texts: How to charge a capacitor with static electricity?

texts:
I want to charge a capacitor using static electricity generated by me (walking on carpet etc.) and try power a small LED or if that doesn’t work a reading on the voltmeter would be fine (it’s for a science project). I know the total power output would be low though. I was planning to have a metal plate on a wristband and the capacitor connected to this and then to ground, this I think should charge the capcitor from what I understand. Would this work?

EDIT
Here’s a diagram/sketch of my current circuit

The capacitors are 10uF 63V.
The diodes are 1A 200V.
Currently there’s a voltmeter but I would like to have a neon light. I have a 90V and 80V neon light which could be used.


texts: Using a power transistor upstream of a load (control VCC to a load with a lower control voltage)

texts:
So I have an interesting challenge. I have an LCD screen from a laptop which I am driving with a control board. The problem is the backlight needs around 19 volts to run while the control board I have is designed for LCD panels with a 5 volt backlight. Everything else runs fine, just not the backlight. I have a 19 volt power supply that I intend to run everything off of (the 5v control board will be powered of a buck converter from this 19v source). The problem is, when the control board is off or in power saving mode, it is supposed to cut power to the backlight, but since I am driving it directly off the 19v power supply, it stays on. To solve this problem I acquired myself a TIP31AG power transistor from the local radio shack (yes they do still exists) assuming that it could be used like a relay, or atleast in the same situations. As you can imagine this turned out not to be the case.

The Problem:

I have a 19v load of an unkown and probably variable current draw and resistance (it has a separate PWM brightness control which probably varies things).
I have a 5v control wire which can provide a decent amount of current (greater than logic level that is)
I need to control the VCC into the load (not the ground connection, due to the way the control board works)
I have a TIP31AG power transistor, and all the tutorials I have looked at have their TIP31 (which is NPN btw) downstream of the load (that is between the load and ground)

Can this be done with my TIP31 or do I need a TIP32 (the PNP variant) and another PNP control diode to control the load on the VCC side?

simulate this circuit – Schematic created using CircuitLab


texts: What is comparison of readout times of global and rolling shutter cameras?

texts: Rolling shutter will take more time because of sequential readout and global will take less time.But what are the exact values of image readout time?


texts: Using capacitive coupling to implement pulse transition

texts: I was reading about master-slave flip flops, used to implement edge triggering and I read that instead of using master slave configurations, using RC coupling to clock inputs could also enable pulse transition. How is this possible?


texts: VHDL to RTL/schematic, not what I expect to see

texts:
I'm teaching myself VHDL (using Altera Quartus Prime Web Edition) so we can incoroprate a CPLD into a design. I've only been doing it a few days but so far the VHDL itself seems reasonably straightforward. I've learnt how to design entities and use multiple instances of them within a design as components, knit together different components within the VHDL and am pleased with my progress. In fact the hardest thing so far seems to be the simluaton/test bench stuff!

I thought it would be good to see if you could view your VHDL as a schematic to see whether what I have been writing looks like it should. So I Googled around and found references to an RTL viewer and worked out how to use it with some good Altera documentation. At first I thought it looked perfect. The high level view seemed spot on: the internal buses are connected to each component correctly, clock and clr go into the 4 bit registers, inputs go into a multiplxer and come out of the other side etc, exactly how you'd expect it look.

However, when you click on the plus sign to open up a particular component (I hope that is the right terminology using component as an instance of an entity), it looks nothing like how I'd expect.

The following code, for example:

library ieee;
use ieee.std_logic_1164.all;

-- Four bit eight way multiplexer. The eight four bit latches are fed into this and one of them is
-- selected depedning on the select line. This select line will automatically cycle through
-- and also control the eight column outputs.
entity four_bit_eight_way_multiplex is
    port
        (
        sel : in std_logic_vector(2 downto 0);
        IN1: in std_logic_vector(3 downto 0);
        IN2: in std_logic_vector(3 downto 0);
        IN3: in std_logic_vector(3 downto 0);
        IN4: in std_logic_vector(3 downto 0);
        IN5: in std_logic_vector(3 downto 0);
        IN6: in std_logic_vector(3 downto 0);
        IN7: in std_logic_vector(3 downto 0);
        IN8: in std_logic_vector(3 downto 0);
        O: out std_logic_vector(3 downto 0)
        );

end four_bit_eight_way_multiplex;

architecture behaviour of four_bit_eight_way_multiplex is
begin
    mult_process : process (sel,IN1,IN2,IN3,IN4,IN5,IN6,IN7,IN8)
        begin
        case sel is
        when "000" => O <= IN1; -- sel = 0, number 1
        when "001" => O <= IN2; -- 1
        when "010" => O <= IN3;
        when "011" => O <= IN4;
        when "100" => O <= IN5; -- sel = 0, number 1
        when "101" => O <= IN6; -- 1
        when "110" => O <= IN7;
        when "111" => O <= IN8;
        when others => O <= IN1; -- Can never get here of course
        end case;
    end process mult_process;
end behaviour;

Gives the following RTL diagram:

This does not look like a four bit, eight way multiplexer. Well to me it doesn't. I even took a one bit, eight way multiplexer off a tutorial site and it gave a similar looking RTL schematic.

I would have expected something of this style. Please note, style, I realise this is a one bit, four way device.

So, can I not do what I thought I could? Is it possible, but in a completely different way? Should I be forgetting about doing this and just enusring the device works with good simulation?

I've also tried technology map viewers, but they don't seem right either.

I repeat, I've been doing this for just a few days and fully appreciate I might have some major misunderstandings here. Many thanks.


texts: How to read hexadecimal data from text file and write in into memory in verilog?

texts:
I have a text file named "Hex_data.txt". I want to load content of Hex_data.txt into a variable name RAM in verilog. When I try this, I get an error that the text file can't be found. Where is this file loaded from?

The content of "hex_data.txt" :

21
a4
2a
26
7a
ff
6f

I want to create a variable name "RAM" defined like:

reg [6:0] RAM; in which the above content save like:

RAM[0]=21
RAM[1]=a4
RAM[2]=2a
RAM[3]=26
RAM[4]=7a
RAM[5]=ff
RAM[6]=6f

I wrote a code:

module file_read;
  reg [7:0] RAM [0:6];
  initial $readmemh("Hex_data.txt", RAM);
  integer i;
  initial begin
    $display("data:");
    for (i=0; i < 7; i=i+1)
      $display("%d:%h",i,RAM[i]);
  end
endmodule

But the above code not working. How can i get desired output?


texts: ADC bandwidth in excess of filter bandwidth

texts: I am using a BPF of 5 to 300kHz on a pulsed input signal. Is there any benefit to digitizing at a rate significantly in excess of nyquist?


texts: I2C baud rates and delay calc(bit banging)

texts:
The microcontroller which I am using doesnot support I2C hardware. So,I am trying to implement I2C in the module using GPIO ports. The microcontroller communicates with EEPROM, and the EEPROM has SDA and SCL pins.The EEPROM chip has a baud rate of max 400Kbps(according to its datasheet). I am aware of I2C protocols and know how to implement (Start, write, read, stop), but I am unable to determine the baud rate at which the controller needs to communicate with the EEPROM. Since the controller doesnt supports the I2C hardware, how and where can I set the baud rate (No baud generator formula). I am also finding hard to calculate the I2C delay time, when I set the pin from High to Low or Low to High(it may take some time when pins are made high to low or vice versa). Could someone please explain in general, what is the proper way to detrmine I2c baud and delaytime. The EEPROM chip has maximum baud rate upto 400Kbps. The control runs at maximum clock speed of 40MHz .

Your help is highly appreciated

Thanks


texts: Can i output a certain memory area of a processor with objcopy?

texts:
For a bootloader (PIC32) i do need only a certain memory area from a binary file (application for a bootloader, config and bootloader are located elsewhere, no hex possible). If i call the xc32-objcpy on a hex or elf file it will create a 44MB binary of the whole address space.

What i need is only a certain memory area (kesg0_program_mem) where the application is located. Of course i could create the 44MB binary and then cutout a certain address range, but is there no option to directly output the area of interest? The program mempory is stricly defined:

kseg0_program_mem     (rx)  : ORIGIN = 0x9FC01000, LENGTH = 0xFF00-0x1000

I tried getting only the sections from the Linker file but that is tedious even with wildcards (see below, incomplete).

-I ihex -O binary -j .text -j .data -j .rodata -j .reset -j .bev_excpt -j simple_tlb_refil -j .cache_err_excpt -j app_excpt -j .vectors Test.X.production.hex Test.X.production.bin

I am open to any but it would be helpful if it can be done by the command line


texts: Value of the capacitor required for smoothing

texts:
I have been checking outputs for my energy harvesting device. I connected the schottky bridge rectifier for full wave rectification and then connected 2200 uF and 3300 uF capacitors for smoothing of the voltage.

simulate this circuit – Schematic created using CircuitLab

The direct output voltage from the motor is as follows:

When I connect them to Schottky diodes and C3 (2200 uF), It gives this reading with V_max at around 12 v:

When I connect to Schottky diodes and C1 (3300 uF), It gives this reading after smoothening with V_max at around 10 v:

How is this possible and how do I get the right smoothing capacitor for my required output voltage waveform? In this case, 2200 uF capacitor works better than the 3300 uF. I tried calculating using the formula, but I am not able to ballpark it to the estimated 2200 uF value:

$$q = I.t$$
$$C. \Delta V = I.t $$
$$ C = \frac{I.t}{\Delta v}$$


texts: Simple way to turn on/off 230V line power by a simple PC?

texts:
Reopen reviewers: the question didn't ask for a specific product, the question asked for, how to do it. A specific product name may or may not inserted into an upvoted/accepted answer. I had never asked a spam seed intentionally, please don't misinterpret the essential part of the question.

What I can:

A home PC with a linux, and I can program it on need.
I can buy cheap chinese things from ebay.
I can solder and do basic electronic tasks.

What I can't: I won't create printed circuits for a such simple task.

What I want to reach: I want a solution (probably some hw+sw combo), which enabled me to turn on/off the 230V line power of another device by a PC.

I prefered a wired solution against wireless because of stability, but wireless can be also ok.

What to do?


texts: atmega328p is not detecting on USBasp programmer after verify 0 error?

texts:
I was trying to burn my atmega328p board which is designed for some wireless application. The ICs atmega328p, esp8266 12f, and ADM7171 are using the same Vcc. Here the Power supply is connected to LT3682 and the output of the same is shared by the above said ICs.

I have used ProgISP tool and USBasp programmer. The board that I have used was already programmed by another person. So the fuses are already set.

After connecting and verifying the connections. I clicked RD button on progisp and output was ok. so the atmega328p is detected and thereafter I verified the fuses and it was ok. Then burn the flash with my hex code, but at this time it gives me a verify 0 error.

After getting that error, Atmega328p is not detecting on USBasp programmer. I have also changed the tool to avrdudess but it have the same problem.

The one problem that I was observed is that, while writing the flash USBasp programmer was at 5V. Is that any problem?
After noticing this, I have changed that to 3.3v and again tried to burn the flash but the same happened atmega328p is not detecting.

Is that any fuse locks? But I haven't done anything to fuse bits, I have just read that. I have also double-checked the connections and the programmer is good since I can burn the flash of the other board.

For programmer at 3.3v, I observed following voltages.

Vcc - fluctuating 2.23-2.31
RST - 2.22

These voltages are not constant, sometimes it varies.


texts: What is the operating frequency of this IC?

texts:
It is the LT3751 High Voltage Capacitor Charge Controller, datasheet.

I am trying to calculate the required value for the input capacitor for my application, but the datasheet does not clearly specify a frequency.

The best clue I can find is the "One Shot Clock Period" in page 3, which at 44us results in 23kHz - but I am not entirely convinced.


texts: Do metal enclosures block radiated emissions better than plastic ones?

texts:
Why are some enclosures made of metal instead of a lighter insulated material?

Is there any electrical reason for that?

Will such enclosure block radiated EMI in and out better than a plastic one?


texts:
I am working on a temperature measuring circuit using a pt100. The input of my instrumentation amplifier (AD8226) is between 80-200mV. The Gain is set to 20.84 so I get an output range of 1.7-4.2V. I want to shift down those voltages to 0-2.5V for my ADC.

I only have a precise 2.5V Voltage reference. Whats the best way to get -1.7V for the reference pin or is there a different way to shift the levels down so I can use the entire ADC voltage range?


texts: Precision and manufacturing of resistors

texts: I am trying to understand why there is variations in resistance values, in other words, why there is difference in the value of the resistance between color code and the measured resistance. Also, how to manufacture more precise resistors?


texts:
I've been fiddling with a twin-T percussion oscillator with success. It's built on a breadboard and it sounds exactly how it should sound (damped sine wave, big 808/909-kind of kicks). However it's noisy. I've tried adding a big electrolytic cap between V+ and GND. It makes difference yet it's still very noisy. Also, the circuit tends to 'buzz' when I touch the pots or a wire. Any idea how to kill that? The whole circuit is powered from a split power supply from a switchable adaptor (I mean the op amp, the rest of the circuit is powered from 0-9V).

Simulatable schematics of the circuit here (Open in Editor-> Menu->Run Last Simulation):

simulate this circuit – Schematic created using CircuitLab

This is the power supply used:


texts:
I need a simple circuit to protect my device from overvoltage (more than 13V). Typical working DC input voltage is 7-12V. Can I use this circuit:

Will it work?

UPD. OK, it will not. I was too stupid. Yet another try:

(Sorry, I forget to change default names. My MOSFET is IRLML6402, transistors is BC817, zener 13V.)

When input < 13V, Q2 closed, Q5 open, MOSFET open. Else Q2 open, Q5 close, MOSFET close. OK?


texts: H-Bridge Low Side Sense Resistor - Position of Resistor and Bulk Capacitance

texts:
My question regards the considerations required in determining the location of a current sense resistor on the low-side of an H-Bridge. I've presented two scenarios.

Details: The H-Bridge load is a fly-back transformer driving a high voltage piezoelectric transducer with random frequencies between 20 kHz to 80 kHz. The transducer is driven on 50% duty cycle of 100 ms of pulsed signal then off for 100 ms. The transducer presents a wide range of impedance and harmonic resonance characteristics that are determined by the frequency it's being driven. Much of the band between 20 kHz and 80 kHz presents high impedance and the current drawn can be as little as 0.5 A. At self resonance it can be as much as much as 10 A.

Bulk capacitance is 2000 uF.

VDD is 12-14 V.

Sense resistor is 0.15 ohm (Current throttling will kick in at 3 A creating a voltage differential above ground of 0.5 V)

The first scenario would be what I would rather do. It locates the current sense resistor after the termination of bulk capacitance. This would essentially isolate the H-bridge from the rest of the circuit and allow inductive currents to circulate back to the bulk capacitor bypassing the sense resistor. This method would provide a less noisy and more normalized current reading. It would also create up to a 0.5 V difference between the H-bridge and ground. I'm unsure of how this would affect catch diode placement and the gate driver ICs. Also, the gate drivers would be connected to true ground as well as the common nodes of the bridge and at times present a -0.5 V ground path. Unless the driver ground be placed into the same node above the sense resistor, but I'd then run into the same problem with the ground path of the micro-controller supplying the signal input to the gate drivers. Is this scenario feasible?

The second scenario has the bulk capacitance outside the sense resistor. Bulk capacitance would have to circulate back through the sense resistor. This option would provide a more "real-time" current reading, but would be extremely noisy and produce higher currents through the resistor. Also, the circuit is liable to present transient voltage spikes through the sense resistor that would make it difficult to determine actual current draw.

Are there other options for low side current resistor placement?


texts: Why is 1000Base-T RJ-45 pinout scrambled instead of having each diff. pair in sequence ?

texts: I need to make an ethernet connection using a cable about 6 feet long to a small and low power gigE camera.  Other signals are required (power to camera and hard trigger) and one cable is better than two for practical reasons, so I'm not going to use an RJ-45, and plan on using a multipin circular Hirose (uncharted territories here).  I noticed however that in the RJ45 one of the pairs is 'inside' another pair in the pinout, but I would have imagined that each pair would simply be next to each other.  I don't know why this is not the case, and if the reason behind this may help me in choosing the right pinout for the circular Hirose.


texts: What is the purpose of two cylindrical holders in RJ45 female connector for PCB

texts:
I am a beginner in PCB design. While using sensors for my project I thought it would be a great idea to connect my sensors using RJ-45 connector and in my device, I'm thinking of using a RJ-45 female connector for PCB. The female connector looks like this:

To make the female connector firmly attached to the PCB board, the 8 pins are soldered to the PCB board. But, besides it, I don't know the use of these cylindrical holders. How to use it?


texts:
Have you ever encountered an SD card which does not support the SPI mode?

I know microSD are not required to but I believe all do support SPI.

EDIT: The information about optionality of SPI seems to come from Wikipedia and was recently removed (here and here).


texts: Current measurement opamp, is this circuit flawed? Output all over the place

texts:
This is a circuit to measure a current flow that is 0-10A DC. The output goes to an ADC.

The circuit itself works fine, however, over a dozen cards, the output of this circuit is all over the place.

At rest, I=0, the output offset can vary by a factor 10 (300 to 3'000 count on the ADC) from one board to another; but is stable in a specific board.

So far, it might be related to the input offset voltage, given at 0.11mV typ. but this would account for perhaps 10%.

The manufacturing of the cards was also poor and noticed some pads seem not well soldered, I wonder if that could be a cause as well.

Are there other fundamental flaws in this circuit?

I need to fix an existing batch of boards.

VDD: 3.3V
ADC is 0-3V with 0.1% reference. the ADC is not saturating.
ADC is 12bits, 16 measurements summed: 16*12bits = 65535 counts.

Two random cards measured at rest I = 0A voltage at the circuit output:

A: 150mV / 3445 count
B: 34mV / 336 count


texts: How to modify BRR and BRSS registers to stm32f4 from stm32f103

texts:
I'm trying to modify stm32f103 2x16 lcd library to stm32f4. There are BRR and BSRR register on stm32f103 but there aren't similar register in GPIO_TypeDef structure on stm32f4 so i don't know how to modify these codes.

LCD16X2_GPIO_D5->BSRR = LCD16X2_PIN_D5;

LCD16X2_GPIO_D4->BRR = LCD16X2_PIN_D4;


texts: Single I2S Source for Two Speaker Amplifier

texts:
I have two same speaker amplifier which is TAS5720 series from TI.
I drawn two identical schematics for these ICs which driven by one I2S source.
In practise, one of them is playing sound bad. Both of two has correct duty cycle at output stage and one of them is modulating depending on digital sound data but the broken one could not modulate. If I only initialize the broken one by software. It plays sound well.

This is my schematic.


texts: I'm going to buy a PoE injector kit, and I will supply it with an AC voltage, and with ethernet cable, and at the other end I will design a seperator circuit, but however most PoE injectors just give 40DC, with at most 400mA. I would like to get more amperage at the backend, is it a must to have a battery or any other supplier and put some transistors to get more current ?


texts: Is the field distortion due to armature reaction constant in a series motor?

texts:
In a series motor the current in the field and armature windings are always equal.
I'd expect that to mean that their respective fluxes always keep the same proportion.
So, if this is true, does the MNA keep the same angle relative to GNA in a series motor, irrespective to load?
The currents induced in the iron core of the armature (and the flux generated by them) don't follow this, but once the core is laminated this should be minimal, right?


texts: What are these rectangular sidebands on my local FM radio station?

texts:
I recently bought an inexpensive USB software-defined radio dongle, and have been poking around my local spectrum:

The above image is one of the local FM radio stations (88.7 Mhz, to be specific). I am wondering what the large, rectangular side-bands are. They don't seem to be involved in the actual radio content, as this is the only station that has them, and all the other stations seem to be received fine.

It's also not the stereo component of the signal, as again, stereo demodulation for other stations that lack these sidebands works without issue.

Each sideband is 125 Khz out from the center of the signal (i.e. the inner edges of the rectangular sidebands are 250 Khz apart).


texts: Is better to have holes on different sides of the shield instead of the same side?

texts:
I suppose the best is to have no hole on the shield, but that is practially impossible if you have to let cables come out of it.

So I read somewhere that having the holes on different sides of the shield (assuming that a shield is like a box around some electrical equipment, like a chassis around PC hardware) is better as opposed to having them on the same side.

If we have a box shield, with 6 sides, drilling 3 holes on 3 different sides is better than drilling 3 holes on the say upper side?


texts: Can you short two output pins of a decoder (74LS154N)

texts:
Let's say for two inputs, the output values will be the same. So instead of using an AND gate, I was wondering if i can just short them. Please check the attached logisim screenshot to get a better idea of what I'm trying to do.

The 7-seg display will show "1" when the input is 0101 or 0111. Can I just short the two pins in the real decoder, like I've done in logisim? Or would it mess up the thing?


texts:
The Junction-to-case (bottom) thermal resistance of the TPS7A4701 LDO regulator is 1.7 °C/W. It is explained in the TI's app note "Semiconductor and IC package thermal metrics" that this metric refers to the thermal resistance between the junction and the exposed pad of the package.

On the other hand, the Junction-to-board thermal resistance of the regulator is 11.9 °C/W. I am not sure that I understand this metric. If the junction to the bottom case (exposed pad) is only 1.7 °C/W, and the junction to board is 11.9 °C/W, so there is a 10.2 °C/W thermal resistance between the exposed pad and the board. But the exposed pad is soldered to the board, so it doesn't make sense, the thermal resistance of the solder should be very low.


texts:
I'm developing a LoRa solution that I want to check is compliant with radio spectrum laws in Australia. The radio will transmit at 915Mhz at 22dBm (158mW) with a channel bandwidth of 500Khz, and won't be setup for channel hopping.

The legislation says (for digital modulation transmitters as its not channel hopping):

915–928 1 W The radiated peak power spectral density in any 3 kHz must not exceed
25 mW per 3 kHz

My interpretation of this is that as the 22dBm power is spread across 500Khz, then looking at the power in a 3K slice will have a much smaller proportion of the total power (3/500) assuming the power distribution is linear across the bandwidth. Even if the power distribution isn't linear I should be well within the legislated limits.

Am I reading this right?


texts: NiMH discharge protection and MCU powering

texts:
I would like to power an ESP32 devkit board with four NiMH AA batteries.
The ESP32 board has an AMS1117 voltage regulator. It has a dropout voltage of 1V.
The output voltage is 3.3 Volts so my understanding is that the minimum supply voltage is 4.3 Volts.
For 4 NiMH AA battries:

Full: 4 x 1.4 = 5.6 Volts
Nominal: 4 x 1.2 = 4.8 Volts
Empty: 4 x 0.9 = 3.6 Volts

This means that the voltage regulator should stop working when each cell reaches 1.075 Volts (4.3 / 4). This voltage should be safe for the NiMH batteries, my goal is to not damage the batteries by discharging them too much, is this "protection" enough to avoid deep discharge ?
External monitoring (absence of communication) will warn the user about the low ('dead') battery so the ESP32 should not stay in this condition for long.


texts: Is electrical induction achieved more efficiently by coiling a wire than using a cylinder?

texts:
I'm currently learning the concept of electrical induction and came up to a realization that if we use a cylinder or a huge strand of wire/conductor instead of coiling tiny wires, we should be able to achieve the same (or probably greater) electrical induction.

What should be the obvious and scientific difference and implication for this?

Sorry, newbie question here.


texts: An AC generator can 'lock up' if its timing is off?

texts:
I believe I read elsewhere on Stack Exchange (Physics or Electrical Engineering) about how an alternating current generator can seize up if the frequency of the current does not match something else in the device?

The commenter said the revolving magnets suddenly want to reverse direction so fast that they barely move back and forth at all?


texts: What opamp characteristics for voltage reference

texts: What opamp datasheet characteristics should i look for when choosing an op amp to proivide a reference voltage like in the following image?


texts: Determine if servo pulse length is in a given range

texts:
Quick refresher on servo control: High pulses are 20ms apart and last between 1ms and 2ms.

I know this could be done with a microprocessor very easily, but I want to do it without one because the power supply is shared with the drive engine and spikes that would disturb the processor might occur. Other than that, the circuit is provided with stabilized +5V.

I need a circuit that would check if the incoming servo signal is in a given range (1,7-1,8ms), if it is, the output is to be High, if it is not, then Low. Idealy it would also hold the High for about 0,5s after the pulses are out of range, to ensure that the output is High for a while even if the pulse length is rapidly changing, however that is not a requirement.

The circuit doesn't have to be super precise, as it is only meant for cosmetic enhancement and not crucial functionality of any kind.

Also, this question could use a length-related tag, I have no right to create them and found no existing ones.


texts: How do I find out power requirements from AC / DC specs?

texts:
I have a device with the following AC / DC specs:

100—240V, ~2 amps,50—60 Hz
24V DC @ 6.25 amps

click to see device

How to get power in Watts from this information?

Also, for a second device:
100-240V
1.5A 50/60Hz
60W

click to see device

Where did they get 60 Watts from? Doesn't Power = V * I?

Thanks!


texts: What is the difference between emitter and collector for BJTs?

texts:
the (surely simplistic) model of a bipolar junction transistor one is taught in foundational physics course appears to be symmetric. - So, what is the difference between the collector and the emitter of a real BJT? If the transistor were symmetric one would not make this distinction...

Also:

Do BJTs have a 0.6V voltage drop like diodes?
Are BJTs conductive in both directions, i.e. E-C and C-E?

Many thanks.


texts:
I bought this kind of module for my led light project. Unfortunately it did not come with instructions.

It can be found from eBay with "3.5-28V to 1.25-26V DC-DC Converter Boost Buck Step Up Step Down Voltage Module"

My plan is to set a load on the "OUT" side, set up a multimeter and turn that screw in the down middle until I get the correct reading. Is that the way to fry the board?


texts: Where can I get a 3D CAD model of the lead frame of TO220-2L?

texts: I am new to electronics packaging and searching for a 3D CAD model of TO220 with 2 leads. I have tried at numerous websites without any luck. If anyone has a 3D CAD model of this lead frame or can direct me to the manufacturer I would greatly appreciate. Thanks.


texts:
I want to estimate the throughput of i2c lines and this is the calculation I have done:

Hardware architecture:

MCU <---> i2c mux TCA9548A <---> 8 i2c based IMU sensors MPU6050

What am I trying to do?

Sensors will connect to MCU via multiplexer. There will be a max wire length of 1 meter between MCU and any sensor. MCU will read all sensors cyclically and transmit the data to a PC or a mobile phone over bluetooth/wifi for further processing.

  Total data from one sensor:

  Accelerometer : 3 axis X 16 bits = 48 bits

  Gyroscope : 3 axis X 16 bits = 48 bits

Each read will have some device address overhead = 31 bits (Edited as per JimmyB's comment)

Single read will require 48+48+31 = 127 bits

Assuming that my i2c clock is operating at 400 kHz, I will be able to transfer 1 bit every clock cycle, and hence 400,000 bits in a second.

One complete read = reading all sensors once, i.e. 127x8 = 1016 bits

Thus no. of times I can read all sensor values every second (RPS):

RPS = 400,000 / 1016 = 393.7 assuming my sensors are ready to supply data at that rate.

  Notes from datasheet:

  Output data rate for Gyro = 4 Hz to 8000 Hz

  Output data rate for Accelero = 4Hz to 1000 Hz

Worst case scenario : My sensors will be at a distance of 1 meter (max) from the MCU. Taking into consideration increased bus capacitance and other things that might slow down data transfer, I am thinking 100 kHz will still be achievable (am I right in thinking so?).

Thus reduced RPS = 98.4

Are my calculations correct?

What precautions should I take to improve my data throughput? (twisted cable?, some i2c buffer?)

UPDATES:

I did some research after posting this question. I found one i2c bus buffer P82B96 which allows me to have 400 kHz clock frequency for wire lengths exceeding 20 meters.

Limiting thing is program only I guess, provided my calculations are accurate.


texts: Current clamp circuit after buffer amplifier

texts:
I'm building a voltage supply that uses a DAC to convert a binary string into an analog voltage. The DAC can't source a lot of current, so I'm using unity-gain amplifiers after the DAC output on each channel. I want to make sure that those little unity-gain amplifiers don't get blown up in case the load is suddenly low resistance and draws a bunch of current (my little unity-gain amps can only handle 20 mA).

I was thinking about setting a sense resistor to produce a 0.7V voltage when the current reaches 20 mA, but I'm concerned that I'll be adding some noise to my output voltage (I'm going for low noise).

Is this the right way to go? Is there a discrete IC that is meant for this purpose that I should be using?

simulate this circuit – Schematic created using CircuitLab


texts: Use 4-pin S-video cable connector on RGB LED?

texts:
I'm hoping to make some 4-pin RGB LEDs (R, G, B, GND)  easily hot pluggable, so I'm wondering if 4-pin S-video connectors could be used.

Now, 2 of the pins on a S-video connector are GND, so would it be a good idea to abuse it and connect it to one of the colours? I'm just trying to cause minimal damage if it is plugged to another device with a S video female, and vice versa.

Here's the LED


texts: Using a straw filled with electrolyte as stylus?

texts:
Now what I understand is our human body or a stylus disturbs the electrostatic field of a capacitive screen and thus the mobile calculates the disturbance and does some math and registers a touch.

Now what if I take a thin tube and fill it with some kind of electrolyte (like Vinegar or Salt Water) then put a cotton swab on one end and then use it as a stylus. What will happen...?

Edit: So I tried it with Normal Tap Water. So I had a bit of mixed results sometimes it worked sometimes it didn't. And it did get messy. Now I have to somehow make it efficient.


texts: Which AC bridge circuits are oscillators?

texts:
There are different types of AC bridge circuits like the Wheatstone bridge, Maxwell, Hay, Shering and Wien.

I need to know which ones are oscillators but I still don't get the main reason why the last two bridge circuits are oscillators. I want to find a clear argument.

From what I read, I got:

The Shering bridge and the Wien bridge are frequency dependent and
oscillators
A circuit is oscillator when they have limit cycles, ie they have
closed paths which only occur in systems underdamped


texts: How do you minimize stepper motor vibration?

texts: I'd like to run a stepper motor at a very smooth, constant speed, with minimal vibrations to both the mount holding it and its output. How do I drive the stepper motor so that speed remains constant, even between steps?


texts: Segmented Display With SMD Pads? (Not Thru-Hole or Half-hole SMD)

texts:
I'm looking through a product design, and I've seen these SMD / sticky segmented displays LCD being used.

They are not hand-soldered, the segmented display appears to use some conductive sticky pad that attaches the pads on the board that have the common & signals going to the LCD.

Do you know what this is called specifically?  I've used typical thru-hole segmented displays, and I see that you can get like half-hole module type displays.

Anyone know the term of display that you just stick on the board?

(The white part is actually the backlight, and then the LCD display just goes on top and connects to those rectangular vertical pads circled in red).


texts: Measuring voltage in a 440 V motor start capacitor

texts: How can I measure the voltage in a stand alone motor start capacitor with ratings of 440 volts @ 60 uF avoiding destroying the DVM? We were given a formula for determining the power in a cap, but were not told how to measure the capacitor without changing the out the caps conditions or blowing up the multimeter?


texts: PMSM failure modes? Winding apparently not shorted

texts:
(This may look like a repair question, but I'm actually interested in how the simplest kind of motor failed)

This is the stator of a permanent-magnet single-phase motor from a washing machine drain pump:

There's two coils in series with a thermal interrupter, and a permanent-magnet rotor goes in the gap. That's all.

The rotor spins with force (I can't stop it with my fingers) but irregularly, especially in the first few seconds after applying power:

https://i.imgur.com/137FDoU.mp4

Conventional wisdom says the windings are shorted, so I measured R≈12Ω, ~6Ω each half (it's rated 85W@120V; I don't know of a rule of thumb to estimate the number of turns). In case both halves had similar partial shorts, I unwound one down to the bobbin and didn't find stuck turns or visibly bare copper. The rotor turns smoothly, snapping magnetically every 180°. Shorting the thermal interrupter doesn't change anything.

So, how else can this simple device fail to turn evenly?


texts:
We have a problem in which an amplifier of low frequencies like in the figure is presented. The transistor has these h parameters:

$$h_{ie}=1.1k\Omega, h_{fe}=50 $$

In the input we have \$V_s\$ as a variable and

$$R_s = 10 k\Omega$$

We are asked to find \$A_1, A_{is}, A_v, A_{vs}, R_i, R_i', R_0\$ and \$R_0\$.

I made the pi-model also in the figure. Is it correct?

Can you please help me find what is being asked?

Below is what I think the calculations are:

$$V_0 = i_0 R_c = -g_m v_{pi} R_c$$

$$V_i = ib (Rb || rpi) = V_{pi} \frac{R_b}{R_b + r_{pi}}$$

$$A_v = \frac{V_0}{V_i}$$

$$A_{vs} = \frac{R_i}{R_i + R_s} A_v$$


texts: Is the zeta DC-DC converter topology scalable to 50kW / hundreds of amps?

texts:
Question

The task at hand is to build a 50kW (e.g. say 125VDC 400A out) DC-DC converter that charges a large lead-acid stack with said 400A and accepts a somewhat wide input voltage range. With that in mind, if we allow the input voltage range to be 50-260V, the converter topology will need to be zeta (or similar - buck-boost, SEPIC, Ćuk). If I instead ensure the input voltage is always higher than the output (e.g. 150-800), then the buck topology is likely the best choice (multi-phase buck, a vastly scaled up version of the 12V->Vcore part in modern PC motherboards). The zeta topology however gives me more flexibility in the specific application, so I'm wondering - could it also be scaled to such power levels?

Background

Some guys are building an electric motor testing bench, and the part that I might get involved is the powerful DC-DC converter for energy recuperation. The idea is that a stack of power lead-acid cells (forklift-duty types) would power an ESC, which commands the Motor Under Test. Another, larger motor, would act as a mechanical load to the M.U.T. That second motor, operated as a generator, would recuperate the energy back into the battery stack through a DC-DC converter, which should have programmable target output power (so that we can modulate the torque that the M.U.T. has to provide in order to keep the set RPM).

More current to the battery leads to more mechanical torque, so the M.U.T. will draw even more current to keep up, so in the end the battery will still be drained, but only with the power lost as inefficiencies in the system - not the full 50 kW.

Specifications

The generator will be a 3-phase permanent-magnet type
The M.U.T. will be up to 50kW, so realistically the DC-DC converter only needs to handle 40kW. But I'll aim for 50kW to have some margin.
The battery voltage could be as low as 24V, and as high as 120V. Of course, 24V batteries will only be used for testing low-power low-voltage motors, which are nowhere near 50 kW.
400A will be the max amps we'd want to get into the battery, regardless of its voltage. So 50kW are only with the highest battery voltages.
50kW will only need to be sustained for a few seconds, and the entire test run (with varying power levels) is less than 1 minute.
We'll only build one, or a handful, of these converters. Component cost is not a huge priority. Development cost is more relevant.
Other guys are handling the mechanical part (motors, bearings, torque measurement, shafts, ...)

Zeta topology option

I've read a Microchip app note (High-Power CC/CV Battery Charger Using an Inverse
SEPIC (Zeta) Topology) which presents a 100W charger in the same general direction. The central part of the converter is this:

I was thinking that maybe, maybe, if I uprate the power components for voltage and current, and provide many more parallel copies of C1,C7,C8, Q1, Q2, the circuit can be scaled to tens of kW. Then it would give me more flexibility, as this way I don't need to worry about the corner cases that the other option has.

Buck topology option

Instead I can push the guys to select a motor with a very low Kv for the generator (or use a transformer after it), so that the input voltage to the DC-DC converter is always higher than the desired output. This either calls for a motor with ridiculously low Kv, or a 3-phase transformer, if I want to cover the worst possible case: battery voltage 120V, test at low RPM. The transformer options is likely the best, if also provided with bypass contactors to handle the low battery voltage case as well (to avoid ridiculously large input:output voltage ratios).

Other thoughts

Of course the option to lose the energy from the generator in a resistive grid is possible, but is viewed as inefficient and will cost more to provide the necessary cooling
probably a permanent-magnet generator is not the best idea. Come to think of it, using an alternator is maybe a fruitful direction, I'm not sure why the guys are fixated on PM motors, maybe I'll be able to persuade them otherwise.


texts: I'm looking for a type of potentiometer (ideally about 500k) that has a feelable click switch at both ends. I have only found ones with a single on/off switch. What's the term I need to look for?


texts: Electronic switch with high number of poles

texts:
I have two cables each with 10 pins, that connects between two PCBs. I would like to be able to connect and disconnect them from each other. Something like this link to 10 pole mechanical switch, however instead of pressing manually I want to automate it.  I have also looked into relay boards but have not found any that have several outputs and it would be too bulky having 20 relays.

To clarify I need to connect/disconnect 20 pins with one signal, it is not necessary to be able to control them individually. The pins are used for SPI communication, however I was hoping to find something like this 4 pole relay but with 10 poles instead. We use this for testing purposes and not in the final design, as of now we manually disconnect the cable during each test. So I am looking for some already created device that can act as the "dis-connector".


texts:
In a circuit having two diodes with different conduction voltages,how to know which diode is in ON condition.
Let the circuit be

simulate this circuit – Schematic created using CircuitLab

If D1 diode has cut in voltage of 0.6 and D2 having cut in voltage of 0.2 then what are the conditions of D1 and D2 whether they are ON or OFF and is the current flowing through R3. Please provide the explanation. Thanks in advance.


texts: Can you overcharge a Li-Ion on CV charging when charging voltage > saturation voltage?

texts:
This question is almost answered in "Charging li-ion cell using constant-voltage only" but I wanted to know if this is true for an extra long period of charging.

I bought a broken electric bike from my nephew and the battery pack is fully functioning. I wanted to build a simple UPS for my server using the li-ion pack(LiCoMn).

Since I don't care about slow charging and want something relatively simple, I wanted to charge the batteries via a buck regulator connected to a laptop power brick.

The charging voltage for the pack is 21V(4.2V per cell and 5 in series) and the buck converter outputs 20.5V +- 0.05V.

Theoretically since the charger cannot charge the battery past the charging voltage, there is no danger of overcharging. However, as an UPS, this device will be plugged in for long period of time and I was wondering if there is any danger to this practice.


texts: I was wondering why I cannot edit footprint of LED 1206 to take care of LED 0805 as well so that I can mount one of them depending on the availability. To do this, I have to increase the pad size of 1206 footprint on the inner side to give a clearance of around 1.2 mm between two pads. I want to know the impact of increased pad length in the PCB.


texts:
I am creating an open source dive computer (www.diydivecomputer.com) and I am having a little bit of a problem trying to figure out how to power the device on and off.  The problem is that the device needs to be completely sealed since it will be operating underwater and at high pressure (up to 200 psi) so there cannot be any holes in the case for a switch.  I will be using hall effect sensors/magnets for the user interface buttons and would like to be able to power the device on and off using one or all of these buttons (i.e. press any button to power on). I would also like to be able to power off the device by holding down one of the buttons for several seconds (to reboot the device in case of a software crash).  Lastly, I would like the device to automatically power on when the device is emersed in water.  I will have connections leading to the outside of the case for charging so I could add another for water sensing (or somehow use the charging pins). Of course, the power consumption when the power is off needs to be zero or as close to it as possible since the device may be stored for months between uses.

I am a software engineer and electronics hobbyist so this is a bit outside of my capabilities.  I know this is "question" with no simple answer but if anyone can point me in a direction, I would appreciate it! However, if you do find this an interesting problem I invite you to join the project! I could use the help!


texts:
I currently have this PCB layout for a project:

Now I'm unsure if I should invest more time to get rid of some vias or if I just should finish it off and order the board.

Do vias matter for such short traces? For comparsion: the ICs are TSSOPs and the passives are 0603s.

Additional Info::

No I don't know the maximum signal frequency yet. But it will be around 10-100kHz.
ICs are MAX312L and 74LVC125AT

So it boils down to the question 'when should I stop working on a PCB'.


texts: Reading Voltages using INA125p with Arduino

texts:
Complete electronics beginner here. I'm attempting to build a weighing scale with an Arduino.

I'm attempting to follow this tutorial, with the shield that they use.

I've arranged my load cells on the scale into a Wheatstone Bridge, and I can get some readings just by taking a voltage reading from the two cells marked V+ and V-. The board has terminals that are linked to a INA125p, and the pins should give an amplified reading.

Pin A1:0.96
Pin A2:1.42
Pin A3:5.00
Pin A4:5.00
Pin A5:5.00

Regardless of whether I have the scale wired in or not, I get these readings from the individual pins. The scales seem to be able to take power from the Arduino shield.

The scales that I have are different from the ones in the example. From what I can figure out, the yellow cables that they reference turn their particular scale on when weight is put on it.

I've put the wires where I take the reading into the 2 and 4 terminals on the circuit board that they have (where the tutorial references a differential signal), but again, it makes no change.

  unsolder or cut the white wire that is referred to as G3 (Wheatstone bridge mass) on the original printed circuit, extend take it to terminal 1 on the new printed circuit;

  unsolder or cut the white wire that is referred to as G2 (Wheatstone
  bridge positive) on the original printed circuit, extend take it to
  terminal 3 on the new printed circuit;

  unsolder or cut the white wire that is referred to as G1 and G4 on the
  original printed circuit, extend take it to terminal 4 and 2 on the
  new printed circuit (differential signal on the Wheatstone bridge)

I've attempted lots of different combinations of cables and terminals on the new circuit, but it appears to make no difference to the readings.

My question is:
Based on the tutorial and the drawing above, am I taking the readings from the correct place? Are there any things I'm obviously doing wrong with the circuit itself?

I apologise for the vague nature of this question, but I am a complete beginner trying to figure this out, and I am struggling to follow the tutorial. I'll try and provide any additional information that you need.


texts: High side transistor switch with 9V LED driver

texts:
I'm trying to build a high side switch using a PNP and NPN transistor together to run (7) 10W LED's off of a LED Driver. It's part of a multiplexing circuit and I do not have the option to make it a low side switch. I also need to be able to switch it quickly. I found the schematic below and have tried to recreate it with no success. I'm using a 2N3906 PNP with a 2N2222a NPN. The image below shows a 12V power supply but I'm actually using a LED driver that is 9V and 900mA. My load is 7 LED flood lights connected in parallel.

Here is a picture of my breadboard connection. The LED driver is blue + and yellow -. The black wire goes to + on my LED's and the white wire is the - on the LED's. Red is +5V on the Arduino and Brown is GND on the Arduino.My understanding is that when I connect and disconnect the red +5V wire the lights should turn on and off. My issue is that the lights are always on.
Please help!! Thanks


texts: Setting RF frequency by putting screwdriver into coil

texts:
I am working on a small FM transmitter circuit. I don't have a trimmer capacitor so I can't set the frequency.

I remember that when you put something like a screwdriver, the frequency changes when you move the screwdriver.
I tried putting a screwdriver into coil, but it didn't work.
What kind of "screwdriver" can make that frequency change?

(I've removed connection between two pins of microphone)
(6 turns, 9mm coil diameter, 1mm copper diameter)

I hope I could explain it!

Solved: Thanks to @JRE, I needed a screwdriver made by a ferrous metal!


texts: 10GBASE-R 64B/66B Encoding/Decoding Unusual Control Block Formats

texts:
I need to design a 64B/66B decoder on receiver side of the GTY transceiver. Currently, I get 2 bit header and corresponding 64 bit descrambled payload at positive edge of every other clock cycle. So now I need to decode the 64B/66B encoded data according to the table below. (IEEE 802.3-2008 section 4, Table 49-7)

It is easy to understand all termination control block formats and data block format is trivial. However I am not sure how control block formats with block type fields 0x2d, 0x66, 0x55, and 0x4b. I am guessing that:

- 0x2d, 0x55 and 0x4b types are used when for some reason transmitter side wants to send 3 or 6 bytes of data between start and termination of a packet

- 0x66 is used when for some reason transmitter sends start together with 6 byte preamble, but I think this does not make much sense

I do not think that my guesses are correct, even if any of them is correct I do not think that it is complete, so I have some questions regarding this issue:

1. Is any of my guesses at least partially correct?

2. Can you explain why, how, when and how often those 'Control Block Formats' used?


texts:
Hope someone can help me out and point me the right direction to solving this.

I am trying to do a voltage drop calculation to see the VD % for the cable selected. The following are the values,

Current: 140A (I)
Resistance of Cable: 0.0001 Ohm/m (R)
Reactance of Cable: 0.0000704 Ohm/m (X)
PF: 1
Distance: 300m (L)
Voltage: 20 kV (20000V)

I am using the following voltage drop formula that I found in a very old school notes (can someone pls verify this formula)?,

Vd = (I x (R cos theta + X sin theta) x L) / 1000

If I input the values into the formula, my answer is 0.266V. This does not  look right for me as I will get a weird VD %.

Can someone please assist? Thanks!


texts: Can I use a PC Microphone in a PIC with ADC?

texts: I want to do an FFT on some music, I found an electret board so connect directly to the ADC port, but I was wondering if it's possible to use a normal computer microphone, anyone know a tutorial or something? or how to do it?


texts: Why does the LTspice op amp stability tutorial recommend open loop analysis?

texts:
I have performed a hand analysis on an amplifier circuit that I am suspicious of, and I am still suspicious, so I want to validate my hand analysis with LTspice.

I found this tutorial online:
http://www.linear.com/solutions/4449

It recommends to find the "open loop gain and phase response" to analyze the phase margin. It discredits the "closed loop response" from having the necessary information to analyze amplifier stability.

I can't post my exact circuit, but that shouldn't matter. Here's an example circuit, modified as instructed by the tutorial:

My prior understanding was that the open loop response of an op amp was just the op amp by itself with no feedback circuit, and that the closed loop response contained all the information needed to analyze an amplifier with its feedback circuit.

Can someone please explain what the LTspice tutorial is talking about?

Thanks


texts:
We have a product (optical detector), one client had an issue with false alarms due to their radios they use on site.

Did some modifications, added a ferrite bead to the cable and put a driven guard shield around the sensor. With the PCB with these mods, and no housing just lying on my workbench, it won't trigger by radio short of putting the antenna right beside it. They are unlikely to do this, so this looks great.

However, I put it back into the body of the detector it appears to negate these changes entirely. It false alarms again at range again.

My question is why would this occur? I went so far as to make sure all the metal plates and the body were stripped of paint on the joints. With only three openings (much smaller then the 150 MHz wavelength) on the unit for the sensor window, pot knob, and cable grip.

Shouldn't this be a Faraday cage and block everything? I tried grounding the body to 0 VDC and Earth or both, no effect.

What am I missing here?


texts: Is there a reason the offset of this opamp is done like this?

texts:
I recently found this schematic from a project at university (drawn by our lecturer). It's a low pass filter that also adjusts the gain, and adds an offset of 1.5 V (the input signal can be positive or negative and this filter feeds an ADC).
However, I just realised that the 1.5 V offset at the positive pin of the opamp doesn't include the capacitor. Is there a reason the 1.5 V is not connected to both components?

Thanks for your help!


texts: Why doesn't the relocation of this resistor affect the circuit's total resistance?

texts:
Why does moving the 470Ω resistor in these examples have no effect on the total resistance between A and B?

This is a new question regarding the answer given here by @helloworld992.


texts:
First I want to say that I have no experience with capacitors heating up, so this one may be obvious.

I've recently replaced a set of aluminium electrolytic capacitors on an ADSL modem. The original ones vented. They were rated at 105 °C, so I got some 105 °C (of same voltage rating) capacitors as a replacement. Unfortunately, I couldn't find capacitors of the same size, so the modem is now outside of its plastic case.

Anyway, I noticed that the capacitors are getting hot. This is first time I noticed something like that. All other capacitors I've touched were always cool, even when used on a warm PCB. So I'm getting 45.5 °C on the cap of the capacitors. The outside temperature is 27.8 °C. The temperature of the PCB itself (measured from an exposed, unpopulated, solder pad) is 35.7 °C.

I do understand that the capacitors should be able to take the temperature without any problems, but it still seems a bit too high to me.

So is it normal for capacitors to heat up this much? I was unable to determine exact properties of the original capacitors (and Google isn't familiar with inscriptions on them), so I got some "low-ESR" capacitors just in case.

UPDATE: The capacitors are rated at 25 V (working at 12 V) and have capacitance of \$470 \mu F\$. The modem was bought in 2008. and was working more or less continuously (with no more than two months downtime for that period) since then until a month ago.


texts: How to connect Raspberry Pi to House Alarm Serial Bus (DSC Keybus)

texts:
I have a DSC 1864 House Alarm and I want to connect up my Raspberry Pi's GPIO to the Keybus (a serial data communication protocol used by the alarm).

I would say my knowledge of electronics is novice to intermediate.

Info:

The Keybus is a 4 wire serial data bus - +12V, Ground, DATA and CLK.

The clock runs at 1khz from what I've heard.

The Logic is 0-12V I believe (I tested with a multimeter since I dont have a scope and got 12.84v on the +12v and a continually changing 6-8V on both Data and Clk lines as to be expected.)

The Raspberry Pi has a 0 - 3.3V logic level, With anything above 2.8V being HIGH.

Quesiton:

My question is how best to connect these two, with the Pi purely just eavesdropping on the keybus - I dont need to write to it, just read from it.

I'm concerned that if I dont have a high impedance circuit, that the Raspberry Pi will act as a drain on the circuit and disrupt communications between the alarm panels (bad!).

Possible Solutions:

Use an Optocoupler - Not a good solution as I've heard they are slow and draw a lot of current on the transmitting side.
Use a logic shifter chip - Possibly, but I dont know how to find the right one for my needs, and it has to have high impedance so as to not disrupt the keybus circuit.
Use resistors as a voltage divider - This is the route I was planning on going. I calculated that the following:

simulate this circuit – Schematic created using CircuitLab

Will give 3v at the Pi when DATA goes to 12v, but will fry the GPIO pin if the voltage goes above 13.5v.

It should provide 1.05mA to the Pi - I'm not sure if this is enough for input purposes.

Further Reading:

Resources I've found while researching this:

http://www.avrfreaks.net/index.php?n...topic&t=104139
http://www.house4hack.co.za/dsc-keybus-talk

Any help / suggestions here would be greatly appreciated.


texts:
This is my stereoscopic system:

I'm using a zedboard to pilot two i2c-camera MT9D111:
http://www.dragonwake.com/download/camera/MT9D111/mt9d111_rev5.pdf

Camera PCB Information:
https://drive.google.com/file/d/0B2_rhDNAxM4sMWM2MmQ5MWMtNTFjMS00Y2YzLTgzNGUtYjEwMWZlMDg1NjM2/view

I'm encountering problem using i2c-cadence driver on an ArchLinux Distro.

The two i2c cameras are always detected by i2cdetect tool, but if i try to write to them sometimes they work correctly, but other times i get:

Something went wrong with write()! Error: 11 - Resource temporarily unavailable (addr:93)

or worst:

Something went wrong with write()! Error: 6 - No such device or address (addr:93)

I do not know why this error are popping out totally randomly, can someone explain this weird behaviour? Are the wire to long for I2C protocol (400KHz)? Is something related to the power supply?

I'm going crazy about this issue, any help will be useful.


texts: How to use SPST switches to change voltage polarity?

texts:
Top is original schematic.
Edit: It's been brought to my attention that if the wrong switches are open/closed I could end up messing up my unit and DUT. How can I avoid this?

So i am using a keysight general purpose switch(spst form A) and I am trying to figure out how to change the voltage polarity since I only have a single power supply. I have this diagram that one of my friends helped me with but I am bit confused. If i close switch 1,2,4 would i be getting positive voltage? If i close 6,3,5 I get negative voltage? I guess I am just having a hard understanding what happens when i connect power to NO as opposed to COM. Any help is appreciated or any good references on understanding switches.


texts:
I've got an IC that requires 3.3V Vdd and 550uA.

My supply is at 5V.

I'm reading all over the internet that powering it via a voltage divider is not advised and I should get a voltage regulator/buck converter.

Nowhere did I find anything about a dropping resistor. Using this calculator I've calculated that a 3400 ohm resistor would create the required 1.7V drop and limit the current to the appropriate value.

I'm just here for a word of comfort, is my logic correct?


texts: What is a Kva in simple terms, for somebody who doesn't know electrical engineering?

texts:
I have a DC circuit that runs on 8.1 A × 12 V (97.2 W). Power is supplied from a AC-DC transformer that plugs into a socket.

How many of these can I run in a place that provides a maximum of three-phase 30 kVA?

I cannot make sense of the kVA definition and it is beyond my comprehension. I do not understand real power, apparent power, power factors, resistive load, reactive load, linear load, nor can I calculate these.

Is there a simple answer?
Help appreciated


texts:
I would like to know if a circuit breaker is polarized if it looks like this.
I would also like to know how I can manually turn off these breakers and how to reset them
Thank you!


texts: Can I use ferrites for the ground connections?

texts:
I may have an issue with conducted EMI through the ground connections between devices in a system. There is specifically a device which clearly creates noise on the measured signal from another circuit with a scope (noise is reduced when it's off). That scope has to be connected to both that noisy device and the measured circuit so I'm suspecting HF noise is conducted through the ground.

I am thinking about putting ferrite beads on the ground connections for example on the ground connection from all the devices (especially the noisy one) to the scope, but that layout looks like odd to me. Does it make sense to have a ferrite for the ground lead of a coaxial cable? Is there any other way?

Additionally, the scope is directly connected to the measured circuit, which is a resistor with one grounded lead (It's a current consumption measurement). Another approach I'm thinking about is a differential amplifier, does this approach looks better? Can even be necessary a combination of both?


texts: Optical heart rate sensor vs bioimpedance sensor?

texts:
I didn't know a better place to ask this, so here it goes. For activity trackers, Fitbit has the Charge HR with an optical heart rate monitor, while Jawbone has the UP3 with a bioimpedance sensor for heart rate.

Can you please explain the differences between the two. Also, diagrams would make it more understandable.

Info about optical sensor:
electronicdesign.com/displays/build-your-own-optical-heart-rate-sensor
Also, are any diagrams from here relevant?

On Jawbone's blog, there is some info:

  Bioimpedance measures the resistance of body tissue to tiny electric
  current to enable the capture of a wide range of physiological signals
  including your heart rate. If you've ever measured your body
  composition such as fat content, this is very similar. Our choice to
  use bioimpedance technology sets us apart in three key ways:

  Battery life. Because bioimpedance requires significantly less power
  compared to optical sensors for same level of accuracy, we can deliver
  a smaller form factor and longer battery life Physiological signals. A
  single platform utilizing bioimpedance sensors captures a wide range
  of signals: heart rate, respiration rate and galvanic skin response
  (commonly known as skin conductance) Updatable technology. Given the
  versatility of the sensor platform, we are able to (and we will)
  unlock exciting new features with a simple, free, over-the-air
  firmware updates in the coming months


texts: Which transistor should I use in place of a 5V relay to adjust brightness of lights (230V) with the Arduino?

texts:
I want to control brightness of lights (230V) with the Arduino, and I know that relays will just switch the lights on/off. If you have the circuit or any idea about which transistor to use and how to use then please reply.

(Sorry for my English.)


texts: SD card initialization problem - CMD8 wrong response

texts:
I am trying to interface an microSD card to a microcontroller board (FRDM-KE06Z) using FatFS code. I only modified SPI parts for my application. Besides digging into FatFS code also I checked this guide

When I send CMD0 to the card the reply is correct:

But when I send CMD8 to identify the card the response is totally wrong (after 0xFF there should be anything with MSB set to zero):

I have checked:

Different SPI modes 0/1/2/3, clock speeds 75kHz and 150kHz
Two different SD cards (brand new 32GB SanDisk Ultra HC 1 and an old SanDisk 2GB)
I do send dummy clock cycles after power, I also wait a couple of seconds before doing anything with the card
Wiring is short, so signal integrity should not be the problem
The same happens with and without logic analyzer attached
Plugging the card after MCU pins are initialized, waiting a couple of seconds and starting the code
CS timing is very relaxed (couple of miliseconds before data is sent, many miliseconds between CMD0 and CMD8)

What can be the reason my cards are failing to properly respond to CMD8, while responding correctly to CMD0?


texts: How to send the result of a count from the register TMR1 (used as counter in the PIC 16f877A) to sevral output pins on the same pic?

texts:
I'm using a PIC 16f877A with a D/A Converter (AD667) in order to transform the result of a count into a analogue output to use later, but I find my self incapable of sending this 12 bits from the PIC to the AD667, is there a way to do so using MikroC ?
here is the code I'm using:

// sbit tmr1 at RC0_bit;

void OutTimer1 (void)
{
    while (portc.b0==0)
    {
        tmr1= porta= porte = TRISC.B2, TRISC.B3  ,TRISC.B4 ;
        if (TMR1L == 0XFF)
        {
            TMR1H ++ ;
         }
    } // end while
} /// end OutTimer1

void main()
{
    OutTimer1();
}

`
am I on the right truck at least?

in the simulation with proteus i couldn't find an AD667, so  used what i found in the library dac 1219.


texts: Live wire touching ground, sends power back through TV cable

texts:
This bizarre show happened twice at my house. The first time it happened I only realized something was at fault when I was having to call the cable company every two weeks to fix the cable internet. One time a technician came back and said the connections were burned up at the pole and as soon as he managed to unplug it... sparkles.

I plugged a lamp between neutral and ground, and there was light. I called in a horrible electrician at the time that simply disconnected ground from the affected region of the house, the garage.

Recently it happened again, an outlet from the washing machine overheated because the dryer was extending that outlet straight from it, no pigtail. The plastic overheated and melted some of the cable's coating and once again ground was live and the TV coax too!

I'm mature enough to understand the poor piece of work done, fixing, inspecting things now, not trusting any electrician, but I'm having trouble investigating the odd ground behavior.

Why did the TV send out power from the live ground :( instead of it going to earth? Not a single breaker ever went off. I'm no longer connected to the street's TV service. Satellite and fiber now. I'm not sure what would ground things now. Has anyone seen such thing?


texts: Diodes circuit analysis problem and voltage calculation

texts:
I'm learning about diodes. In one of problems which book has solved, it says

Vo=((Vi-2)/2) +2

when both diodes are off.
I can't understand why we have "+2"
here.
My calculation of Vo is without +2

Vo=((Vi-2)/2)

Which on is correct? If the first way is correct, why?


texts: Is The Magnitude of Gyro XYZ Meaningful?

texts:
Say I have a gyro that outputs degrees/second, and I take the euclidean magnitude of the x,y, and z rotations:

$$
\text{magnitude} = \sqrt{x^2 + y^2 + z^2}
$$

Is this actually useful? Is magnitude now "total degrees/second"? Or does the weirdness surrounding non-commutative addition of rotations come into play?


texts:
What would be the least expensive way to boost a DC voltage?

The aim is to convert 1.2 V/1.5 V (from an AA/AAA cell) to 3.3 V to power a small 8-bit microprocessor, like Atmel ATtiny45 or ATtiny2313, and also (if possible) 6 V to power a buzzer.

Also, what would be the maximum current one could draw safely from an alkaline battery, after boosting it to 3.3 V/6 V?

Finally, how I could compute the duration for which the alkaline battery would last, given a certain consumption?


texts:
In most CMOS applications, the use of resistive source degeneration to
  reduce noise and improve matching is restricted due to headroom
  constraints.

A) Could anyone elaborate on this statement extracted from "Ultra High-Compliance CMOS Current Mirrors for Low Voltage Charge Pumps and References" ? Besides, how do we obtain the equation of output noise current = (16/3)KT*gm in the same document ?

B) For http://www.ele.uri.edu/courses/ele447/Slides/CurMir/Chapter_07.pdf#page=78 , the Thevenin resistance would be 1/gmREF in series wth Rb, right ? If so, why there is a factor of (1+gmREF*Rb)2 in the denominator ?


texts: How to invert colors in Altium for Soldermask application

texts:
I am trying to invert black and white in Altium for the "Bottom Solder" *from this one *to look this one
 from https://www.youtube.com/watch?v=7ISmS7HuXSE. As it turns out, while doing screen printing the white part should be black while the black should be White. I appreciate your guidance on the way forward with Altium or any other PCB design software.


texts: Why is my 10k NTC thermistor on average accurate to 2C

texts:
I am trying to figure out what is causing the 2C inaccuracy in my thermistor calibrations, my goal is to get my accuracy down to > .1C. I am using the KS103J2 10K NTC thermistor. To calibrate my thermistor I am using a vernier temperature sensor both the surface probe and stainless steel probe. I calibrate by putting the probe as well as my own NTC thermistor inside a beaker with water, let the probe and thermistor equilibrate with the water. I input the vernier probe's temperature, which is displayed by Logger Pro, into the Arduino Uno serial. The code then takes 10 resistance readings from the NTC thermistor, averages them and then uses that as a point (temperate from vernier probe, resistance from NTC thermistor) as a point of calibration for the Steinhart-hart equation. The code calculates the A, B, C coefficients. I then test the calibration by inputting the resistance into the Steinhart-hart equation which returns the temperature based on the value. I find the difference between the outputted temperature from the Steinhart-hart equation with the vernier probe's temperature to find the "error - 2C.

Setup and General Information:

10K NTC thermistor (waterproofed with liquid electrical tape) with resistance range 35000 - 1,200 Ω
Arduino Uno (10-bit ADC) and breadboard
Temperature range: 0C to 75C
Using water to sample temperature

What I have tried to fix my error:

Switching to a different NTC thermistor for calibration

  Result: No difference in accuracy (stayed around 2C)

Checking the precision of my voltage divider

  Result: Very stable, I tested this by replacing the NTC thermistor with 3
  different stable thermistor (1K, 10K, 100K).

Switched to from 5v to 3.3v with Aref

  Result: The error remained the same.

Calculating maximum ideal error with 10-bit ADC

  Result: at the ideal maximum, the error should be .25C at 75. The rest
  of the range should be >.2C.

Checking the accuracy of the Steinhart-hart model with an NTC thermistor
resistance table

  Results: the model predicted the temperate very accuracy.

NTC Table:
20.80C    11,868.8 ohms
20.85C    11,844.3 ohms
20.90C    11,819.9 ohms

My NTC thermistor values with Steinhart:
20.82C    11858.97 ohms

What I think the problem might be:

Imprecision in the vernier probes (I tested with 2 different types of
probes and the error still continued, they are rated for accuracy of
+/- 0.2 C, but their precision is unknown).

Limitations:

I cannot use external ADC's
I cannot use thermistors with waterproof housings

Circut:


texts: Seeking simple circuit for converting 5vdc to ~15vac

texts:
I picked up some sample smart materials because I have a small project that I want to put 'magic glass' on the outside of so to speak.

I picked up a couple of different sample pieces from a couple different sources to try and one came with a AC adapter/converter to drive the 'clearing' of the smart film, the other came with a small battery operated unit.

Either one seems to clear the material, but throwing the testors on them produced different results.

The AC version (110vac US plug) seems to output ~17vac @ 60Hz. It also seems to clear the film a little better.
The DC version (two AA batteries at 3VDC) outputs ~7.5vac @ 500Hz.

I'm not sure if this smart film needs specific frequencies or not, but this was a purchase off banggood of just a couple small sample pieces about 10cmx15cm each.

My project uses primarily 5vdc with access to low-current 3.3v sources. But I'm guessing this thing would draw too much current (for my 3.3v using the existing driver board) to clear all four panes even after I cut them down to fit inside the project.

So I'm guessing I need something that will generate an AC voltage in the 15v range somewhere between 50-500Hz to drive this thing but I know nothing about building oscillators or inverters. I would also prefer something that could run straight off a 5v source.

(I'm running out of room to put new DiY components. (I'm already stuffing a few props, a servo, a stepper motor, at least 25 LEDs, an i2c PWM board, ultrasonic vaporizor, and a a Raspberry Pi with a ReSpeaker shield a pair of speakers somehow inside of a 10"x6"x6" brass lantern! The smaller/simpler the circuit the better)

Any help is appreciated.

--EDIT 1--
the 110vac which outputs 17vac @ 60Hz is only about 1.4ma
The 3VDC which outputs 7.5vac @ 500Hz is 7ma


texts: Determining changing values of C in RC circuit

texts:
My problem is related to the change in the membrane capacitance of a cell (link to paper). The electrical properties of the cell can be modeled using a battery, a resistor and a capacitor in series.

I apply a sinusoidal wave (5 kHz, 10 mV amplitude)

During the process I apply an external stimulus that changes the capacitance of the system. This can be infrared light or anything that generates a pulse of heat.

simulate this circuit – Schematic created using CircuitLab

The results I get for 1 trace is the following

If I repeat this several times I get something like this

I would like to know how the applied stimulus changes the capacitance in time?.
My guess is that I could obtain the instantaneous phase shift and amplitudes from the several traces I have but I don't know how to do that.

The data can be found in the following files:
Applied voltage
Current response


texts:
I have a robot that has a load of 60kg and it has to move using 4 stepper motors. I saw from previous searches that the torque required by the motors to move is Force times the wheel radius.
COF = 0.55
Torque = [(60 x 9.8) x 0.55] x 0.05 = 16.17 Nm
I would like to verify if the motor I have available will do the job. I assumed that aerodynamic drag is negligible since it runs 0.5 m/s at most. There is also no slope on the floor.
And since I would be using omnidirectional wheels, are there additional torque needed when it moves sideways? Thank you
Motor:
Wheels:


texts:
I have a circuit that is essentially just a 1kV DC source connected to a very high resistance (basic circuit outline), within which current in the range from 0.1nA to 500uA flows that I am trying to measure using an Arduino  (the current varies because the resistance varies due to outside factors). I had the idea of using this (or similar) connected to an Arduino: https://www.adafruit.com/product/904

However this works up to 26V and only has a 0.8mA resolution.

To solve this I first thought of using a potential divider to have a parallel section of the circuit with voltage reduced to ~13V where the INA219 can go (reduced voltage section), with high resistance resistors so essentially all the current flows through this section.

However I now need to amplify the current in this section to a value the INA219 can measure. After looking things up I thought that a good idea for this would be a Darlington pair and implemented it like this: with Darlington pair. However I find there's no amplification for this. Am I implementing the Darlington pair incorrectly or does it not work for such small currents, or is a Darlington pair completely the wrong idea here to amplify the current? If this is the wrong way to go about it, what would be a good way to measure the current of this low current high volt circuit with an Arduino?

Edit: I've included a schematic of the diagram that I think is described by Olin Lathrop's answer

simulate this circuit – Schematic created using CircuitLab


texts: Polygon subtraction error. Altium rules are ignored

texts: I need to subtract a small polygon from my base polygon. However, after subtraction, my rules are ignored by the Altium. what is my mistake?


texts: I keep seeing similar diagrams of RAM like this abstract picture of a simplified RAM Layout. So I just arbitrarily selected this picture but my question is about this layout in general. My understanding is that the whole selected row sends their memory contents down their column lines and the column decoder selects the appropriate one to output. So is this understanding correct? And is the Row Decoder implemented by a decoder-like a 3 to 8 decoder- and is the Column Decoder a multiplexer? And are each of the column lines a bus? Is this how most RAM works in the big picture, for both SRAM and DRAM?


texts: Using a 12 V 3 A bilge pump on a 12 V 8.5 A LED power supply

texts:
I recently bought the following for a grey water system project I'm working on:

3 x 12 V, 3 A bilge pumps
1 x 12 V 12.5 A power supply

I'm not an electronics expert, so my assumption was that the power supply should easily power the bilge pumps. This was not the case. The moment you connect the pump to the power supply, it's like it sucks the power supply dry (the LED actually dies). The bilge makes half a spin every 1.5 seconds or so, the LED goes back on and the process repeats. So I thought there is something wrong with the power supply.

Because I live in South Africa, shipping the part back to Amazon was a bit of a mission, so I decided to buy another power supply locally as I thought the original was faulty. This one was 100 W, 8.5 A supply.

It works a little better; the pump actually spins up after the third 1.5-second burst. If it is submerged however, it's again as if the power supply cannot supply enough power to the pump. As long as I get it spinning before I submerge it, it works fine. It's almost like the supply needs some help getting out of the starting blocks.

It's obvious there is a critical piece of knowledge I don't have here. Can someone please explain why a power supply rated for 12.5 A or 8.5 A (12 V) cannot power a 12 V, 3 A bilge pump?

I run it off normal 220 V AC, 50 Hz.


texts: I'm looking for a high current DC switch (able to switch something like 5V@30A) and I've encountered several DPDT that might do what I need, however they are only rated for AC applications (3A@250VAC or 6A@125VAC). Are these rating convertible to DC? or is that something that only the facturarer would know?


texts: Parallel wiring battery and amplifier board to a 12VDC 1A power supply safe?

texts:
i built one of those diy boomboxes but have trouble charging ang using it at the same time. Currently i have to use two different DC wallwarts to charge the battery and power up the amplifier at the same time because the battery would cut power to the amp when its charger is connected.
My idea is if i wire the battery and amplifier parallel to the charger would it charge the battery and power the amplifier at the same time?


texts: Simple way to generate a two-level pulse?

texts:
I am looking to generate a two-level pulse as follows, where the adjustable parameters are \$V_1\$ and \$V_2\$ between 0 and ~5V, and \$t\$, ~5 to ~50 ms:

The trigger pulse length may be anywhere from a few milliseconds to tens of seconds. If its duration is less than \$t\$, then the generated pulse should be \$t\$ long with amplitude \$V_1\$. \$V_1\$ is always greater than \$V_2\$.

Of course, it can be done using two resettable monostable multivibrators (one as a one-shot timer to generate the \$t\$-long pulse, and another to produce a second pulse, starting after the end of first and continuing until the trigger goes low), plus buffers to scale the outputs from each of these. However, by my reckoning, this requires at least a dual opamp and a dual timer IC such as a 74HCT123, plus two potentiometers, miscellaneous resistors, and a timing capacitor (and, ideally, some Zener diodes to make it independent of the power supply).

Can the same be achieved more simply (fewer components; no microcontrollers), while still accommodating the adjustment of the three parameters? I don't think so, but I would be happy to be surprised.


texts:
I'm planning on using this optocoupler in a PCB I'm making.  I've never used one before so I want to make sure I'm doing this correctly and got the right numbers off the data sheet.

The image below is a simplified version of how I set it up.  If I read the data sheet correctly the LED has a 3mA max current and around 1.0V forward voltage.  The 1.8K resistor should limit the current to about 1.5mA.  Then a 100 ohm resistor on the collector to keep it well below it's maximum of 10mA with a bit of room to use higher voltages if I want to in the future.

It will always have a 3.3V signal but I'd like to have the option to use different voltage motors and servos on the other side.


texts: Is it possible to know what is the dielectric voltage between earth and conductor of those cables?

texts:
I am looking to know what is the maximum voltage (dielectric voltage) that it can be applied between the conductors of the cable and the earth (not into the cable). Usually I look for a term which is called " Voltage Test " but in the datasheet below I am not able to find the informations :
https://fr.farnell.com/amphenol-ltw/hmc-05bffm-sl8a01/nmea-micro-c-5pin-f-conn-f-pin/dp/2912028
https://media.digikey.com/pdf/Data%20Sheets/Phoenix%20Contact%20PDFs/1669770.pdf
Thank you very much and have a nice day.


texts: Simultaneous Cathodic Protection and 4 Wire Resistance Measurement

texts:
I am making an electrical resistance sensor for erosion rate measurement using the Arduino. Since my sensing element is a thin strip of carbon steel, I have to ensure that it is protected from corroding, so I can measure pure erosion. I am measuring the resistance using the 4 wire method, and amplifying the potential drop across the sensor using the TLC2652AC chopper-stabilised amplifier; the amplifier gain is 10,000.

I am confused about the cathodic protection part. I plan to use the ADM660 to invert the 5V Vcc from the Arduino, and then use the LM137 negative voltage regulator to produce a negative current of 100 mA, which would pass through the sensor to ground, while I measure the potential drop across it. Since my sensor has an area of 250 mm^2, this would produce a current density of 400 A/m^2.

Is this a feasible way to approach this? Below is a diagram of the circuit.


texts: Find the first-order transfer function from a measured step response data

texts:
In a school experiment, we had to measure an output voltage from an IC. We gathered the data with respect to time. Now we have to find the transfer function given the output data.

I think the whole experiment was treated as a first order open loop system. Now we have to find the transfer function that drove this step response output.

I searched around to find a few equations but still finding that this is a bit hard and requires estimation? Any hints onto how I can do this?


texts: Control 12V DC via MOSFET and normal transistor

texts: I made this schema and I want to ask, how transistor control MOSFET. What that s8050 transistor do with the IRFZ44N MOSFET. Please, help.


texts:
I'm still just beginning my adventure into electronics and IC chips and datasheets have me confused so I'm going to ask a series of beginner questions will help me and hopefully others as well.

There are many different IC and IC manufactures out there. Specifically for the 74 line, are these chips standard across the different manufacturers? If not, what are generally the differences between them? Will it matter if I mix and match different ICs from different manufactures?

Datasheets, for some reason these tend to be horribly thought out and rather difficult for a beginner like me to decipher (I've noticed TI is notorious for this, giving abbreviations to all their pins without any explanation. What the heck is OE?). Is there a company (assuming that all chips are standard between different manufacturers) that provides clear and concise datasheets for all of the 74 IC chip line?


texts: Why we need gate drivers and how much they are important in power electronics applications

texts: Generally, there are low, high side, as well as half-bridge and full-bridge gate drivers, existing in the market. I am keen to learn the basics of all such gate drivers in view of power electronics applications. Does anybody can share a technical guide/link which can help me to understand various sort of gate drivers with their examples. I will be thankful.


texts: How to measure small, spiky amounts of current?

texts:
Let's assume I have a microcontroller with some amount of peripherals attached and would like to be able to make a reasonable estimate of battery life.  Because I might have it sleep at times, and various peripherals would be in differing states, my current consumption might vary between uA (in sleep mode) and some 10s of mA (when awake).

Now, I could attach a battery and let it run down and measure the time, but this makes it both time consuming and hard (and possibly expensive) to compare different approaches, both in the firmware and hardware.

I could place a multimeter in series, but even if it has data logging, that is at some interval and I'd have to interpolate, and could entirely miss variations smaller than the interval.  (Plus burden voltage and all that.)

If my device sleeps enough, the awake current becomes somewhat negligible, but that might require a 1000:1 ratio of sleep time to awake time, so that's not likely on all designs.

Is there some device that integrates current over time at very small amounts (e.g., not the Kill-a-watt outlet meter)?  Basically I'm interested to know that "over the last hour, 20mAh were consumed".  Bonus points if I can get precision current measurements at any given time, to compare awake and asleep current consumption.


texts: Do two active high signals cancel each other?

texts:
A tp4056's temp pin is pulled HIGH, so it disables the chip. I accidentally fed a high signal into that same pin and it enabled the chip again!, which has to mean the signal went LOW. Are these two high signals cancelling each other? or is something else happening?
Answer: So I figured it out. First of all HIGH HIGH != LOW(its not math). Secondly, the pull-up is not at fault either. My signal when HIGH is 3.60v and when LOW is 1.23v, also my Vin is 4.73v (laptop). As the datasheet mentions, "If TEMP pin’s voltage is below 45% or above 80% of supply voltage VIN". 1.23 of 4.73 is 26% (which is below 45%, so the chip turns off) and 3.60 of 4.73 is 76%~ (which is just ever so slightly below the 80% threshold) that's why when signal is HIGH the chip remains on.


texts: What is the peak - peak voltage of 15mV rms white noise?

texts:
I've been experimenting with zener diode based noise sources.  I have such a source for which I want to determine the peak to peak noise voltage.  I've measured the noise with my trusty multimeter and it's approximately 15 mV which I believe is RMS.  The noise from these things is white.

So how can I obtain the peak to peak voltage, as I don't have an oscilloscope?  I think that it should be possible to calculate it from the RMS voltage and some statistics knowledge.  My multimeter is a digital Maplin Precision Gold (M-5010EC) from 1989.  The specification booklet says that it has a frequency range for AC measurements of 45 Hz – 500 Hz.  This is calibrated for a sine wave of course and not a white waveform.  Is that enough to obtain Vp-p?


texts: Are there any disturbances caused by wire of socket which not being used?

texts:
Let's say there external wiring that lead to AC power socket. Are there any electromagnetic field or something from the wire if the socket isn't used at the moment (nothing plugged in).
What if Internet cable (conventional CAT-5) would go near it?


texts: I want to replace a car dash cam battery with a capacitor

texts: My car dash cam (G1W) has a weak battery. When it dies the camera will not function at all. I have already replaced it once. The original battery was 200ma, but I found a 320ma one that would fit. It lasted about the same as the original - a year. The newer models (G1W-C) of the camera have a capacitor as original equipment, but I can't get any information from the Chinese manufacturer(s) except that it's a super capacitor. How do I calculate the necessary capacity? It only powers the camera for about 10 seconds so that it can save the recording before the camera shuts down.


texts: Having hard time to identify feedback types

texts:
update: I have read similar questions on ee.se, they helped a bit, but it is still hard to understand the type for example in the question in figure. Maybe, you can just explain specially the question below.

Series-shunt, shunt-shunt, current mixing, voltage sampling,... All these keywords became a total mess in my head. I cannot find a logical way of how to categorize those feedback types. The picture is just for an example, I would be appreciated if anyone comes up with a neat way to identify the feedback types and when it is sampled or mixed.


texts:
I only need help with part C). What I've done for part B) is square the wave, which makes Vpeak->V^2peak and the waveform in the negative region(under the period axis) become positive AND squared(like the waveform from 3T to 5T). I know Vpk=sqrt(2)Vrms, but that, of course, won't give maximum marks. So I equaled Vrms=sqrt(1/8T(total period) times the areas under the waveform graphs)=V/(sqrt(2))=140(sqrt(2))=198V

C) wants us to to find the pk Voltage to get the same 140V rms value, which is again 198V. My question is: How do we find the area under the graph?. We square the wave as before, obtaining the negative cycle as a squared positive one. I see we have 2 flipped parabolas. I think we can solve this using a definite integral, but that's where I get stuck and can't get the 198V answer.


texts: Small lathe induction motor - off-grid alternatives to capacitor start or modifying SP PH for capacitor

texts:
(UPDATE 19/09/18)
I have experimented retrospectively adding capacitors in series with the (centrifugally switched and originally capacitorless) start winding of the split-phase induction motor fitted to the small lathe. Testing it on the noisy 5kVA diesel genny revealed about 8A instantaneous start current with no capacitor. This reduces to 5.6A with 14uF and 3.9A with 47uF. There is no appreciable increase in time taken to reach operating speed; it is still quite instantaneous so it's not like it's lingering on start for too long causing mischief. The running current is 2.6A. This now runs on the smaller generator as required although it still causes a bit of strain on starting. It would be nice to tweak it one step further with a higher capacitor. Tests with no pulley belt fitted.

I have available a 100uF and 200uF capacitor to take the test further but we are approaching the run current anyway. Does anyone forsee any adverse effects on machine longevity with such a modification? Thank You.

(UPDATE 15/09/18: I was mistaken - Lathe motor is SP PH and looks like no capacitor)

I have removed the lathe motor and thought I'd check for the correct function of the centrifugal switch of the original motor now that's easy to get to. The centrifugal switch works fine and is used to cut out a second parallel winding once the RPM is high enough. The diagram in the cover describes an alternative connection for the start winding for opposite rotation. I do not find a capacitor anywhere obvious. The plate is stamped (WDG) SP PH so do I presume split phase and not capacitor? A very similar (but higher output) capacitor version from the same Hoover motor family is shown in https://www.youtube.com/watch?v=esRAVdc1drI but that is stamped something like CAP ST and the type stamp is different. Does this change the state of play? Can one add a capacitor to my SP PH to achieve softer starting? [230V (UK), 2.6 Amp, 1425 RPM, 1/4 HP, Rating: Continuous, 50Hz. This is manufactured at Cambuslang, Scotland.] Thank You

[230V ac, single phase, off-grid, UK]

I have a pillar drill and small lathe both with 1/4HP motors which are plated at 2.6 amp. They are both capacitor type - one has the capacitor piggy back on the outside and the other is inside the free end bearing cover. I am running a 1KW inverter generator which is nice and clean. (The light-dimmer switch on the cylinder vacuum cleaner for a forge blower can crawl at a snails pace if I need it to and the variable speed jigsaw works fine.) When I use the Pillar drill (belt-driving the chuck spindle) it starts fine after the expected momentary surge. When I try to start the lathe (with all belts disconnected so only motor inertia) it overloads the genny.

So I am trying to work out why they are the same capacity but different electrical loads and how to reduce the start requirement of the lathe. I made a simple experimental arrangement of a single gang and double gang mains sockets in series. The lathe is plugged into the single. The  double carries a (fused!) "shorting" plug in one socket and any resistive load in the other socket. The current for the lathe therefore has to also pass through whichever of the other two plugs is switched on. The plan was to start on the resistor then short the resistor to run. So I took a few resistance measurements and tried a few different things like a hair drier and electric kettle for a resistor but had no luck. The hair dryer at 66ohm holds it back so it only flinches and the 26ohm kettle is not enough. Maybe my steps for splitting the voltage are too coarse.

Is this a correct approach? I don't mind the inconvenience of the extra switch.

Might a light-dimmer switch (I'd need to source a higher current one) work on an induction motor? The requirement is only for soft starting and NOT run speed control.

There are many budget motor speed controllers. What are the differences between these and a light dimmer switch?

I can get the motor plate details and try to find out any spec differences if that helps.

Thank you.


texts: Can someone explain interference alignment in layman terms

texts:
I am reading about current research going in wireless communications. I came across the term  interference alignment for MIMO systems.

Can someone explain what is interference alignment?


texts: How does the LM317 bypass adjustment terminal reduce ripple amplification?

texts:
According to the LM317 datasheet it says that the adjustment terminal must be bypassed to ground to improve ripple rejection, so that the ripples aren't amplified.

Could anyone explain how this is possible in detail?

I have done quite a lot of research but I don't understand how the adjustment terminal and ripple rejection are linked.


texts:
I'm using a Tektronix TDS 1002B oscilloscope.
I was investigating some glitch issues on pulses/square-waves and decided to save the time-series data to a USB drive in CSV file format to plot in MATLAB.

Input to the scope is a square-wave or pulse.

When I set the scope's Acquire feature to 'Peak Detect' setting, and observe the signal on the scope's screen live I only see over-shootings at the rising edges but the pulse seems it has no glitches.
But then I save this signal data(using Save feature) to a USB drive in CSV file format to plot in MATLAB.

In the following example, the input to the scope is a 50Hz 4Vpp square-wave.

When I set the Acquire to 'Peak Detect' and saved the data in CSV format, here is what I plot in MATLAB:

And here in the zoomed view I see glitch on each falling edge:

On the other hand, when I set the Acquire to 'Sample' and saved the data in CSV format, here is what I plot in MATLAB:

As you see the square-wave is clean and free of glitches:

I tested this measurement with different inputs I mean different function generators and pulse outputting devices at various frequencies.
But I always see same type of glitch always on the falling edges when the Acquire is set to 'Peak Detect' and saved as in CSV format.

I made the same test with a chinese scope Siglent SDS1102CML and when I saved the data in Peak Detect mode I don't see any glitches.

What would the reason be for those glitches after each falling edge. Is that an oscilloccope error?

Edit:

Following PlasmaHH's advice I checked the measuremtns with more horizontal settings. When I decrease the division enough, at some point the saved data for falling edges are clean, glitches disappear.

When the horizontal is set to 50us here is the data saved:

And here is the zoomed view of a glitchy falling edge:

When the horizontal is set to 5us there is no glitch, here is the data saved:

When the horizontal is set to 250ns there is no glitch, here is the data saved:

Edit 2

Horizontal is set to 5ms per division. The input is 50Hz square wave.

Here are the results:

Each falling edge has glitch. And here is the zoomed view:

And here below is the data from CSV file where the first glitch occurs:

t = [-0.01006
-0.01004
-0.01002
-0.01
-0.00998
-0.00996
-0.00994
-0.00992
-0.0099
-0.00988
-0.00986
-0.00984
];

V= [2.76
2.76
2.8
-2.72
2.76
-2.76
-2.68
-2.76
-2.68
-2.76
-2.68
-2.76
]

plot(t,V)


texts: lm317 vs lm1117 for 5v to 3.3v in circuit

texts:
I am wondering if I should use an LM317 or LM1117 for a 5v circuit that needs 3.3v for a sub-circuit far (20ft) from the power supply.

Any help would be greatly appreciated.  Thanks in advance.