists.
Libero Version : 12.1
IAR Version: 7.8
Board: Smartfusion2 M2S150
Windows Versions: Windows 10


texts:
I am creating a basic RISC processing core on a FPGA development board (Nexys A7-100t).
I created a RAM block that will be used to store the instructions that my basic processor will execute to run a simple program. I have attached the file code for my RAM block below. Note it is not complete or been tested / compiled so there will be errors but it is just there to give you an idea of the RAM blocks functionality.
This code in theory generates the logic for accessing / sorting data but it doesn't initialize the RAM memory contents to hold the binary instructions.
My question is how could I initialize the RAM block upon power up or FPGA configuration?
My initial thoughts tells me I have the following options:

Generate the data 'manually' with VHDL code and LUT to write the data bytes to the RAM block. This might be the easiest option as there may only be approx 100 memory locations which are 32 bits wide.

Maybe Xilinx provides functionality to achieve this. I am not sure.

Use an SD card with the on-board SD card reader on the development board. Again unsure if this is viable.

Use an EEPROM to store the instructions and upon power up, write this data to the RAM block. I imagine this is no different than method 1. except for the hassle of reading the EEPROM contents serially while still having to load the data 'manually'. I do like the sound of using an EEPROM though.

I am interested to hear how everyone would do this. This is an academic project so doesn't require high speed, just low complexity and something repeatable.
Thanks for any help everyone!
RAM block VHDL file

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
--add other required library files that holds 'Data_width' constant

entity RAM_Block
 Port ( RAM_Address : in std_logic_vector (Data_width-1 downto 0));
        Data_in  : in std_logic_vector (Data_width-1 downto 0));
        Clock : in std_logic;
        Enable : in std_logic;
        Data_out : out std_logic_vector (Data_width-1 downto 0));
end RAM_Block;

architecture Behavioral of RAM_Block is

type memory is array (0 to 100) of std_logic_vector (Data_width-1 downto 0);
signal RAM : memory;
variable RAM_Address_int integer := 0;
signal RAM_output : std_logic_vector (Data_width-1 downto 0);

component Enabler_Block is
 Port ( D : in std_logic_vector(Data_width-1 downto 0);
        Enable : in std_logic;
        Q : in std_logic_vector(Data_width-1 downto 0));
end component;

begin

Enabler_Block_instance port map (D => RAM_output , Enable => Enable , Q => Data_out);

RAM_Address_int <= conv_integer(unsigned(RAM_Address));

   Process (Clock , Enable)

    begin

     if(rising_edge(Clock) and Clock = '1') then
        RAM(RAM_Address_int) <= Data_in;

     end if;

     if(rising_edge(Enable) and Enable = '1') then
        RAM_output <= RAM(RAM_Address_int);

     end if;

    end Process;

end Behavioral;


texts: Review of: voltmeter, ampmeter, ohmmeter circuits for Arduino

texts:
I'd like to build a multimeter with an Arduino Due. Could you review the following circuits and tell me what I should improve?

Voltmeter

Requirements:

Ranges: -30V -> 30V, split into a) -30->30V b) -12->12V c) -6->6V c) -3->3V and another set without the negative voltages to double the accuracy
Accuracy: 1% of voltage range, e.g. 0.3V max on highest range (see above)
Bandwidth: 400kHz

Circuit:

simulate this circuit – Schematic created using CircuitLab

Ampmeter

Requirements:

Ranges: -5A->5A, split into a) -5->5A b) -1A->1A c) -200mA->200mA and another set without the negative currents to double the accuracy
Accuracy: 1% of current range, e.g. 50mA max on highest range (see above)
Bandwidth: 100kHz

Circuit:

simulate this circuit

Ohmmeter

Requirements:

Ranges: a) 0->1k b) 1k->10k c) 10k->100k d) 100k->1M
Accuracy: 1% of resistance range, e.g. 10k on highest range (see above)

Circuit:

simulate this circuit

All resistors are 0.1%, calibration will be done via offsets in software. Any suggestions on different circuits, different parts...? I'd like to keep the cost low, like ~15$ for 6 voltmeters, 3 ampmeters and 1 ohmmeter circuits. Apparently the ACS712 is ~1.6$ on ebay.


texts:
I am designing a system around a bus using DIN 41612 connectors. I have come up with the following pinout for my connector taking into account the following requirements :

Each signal pin should have a ground pin next to it for better ground return paths
The boards is rated at 30W coming from the 12V pins of the connector.

With this design, 12V pins shouldn't exceed 625mA as each pins of the connector can handle 2A of current.
Is this a good pinout or am I missing something ?
Thanks !


texts: What is the "leakage current" between signal and shield?

texts:
Consider a coaxial cable with shield not connected to anything. My textbook seems to suggest that there will be leakage current between the "signal" and the "shield".

I have two questions:

1) When the shield isn't connected to anything, how can any current be there and where will the current flow to?

2) How does connecting the shield to common mode voltage reduce both leakage current and capacitance?


texts: Handling a multiplexed bidirectional data bus in VHDL

texts:
Ok, I am a self-taught novice playing with an FPGA and VHDL. I have successfully implemented a number of projects using I/O but only unidirectional. Pins are either in or out but not inout.

I am now wanting to interface with an external device that has an 8-bit bi-directional data bus. To further complicate things, this bi-directional bus is multiplexed with the address bus.

On the low part of the device's clock cycle it will alway output the upper 8-bits of a 24-bit address on the data bus. The lower 16 bits are not valid at that time. At the high part of the cycle it will either drive data out or read it in. There is an active low write enable (RW) signal to indicate the direction. The lower 16 bits of the data bus are also valid at this time.

The FPGA is generating the clock for the device so I have access to the clock signal. I would also like to separate the data into two 8-bit buses to use internally, One for read and one for write.

So, I need to set the pins to input and latch the upper part of the address during the clock low period, and then during the clock high period I need to set the pins to input or output and tristate when appropriate depending on the RW signal. So, basically a VHDL version of the schematic below.

simulate this circuit – Schematic created using CircuitLab

I would provide some VHDL I have tried but I'm not sure of which of the 20 different attempts to post.

Oh, and if anyone has any tips on properly driving simulated external inout signals during simulation, that would also be helpful. I am working with ISim which is part of the Xilinx ISE.

Update:

Thanks to @Humpawumpa I think I have this figured out.  Looks like my problem was incorrectly handling the high-impedance state of the inout pin, and on top of that because of my incorrect understanding of when and where to set high-impedance, I was also setting up my simulation stimulus all wrong.

This is the code I have come up with incorporating Humpawumpa's answer and it looks right in the simulator. Hooray!

    entity addressDemux is
    port
    (
        phi2 : in std_logic;
        rw : in std_logic;
        data_io : inout std_logic_vector(7 downto 0);
        addr_low_in : in std_logic_vector(15 downto 0);

        addr_hi_p : out std_logic_vector(7 downto 0);
        input_p : out std_logic_vector(7 downto 0);
        output_p: in std_logic_vector(7 downto 0);
        addr_full_p : out std_logic_vector(23 downto 0)
    );
end addressDemux;

architecture struct of addressDemux is

    signal addr_hi : std_logic_vector(7 downto 0);
    signal input : std_logic_vector(7 downto 0) := (others => '0');
    signal output : std_logic_vector(7 downto 0);
    signal addr_low : std_logic_vector(15 downto 0) := (others => '0');

begin

    addr_hi <= data_io when phi2 = '0';
    data_io <= output when phi2 = '1' and rw = '0' else (others => 'Z');
    input <= data_io when phi2 = '1' and rw = '1';
    addr_low <= addr_low_in when phi2 = '1';

    addr_hi_p <= addr_hi;
    addr_full_p(23 downto 16) <= addr_hi;
    addr_full_p(15 downto 0) <= addr_low;
    input_p <= input;
    output <= output_p;

end struct;

So basically what was tripping me up was setting the inout pin data_io to high impedance. Coming from a software development background setting data_io to 'Z' on the clock high period and then reading data from it was confusing me. In software setting a variable to some value does not give you a different value when you read it back. So I was thinking if I set it to 'Z' my input would be 'Z' when I read it. It's all just code right, LOL. Lots to unlearn I guess.


texts: minimum readable rise/fall times in an oscilloscope

texts: How can I calculate minimum readable rise/fall times of a signal in an oscilloscope (from practical point of view)? Does it depend just to bandwidth and sampling rate of oscilloscope? regards


texts: Wrong value in the W-register after a MOVF operation

texts:
How do I resolve obtaining the wrong value in the W-register after a MOVF operation?
I am debugging a code which builds & programs successfully, but does not have the desired result when powered up as part of the circuit and I have noticed that the working register does not contain the right value after a MOVF operation, whilst debugging.
If the value that is being copied to the W-reg is manually written in during debugging, then the code functions as it should.
The following images, I believe, illustrate the my issue quite well.

1. Port definition.

2. LEDportA value of 0x02 is to be moved to the W-reg.

3. After the operation, W-reg contains 0x00, instead of 0x02.

4. Final image shows that LEDportA is the same as LATA, as it is cleared after the "clrf LEDportA instruction.
I am totally bewildered as to what could be causing it and any insights or advice that anyone can provide will be very much appreciated.
Please note that the PIC MCU in use is the PIC16F1829.


texts: Three-phase inverter with or without flyback diode?

texts:
I'm not sure if I really should include flyback diodes or if the body diodes of the Mosfets is enough for a three-phase inverter, used for motor control. The Mosfets I planned to use are the following:

https://www.infineon.com/dgdl/irfh3707pbf.pdf?fileId=5546d462533600a40153561a2e0b1e78

The Mosfet is specified for 29A, but I will limit the current to 7A. The PWM frequency will be 25kHz. As far as I can see, the recovery time is fast enough such that it can act as a flyback diode and also the continous current seems with 3.5A to be enough for 7A continous, since the diode will not be always on and the current will drop fast.

Do you think the body diode is enough for this application or should I include schottky diodes as flyback diodes or even take Mosfets with body diodes with higher current ratings?


texts: Adesto DataFlash (AT45DB641E) reads zeros after exercising flash for several minutes

texts:
I am using the AT45DB641B Adesto DataFlash and not in Low Power mode.

In my application I am recording a stream of raw sensor data and constantly writing to flash every second. I have a self-test that is invoked every minute to read back a sentinel from flash to make sure everything is running correctly. However, when I have been running my recording for from between 10 minutes up to 4 hours, at some point the flash would read back all zeros at this sentinel address. This memory address is set once initially and is never modified during the course of the recording.

In my test unit, I exercise heavily erase/program then read back and different set of data and all operations seem to work normally.

I wonder what could possibly cause a flash to read back zeros and that it happens inconsistently.


texts:
In the context of parasitic capacitances in ASIC design. Imagine a net going through Node1. My parasitic extraction gives capacitance C1 to ground and C2 to the power net. What is the total/effective capacitance of the net?

Note, this is not a homework question, and I am not a student.

simulate this circuit – Schematic created using CircuitLab


texts:
I have attached a PSU design which I have created. The input voltage is between 12 and 24V DC.

The first stage creates an isolated output voltage of 7V that is then fed into the two TPS562208DDCT (buck converters) to produce 5V on IC3 and 3.3V on IC2.

The circuit is working as intended, without a load connected to the output. For the test, I removed IC2 and was just working with the 5V output. When I measure the output of the IC3 without a load, then the voltage is 5V as expected.

However when I connect a load that typically draws between 300mA and 550mA, the output of IC3 drops to 2.2V which seems like IC3 is current limiting. According the datasheet of the TPS562208DDCT, the chip can deliver 2A. I have followed the suggested components according to the datasheet.

Any suggestions on changes or corrections that can be made, will be highly appreciated. Thanks in advance.


texts: Why does current have to return to its source in a circuit?

texts:
As far as I know there should be a current when a high potential point is connected to a low potential point, but apparently that is not true. I understand that a circuit must be closed in order for it to flow. I just don't get why a return path to source is essential for creating current.

Why do electrons have to go back in a loop to the source? Shouldn't they just want to move to a point with a different potential, regardless if it's the source or not?


texts:
I'm looking at the datasheet for the TI adc12dl080, it suggests a "quiet" 74ACQ series inverter to complement an output clock signal, presumably to reduce noise coupled into the ADC:

Looking online, I see that these were introduced by the early 1990s, but I can't find a datasheet for that specific part or a way to buy one.  It isn't clear to me how much being "quiet" matters and without a datasheet I'm not sure how to pick something equivalent.  Would a more common 74AC be acceptable here? Actually, elsewhere in the datasheet:

The best logic family to use in systems with A/D converters is one which employs non-saturating transistor designs, or has low noise characteristics, such as the 74LS, 74HC(T) and 74AC(T)Q families. The worst noise generators are logic families that draw the largest supply current transients during clock or signal edges, like the 74F and the 74AC(T) families.

So I should not use the 74AC, and I should find a low noise logic device.  The 74HC04 and 74LS04 are easier to find, but they're too slow, so that doesn't help.


texts: Why is barrier potential of Ideal Diode zero?

texts:
I am learning the basics of semiconductors.
Going through diode equivalent circuits, the material says that Ideal Diodes have a barrier potential of 0 volts. Why is this?

I have understood what a pn junction diode is and how it works, but I cant wrap my head around this.


texts: Identifying an unmarked SMD capacitor and chip

texts:
So I'm setting myself into SMD components, as I want to create my own compact 5v step down converter, based on this component.

I've read that these small brown ceramic capacitors are most likely unpolarised, to my knowledge meaning they can be turned both ways and still do their job just fine. But using my multimeter measuring capacitance, gives the result 8.400 uF and while reversed on the same capacitor gives me the result 26.60 uF.

The other capicators give me a more clear answer when measured 220 uF and when reversed 0 uF.

Does this mean they're polerised and can only be put in one way? I would also very much like to know which kind of chip that could be on the back on this 5v step down converter.

Chip:

The component:
https://www.aliexpress.com/item/3pcs-5W-9V-12V-24V-to-5V-DC-DC-Step-Down-Buck-Converter-Module-replace-TO/32766296476.html?spm=a2g0s.9042311.0.0.27424c4d1qdowf


texts: Is there a text or markup standard for describing a Bill of Materials?

texts:
I'm an electronics newbie, and recently purchased empty PCBs for GoodFET and Ubertooth.

While trying to put together an order for all the parts in the bill of materials, I realized I'd very much like to have a computer parseable format I could dump into a parts search engine like octopart.

I started hacking up a simple website to do this using the octopart API but I can't find any sort of xml standard for a BoM.

Has anyone heard of such a thing? I'd be particularly interested in some sort of standard format that's available from gEDA, EagleCAD, etc


texts: Locally create 3V3 from 5V for small load and uP GPIO

texts:
I am designing a 5V board and i need to read two outputs from the lithium charger using the 3V3-only uP GPIO, while also using them the same output pins to drive user LEDs; charger outputs are either GND or Hi-Z.
While trying to come up with a solution that ticks most boxes (all round optimal for cost, size, footprint, but not best in any regards) i came up with this:

R_LED and G_LED nodes are the charger outputs.
I used these P-mosfets because i already have pleny on the board, thus avoiding an extra part in the BOM.
Datasheets:
battery charger IC
P channel MOSFET
LED to drive
Zener diode

My reasoning:
Zener datasheet states PD max = 500 mW: at Zener voltage of 1.8 V that translates to I max of 277 mA; so i think i can pull 20 mA for each led without issues.
When both input nodes are Hi-Z, zener will drop 1.8V allowing 320 uA to flow through R98, creating a 3.2 V reference for the High state of the 3V3 uP GPIO input (although GPIOs will be connected to this reference voltage via R93 and R94, which concerns me).
When either input node transitions from Hi-Z to GND, uP GPIO which is tied to directly will move from 3.2 V to GND; also, the mosfets will start conducting, turning on the LED.
The questions:
Am i correct in assuming that this will work?
Is there a better way to achieve the same?


texts:
I am having trouble reading data from a pressure sensor using MATLAB. The pressure sensor is connected to an NI 9219 Analog Input Device. Firstly, i tested the device to make sure it is working using NI DAQmx (Measurement and Automation Explorer) software and below is a waveform of an output received :

 So i have tried a couple of things based on comments below, i have done 2 runs of the code changing only the addAnalogInputChannel settings:

1) First Run is using Voltage in the addAnalogInputChannel, i have attached a picture of my workspace and Waveform below:

2) Second Run is using Bridge in the addAnalogInputChannel, i have attached a picture of my workspace and Waveform below:

My previous code is shown below:

%% NI UST-9162 Interface %%
devices = daq.getDevices;
% disp(devices) %Identify devices (NI USB-9162 as 'Dev1')
s = daq.createSession('ni');
ch0 = addAnalogInputChannel(s,'Dev1','ai0','Current'); %Honeywell pressure sensor

%ch0.BridgeMode = 'Full'; %Configures the bridge mode property of Honeywell
%ch0.NominalBridgeResistance = 5000; %Honeywell datasheet suggests 5 kOhm

ch.Coupling = 'DC';
ch.ADCTimingMode = 'HighSpeed';
ch.ExcitationVoltage = 2.5;
s.Rate = 2; %Scan rate per second
s.DurationInSeconds = 2; %Set data collection for S seconds
[data,time] = s.startForeground; %Start test data collection

%% Plot Captured Data %%
figure(1)
clf(figure(1))
grid on

plot(time,data,'-.','linewidth',2)
xlabel('Time (s)')
ylabel('Voltage')
legend('Honeywell')
xlim([0 s.DurationInSeconds])
ylim([-0.03 0.03])

I have listed the equipment below with links to datasheet:

1) Pressure Sensor(Mine is Port Type B with 6G)

2) NI-9219 Analog Input Module

3) MATLAB 2017b with Data Acquisition Tool Box

4) NI DAQmx


texts: Multistage Differential Amplifier Gain Stage Problem

texts:
I have been trying to design an opamp to obtain alpha and beta waves from brain.

So far, I've designed multistage differential amplifier that provides x100 gain approximately.
Inputs are 50uV and 70uV at 30 Hz, the output is about 2mV.

The problem is related to gain stage. Whenever I try to amplify the signal coming from the output, all gain gones.

What is the root of this problem ?

Thanks.

Schematic : https://i.hizliresim.com/rJANdP.jpg


texts:
I am using an MRT511 thermopile temperature sensor and COS77DT for amplifying the temperature sensor output.
I used Recommended circuit in the MRT511 datasheet but output voltage of the op-amp not varied with thermopile sensor. Output voltage is always constant.
Can anyone share mistakes in that circuit?


texts:
Does anyone know a way to get Tango schematics into Eagle? Even if it is a hard way (other than entering from scratch)... Of course, an easy way would be nice.

Cheers,

Marcus


texts:
I have a drone that can plug two 1s batteries. I have the option the plug only one battery but I need to "close" the other battery input with the following (image).

I have no idea how this is called. Mine broke and I need to find an other one.

How is this called?
It a 1s battery connector but with a wire that goes from the positive to the negative.

Edit

I put a better picture. This is the actual part that just broke. Maybe there's an easy way to fix it.


texts:
I need to switch some power to a device, so I was wondering, if this will work OK, or do I need to add some other stuff to protect it, or make it work correctly.
I ran some simulations, on CircuitLab, and according to them this should work, but I would like, the opinion of other professionals.

VCC = 12V (2A)
YELLOW_IN, WHITE_IN = 0-5V, 40mA (PWM from Arduino)
YELLOW, WHITE = VCC

I should also probably put a resistor between the Collector of Q1 and Base of T1.
This schematic is pretty straight forward, when you put 5V to YELLOW_IN it will act as a switch and then the YELLOW will be connected to VCC which is 12V.
Do you see any problems with this schematic or design?

As for this schematic, it acts the same as the other one, except for one more case, I need to be able to supply ~0.4V to WHITE when WHITE_IN is 0.4V, and when WHITE_IN is 5V, it will bridge VCC with WHITE.
But in that case what happens with the voltage/current coming from WHITE_IN.
Do I need to build that part of the circuit differently ?

Edit 1: I've modified the schematics according to the suggestions, is this sufficient now.


texts: how to connect 4 3W RGB in serial together?

texts: I have 4 3W, 6pin RGB with heat sink, I want to connect them in serial, how do I do it, take 2 LED (LED 1, LED 2)for example, should I connect LED 1 (R-) with LED 2 (R+), LED 1 (G-) with LED 2 (G+), LED 1 (B-) with LED 2 (B+)


texts: Probe characteristics- what does CAT 1 and CAT 2 mean?

texts:
What does this mean?

Maximum input voltage : 300 VRMS CAT II

Maximum input voltage : 300 VRMS CAT I


texts: Why would solder paste not wick in completely during reflow?

texts:
I'm using a hot plate to reflow a PCB. Aside from a rather egregious amount of solder paste (this was the second time around, and somewhat intentional), why would solder paste, at temp, not wick in completely? It's leaving behind a mess of the individual grains:

I'm using an IR gun to watch the temp, it gets to about 220C, clearly goes liquid, but then doesn't wick in completely like I see in the various youtube videos.

Could this be a function of paste age?

Edit: Doing some digging on the web, it does seem to be a function of age:

  How does one know if their solder paste is still usable? This can be determined rather easily. As mentioned earlier, one artifact of a degrading paste is a rise in viscosity. So one can perform a simple printing or dispensing test to see if it still performs adequately in that regard. Another aspect that often suffers is coalescence. As the flux degrades it looses its ability to adequately remove oxides on the solder powder. In order to gauge the degradation, it is best to put a small amount of paste on a non-wettable substrate, like a piece of ceramic. Reflow the paste and see how well it coalesces. If coalescence is good, the solder paste will reflow into a ball, surrounded by a flux pool that is relatively free of uncoalesced solder particles. If the paste has significantly degraded, the paste will not coalesce well and there will be a significant amount of uncoalesced solder particles in the flux pool.

http://blogs.indium.com/blog/eric-bastow/solder-paste-expirationshelf-life

The jar of paste (30g) sat in my fridge for probably 18 months.

Edit 2: Age was definitely the issue. Here's what happened on the same board, with the same reflow technique, but new paste:


texts: Cost effect of different component packages during PCB assembly

texts:
We are looking at starting PCB design in house, up until now we have outsource design and manufacture. This means that we have yet to see the real cost of the PCB, components and assembly as discrete items.

Looking at the current PCBs that we have, they currently all use SOIC style of chips, even when QFN parts are available alternatives. Is the reason for this because the legs on SOICs make them easier to use in manufacture? Or is it because the legs on SOICs make life easier for debugging and hand soldering etc?

We are interested in the cost of assembly in large, 100k or 1000k quantities, when produced in a production line with pick and place machines.

I haven't found any difference in the cost of the IC in the different packages, so I don't think that is the reason. But it could be that the difference packages are delivered in different methods; tape and reel vs a tray.

Is there any resource that I can use for estimating which is the cheaper packages or delivery packaging? I've tried a bit of internet searching, and not found anything yet.


texts: Can somebody please explain to me the principle of a T-T Earthing system?

texts:
How are the transformer, consumer's side and the generator earthed in a T-T Earthing system?
I seem to understand that the generator and its frame should be earthed separately; The neutral of the generator is earthed at the site while its frame is connected to an earth bar in the Main Low Voltage Panel (MLVP). Is that correct?
For the transformer, I understand that the supply company provides earthing for the neutral of the transformer at the site. Is that correct?


texts: Some questions about the CN3722 solar charging IC and its MPPT setting

texts:
I'm currently working on a project, where I have to charge batteries by solar. For this reason I chose the CN3722 IC. Since I want to create my own PCB with all the necessary parts I had to read the datasheet in order to wire everything right.
However, I stumbled upon something that confuses me.
The CN3722 IC has one pin labeled "MPPT". One can set the MPP voltage of the solar panel by altering the resistor divider (R8/R3). (see page 2 of the datasheet)
The datasheet also states that a charging cycle only begins, if the following three criterias are met: (the first two are irrelevant for this question)

The voltage at VCC pin rises above the UVLO level
The voltage at VCC pin is greater than the battery voltage by sleep mode release threshold VSLPR
The voltage at VCC pin is no less than the maximum power point voltage set by the external resistors

The last one heavily confuses me. I don't understand why they designed it that way. I know that every solar cell has a different MPP which also depends on other environment factors, like temperature and sunlight intensity.
My questions:

Why doesn't a charging cycle begin, when the MPP voltage isn't reached? Sure, the charger won't operate as efficiently, but it would still generate power, wouldn't it? Why did they design the IC this way? Is there any logical reasoning behind that decision?
I also have a question regarding solar panels. For instance, I bought these cheap solar panels. How can I obtain its MPP voltage (at room temperature I suppose)? Sadly there was no datasheet or similar given...


texts:
We are building a system that needs to have 2 kinds of USB Switch: one momentary (normally closed) and another that is not momentary (like this). We are thinking about doing something like this:

simulate this circuit – Schematic created using CircuitLab

where SW2 will be used as a normally closed switch, R1 will have some value just to avoid short cuircuits and M1 will be a MOSFET, not sure what (we don't really have an electronics background, it's just to complement an embedded systems course project). Before the USB female VCC we are thinking in putting a LED (perhaps). I don't know if I got the MOSFET pins right, but the idea it's this:

If SW1 it's open, nothing goes to USB-F
If SW1 it's closed and SW2 it's open, then we "short-wire" the VCCs
If SW1 it's closed and SW2 it's open, then it's  logic 0 in the MOSFET which will make that nothing goes to USB-F.

Now here are some questions:

Is there any better way to do it?
Do you see any problem with this system?
What happens if SW1 it's open and we close SW2?
Can SW1 and SW2 be those simple switches that only have rating of 20-50mA? I'm a little worried about that because this sources can give up to 2A and I don't know if all of those amps pass through the switches (even if the mosfet requires low power).


texts:
Dear all i have a very simple question on serial data transmission.

signed int NUM;//32 bit
NUM=235;

the serial configuration is:

115200 baud rate
1 start
1 stop
no parity.

How much time will it take to transmit this number(NUM) over the serial port?

furthermore, I send the data in two ways as follows. My IDE is Keil Microvision.
1>  use printf("%d /n", NUM);

2> I have written a function

    void Send_Info(uint32 count1)
{
      int k;
        static uint8 NumPos[6]={0};

    NumPos[0]= count1 / 10000 + 0x30;        //tenthousand1
    NumPos[1]= count1 % 10000 / 1000 + 0x30; //thousand1
    NumPos[2]= count1 % 1000 / 100 + 0x30;   //hundred1
    NumPos[3]= count1 % 100 / 10 + 0x30;     //decimal1
    NumPos[4]= count1 % 10 + 0x30;           //unit1
    NumPos[5]= 0x0D;                         //CR
     for(k = 0; k < 6; k++)
    {
            (void)stdout_putchar(NumPos[k]);
    }
}

All transmission happens inside an interrupt which occurs in every 0.5 sec.


texts: Is there any problem with soldering a charged battery?

texts:
I have a project in mind that amounts to little more than rebuilding a broken eGo-T (electronic cigarette). The battery when I took the busted eGo-T apart had quite a kick and I got a minor burn from it. (It's a lithium ion battery, I think). As I have no way of discharging the battery I was thinking that I would just hook it back up and solder some new wires into it. That strikes me as potentially problematic, not only because I do not fancy another burn but also because I am worried about damaging the PCB.

Edit #1: I am getting 3.8v on the Multimeter so it is definitely still at full charge.

Edit #2: The battery has solder tabs on it so according to the answer to Is soldering wires directly on a NiMh battery safe? I should be okay I think? I'm a total newbie so I could still be wrong.

Aside from the very real risk of heat damage to my fingertips are there any other risks I need to be aware of?


texts: What is reset, preset and clear in a counter circuit?

texts:
I know this is a basic question. But I want to know the use of Reset, Preset and Clear in a Counter circuit.
How do I use them?
An example would be appreciated.


texts: plotting dirac delta function using inverse Fourier transform

texts:
I was trying to plot shifted dirac delta function in Matlab.
$$\begin{align}\mathscr{F}\left(\delta(t-t_0)\right)&=\mathcal{F}(\omega)=e^{-j\omega t_0} \\
e^{-j\omega t_0}&=\cos\omega t_0-j\sin\omega t_0\end{align}$$

Using Trigonometric form of Fourier transform:

$$\begin{align}\mathrm{A}(\omega)-j\mathrm{B}(\omega)&=\cos\omega t_0-j\sin\omega t_0 \\
\delta(t-t_0)&=\frac 1{\pi}\int_0^{\infty}{\cos\omega t_0 \cos\omega t+\sin\omega t_0 \sin\omega t \space \mathrm{d}\omega}\end{align}$$

Let's assume \$t_0=\pi\$.

For more information on trigonometric form of FT: https://imagizer.imageshack.com/img922/8960/Z9xkMw.jpg

Given below is Matlab code and the plot generated using it. Where am I going wrong? Thank you for the help.

clear all; close all; clc;
t=linspace(-5,5,800);

for it=1:800

f=@(w)(1/pi).*(cos(w.*pi).*cos(w.*t(it))+ sin(w.*pi).*sin(w.*t(it)));
F(it)=integral(f,0,3000);

end

figure('Name','inverse Fourier transform');
plot(t,F,'red');
hold on;


texts: Diode package selection in flyback circuit for a relay

texts:
I intend to use the following flyback circuit for my relays (third circuit circled in red):

Here are my relay specs:

1) G6DN - 5 A 250 VAC contact rating

Coil voltage = 5VDC

Coil resistance = 227 ohms

2) T9G series - 30 A 250 VAC contact rating

Coil voltage = 5VDC

Coil resistance = 28 ohms

I intend to use this NPN transistor to drive the relay:

Part number - MMBTA42LT3G

Max Ic = 500 mA

Max Vce = 300 V

I am going to use a 24 V zener with a series diode as shown. PCB has space constraints and hence I would like to use the tiniest packages of diodes which guarantee safety of the circuit. Below are my questions:

1) What should be the minimum reverse breakdown voltage for D2?

My guess is that Anything more than 10 V will do the job because VCC = 5 VDC.

2) What should be the packages of D1 and D2?

I believe package has to do with allowable peak current and power dissipation. More current and power calls for a bigger package. However I am clueless about how to calculate these quantities.


texts: Visible Light Communication LED Turnoff Time Problem

texts: I am doing Project on Wireless Optical Communication(Visible Light Communication). I am using Nicha  NSPW510 DS White LED at transmitter and Vishay BPW34 PIN photodiode at receiver. The problem is with LED TURNOFF TIME. It is about 30 usec s. and i am not able to increase my speed beyond 10 kbps.(distance 1 - 2 meters). Could u please suggest any LED type, which supports upto 1 Mbps. ( I have tried to reduce turnoff time of LED by driving it into reverse bias region, but it did'nt helped me.)


texts:
I need to switch three different supply and for that I am planning to use 3:1 Analog switch something as shown in the below Block diagram.

As we know there will an on resistance(Ron) for these kind of switches. So will this resistance lower down the voltage once it is switched through the analog switches? My understanding was, since this resistance will come in the series of load resistance of IC, so should impact only the flow of current not the voltage.

Is my understanding is correct? If not, could some one please suggest an another way of switching the 3 power supply with two control inputs?

Thanks


texts: What determines the number of bits for the address field in a cache memory?

texts:
I understand a cache memory is constructed for a basic block like this

Valid bit | Address bits | Data/Instruction

But what determines the length of the address bits? I understand that for a 32-bit system the address bits always end with two zeroes and therefore these two zeroes are omitted. Will for 64 bits last 4 digits be zero? Does this depend on size of primary memory? What does the formula look like?


texts: has anyone used the arduino to convert text to speech?


texts: Fundamental period of periodic delta function

texts:
I have the following signal:

$$ x[n] = X\sum_{k=-\infty}^{\infty}
(\delta[n − 4k] + \delta[n − 4k − 1] − \delta[n − 4k − 2] − \delta[n − 4k − 3])$$

The fundamental period of this signal is \$4\$. Is this purely because of the factor in front of \$k\$? Secondly, if I were to sketch the signal for 1 period, would the value for \$x[0] = \delta[0] + \delta[-1] - \delta[-2] - \delta[-3]\$? Or would I have to take into consideration the value of k?


texts: For my project, I am using a 3.3V source to run two motors. If the motors pull more than 1A, then they have to stop. I was told to do this with software and hardware protection. As a programmer, I have no clue how I should go about trying to design this circuit to stop just with the hardware. The suggestion I was given was to "think about shunt resistors".


texts:
After years of programming, I'm trying to do some electronics again.

So I wanted to build an amplifier. I think I now have most of the information, but I'm stuck with the heat sink.

So, basically, I figured out that the calculation goes something like:

temperature increase = power dissipation * total temperature resistance

This particular amplifier IC has the following characteristics (datasheet):

max output power:           40W
Rth (junction-case):        1.8°C/W
max junction temperature:   150°C
max operative ambient temp: 105°C

So, when I have a room temperature that shouldn't go over 30°C, my guess would be that I have 120°C of 'room'. But an average heatsink adds a few temperature resistance units, easily going over the maximum temperature. So I started wondering what the actual power is I need to dissipate.

I am using 4 ohm speakers. I don't intend to drive the volume too high (the speakers themselves are 35W, and while I only have a vague idea of how loud that is it seems much louder than I would ever listen to).

This is a graph from the datasheet.

So I do have multiple questions actually:

Are my assumptions and calculations correct?
What is the maximum temperature I should use for the junction, 150°C or 105°C?
How much warmth does the chip produce? I have trouble interpreting the graph.
And what kind of heat sink would be suitable for that? It appears this is measured in W/°C.

EDIT:

I've decided to go with a different IC, as this one produces a bit too much warmth. Either one that is much lower in power (and has a less confusing datasheet), or with this class D amplifier which doesn't even need a heat sink and is thus much smaller. Thanks for the help and explanation, I think I have a better grasp on calculating heat sinks now.


texts: How can I find the voltage rating for a particular ceramic capacitor?

texts:
I have an old tube radio. There is a ceramic cap with:"RMC / 0.1 / 1400V / Z5U " written from top to bottom, respectively. Now, this cap has broken at it's base and can't be resoldered and so must be replaced. I have another ceramic disk cap, almost the same radius (across the flat aspect) with: " RMC / 0.5 / 20% +- / Z5U " written on it in the same fashion.

I'm wondering what the voltage rating of this possible replacement cap is and whether or not it would make a suitable replacement for the whacked one.
I've been looking ALL OVER the Net for info on ceramics and their voltage ratings when not shown on the cap. I found nothing so any help would be appreciated. I read something that I find highly suspicious so I won't poison the mental pool here with that particular suggestion but I am quite interested in what the EE community has to say.


texts:
In reviewing the following wiring schematics for a vacuum contactor, I can't wrap my head around why things are the way they are.

Source > Downloads > Catalogues

Wiring Diagram #1, Size 4 Contactor

My thought-train for the circuit is:

START is pressed, powers the circuit.
AUX is not powered so it shorts the resistor/capacitor
Coil M receives the fully rectified line voltage.
Sometime later, AUX closes and the resistor/capacitor are in series with the rectifier.

What is the purpose of this resistor and capacitor? Is this just to reduce the voltage on coil M? M would require a specific VA to keep it energized, so wouldn't dropping the voltage simply increase the current required?

Bonus: What would be the purpose of substituting the resistor/capacitor for a resistor and potentiometer in series? Tune the voltage at the rectifier?

Wiring Diagram #2, Size 5 and 6 Starter

This circuit doesn't include the resistor/capacitor pair, but it has two coils in series. This didn't make sense to me so I researched some and found this excerpt:

  The operating coil has a "figure-eight" shape and is really two coils in series, with a connection to their common point. [...] When adjusted correctly, this contact allows a relatively high current through the pickup winding, and as the controller closes, the contact inserts the holding winding, which reduces the coil current to a low value [...]

That makes general sense. One coil for high current draw, one coil for holding current draw. What doesn't quite make sense is, again, how putting them in series reduces the total draw. Don't they each need their required VA? Or, does the holding winding essentially knock-out the pickup winding? I think I might be overthinking it as I rarely see coils in series, always paralleled.

Lastly, with both of these coils being fed off full-bridge rectifiers with no smoothing capacitors, do they ever risk opening as the DC voltage bounces to 0 V?


texts: Questions on interfacing circuit for an NPN input

texts:
I have to use this sinewave outputting sensor with the NPN input of this converter. My previous question was related to the same issue but the question was about a totally different circuit design i.e. a single CE amplifier. Even the circuit was working in practice, from many expert comments I was suggested to make an interface with a comparator instead and use voltage protection.

Input is a sensor which outputs sine waves from 200mVpp to 12Vpp between 1Hz upto 100Hz. The circuit below I aim to convert these sinusoidal inputs to pulses and via comparator's open collector I want to pull down NPN input (Y1) of the F2V converter. Output impedance of Y1 is not given so I measured it with different resistors as around 2k (R1 in the circuit).

In simulation I get the following voltage output at Y1:

It seems this works in simulation for the desired input ranges.

Is my way of driving this sensor to the converter correct? Can this circuit be optimized or improved? Are the locations of TVS and diodes correct? I'm just wondering if there is fundamental error before I start soldering.

edit:

Above is how I'm going to configure the setup. The points A, B, C and D are in question for protection. I was only thinking for the moment MOV or TVS for the point A.

EDIT2:

Corrected comparator circuit:

Suggested self powered transistor circuit:

I apply this noisy signal as an input to both:

With 100mV hysteresis the comparator circuit inputs:

Comparator circuit final output at Y1:

Transistor circuit's final output at Y1:


texts: ID a green ceramic component from a tachometer?

texts:
This component is from a 1960-70 vintage boat tachometer.

It's about 1.25" long.  It generates not a single reading on my 11-function multimeter (including capacitance). I may have fried it removing it from the circuit board.

Thanks for any help.


texts: I would like to use the method of Zigler-Nichols method for open loop. I got the step reponse from Simulink scope but How can I calculate the L and A from the scope?


texts: How to measure the impedance of PCB trace

texts: I am working on some front end electronics design working at 200MHz to 1 GHz for my MS project. I have designed the circuit and PCB. Trace width were calculated by simulations. After I given this to my local fab house, they have provided me a PCB strip about 1 ft in length with some via on each side and trace connecting them. This trace is mentioned to be 50ohm and 100ohm differential. But my guide wants to verify it by myself. My question is how can i practically measure the characteristic impedance of PCB traces, both single and differential pair. What instruments i am going to need and how do i connect them to strip, because i can't add a 50 ohm connector at test points.


texts: Transistor substitution guidelines? (and the BC147A)

texts:
I'm in the US and fixing a vintage German integrated amp which has a crackle static issue I've isolated to a transistor in the preamp section. The transistor is specified in the schematic (below) as a BC147A (datasheet specs) and the actual part in the amp appears to be a BC147B (datasheet specs) These are both vintage European parts, not generally available here and now. (I'm trying to avoid navigating international postage during the pandemic on an NOS part.)

I'm not an electrical engineer and frankly don't know a whole lot about transistors outside their basic use in a circuit, but I'm willing to learn. So I'm trying to take the opportunity to understand what guidelines I should follow when trying to source a replacement transistor for a part that I can't source. (I spend a lot of time trying to fix up old audio stuff so this comes up from time to time.)

The very bottom of this web page offers this handy list:

  Use a device with equal or greater breakdown voltage
  Use a device with equal or greater operating current
  Use a device with equal or greater power dissipation
  Use a device with equal or greater gain bandwidth product
  Use a device with equal or lower switching time
  Use a device with equal or lower trigger current
  Use a device with equal or lower reverse current

I'm trying to understand if this set of guidelines makes sense and how important each of these variables might be (or how to determine given the device how important). I'm a dummy on most of this stuff, so my apologies for looking for something more rote, but I'm happy to learn if anyone wants to point me off somewhere that could help contextualize parts for audio circuits

I had someone advise me that RCA used to do a bunch of "universal" replacement transistors, and that in my case their SK3444 part (datasheet) would be appropriate. It doesn't follow quite all the rules in the list above though, for example the original part seems to have somewhat greater (45V) breakdown voltage collector-to-emitter than the replacement (40V). Not all the above specs seem easily findable for both parts.

Thanks for any insight.


texts: Different 50Ohm-matched condition for different length of metamaterial waveguide

texts:
Based on coplanar waveguide, I am designing a meta-material waveguide by inserting lumped-element inductors along the center line.
Here are some parameters:

Target frequency: 10-20 GHz
Size of lump capacitor: 10 um, sit along
the CPW (insert into a cut along the centerline)
CPW dimension: CL width = 20 um, CL gap = 11.8 um (nominally 50 Ohm TL)

The lumped-element inductors are separated by 20 um. To achieve 50 Ohm matching, between the inductors I inserted a pair of open stub, extending from the center line into the GND without touching. Together with the inductor, I define a unit cell using T-model as "LCL", where L is half the inductance of each inductor from the front and rear of a cell.
A similar figure can be found in Fig. 1 in this work:
https://arxiv.org/pdf/2007.00638.pdf
In COMSOL, I simulated a short array of 20 such cells terminated by 50 Ohm lumped ports, where I swept the stub length as a parameters:
50Ohm_LumpedPort_1 --- (LCL) --- (LCL) --- ... --- (LCL) --- (LCL) --- 50Ohm_LumpedPort_2
With the above 20-cell simulation, I found that I needed a stub length of 100 um (each side) to obtain sufficient shunt capacitance to get good 50 Ohm matching, characterized by a minimum peak reflection over a wide band of freq (8-12 GHz)
Then I expanded the simulation from 20 cells to 200 cells. The models are similar except that now we have a longer chip as the array is straight. I also kept the lumped-element inductor the same. To my surprise, now the stub length that gives 50 Ohm matched condition is significantly shorter at 80 um.
To analyse the issue,
I fitted the 20-cell model in Python to an expected transfer matrix to extract the L and C values of the cell at a given stub length. Using the obtained L and C, I formed a 200-cell array and analyse the Bloch impedance, I do not see a big difference from that of a 20-cell array, and they are both very close to Z_0 = sqrt(L/C) expected from a single cell.
Much appreciated if you can advise on it.


texts: Solving 5 variables Karnaugh map - grouping

texts:
Welcome. I would like to ask about solving Karnaugh Maps, especially grouping 5-variables map. I am not sure if I made this good way, so if you could, please let me know what is wrong. It seems to me everything is fine.

Actually, is there any good Karnaugh map solver which work with 5 variables as well?

Here is map:


texts: How to make two independent voltage source from single 12V 2Amps power supply

texts:
Well, I am cranking my head around this one. I have a 5V microcontroller (AtTiny2313a-pu) which drives a 12V(max) DC motor(ampere rating unknown).
I have programmed my uC correctly and caused the motor to "blink" for one second then turn off for one second and so on(not resorting to PWM). I tested using this using this schematic and it works. (I am using a TIP120 npn transistor)

Instead of using two batteries/ supplies, I tried to use the same battery for powering my microcontroller and Load and I am getting very strange behavior. I set the blink time to 2sec but here with this schematic(below), I observe random switching.

I have read about a phenomenon called ground bounce from the noise generated by motor that is temporarily resetting my microcontroller.
I followed the instruction from a similar post that appeared in the forum and I tried to connect the battery ground to collector first then to my microcontroller and its regulator as mentioned in the answer but I observe the same strange behavior of resetting. How would I get rid of this behavior?
Also, I have a 12V 2amps adapter and I want to power my project through this. Is there a way to split 12V into 5V(for microcontroller) and 9V for Motor as an independent power source as described in schematic 1?
I read that linear voltage regulators are very bad for powering motors,Will buck converter serve my purpose?
PS: I am very new to electronics please don't vote me down. In case I miss something I will modify in the post and abide by the standards of this forum.
Thanks you


texts: Why can't we use diodes in place of batteries?

texts:
1.why we cant use diodes in place of battery?we are getting 1.4v in a cheaper cost than battery.but why we dont use?

2.if electrons are moving in a single direction it releases many energies but why we are calling it as "current"?

Probably can be put as follows. Opriiginal poster may wish to check this wording:

Why can diodes not be used instead of batteries as a source of energy. Bothe batteries and diodes have current flow in one direction and diodes have potential voltages of up to 1.4V and are cheaper than batteries - so they seem like  better choice.
Electron flow in a single direction provides a source of energy.
Why do we call this energy flow "current"?


texts: Why are evaluation/development boards banned from being used in products?

texts:
Typically they say stuff like...

  ... shall not be directly or indirectly assembled as a part or
  subassembly in any finished product.

I have found on a number of occasions it would have been very convenient just to include one in a small run product


texts:
I am designing a circuit with a DC motor 12V DC Reversible Gearhead Motors - 70RPM  and some other stuff including a MCU and a LASER, all driven from a single 12V source and am concerned about big HF noise ripple from the motor (electrical rather than radiative but no harm in reducing both).

I haven't worked much with motors much before, however from reading the articles in this community and some searching elsewhere on the internet, it seems there are a few techniques for dealing with this noise and I was wondering if I could get some educated response on the validity and drawbacks of a few of the techniques that I have encountered.

Small capacitors (1 or 10nF) connected across the terminals in a variety of combinations including between Vcc/Gnd, two between Vcc/Gnd with the middle connected to the case exterior, and a combination of the above two. Non-polarised if the motor needs to run both ways.
Directly grounding the case of the motor.
Choke inductor in series with the Vcc of the motor.
Employing a more complex filtering topology close to the motor.
Twisting and shielding the cables of the motor and physically isolating them from the remainder of the circuit.
Keeping the ground of the motor separate from the ground of the remainder of the circuit and connecting it directly to the terminals of the power source if possible (or as close as possible if not) to avoid ground loop problems (star grounding?)
Enclosing the motor physically inside a metal case (and grounding that case).
Using large (1000uF+), low ESR electrolytic capacitors connected as close as possible to other sensitive equipment between their Vcc and Gnd (Anode to Vcc, Cathode to Gnd), or placing these large capacitors next to the power source itself on all of the lines leading out.
Running some of the other equipment through a linear regulator (Not sure if these are particularly good at rejecting HF noise)
Placing diodes next to the power source for different lines leading to different systems.

Looking for a generic answer regarding the effectiveness of the above techniques and perhaps more regarding protection from DC motor noise, not something specific to that motor as that project is actually over, now I am just curious and think it would be useful to have this information available in one spot for future projects and other interested people.


texts: Which chemicals can be used to clean electronics?

texts:
I have access to these

isopropyl alcohol
ethyl alcohol
vodka
rum
acetone

And would like to know which ones should be used to clean electronics, and (out of curiosity) why some are worse choices than others?


texts:
Good day,

A simple question to improve my understanding of multiple voltage sources. If I have two potentiometers with the wipers connected both to one input on a lm339 comparator, each voltage source being 2.5, will the input see 2.5v or 5v? Likewise, if one was increased to 5v and the other the same at 2.5v, would it read 5v, 7.5v or an avg? Any explanation would be appreciated.


texts:
I need to make a circuit with 2 leds, 1 green 1 red.

If the current flows, green led will light up, if there is a break in the circuit (open circuit) it will light up another led as red. I don't know how to add the red led and make it light up when both switches in parallel are off. I have no clue how to do this without using a 3rd switch that says close if both switches are open. Help? I've heard of mosfets and spdt but I don't understand them. If someone could draw a beginner schematic it would be great.


texts: Function of Glass bead on EMI Filter Legs

texts:
I am looking at a PCB that has tiny glass beads on the input and output legs of an EMI filter. The middle pin goes to GND.

What is the purpose of the glass beads?

Couldn't get the focus quite right but here is a picture.


texts:
For a project, I need to create a large display (most likely an LED matrix) that can be controlled via Arduino. Large means probably somewhere in the neighborhood of 3' by 10". I intend to use an Arduino R3 to control the display, and it will either have a bluetooth or RF receiver module installed on it, but otherwise empty. The Arduino (and presumably the display) will be powered from a nearby wall outlet (120V). What options do I have in terms of displays to keep the cost as low as possible. (I have several people pitching in money, but I still don't want it to be too high.) From what I have seen, a large LED matrix is not only hard to find, but also very expensive. Can I just somehow link together several smaller LED matrices, or is there some other option? I have no problem doing some programming to accommodate a strange setup if it is cheaper.

Edit:
The only density requirement is for it to be high enough that 1-2 lines of text filling the display is legible at a distance of about 3-6 ft. (This display will be mounted along the side of a hallway.)


texts: Why do positive terminals on DC devices exposed to water corrode more than negative terminals?

texts:
I'm a glaciologist working in Patagonia where everything is always wet. Often water makes its way into instruments, radios and other devices and I feel that always the positive terminals of batteries (and the circuitry connected to it) corrodes more effectively than the negative side.
After not finding a explanation for this, I thought it might only be my impression. But then I searched for some batteries and instruments that spent some time underwater and indeed the positive terminals are corroded and the negative ones are like new. The example below show some Li-Ion batteries that display that situation (of course the picture shows two batteries, but believe me that positive/negative terminals in both batteries looks pretty much the same).
I'm considering this question because I'm now designing an instrument that uses MOSFETs as switches for peripherals, and I'm struggling to find P-Channel MOSFETs to switch the positive side. As N-Channel MOSFETs are much more common and cheaper.
So, does really the positive side corrodes more? If so, why? Can that be avoided somehow if I decide to switch the negative side?
NOTE: One line of thought that I've explored is that the battery will produce water electrolysis. Although, my chemistry knowledge is very limited, I think in that case the highly reactive acid H+ (that I think is how hydrogen stays in aqueous solution) should go to the negative side, so I would expect corrosion there. The negative side gets O2, which could be the reason of the oxidation of the positive terminal, but as there is plenty of dissolved O2 in water and even more in air, I would still think that the negative side should get the worse corrosion, so this doesn't makes much sense to me either.


texts: Using a toggle switch to act as push button

texts:
Basically I want to use a toggle switch to turn on my computer. I need some sort of circuit so that the toggle switch will act like a push button. IE, I turn on the toggle switch but it only sends a pulse rather than keep the circuit open.

Thanks in advanced.


texts: Laptop charger leaks AC while giving DC voltage at the same time. How?

texts: So, I got some laptop charger from my neighbor and I was thinking about to do something with it. Then one day I feel tiny shock from the output of the charger. I thought ac to dc filtering mechanism maybe shorted. Then I had tested other remaining charger to see if there was any AC current going on. And they all do the same. Is it normal to have flow some AC through DC ? Can I do something about it ? make it safer for work ? It does not feel like comfortable.


texts: Confusion between average and rms calculation for power

texts:
I have a DC source where DC Voltage = Vdd and the current supplied by this source is rectified sine wave to a circuit.

Now I would like to find the average power delivered by DC source. There are two ways of doing it
$$
P_\mathrm{avg1} = \frac{1}{T} \int_{0}^{T} v(t) i(t) \, \mathrm{d}t
$$
$$
P_\mathrm{avg2} = V_\mathrm{rms}\times I_\mathrm{rms} = \sqrt{\frac{1}{T} \int_{0}^{T} v^2(t) \, \mathrm{d}t} \times \sqrt{\frac{1}{T} \int_{0}^{T} i^2(t) \, \mathrm{d}t}
$$

Where 'T' is one complete period of \$ I(t) = I_p sin(t) \$ and \$ V(t) = vdd \$
Now the average power delivered in both cases will be \$ P_{avg1} = vdd \times \frac{I_p} {T/2} \$ and in the second case \$ P_{avg2} = vdd \times \frac{I_p} {2}    \$

Which one is correct and why?

According to me the average way is correct, because the average of instantaneous voltage times current should give you the average power. But then I cannot understand why RMS way is wrong! There is plenty of literature on RMS and average power but they generally deal with either sinusoidal or square waves voltages and currents.


texts: Is it possible to generate internal reset pulse in verilog with machxo3lf fpga?

texts:
I have a board without Reset input for my design. But I need to reset at fpga startup.
Is there a verilog solution to generate this pulse ?


texts: Connecting Can Bus Debugger with Arduino Uno

texts:
I'm currently trying to interface USB Peak Can with Spark fun can bus shield.
So I'm trying to test sending data from the Shield to the USB Peak Can bus, but nothing is sent at all, the same for receiving.
Here is the pin diagram for Peak USB Can
Pin assignment D-Sub
Pin Pin assignment
1   Not connected / optional +5V
2   CAN-L
3   GND
4   Not connected
5   Not connected
6   GND
7   CAN-H
8   Not connected
9   Not connected / optional +5V

CAN-L, CAN-H are connected to the shield CANL, CANH, plus the ground common.
I'm not sure If I should add a terminal resistor, but if it's necessary, how would I connect, can I have a schematic diagram please ?


texts: I have a 60V battery bank with 16 Li-ion cells in series. I was wondering if I could get 12V output by connecting a wire across 3 or 4 cells in series and using it to control the 12V dc fan of the battery box.


texts:
I'm designing a new PCB in which
I'm powering a resistive wire via a MosFet, driven by a microcontroller kind of that way:

Vdd: +5V several Amps (depending on the heating wire)

Vin: 3.3V, an output of the microcontroller

I would like to be able to simply test if the resistive wire is present or not before Vdd is turned on.
without Vdd on, I can't use a sense resistor in series with my load to sense the current so I don't know what to do.

There is probably a simple circuit or an IC capable to detect that and send the info to the microcontroller but I can't find it.

also, I only have one input pin left on my microcontroller which also complicate things.


texts:
Is the system \$y(t) = x(t-2) + x(2-t)\$ time invariant?
Here is my solution:
Let \$x_1(t)\$ be an arbitrary input, then the corresponding output is:
\$y_1(t) = x_1(t-2) + x_1(2-t)\$
Let \$x_2(t) = x_1(t-t_0)\$, then the corresponding output is:
\$
\begin{align}
y_2(t) ={} & x_2(t-2) + x_2(2-t) \\
={} & x_1(t-t_0-2) + x_2(2-t+t_0) \\
={} & y_1(t-t_0)
\end{align}
\$
Since \$y_2(t) = y_1(t-t_0)\$ the system is time invariant. Is this solution correct? Because the manuel solution of my book (signals and systems by Oppenhiem) says that this system is time variant.


texts: LED driver circuit interfering with 555 timer?

texts:
Below is a circuit I put together that uses a 555 timer and an LED Driver:

But the strange thing I see is that the timer does not follow the 1.1*R*C equation. The led remains lit for much longer.

I tested this circuit by removing the MOSFET and triggering pin 2 manually. I get the same effect. When I completely remove the LED driver and replace it with just a resistor and LED, it works. I also replaced the 100uF with a 10uF and I see the same problem.

Is the inductor affecting the timer? Is it not a good idea to use such a boost converter + driver to light the LED? Should I replace this circuit with say a 2 transistor constant current source circuit?

I have independently tested the LED driver and it works very well - even with a 1.5 V battery. For the given circuit, I am using a 9V battery.


texts:
I'm building a small class D amplifier: some op amp circuits for pre-amplification, a pwm modulator based on a dsPIC, some power buffers for controlling the gates of an h-bridge power stage, and a LC output filter.

To power the system I bought a cheap (7€) power supply 12V, 5A. A photo below to give the idea of the device:

I tested it and it seems quite strong: while increasing the current flow the voltage always remained at a fixed value.

The problem is that every 15us there is a very high frequency oscillation (~1MHz, ~2V amplitude) on the output. Images below:

To reduce the output of these pulses i tried:

An additional LC filter (L=200uH, C=30uF tantalum) on the output. The ripple still remains and I don't know why.
A 12v standard zener regulator. The ripple still remains (maybe because the frequency is too high for a zener diode???)

What else do you recommend to do?

Thanks


texts: How do you determine the effective resistance of a finite grid of resistors?

texts:
Disclaimer: I am a geophysicist with limited electrical engineering background. I am not sure if this problem is incredibly easy, incredibly complex, or completely nonsensical.

My goal: Determine the bulk resistivity of a rock sample using resistor networks.

The rock sample is to be modelled using a resistor network with certain resistors having high resistance(representing solid rock) and others resistors having low resistance (representing fluid pathways in the rock).

Suppose I have a network of resistors on a uniform grid as shown below. In the example shown, each line segment has an associated resistor labelled 1 through 24 on a 3-by-3 grid. The resistances of each line segment are known.

The total length of the grid is \$L\$ and the "area" is \$A\$ (in this case it is a 2-D example, so the area is also just a length). The bulk resistivity of the sample is then given by:

$$\rho_{bulk} = \frac{R_{eff}A}{L}$$

My question: How do I determine the effective resistance, \$R_{eff}\$ of the network?

I have looked online but all I can find are discussions about infinite networks, source and sink currents etc. I am not interested in the current or voltage.

Can this problem be solved as it stands?