texts: Add tilt switch to this photodiode circuit

texts:
I'd like to take this phototransistor switch circuit:

And add a tilt-ball or similar switch in series. That switch needs to be heavily debounced, so that it stays "switched" more or less for several seconds after the last contact, but does not need a sensitivity adjusting trimpot which the phototransistor is still going to need.

Here's my attempt:

The desired behavior is that the leds should light when it's dark out and the tilt switch has been jiggled around recently.

I don't know how to simulate either the phototransistor or the tilt switch and I don't have the parts on hand. Does my circuit above seem reasonable?

UPDATE:

I hadn't realized that the transistor pair is inverting, so I think the way I have it above if there's no light and there's motion it will shut off. If there's light or no motion it will remain on.

What I want is if there's light and motion turn on the load, if there's either light or no motion fade out & shut off the load.

Also this is intended to be battery operated so it's better if it consumes as little power as possible when off. To me this seems a little challenging because you might naturally want the phototransistor pulling down a pull up which is always going to waste a little current.

UPDATE 2:

This seems pretty close to what I want. Horizontal switch represents the spring switch, the vertical switch represents the phototransistor.

Only question is how to tune the phototransistor's sensitivity...


texts: Using different termination types on CAN bus

texts: Is it possible to terminate one end of a CAN bus using Standard termination (single 120 ohm resistor across CANH and CANL) and the other end using Split termination (two 60 ohm in series with a capacitor between their joint and ground)?


texts: TMP36 reading not steady if circuit has more elements

texts:
I have a TMP36 connected to an analog pin of an Atmega328p-pu on a breadboard (with Arduino bootloader), everything is powered w/+5V from an Arduino Uno R3 (which is used as a programmer).

The reading I get are steady, but when I connect a piezo buzzer to a pwm pin, the temperature reading jumps higher, when I disconnect the piezo jumper wire, the temperature drops down again.

What is going on? I suspect that the current is not sufficient for the atmega chip and the buzzer and the tmp36, but I don't know whether that's true... how would you solve this?


texts: Using l6506 with digital pot to vary force output of stepper

texts: I want to precisely control the amount of force being applied to a component - my plan is to drive my stepper linear actuator with the absolute minimum current to make it move, until it stalls out against my component. Then I would gradually up the current to the stepper until it was able to move another step (measuring the force being applied). I was thinking of doing this using an l6506 with a digital pot as the Rsense. Will this plan work? Many thanks!


texts: How to measure FM deviation for pilot signal?

texts:
I'm trying to calibrate my FM signal generator, but don't have the required FM detector.  The instructions say:

Turn pilot ON, comp OFF
Set pilot to 10% deviation
Verify detector says 7.5kHz, or adjust R102

If I use my HP E4406A connected to the VSA software, the second plot is supposed to show the FM deviation.  Why is the resolution so bad?  It seems to work ok when checking with a 1kHz tone at 67.5kHz deviation.

Edit: This is what the signal looks like with FM mono and 1kHz tone, comp only


texts:
I need a solution for listening to music from 2 headphones/earphones on a single mobile phone. Using a speaker could be an option buy my girlfriend wants it this way. Anyway, while looking for a solution, the only thing I could really find is DIY videos of people making a cable like this 3.5mm jack signal splitter. I'm worried this could affect maximum volume, or damage the earphones, maybe even my phone's audio output, as it would put two inputs in parallel, thus making the current larger. For this reason I've been looking for some low-power circuit that i could power with a smaller battery pack, probably with an amplifier with two outputs or something. I've been unable to find any that suit this criteria. I did find this circuit which seems like it could be what I need, but I'm not sure about how portable it is, considering it would probably need a separate power supply or something, since it works at 20-35V.

I would like to know are those 3.5mm signal splitters reliable and safe for both phone and headphones, and if not, I would appreciate if someone could point me to the right direction regarding picking a custom circuit and assembling it. I would very much appreciate if you were to provide me with a suitable circuit diagram.

I have relatively limited knowledge of electronics, one that's mostly theoretical so I would warmly welcome any corrections you make regarding stuff that I said in the question. Same goes for my English, since it's not my primary language.


texts: Syntax error near variable and range in VHDL

texts:
I learnt Java last year and started to learn VHDL and implementation on BASYS3 this year. I am just trying to display numbers on the seven segment starting from 0 and each time a push button is pushed the number will increase. I am familiar with the input and output declarations but I was not able to declare my integer variable as follows in VHDL vivado;

architecture Behavioral of top_module is
begin
shared variable total_foul : integer range 0 to 5;
total_foul := 0;

It keeps saying that there is a syntax error near variable and range which I couldn't find out. Also I tried to write the code for seven segment in case statements as follows;

 begin
        case total_foul is
        when 1 => LED <= "1001111"; -- "1"
        when 2 => LED <= "0010010"; -- "2"
        when 3 => LED <= "0000110"; -- "3"
        when 4 => LED <= "1001100"; -- "4"
        when 5 => LED <= "0100100"; -- "5"
        when others => LED <= "0000001"; -- "0"

But this also states that there is a syntax error near when.

The overall code for now is;

entity top_module is
    Port ( increase : in STD_LOGIC;
           decrease : in STD_LOGIC;
           foul : in STD_LOGIC;
           anode : out STD_LOGIC_VECTOR (3 downto 0);
           LED : out STD_LOGIC_VECTOR (6 downto 0));

end top_module;

architecture Behavioral of top_module is
begin
anode <= "1111";
shared variable total_foul : integer range 0 to 5;
total_foul := 0;
begin
if foul = '1'  then
    if increase = '1' and decrease = '0' then
        total_foul := total_foul + 1;
    elsif decrease = '1' and increase = '0' then
        total_foul := total_foul - 1;
    end if;
    begin
        case total_foul is
        when 1 => LED <= "1001111"; -- "1"
        when 2 => LED <= "0010010"; -- "2"
        when 3 => LED <= "0000110"; -- "3"
        when 4 => LED <= "1001100"; -- "4"
        when 5 => LED <= "0100100"; -- "5"
        when others => LED <= "0000001"; -- "0"

end Behavioral;

Thanks for everyone in advance.


texts: Confused about Kirchoff's voltage law and voltage drops

texts:
I am a beginner student in electricity and magnetism. I have troubles understanding the physics behind it and so have found myself stuck with this:

Kirchoff's voltage law, as I understand it, says that the electromotive force (voltage) that drives the current is equal to the total losses of voltage over the current.

How can this happen?

If we have a battery driving the current, isn't the voltage on its terminals always the same?

If the voltage drops over a resistor, will the current after it be moved by lesser force (smaller voltage)?

And most of all, doesn't that mean that the voltage after all drops will be 0, so what moves the current anyway?

I have no knowledge of AC, so this is DC related.

I am so sorry if this question is badly formatted or put together, but I couldn't word it differently.


texts: Struggling to find a sensor to detect water depth that suits my purposes

texts:
I am new to finding sensors and not familiar with good resources to find what I need, so the answer may be simple.

I have a small tank that I am controlling the water level in. However, the depth only varies between 0-2 inches. Most sensors I have found don't have fine enough resolution to find measure changes in water level in this small of a tank. Any suggestions would be a big help.


texts:
I’m (for fun and hobby projects) making a DIY reflow oven (box, not conveyor) based on resisting heating elements and convection.

I initially used a base to hold PCB made of steel wire, but that introduces uneven thermal spread.

I have an option to make new base either using steel or aluminum plate with perforations.

My question is which material would be more suitable for this purpose?

I guess it is whether thermal conductivity of the plate should be higher or lower but I cannot find the right answer to that somehow.


texts:
How is it possible that in scenario 1 resistor R1 converts 5V of energy to heat and in scenario 2 the same resistor R1 converts 2.5V of energy to heat?

The resistor R1 in both scenarios are exacly the same, I don't seem to grasp what happens on the physical level to the electrons how they "know" when to dump all their energy at once in resistor R1 in scenario 1 or to divide the energy they have proportionally over the resistors R1 and R2 in scenario 2.

I have read an explenation here, but it's still not clear. How is it possible that the voltage is different at point A going through the same amount of resistance? I would expect a linear relation between voltage and resistance.

Could someone explain what physically happens that causes this?

simulate this circuit – Schematic created using CircuitLab

Edit

Is my understanding right? According to here

The resistance drops liniar along the path.

In scenario 1 at the start of R1 the resistance the current encounters is 100\$\Omega\$ and at the end of R1 it encounters 0\$\Omega\$.

In scenario 2 at the start of R1 the resistance the current encounters is 200\$\Omega\$ and at the end of R1 it encounters 100\$\Omega\$.

If this is true, why does point A in scenario 2 have more volt left if it has encountered a higher resistance of 200\$\Omega\$ at the beginning opposed to scenario 1 where it encountered 100\$\Omega\$ at the beginning?


texts:
I want to use MIC29302 as regulator in SIM800L circuit.

In the suggested circuit in the datasheet there is a 100 µF capacitor before the regulator and a 330 µF capacitor after the regulator, but there is no information about the voltage of these capacitors in it.

How should I choose the appropriate capacitors?


texts: LEDs inside of solar-powered calculators

texts:
Why do a lot of solar-powered calculators contain red or infrared LEDs that are hidden from the user? So far I have only seen this in Texas Instruments calculators.

Here are some examples of this in Texas Instruments calculators, taken from user-contributed guides on iFixit:

Older TI calculators, from datamath.org:

Here's a newer TI-106II, with what appears to be an infrared LED:

I think I first saw this in a Youtube video from either EEVBlog or bigclivedotcom and I remember whoever doing the video was confused as to why there was an LED inside. If anyone has seen this video and could provide the URL that would be good.

Any ideas?


texts:
I tried to make a microphone (condenser microphone) amplifier that powers a 0.5W 8 ohm speaker using the LM386, however I have been having random noise issues.

Whenever the power is connected, the speaker will output a random high pitch frequency and turning the potentiometer will cause the pitch to raise or lower. Sometimes when I tap the microphone there is a break in sound, however, if I expose the microphone to audio like music nothing happens and the random high pitch noise continues to play (note that this also happens if the microphone is not exposed to any sound.) I am thinking that it may have to do with the fact I am using a breadboard. Do you have any ideas?

Here is the circuit I am using:


texts: New multimeter always shows a resistance of 1

texts:
I'm having the same problem as this person - no matter the setting, my  multimeter always shows a resistance of 1. I tried touching the probes together - still 1.

Is my multimeter faulty? Or am I doing something wrong? Help!


texts: Soldering iron for hakko t12 tips on 12v

texts:
I considered getting those clone hakko t12 tip compatible soldering iron.

this is the tutorial I'm following:

  https://www.instructables.com/id/DIY-Hakko-T12-Compatible-Soldering-Station/

so based from the title, I know you know what I am doing so i'll just get to the point already.

I'm building those soldering iron kit but I don't have the 24v power supply. I  have however a 12v power supply.

In theory, the soldering iron will still heat up but slower. I'm fine with slow so will it function or will the circuitry on the controller explode or something. Even if it is slow, As long as it is functioning, I'm fine with it.

This is what my soldering iron looks like:

  https://www.ebay.com/itm/Digital-Soldering-Iron-Station-Temperature-Controller-Kits-For-HAKKO-T12-Handle/112555080925?hash=item1a34ce3cdd:m:mhF39lZBeOxALWWO8tNREIQ


texts: Why is feeder network so long and other questions?

texts:
I have an mBed Lora 915Mhz shield I attached to a Raspberry Pi. I had some questions about the feeder network. In the attached schematic. Why isn't a simple cap/inductor pair sufficient for an impedance match in this case? Also, they use a capacitor and inductor in series. Is this a resonant band pass filter? Then why is the resonant frequency 1.4Ghz (22pF/5.6nH) and not 915Mhz? I checked the BOM and half the components are DNP. I attached a spice simulation with the actual component values.

Here is the simulation with the resistor removed:


texts:
I am trying to understand the following situation:
I have an MCU (STM35L152RE), in which I am encoding digital data into PIE encoded data. Then I want to communicate this PIE encoded data with transceiver IC (S2LP) for modulation and transmit it over the air for the other receiver.
Is there any issue to communicate this PIE encoded data with transceiver IC via SPI communication? Will there be an issue with clock synchronization?


texts: Time Domain Measurements with Vector Analyzer

texts:
In my university I have done some time domain measurements with a VNA (by using the transform operation of the instrument). Precisely, I have selected the measurement of the real part of S11 while leaving port 1 open (so port 1 of the device is connected to a floating coaxial cable), and I selected the Step Response Mode.

The result of my measurement is this one (a step signal has been sent by the VNA, and a step signal I have obtained for the real part of S11)::

Now I have 3 questions:

1) What is exactly S11 measured by the instrument in that situation? During the lecture I have been told it is the reflection coefficient of the DUT - which in this case is a floating coaxial cable - , but in theory S11 coincides with the input reflection coefficient only if the other port is matched (and in this case it is open). So what does it represent?

2) In that situation the input reflection coefficient of the floating coaxial cable shoud have absolute value equal to 1 (total reflection), and real and imaginary part function of the position on the coaxial cable (and so of time of moving along it). My question is: why is the real part of S11 a step, like the signal sent by the VNA during the analysis?

3) S11 depends on t with a precise mathematical relationship. Why does its curve depend on the mode we select on the instrument (low pass step/low pass pulse)?


texts:
I am presented with the following problem:

I have 256 12-bit words.  Each of them are initialized to the same (arbitrary) value.  At any given time, a subset of these words will either increase or decrease by the same quantity.  For example, 56 of the 256 words at one FPGA clock cycle may increase/decrease by n, while the 200 others remain unchanged.  Of these 56, each one of them experiences the same amount of addition or subtraction.

So, into this system, there are 512 bits which enable control over the 256 words. There is also an additional input, the incrementer, inc, which is common to all the words.  If the control bits of a single word, word1, are 01, then word1 adds inc to itself.  If the control bits are 10, word1 subtracts inc from itself.  If the control bits are 00, then word1 remains the same.

Knowing that all 256 words start in the same, arbitrarily defined state, and that they change predictably, as determined by their control signals and inc, I am wondering if there is a hardware-efficient means to sort all 256 words on-the-fly.

I hope my question makes sense, and please let me know if I can provide further information of my question statement. Thank you!


texts:
Let's say I have an audio oscillator, which a resistor varies the tone.

I have 5 different voltage sources, each representing a tone.

How can I control the tone (vary the resistance) depending on which voltage source is on?


texts:
I am repairing a battery charger that uses two power supplies. TH20594 (couldn't find any info on that either) controls the primary PSU, while the mysterious chip controls the bootstrap/standby supply (aux winding on the smaller transformer provides power to the TH20594). It does not work, but I cannot find any information about the chip.

The chip is a really small 6 pin SMD package (TSSOP-6?) and is marked as "67A".

Here is part of the schematic of a power supply (cannot guarantee the accuracy though).

Anyone knows what chip it is and where to find a datasheet for it (as well as the TH20594)?

67A:

TH20594:

EDIT: It is definitely "67A".


texts:
I read that the frequencies over which FM signals can be transmitted is limited between 88 MHz and 108 MHz. Why is it confined to a particular range and why specifically to this (88 MHz to 108 MHz) range?

Besides FM, other communication techniques have their own band of frequencies. What decides their band of frequencies.


texts: What is the resistance of an electric arc between two graphite electrodes?

texts: I want to make a mini arc furnace just for fun. I have two 4mm diameter graphite electrodes from an AA battery. I could calculate the loss of heat by radiation, but I dont know the resistance of the arc and I need it to calculate the windings of the transformer that will supply it since I dont have a power source with more than 10 A.


texts: How do I add a bipolar stepper motor to this circuit?

texts: I have just started electronics at school and cannot find any tutorials on how to do this. I am creating a circuit that when the light intensity increases a bipolar stepper motor will step clockwise for with 5 second intervals for 30 seconds then do the same but anti clockwise. I know how to program this, but not how to connect it to my circuit. How would I connect this to my circuit with the use of h bridges. I am using circuit wizard. circuit diagram btw, this is just a circuit, I am not planning on making this I would just like to know for further use. I would like to connect it to Q4 (no output is there currently )


texts: CRC generator polynomial for data flash memory storage

texts: I have been facing a problem how to implement embedded software configuration parameters management system. It means how to implement a software module which will be responsible for storage of for example PI controller gains or some compare levels of protections into the external flash memory and retrieving them from the external flash memory. One of the questions regarding this problem is what generator polynomial I should use for CRC calculation. The parameters will be without exception 16 bits values. Is the CRC16 polynomial i.e. \$x^{16} + x^{15} + x^{2} + 1\$ good choice for that? Thanks for any ideas.


texts: What is this red mark that resembles a net bridge in circuit diagrams?

texts:
What does the red mark on this schematic mean? I think it's not a net bridge.

The corresponding image was taken from the IO board of raspberry pi compute module 3.

Link to the diagram: https://www.waveshare.com/w/upload/7/75/CM3-board.pdf

İmage:

Best regards and thanks


texts: Shorthand syntax for components in series

texts: When doing circuit analysis, you can represent the mathematical operation of two components in parallel with the symbol "||".  Is there a similar way to represent the mathematical operation of components in series?  I'm doing my Circuit analysis homework and we are beginning to use source transformations.  I don't want to write out a complete sentence for "This source is in series with this transistor" Every time I do a transformation, lol. Thanks for your time.


texts: Ac current source(1-10mA) with help of 5V dc battery

texts:
I have been working on a project in which I have been using an Howland AC current source (it has an AC voltage source in it) as a current source.
But as an upgrade, I need a current of same sort which can be made using a 5VDC source (battery) and other components.

Objective is to make the equipment portable. Load is variable, so constant current over a wide range of output load is preferred.


texts: What is the use of this pin in my AC to AC converter

texts: I am using a 9V AC converter for a digitech product. But I notice that there is a pin in a socket kind of thing in the adapter. What is the use of this pin?


texts: Design of an Automatic Gain Control Using a JFET

texts:
simulate this circuit – Schematic created using CircuitLab

I have implemented the above circuit which is supposed to amplify a negative 200kHz sinusoid to constant amplitude even if the amplitude is varied. The constant amplitude is adjusted according to the reference.

Am I missing something here? Since the amplitude of Vout still varies with the input amplitude , but doesn't vary when the Reference voltage is adjusted.

However I noticed that the overall gain of the VCA is reduced as the amplitude of the input is decreased. This remains constant if the feedback is removed.


texts: How is switching frequency related to baud rate?

texts:
Within the datasheet of AM26LV32IDR, it is advertised that "Switching frequency is up to 32MHz", but there is no baud rate specified.

If we consider t_rising and t_falling, we can calculate that a square-like wave can be obtained at 1 / (4*5ns) = 50MHz:

Moreover, the test setup had been run at 10MHz:

So where does the 32 MHz come from? How can I calculate the maximum frequency (=kbps) of input data signal? What would be the maximum frequency of input 50%-duty-clock signal?


texts: Does a DC Current charge a DISCHARGED capacitor and does the current pass throug the capacitor?

texts:
simulate this circuit – Schematic created using CircuitLab
Like I said, does a DC Current charge a discharged capacitor and does the current pass through the capacitor and feed a resistor? (The values in the given schematic are not real.)


texts: What are the X symbols in a board layout file?

texts: I'm viewing a board layout file in Mentor PADS and there are X symbols all over the board. I'm not sure what they indicate, but they don't seem to be a part of any layer and I can't hide them. I'd at least like to know what they are, but also knowing how to disable them in this viewer would be helpful as well.


texts: Best way to control power with MCU gpio pin

texts:
This is my circuit. An MCU gpio pin should control the power of another IC. Because the component requires more current than the gpio pin can drive, an N-Channel MOSFET is used. This is IC has no ENABLE/SHUTDOWN/RESET pin. VCC may be different from MCU VCC. However in this configuration a virtual ground for that component is created because of the RDS_ON resistance of the MOSFET that causes a voltage drop.

A certain number of question arises:

Is this a good way? Is there a better way?
In order not to left components ground floating (if the MOSFET is not conducting) is this 100K pull-up resistor required or is it even allowed? Is a floating ground a problem in most situations?

Update: New circuit based on Michael's reply Unfortunately wrong.

If I understand, the circuit can even be simplified by using one logic P-Channel MOSFET like following circuit (assuming SSM3J328R P-Channel MOSFET):


texts:
When designing a PCB, I understand that it's often good to design the ground signals so that:

They follow the signal in reverse (make return path be same as out path.)
They do not daisy chain, but instead connect back in a "star."
They minimize the return path length.
They have the same trace width as the signal.

These are sometimes contrary to each other, but that's OK -- if it was always straightforward, it wouldn't be called "engineering" :-)

Here's what I don't understand, though: I also see the recommendation to do a polygon pour for the GND net, on both sides of the PCB.
I mainly work with through-hole components on two-sided boards at <= 20 MHz frequencies; 1 oz copper; FR-4; 1.6mm thickness; ENIG.

So, once I pour the copper, the traces I designed for the four original points kind-of go out the window, right? If I know I'll have ground pours, do I not need to pay attention to the "no daisy-chaining of ground" anymore?

Also, I try to route most signals on the top layer, and keep the ground layer somewhat less crowded; is this actually worth anything, or is a snake pit of traces equally distributed on both sides about just as good?

And would there be any benefit to pouring VCC instead of GND on the top layer? Especially if that layer is pretty dense with signal traces anyway?


texts: How to properly connect to a RN-171 Roving Network's WiFly module?

texts:
I have this WiFly device and I can't seem to make it work correctly. I've connected both available interfaces (UART and SPI) to my microcontroller (STM32F107). For now, just the UART interface would make me happy.

From the three boards mounted, in only one of them the RN-171 would reply to the commands sent through the UART interface. The other two would just remain mute.

I was suspecting that maybe I was activating the SPI mode automatically, so I've putted the SPI associated pins at a state that will shut it down for this device (CS high, everything else low).

However, now even this board is not working anymore. Factory reset is not bringing it back either. I'm really confused.

Has anyone here worked with this device before? What am I missing here?

Thanks in advance.


texts: Photocell and Relay switch not working properly

texts:
I am trying to build a simple circuit to switch on and off my garden lights according to the brightness level. More to the point, I'd like the lights to turn on when it's dark and off in the morning.

The solution I've come up with is the following, but somehow it is not working properly.

I use a 12V battery, in conjunction with a 12V relay switch, a 12V 4.5W LED lamp (in the picture it is shown as a single LED) and a photocell.

According to the specs, the resistance of the photocell should be 10K Ohms during the day and around 600K Ohms at night. Below are the datasheets

Relay: https://www.ghielectronics.com/downloads/man/20084141716341001RelayX1.pdf

Photocell (Photoresistor) https://learn.adafruit.com/downloads/pdf/photocells.pdf

Is the circuit ok? What am I doing wrong?
Thank you


texts:
I checked the wall near a plug with a Non Contact Voltage tester, and it showed electricity is present in a 3 meter diameter from the plug, on the wall. I think the wire inside has some contact with the wall. I was wondering if anybody knows for sure that if that would be the case, does it mean that I have a current drain? And I am paying for the electricity that I haven't used.

Thanks.


texts:
How It's possible to add a LED to a line that it's debounced (switch) with an RC circuit. If I place 2 LED, one on ground and one on VCC to know button position. Will they remove my charge/discharge rate of Capacitor since they have a low R load?

/* EDIT */

Of course with schematic is easier.

simulate this circuit – Schematic created using CircuitLab

Switch closed, D2 ON and D1 OFF
Switch open, D2 OFF and D1 ON

With debouncing on Input

This schematics is wrong, how can I correctly set it up?

/* EDIT 2 */

It's a reference for a Micro input.


texts:
I need to transfer data over about 20m from a DS18B20 to a Arduino board, I was wondering if I could use the much cheaper CCA cable?

Also can you please inform me in which cases must I go for the CU cable. The differences between the two types are obvious but I still do not know in which cases I should use CU type. I have found some information in which is stated that CU, due to it's lower resistance, is required in case the load is draining significant current. What about frequency?


texts: Resistance of a MOSFET in saturation mode

texts: I have been studying MOSFETs and have a question regarding saturation mode. To my understanding, the drain current is constant in saturation mode. Does this mean that the drain-source resistance increases with drain-source voltage (to keep drain current constant)? If so, does this mean that the voltage drop across the transistor increases with drain-source voltage? For instance, if I were applying a high voltage (say 20V, and the transistor was saturated at 10V) across the drain-source and had a load in series with the transistor, would I get a voltage drop much less than 20V across the load (because of the high resistance of the transistor)? I am not sure if my interpretation is too "ohmic". Any help/resources would be appreciated. Thank you!


texts: 267 3MW wind turbines can produce 960MW?

texts:
WINDFARM PROPOSAL

In the proposal above, it states that 267 3MW wind turbines are used to provide 960MW. but using a very simple calculation: 267 * 3MW=801MW.

So how is it that the windfarm is designed to produced 960MW?

wind turbines used are Vestas V112 Wind Turbine Generators 3MW


texts: Is a buck converter necessary for a 18V drill conversion? (NiCad to Li-Ion)

texts:
Im currently planning out my (first) conversion of an old 18V drill with dead NiCad cells to 18650 Li-Ion. I have enough cells that should support the high discharge rates and I'm putting them into a 5S configuration.
My question: should I use a buck/boost coverter to keep the voltage steady at 18V or will the motor (most likely) be fine with the voltage range of fully charged and discharged Li-Ion cells (roughly 15 - 20V)?
If possible, would a 5S2P configuration be preferrable, to "spread out" the current over 2 cells? Would a different BMS be required for that?


texts: When tapping single phase power from a 3 phase service, how much power can safely be drawn?

texts:
I'm setting up a piece of lab equipment that needs 220v-260v to operate properly. The room it's located in has a a 480v 3-Phase service, in the form of a California Standard 50Amp twist-lock connector. It has a large outer ground terminal, and what  I assume are 3 "hot" terminals.

The device in question had a 3-prong 240v plug, which I have removed. One Ground, one Hot, one Neutral.

Based on my reading, I believe I can connect the device by wiring Neutral and Ground on the device to the service Ground, and Hot to one of the 3-phase leads. Each lead should be about 480/sqrt(3) volts relative to ground, which is correct for the device.

I've been told that using only one phase of the 3-phase power is not something the transformer is designed for, and so the power factor will not be good, and the full 50amps will not be available. Needless to say, I need about 10 amps, so I assume this won't be a problem.

Is this feasible? Is there anything i'm missing?

And don't worry, I'll someone look at the cable after I set it up. I'm an EE student so I thought I would give it a try at least.


texts: Important Parameters to Check while Chosing a GSM/GPRS Antenna

texts:
what technical parameters decide the performance of a GSM/GPRS antenna? (excluding power consumption and size)

I have found out several antennas that have 3dBi gain. And I want to chose between them. Some are PCB antennas, some are external antennas and some are ceramic.

What other technical factors (polarisation pattern, VSWR etc) should I consider? And can someone please explain the combinational effect of such parameters?

P.S : Some technical terms given in antenna data sheets are very difficult to understand. But I am sort of certain that antenna performance may be not fully judged by dBi figure. Am I right to think a 2.5dBi antenna may be able to perform better than a 5 dBi antenna in a forest or harsh environments when such technical factors come into play?


texts: Raspbery PI GPIO output failing to control RGBW strip via N-FETs (always on 100%)

texts:
I'm trying to build a lighting system that will give me 24 hour control of some RGBW strips using a Raspbery PI Zero.

I'm a software guy, so I'm pretty new to the electronics beyond a bit of work on cars and wiring the odd plug/light fitting. There are a few tutorials for wiring RGB strips with PI and Arduinos and they're all pretty similar, using the GPIO to trigger Mosfets to provide the 12V needed for the strip.

I've been mainly following this tutorial here, but adding an extra Mosfet for the white LED pin.

Here's my schematic (yellow wires => white):

I used 4 IRLB8721PBF 30V, 62A N Channel MOSFETs, 5 meters of 12VDC 5050 rgbw strip (ebay special, not much data). The GPIO is connected to the gate, the RGBW strip channel is connected to the drain, and the 12V- to the source.

I also installed pigpiod on the PI using method 1.

When everything is up and running it lights up:

However, I'm finding it is always seems to be fully lit. When I try change the levels via the GPIO pins using commands like this (turn it off):

pigs p 17 0
pigs p 22 0
pigs p 24 0
pigs p 27 0

or this (make it red):

pigs p 17 255
pigs p 22 0
pigs p 24 0
pigs p 27 0

Basically nothing happens and it stays at 100% output on all channels.

My question: How should I approach debugging this issue? I've only got a cheapo multi-meter.

Also, I'd like to double check my understanding.

At first I thought Mosfets used the gate voltage to 'switch' the larger source/drain voltage. So when the output of the GPIO reaches a threshold, the mosfet switches 'on' and the 12V passes from source to drain.

I can't see how that would convert the (angalog?) raspberry PI signal from the GPIO to anything meaningful other than an ON or OFF 12V.

Is the Mosfet taking the gate voltage and amplifying the 3.5V to 12V proportionally? So 1.75V output (a value of 127) would produce 6V, and thus that channel would be 'half' brightness? (If it worked!)

Edit

I've wired just a single Mosfet up with a single colour on the RBG,

The center pin is to the RGB R channel.
The right pin is to 12V- (ground)

The RGB + is 12V+

Now, when I touch the left pin to 12V- (ground) it should turn off right? This is simulating LOW output (excuse the awful paint diagram):

Test 1 (should be off):

Test 2 (should be on):

What I get is a bit of a mess. It's flashing on and off. Sometimes it's consistently off, but often consistently quite-low. Then, suddenly it's ON full, then flickers.

It kind of turns off more often than not when the ground is to source, and on more often than off when ground to +12V (or +3.3/5V output on the PI, not GIPO), but it's all over the place. Often it doesn't go 'off' just consistently very low, but even then its acting as if there's a loose connection or something - even through I've tried soldiering all connections.

I can't think of anything that would cause this but dodgy Mossfet? I could have caused problems soldering the connection on.


texts: Measuring voltage drop across a 100 ohm resistor from an isolated power supply

texts:
I am new to this and i need help with a question I have in a circuit
I want to measure the voltage drop across the resistor RS1. The opamp is powered by a 5V supply rail. The 50VDC is coming from the same supply source but its isolated using a step up transformer and rectifier circuit. Now, the question is, where should the ground pin of the op-amp be connected? is it safe to connect it to the ground of the +50VDC rail or can I just connect to the battery ground(5v power rail source) which is isolated from the 50VDC rail


texts: Arduino Code - simple if, else statement?

texts:
Basically, I have two led lights connected to pin 2 (led 1) and pin 3 (led 2), and I want led 2 to light up every time led 1 lights up, and turn off every time led 1 turns off.

My code:

int led1=2;
int led2=3;

void setup()
{
    pinMode(led1, OUTPUT);
    pinMode(led2, OUTPUT);
}

void loop()
{
    if (digitalRead(led1 == HIGH))
    {
        digitalWrite(led2, HIGH);
    }
    else
    {
        digitalWrite(led2, LOW); //This line won't work.
    }
    digitalWrite(led1, HIGH);
    delay(5000);
    digitalWrite(led1, LOW);
    delay(3000);
}

So after I upload this code, led 2 lights up whenever led 1 lights up, but led 2 wont turn off when led 1 turns off.


texts: Negative Voltage Reference for Bipolar ADC

texts:
I am considering using ADS1258 - a bipolar ADC. It needs an external reference across REFP(+) and REFN(-). How do I generate precise -2.5V assuming I have +12V and -12V analog voltage rails? I can generate an approximate -2.5V using something like LM337 but I need something more accurate as that voltage is going to be used as a reference. A more precise way is to use a low input offset voltage opamp to invert a positive reference but that would still add some error.

What is the standard way to get good quality bipolar reference voltage in a circuit?


texts: Is it possible to create a computer without sequential circuits?

texts:
Do computers (or FSMs) absolutely need sequential logic, or can it be done theoretically without?

This seems impossible. Any proof of why it's not the case? (Showing that there can be no memory without sequential logic, and that FSMs need memory?)...

EDIT: I redefine computer to mean a Turing-complete system.


texts: Charge device and power other devices over the same USB port

texts:
I'm creating a raspberry pi based mobile device. It has a LiPo-battery and a lipo charger, which will power the raspberry pi. The device should have one usb port, over which the device can be charged from externally. Furthermore, I want to be able to connect e.g. a keyboard over the same port, which means that the usb port has to be able to power external devices. I have researched a lot about bidirectional usb power but I couldn't find anything which helped me. I guess this is normal behaviour for every smartphone out there, somehow related schematics and controllers for this seem hard to find. I will include a schematic of my project.

schematic so far (the bottom left corner is a save shutdown for the rpi)
Does anyone have suggestions on how to do this?


texts: high output impedance sensor with voltage output

texts:
I've to design an input stage for signal conditioning of a voltage signal coming from an high output impedance sensor.
The sensor output impedance is 100k, and the amplitude of the voltage signal is 0-5mV. The frequency of the signal is between 50-150 kHz.
I'd like to minimize the op-amp used in the circuit.
In terms of "circuit blocks" what architecture do you suggest?

I was thinking of using a voltage buffer for the input stage, in order to have a low impedence at the buffer output and then amplify the signal with a non inverting op-amp.

Is it a good idea?

If I had to use an opamp with a small gain bandwidth product, is there a way to externaly compensate the op-amp dominant pole and increase the GBW product?

Thanks for your help!


texts: Audio filtering circuit with capacitor shorted

texts:
I was looking at the Adafruit FONA cellular network modem breakout board schematic and found something that I can't quite understand. The breakout board has an audio input and output that both goes into the SIM5320A modem through a filter.

I found the audio filter quite strange as there is 2 capacitors where both terminals are connected together. See circled components

What is the purpose of such design?


texts: In case Vgs is supplied and equal or above of its threshold level so that I expect it's open, but how about a fault occured which I don't know, how can I understand it's open or not by looking on its Vds voltage?


texts:
I have an ESP32 that I want to power from an external source. It's a dev board and have an USB input for programming and 5V, but moving past my prototype, I want to ditch the USB (I have a separate power supply board that will power two MCUs)

The Arduino boards have a vIN pin for this purpose. My setup works if I connect the 5V output from the Power supply board to the 5V pins of my ESP32 and to the vIN of the Arduino board.

Im just curios if this is "safe" or the right way to to it. Ive always thought of the 5V pin as 5V "out", not "in".


texts:
I've got a virtual isolation transformer by connecting two 12V transformers at the secondaries, so the input to my circuit is an isolated 120VAC (US).

I'm creating a 2 level Greinacher style voltage multiplier, so a voltage quadrupler, roughly. Based on my simulations, about 1uF for the caps ought to get me up to a bit under 440V (anywhere in the 400V arena is fine).

Does it matter what kind of caps I use? Will a 500V rating be sufficient?

Edit: It just occurred to me that the 4 caps that are part of the multiplyer never see more than about 220V or so across them. The only cap that would see the full 440V or so would be the filter cap, as only one other cap, in the first level of the multiplier, references ground. The others reference the previous stage which is ~220V less.


texts:
It is commonly known that power control in CDMA is needed since all users/base stations transmit on the same frequency, and power control would help to limit the interference received at the base station.

My question is more fundamental - Why is it a problem that the various incoming signals (at the base station) are received with different power? Can we not distinguish each signal as per the Spreading Code or Walsh Code?


texts:
The table below, gives some parameters of DC cables:

Based on the table above, the average diameter of the first cable (1x2.50) is 5.1 mm.
As far as i know the cross section can be found by the following equation.
S = pi* r^2 , where r is the radius of cable.
However, if you do the math, the calculated cross section is 20,417 mm^2  which is significantly different from the section of the table (6 mm^2).
Where am I wrong ?


texts:
I am trying to read data from an I2C connected touch sensor. Specifically the Azotec IQS266. I plan to preprogram all of the settings the way I want them, and then not touch them again after that. In addition to this, there is really only one piece of memory that I am interested in, the track pad gesture information at TP_FLAGS (0x02, offset 0).

This brings me to the question: how could I monitor a single memory address of a single device on an I2C line, without the use of a microcontroller? Say for instance, I wanted to light up 8 LEDs according to the 8 bits of information stored at that address whenever the Azotec device produced a ready signal.

I agree that a microcontroller would make the most sense, but there are some cases where maybe you would prefer to avoid their use. Certain regulatory bodies become harder to deal with when you introduce 'software' into a design, and it may be advantageous to get simple data from an I2C capable device with a more 'hardware' based approach. Is this possible to monitor one I2C device for a specific address, and essentially convert its information to a parallel GPO output?


texts:
Unlike any other board , every pin on Arduino due can be used as interrupt.How that's possible? What is the concept behind that?
Apart from due , are there any boards /MCUs that can do the same thing ?


texts:
I am using an XP Power XP-IL1224S 12V to 24V DC-DC converter, does anyone have experience with the current rating of these kinds of parts?

The maximum current is rated as 84mA @ 24V, which works out to 2W - so this is an average current rating.
How would I go about finding out the peak current rating? My application is drawing over 400mA for peak (for 40-80mS) and I am concerned about the longevity of part.

I've tried contacting the manufacturer but I've gotten no response back :(


texts: Has someone tried to keep a CD at a further distance from the CD-pickup-reader?

texts:
So, I basically want to know the range of the IR light that comes from a CD reader/writer (KSS-213C). I used an IR sensor(IR Photodiode) to detect the light that comes from the pickup reader, but until I go very close to the lens, I'm not getting any reading. (Following image source: google.com)

Also, if I remove the lens, will the range of the IR laser increase?

If you need any other information, I will add it along later.


texts: Magnetic ballast with g23 bulb with capacitor

texts:
I am trying to make a UV-b photo-therapy light and want to make sure I'm understanding the circuitry correctly-so i don't hastily burn a $50 bulb.
Im using a Phillips PL-S 9W/01/2P (link here). It's a 9 watt 2 pin g23 socket bulb.

From what I've found, I need a 9w magnetic ballast, as electronic ballasts won't work with the build in preheat capacitor in the bulb. The part that I'm confucius about is the voltage that the bulb receives. The spec sheet  says 60V, but am confused about how to match that part up with a correct ballast. I tried to track down a good example and have this.
Any suggestions for the correct ballast or any other circutry 'magic' I haven't taken into account?

Thanks


texts: How to model the motor for this PWM motor driver circuit and is this simulation reliable?

texts:
I want to control the speed of this brushed DC motor with PWM control by using a uC board like an Arduino board. So the PWM output is 5V and it can source only upto 20mA so I need to use a transistor buffer. The DC motor specs are given as following:

And below is the driver circuit I plan to use. Before soldering I have some questions not settled, I merged a transistor buffer with this power MOSFET I have at the moment. I only have these transistors at the moment. And I want a non-inverting logic. I mean when PWM is 100% the motor should run at full speed and vica versa. That's why I use two bipolar and drive the load(motor) on the upper side of the MOSFET. PWM frequency can be 500Hz up to 24kHz. Not decided yet.

When I simulate the MOSFET drain voltage, drain current, motor current and the MOSFET power I get the following plots(PWM freq in this case is 500Hz):

1-) If there is not fundamental problem with this driver circuit, how can I model the DC motor? I modeled it as L and R series but the values are based on assumption. Is it correct to estimate motor resistance Rm from  the specs as 24/0.3A = 72 Ohm? How about the inductance? Is 1mH realistic?

2-) And from the MOSFET data sheet, upto what max current this MOSFET can handle without a heatsink? I'm asking because I might change the motor voltage or use similar type of motor with more current.


texts: All conductors exhibit capacitance, inductance, and resistance; does the same apply to memristance?

texts: All conductors exhibit capacitance, inductance, and (excepting superconductors) resistance. Does the same apply to memristance? Do all conductors exhibit memristance to some degree? Or is the value of a generic conductor's memristance theoretically zero?


texts: Will a low-pass filter make zero-crossing detection less precise?

texts:
In my application I need to sample a number of bipolar signals coming from piezo sensors, and detect their relative time difference (for multilateration based on difference time of arrival).

I expect the signals themselves have a fairly low bandwidth, around 10kHz, but I'd like to determine (among others) when their zero-crossings happen with an accuracy of 1-2μs.

I'm considering the ADS8661 as the ADC: its sampling rate of 1.2MSPS seems accurate enough, and the presence of a built-in analog frontend would make my schematic simpler.

I see that the frontend has a low-pass filter with a cutoff frequency of 15kHz. Given that it will remove all higher frequencies, is there a risk that it will make zero-crossing detection less precise?


texts: Snubber capacitor VAC handling by frequency of C0G?

texts:
I'm looking for a suitable snubber capacitor (220 pf) for a boost converter.

The semiconductor manufacturer recommends some ceramic capacitors for this

http://www.mouser.com/ds/2/212/KEM_C1035_C0G_PULSE_SMD-515563.pdf

The capacitor will have a stress of around 70kHz 800Vpp.
Even though the rated Vdc i 2000 V I'm a bit skeptic it will handle the 800 Vpp at 70 kHz.

Maybe there is something I don't know, I just know that film capacitors usually have a Vrms depending on frequency.

Hope someone could enlighten me


texts: What is the relationship between speaker volume change and resistance change?

texts:
Assume that we have a speaker whose volume is controlled by the potentiometer. If the resistance of the potentiometer changes by X%, and speaker volume changes by Y%, what is the ideal relationship between the changes?
Y=C.X, is C = 1 or can it be anything?


texts: Fuse and AWG choice for immersion heater circuit

texts:
I am planning to operate a 1500 W resistance immersion heater with an SSR and I'm trying to determine which fuse and AWG wire to use. The 1500 W heater on 115 VAC should operate at a current of around 13 A. The SSR is rated for 25 A. The chart from Grainger's website says that 14 AWG should be good for up to 15 A, so I'm planning on going with that size. I searched on McMasterCarr for a fuse for 13 A and the closest thing that I found was 15 A, so that is what I'm planning on using. Is the 15 A rating too high above the expected 13 A operating current?

Part of the reason for the fuse is to protect the circuit from power spikes/surges, but how much higher can those surges make the current go, compared to the normal current of the circuit? Should I be using 12 AWG wire (rated for 20 A) to account for power surges that might bring the current above the 15 A that the 14 AWG wire is rated for?

I have also seen some diagrams where it looks like the fuse is installed on the return line (shown black below) instead of on the hot wire (shown red below) before the SSR like in my diagram below. Should the AC fuse be placed before the SSR or on the return line and why would I install it on the return line if that is the right way? These questions are related to the AC loop in the diagram below:


texts:
I want to read a voltage of 3.3V on my MCU's ADC input.
I have a potentiometer that is to provide some feedback. I am wondering if it is necessary to add the R1 resistor, I added it since my MCU has a current limit of 8mA for GPIO, although I think this pin won't draw current but only read the voltage?

simulate this circuit – Schematic created using CircuitLab


texts: Understanding Resonant Frequency in a Series RLC Circuit

texts:
After spending a couple of hours on the internet searching for answers I'm hoping Stack Exchange can help me.

Recently, using simulation software, I used an oscilloscope to calculate the resonant frequency of the circuit, by measuring the sine wave of the resistor. I used the equation 1/T, with T being the time period between the start of the wave and the peak of the wave. this gave me Wn (or Wo, whatever your preference).
My reasoning behind this was that resonance is when Xl = Xc, meaning the circuit it purely resistive so the resistance would be at it's peak.

However

When doing the same tests in the lab irl I was told to measure Wn over the capacitor instead, as Q factor is at it's highest when at at resonance as Q=VC/VS.

Both methods gave the same answer, and I'm sure there is a simple explanation as to why, but I simply cannot get my head around it right now and information online is phrased in a manner that is not helping me to understand.

Which method is better? Are the reasonings for using either method correct?


texts:
I have this ic:
https://www.ti.com/product/SN74CBT3251
However, if you look at the actual packaging, there is not a circle, in order to figure out pin 1.
This is a picture of the IC:

Can someone give me a tip, on how to identify which is pin 1?


texts: How to transition from using linear to switching voltage regulators?

texts:
I'd like to start using switching voltage regulators such as the LM2575 in the Arduino-like boards I design, instead of the linear regulators I usually use, such as LM7805 and LM7812, mainly to avoid overheating.

However, I'm finding a little difficult to make the transition, as there are a few more things to worry about when using switching voltage regulators in such designs. The following are a few of the obstacles I've found while studying the LM2575 datasheet:

Inductor selection based on maximum voltage and current;
PCB layout issues, such as single-point grounding and ground plane construction;
Continuous and discontinuous modes of operation (when to select each mode).

Could someone provide some guidelines for beginners like me who would like to transition from linear to switching regulators? Are there any traps or dangerous situations to avoid?

Edit:
To be more specific, I have three examples I would like help with:

I have an input of 15 to 18V and want the regulator to output 0.8 to 1.0A @12V. But during operation the load may require less current (when less 7-segment displays will be lit). What inductor should I use for that situation? Should I select the inductor for continuous and discontinuous operation mode?
What would be a good choice of inductor, input and output capacitors if I wanted to replace the LM7805 linear regulator for a LM2575@5V on an Arduino Single Sided Serial board (S3V3 - Severino).
Will I have to worry about EMI to a RF receiver on the same board I use the LM2575?


texts: How to implement gain and offset in a single opamp?

texts:
I tried designer here in this page. But my particular case (Case 2) seems not working in the page.
Then I Read this document and my case there, is section 4. But my calculation results are not producing intended result in LT Spice. I am making some mistake somewhere, which I cannot locate. Can somebody provide me the solution?
I am using Op-amp  LM324 with single supply 12V.
My input signal spans from 4.5V to 6.5V. I need to span the output signal from 3V to 10V. Reference voltage I can provide is 5V.
Circuit I follow is here

Thanks.
Here is the circuit I tried. The output spans from 7.5V to 10.5V with these values. The values I calculated from  the Document I referenced above.


texts: Bit-banging a ShifBrite led driver with a PIC

texts:
I am having problems making communicate a Shiftbrite A6281 led driver with a PIC18F4550. What I am trying to do is to send the RGB values to the driver in order to select the color of the led, but I am not even being able to light it up.

My main problem is that I have never used bit-banging before and I am afraid that a novice error in my code may be causing the problem. (such as port configurations or delays). The goal is to send 32 bits to the driver and then make it load (latch) them, then it should light up the leds.

I am using proteus to simulate the circuit and XC8 as a compiler, here is a screenshot and the code used:

#define _XTAL_FREQ 8000000
#include <p18f4550.h>
#include "config.h"
#include <xc.h>

#define RA0  PORTAbits.RA0
#define RA1  PORTAbits.RA1
#define RA2  PORTAbits.RA2
#define RA3  PORTAbits.RA3
#define RA4  PORTAbits.RA4

#define DATA  PORTBbits.RB0
#define CLOCK  PORTBbits.RB6
#define LATCH  PORTBbits.RB2
#define ENABLE PORTBbits.RB4

#define BLUE  0x3FF00000
#define GREEN  0x000FFC00
#define RED  0x000003FF
#define WHITE 0x3FFFFFFF
#define BLACK 0x00000000

typedef unsigned char byte;

void write_color(unsigned long int color)
{
    LATCH = 0;
    CLOCK = 0;
    ENABLE = 0; // 0 = ON

    for (int i=1; i<33; ++i) {
        if ((color >> (32 - i)) & 1) DATA = 1;
        else DATA = 0;
        CLOCK = 1;
        __delay_ms(1);
        CLOCK = 0;
    }

    LATCH = 1;
    CLOCK = 1; CLOCK = 0;
    __delay_ms(1);
    LATCH = 0;
    // ENABLE = 1;
}

void main()
{
    ADCON1 = 0xFF;  // digital
    TRISA = 0xFF;
    TRISB = 0x00;   // PORTB pins = output

    while (1) {
        if (RA0 == 1) write_color(BLUE);
        else if (RA1 == 1) write_color(GREEN);
        else if (RA2 == 1) write_color(RED);
        else if (RA3 == 1) write_color(WHITE);
        else if (RA4 == 1) write_color(BLACK);
        __delay_ms(1);
    }

}

Any help would be greatly appreciated, thanks in advance.


texts: What is the maximum frequency of CMOS level triangle wave?

texts:
What is the maximum frequency of CMOS (3.3V) level triangle (or square) wave that I can achieve with
serial discrete ICs (for example: discrete PLL or DAC + OpAmp cascade)?


texts:
I have done with a solar panel powered mobile charger. This is how it is now

Solar Panel(5W,8V(max),0.59A(max)) -> 7806(5.4V normally) -> Female USB -> Mobile

Since 78XX just reduces the voltage,takes so much time for my mobile to get charged, because of low current. Is there a way, something like  Buck converter that would practically work for this case? Any reference would be helpful.


texts: Calculated MOSFET switching time does not agree w/ expected results

texts:
In preparation to design my own boost converter, I am trying to analyze the poorly-performing 555 boost converter circuit discussed here (so that I know which mistakes to avoid):

555 timer boost converter doesn't meet spec

The circuit is reproduced here for convenience:

The accepted answer's comments suggested that the power MOSFET attached to the 555 has a switching-on time in the microseconds range and a current of approximately 1 mA. While I trust the posters' judgments, they do not explain how they reached those values. I wanted to try to calculate the expected switching time on my own and see if I could reproduce the results.

Using an IRF740 datasheet and an appnote (not enough rep to post the links) for calculating the switching speed during turn-on, I found the following equation:
$$
t_{ir} = (R_g + R_{g\_app})*(C_{iss}~at~V_{DS})*\ln(\frac{g_{fs}(V_{GS\_APP}-V_{th})}{g_{fs}(V_{GS\_APP}-V_{th})-I_{DS}})
$$

where:

\$R_g\$ is gate resistance.
\$R_{g\_app}\$ is external gate resistance (0 Ohms).
\$C_{iss}\$ is input capacitance (1400pF @ 9V).
\$I_{DS}\$ is Drain-Source current.
\$g_{fs}\$ is forward transconductance (5.8 S).
\$V_{Th}\$ is threshold voltage (4V worst case).

I made the following assumptions when trying to calculate switching time with the above equation:

\$R_g\$ is not given. Assume 1 Ohm.
Input \$V_{GS}\$ is 9 - 1.7 = 7.3 Volts, according to voltage drop from 555.
\$I_{DS}\$ at maximum is 1.44 Amps (worst case), according to the linked answer.
Inductor current is constant just before switch, so MOSFET sees 9V across drain and source.
\$C_{iss}\$ is assumed from chart (25C) on page 3 of the datasheet.

When I do the calculation, my predicted switching speed is approximately:
$$
1.4*10^{-9}*\ln(\frac{5.8(3.3)}{5.8(3.3)-1.44}) = 1.09*10^{-10}s
$$

My calculated switching time seems orders of magnitudes too fast, considering the output current calculated is in the milliamp range. Does anyone have an idea of what assumptions I made that do not hold, and what assumptions I should replace? It would be nice if I can get my predicted current and switching speed within an order of magnitude of previous analyses done by others (which I assume to be correct).


texts: Exceeding _Enable input voltage_ of optocoupler

texts:
I have microcontoller board with following optocoupler interface

which is obviously made for input up to 5V. Based on datasheet I found, Vf = 1.5 V and If = 15 mA (whereby recommended range is from 0.3 mA up to 10 mA). On page 10, they say that

  Enable input voltage (Not to Exceed Vcc by more then 500mV): Max: Vcc + 0.5 V

My question is, if I replace R17 with higher resistance resistor (i.e. 2.4 kOhms) I am still not allowed to connect 24V on OCVCC? With higher resistor, I can limit current through optocoupler, but wouldn't it still exceed Max. enable input voltage? Or will such high resistor cause voltage drop?

BTW, I am amateur doing microcontoller just for fun. If I am asking stupid question, I apologize in advance!

Thanks in advance!


texts:
I bought a spark fun inventors kit in order to learn about arduino. I am attempting to complete circuit 13 http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Kits/SFE03-0012-SIK.Guide-300dpi-01.pdf  .
It is a circuit to control 2 LEDs using a relay. I know I have the relay hooked up correctly because I can hear it click, but instead of the first LED turning off and the second LED turning on the first LED dims. Then when the relay clicks again the first LED brightens. I'm not sure what I have done wrong but no matter how many times I undo the circuit and start over I get the same result. I am especially confused because from what I understand a relay functions like a digital on/off switch. So I cannot understand why the first LED would dim instead of just turning off, even if I didn't have the second LED connected correctly.

Any tips/pointer/advice would be really appreciated. This is driving me nuts.
Thanks.


texts: Basic Power Consumption - Continually leave AC on vs Occasional start/stop

texts:
Question

If my goal is to keep my energy consumption at a minimum should I power my AC off once the room is cool or leave it running in its sort of stand-by state (fan still running)? I'm not sure of the physics of the power consumption but I assume it takes more power to start the A/C than it takes to keep it running.

Extra

I live in an NYC apartment
I run my A/C for about 10 minutes and my room is cooled down. I turn it off for about 10 minutes and the room STARTS to become noticeably warm again.
This AC is a "portable" LG 8000btu (LP0817WSR) if that impacts this question at all.


texts: In an ALU, is every function calcuated simultaneously?

texts: I'm designing a 4 bit ALU as a project. I have circuits that can calculate addition, subtraction and bitwise logic operations - my question is, do I tie A & B (4 bit inputs) to every circuit that performs an operation/function, meaning every function is carried out at once, and use a multiplexer to select which output I want? Or is there a more efficient/elegant way of performing just the operation I want on A & B? I'm not sure (traditionally) how this is done.


texts:
I'm trying to build a device that is able learn a command from a TV IR Remote and  recognise when this command is sent to it. I've see that the most common protocols used are NEC and Philips and that the frequency may vary of some kHz depending on the manufacturer. I need a receiver that is compatible with most of TVs.

The problem is the frequency: I've see modules like the Vishay TSOP48XX series but they only work with a specified frequency (like 36 kHz, 38 kHz, 40 kHz). Is it possible use these receivers out of their frequency range of 1 or 2 kHz with accettable results?

If not, what's the best solution in order to receive commands from all TVs?


texts: How CMOS transistors might be used as a capacitive sensor for biopotential?

texts:
I was wondering how CMOS-based capacitive electrodes might be designed (e.g. in this article I stumbled on). It seems to me, that it would make sense to capacitively couple the input of the transistor to the signal you were trying to measure.

But how would one go from one bit of information (one transistor conducting or not conducting as a result of coupling) to a more robust representation of the signal with an amplitude described by multiple bits (i.e. some quantized representation of the signal in, say, 16 bits). Is it possible that the transistors are each designed with different threshold values to represent the various bits that are the amplitude of the signal at that point in time? Is that even practical, or is there some other method that might be employed to achieve that affect?


texts: Control onboard LED via PWM on STM32F4 Discovery board (HAL library)

texts:
I'm writing a program where I want to use the intensity/brightness of one of the onboard LEDs to indicate a specific state change. Is it possible to use PWM or some other means to modify the brightness of one of the onboard LEDs?

I have set a timer into PWM mode that ticks via interrupt every 50 ms and provides the PWM value range that I want. However, I'm unsure of how to make the GPIO pin (LD pins) respond to the ticks of the timer/PWM. I've tried configuring the LD/onboard-LED pins in the GPIO.c with the following code:

GPIO_InitStruct.Pin = LD4_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
GPIO_InitStruct.Alternate = GPIO_AF1_TIM2;
HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

From the information I have gathered from the HAL manual and other online information, I hoped that these changes (setting GPIO_InitStruct.Mode = GPIO_MODE_AF_PP and GPIO_InitStruct.Alternate = GPIO_AF1_TIM2) would allow the timer to control the LED output however, with this code the LED doesn't activate at all.

Is there something I'm missing with this method or is this the completely wrong method to be trying to control the brightness of the onboard LED?

Any assistance on this would be appreciated.


texts: Synchronizing oscilloscope to reference time

texts:
Consider a lab that contains an NTP (network time protocol) time server that synchronizes events between multiple workstations connected to the same network. I have a Tektronix DPO4034 oscilloscope that features an ethernet port. Would it be possible to synchronize the oscilloscope to the NTP time server such that an event could be captured on the oscilloscope and its time recorded with respect to the NTP reference time? Is this a feature that's common or available on modern oscilloscopes?

I searched the DPO4034 manual for all instances of 'time' or 'timestamp'. It looks like you can buy modules that allow you to capture I2C, SPI, CAN, or serial bus events that contain timestamp information, but from the following image it looks like it only provides relative time (presumably with respect to some arbitrary reference time?):

Plus, I'd like to capture time events for arbitrary signals, not necessarily I2C, SPI, CAN, or serial signals. Does anybody have any advice?


texts: Don't Understand the Notation on this State Diagram

texts:
This like a simple question, but I can't find a clear answer anywhere. Basically, I am used to seeing and implementing state diagrams that look like this:

Where the output and input are in this notation: input/output at each edge.
Now I have been given a diagram that looks like this:

Where it looks like the output is possible written underneath each State? I am not sure if I should just apply the number written under the State (e.g A/0) to each of the edges pointing away from the state to make it look like the first diagram or if the number means something different.


texts: 2 out of 3 buttons on wine fridge display stopped working

texts:
I have an Ansonic wine fridge. It has a front display that display the temperature of the fridge, and has 3 buttons: + temperature, - temperature, and light.

Recently, the + button stopped working, so I removed the button panel and reseated it, and now the - button no longer works, but the light button still works.
On the inside, it looks like this:

Since the temperature can't be controlled anymore, it always tries to go to 10 degrees Celsius, which means the compressor is always engaged and it's too loud (it's also not the best temperature for the wine).
My question is: what kind of buttons are these, why are two of them not working anymore, and what's the best way to go about diagnosing this?
I have a multi-meter and a soldering iron, if that's helpful.


texts: Say I have a signal with a SNR of 100 dB. I pass it through an ADC with 16 bits. Since the ADC will have a SNR of 6*N + 1.77 dB, how can I calculate the final SNR of the signal?


texts:
I have a circuit that looks like the following. It appears to be simple-

What's the thevenin equivalent? I can't seem to simplify it as there are no common nodes that any of the resistors connect.


texts: Using a cap to predict the presence of a pulse via voltmeter

texts:
I have a pulsed power supply that provides 250v pulses with a pulse width of 2 uS and a frequency of 10 Hz. However, I'm unaware of the polarity of these pulses.

In order to detect the polarity of the pulses, I'm planning to place a diode in series with the output of the pulsed power supply (which only has a single output lead). Depending on the polarity of the voltage, the pulse will either pass through the diode or be defected.

The diode is followed by a charging resistor (20 ohms) in series with a 4 nF capacitor. A voltmeter probe makes contact with the other pole of the capacitor, with the opposite voltmeter probe being grounded. The set up may be shown below:

simulate this circuit – Schematic created using CircuitLab

Based on my specs, I'm expecting to receive some sort of a signal/blip on my multimeter (Fluke 87 III True RMS Meter) to provide some evidence of the presence of a pulse.

Please note that I am not looking to measure the pulse width, voltage, or frequency of the pulses. I'm only looking to see if they are present after the diode.

EDIT 1: The question is whether or not this set up will work to detect a measurable signal.

EDIT 2: The diode shown is a 300v diode, the label shown was only auto-generated by the system.


texts: Design Question: 20 MS/s data acquisition

texts:
Let me preface that I am fairly new at working with sampling high speed signals. Specifically, I want to do some processing on slightly corrupt NTSC signals. For this, I need to sample at above 14.3 MHz. So suppose I want to take 12 to 16 bit samples at 16 MS/s with an ADC - that figure is reasonable enough to attain judging by the selection available. However, the challenge is in storing this result. Can someone give me any suggestions to solve this problem?

I don't yet have the schematics as it is still early in the design process. But the general idea is that I will have an ADC, which will collect samples and a microcontroller that will facilitate storing those samples.

In terms of total size, I am looking at (worst case) say:

$$\frac{16\ MS}{s} \cdot\frac{16\ bits}{S}\cdot\frac{byte}{8\ bit} = \frac{32\ MB}{s}$$

And the NTSC video source I am trying to recover is about 2 hours long worst case, so:

$$\frac{32\ MB}{s}\cdot\frac{3600\ s}{hr}\cdot\frac{2\ hr}{tape}\cdot\frac{GB}{1000\ MB} = \frac{230.4\ GB}{tape}$$

Further clarifications:

Why do I have to do this in real time: The video I am trying to restore comes from a Video8 tape, that can only be read using an old analog video recorder. The recorder spits out the content of the tape onto its NTSC port, but the data is slightly corrupted (vertical sync signal missing, horizontal line data okay). This shouldn't be too hard to fix in software if only I could digitize the tape.

Is the NTSC video in color: Yes. But as long as I can digitize the NTSC signal, I will be able to process it in software and convert it from lines -> fields -> frames.

Why not use a frame grabber: Because the video signal is corrupt. Like I mentioned before, it is missing the proper vertical sync signal. The line data, however is completely fine so I believe it is salvageable by software. A frame grabber usually uses hardware decoding for NTSC, which will not work in this case because the signal has to be processed first.


texts: read 12V logic pin from arduino using an NPN transistor

texts:
I have an inductance sensor on a CNC machine that goes 12V high when triggered (open collector when not) . I want to read that input on my arduino who uses 5V logic.

I was thinking I could just use a simple NPN transistor to do the logic level shifting. Would this work? I dont want to test it incase it could fry the arduino.


texts:
I have the following problem to solve. I wanna find the current through R1 so i did a node analysis on this circuit. This is what i got so far:

I2 = I1 + I3 (I2 being the current going through R2 etc)

I2 = (VB - 0)/R2 (VB being the node between r1 and r3)

I3 = ((VB - 0)/R3+R4)+I

I1 = (VB-E)/R1

i put all this together and get 28800 = 201VB + 1000*I. Now i dont know what to do with the I aka the current source. Do i convert it to voltage?


texts: Is there a simple way to toggle kicad layers? For now, I am able only to manually tick the respective layer boxes. Is there a way to optimize this task, e.g. layer profiles?


texts:
I'm working on a project where I use DC motor and gearbox to reduce the speed and get a higher torque.

The problem is, when the project sit, for example on a table, the noise is amplified. (with transferred vibration). Which is great for the musical box but a real pain for the DC motor and gears noise.

Do you have any idea on how I can reduce the noise of this ?

(If you think StackExchange EE is not the correct place, let me know where I can ask this and I'll delete the post)


texts: Why does Arduino SD card module only work when multimeter attached?

texts:
I have an Arduino Mega and the SD card module found at this link:
http://www.ebay.com.au/itm/SD-Card-Module-Slot-Socket-Reader-Arduino-ARM-MCU-Read-And-Write-/180868021964#vi-content

I am using this test code to check if it is working: http://arduino.cc/en/Tutorial/CardInfo

The problem was that it was not working, so I started checking voltages on the SD card module. Then I found that when I have the multimeter probes on the SCK (Serial Clock) and GND pins the code works. I unplugged the probes from the multimeter but left the ends attached to the SD card module and it still worked. As soon as I remove one of the probes from the module (either GND or SCK), the code no longer works.

I have no idea what is going on here but is it something to do with the probes changing the resistance of the pins that is making it work?


texts: Ultra High sensitive sound capturing sensors

texts: We are working on a project which involves in capturing signals traveling through a rail line. Unfortunately in our country, we have lots of joint in between rail tracks. So the signal gets attenuated and becomes very hard to capture using normal devices like microphones and accelerometers. Could anyone please tell us of good (actually very good) sound capturing devices?


texts:
As far as I understand, and antenna like a simple dipole has a circular radiation pattern at the 2 edges, so the physical aperture in this case is circular.

$${A = \pi  * r^2}$$

Where r is the radius of the circle surrounding the dipole, or basically r is the length of 1 rod of the dipole.

Then we have the gain formula:

$${G = 10*  \log_{10} (  \frac{\eta * 4 *  \pi * A }{\lambda ^2 }   )}$$

Where eta is the efficiency, and A is the aperture calculated above.

So can we use the following formula to calculate the gain of an antenna?

$${G =  10* \log_{10} (  \frac{\eta * 4 *  \pi^2 * r^2 }{\lambda ^2 }   )}$$


texts:
I need a precision low value sense resistor to make current measurements e.g. 10R 0.01R. Looking for precise resistors e.g. Vishay, show that these are expensive e.g. $35 for a single 0.001-0.005% tolerance resistor with 10ppm/K thermal coefficient.

Too much for a hobbyist like myself. What cheap workarounds can I use instead?

Currently, I'm thinking of measuring several 1% metal film resistors and using that, but not sure if there is a better option e.g. some other material or whether there is a trick to reduce the temperature variation?


texts: finding if certain numbers are don't cares in KMAP

texts:
i've solved several question but i don't know how to solve this one, please help me if you can, as my due date is today.

\$f(a,b,c,d)=\sum(0,1,2,4,5,10,12)\$

after a lot of trials, i know that this is the boolean i get a'c'+c'd'+b'd'

how can i know if (i) 6 AND 14 (ii) 15 could've some of the don't cares?

this is important: how can i know for sure if 8 was a don't care? (if it was).

please help me if you know the answer and can help. i am so frustrated from this.

this is what i got, please tell me if its true and if not help me correct it:

 c'.d' c'.d c.d c.d'

a'.b'  1 1 0 1

a'.b 1 1 0 x

a.b  1 0 x x

a.b' x 0 0 1

if m6, and m14 together, i get cd' which is not what i was looking for so i guess it's not possible.
if m15, it doesn't help me at all (it's not connected to anything, i can't pair it)
if m8, if i am right, then it simplifies the simplification of the given function. i am not sure if it is a must though


texts: Is time-invariant system taking system initial state account?

texts:
The time-invariant system is defined as following:

If y(t) = (H(x))(t) and y(t − τ ) = (H(x))(t− τ )
Then H is a time-invariant system.

Has this definition taken system initial stats account? At t=0 and t=τ, the same system could have different states, due to a discharging capacitor and etc. Then y(t) and y(t-τ) could be different for a time-invariant system.

So when taking initial states into account, a time-invariant system could be no longer time-invariant. Is my understanding correct?


texts:
What formula can I use to determine the capacity of a USB battery bank (ex. emergency backup battery for a cell phone) to power a device that consumes x miliamps at 5 volts for y hours?

I'm specifically using this for a raspberry pi that consumes 1200 miliamps at 5 volts.


texts: NP0 C0G X7R (Y5V?) Typical Leakage Currents?

texts:
does anyone have some "typical" values or ballpark averages for the various SMT capacitor leakages?

I assume that if the leakage is dependent on the dielectric, then NP0's would be "best." But how does the typical NP0's leakage compare to say, an X7R? Thanks.


texts:
Given this circuit

Switch \$S\$ is closed for a long time (\$t<0\$). At \$t=0\$, switch \$S\$ is opened. Find expression for \$V_c\$.

I know if the circuit only has one source I could apply KCL right away. But in this case, the circuit has two sources.


texts:
I have designed this simple analog temperature transmitter. Specifically, this is a 2-wires loop-powered transmitter. The circuit is intended to measure temperatures from -50 to 400 °C. The first stage (Blue square)is a conditioning circuit which convert the input range voltage from thermocouple (-2.431 mV to 21.848 mV) to 0-5V. The second stage convert the 0-5V to 4-20 mA.

The first stage by itlself works properly, but when connecting the second stage, that is, the one to convert voltage to current, the regulated voltage from the TL431 goes down. The second stage also works properly by itself. The regulated voltage is 6V, but it goes to 2.4V when joining the two stages. The regulator is supposed to deliver 3.6 mA max.

I am using TLV2772 Op amps. I also have LT1013. The LM35 is used for cold juction compensation.

Any suggestions about handling this problem?


texts: why when start induction motor the torque oscillate before become constant, like the following matlab torque simulation graph .


texts:
I'm having trouble getting my colpitt's oscillator to give me nice sinusoids. It seems to be clipping the output for for reasons I don't understand. The circuits needs to oscillate at 7MHz (Body capacitance does zilch at 1.5MHz). So here's my process. I choose \$I_c = 150 \mathrm{mA}\$ since that's what they tested the transistor at according to the datasheet. Also i want to bias \$V_{c}\$ in the middle of the supply voltage. With this in mind here is my process:

\$R_c = \frac{12-6}{150\mathrm{mA}} = 40 \Omega\$
Equally split the 6V across the transistor and emitter resistor

\$R_e = \frac{3V}{150\mathrm{mA}}\ = 20\Omega\$

If \$V_e = 3\mathrm{V}\$, \$Vb = 3.7\mathrm{V}\$
Assuming \$h_{fe} = 100, I_b\$ has to be \$1.5\mathrm{mA}\$
If 10 times \$I_b\$ flows through the voltage divider, \$R_1\$ and \$R_2\$ can be calculated to be \$533.4\Omega\$ and \$246.7\Omega\$ respectively.
Oscillation frequency is \$f = \frac{1}{2\times \pi\times \sqrt{800\times 10^{-9}\times 0.6\times 10^{-9}}} = 7.2\mathrm{MHz}\$

LTSpice says the frequency is \$5.47MHz\$ and it seems to be quite distorted and clipping at the bottom.
Any help in fixing this or understanding this would be awesome.

Thanks!!

simulate this circuit – Schematic created using CircuitLab

EDIT : As you guys suggested, I biased the transistor at 10mA instead and added a schottky diode between the forward and feedback path. Someone pointed out to me that the higher the current, the lower the BW so that might have been messing it up too. Everything works now. Thanks!!


texts: Recommendation for a USB digital simulator

texts:
It's becoming quite frequent to me having a new digital subsystem which I want to test in isolation before trying to make a prototype circuit. I've been using the digital analyzer by Saleae for inputs, which is quite handy, but I'm wondering if I could find or build its counterpart. Ideally it would be a device to plug in an USB port, would have many digital outputs (let's say 20 or more) and would come with software that would enable me to do a playback from a prerecorded file, or generate the output with a program or script.

Does anyone know about such a product, or have guidelines to build on my own?


texts:
I have some microcontrollers with TCXO's where I wish to measure their frequency stability using Allan variance (from say 1ms to 10s). However, my measurement equipment is limited. I have access to a 10 Mhz Rb source, a nice oscilloscope (sadly without support for external reference), and a 53220A Keysight frequency counter. I would think that the frequency counter would be the ideal to measure Allan variance, unfortunately, my model has significant gate "dead" time which appears to pollute my measurements.
Any ideas about how to go about performing these measurements would be greatly appreciated.


texts:
This question is related to my previous question about the battery charging and discharging. Here is the link to my previous question.

I have made a small change in my previous schematic, which is the PMOSFET. I have added NMOS in between the Charging IC and the Battery. Below is the schematic,

The following is the principle of the circuit,

Hysteresis of 3.4V and 4V is set using a Comparator.
Depending on the voltage level of battery, comparator gives the output. If the battery
voltage is 3.5V then the output of the comparator is "HIGH"; this then turns "ON" the mosfet M2 (and Turns "OFF" M1) allowing the charging IC to charge the battery. When the batter voltage reaches to 4V, comparator output becomes low. This then turns "ON" the Mosfet M1 (and turns "OFF" M2); allowing the battery to discharge to the load.
The load I am using is 0.25W 1.4K resistor but I have added 10 resistor in parallel. Which then makes the resistance of 140 ohm, so the current Iload=28mA.

Following is what I observe in the circuit.

When the battery is charging and it is 3.7V the charging stops and starts to discharge. At this point I was also monitoring the hysteresis point and it showed 4V, but what I don't understand is why did it stopped at 3.7V?
Also the discharging stopped at 3.48V instead of 3.4V. Also at this point i was monitoring the hysteresis point which was set to 3.4V.

Why is my hysteresis not working properly. I have used M1 as PMosfet so that battery gets connected to load when the output from the comparator is LOW and M2 as NMosfet to disconnect the charging process when the battery is connected to load.


texts: Estimating maximum current capacity of non copper wires

texts:
I am interested in estimating the max current capacity of wires made from materials other than copper, ie nichrome. I have found plenty of data on the current capacity of copper wires
here
https://www.powerstream.com/Wire_Size.htm
Can I estimate the max current capacity of a nichrome wire by comparing the restistivity of copper and nichrome? Would the current capacity of nichrome wire decrease in relation to copper wire by the same factor as the difference in resistivity between the two materials, or would the difference in thermal conductivities make such an estimation too inaccurate?


texts: Cockroft-Walton circuit use in bug zapper

texts:
The basic Cockroft Walton circuit consists of 3 stages of diodes and capacitors creating a voltage of around 1860 from standard AC 220V/50Hz supply.
I tried creating a bug zapper with the same circuit and achieved similar voltage at output and could generate spark on touching positive and negative terminals. The actual requirement is to generate 5000V best case or at least 3000 volts from 220V AC supply without the need of a transformer. Now for this I added 3 more stages to the circuit and measured the voltage with HV probe and it was around 3700V which is decent enough. I am using 0.47uf 800 volt capacitors and 1N4007 1A diodes for this
The moment I short the positive and negative terminals it generates a good spark but when I touch again them the spark starts to fade away and the voltage at the output starts decreasing on every spark. I checked what went wrong found out diodes keep getting damaged.  If we go from 3 to 4/5/6... stages, I thought diode has reverse voltage rating of 1000V, so I replaced them with 16kv 5mA HV diode, it couldn't even generate 1860 on 3 stages.
Question :

Why does the diode get damaged if I add one or more stages to below given 3 stage circuit?
How do I fix it and avoid damaging diodes if I have to use 1N4007 and generate 3000+ volts to be used as a bug zapper?

Ref video link to 1.8k fly/bug zapper: Youtube Link
This is the basic circuit for your reference:


texts: Schottky barrier diode as a bridge rectifier?

texts:
I am building a linear power supply. I need a bridge rectifier and the diodes I currently have can only handle up to a maximum of 1 amp, but I need 4-5 amps.

But I have a bunch of YG862C15R Schottky barrier diodes.

Can I somehow use them as a bridge rectifier or have I got this all wrong?

Since it only has three pins, two for the AC IN and only one for the DC OUT (I guess), won't there be any negative? Like in an IC rectifier which uses four pins. How do these work?


texts: Solar energy system design and calculations to power a computer

texts:
I have a computer that uses a 500-Watt power supply. Note that this is a 500-watt power supply. How much power the computer actually uses, I don't know. 500-watt supplies are pretty typical. I think the computer actually probably uses around 150 Watts on average.

I am trying to figure out how much solar panel and battery I would need to run the computer 8 hours a day, but I find the calculations confusing.

In my case I am not going to use an inverter. My plan is to connect the 12V battery directly to the DC lines powering the computer and its fans, so there is no AC conversion loss. (although this does leave the problem of how to turn 12V battery power into 5V computer power)

Can anybody walk me through the general process to do the calculation to size the panels and battery?

I live in Massachusetts (42-degrees latitude) and would need to run the computer through the winter months. I would probably need to have 3-5 days of buffer in the battery to deal with clouds and stuff, but that is just a guess.

Comment on the "Close" Votes

This question is about calculating the design envelope of a solar energy system, which is a problem in electrical engineering. This is an on-topic question.


texts:
I want to design a Switch Mode Li-ion charger which uses 5V as input and charges a single cell Li-ion cell.
I am referring this AppNote

On page 4 they have given the equation to find inductor value i.e.
$$
L = (V_i – V_{sat} – V_o) \times \frac{T_{on}}{2 \times I_{max}}
$$
If I use 5V Vin and want to charge at 1A current, the inductor value comes out to be very low. I assume Vo=4.2V. Ton=1.32\$\mu\$s (50% duty cycle) for 376KHz PWM.

So I am confused as to how they use switch mode chargers in mobile phones.

This is the schematic of typical charger:

simulate this circuit – Schematic created using CircuitLab

so I was wondering with 5V input and voltage drops at MOSFET and schottky diode would I have enough voltage to charge the battery?


texts: Sine wave pwm signal measurement with digital oscilloscope

texts:
I am beginner in electronics and I would like to measure 12 kHz sine wave pwm
signal on the output pin of my microcontroller. My problem is that I am not
able to setup the digital oscilloscope RIGOL MSO1104z (User's guide) in such a manner that I am able to see the signal. Firstly I tried to use Auto set function but without success (the signal is unstable). Then I tried to set the oscilloscope by myself (I set the trigger level and hold off time but there is only some transient waveform on the screen). I have been reading the User's guide to the oscilloscope but there are no practical examples how to set the oscilloscope for common measurements. Please can anybody give me an advice how to set up the oscilloscope for my measurement? Thanks a lot in advance.


texts: I was wondering if when I needed to run a cable from the negative terminal of my battery when running the positive inside my car for powering a CB radio. I know this seems like a dumb question but I have not been able to find a definite answer online.


texts: reverse engineering camera flash charger

texts:
I am trying to understand how exactly the voltage from a 1.5v battery gets connected to a 1000+v capaciter inside these disposable cameras. is there a speciffic chip designed to act as a voltage amplifier and diode or do capaciters act as a sponge of sorts and directly connecting them to lower power sources allow for saturation?

edit
after previous answers I have more questions.
1 you state the current is transfored to ac with a transistor* imbeded in the chip. does this mean I could get the same result with a suitable market transistor
(and other components*)

as my direct intentions for the hack are to use an increased voltage supply to drive a motor from a smaller set of cells (18650 to be exact) and I am aware that power is always lost durring any conversion, would it maybe be best to use an ac motor such as a furnace fan I have than the 12v scooter motor I had intended?

assuming I were to go with the ac alternative I would presume I would substantially be building an inverter,while I have had trouble with these being limited in their output to under 100 watts I suspect this may be mostly due to compenent costs and limits to ensure certain comercial safety ranges for delicate electronics's safety, as the whole point of this circuit will be to drive a motor some of those parts may be ommitted? I have apx30  18650 cells at my disposal though preferr to keep them in smaller banks of 2-4cells per set and have an arduino with relays I could use to switch banks,
what would be the easiest method (ie speciffic parts and general wiring preferred) to deliver the energy to get this motor running as good as possible.

particularly as I believe the fan motor calls for something like 20amps I would presume I may need multiple transisters in parallel,if so would I then need to bridge one of the legs on each to ensure they all switched at the same time to the same phase or would it need to be more complicated than that?

I will note the intent is to build a motorized cart from bikes and other materials.


texts: Why is the current in this circuit 100mA?

texts:
I am just learning electronics and trying to reason some figures I measure in simple circuits.

I need a bit of a hand with this one.

I have a 3.2V power source, and 2, 1 ohm resistors wired in series.

I want to determine the current in the circuit. I know that

I=V/R

So, I know the voltage and the resistance, so assume that after I use my multimeter over the start and end points of the circuit I should see

I=3.2/2
I=1.6amps

However, my multimeter reports 102mA!

So how does this make sense? What am I overlooking. It sounds like I may be plugging in the wrong figures somewhere.....

Help please!


texts: connect 2 audio inputs to 1 output using an audiosplitter

texts:
Alright guys, gals and overall people who are smarter than me,

I recently wanted to play some games on my laptop while also watching a youtube video on my phone at 3 A.M., so to not disturb my family I would need to use a pair of earbuds, but then I only had the option to get the gamesounds or the youtube sounds, so I went online to see if there was an easy software solution for this, which there was not (multi device wireless audio mixing is apparently quite a niche market). After about an hour of googling, I noticed an audio splitter lying next to me with a couple of 3mm male to male cables when I got an idea;

Would it be possible to put the two 3mm male to male cables in audio splitter, one to my phone and one to my laptop and then connect my earbuds to the third input of the splitter(see the schematic if i can't explain it very well), or will that just blow up my equipment? If it's save, would the audio even sound right?

simulate this circuit – Schematic created using CircuitLab

Any help on this matter would be greatly appreciated!


texts: Difference between an inverter and a buffer with active low input

texts:
In logic diagrams found in datasheets (e.g. Texas Instruments 74HC316) I've often seen both inverters and buffers with active-low inputs ("negated buffers" or "inverting buffers" or whatever they are called).

I wonder why they use different symbols, since from a logic level point of view they act the same (output is the logical NOT of the input after all).

Are there some differences in the implementation of the two? It seems to me that it is also manufacturer-dependent, since the datasheets of the same parts from other manufacturers may also use plain inverter symbols instead of "negated buffers" (e.g. NXP 74HC3416).


texts: I need a very small ARM based development board capable of running Linux (and Android, if possible, via SD card). The board should be not more than 25mm in terms of breadth. I found Raspberry Pi Model A to be perfect but it's not available. Any alternatives?


texts: IGBT ratings, I don't understand how this is possible

texts:
I found the IXGX400N30A3 at Digikey.  The datasheet says the device is rated for 400A @ 25C, 1200A @ 25C for 1ms, with a voltage rating of 300V and PD of 1000W.

Really?  This TO-264 package can control 400A of current all day long?  I can short out my TIG welder with it in DC mode?  How do those leads even carry 400A of current?


texts: Negative-Gm Oscillator Biasing Conditions

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I have some questions regarding the circuit below. I need to ensure two conditions are met. The output is taken from the drains of the cross-coupled pair. I think the drain voltages (1.198V) are not present at the same time during operation, but I'm not entirely sure. I'm pretty sure they switch back and forth.

1) I need to keep M2 in the saturation region. From my understanding, the cross-coupled pair will act as switches and turn off and on. Allowing for that 1.198V to always be present at the drain of M2. Therefore, $$1.198 \geq V_{bias,t} - V_{th} $$
$$V_{bias,t} \leq 1.198 + 500mV \leq 1.698 $$

Is this correct?

2) Bias M1 in the subthreshold region. Would I simply set the M1 bias voltage to a value of 1.675V? Because:

$$1.675 - 1.198 = 452mV$$


texts: Powering a motor through wireless electricity

texts:
simulate this circuit – Schematic created using CircuitLab

simulate this circuit

Schematic redrawn by Transistor. OP to edit or delete as required.

I have a wireless electricity transmission circuit that is intended to be used to power a toy car. However, the receiver coil does not cause the motor to rotate.

I am using a 9-volt battery in the transmitting coil, which is functioning properly. The receiving coil is receiving electricity and can power an LED. I used a bridge rectifier to convert the alternating current to a direct current to power the motor.

To test it, I connected the motor and LED in series as the output of the bridge rectifier with a capacitor going across the outputs. The LED lights up properly but the motor fails to function.

What can be done to power motors through wireless power transfer and how can I make my circuit work?


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Is there a standard method of detecting a stuck relay in PLC?

Say, I want to build a H-bridge using relays:

simulate this circuit – Schematic created using CircuitLab

In case one of the contacts in RLY2 gets stuck, I'd cause a very bad short-circuit, therefore before switching direction I'd want first to disengage "Enable", VERIFY that at least one contact of "Enable" has disengaged, toggle "Dir" and then VERIFY that RLY2 has switched both contacts correctly. Only then I'd switch "Enable" on.

What kind of sensors (commonly used with PLC controllers) would I use to achieve that?

Optional extra problem: PLC input contacts not rated for the PSU voltage.

EDIT:
eh, I saw the short circuit problem with my imagination's eyes, then failed to reproduce the circuit that would cause it, making one immune to this problem instead... Here's my former worry (obviously most easily mitigated by turning it into the above version...) - and yes, in this case one of contacts of RLY2 stuck would mean a short circuit.

simulate this circuit


texts: Should I isolate grounds of an isolated DC/DC converter?

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If I use an isolated DC/DC converter, when designing the PCB, should I isolate the ground of the input and the ground of the output as shown below?

I've never isolated grounds (except for AGND and DGND) but always used one single ground plane for the input and output grounds of any DC/DC converter as shown below:

Is this practice not recommended? And when is it recommended to use an isolated DC/DC and when not?

Thanks.