texts: What is the advantage of a current shunt ic versus a differential ADC across the shunt?

texts:
I'm trying to measure DC 25A across a .005 ohm shunt resistor. From my research I've found the TI INA169 which is a current shunt monitor ic. However the datasheet says it has a total output error of ~1%. At 25A, this would be .25A. I'm trying to measure to 0.01A accuracy.

With 25A through the resistor, that is 125mV. If I had a differential ADC like the ADS1115 (16-bit, 1 for sign and 15 for value), then if I had it measuring the voltage differential between the shunt would that not be a more accurate solution?

With the INA169, what is the real accuracy I could expect if I measured the output with the ADS1115 in a single ended configuration? Would it realistically be more than 1%?


texts:
My PCB includes li-on charger(3.7V) circuit with BQ25060. BQ25060 is to charge single lion battery according to datasheet.
I bought new liPo battery(1S,3.7V,1550mAh).But, There is not information about liPo battery in BQ25060 datasheet.
Is it safe to charge a LiPo battery with a Li-ion battery charger circuit?
if I can't charge, Can someone explain why?
https://www.ti.com/lit/ds/symlink/bq25060.pdf?ts=1619636089137&ref_url=https%253A%252F%252Fwww.google.com%252F


texts: Grounding A Faraday Cage On The Seventh Floor

texts:
I am working on a project for my physics class to test the resistance of various flames.

This will involve using a spark gap with high voltage and I am in the process of building a small Faraday Cage to protect the people outside from any sparks that are a higher voltage than expected, also just to keep them from having the urge to touch it.
(The logic being that people are a lot more respectful of radioactive sources when there's a Geiger counter clicking away in the background.)

  The problem is this: I need to earth the cage so that the cage itself doesn't become charged but I'm on the 7th floor and its not using a mains power source and I'm not sure what I could use as an earth.

simulate this circuit – Schematic created using CircuitLab

I had thought of earthing it to a radiator pipe, since they're grounded anyway, but I'd be worried about maybe building up charge there that passes through somebody on a higher floor or something and most other ideas I had, had similar problems.

I had also thought about connecting it to the ground of the spark generator assembly, which is not connected to the earth, but I have some strange gut instinct telling me that would be damaging to something or stop the cage working as intended.

Its very important the safety precautions I take are as good as possible because my lecturer is liable for my safety and I don't want to make any mistakes that could hurt somebody due to my ignorance.

I have done some research on grounding and Faraday Cages but I can't seem to find anything other than "Warm, wet dirt is better than cold, dry dirt" and I don't think carrying a bucket of warm moist soil up to class would be appreciated, enjoyable to do, or even work that well as a ground because I can't find anything on exactly how much soil is needed to qualify it as a good earth.

  NOTES: There are earthed outlets. I am from Britain if that's important. I wasn't sure if I could just remove the live and earth cables from the plug and use it solely for its ground pin as I am more familiar with electronics than building wiring.

  The cage will be approx.  42x30x23 cm

  The cage is totally bare steel wire, not painted.

  The frequency of the AC spark is approximately 70Hz with a rise time of approx. 50us

  This assembly and the experiment will be on an insulated base raised from the table by bricks.

  The length of arc will be approx 3cm but it will be passing mostly through the flame, not air.

  The voltage will be on the order of 3kV and I cannot tell you what the current limit of the source will be until I can have a look at the specs for the source, which is approx 30 miles away right now.

Thanks for reading.


texts: What to plug in first to usb charger when charging: wall outlet or cell phone and why?

texts:
I asked this question on Physics StackExchange but was advised to ask it here.
When I charge me cell phone or notebook or whatever device what should I plug in first? Should I at first plug in usb charger to the AC wall outlet and only then to the cell phone or vice versa? What are the precise physical arguments for this? And are there any differencies at all?
I think it is safer to plug in wall outlet first because of peak charge. Can someone give me a technical explanation?
Thanks in advance.


texts:
I am using bayangtoys X16 GPS drone.
I managed to solder the "alfa APA-M04 7 dBi gain RP-SMA directional panel antenna Wi-Fi" on the board, and it was working absolutely fine. Until, I put hot glue on the antenna's solder to make it more solid.

Since then , when I power on the remote the red light comes on for a second and beeps then it goes off. I removed the hot glue and still its doing same thing..

(That glue near the LED is factory set, it was there since the beginning)

1)I have checked for any short on the antenna's ground and main wire, there is no short there. I have checked the battery and power, and all looks good.
2) Battery are tested for voltage and working fine.
The board is receiving proper voltage from the battery, I tested the voltage on the board as well.

Could anyone help me out please!

Link to video explaining the issue Video


texts:
I been hunting for an equivalent for a Diode in TV Power Supply - its a FMXG26S. Does anyone have any idea of an equivalent? Or where I can look one up? The datasheet advises the following for the device:-
https://www.semicon.sanken-ele.co.jp/sk_content/fmx-g26s_ds_en.pdf

Transient Peak Reverse Voltage - 600V
Peak Reverse Voltage - 600V
Average Forward Current - 10A
Peak Surge Forward Current - 100A

All help greatly appreciated!


texts: Examples of fluid (including air) being used to transmit digital data?

texts:
We usually use electrons to communicate data across wires, and sometimes we use light also.  Does anyone know of real world example systems that use fluids (including air) to do this, and the advantages vs using wires? When I search for air pressure communications I get TPMS tire pressure monitoring or "how to communicate under pressure" lol.  Also, I'm not referring to the systems of tubes that carry messenger capsules with paper inside, but instead to direct digital communications via the modulation of air or fluid pressure through a pipe or hose.

I've heard of using air pressure to communicate analog process data in factories before 4-20mA was invented, but I'm not sure of the details.  Also, that's an analog technology and I'm more interested in digital data streams.

I'm sure this type of system would be slow, but could be interesting to study.

Thanks for any info!


texts: 555 timer with output voltage equal to 5V?

texts:
I am (still) learning about electronic and want to get a 555 timer. From a datasheet (page 5) it looks like when the input voltage is 5V, then the output voltage is only 3.3V.

Is that correct?

If this is correct, are there any 555 timers (or similar) that will operate on inputs on about 5V and give outputs also 5V

(or just the same as the input)?


texts: I needed to find the impulse response of the low-pass RC filter described by the differential equation and the output

texts: If someone could check it, that would be great.


texts: Why aren't vehicle mounted generators grounded?

texts:
To clarify, I'm thinking specifically of PTO-driven generators on fire apparatus.

It would seem that they are grounded (Earth ground - not floating) when connected to a hydrant and their hoses are filled with water - but there are no guarantees that an apparatus will necessarily be connected to a hydrant when its generator is running. (The generators often power lights on the apparatus, as well as electrical outlets for tools.) If an apparatus were not hooked up to a hydrant, it would be electrically isolated and floating.

Given it is common practice to drive a ground rod for portable generators, why are apparatus mounted ones not grounded?


texts: How do I design a circuit to allow for two power supplies of the same voltage?

texts:
I am currently designing a circuit which utilises a 18650 battery which passes through a TPS63000 buck-boost converter, converting the voltage to a steady 3.3V. I require the circuit to interface with an FTDI board occasionally, where the FTDI board supplies 3.3V to the circuit, allowing the board to function with the battery disconnected.
I would like to know how I would design the circuit so that plugging in the FTDI's power pins would not damage any components. I have seen suggestions for Schottky diodes being placed in series with both the buck-boost converter and the FTDI's 3.3V supply, however the forward voltage drop would likely be too great for the microcontroller to be powered (STM32).
I would appreciate any help on the matter, even if it was to tell me I was missing something blatantly obvious .
Thanks again!


texts: Logic circuits use current source or voltage source?

texts:
Main question: Do logic circuits use a current source or a voltage source? My assumption is that they use current sources because the standard is to use voltage as the indicator of input and output values (usually 0V and 5V).

EDIT: There appears to be some confusion about my understanding. So here are my assumptions:

I am assuming Ohm's law V = IR, meaning that with a constant current (current source), resistance controls voltage, but with a constant voltage (voltage source), resistance controls current.
I am assuming that (approx) 5V output/input means the bit is a 1 and (approx) 0V output/input means the bit is a 0.
Circuits change the voltage, by 1) using resistors to control the voltage range of the power, inputs, and output directions, and 2) using voltage controlled transistors to control the actual logic.

Secondary questions:

If a current source, then would it be safe to assume that using a battery or a 5V/10A power supply (usually voltage sources by my understanding) would be a bad idea with standard logic circuits?
And what would the amperage of a good current source be for a logic circuit?


texts: Simple Node Analysis - Is the given answer wrong?

texts:
I'm doing some homework sheets, and I just wanted to know if the given answer to this problems is wrong:

I'm getting V0 (the node) as 144v and the current ia as 48A, I just wanted to confirm if the error is in the question, or if it was me who went wrong:

Here is my working out:
$$
\frac{6I_a-V_0}{3} = I_a
$$
$$
I_a = \frac{V_0}{3}
$$
Then doing KCL at node V0, treating the node below the 24ohm resistor as ground, and subbing in Ia gives:

$$
\frac{V_0-60}{2} + \frac{V_0}{24} + \frac{V_0-6I_a}{3} = 0
$$
$$
\frac{V_0}{2} - 30 + \frac{V_0}{24} + \frac{V_0}{3} - \frac{2V_0}{3}  = 0
$$
$$
\frac{5V_0}{24} = 30
$$
And then then gives V0 as 144V and Ia as 48A.

Thanks guys!


texts: How to test insulation of an unarmored, buried cable with mega-ohmmeter?

texts: I have 3 single 1000V rated cables that have no armor and there is no ground reference (they are in a trench in the middle of the field). Usually I do phase to phase and phase to ground for each conductor. But because I don't have ground point, I only did phase-to-phase. Does phase to phase value tell me something if the insulation is defective ?


texts: when should I use a tuned amplifier circuit compared to a LCR bandpass circuit?

texts: I am reading Microelectronic Circuits by Sedra and Smith. When should I use a tuned amplifier circuit compared to a LCR bandpass circuit? The text does not explain it well.


texts: Difficulty sourcing a 6mm dc adapter/plug/converter...any ideas?

texts:
I recently bought a second power supply for my laptop. The laptop requires a 330w power supply (it runs a desktop grade CPU), which costs around £120 (Laptop is the Asus GL702ZC).  I managed to source the exact same power supply, except fitted for a different dc port/plug socket for £40, thinking it would be relatively straightforward to find a converter for it, or even a plug that I could solder on to it if need be. It's basically been impossible to find this socket. I visited RS Components in the UK and even they didn't have any of the specific plugs/converters on their database. I was wondering if anyone knows where I should look to find this plug.  I have looked on ebay and ali express,  but no luck either..

The details are:

DC Socket/plug (forgive my ignorance if these are the incorrect naming conventions - this is what it looks like:

Inside measurement 3.5mm
Outside measurement 6mm

Either a plug with these measurements or a converter for a socket for these measurements converting from:
Inside measurement: 5mm
Outside measurement: 7.4mm

Thanks in advance


texts:
I have come to the part in my construction where I suppress EMI. I just need a little help on how to select the right one.

I'm using two RT8259 switch regulators (switching at 1.4MHz) and want to suppress the switch frequencies EMI on the 24v DC input.

I can I calculate the L1 value from the switch frequency?

simulate this circuit – Schematic created using CircuitLab


texts: The proper way to store bits in JK flip flops

texts:
Currently I'm working on a contraption where when a button is pushed, it briefly creates a 4 bit binary sequence.  I want to have this binary sequence, 0000 all the way up to 1111, stored properly in 4 JK flip flops.  The problem I am having is how to properly invoke the clock and store the bits.

I would assume that I need to use the button as a clock pulse, but the problem is, if the binary code is 0000, it would be near impossible to accurately find if the button is held down, especially since I'm using pull-down resistors that hold inputs J and K to ground so that they function properly if the button is not being pushed.

Here is a diagram of what I am attempting:

EDIT: It seems to me that registers will be the way to go.  I must test some more things.

EDIT1: I've decided to not rely on the button pulses, and just sync everything using an astable multivibrator


texts: SLA Battery over-discharge protection circuit for robot

texts:
I've got a robot powered by a 12v SLA battery.  I'd like to build a discharge protection circuit to kill things if the battery dips below 11V.
In the event of low voltage, the brain of the robot (Raspberry Pi@3.3V logic levels) will turn off everything it can,  but I need to cut power to things that eat power at idle (like the Raspberry Pi itself) so the battery doesn't over-discharge when accidentally left on.
If I put a relay*** between the battery and the relevant boost and buck converters that change the battery voltage into 3.3V, 5V and 18V rails, I'm looking at switching about 14V@11 amps max or around an amp at idle when the cut-off would be needed.
Is there a low-draw circuit that can switch an 11 amp circuit?  I'm kind of lost researching between mechanical relays, SSRs, and MOSFETs as far as which wastes the least power, and am not sure the best way to trigger one of those at 11V.
I know enough to run with a general idea if I can get a general direction (I.E. Use an SSR with a comparator), but I certainly won't turn down a link to a relevant schematic.  I just don't know which road to go down.
Budget is low to moderate.  (I'm trying to prevent ruining a $40 battery)
*** I say relay here, but am totally open to whatever makes sense to do the switching.


texts: How to connect microphone mono to stereo power amp

texts:
I try to connect mono microphone to stereo power amp like this image.

I connect line of microphone to left and right of power amp input and ground of microphone to ground of power amp but it have no sound. How to fix it?


texts: AC to DC rails sag excessively when loaded

texts:
I'm just experimenting with rectifying a 120v to 12v dual winding transformer and smoothing it out two a dual rail power supply while I work towards attempting to build a clean power supply.  I realized the 12v outputs were too low for my intended purpose, so I decided to just test it out with what I had on hand while I wait for a more appropriate transformer to come and other parts.

I was trying to somewhat emulate the PSU circuit from here:
https://www.diyaudio.com/forums/pass-labs/317803-whammy-pass-diy-headphone-amp-guide.html

This is what I made with the parts on hand:

With no load, the positive rail measures at ~+11.95v after the regulator.  Okay, sounds good.  The problem is, when I put any load on it more than a few mA, it immediately sags down to a measured ~+10.8v and varies a lot around that area.

With just an LED and resistor set for 10mA current on the LED, the rail held as if nothing changed.  But anything beyond that and it immediately drops out of regulation.  The pre-regulator positive rail measures well over 14v (I believe almost 15v) and the regulator has a 2v dropout voltage, so I thought it'd be okay.

What am I doing wrong or not understanding about this? I know to seasoned EE's (I'm just a hobbyist), the capacitor and resistor values probably seem random and not ideal (it was what I had on hand), so please note that I do know the values are probably not ideal.  But, I thought it'd be plenty of smoothing through the CRCRC and work similar to the referenced circuit.

Thanks!


texts: Is a 75 KHz 12V peak signal suitable for LM324N?

texts:
The LM324n has a gain-bandwidth product of 1 MHz, so I guess it works from 0 Hz to 1 MHz, is what I understand true?

Its  slew rate is 0.5V/us which means that it can generate a 500 kHz output signal, is that true too?

If the above are both true, why when I apply a 75 kHz 12V peak signal to Vin+ with +12V DC supplies and Vin- is connected to Vout so it should work as a buffer, is the output signal destroyed?


texts:
I'm working on a 5V buck converter circuit. Below is the schematics:

The circuit is designed using the LM43603-Q1.
I put in an input voltage of 8.4V into the PCM_IN pin. I used a variable load to test the circuit. The problem is that as soon I withdraw 200mA from the circuit, the output voltage drops from 5V to 3.8V. Any suggestion for what could be causing the problem?
Thanks.


texts: Attempting to build photosensitive alarm-clock - circuit questions

texts:
I'm working on building a photosensitive alarm clock for a school project.
My supplies require me to use a DC power source, and my speaker requires an AC current. In the circuit I posted below, I attempted to do this in a two step process, where I first create a circuit that can vary its DC output based on light levels, then attempted to switch that to AC through an op-amp multivibrator.

This is the circuit I have come up with, but currently it doesn't work. For reference the top node is +12V and the bottom node is -12V. Do you guys see any glaring wrongs with what I have put together and any potential fixes that you could suggest?


texts: I am making a pitching machine that that feeds balls through a pipe into two wheels. These wheels are powered by two motors, each running at 12v and 10a., and each on their own battery. I would like them to run for around 30 mins. I do not have an arduino or anything, and am just looking to take this out and use rechargeable batteries. Can someone help me figure out what the best type of battery to use would be for this situation? Thanks


texts: How do you calculate the hourly output, measured in kWh, of a 1 kw solar photovoltaic panel given hourly irradiation data in kj/m2?

texts:
I am working to build an economic model that includes hourly solar output for solar photovoltaic installations built at several different geographic locations. I have data on irradiation (Direct Normal Irradiation kj/m2, Diffuse Horizontal Irradiation kj/m2) for each site and the location of the sites (latitude, longitude). I've followed the instructions laid out in Chapter 7 of Gilbert Masters' book Renewable and Efficient Electric Power Systems to calculate the amount of irradiation striking a given panel at a given hour, expressed in kj/m2. I would now like to use this irradiation data to calculate the hourly power output (in kWh) of a 1 kilowatt solar installation. As background, I'll use this information in an optimization procedure which will calculate the optimal investment in new solar capacity for each location to provide low-cost, reliable electricity in an integrated electricity system.

Here is a sample of the hourly irradiation numbers. Can anyone tell me the calculation to turn these irradiation numbers into kWh/kw?

Irradiation
1557 kj/m2
2591 kj/m2
1494 kj/m2
987 kj/m2

I understand that it is necessary to assume an efficiency for the solar photovoltaic installation. For the purposes of this example, could you use 16%? Also, I understand that the output I am looking for is DC output. To convert to AC I recognize there will be losses associated with the inverter.


texts: Determining physical address for logical address

texts:
I have a simple segmentation system with the following segment table:

Starting Address    Length (bytes)
660                 248
1752                422
222                 198
996                 604

Determine the physical address for the following logical addresses; indiciate segment faults.
I know the answers, but I don't understand how they were calculated:

a. 0, 198  --  858
b. 2, 156  --  378
c. 1, 530  --  seg fault
d. 3, 444  --  1440
e. 0, 222  --  882


texts: Small signal model of a forward converter operating in current mode control

texts:
By knowing that I do not know the plant transfer function of the forward converter operating in current mode control, I can be suspicious on the result provided by the following document :
https://cbasso.pagesperso-orange.fr/Downloads/PPTs/Forward%20small-signal.pdf
Nevertheless as the man who writes the document is clearly one of my master (as Yoda would be if I were a Jedi), I am pretty sure that the results are correct.
But there is something that I do not understand : the placement of the average pwm switch and the absence of the diode on the secondary side (it seems that the diode at the secondary has been placed at the primary, nevertheless how can I say that it wouldn't have influence on the transfer function result ?) :

An other point the placement of the average pwm switch depends on the type of controller : (voltage mode or current mode)

Can someone help me to understand how the pwm switch is placed ? and why one diode is missing on the secondary side ? (it seems that the diode at the secondary has been placed at the primary, nevertheless how can I say that it wouldn't have influence on the transfer function result ?)
My final goal is to simulate the plant transfer function of a two switch forward converter in current mode controller. From my side, It would be really really hard for finding the transfer function manually as there are 2 switches and a transformer ? Isn't it ?
Thank you very much !


texts: University Project - Common Mode feedback in EEG systems

texts:
Basically EEG signals (potential from brain) contain 'noise' due to EMG signals (potential from muscles). I was thinking of using the EMG as a common mode feedback prior to the amplification of the EEG signal. Thus, I would assume the EMG signal (EEG 'noise) can be removed when it enters the differential amplifier.

I am just wondering how possible this is. I am aware that EMG signals are much larger than EEG signals.


texts: How can I create a microphone preamp with a variable slew rate?

texts: How can I create a microphone preamp with a variable slew rate that is dialed in with a button and have a wide range from very slow to very fast?


texts: Lead-Acid Battery charger using LM350 and LM301

texts:
Given the circuit below, I want to discuss some issues concerning the way the circuit works.
Here is the circuit:

Let me report what is wirten in the handout:

The circuit furnishes an initial voltage of 2.5 voltes per cell at 25C° to rapidly charge the battery. The charging current decreases as the battery charges. and when the current drops to 180mA, the charging circuit reduces the voltage to 2.35v, leaving the battery in a fully charged state.
The LM301 compares the voltage across R1 to 18mv set by R2. The comparators output controls the voltage regulator, forcing it to produce the lower float voltage when the battery charging current drops below 180mA. The 150mV difference between charging and float voltages is set by the ratio of R3 and R4. The LED shows the state of the circuit.

Let's take the case of a 6V battery.
To charge that battery, usullay it is suggested to charge it with a Voltage around 7.5V (2.5v per cell as it is mentionned). LM350 or LM317 have a 1.25 voltage reference. So how do we acheive a starting charging voltage of 7.5V from this circuit (When I did my calculation I did not end up with 7.5v but more with Vref=1.25v and Iadj=50uA).

The handout says that "LM301 Compares the voltage across R1 and R2", so the OPAMP here plays a role of a comparator (The output is either High or Low), am I right?
In case I am right, how can this OPAMP be Low (sink current to allow the upper LED to be ON ) since its output (PIN 6) is taken form an emitter of a npn transistor (From the datasheet of the LM301).

How does the PNP transistor contribute to the selection of charging voltage (2.5V per cell of 2.35v per cell) ?


texts: Does anyone know about this IC/chip from and RC helicopter?

texts:
I have an RC helicopter toy (FastLane RC Pro Flight Helicopter) which I had to disassemble for fixing.
I have a chip/IC on the pcb board of that helicopter. On the chip it says 103FMTB11.

I would appreciate if someone would provide datasheet or any type of information.
Or any smd code book that provides the information which I couldn't find so far anything about it.
Thanks,


texts: Resetting of NodeMCU ESP8266 in deep sleep

texts:
I have been doing a project as my first project to learn ESP8266 applications. My project is a temperature and humidity values data logger and upload the data to Thingspeak.

The sensor used is DHT11.

I am using a NodeMCU ESP12 v0.9 board as in this image:

Connection diagram is:

The code you can see is this.

The problem that I faced is:

When it is running and the battery dies the whole system doesn't restart from the start. It remains in sleep condition, I have waited like 30 minutes thinking the nodemcu would wake up from sleep but no it doesn't.

I want to know if there is reset code that can be used or a push button or switch should be used to reset.


texts:
I've started studying basic electronics, and in this video I noticed he had a similar example as in my textbook: https://youtu.be/sTu3LwpF6XI?t=3m28s

Above is a screenshot if you don't bother to click on the link.

So, in essence.. when the switch is off, the LED to the right on. This means, there's a voltage drop across the second resistor and a voltage drop across the LED.

Now, by turning the switch on, we'll have voltage U across both first two paths. The first resistor should make sure not too much current is flowing through the base and thus, turning the transistor on. Now when the transistor is on, the voltage will be lowered to 0 after the second resistor.

Why the LED turns off at this point is because there's no (or at least not enough) current flowing through it (the potential is zero so there can't be). This should be due to the resistance of the LED itself. Or is there anything else going on here?


texts:
I have a problem given to me that states:

  Design a 4-bit Johnson counter and decoding for all eight states using
  just four flip-flops and eight gates. Your counter needs not be
  self-correcting.

I wrote my VHDL code for the 4-bit Johnson counter, but I am confused as to what it means by decoding for all eight states, using eight gates? Do I need to have combinational logic to implement this? If so, how would I implement that in vhdl?

Here is my code:

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;
use IEEE.std_logic_unsigned.all;

entity eightRC is

 port(
        CLK : in    std_logic;
        EN: in  std_logic;
        RST : in    std_logic;
        Q: out  std_logic_vector(7 downto 0)
    );

end eightRC;

architecture behavior of eightRC is
signal qs: std_logic_vector(7 downto 0);
begin
    process(CLK, RST, EN)
    begin
        if(RST = '1') then
            QS <= "11111110";       --initial state for QS
      elsif (CLK'EVENT AND CLK = '1' and EN = '1') then     --enable starts the shifting
         QS(0) <= QS(7);            --shift '0' to the left each clock edge, Q(0) gets Q(0) bit value
         QS(7 downto 1) <= QS(6 downto 0);
      end if;
    Q <= QS;
    end process;
end behavior;


texts: Why does this lithium battery have such a flat discharge curve?

texts:
I'm trying to understand some apparently anomalous observations of the discharge profile of a 1S lithium battery. I'm using this battery to run a Raspberry Pi Zero W, back-powering the Pi via the +5V pins of the GPIO header (I'm not using anything on the Pi that needs 5V). My goal is to detect when the battery needs to be recharged.
To support hot-swapping the batteries, my device includes multiple power connectors feeding its power rail. Each connector has a diode in series to prevent large current flows between batteries.
To allow the Pi to monitor battery voltage, the power rail is connected through a voltage divider to an input channel of an MCP3002 ADC, taking VREF from the Pi's 3V3. I've written some code which reads the ADC and adjusts for the divider and estimated diode drop to produce a voltage that closely matches what my voltmeter shows.
My understanding is that after a full charge the battery voltage should decrease from ~4.2V to ~3.7V, then remain steady for most of the discharge, then fall off until the cell is depleted. The actual results I'm seeing are these:

That's two trials (red and blue) with two different batteries; the solid line is a 1-hour moving average. The end of the data is when the Pi died. There is no appreciable decrease in voltage to warn of the impending cutoff.
The battery is said to contain a "protection board", and a little exploratory surgery reveals that this is implemented with a DW01 and a pair of MOSFETs in what appears to be the application circuit from the datasheet. I'm not an EE, but I was unable to find any indication in that document that such a circuit would provide voltage regulation.
I'm stumped.
Edit: It's been suggested that the Pi's regulator wants 5V, and may be causing trouble at the low end of the battery voltage. From the the Pi's schematic, the regulator is a PAM2306. Looking at the datasheet for that part, it seems like it should be happy with anything from 2.5 to 5V, and it explicitly says that it allows the use of a single lithium cell.
Edit 2: Testing @mkeith's hypothesis about VREF dropping in parallel with VBAT gave me the following data:  Because the ADC is essentially reporting the ratio between the sampled voltage and VREF, and because as they drop in parallel that ratio remains constant, the reported battery voltage remains steady as the actual voltage drops.
I think my solution is to either regulate VREF down to something that will remain stable until the battery dies (which is a pain since the PCBs are already made), or just accept that the result is unreliable below 3.65V or so.


texts: Dealing with unreliable BeagleBone pin levels during boot

texts:
I have a BeagleBone application that needs to interface with some 5V components. Unfortunately, some of the "5V components" that need to be interfaced are LEDs, so they draw appreciable current.  As a result, I can't use a level shifter with a pull-up resistor (like BOB-12009) because the voltage drop over that resistor is too high when I try to light the LED (so the LED ends up being way too dim).

I've simulated a NPN -> PNP transistor setup that seems to work OK, but here's my problem:

On boot, the pin levels on the beaglebone can be anything (though they mostly hover in the middle of the 0-3.3V range).  Since I'm connecting the BB output to a 5V relay that powers a pump, it's not OK for the pump to turn on while the BB is booting.  How do people deal with this sort of thing?


texts: Power an ornament via christmas tree light bulb socket

texts:
My dad owns a really neat star trek Christmas tree ornament that plugs into a standard bulb socket in a Christmas tree light string. It has a button that, when pushed, causes Spock to say a brief holiday message.

I want to know where I should start to be able to create my own ornament like this. I know you can get programmable chips that can play a sound clip when hooked up to a speaker, and it can be powered from a tiny battery. But that is DC, whereas light strings are AC.

Can someone give me an idea of a simple way to run something like that off of the Christmas tree light strands?


texts:
I'd like to power several 12 V @ 1A vacuum pumps (and control them via Arduino).
For a few pumps, I assume a 12 V at 3.5 A adaptor would suffice?
Also, I'm currently using a TIP31C transistor (datasheet here: https://www.fairchildsemi.com/datasheets/TI/TIP31C.pdf), but the maximum current is only 3A, so I think I'll need something else here-- any suggestions?
Here's an image of the proposed circuit:


texts: Resistive circuit analysis with dependent current and voltage source

texts:
The question in a study book says to find the current through R2. I have very little experience dealing with dependent current and voltage sources, so I get thrown off when performing loop current (mesh) analysis. Here's the work so far, but the unknown of the voltage I1 makes too many unknowns.

I then attempted to do node analysis thinking that I could find the nodes between R2/R3 and R1/R2 then do a simple Ohm's calculation (Va-Vb/R2 = I2).
I've searched the forums for similar questions, which there definitely are...but I'm not understanding how to do this since the current source is not expressed in terms of another branch current or some voltage coefficient.

I appreciate any help steering me in the right direction.


texts: Mysterious voltage drop then slows climbs back up when powered off

texts:
Ive built a simple circuit on some strip board, just a motor and a micro controller and LED and powered by 6 AAA batteries. The motor takes its power straight from the battery and the micro and LED go through a 5V LDO. I also have a slide switch to turn off the power.

The problem is when the power is turned on the voltage I measure across the batteries drop at a steady rate, about 0.01V a second, if I turn the switch off the voltage jumps up and also starts to climb back up to the real voltage across of the batteries. If I wait long enough the voltage is back to the real voltage of the batteries. If I switch it on the process starts again.

Will there is enough voltage for the LDO the circuit works perfectly so im sure there isnt a short, and from what I can see there isnt a short anywhere. Nothing is getting hot at all either. Im not quite sure what to look for or what it could be..


texts: Replacing capacitor with more than but close to farad value

texts:
I have a crushed capacitor rated at 25V 390 microfarads. My local electronics store has a 25V 470 microfarad capacitor available.
Is this a safe replacement? I believe you are fine with increasing the voltage rating, but I am not sure about the capacitance rating.
With extremely basic DC knowledge, why is this OK or not OK?


texts: benefits of removing reset in an FPGA design

texts:
The benefits of removing reset from your design are: fewer timing paths, performance and the ability to infer more dedicated hardware

Is this true or false?

I think that is false because the performance has nothing to do with fact of having/not having reset.

What do you think?


texts: CCVS (current controlled voltage source) in practice

texts:
In my current project I'll possibly need to deploy a CCVS (Current controlled voltage source). It is transconductance amplifier or converter and many manufacturers offers transconductance amplifier but in form of a VCCS (Voltage controlled current source). In practice I need CCVS with 0.5ohm (or 500mV/A). When using simulation like one in TINA it's easy: there you can choose ideal CCVS and everything works perfect: for let say 5mA of current it's "mirroring" 2.5mV.

I was playing with different current mirror topologies (with 2 to 4 transistors) and the best what I got is predictable "transfer" of 100 ohm, that means for 1mA of the current (Ibias on the picture) 100mV (Vbias). Something that seems to make things more challenging is that emitter is connected to approx. -6V (-15V + 9.1V zener) but this is another story. First I need to get a precise 0.5ohm "mirroring".
My question is how to calculate 0.5ohm current mirror (any topology) that I can use in place of ideal CCVS.


texts:
I am using CubeMX to generate initialization code for STM32F407 MCU. I wonder where  can i see the SysTick timer rate in CubeMX or its generated code?

I am using 8 MHz external crystal and set SYSCLK and HCLK to 168 MHz. What will be the rate of SysTick timer?


texts: Is it possible for someone to build a linux embedded board at home?

texts: I am wondering if it is possible to build an embedded linux board at home that has basic features like USB , serial and linux support but is powerfull enough to drive an LCD. I have looked at this tutorial http://hforsten.com/making-embedded-linux-computer.html and it is very handly but it cannot drive an LCD.


texts: What does the 3-figure code below the value code mean?

texts:
I have got plenty of capacitors which I do not know the manufacturer of. They are all marked with the 3-digit value code (for instance, "153", meaning 15×103 pF = 15 nF). There is a second code written on the components, also consisting of 3 figures (letters and numerals). I suppose they hold information about the tolerance, the rated voltage and some temperature dependency quantity, but I do not get what figure means what.

Here are the codes:

153, A5J:

104, E5M:

333, M5C:

333, YJA:

333, YKA:

So what do these codes mean?


texts: Using a NMOS as High Side Switch for 48V battery

texts:
I am evaluating IR2125 and IRS20752LPBF and IR2184 high side gate drivers to drive a MOSFET that is to be used as a battery switch for a 48V battery, the continuous current from the battery is around 25A. I have selected the IRF100B201 MOSFET for the same. If I pull up the IN pin to 3.3V or 5V will my MOSFET turn on, and if I give a logic 0 signal to IN pin will the MOSFET turn off. I am not talking about a PWM signal, I am talking about a fixed DC voltage level.
Can someone please help in clarifying my doubt regarding these gate drivers?
Datasheet Links-
IR2125 https://www.infineon.com/dgdl/Infineon-IR2125-DS-v01_00-EN.pdf?fileId=5546d462533600a4015355c85ba31694
IRS20752LPBF https://www.infineon.com/dgdl/Infineon-IRS20752L-DS-v01_02-EN.pdf?fileId=5546d462533600a401535675e709278e
IR2184 https://www.infineon.com/dgdl/Infineon-IR2184(4)(S)-DataSheet-v01_00-EN.pdf?fileId=5546d462533600a4015355c955e616d4
In my application I want the switch to always remain in on-state, i.e drive all of my electronics during normal operation, and when there's a fault microcontroller should turn it off.
This switch acts as an input to different buck converters and DC motor drivers.


texts: Why does a Tesla coil secondary need intermittent excitation to achieve resonance?

texts:
I have been reading about Tesla coils and their principle of operation - if I have understood correctly -  after the primary is sufficiently charged, its circuit is closed (by means of a spark gap or a solid state device) which much like an LC circuit generates an oscillatory circuit.
Due to the magnetic coupling between primary and secondary coils however, there's exchange of energy towards the secondary (and backwards, after the first half of the entire cycle) - the secondary acts like an LC circuit too. Since the capacitance of the secondary is low, the energy that is transferred in its entirety from the primary after some point, generates a massive voltage which can ionize the surrounding air and cause discharges.
My questions are the following:

Why does the primary have to be intermittently charged in order to cause resonance on the secondary? Isn't the primary always oscillating at its natural frequency? Why can't it be driven at that frequency by the supply transformer constantly?

Is the frequency of voltage in the secondary the same as the frequency of its excitation in the primary? What determines how fast energy from the primary transfers to the secondary and vice versa?
The Wikipedia page on Tesla coils mentions:

[...] Current flows rapidly back and forth through the secondary coil between its ends [...] The secondary current creates a magnetic field that induces voltage back in the primary coil, and over a number of additional cycles the energy is transferred back to the primary.


texts: Which equation of the Ebers-Moll-Model is correct?

texts:
I'm confused.

In different sources sometimes I find the equation

\$ I_C = I_S\cdot\left(e^{\frac{U_{BE}}{U_T}}-1\right) \$

or like wikipedia

\$ I_C = I_S\cdot e^{\frac{U_{BE}}{U_T}} \$

Can someone explain which equation is used in which case? Or is it just a simplification?

Thank you

Kind regards
Thomas


texts:
I picked up an old Toshiba MSX computer with a duff power supply.

I need: Ground, +12v, +5v and -5v.

I've picked up a 12v power supply and I thought I could use a buck converter for the +5v, but I'm at a loss how I can get the -5v and how I can complete the circuit (can I use the negative terminal of the 5v for the -5v?).

Many thanks for any answers.


texts: Three phase system represented as a vector

texts:
In multiple locations I've been seeing the following:

"Any three phase system can be defined by the vector As:

\$ A_s = \frac{2}{3}[Ax(t) + (c)Ay(t) + (c^2)Az(t)]\$

Where \$ c=e^{j\frac{2\pi}{3}} \$"

I understand this is showing the resultant of three sinusoids 120 degrees apart (from the c coefficient) but I cannot for the life of me remember where the \$ \frac{2}{3} \$ coefficient is coming from. Can anyone explain where this \$ \frac{2}{3} \$ coefficient is from? I assume its a byproduct of vector addition maybe?


texts: What do I need A0 in a USB Controller (PDIUSBD12)?

texts:
I'm reading the datasheet of the USB controller PIDUSBD12, but I can't understand what the goal of the A0 pin.

In the controller there is a data bus (D0-7) and this A0 pin, the datasheet says that the latter is used when communicating with a demultiplexed device, but if it is talking with a demultiplexed device shouldn't there be two different buses, say, D[0-7] and A[0-7], what does this pin do?


texts: Power resistor dealing with quick high current surge

texts:
I am currently working on a circuit to deal with the high inrush current of high value capacitors.

I'm calling this a 'capacitor adder' as the rest of the circuit (output load) is already powered while the caps are slowly charged over a current limiting resistor. The resistor is then shunted by a relay when the capacitors are (almost) fully charged.

Falstad Link1

My question is concerning the wattage of the power resistor as the simulator shows power consumption of over 11 watts but in a short burst of about 1.1 seconds until it lowers to 1 watt. Does this mean only a resistor rated over 11 watts is suitable? I'm thinking because of the short time frame this will not give the resistor time to warm up and so maybe a 5w wire-wound resistor may be suitable.

Any other improvement I could make?

Thank you ESE community!


texts:
I am using some stepper motors and I realized they are much slower than the stepper motors of OpenBuilds (http://youtu.be/GrjqW2MDCvM?t=3744). They're using less teeth on pulley too. Power supply voltages are same (24V) and I'm using A4988 drivers instead of their custom ones (maybe TMC).

We both using grbl, but their axis maximum rate mm/min is 5000.000 while mine is 500.000 (after 800.000 nothing seems changing for my motors but sound), their axis acceleration mm/sec is 500.000 while my acceleration can be around 30.000.

My motor does approximately 2500 steps/min and 40-42 steps in a second.

I would like to learn what's the difference between these two motors about speed?

Here is my slow motor specs: https://www.omc-stepperonline.com/nema-17-bipolar-1-8deg-26ncm-36-8oz-in-0-4a-12v-42x42x34mm-4-wires.html

Here is the OpenBuilds motor specs: https://cdn11.bigcommerce.com/s-itwgldve/images/stencil/1280x1280/products/105/3714/imgpsh_fullsize_4__22403.1539714162.jpg?c=2?imbypass=on


texts: 3.7V to 9V DC to DC boost step-up converter design help!

texts:
I need serious help choosing an IC for my project. I need a step-up boost converter to power my device from a 1000mAh or 2000mAh lithium ion battery. So far I have measured that my device only draws around 25mA when I wired in an ammeter. From looking at the data sheets and using "quiescent" current ratings, I calculated that the device would draw 62.8mA of current. Since I am using an ATmega32, I looked up what the absolute worst maximum current draw would be and found that an absolute max of 400mA could be drawn from the atmega32, but I will likely never really see that.

Based on that, I've been looking for an IC that will boost 3.7V DC to 9V DC with a max output current of around 500mA. Can someone advise me on why I am having a difficult time in finding such an IC and can anyone make any suggestions for a circuit that I can incorporate?


texts:
For the circuit above, I was wondering how they derived the formula

$$\omega_0 = \sqrt{\dfrac{1}{LC} - \Big(\dfrac{R}{L}\Big)^2}$$

If anyone is able to walk me through this it would be fantastic.


texts: Can't get a precise reading with PT100 temperature sensor

texts:
I am trying to get more precise temperature value from PT100 ( 2 wire ) sensor with Arduino.

Here's how my circuit looks like :

When the sensor is about 20 °C I get a value on A5 pin that is 432 and when the sensor is about 30 °C I get a value on A5 pin that is 440. As you can see this is a very small range ( 432 - 440 ).

I want a larger analog signal range, like from 100 to 1000.

Maybe I can somehow obtain the resistance of PT100 and with some math formula to get the temperature.

What can I do with my circuit to get a more precise temperature reading ?


texts:
I have a DC-DC converter that I want to repair. Unfortunately I cannot identify 2 SMD components from the drive circuitry. I am hoping some of you can help me identify what they are so I can have the complete schematic and find replacements.

I attached a hand-made schematic of the drive section as well as a photo of the PCB.

Thank you.


texts: Solving an inverting opamp with stability compensation

texts:
I am trying to calculate the transfer function of this circuit with a non-ideal opamp (Vopamp = -A*V-), but I don't have enough equations to solve it... I found 4 individual loops for 2 nodes (I output opamp is not useful, and I think I can still consider the bias current to be zero, but I am not sure?) so 6+1=7 equations, but I think there are 9 unknowns: Vi, Vo, V-, Vk (output of opamp), Ii, If, Ic, Io, Il.

simulate this circuit – Schematic created using CircuitLab

What am I doing wrong?


texts: how to calculate the value of current limiting resistor connected to zener on full load conditions?

texts: I know the formula R=vs-vz/Iz but is it applicable with no load condition? and would it be R=vs-Vz/IL when load is attached?


texts:
I have a few I/p transducers(which work on 4-20mA loop current) and I have made a single cable for all of them, they each have posititive, negative and Ground wires. The controller I have for these I/P transducers have only positive and negative wires. I have a few questions and would really appreciate some advise

1) What should I do with the ground wires?

2) The controller sits in a huge metal cabinet, should I connect the ground wires to the cabinet?

3) What kind of grounding should be done, is it signal grounding, chasis grounding or earthing? I'm confused about this. The symbol I saw on the I/P transducer is the earthing symbol but since this is a current loop I though it would be a signal ground.

Details about the parts:

I/P transducer used: https://www.omega.com/en-us/control-and-monitoring-devices/controllers/pressure-converters/p/IP710

V/I converter that is connected to the transducer: https://www.amazon.com/KNACRO-Voltage-Current-Conversion-current/dp/B0793MLDXZ/ref=pd_cp_421_1?pd_rd_w=61AJ1&pf_rd_p=ef4dc990-a9ca-4945-ae0b-f8d549198ed6&pf_rd_r=PAN3QRZF0ENADYC2DJ7N&pd_rd_r=4b180e82-a70a-11e9-8b3f-05565185fef1&pd_rd_wg=740lv&pd_rd_i=B0793LQZWC&refRID=PAN3QRZF0ENADYC2DJ7N&th=1


texts: Using a 0.1uF 275V ceramic capacitor for 5V LDO?

texts:
i was wondering if it's possible to use a high voltage ceramic capacitor for a 5V ldo, I also will use a 0.33uF 250V ceramic capacitor for the input.
thaanks


texts: Why do lead-acid batteries fail after about five years of operation?

texts:
I had some time ago a failure in the batteries of my UPS. The UPS periodically performs a self-test of the battery, and it failed, causing all the computers behind the UPS to shut down. The batteries were gel cells, and failed five years after I purchased them.

What is the physical/chemical reason for the batteries failing after about five years of operation? I do understand that lead-acid batteries suffer from sulfation if not kept continuously full, but in this application they were continuously full and in fact never saw a full discharge cycle.

I have adjusted the float charging voltage to be 13.65 V. Is the float charging voltage incorrect, as the batteries failed? According to Wikipedia, starting batteries suffer early damage if kept in continuous charge due to corrosion, but these are not starting batteries.


texts: Best way to switchover between 2 power supplies?

texts:
So I was trying to think of a way to make a circuit reversible across a DC-DC charger
See diagram below, it will normally be on case 1, but in some circumstances, it will be need be on case 2

The best way I can think of doing this is with 2 three-way change over switches, but would there be a better solution? What hardware should be used?


texts:
I have come up with a problem which wants to convert a Mealy machine to a Moore machine. I searched the web and found out how to convert a Mealy machine to Moore machine and vice versa, but I have other questions which I couldn't find them on the web:

What is the meaning of equivalence between Moore and Mealy machine? As you know The output of Mealy machine depends on the inputs when the input changes the output changes but Moore machine is not.
Why the conversion from Mealy to Moore is in the way described in this link?

Thank you


texts: Why do all digital signals have infinite bandwidth?

texts:
Why do digital signals have "infinite bandwidth"? Frequency is the number of cycles per second. I have seen before the formula that bandwidth = maximum frequency - minimum frequency. I remember I was told something like because of the vertical straight line for the digital signal, the bandwidth is infinite. But I still don't understand: How is the bandwidth infinite this way?
For periodic digital signals, there could still be a number of digital cycles per second, couldn't there? Then how is there a maximum and minimum frequency when the number of cycles per second is always constant throughout? Bandwidth would then be BW = Max_Freq - Min_Freq = 0.
For non-periodic digital signals, there may not be a fixed number of cycles per second, so there is a maximum and minimum frequency. But still, the bandwidth is not infinite, is it?
In both cases, how is the bandwidth infinite?


texts: What's the maximum time an interrupt service routine can take to execute on ATmega328P?

texts:
I have an ATmega328P that checks if a button was pressed via pin change interrupts. Now, I want to turn on an LED for 200 ms.
Can I just turn the LED on, wait 200 ms and turn it back off in the ISR like in the following code?

ISR(PCINT1_vect)
{
    if(PINB & 0b1)
    {
         PORT = 0b10;
         _delay_ms(200);
         PORT = 0;
    }
}

In a few forum posts on AVR Freaks, I've read that you shouldn't spend much time in an ISR, but I've never seen any exact numbers. I sadly can't find those posts anymore, so I can't link them. As far as I can remember, they all said, that if you spent to much time in the ISR, the microcontroller might crash.
Is that true? And if so, is there an exact time limit after that this might happen?


texts:
If noise on a signal is randomly fluctuating in time domain around its mean following a Gaussian normal distribution (Gaussian noise), would this be equivalent to an constant intensity in the frequency space (white noise)?
Can we somehow relate the frequency distribution to the amplitude distribution?


texts:
I have a WROOM  WIFI module ..

what are the available SPI pins taken from this IC for communicating?

DATASHEET


texts:
I have 2 PWM ports, one generates 5V PWM and another at 3V. But only 1 will be generating at a time. However, their output is going to a same wire or pin. So, to avoid the current to pass into each other, I want to put diodes on each port as protection. For this, I would need fast switching diodes as PWM frequency is KHz or few MHz. I searched for fast switching diodes and found 1N4148. It does what I need but its forward voltage is 1V. So, for 3V and 5V, it will blow up ? or am I understanding the datasheet wrong ?

I read in this answer that forward voltage is voltage drop ? so if its voltage drop, whats the max voltage that it can support ? also 3V will come out as 2V, so I will be required to level it up to 3V again, right ?

simulate this circuit – Schematic created using CircuitLab


texts:
I am trying to make an I2C communication with a device by using PIC18F26K83. I use 8 MHz MCU clock. While trying to set I2C clock these options:

Use 8 MHz MCU clock & HFINTOSC for I2CxCLK register.
Use 8 MHz MCU clock & timer 2 postscaler output while the timer configs were like below:

void InitTimer2(){
  T2CLK =0b00000101; //500 kHz
  T2CON.B3=0;
  T2CON.B3=0;
  T2CON.B3=0;     // Timer 2 PostScaler = 1:2 (500/2 = 250 kHz)
  T2CON.B3=0;
  T2CON.B7  = 1;  // Timer 2 is on
}

250 kHz MCU clock & Fosc for I2CxClk register.
250 kHz MCU clock & HFINTOSC for I2CxClk register.

And only first option worked. However, I believe all four options above should have worked. So my questions are:

Is that a correct way to set timer like above code?
When I say I use 8 MHz MCU clock, does that mean Fosc is 8 Mhz?
When they say I need to have 1 MHz frequency, should I set clock to 1 MHz or 4 MHz? Because in some sites they mentioned that one operation take 4 clock cycles in PIC. So it made me confused actually.
Is the below code a correct way to set the oscillator in PIC?

void Clk_250kHz (){
  NOSC2_BIT =1;
  NOSC1_BIT=1;      // HFINTOSC
  NOSC0_BIT=0;
  FRQ3_BIT =0;
  FRQ2_BIT=0;       // 1 MHz
  FRQ1_BIT=0;
  NDIV3_BIT =0;
  NDIV2_BIT=0;
  NDIV1_BIT=1;      // Divide 4 = 250 kHz.
  NDIV0_BIT=0;
}


texts: Understanding Thermal Characteristics for Microchip CL2N3-G Constant Current LED Driver

texts:
I'm having trouble interpreting the thermal characteristics of the Microchip CL2N3-G Constant Current LED Driver chip.
Here's the datasheet: CL2N3-G Constant Current LED Driver 1
What I want to do is to power a single LED from a 60 VDC power source.
I'm planning on using the TO-92 package.
The problem I'm encountering is when I calculate the temperature rise of the CL2N3-G.
The spec states for the TO-92 package a thermal resistance of 132°C/W.
Here's the equations I'm using:
    60 V - 2.1 V (LED Vf) * 20 mA = 1.152 W
    1.152 W * 132 (Thermal Resistance) = 158.8°C

This seems like a ridiculously high temperature just to power a single LED.
Is this correct or am I missing something?
Thanks for your assistance and insights.


texts: Programmable momentary switch for motorized desk desk leg with elcetronic stop

texts:
We're building motorised tables with 1 leg. Currently the manufacturer can only do either:

2 buttons up and down switch, that need to be pressed to start the motor and pressed again to stop the motor. This can be programmed so it does not overextend or drive down too far.
2 buttons up and down momentary switch, that only go up or down while pressed, and stop when not pressed. But this cannot be programmed to stop before the "hard stop", which makes the gears grind before the stop.

Question: I need to source momentary switches that can be programmed so we can define the maximum extension or collapse which is before the hard stop. Our supplier isn't able to find those
Any ideas?


texts:
I have been reading this application note from National and I have a question about this phrase:

  ... traces carrying switching currents/voltages must also
  be kept away from ’quieter’ traces to avoid crosscoupling. ...

How many mils should they be away? Does this distance change with the current or voltage? Does the flow of current, voltage affects 'Quieter' traces?


texts: Stored energy (and others) of RC circuit

texts:
In a circuit shown below me and a friend of mine discussed how we could calculate this.

simulate this circuit – Schematic created using CircuitLab

He simplified the circuit by stating the resistors and capacitors are in parallel, and hence it can be simplified to a capacitor of 17 farad and a resistor of 142k ohm.  So energy stored would be: \$ \tfrac{1}{2} CV^2 = 0.5 \cdot 17 \cdot 36= 306 J\$
I thought this was wrong, and one could simplify the circuit to 3 "parallel" rc-circuits, each consisting of a 47k ohm resistor, 50 F capacitor and a 6/3 = 2 V dc supply. So total energy that could be stored is:
\$3\cdot\tfrac{1}{2}CV^2 = 1.5 \cdot 50 \cdot 4 = 300 J\$

What is the correct approach, or should a complete different method be taken?


texts: Could a blown voltage regulator still supply electricity?

texts:
(I'm new to electrical engineering, both the website and the topic, so don't hesitate to correct me)

I'm building a very tiny form factor transformerless power supply with 5 V output.

I was wondering if I could use a voltage regulator as a fuse so if one of the cap or resistor fails and the circuit starts outputting something like 230 V (more than desired volts and more than rated limit of voltage regulator), the voltage regulator will blow and stop the current from passing.

I've heard that normal fuses are temperature sensitive that's why I want to use a voltage regulator as a fuse.


texts: How do I create the perfect PCB mask everytime?

texts:
After wasting money, I learned that I can develop and etch PCBs but the artwork is a problem.

Today I bought premium transparencies (made by MG chemicals) specifically for laser printers. I own a brother laser printer.

I did two printouts and made use of the full page as I am doing multiple circuits in one go.

I tried thick paper setting, and the printer took time to print. I tried thin paper setting and the printer printed super fast. In both tests, the image seem to have shrunk horizontally by a few percent (I couldn't align a 40-pin DIP IC onto the holes in the mask and my circuit requires a 40-pin DIP IC).

In the past I tried vellum (equivalent to 120gsm tracing paper), and it also does not work for large circuit boards because the result is not solid (PCB in the end looked patchy and the only way to use it was to redo the board with solder tape?).

I did read somewhere about transparencies shrinking when going through a laser printer but I wasn't expecting MG chemicals transparencies (that even indicate online they are heat stabilized) to shrink the image.

Yes I have done the obvious of making sure I'm printing at a 1:1 scale and I didn't do anything in software to cause scaling to happen.

It seems that my only options are these:

Run to a print shop for every printout (which is a pain).
Ditch my printer and find an older one.

If I choose option 2, should I go with inkjet or laser and why? and what brand should I go for?

The thinnest track width for all my boards is 10mil.

EDIT: I increased the margins to make the printer driver happy but I still get the same disappointing results of the image not to scale.


texts: How to keep current from draining out the bottom of this push-pull amplifier?

texts:
In an earlier question I asked about driving a speaker with a BJT transistor. @Jonk offered a push-pull amplifier design of his own, and @G36 noted its similarity to the JLH amplifier described in a paper from 1969.

In 1969 NPN power transistors were easier to come by than PNPs, so the JLH amplifier, and @Jonk's amplifier, use two NPN transistors instead of an NPN and a PNP. This is interesting to me because I'm trying to understand tube guitar amplifiers, and tubes are more or less NPNs. (I know they're more like FETs, but my point is, there are no PNP-like tubes.)

Using two NPNs requires a third NPN to act as a phase splitter. I've set this up, and it works fine:

simulate this circuit – Schematic created using CircuitLab

The base of Q1 is biased to about 6.7V (give or take). The input swings +/-5V because it is the output of a previous voltage-amplifying stage. With no signal the emitter is at 6V and and the collector at 18V, giving plenty of room the voltage swings.

The problem is that when I attach the power NPNs, there is a zero-resistance path between the base of Q1 and ground, and all the current drains out. :-(

simulate this circuit

How can this be made to work? All the examples I've seen have the emitter of the "bottom" NPN (Q3 in this case) connected to ground. But that means its base will be at about 0.7V, and the base of Q1 will be 1.4V, and they will not be able to swing +/-5V, or at all.

In the JLH and @Jonk amplifiers, there is a PNP upstream of the phase-splitter transistor that I suspect has something to do with the solution, but just can't figure out how it works.

UPDATED: Added a decoupling capacitor in front of the speaker.


texts: How to find the right smoothing capacitor for rectification circuit

texts:
I am creating a power supply which will need to convert the 24vac to 5vdc. I am thinking of using a rectifier to convert ac to dc, then a capacitor to smooth out the voltage, then an LM2596-5 to drop it down to 5v. I am having trouble with selecting the right capacitor to smooth out the voltage. I saw this formula to find out the capacitor value

Current * Half Cycle time / acceptable voltage drop *1000 = C uf

When I plugged in my values

2 * 8.3 / 1 * 1000 = 16,600 uf

As you can see I get a ridiculous number and this guy has used a 100 uf cap on his 24vac to 5Vdc power supply. My use is a smart thermostat that I am making. my max current that my setup takes is 1.4a but my rectifier is rated for 2a so that is why I am doing 2 amps. I am mainly confused on how the formula is giving really large numbers and why that guy happily chose 100uf

The Formula I got is from this video


texts: Capacitive touch sensor senses every materials touch

texts: I have a ttp223 capacitive touch sensor. It has three pins, VCC GND and I/O. I left I/O open for test purposes. I connected the VCC to 5V and GND to ground. When I touch the sensor, its led indicator lights up, sensor works fine. I wanted to see if it works through wood because I want to make a touch sensitive wooden surface controlled by arduino. When I brought the wood closer, without even touching the corresponding area with my finger on the wood, sensor lights up.I tried touching the sensor with various materials including plastic and it still lights up. It detects every touch from every material. Obviously I dont want this. How can I solve this?


texts:
Is there a way to send GPS coordinates from one device to another, without the use of any kind of cell service?

What I'm attempting to design is a device that connect to a motorcycles' tip-over sensor, that can send some sort of SOS message to a pre-determined contact (phone number, email address, web server, etc) in the event of a crash. The problem is that often times, the places we motorcyclists ride is not within cell reception. I've found a lot of information on how to build GPS tracking devices, but they seem to all require an internet connection or cell service. So it'll have to be a satellite transmission of some sort, I think.


texts: Why does radiated emission of a PCB decrease as the frequency of the signal increases?

texts:
I was just reading Henry Ott's book "Electromagnetic Compatibility Engineering" and chapter 16.3.3 where he discusses how changing reference planes is detrimental to EMI.

Quoting from the book:

  When a signal trace changes from one layer to another, the return current path is interrupted because the return current must also change reference planes

which he explains increases loop area and radiated emissions.

Then I then came across this statement:

  At 247 MHz (diamond marker in Fig. 16-9B), the emission is almost 30 dB greater for the case where the signal transitions from the top to bottom layer, versus the case where the signal is routed on a single layer.

That is in perfect accordance with the previous statement, but:

"Above about 2 GHz, the interplane capacitance is sufficient to reduce the impedance of the return path, and hence, the radiation in both cases are about equal"

And indeed by observing the graphs, above 2 GHz emissions in Figures 16-9 A,B are approximately the same.

So my question is:

Does designing for frequencies above 2 GHz have less restrictions, in that you don't have to take such issues as changing reference planes into consideration? That would be counterintuitive to what I've considered so far about higher frequency signals and how they are more susceptible to EMI.

Thanks


texts: Help with designing falling edge detector using a state machine

texts:
Using a state machine, I designed a circuit that detects the falling edge of a signal (working with positive edge clock), but my circuit has one more not gate than the circuit shown in this document:

https://www.cypress.com/file/133046/download

Here is what I did:

Drew the waves, with trig being the input signal and pulse being the output signal.

Drew a mealy state machine.

Made a table which describes everything:

Wrote the Boolean expressions for Q_next and pulse (a karnaugh map was not necessary for pulse).

And finally, the circuit:

I also wrote a VHDL code and a testbench and I see it is working (will attach if necessary, don't want to make the post too long).

So, this works, but I think one big mistake here is that I'm assuming the signal trig starts at '1'. I mean, if it were to start at '0' (and my initial state is S0), then pulse would be '1'. But, if I were to add another state, it would add a second FF.

So, what did I do wrong that I have an extra not gate?


texts: ARM CPU burning hot within 30s after voltage regulator failure

texts:
I have an STM32F3 DISCOVERY board (3V CPU, http://www.st.com/web/catalog/tools/FM116/SC959/SS1532/PF254044), and I accidentally dropped a 25V lead on a wire that I didn't think was connected to the board, but the board, being powered off USB, stopped working immediately.  After testing, I found that applying any voltage to the regular would not power on the board, but if I applied my 3V wall wart directly to the chip's VIN, bypassing the regulator, then it would still turn on, and could even be programmed via USB.  However, within 30s of turning it on via this method, the CPU becomes burning hot to the touch.  I have other identical boards, and they do not do this, even when bypassing the regulator.

The CPU's datasheet (http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/DM00058181.pdf, page 57)

claims it can operate at anywhere from 2-3.6V.  I measured my power supply before connecting it, and it read 3.1V.  (after connecting it I read 2.6V)  I also tried powering it via AAs, with a combined voltage of 2.4V, but it heated up just the same.

Basically, I'd like to get it working stabily again.  Looking at the schematics (http://www.st.com/st-web-ui/static/active/en/resource/technical/layouts_and_diagrams/schematic_pack/stm32f3discovery_sch.zip)

it seems that the regulator is outputting 2.96V (measured on another, working board), which goes directly to the chip, so I was hoping that using an external regulator (like http://ww1.microchip.com/downloads/en/DeviceDoc/22001c.pdf, but I'm open to suggestions) hooked to the 3V could fix it, however since I'm applying voltages that are supposedly within normal operating conditions to it already, I'm not sure if that could fix it.

Can anyone explain why it's getting so hot?


texts:
I'm working on a PIC32 design and am looking at the power supply. Currently I have a solution in mind as below.
12V -> MBR360G (Schottky Diode) -> MCP1584en -> 5V -> MCP1726 -> 3.3V
But looking at some of the development boards from Microchip, they also add a current limiter like MIC2005 or similar. What is the best practice here, is this needed and what is the main purpose? Short circuit protection or more for the ability to enable power once stable? The 3.3V consumers on my board is really just the PIC itself and a very small number of low power consuming ICs.
The MCP1726 already has some level of short circuit protection, albeit maybe not as good as a MIC2005.
Hope to hear some thoughts on this.


texts: Input Resistance: Why can you ignore current sources?

texts:
This may be a weird question, but I simply can't figure out, why you can entirely ignore current sources when calculating the input resistance of circuits.

Here is an example (it's actually a small-signal model of a BJT-circuit):

simulate this circuit – Schematic created using CircuitLab

When you want to find \$R_{in} = \frac{V_{in}}{I_{in}}\$ you end up with \$R_{in}= R_a\,||\,(R_b + R_c)\$ (at least that's what the sample solution sais).

However, intuitively I was thinking: When there is a lot of collector current flowing around, with \$R = U \cdot I\$ the resistance will go up. And only when there is almost no collector current left \$(I_C \to 0)\$, I was expecting:

\$R_{in} = \dfrac{V_{in}}{I_{in}} = \dfrac{(R_a\,||\,(R_b + R_c)) \cdot I_{in}}{I_{in}} = R_a\,||\,(R_b + R_c)\$.

But obviously that is always the case. Can anyone explain to me, what I'm missing here?


texts: Can the inrush current of a DC motor powered by a battery affect/damage other devices conected to the same battery?

texts:
I have a small differential drive vehicle that has two 24V 400W DC motors, powered by two 12V batteries connected in series. I am planning to attach a UST-10LX scanning range finder at the front of the vehicle, so I can implement some obstacle avoidance algorithms. The voltage operation range of the sensor is from 10 to 30V, ripple within 10%.

I would like to know if it is safe to connect the sensor to the batteries without any protection circuit, or if the current drained by the motors could possibly damage the sensor in any way.


texts: Emitter resistor in BJT differential amplifier

texts:
I'm currently studying the three modes of a BJT differential amplifier, and am struggling with some hypotheses the textbook makes.
When examining single input and double input, the author uses a model like the one below, and goes on to an AC analysis of the circuit.

simulate this circuit – Schematic created using CircuitLab
While applying KVL from V1 to V2, they attempt to simplify analysis by stating that 'we choose a very large emitter resistor, almost infinite' without further explanation, and they end up with the formula for the single input DA.
$$
A_s = \frac{V_o}{V_i} = \frac{R_C}{2r_e}
$$
However, when doing the AC analysis of the common-mode DA, the emitter resistance shows up in the formula
$$
A_c = \frac{V_o}{V_i} = \frac{βR_C}{r_i + 2(β+1)R_E}
$$
The author omits further diagrams, by saying we 'apply a similar logic'. What I struggle to understand is, why is \$R_e\$ suddenly not infinite, and we take it into account in common-mode?


texts: STM32 ADC and timer(s): Measuring moving average peak voltage of PWM signal with varying amplitude

texts:
I want to measure a moving average of the amplitude of a fix frequency, fixed dutycyle PWM signal with slowly varying amplitude but in a noisy environment (DC motors).

I want to use as little as possible CPU power to do this and have the ADC do this for me. I have an internal signal coming from a timer that is in sync with the signal to measure. I can use this as a trigger.

Below is what I try to do:

use the internal trigger from the timer on the chip that actually generates the PWM signal
wait 1/4th of the onPeriod before taking any samples to filter out rising time or overshoot
then take N samples and filter out noise by taking the arithmetic average
keep a constant moving average of the M past cycles (3 in the drawing, 100 in reality)
Store this result in an ADC register such that the application can always retrieve the last 100ms average

So far, I figured out 1 (interconnect of timer output channel and ADC external trigger) and 3 (oversampling) by reading the reference manual and think I can do 2 by using a basic timer inbetween first timer output and ADC. But I completely struggle with 4 and 5.

Can this be done? I am using STM32L4 and F4/7.


texts: Do standard NiMh AA or AAA battery's have any kind of BMS or protection circuit built-in?

texts: Do standard rechargeable NiMh AA or AAA battery's have any kind of protection circuit like over discharge? Or are there any circuits out there that do that kind of stuff? I want to power my Arduino Nano with two AA battery's. Any suggestions? Do I need extra protection circuits to prevent any damage to the battery or do they shut of themself when they reach the 1v mark?


texts: Terminal vs induced voltage for a transformer with respect to the voltage rating

texts:
Suppose we have a 2200/220 V non-ideal transformer.
Based on the image below of a non-ideal transformer, would 2200V be the primary terminal voltage (V1) or the primary induced voltage (E1)?
Similarly, is 220V the secondary induced voltage (E2) or the secondary terminal voltage (V2).
If neither, could someone explain what this rating is about?
I came across this explanation in my search, that this means that if 2200V is applied to the primary winding, then 220V is induced in the secondary. Now, my understanding of "applied to the primary winding" refers to the primary terminal voltage (V1) rather than the primary induced voltage.
I am really confused about this voltage rating for the transformers and any information is welcome.


texts: Calculate number of photons of a light source given the lumen and the color spectrum

texts: Is there any program that given the lumen and the colour spectrum (relative intensity at any wavelength) of a light source and it outputs the total amount of photons per wavelength?


texts:
I would like to control AC universal motor (brushed). I would like to know the load torque, but I cannot measure the torque directly. I have to calculate it from motor parameters. Please let me know what parameters I have to measure to calculate the load torque of the motor.
I have seen that the running motor current changes when the motor windings is heating.
What kind of parameters I have to sense:

Current
Voltage
Speed rpm
Temoerature
?

What about an equation: Torque = Power/Speed (T=P/ω) ? Can I use this relationship to calculate load torque?


texts: Printer Data Cables with *suspected* IC boards

texts:
I've one found of those printer data cables that have some kind of pair integrated circuit along them, one at each end just before the plugs, I was wondering if there is a less invasive way of determining the specs for them other than slicing their enclosure.

I'm sure it will be fine in doing so, and I know I'm over thinking this just a tad but I just feel uncomfortable with a pair of IC that isn't detected by windows, and if it were some kind of spying boom doogle it would probably have some kind spring/pressure based mechanism that wipes the microcontroller's programming or something of that nature

complete novice in this field apologies for any misuse of terminology and or incorrect terminology.


texts: Flyback 120-240VAC to 3.3VDC ripple and simulation

texts:
I'm working on a project requiring a 3.3VDC and eventually a 12VDC. The input voltage could be either 120VAC or 240VAC 60Hz.
I've found and replicated the design PMP10143 proposed by Texas Instrument with only the 3.3VDC output part for now. Here is the current schematic :

The current issue is the ripple that is pretty high :

Now wondering if there is something wrong with either the design transfer or the original design. Also, for test I tried to recreate a simulation, but can't find an opto coupler to recreate it.
Help about the ripple source and/or the circuit simulation would be greatly appreciated!


texts: Avoiding crosstalk between makeshift wires

texts:
My setup is as follows. I have 6 foot long 22-gauge wires connecting pin headers of an audio codec eval board and an FPGA daughterboard. I am sending an 8KHz and 128KHz clock signals and a data signal that changes with the fast clock. At present all I've done is loopback the signals from the audio board into the FPGA back to the audio board. I can do this same loopback bypassing the FPGA and the signal integrity is fine. The problem is when I route through the FPGA. At the output pins at every fast clock transition there is significant noise on the slow clock, so much so that it sometimes changes logic level. How do I isolate these from each other effectively? Thes pins on the daughterboard are currently right next to each other. Would moving the pin assignments make a difference or would it not matter because the wires will still be next to each other?

Thanks for any advice!


texts: Why can't you use the ground of a second DC power supply as a return?

texts:
This is probably a really silly question, but I can't seem to find the answer anywhere.

Say I have two totally separate DC power supplies running from AC power, and another piece of equipment that requires 12v DC. Why is it not possible to take 12v from one supply, to the device that needs powering, and then take the return to the ground on the second supply? What is it that stops the current flowing?


texts: Noise generated by monitor from Word document

texts:
I was zooming in and out of Word documents of only text and noticed that a noise was produced. The noise increased in pitch as I zoomed out and decreased as I zoomed in. I tried changing the font colour and the same noise was heard.

I thought it had something to do with the contrast of the font colour and the white background, so I created the following checkerboard pattern and zoomed in and out of it and was unable to produce the noise:

I have a 2014 MacBook Air which is connected to a HP Z22i monitor.

My adapter setup is as follows:
Thunderbolt (non-genuine adapter) -> HDMI -> DVI

Here is a link to a video of a Word document being zoomed in and out of. You may have to turn up the volume, it is fairly quiet.

Would you know what is causing the noise and why it increases in pitch as there is a greater percentage of white shown?


texts: USB hub with power delivery OR android accessory mode

texts:
I'm looking for a USB hub solution for small host computer (like a Raspberry Pi or Nexus tablet) that can simultaneously power/charge said host computer.

I've heard about the USB power delivery specification, but I can't find USB hubs that implement this.

I've also seen the Android Open Accessory Protocol. I don't think it's possible to program an Android Accessory to appear as a USB hub to the Android device, but feel free to prove me wrong.

Since I can't find any existing implementations, I'm going to implement it myself, on a PCB. Is there any specialized circuity involved in wiring a microcontroller (as a USB HUB) that provides Power Delivery?

Alternatively, I'd take a PIC/Arduino project that implements a USB Hub with power delivery, as a starting point.

Edit: pertains to Power Delivery circuitry.


texts:
Are phy transceivers like Ethernet phy, Wlan phy and USB phy transceivers digital or analog in nature?

I referred to datasheets but it just shows transmitter and receiver as a block diagram, hence the query.
Thanks in advance.


texts: Finding 74hc595 alternatives with the same timing- how to read datasheets?

texts:
I am a tinkerer trying to find a higher power alternative to the sn74hc595 and my search brought me across the tpic6b595. From googling around a bit I found that the tpic6b595 should work with the existing arduino library. That's fine and I am willing to accept that, but how would I be able to come to that conclusion by looking at the data sheets? I am sure it has something to do with timing, but I keep staring at the datasheets and can't really find any patterns or anything to work with. Can someone help me out or point me in the right direction?

http://www.ti.com/lit/ds/symlink/tpic6b595.pdf
http://www.ti.com/lit/ds/symlink/sn74hc595.pdf


texts: Cheapest, simplest way to implement a Bluetooth keyboard/mouse?

texts:
Thinking of building a device for sending text and probably mouse movement into a computer, but I want it to be wireless and compatible with many computers/PDAs/phones without a specialized dongle, etc.  So I thought "Hey, Bluetooth is a standard for input devices and lots of computers/PDAs/phones have it built in!"  But how to get the data into the Bluetooth on the other end?

I could buy a Bluetooth
IC and build a PCB for it, but I
can't even find a place to buy them
in small quantities, or find documentation without being part of a company and signing NDAs, etc.
I could learn the
very popular Arduino with the
Bluetooth adapter, but this
would cost $149.95, which is not what I had
in mind, and I don't know if it can even act as a keyboard/mouse.
I could buy a cheap USB
keyboard and take it apart, figure
out how the keys map to the data
lines, and just stimulate them
appropriately.  Mouse is not so easy,
though.

The last seems like the best, but do you have any other ideas?

I do not want a generic serial-over-Bluetooth board, unless it can be configured to look like a standard Bluetooth keyboard/mouse at the other end.


texts: Standards for colour of conductors of pre-assembled cables

texts:
We are designing a product for industrial energy storage systems. Multiple units are connected with pre-fabricated cable assemblies of 2-4 separate leads that are terminated in  connectors unique to our system, similar in concept to these:

Now, for branding purposes, we want to use our company‘s colours for the leads in these cables. Some of them conduct high voltage and current during use.

For now, we are looking to only sell this product in the EU.

I found a few norms regarding single leads and screw terminals in machine building, where only certain ways of marking cables are allowed, and standards for mains AC cabling, but nothing that explicitly talks about pre-fabricated cables.

How can I find out whether custom colouring of cables is allowed in the field our product will be used in?
Is this sort of thing maybe common practice in the industry?


texts: How can I get a fixed collector current from S8050?

texts:
I am trying the following circuit as a part of a project. The goal is to turn on and off the transistor, S8050 (datasheet) at a certain time interval (say 1s), and read the value of the collector current (Ic). I am controlling the base voltage of the transistor using ARDUINO PWM. When my transistor is off I am getting zero Ic current which is fine. But when I turn the transistor on the IC current is fluctuating from 19mA to 45mA. My question is how can I get a fixed Ic current?
I tested the circuit putting base voltage 0V and at that time Ic is Zero. Also, put the 5V to the base and got 33mA. This fluctuation arises when I'm turning ON and OFF the transistor using the PWM.
Thanks for your time.


texts: magnetizing current - which value must be chosen?

texts:
Sometimes in app notes i see something like @assume that magnetizing current value is 10% of the primary current".
Why? How to choose the magnetizing current value the right way?


texts: Output resistance with no lambda SPICE parameter

texts:
I have a simple current mirror and am trying to find the output resistance in OrCAD. Somewhere I saw: $$R_O=r_{ds}={1\over g_{ds}}$$ Using this formula and the SPICE bias file, I get a theoretical output resistance of \$22.17 k\Omega\$. I then gave my output an AC voltage input of 1.5 V (the assignment asked for this specific number, I'm not sure why), ran an AC sweep, measured the output current as 63.49 uA, divided the two, and got \$R_O = 23.625 k\Omega\$, really close to my original theoretical value. However, when I went back to check the equation, I couldn't find the one mentioned above, but instead found the following one:  $$R_O = r_O = {V_A\over I_D} = {1\over \lambda I_D}$$

Which is all well and good except that my SPICE file I'm using for my MOSFET has LAMBDA equal to 0.

How do I know how SPICE/OrCAD is handling Early voltage/channel-length modulation when there isn't a parameter to do so?

Edit: Additionally, if the SPICE model has no \$\lambda\$ parameter, what should I use in my hand calculations to estimate \$r_O\$?


texts: Is it okay to connect a European 240V transformer to a US 240V outlet?

texts:
I've an old Bosch German made automotive charger transformer with ratings 14V/9V, 220-250V @ 50/60Hz 132VA. Can I use it on the 220 to 240V outlet here in the US which uses a split - phase system as the transformer was intent to be used on Europe style 240V with a Live and Neutral system?
Will there be any difference in its performance?

Note: I'd initially asked this question in the comments section of "How is the 220V line in US different from other parts of world? Does a US 220V line need two switches for each wire?". But has been removed by moderators and was asked to make separate thread so this info is seen by everyone.Thanks.


texts:
So I'm considering different antenna shapes to most effectively detect electric field component of far-field VLF waves. I saw some papers that used this method but couldn't find any broad explanation on its electrical design.

I know for a transmitting antenna the impedance of the antenna should be purely resistive(resonant frequency). However, I don't know if that's the case for also a receiving dipole antenna. If it is, then can dipole antennas be used for detection of waves at VLF since it would be practically impossible to build a half-wave dipole at such low frequencies?

So should a receiving dipole antenna also have resistive impedance or is there a way around this?


texts:
I'm trying to read a graphic LCD, it seems to have 128 x 64 dots. It communicates with an ARM STM32F103 via SPI. I intercepted the communication between the LCD module and MCU, and decoded part of the communication.

I would like to know: How can I discover the model of the LCD controller that this LCD module uses?

I need to read it, so, I need to know which controller it uses and which pins are available in the flat cable connector.

Does someone have a tip, or any advice?

Here are some pictures of it.

(click for larger images)


texts: Is PIC running at 3.3v, 5V logic tolerant?

texts:
Can a micro-controller that is capable of running at voltages ranging from 2.3 to 5.5 V, tolerate 5V logic levels while operating at 3.3V?

I need to interface GPS (5V) and raspberry Pi (3.3V) with my microcontroller. Don't have access to logic level shifters.

I am talking about PIC18F46K22 if that makes any difference.


texts:
Why theoretically the higher voltages do not generate the bigger losses  voltage is the amount of electrical potential energy that each coulomb of charge has, so then independent of the current when each such coulumb passes through the electric resistance left out more of its potential energy  and a higher voltage drop.

This my question is primarily based on the distribution of electricity.

And I know what generates losses in the distribution network  I'm interested
 me why the higher voltage does not produce any greater losses because every colomb of carge possesses more potential energy.


texts: Replacing selenium rectifier diode with silicon 1N4007

texts:
I want to replace this selenium diode on an old tube amplifier with a silicon equivalent. Normally, this diode would have a lower value resistor in series with it such as a 15 ohm. Instead, this one has a 15K ohm resistor, only having about 20mA of current going through it. Is it safe to say, in this case that I can simply do a swap of the selenium for a 1N4007 and not worry about adding more resistance?
From what I've read because the voltage drop of a selenium is higher about 7-10V, and the 1N4007 is only 0.7V, you would need to add a small resistor such as 100 ohm in series with it to achieve the same voltage drop and get the same voltage in the circuit as before.
Thanks


texts:
I have an STM32L476 Discovery Board. I'm trying to generate a PWM signal on the GPIO pin PE14 using TIM1_CH4 using bare-metal in CubeIDE.
I have created a new project in Cube and have kept the default System Clock Configuration.
My aim is to have a duty cycle of 50%. I have prescaled by 79 in order to set the Timer Clock frequency at 1MHz.
I have gone through the Datasheet, Reference Manual, and Timer Cookbook several times but for some reason, I can't get it to work. Is there something that I have overlooked in my code?
void intialize_gpioe(void){
    RCC->AHB2ENR |= RCC_AHB2ENR_GPIOEEN;    // GPIOE clock enable
    GPIOE->MODER &= ~GPIO_MODER_MODER14;  // Configure PE14 as Alternative Function.
    GPIOE->MODER |= ~GPIO_MODER_MODER14_1;
    GPIOE->AFR[1] &= ~GPIO_AFRH_AFRH6; // PE14 configured as AF1: TIM1_CH4
    GPIOE->AFR[1] |= 0x01000000;
}

void initalize_tim1(void){
    intialize_gpioe();
    RCC->APB2ENR |= RCC_APB2ENR_TIM1EN; // TIM1 timer clock enable
    TIM1->PSC = 79; // Set Prescaler to 1MHz
    TIM1->ARR = 100;
    TIM1-> CCR4 = 50;
    TIM1->CCMR2 &= ~TIM_CCMR2_CC4S; // CC4 channel is configured as output
    TIM1->CCER &= ~TIM_CCER_CC4P;   // Output Polarity set to Active High
    TIM1->CCMR2 &= ~TIM_CCMR2_OC4M; // Output Compare 4 Mode set as PWM Mode 1.
    TIM1->CCMR2 |= TIM_CCMR2_OC4M_1 | TIM_CCMR2_OC4M_2; // Output Compare 4 Mode set as PWM Mode 1.
    TIM1->CCMR2 |= TIM_CCMR2_OC4PE; // Enable the corresponding preload register
    TIM1->CCER |= TIM_CCER_CC4E; // Capture/Compare 4 Output Enable
    TIM1->EGR |= TIM_EGR_UG;    // Before starting the counter, you have to initialize all the registers
    TIM1->BDTR |= TIM_BDTR_MOE;
    TIM1->CR1 |= TIM_CR1_CEN; // Start Timer
}


texts: Does the counter of an Atmega328 still count inside interrupt handler?

texts:
When you enter the interrupt service routine of an Atmega328 that is triggered from a compare event of the TCNT and the value that is set, will the counter TCNT start counting again or rather, keep counting inside the interrupt handler or is it frozen until the interrupt handler is exited?

I will have an interrupt triggered every X seconds so I'm wondering about the timing of this interrupt. Because if the interrupt stops the TCNT from counting, then I will have an offset every second.


texts:
I new to hspice, i searched on the hspice docs, but still cannot clear about this option. What does this option actually effect on simulation.

  .param dummy=1
  .dc dummy 1 1 1

Please help me on this!
Thanks very much!


texts: Signal Conversion 36V to Logic Level with Zener Diode

texts:
I have 8 cells in series and I want to check them, whether all are connected. I came up with the following schematic:

simulate this circuit – Schematic created using CircuitLab

My question is about R and how viable this solution is.

My reasons for calculating R is the following: I saw that a CMOS gate leaks 1uA. While I don't want to waste energy, I want to be as closely as possible. Not too close, due to noise. So I came up with 470k. Is this too high? Does this work? (Sorry, I don't have 2V Zeners at hand, so I can't check it myself)

Let's say I have a RC element (R=100, C=0.1uF) between the cell and R. Does this help and make those 470k a safer solution?

Do you see any other problems?


texts:
Is the SB19 component a "jumper" (0-Ohm resistor)?  On the board itself, some of these are placed, and some aren't, leading me to believe that's what they are.  There aren't any 0's on them, though.

EDIT: I put 0-Ohm resistor in parentheses because some people thought I was asking if it was a jumper or 0-Ohm resistor, when I meant that it could be referred to by one name or the other.  My bad on the wording.


texts:
I've been struggling with this for a while : am looking for a way to power an ESP32 microcontroller (at 3.3V, or 2.6-3.6V) from a 220V line.

I am trying to do this using only my home'e electrical wires (no plug, so can't use a USB charger).

The question I'm looking an answer for could be reformulante to : What composent is used in  USB chargers to produce a 5 or 3.3V signal from 110 or 220 V line at home ?

Apologies if this is a duplicate, I've tried googling and reasearching on this site but keep coming up with irrelevant subjects.
Ideally, I'd find a ready made (black box type) component I can buy. It is important this composent be very small.


texts:
In ASIC design, we often purchase SRAM macros to use in our designs. A typical SRAM macro includes a Verilog description and a timing/layout characterization (lib file).
My question is this: SRAMs always seem to require a clock to operate. Does this mean SRAMs have input registers in them? Or do they have registers at the output, assuming the inputs are registered outside? The figure below shows a simple block diagram of what I am asking.

Which one is correct?


texts: Cooling requirements of solid state relay

texts:
In the manual of my solid state relay it is mentioned that they recommend using a heat sink with the SSR and if the current exceeds a certain limit (almost 2 magnitudes above what I need) they additionally recommend using active cooling with a fan. Since if possible I would really like to avoid installing a heatsink, I've been doing some reading about SSRs and recommendations about cooling. I've found articles recommending heat sinks when current exceeds 4A, others 10A. I assume this is also related to what current the SSR is rated for. I have an SSR rated for 30A and I am going to have 230V AC with roughly 250mA of current run through it for several hours a day. It will be mounted in a plastic box where it should ideally not exceed 85°C. The box is not sealed and has a rather powerful fan installed but it is not directed at the SSR (yet).
I am now wondering if I even realistically have to worry about cooling, can this small amount of current even generate enough heat to be a problem?


texts: Which software is used to design (and simulate) IC?

texts: Currently I'm using Proteus to design and simulate all of my schematics. Is there any (free) software for designing and simulating ICs? I searched the Internet and found Cadence and Glade Thanks!


texts: Limitations of MOSFET-pair Current Mirrors

texts:
simulate this circuit – Schematic created using CircuitLab

For simple MOSFET-pair current mirrors, such as the NMOS version above, are there any known disadvantages that one has to consider? The above example, for instance, does not perfectly mirror the current (I really don't know about this, as the LTSpice sim works perfectly).

I'm excluding the discussion about parameter mismatch between the MOSFET pairs (V_TO, λ, K, etc)and the condition I_REF ≤ V1/R_LOAD, but more of noise or bias or anything like that.

What I mean is does this just sorta average out as current mirroring? The same way that a Common Drain sorta averages out as having voltage gain of a little less than unity?

EDIT:

What about frequency response? Can MOSFET-pair Current Mirrors reach GHz range?
Or, Is it useless to ask? This being the simplest MOSFET-based Current Mirror?


texts: Is the wikipedia article on 3b4b encoding in 8b10b encoding correct?

texts:
On the wikipedia page for 8b10b encoding (as of writing), the 3b4b table shows that if RD=-1, the outputs can have more 0's than 1's, and if RD=+1, it can have more 1's than 0's.  This does not make sense to because if you already have too many 1's or 0's, you would not want to go more positive, or negative.  Is this a mistake on the wikipedia page, or is my understanding of 8b10b wrong?

https://en.wikipedia.org/wiki/8b/10b_encoding


texts: The calculation of Conventional non-tripping current and Conventional tripping current of MCB

texts: IEC 60898-1 defines the Conventional non-tripping current and Conventional tripping current of a circuit breaker is 1.13In and 1.45In. But why these two numbers? Well, the normal wave of power network may have been taken into consideration. How to calculate them?


texts: Running 60Hz 220VAC motor on 50Hz 220 VAC using VFD

texts: I have imported a hydraulic power unit from Canada. The problem is that the motor is designed for 60Hz frequency but we have 50Hz. Now when we plug in the motor it makes alot of noise and vibration. It gets heated up as well. Now I was thinking to use single phase VFD that will take input of 50Hz and will give output to 60Hz. I just want to confirm before buying VFD that can it work ? and if there would be any effect torque and efficiency. Please share experience if someone has any