texts: can I use Two Same Power supply sharing input in single circuit?

texts:
I currently have a circuit which consists of two different boards. In the main board, there is a \$230\,\mathrm{V}\$ ac supply, a \$230\,\mathrm{V}\$ to \$12\,\mathrm{V}\$ dc power supply, a 7805 linear voltage regulator and other components as transistors biased on their collectors by the \$12\,\mathrm{V}\$ dc generated in the main board itself. On the another board there is a controller, powered from the \$5\,\mathrm{V}\$ supply generated by the main one: this controller drives the transistor located on the main board.
Now I want to use a separated \$230\,\mathrm{V}\$ to \$12\,\mathrm{V}\$ dc power supply for the controller board, so I'll be able to power my controller board from a \$3.3\,\mathrm{V}\$ power supply produced by using another regulator. So there will be two \$230\,\mathrm{V}\$ to \$12\,\mathrm{V}\$ dc regulators, one located on the main board and another on the controller board.
Now my question is:

  Is it OK for the controller to drive transistors whose \$12\,\mathrm{V}\$ collector bias is generated from a different, separated regulator, however sharing the same \$230\,\mathrm{V}\$ dc grid voltage,?  I am also using an ADC which is measuring the output of a temperature sensor powered by the main board \$5\,\mathrm{V}\$ supply and sending its output to the controller board: could this create any problem? should I short the gnd terminals of both boards? Do I need to do anything else? Is this operation safe?


texts: How will the diode act after its junction is penetrated?

texts:
Above is a circuit diagram with 2 sources V1 and V2, a switch SW, a diode D1 and a resistor R1. The points X,Y,A,B,C,D,E,F are terminals of the components indicated with red dots.

If the switch is OPEN as in the figure, the diode D1 is reverse biased and no current will flow.

Lets say the switch is closed(SW CLOSED) and opened in a very short amount of time which is enough to penetrate the p-n junction so that V1-V2 = 10V is applied in that duration to the ends of diode and the diode is forward biased for that short time.

And then lets assume suddenly the switch is opened(SW OPEN) again and kept always opened from then on. Here is my question:

Will the p-n junction remain penetrated and will a current flow through the points C,B,A,D,E,F in order? Or will it block the current since it looks like it is conencted as reverse biased?


texts: Proteus ARES PCB - How do I wire a link pad to some component pad?

texts:
I'm designing a single side pcb, due to trail's density, I decided to use link wires in order to avoid overlap, but when I started routing, the software didn't allow me to connect any wire to link's pad. I tried to assign some netclass but couldn't find a way to that. Sometimes, only by luck, I successfully make the connection, but I'm clueless about what made it possible. I attached a picture that illustrates both situations.
I'm using Proteus 8.6 SP2.


texts: Protect battery from overvoltage - DC brushless motor overspeeding condition

texts:
I'm trying to figure how to protect batteries from overvoltage on my electric skate. Specific condition is : motor would run above max RPM based on system voltage.

Motor is 85Kv, battery voltage is 33.6V. This gives max RPM of 2856.

Goal is to be able to spin the motor up to 4250RPM, which would bring "motor" voltage up to 50V.

Can I use TVS diodes (starts working at 30V, fully operates past 33.5V) to redirect / suppress exceeding voltage toward a loop of resistors ?

I have a hard time figuring their use. Was thinking of making a combo TVS + Schottky diodes to force one-way direction + a big resistor in between to dissipate exceedding power.

Thanks


texts:
I am suing superposition to solve for IR3.

Professor said there is no current flow through 1 kilo ohm resistor. He said it is because it is in parallel with the voltage source. I am confused. If a resistor is in parallel with the voltage source can I ignore the resistor?

Why is there no current through in this case exactly?


texts: wiring two inverters/charger at the same battery bank

texts:
I have 30 solar panels charging 12 batteries (48V system, 4 12V batteries in series ×3 ). 230 W / V=36.4V \$I_{\text{SC}}=8.56\,\text{A}\$

My problem is that I have not found a solar charger for the configuration
3 panels in series with 10 branches.
The open circuit voltage is 109.2 V
and short circuit current is 85.6A.

My questions:

Can I use two inverter/chargers for the same battery bank?
Is it possible to use two charge controllers to charge the same battery bank?


texts: Set a reference voltage: using a zener diode vs using a buffer

texts:
Given the following hysteresis comparator circuit:

simulate this circuit – Schematic created using CircuitLab

R1, R2 and OA1 are used to set a reference voltage for the comparator with hysteresis OA2. The circuit works fine but I was wondering whether there could be a better (or more clever) way to set Voffset without using an "expensive" (or precious, if you wish) opamp. Would using a 6V Zener diode in parallel with R2 be a better choice for instance? What problems would it possibly cause? If you have other options please do point out advantages and disadvantages compared to the proposed circuit.

Sorry, I've just realized a few more specs could help:

Voffest must be around 6V with a +-0.5V tolerance.
The power supply is a battery, as far as my tests went, a +-1V on the supply rail should cover most scenarios.
I made some tests with a few spare LM741CN I had laying around. Speed is not a requisite. The V+ terminal is wired to 12V and the V- is wired directly to ground.
The hysterisis window should be of about 5V +-1V which is about what I got with my brief tests.


texts: Single pulse generator using discrete components

texts:
I've a board like this:

simulate this circuit – Schematic created using CircuitLab
What I want to do is to drive LEDs with OUTPUT pin. This LEDs are used like flash source, so I turn them ON for a very small amount and then off for a relative long time.
I have a button to manually drive the flash, so I must limit ON time by external hardware to avoid LED damage.
What I've done this schematic:

What this circuit should do is:
Circuit is 24V powered -> Button is randomly pressed -> Flash ON for RC time (about 2ms) -> Time finished Flash goes OFF -> Button is released -> C de-charge -> Button is randomly pressed..etc..
I've tested on breadboard and circuit actually works. But I've found some problems:

When button is released, OUTPUT take some time to go HIGH again. Actually not a real problem, but if there's a way to solve I'll able to control better ON time length;
Very rarely circuit freezes with OUTPUT to LOW, happened 1 or 2 times after pressing Button and some more times when circuit is connected to power for the first time;
ON time sometimes doubles or triples, sometimes OUTPUT stay LOW for 4ms or 6ms instead of 2ms;

I attach an oscilloscope image about problem 1) .

EDIT: I've corrected Schematics image.


texts:
I am new here to StackExchange and new to electronics in general. As my second electronics project (the first being a blinker circuit for a bandolier of LEDs) I am building a regulated linear power supply.

The specifications for my power supply are mostly dictated by the components I have available and are within my budget and skill level. Ideally I would like a variable dual output with the ability to supply negative voltage for use with opamps and audio amplification, which is where I am in need of assistance.

So the transformer I'm using is rated for 12VAC at 2A. It is not a center tap transformer.

So, my question :

What would be the easiest way to get a negative rail? I've seen people connecting two positive outputs together in series in a common ground configuration to obtain negative voltage, so would this work given my schematic?
I also have another transformer that can supply 12VAC at 500mA, would it be worthwhile use that alongside the other transformer to provide a negative rail? Would I need a negative voltage regulator for it? I'm under the assumption that having dual half wave rectifiers isn't generally feasible for non center tapped transformer.

Below is my draft schematic (untested) for the supply I would like to build given that I can just hook up the two outputs in series and get a negative rail. I'm just unsure if the setup I have is adequate for it.

I have no idea if the dual output setup I have here will work, I don't see why it wouldn't though. I have no idea what I am doing really so I am probably wrong.

Any general advice would be great as well, thank you.


texts: What does CPM unit mean in relay specification?

texts:
I have a power relay, where in specification it states that "Max operating speed (at rated load)" is "6 cpm". What does that mean?

C.... per minute? Does that mean, that relay can change state every 10seconds (60s/6cpm)?

Other questions is, how to explain "Expected life (min. ope.)" under "Contact specifications", where cpm unit is used again?

Here is the relay datasheet: farnell.com/datasheets/55170.pdf


texts: How to connect Bluetooth module Left and Right audio out to a single 3.5mm TRS

texts:
I'm building my own Bluetooth audio receiver using a Bluetooth module 2.1 with A2DP, so I can connect the receiver (with internal power) to any set of speakers that has a 3.5mm jack, then play music via any Bluetooth device like iPhone or PC.

I got the Bluetooth module wired up and can now be paired with any A2DP enabled device, the issues is, the Bluetooth module has output connectors for 2 audio channels: Left Positive, Left Negative, Right Positive, and Right Negative, my question is how do I connect the 2 channels to a female 3.5mm jack? do I need something like a summing box (which I don't really understand yet), or is there a simple way to solve this? I hope to keep the entire receiver small.

P.s. I initially thought the two negatives are two ground so I solder them together to the sleeve of the TRS, but then the module won't turn on. Further testing found that whenever the 2 negative touch the Bluetooth would shot-out and shut-off. If I just connect one of the negative then I have sound coming out of both speakers, but then I think there would be no difference between left and right sounds.

Thank you.


texts: What do Capacitors do in a System with a Speaker?

texts: I made a circuit based on a diagram from my physics teacher. The circuit has a 555 chip connected to seven wires that make up a circuit. The circuit includes a photocell resistor that acts as a variable resistor. My question is why are capacitors needed to make the speaker work? I'm sorry if this question seems to be a duplicate of What is the job of the capacitor in a 555 circuit?, but the answers on that question don't explain how capacitors help the speaker work.


texts:
I want to build a frequency multiplier with high multiplication factor. I read some application notes of Hewlett Packard on Step Recovery Diodes. I think a SRD can do what I want. However, I have never used one before. Since they are difficult to obtain, I searched for a replacement and came up with standard PIN diodes.

I searched for PIN diodes with low capacitance and short carrier lifetime which should in my opinion give a large number of harmonics. My preferred type of PIN diode is HSMP-3822, but I don't have one here, so I used HSMP-3832 for some first experiments.

Indeed, I got harmonics up to 100 MHz with a 5 MHz drive signal, which is pretty good in my opinion. However, I don't have an idea what the exact design procedure is for a SRD comb generator.

How do I find the correct drive level and what other components do I exactly need for the SRD?


texts: Why are most of the RESET signals in embedded systems active low?

texts:
I am hardware design engineer. I had seen lot of board designs since 2015. In my career I have seen that most of the RESET signals are of active low signals. Is there any logical reason behind that?
Following are the major reset signals which will be present in the most of embedded systems

Power on Reset
Cold Reset
Warm Reset
PCIe Reset
DDR Reset
USB PHY reset
SPI protocol Chip select

Any insight would be greatly appreciated.


texts: Is there any difference between voltage drop and voltage across a component?

texts:
Voltage drop across a component describes the reduction of energy when current moves through passive elements, is this the same as voltage across?

What about for capacitors, technically current does not actually travel through the dielectric, can this term still be used for capacitors?


texts: How do I solder a surface mount (smd) voltage regulator?

texts:
I have a PCB in front of me with a surface mount 5V voltage regualator. I'm wondering how I got about soldering this with just solder (I don't have paste).

I have heat paste, but I'm wondering if pre-tinning the pad and heating it up afterwards from the side with the regulator will be equally effective if this is possible.


texts: If a meanwell ldh-45 led driver provides a range of voltage outputs at a constant current, how is my desired voltage selected?

texts:
http://www.meanwell.com/search/LDH-45/LDH-45-spec.pdf

350mA = current.

Lets say my LED forward biases at 42v.

Is it a 120 ohm resistor that I need?  42V = 0.35A*120 Ohms

I am a bit confused.  Typically when working with LEDs people call the resistor current limiting.


texts: Can an NMOS act as an NPN BJT if Vds is high enough?

texts:
The physical layout of a MOSFET is very similar to BJT transistor, if we ignore the gate. Normally a FET requires a gate voltage to turn on and allow current flow from Source to Drain or vice vera.

My question is: Can a very high \$ V_{ds} \$ force charge carries drift through the channel and reach the other side?


texts: 362J04 230AP SMD SOT23-6 PWM IC on DELL LED Monitor Power Supply

texts:
Is there any way to find the datasheet for 362J04 230AP SMD SOT23-6 PWM IC of a DELL LED Monitor Power Supply? At least a close match is good.

Figure 1: PCB top view

Figure 2: 362J04 SMD in DELL E2219 power supply
I could not find any reference in Google. This PWM SMD drives 4NB65 MOSFET as shown in PCB. It is the PWM.
Furthermore, similar series SMD are available for sale in this link. However I could not find that datasheet also.


texts: Confusion about basic reference distance based path loss formula in wireless communication

texts:
In the following, I am confused about results I am getting by the reference distance based pathloss formula.
My transmitter power is 1 mW (i.e. -30 dB). But the received power is much much higher than that (starts from 200 dB). I have used the textbook formula (PL = Pathloss, do, Po = reference distance and reference power, d = actual power, alpha = pathloss component)

PL = 10 xalpha x 10 x log10(d/do) -PL0

. However, I am not sure what is wrong with it. The Matlab code and the images are below.
Pt = 1e-3; %(1mW)
do = 1; % (meter) Reference distance
alpha = 2; % Pathloss exponent
PL0 = 30; % (dB) Reference pathloss at distance do

PL(idx) = 10*alpha*log10(d/do) - PL0;;


texts: How much space does a 220V AC input power supply save compared to a 120V one?

texts:
For a given output voltage & current, how much space is saved by using 220V  instead of 120V input?

Specifically, I want to know is it expected for 220V only welders to be much smaller than equivalent ones that have to work with both 120V & 220V. Here's a comparison. It's not exactly fair because the 220V machine has less cooling and only allows 25% duty cycle. Another comparison I could've done is compare a 220V only computer power supply vs a 120V one, but it appears there are no 220V only PSUs.

220V: Bossweld 200 Amp TS200 (25% duty cycle @ 200A)

145mm x 280mm x 410mm = 16.6L
7kg

https://www.bunnings.com.au/bossweld-200-amp-ts200-tig-stick-inverter-welder_p6380047

120V: Weldpro ACDC 200GD AC/DC 200 Amp,  40% duty cycle @ 200A

447mm x 201mm x 406mm = 36.5L
< 27kg

https://www.amazon.com/Weldpro-Digital-Voltage-welding-machine/dp/B07LCSXYN5

So the 120V machine is 2.2x bigger.

Assuming a welding power supply uses the same design as a computer power supply like described here and here.

Then it's obvious a 220V supply would only use 0.55 the current in all stages before and up to the primary coil of the transformer. Everything after that would be the same for both 120V and 220V.

So is it fair to conclude that the high voltage, non isolated side will be 1.8x bigger in a 120V design? What fraction is taken up by the other isolated, low voltage side?

I'm also assuming having to support variable input voltage shouldn't cost anything extra, because you don't need any extra hardware, just a different duty cycle.


texts: What is "rabbit ear" in a video-capture context?

texts: I was reading the TVP5158 datasheet, and ran into a register bit that would enable "rabbit ear". What is that?


texts: Is a sinewave that is present entirely within the positive domain DC? How to calculate Vrms for a DC offset sinewave?

texts:
I've been given some conflicting information with regards to the current type of a sinewave that has no negative component e.g. 20-30V pk-pk is either DC or AC.
I have been taught by my lecturers that this is in fact DC. However, talking amongst older EE graduates they seem to be very adamant that this is an AC waveform despite the fact the polarity never changes.
How would one go about calculating the Vrms for such a sinewave? I have found many different equations giving different values.


texts: Can someone explain the use of the transistor in this circuit?

texts:
I came across a schematic which implemented a 1 Wire interface. However, this 1-Wire interface circuit also includes a transistor connected as shown in the picture. Can somebody expain why this has been done? I read on a Maxim AN about using transistors in order to be able to use a stronger pullup (R2) but I don't see how that works.
Thank you for your help


texts:
I am a beginner when it comes to electronics so I would appreciate your help with a simple project I am working on and have been struggling with for several days.

The idea is that I have a PIR Sensor outputting to GPIO 24 on my Pi. Via a python script, I would like to switch on a 12-volt LED strip with its own external power supply. I am able to see when motion is detected via the script, so that is working fine. The issue however is that I am not able to properly use my mosfets to act as a switch. In order to take it step by step, for now I am trying to output signal to my mosfet Gate via GPIO 24, and manually alter the PWM via terminal (instead of using the PIR output).

My scheme is similar to this: https://screen.sh/cAaSbZiM - however not using the battery, and using the GPIO 24 output instead of PIR.

I have tried this with a IRLB8721 mosfet, but realized it needs a higher voltage than what the GPIO can provide. The most suitable one I could find then was the IRF3205, seeing that it is used more frequently with Raspberry PI/Arduino applications, but unfortunately this is also not working. It seems like my GPIO voltage is still too low.

Alternatively I have a couple of 2N3904 transistors available but I am not entirely sure how I can use these without frying them.

I have noticed that when using the IRLB8721, my LEDs are always on, and I am not able to switch them off. I did make sure not to mix up the Drain and Source, yet still not working.

Could you please guide me in the right direction? I am not able to get any other components for another week, so I am stuck with a diode, couple of 1kOhm resistors, and these 3 types of transistors/mosfets/ Is there anything I can do to fix this?

I have looked this up extensively and tried it on my breadboards but with no success. Only lead I have is pointing to a fairchild mosfet which I am not able to get to for weeks.

Thank you.


texts: Question about equation for LT3750 capacitor charger IC

texts:
I have a question about the equation for minimum primary inductance on page 8 of the data sheet for the LT3750 high voltage capacitor charging IC.

The equation in question:

$$L_{\text{pri}} \geq \frac{V_{\text{out}} \times 1\text{ }\mu \text{s}}{N \times I_{\text{pk}}}$$

My confusion comes from the (× 1us) part. Would the minimum inductance for, say a circuit with an output of 600V, a peak current of 3A and using a transformer with a ratio of 1:10, be

$$\frac{600 \times .000001}{10 \times 3} = 0.00002\text{ uH}$$

or

$$\frac{600 \times 1}{10 \times 3} = 20\text{ uH}$$

or something else?


texts:
I am creating a PCB which has multiple ground pads which are connected together off-board. Pcbnew however doesn't know this, so it continues to draw white connecting lines between the ground pads, and of course ERC fails.

How do I tell KiCAD that certain pads are connected together "off-board", and thus does not need traces connecting them?


texts: Charging a protected Li-Ion without a charger (still confused about charger vs protection)

texts:
I opened an USB rechargeable speakers which contain the PCB as follows:

It uses a 1000mAh Li-Ion battery with a protection circuit (not in the figure).
I couldn't find a battery charger IC in the PCB.
I opened the battery external involucrum and noticed a 8205A and DW01 ICs in the protection circuit.
These ICs also come along with TP4056 charges as I could notice.

So, I'm still confused about the differences and necessities of both a charger and a protection circuit:

Does a charger require a protection circuit?
Do all protection circuits require a charger? If so, why having protection circuits attached to the batteries after all?
What is missing in a protection circuit to also allow charging? (since both the 8205A and DW01 are present in the protection circuit and charger)
How come my speakers don't have a charger IC but still work?

Thanks


texts:
I have thoroughly read the TWI part of ATmega data sheets, but I am still confused about a few things.

If I write TWCR = (1 << TWINT);, will that write a zero to TWIE (and thereby disable TWI interrupts)? If I write TWCR = (1 << TWINT) | (1 << TWIE);, will that write a one to TWIE (and thereby reenable TWI interrupts)?
In the most recent data sheet for the ATmega1284p for example, the SCL frequency is calculated as follows:

\$ SCL = \frac{F\_CPU}{16\ +\ (2\ *\ TWBR\ *\ PreScaler)} \$

However, on this document: http://www.atmel.com/Images/Atmel-2564-Using-the-TWI-Module-as-I2C-Master_ApplicationNote_AVR315.pdf
the SCL frequency is calculated as follows:

\$ SCL = \frac{F\_CPU}{16\ +\ (2\ *\ TWBR)\ -\ (4^{TWBR})} \$

and I have even seen other versions on other websites. Has the formula changed? Which is the correct one?
Is it safe to assume that the TWI hardware is the same for all microcontrollers in the ATmega series?


texts: "Live neutral reverse" and "hot/neu reverse" difference?

texts:
I've got a "Meterk GFCI Electric Socket Tester" that can detect "live neutral reverse" and "hot/neu reverse" cases.

Meterk E2752

What could be the difference between these cases? Isn't "live" a synonym of "hot"?

Thanks.


texts:
Newbie: I have a signal generator set (I hope!) to output a 60htz, 12v sine wave. When I put a DMM set for AC across the output I measure < 5v?? I expected either 12v peak to peak, or 8.5 RMS. What am I missing?

FeelTech FY6800
CH1=SINE ON
FREQ: 0.050 KHz
AMPL: 12.0000V
OFFS: 0.00
DUTY: 50.00% (not changeable)
PHASE: 0.0°

DMM AC 0.421 V RMS


texts: How to use extra channels in drone controller for other purpose

texts: I'm doing a hexacopter for my academic project. I brought flysky fs-ct6b drone controller. It has 6 channels. 4 channels is enough for controlling the drone. but I don't know how to use another extra 2 channels for other purposes. i.e for on/off a pump for the sprayer within the drone. can u help me, please?


texts: SPICE modeling gas discharge tube using state machine and behavioral resistor

texts:
A gas discharge tube (GDT) is a state machine which transitions from a high impedance ("normal") state to a low impedance ("glow") state when the potential across its terminals exceeds the spark-over voltage. Older SPICE models of GDTs tend to use switching circuitry.  In 2008 Julio G. Zola published a paper describing a GDT model using only basic electronic components and no explicit switches. This model works well. However in 2018, Analog Devices introduced state machine support for LTspice; this together with behavioral resistors seems like a good fit for modeling GDTs ... with something like this:
* -----------------------------------------------------------------------------
*| GDT model based behavioral resistance and state machine
*|     <pin1>-----o-----o----
*|                |     |
*|               _|_    \      { Vhold / Ileakage    if state = Normal
*|             Cp---    / Rp = {
*|                |     \      { Vhold / current(Rp) if state = Glow
*|                |     |
*|     <pin2>-----o-----o----
*|
* -----------------------------------------------------------------------------
.subckt GDTx pin1 pin2
* -------------------------------------
*| parameters
* -------------------------------------
  .param Vhold        = 15
  .param Capacitance  = 2p
  .param Vspark       = 90
  .param RPval        = 150Meg
* -------------------------------------
*| state machine
*|     _____    if |V(pin1,pin2)| > Itrip   _____
*|    /     \ ---------------------------> /     \
*|   / state \                            / state \
*|   \ Normal/  if |V(pin1,pin2)| < Ihold \ Glow  /
*|    \_____/ <--------------------------- \_____/
* -------------------------------------
  .machine
    .state Normal 0
    .state Glow   1
    .rule  Normal Glow   abs(V(pin1,pin2))>{Vspark}
    .rule  Glow   Normal abs(V(pin1,pin2))<{Vhold}
    .output (machineOUT) state
  .endmachine
  Rx machineOut pin2 1
* -------------------------------------
*| circuitry
* -------------------------------------
  R2 pin1 pin1b 1p
  V2 pin1b pin1c 0 Rser=0
  Bsrc pin1c pin2 R = (1-u(abs(V(machineOut,pin2))))*{RPval} + u(abs(V(machineOut,pin2)))*{Vhold}/abs(I({R2}))
  CP pin1 pin2 {Capacitance}
.ends GDT_behavioral

However, I would rather not have the 1pΩ resistor R2; but when I try to use the current I(V2) instead of I(R2),
  Bsrc pin1c pin2 R = (1-u(abs(V(machineOut,pin2))))*{RPval} + u(abs(V(machineOut,pin2)))*{Vhold}/abs(I({V2}))

I get "Fatal Error: Analysis:  Time step too small; time = 0.00147989, timestep = 1.2613e-018: trouble with node "v:u1:2#branch""
What should I do to be able to eliminate the resistor R2 but still be able to implement the Bsrc based on current through that node?
LTspice XVII (17.0.19.0 November 25 2020 12:46:47 US Pacific)


texts: TI CC2545 supports how many Channels for 1Mbps and 2Mbps Data Rate

texts:
According to TI CC2545 User Guide Page 236, Section:23.5 Frequency and Channel Programming:

"

For normal transmit and receive tasks, the carrier frequency is set by using the register PRF_CHAN.FREQ.
The carrier frequency is 2379 + n MHz, where n is the value of this register, where n can be from 0 to 116.
This gives a frequency range from 2379 MHz to 2495 MHz. Note that this frequency range extends
beyond the ISM band. If PRF_CHAN.FREQ is set to 127, and for the Rx and Tx test commands, the
frequency must instead be programmed directly in hardware registers.
In this case, the synthesizer frequency is set by programming the 7 bit frequency word located in
FREQCTRL.FREQ[6:0]. The synthesizer frequency is given by 2379+ nMHz, where n is the value of
FREQCTRL.FREQ[6:0], and is programmable in 1-MHz steps. The device supports synthesizer
frequencies in the range from 2379 MHz to 2495 MHz. The usable settings for freq[6:0] is consequently 0
to 116.
In Rx, the system operates on a low intermediate frequency (IF) of 1 MHz for data rates up to 1 Mbps, and
on a zero IF for 2 Mbps. In Tx, the system supports operating on low IF or zero IF. The IF to be used for
Tx can be programmed in the register MDMTEST1.TX_TONE. The receiver may operate on a positive of
negative IF when the data rate is 1 Mbps and lower; this is controlled with MDMTEST1.RX_IF.
When the symbol rate is 1 Mbps or lower and the LLE programs the frequency, it uses a ±1 MHz IF on Tx.
For both Rx and Tx, a negative IF is used when PRF_CHAN.FREQ < 62 and a positive IF is used when
PRF_CHAN.FREQ ≥ 62
When the symbol rate is 2 Mbps and the LLE programs the frequency, it uses an IF on Tx as specified in
PRF_RADIO_CONF.TXIF. This IF may be zero, or ±1 MHz, ±2 MHz, or ±3 MHz. The recommended
setting is ±1 MHz. A negative IF is used when PRF_CHAN.FREQ < 62 and a positive IF is used when
PRF_CHAN.FREQ ≥ 62.
For all data rates, the setting of MDMCTRL1.PHASE_INVERT is taken into account by the LLE when finding
the setting for MDMTEST1.TX_TONE. The FREQCTRL register will be programmed corresponding to the
programmed IF in order to operate on the channel specified by PRF_CHAN.FREQ.

."

My questions is:

[1] How many number of channels are possible within 2400 - 2483.5 ISM band if I use 1Mbps and/or 2 Mbps Data rates.

[2] Could I change Channel Spacing for both 1 Mbps or 2 Mbps. Do CC2545 support channel spacing settings.?

I have consulted Datasheet and User guide but i am still confused some brief description will be appreciated. Thank you


texts:
Why do the electron loose energy when it moves from base to collector region?
In a npn transistor first emitter base junction is forward biased so electrons move to the base region . The electrons are minority carriers for base .now when base collector region is revered biased ,as the electrons injected in the base move towards the CB junction it gets easily transmitted to the collector region since the reverse bias produces a strong field which helps the electrons to move.so my question is the electron after reaching the CB junction feels a field i.e a force which further helps it to move to the collector region.so the electrons should be gaining energy and also reverse bias depletion region will not act as as a resistor.


texts:
I want to select a common mode choke. This will be placed at the input of a buck regulator. Now, assuming conducted noise or common mode noise, will be at a certain frequency and I will need common mode chokes that have high impedance at that frequency. For eg / I have a buck running at 100kHz. Then I will need a common mode choke tof high impedance at 100kHz and at harmonics of that fundamental frequency. The fundamental is 100kHz. Now, when terming harmonics, what is the max multiple that should be a worry ? Is it the 3rd harmonic ,so 300kHz ?

Also, when it is said we need high impedance at fundamental frequency and its harmonics, what exactly can be termed as high impedance ? WHat is the value and what is the basis for that value ?


texts: ADC power supplies monitoring - How to reject short overvoltage pulses

texts:
I have an MCU application where the MCU switches on/off and monitors the various power supplies of the board (3.3V, 1.8V, 1.0V etc.). When an under- or over-voltage is detected, an alarm to the system should be raised.

Until now the implementation was a bit simplistic: I only took one sample every 5ms and if it was above/below the relevant threshold, for overvoltage/undervoltage respectively, then the alarm was raised.

That led to the problem that on one board, where the dc/dc converter design was not optimal and short over-voltage pulses were present, the alarms were thrown. Such a behavior is of course not desired.

Now I am trying to optimize the c code of the MCU to cope with the problem. I know that ideally this should be solved at its origin (correct the HW design or implement an analog LP filter) but let's assume that this is not possible for the time being.

My first idea was to require more than one consecutive samples to be outside the limits before an alarm is triggered. But somehow I came to this thought: what if I happen to sample exactly when the over-voltage samples occur? I am not sure if they are periodic at all, but it may also be the case. I cannot exclude it. In such a case such an implementation would also fail; it would trigger a false alarm. What do you think? Does this thought make sense at all?

And then my next idea is to implement a digital low pass filter. Probably an IIR recursive filter. But here the questions are even more. Would this really solve my concerns? I mean, if the samples are taken exactly when the periodic pulses come, then the filter solution fails too. Do you have something else to propose? Do you think the digital LP filter is a good idea? If yes, I suppose I should somehow set the 3dB frequency of the filter close to DC. Is that anyhow possible?


texts: Designing a Transformerless power supply

texts:
I am working on a transformerless PSU for maiking a 3nos.x3 watt led, each having forward voltage around 3.6v and current around 650-700ma.

I have worked on this kind of circuit:

I guess a 1uf 400vac cap at C1 will offer current around 70-80ma, but here I need a current output at around 8-9 time above this. Means around 600-700ma. I am assuming a Vout at 12v dc (where input is 220vac), where 3 of 3 watt led's are connected in series.

Can anyone explain how can I get such an output from this circuit, means what value of C1 and R1 should be used here. Is there any theoretical formula to calculate the output of such a capacitive circuit, or I should say how do I know what value of C1 can give me an output (Iout) of a specified value. Though I have used This, for calculating the same but I can't derive the relation with the led circuit. Any help is appreciated.


texts: What is the difference between 1-phase and 3-phase motors?

texts:
I've read the wiki page on AC motors, but it's still unclear to me as to how they work. I'm looking at motors for a project and need them to be able to have their speed controlled by a light dimmer (for various speed settings). While doing this, a lot of the motors were marked as 1-phase or 3-phase.

What is the difference? Does it have anything to do with the possibility of speed variance?


texts: Can a memory chip have a certain starting address

texts:
In my book there is a question stated:

  Can a memory chip of capacity 512 KB have the starting address
  2B0000h?

To me this seems like an incomplete question with a wrong answer in the book. The answer states:

  No, because the first 16 bits of the starting address are zero, which
  means the capacity of a chip that can have this starting address is 64
  kB.

Is it possible to deduce such an answer based on the given information and why does he say that the capacity of a chip that can have this starting address is 64kB, if the one writing the answer wrote 64kb I would understand that he got it from the 16 zero bits, but even then we can't know if there are more chips and a decoder before it all enabling different chips or if there are more of these chips connected in parallel to form 16 bit words etc.? Also we don't even know how many bits we need for offset, as we don't know if the word on for this processor is 8, 16, 32 bit etc. or if it can address only words or bytes?


texts:
I have a pressure transducer outputting 0-5V which is sampled by an ADC with a 0.5V minimum input voltage.  I need to offset the sensor output voltage by a fixed voltage of 0.5V.  I've looked at an op amp circuit for doing this.  But I struggle with finding a practical way of generating a reference offset voltage that is temperature stable (I'm not sure about using a resistor divider down from Vdd).

Any ideas would be appreciated.

Incidentally, the upper limit of the ADC is irrelevant, as we will never get an output signal in that range.  Therefore, I want unity gain.


texts:
If I keep my charger plugged in while my phone is not connected, it does not heat up.

So, it is safe to keep the charger plugged while it is not connected to the phone?
Will it draw current?


texts: Can I make photodiode's voltage output bipolar?

texts:
I am trying to detect light with photodiode. Currently, I am planning to build a circuit like one of the followings:

Two circuits' output will swing between 0 to Vcc volts.

What I want is, I want to make an output swing -A to A volts.
For better understanding, please note the following figure:

In the figures, original signal is a brightness of light signal and NRZ coding will be the output of photodetecting circuit, and the input of ADC.

So, the problem is, Can I build a photodetecting circuit which converts unipolar waveform of light into bipolar NRZ waveform of voltage?

NOTE: The ADC is originally used for RF signals and antennas which outputs NRZ signal. Therefore, you don't need to worry about How ADC accepts negative voltage input?


texts: Is this the behavior of a broken mosfet?

texts:
I designed this circuit to switch on/off 8 solenoid valves for a programmable dancing fountain that I am building. The GPIO is coming from a Raspberry Pi. VCC is coming from a 12V deep cycle car battery. I built and tested this circuit and it is behaving properly on 6 out of 8 mosfets.

This is the behavior of the 2 non-functioning mosfets:

Solenoid switches on as soon as the battery is attached (bad)
Solenoid valve heats up
~7.5V observed on the mosfet gate (should be 0 unless triggered)

Could the 7.5V gate voltage be due to a broken mosfet?

I noticed this behavior after hooking up 2 solenoid valves at once (to different mosfets).
I have tested all 6 other mosfets individually and they all work.

If I have broken the mosfets, what steps can I take to protect them in the future?


texts: Difference between IRMS and Peak Current on Capacitor Rating

texts:
Background: I was looking at a spec sheet for a round metallized polypropylene film capacitor that gave two different current values for the "IRMS at 100 kHz -70 deg C" and the "Peak Current"

I'm planning on using a pulsed power system that produces 300 A pulses that last for 27 uS and occur at a frequency of 10 Hz. The IRMS at 100 kHz given was only 13.5 A, while the peak current was 432 A.

Question: What's the difference between the two? Based on the specs given, will the capacitor likely be able to handle the 300 A pulse I described?


texts: Strange LED flicker when powered via buck converter

texts:
I have a 12V supply with a buck converter stepping down 12V -> 3.3V to power an esp8266 microprocessor.

The esp is controlling a 12V LED strip switched via 2n2222 transistors. When all LEDs are switched off I can see this constant flicker going on.

How can the transistors switch when the base is grounded, or what else could explain this flicker?

I don't have an oscilloscope unfortunately.

edit: When I remove buck converter and power esp separately the flicker is resolved.


texts:
I just soldered together the PICAXE 8 Pin Proto Kit, and I have a feeling there is one part missing.

Here are the images for the kit:

The part that I think is missing is the white component in the first picture and the blue component in the second image.

However, the list of components in the document that came with the kit says:

Contents:

    PCB     Protoboard PCB
    R1      10k resistor
    R2      22k resistor
    C1      100nf polyester capacitor
    H1      3pin header and jumper link
    CT1     stereo download socket
    BC      Battery Clip
    IC1     8 pin IC socket

The spot on the PCB corresponding to the missing component on the images is labeled "C1" to make things even more confusing.

(there is another place for "optional capacitor holes" where I soldered in the yellow 100nf capacitor, so I don't think the area labeled "C1" is for the capacitor)

Questions:

I would love to know what that part does (the white component in
the first image and blue in the second).
Is it necessary or not?
Is it supposed to be there as per the list of components?


texts:
Following types/variants/package of P1022 freescale processors are available in market:

1)P1022NXE2LFB

2)P1022NXN2LFB

3)P1022NXE2HFB

4)P1022NXN2EFB

5)P1022NXN2HFB

6)P1022NSE2EFB

7)P1022NSN2EFB

8)P1022NSE2HFB

9)P1022NSN2HFB

10)P1022NSE2LFB

11)P1022NSN2LFB

12)P1022NXE2EFB

However, datasheet of most of the packages is same, my question is how above packages differ from each other and how name signifies that difference.


texts:
I was reading some text on microwave devices when i came across these devices.The explanation in the book was very convoluted and difficult to understand. Could some one please explain to me

Basic operation of TRAPATT & IMPATT
Difference between these devices

If you find it too tedious please point me to some reliable references on the internet.


texts:
Would it make sense to connect the GND pins of an 8-pin PCIe power connector to a common point ground (which is at earth potential) and then plug that dummy connector into my new GFX card, before installing the GFX card onto the motherboard?

The setup would look like this.

This way the motherboard and GFX card are at the same potential, before making contact, and while installing. After installing, when the GFX card is in place, i will remove the dummy connector and attach the real power connector from the PSU.

Good plan? Bad plan?

Edit: 1 answer suggests touching the bracket/faceplate to equalize the charges.

But, if the bracket is isolated from the GPU (and the surrounding circuits on the card), then touching the bracket won't do anything to the card. Which can be a good thing. Because you won't damage anything. But then a potential difference between the graphics card and the motherboard (on which it is supposed to be installed) may remain. That can result in an ESD event at the moment the graphics card slides into the PCIe x16 slot.

So, howto avoid ESD on a new graphics card? (Besides leaving it into the box.)


texts: Making a momentary push-button switch activate a 5 VDC relay

texts:
I have a momentary push-button switch in an existing installation that I can hijack for a project. The project requires a 5 VDC relay to activate and the rest of the circuit is powered through there.

But how do I make a momentary push-button switch activate a relay?

I built a circuit like this in the Falstad circuit simulator.

The output is the collector of the NPN with the 1 kohm base. I connected this point to the negative terminal of the relay and the positive terminal is connected to Vcc (12 V). This doesn't work, because the relay coil pulls the collector up and breaks the circuit.

If I add another NPN with its base connected to the NPN with the 1 kohm base it pulls the PNP base down and the PNP will never activate.

Do note I'm a newbie, just a hobbyist here. Btw, I have no access to flipflops, diodes, etc. All I have are resistors and NPN/PNP and various capacitors and a few relays. I will have to drive 2 hours to buy other components if need be.


texts: Why doesn’t voltage drop to 0 when a capacitor becomes fully charged?

texts:
This is my understanding so far of what capacitors are and how they work, if it helps to answer my question at a level I can understand:

A capacitor is composed of two equally sized conductive plates with a dialectic (a insulator that can transmit electromagnetic force but blocks current flow) in between.

When a battery is connected hooked up to a non polarized capacitor, electrons will begin to propagate from the negative terminal of the battery to the plate it is connected to.

The uncharged particles on that plate will receive a surplus of electrons, causing that plate to become more negatively charged.

At the same time, valence electrons from the uncharged particles from the plate across the dialectic will propagate to the positive terminal of the battery, leaving that plate with a positive charge or deficiency in electrons compared to protons.

Current will stop propagating when the atoms on the plate connected to the negative terminal of the battery have accepted the maximum number of valence electrons they are able to hold and when the atoms on the plate connected to the positive terminal of the battery have lost the maximum number of valence electrons those atoms are able to give up. Or when the negative plate reaches its maximum negative charge and  the positive plate reaches its maximum positive charge.

When the battery is removed and replaced with a passive component, because electrons cannot propagate through the dialectic, they will flow In the reverse direction relative to the direction of current flow during charging, from the negatively charged plate around the circuit back to the positively charged plate to restore charge balance.

My question:

From the beginning of charging to when the capacitor is fully charged, current will gradually drop from its starting rate to 0 because, like I previously explained, the atoms on negatively charged plate will be able to accept less and less electrons as each individual atom’s valence orbit reaches its maximum capacity.

So, if electrons are at a stand still/not able to propagate across the supply throughout the wire into the negatively charged plate, how is it possible voltage can remain constant if voltage is directly proportional/created from electron propagation/current? Shouldn’t the voltage across the source and the voltage across the wire be 0 at this point? And why not/how is this possible?


texts:
A linear circuit is shown in the figure.

The elements in this circuit have the following values: R = 100 Ohms, R2 = 200 Ohms, R3 = 350 Ohms, V = 5V, and I = 0.004 A.

Determine the potentials of drops v_a and v_b across resistors R1 and R2 respectively.
Now let us determine if the answers you came up with satisfy the laws of physics.
(a) What is the power (in Watts) dissipated in resistor R1?
(b) What is the power (in Watts) dissipated in resistor R2?
(c) What is the power (in Watts) dissipated in resistor R3?
(d) What is the power (in Watts) coming out of the voltage source V?
(e) What is the power (in Watts) coming out of the current source I?

From the circuit I have:

\$-v_b + v_a + V = 0\$

\$v_b - V = v_a\$

\$i_1 = (v_b - V)/R_1\$

\$I + i_2 = i_1\$

\$(v_b - V)/R_1 = I + v_b/R_2\$

From this last equation I get \$v_b = 10.8\$ and hence \$v_a = 5.8\$.

However, apparently that is wrong. (And hence my answers to #2 were all wrong as well.) Why is that so? What might I be doing wrong?


texts: What's the typical distribution of fabric speed grades in produced dies?

texts: Let's say I produce 1000 FPGAs, what percentage of these 1000 FPGAs are considered super fast, fast, medium, and slow? Does it look like a normal distribution, exponential, linear, etc.? Does anyone have any data they can share or point me to regarding this?


texts: Understanding this circuit with op. amps

texts:
I'm studying electrical engineering and I've came to a problem, where I cannot proceed. It's a "simple" task, where we're talking about an inverting op.amp with 2 voltage sources, each 1V, while all resistors are 10k, except the one in the feedback, which is 20k.

I I know, that the solution is Uout = -7V, but how to get to this result?
By equations I've calculated, I've got result either -0.5 or -3V, but never -7. And also, I've simulated in LTSpice and got -7V.

Will appriciate all the help!

simulate this circuit – Schematic created using CircuitLab

Tidied up schematic for OP review. [Transistor]


texts: Are there datasheets for this dataflash memory?

texts: It's hard to read what is written on this dataflash memory but it looks like 25p80vg. I searched for datasheets and found some things similar to it, but couldn't find anything that matched it exactly. Are there datasheets for this?


texts: Will this Solar-Electric hybrid circuit work?

texts:
Would the circuit above works?

I'm trying to build a self sustaining solar powered Arduino controlled plant watering system. Since I'm using an electronic valve and not a pump, I'll assume it wouldn't need a lot of power.
Can the battery be used while being charged by the solar panel? Would the charger circuit use up the juice when it's not charging the battery?
I will be using this charger.


texts: How to figure out battery life of audio amplifier?

texts:
I have a design of an audio amplifier. It has some special features but basically it takes in an audio signal does some filtering, and amplifies it through a class D amplifier chip. The chip says it has a 1.7A max current draw, sound played will be music or some signals. I want to power it with 4 AA batteries.

My question is, what current do I use in a mAH/current equation to figure out how long my battery might last. It's not a constant 1.7A since the music played will determine output current.

Also, are there other special considerations for battery life of an audio amplifier?


texts: Double Peak Phenomenon in Transimpedance Amplifier Simulation

texts:
I'm simulating a transimpedance amplifier circuit in order to replicate a phenomenon that my team is experiencing. The phenomenon can be seen below in the image circled in red:

My photomultiplier here in the simulation is being triggered at 10 ns by the voltage source V1, and you can see in that big peak before the red circle, our signal is getting amplified by the amplifier. However, we're also getting a small peak, as shown in the circled red part. I don't understand why this is happening, but I know that it becomes more prominent as you reduce the feedback resistance, R1. Here's a view of it at 50 ohms:

If I increase the feedback resistance too high, the signal gets clipped, and I'm trying to avoid that. I don't think that this is necessarily an op-amp exclusive problem, as I see this issue using different op-amp models as well, but why is this occurring, and what can I do about it?

EDIT: In response to one of the replies, here is the output signal when the feedback resistance is 100 ohms:

Here, you can see clipping as it reaches 1.13 volts. This is the situation that my team is trying to avoid; rather than have the signal be clipped, we want a pulse, like how the previous images show (though without that second peak shown in red).

EDIT: As suggested, I performed a small signal analysis of my circuit by injecting a small 15 mA AC  current source (max current limit of the SiPM) into the circuit:

Thanks to a comment, I performed the initial analysis wrong by using an AC voltage source, so I ran it again with the current source. I chose the direction of the source based on how the current would flow through the SiPM (it seems that changing direction of the source just inverts the phase), and the DC trigger didn't seem to have a noticeable effect on the circuit (based on running it with/without the trigger). I see about 5 peaks in the graph, but what does it mean in regards to the circuit?

EDIT: Sorry that I didn't mention this earlier, but I'm using a model of the SensL MicroFJ-60035-TSV SiPM for my circuit.


texts: How do I solder a Sparkfun breakout board to a shield?

texts:
I need to solder some breakout boards onto an Arduino shield.  What's the general procedure to do this?  Do I solder it onto a header?  Do I need any other mechanical connection or hold-down?

For example, I would like solder this gyro sensor onto this aeroquad shield:

gyro sensor: http://www.aeroquadstore.com/ProductDetails.asp?ProductCode=SEN-09801

aeroquad shield: http://www.aeroquadstore.com/ProductDetails.asp?ProductCode=AQ2-000


texts: Is there an equation for the relationship between illuminance and the resistance of a light dependent resistor?

texts:
All I've seen on this is:

R = A.Ea.
where E – illumination (lux),
R – resistance (ohms) and
A, a – constants.
The value of ‘a’ depends on the CdS used and on the manufacturing process. Values usually range between 0.7 and 0.9".

But I'm not sure how to use this. Does anyone know of anything?


texts: How to use the RBO external interrupt to read PORTB (RB4 to RB7) and write the value on PORTA (A0 to A3)?


texts: Normal for WS2812B LED's to turn on immediately when powered?

texts: Is it normal for all the LED's on a programmable LED strip to turn on as soon as power is applied?   I have 3 strips of WS28182B's, and they're all behaving exactly the same way - the 300 LED's all go to white color, full brightness the instant 5V is connected to the red and white wires.  The green data wire is left open, but grounding it makes no difference.  Neither does a 10uf capacitor across the power leads.  I'm now having an argument with the vendor who claims this is normal behavior.  From everything I've seen and tried in the past, this is not normal, and these are defective strips.   Does anyone have info to the contrary?


texts: I want to DIY a double BiQuad antenna . But I find they are different from different web. As the picture first of below, the board under the antenna is flat, but the second has two orthogonal bend. I just want high dBi and use for  5.8G wireless image transmission. Which is better ?


texts: Reading output from "line-driver" hall-effect sensor

texts:
I am trying to control a 3 phase brushless dc motor with integrated hall-effect sensors.  I understand how to do this with your typical open-collector hall effects, however according to the manufacturer these are "line-driver" hall effect sensors.  I do not understand how to read them.

Instead of just having 1 output for each halleffect this motor appears to have 2.  I have hooked 12v to Vcc and Ground to ground and measured the output of both the + and - output of the halleffects.  There seems to be 3 possible outputs at each output ~6.86, ~5.8, ~ 5.  I have to be missing something right??

I have attached the very limited information the manufacturer has given me


texts:
so I had my original circuit looking like below:

simulate this circuit – Schematic created using CircuitLab

I was able to simplify it to look like as follows:

simulate this circuit

but now am stuck. I don't know where to go from there. This is a small signal model for an amplifier utilizing an npn bjt. I'm being asked to find vo/vsig and Rin. Any help please??


texts: how to detect error and restart microcontroller for embedded system with Esp 12 or Esp 32

texts:
one thing that make me confused is how the microcontroller notice the errors and restart by itself
let me give an example
we have cooler system with Esp 32 and temperature sensor,when temperature be Above 25 centigrade degrees cooler will work until temperature reduce to 25 degree .
all the thing will work in the loop .
for example after 1 week of work errors come to esp , how is possible that Esp notice the error and restart automatically for fixing the error .
i don't want restart the board manually


texts: In a short-circuit test where the secondary winding is short circuited, how come the primary voltage isn't zero (in real life) when it should ideally be zero?


texts:
I am using a PIC24FJ128GA010 and I need to make an oscillator choice. If I am not wrong, two main oscillator could be used 32KHz and 8 MHz.
1. Do I really need 32KHz oscillator?
2. Element 14 website shows many 8MHz but the Microchip website advice to make a clever choice.

Could you please help me for this choice.


texts:
I'm trying to design a BMS that allows for multiple larger packs to be connected together in parallel (say, multiple 4S LiFePO4 packs). Using an unconnected conventional BMS SOC there's obviously the risk of unregulated balance current between various voltage cells which could damage cells or the BMS.
I'm wondering if say, current is limited into the pack (at 0.3C for example) and a data connection is made between packs, and packs are top balanced like the cells are if this mitigates those risks?


texts: Are small valued capacitors effective in the device power input?

texts:
I am really confused with all of the ground bounce, decoupling, bypassing, filtering, resonance and ESR&ESL stuff.

What I currently understand is:

Ground bounce occurs when the (capacitive part of the) load trying to source (and at the same time IC trying to sink) the current which has a high enough  \$\dfrac{di}{dt}\$. Lead inductances of the package do not matter much, however other inductances of the traces which are bigger compared to the IC leads matter. That's why capacitor(s) are put as close as to the IC power pins to provide a spontaneous power supply that is close enough and have small path inductance enough to prevent ground bounce.
Decoupling is the job of the capacitor mentioned above. Also, it will bypass the noisy sub-circuit from the quiet sub-circuits by preventing high currents that have \$\dfrac{di}{dt}\$ to distribute to the other parts of the board.
Also, a decoupling capacitor will filter unwanted high or low frequency noise from the power supply by giving the noise a least inductance path to the ground.
Resonance frequency plot of the capacitor will show us how effective it is at a frequency.

My questions are:

If one uses 1nF, 100nF (both polyester film box type) and 10uF (electrolytic) through hole capacitors near the the power input of the PCB, like in the below layout, (s)he obviously won't be able to decouple the ICs that are far away, however will (s)he be able to suppress the noise coming from the power supply of the system? Is a 1nF, 10nF or 100nF capacitor effective for this job?
May be the same question as above. Is putting a 1nF, a 100nF and a 10uF capacitor on the power bus of a breadboard effective?
Can decoupling capacitors cause oscillations?

Below is a PCB I tried to lay out. It is an audio amp that is used in the buses so the +24V power supply input in the "input & output connector" is noisy. In the schematic I was given, there were lots of capacitors and an inductor (in both SMD and through-hole package, only one is populated). L1, C7, C8, C10, C9 are the components I am talking about. Are these capacitors effective by the means of first question? Also, do C10, L1 and C7 form an effective Pi filter?

Edit: Sorry, I had to remove the PCB and the schematic due to company policies. Oops!


texts: Frequency dependent resistor in real inductor (air coil)?

texts:
I tried to measure the resonance frequency of some multi layer air coils. Typical parameters are 0.6 mm copper wire, 3 to 8 layers, and diameter and height are approx 50 mm. I solder a 1 Ohm resistor to the coil and connect it the shortest way possible to a frequency generator. The output current saturates at low frequencies and the adjusted voltage drops, but I normalize accordingly.
When measured with an RLC-meter the coil has about \$L = 5\;\rm{mH}\$ and \$R = 5\;\Omega\$. Measuring \$C\$ does not make sense as the effect is much smaller than \$L\$. So I check the resonance by measuring the voltage over the \$R_0 = 1\;\Omega\$ resistor and the total circuit with a scope. I was expecting a behavior that you get from a simple equivalent circuit, i.e. \$L\$ in series with \$R\$ and \$C\$ parallel to both.

simulate this circuit – Schematic created using CircuitLab

So here is what I get

The small dashes are the data. The dotted lines are fits where I fix \$L\$ and \$R\$ and \$R_0\$ as measured from the LCR meter and allow only \$C\$ to vary. This does obviously not fit the data. The dashed line additionally has \$R\$ free to fit, but this doesn't work either, especially not for the 8 layer rectangular coil. The continuous line fits very well but it assumes the resistor \$R\$ to behave as
$$ R = R_\rm{const} + \omega  \;  r_\omega $$
i.e. a resistance changing linear with frequency. The parameters should be pretty far away for significant changes due to skin effect. Losses due to eddy currents are unlikely as well (I checked with and without a big aluminum sheet near by: no difference).

So what am I actually measuring?

Edit
Is it radiating? Long wave radio would be up to 300 kHz.


texts: Theoretically determining Q for an inductor

texts:
I've recently been looking into passive filter design a little more closely than my classes have gone into, so far as actual component selection and design are concerned. The biggest sticking point for me has been understanding how to gauge Q, specifically for hand wound toroidal inductors.

I understand Q is the reactance over the resistance, and is only valid for a specific frequency. The reactance is a fairly simple equation for a toroid, but I can't seem to find any discussion of how to determine R. All sites that I've found talking about inductors and Q factor only mention that it's a complicated value that has to take into account skin depth, eddy currents and hysteresis losses, but there is never any way given to estimate it nor is any method discussed so far as I've seen. All the responses here to similar questions unilaterally say to refer to the datasheet, but with a hand wound inductor, those are in short supply.

Furthermore, how much Q do I need for an inductor in a filter? From what I've seen higher Q leads to more efficiency, but how much Q is enough to provide acceptable losses?


texts: Better displacement finder? Lasers/Inertial Sensors

texts:
I've seen laser rpm measurement devices. But can it be used the find displacement/distance moved for object when attached to it?
I know taking rpm of wheel and multiplying by circumference would give it, but is there any way we can find distance moved when the object slides?
For example, a model roller-coaster, when its moves what is the best way to find its displacement? I find inertial sensors complex and less feasible.


texts: Use 110/120V Outlets, Receptacles and Switches in 220/240V Country

texts:
The outlets used normally in that country are exactly the same as what is used here in the U.S. - the only difference is they're 220-240V.

I do notice that the construction and connectors seem to be exactly the same - ditto with the amount, thiknesses, etc of the copper material, connectors, etc used... Even the AWG sizing of the wires are the same for the branch circuits.

Reason I want to use U.S. based 110/120V fixtures is they seem to be better built, longer lasting than the often China/Taiwan/Thailand sourced fixtures available in that country.

Is it okay to use U.S. type wall outlets, receptacles/fixtures and switches designed for 110/220V operation in a country where 220-240V is standard?


texts: Difference between two equal valve tubes

texts: Is there any difference in "Plate Voltage"/"Plate Current" curve between two real vacuum tubes 12ax7?


texts: How to unsolder a flow soldered board with a large ground plane

texts: Hi I have a flow soldered board with some very big capacitors on it. I was hoping to get them off but when I looked it has a very large ground plane. I was unable to get these capacitors off because it heated up the surrounding board. When I attempted to pull them off even after the solder looked like it was melted and I sucked it off. Once i did this and pulled on the cap it pulled the leads out of the cap. Do you guys have any ideas thanks


texts: I have a microphone with a XLR output and a XLR to PL cable. I don't get from it any signal on my PC. Can I test with a DMM the microphone and the cable  in order to locate the problem?


texts: How to deduce number of possible states for an adder

texts:
If my calculation is correct, a 4-bit adder has 65536 states which is exactly 2¹⁶. Where does this number come from? It seems there should be some theoretical background why this number is exactly 2¹⁶. Is it true, according to a general formula or is my model faulty?

My adder looks according to the following specification.

MODULE bit-adder (in1, in2, cin)
VAR
    sum : boolean;
    cout : boolean;
ASSIGN
    next (sum) := (in1 xor in2) xor cin;
    next (cout) := (in1 & in2) | ((in1 | in2) & cin);
MODULE adder (in1, in2)
VAR
    bit0 : bit-adder (in1[0], in2[0], FALSE);
    bit1 : bit-adder (in1[1], in2[1], bit0.cout);
    bit2 : bit-adder (in1[2], in2[2], bit1.cout);
    bit3 : bit-adder (in1[3], in2[3], bit2.cout);
DEFINE
    sum0 := bit0.sum;
    sum1 := bit1.sum;
    sum2 := bit2.sum;
    sum3 := bit3.sum;
    overflow := bit3.cout;

It is the number of states from my main module that is reported. If I don't include the main module then the number of states is 1.

MODULE main

VAR
    in1 : array 0 .. 3 of boolean;
    in2 : array 0 .. 3 of boolean;
    a : adder (in1, in2);
ASSIGN
    next (in1[0]) := in1[0];
    next (in1[1]) := in1[1];
    next (in1[2]) := in1[2];
    next (in1[3]) := in1[3];
    next (in2[0]) := in2[0];
    next (in2[1]) := in2[1];
    next (in2[2]) := in2[2];
    next (in2[3]) := in2[3];
DEFINE
    op1 := toint (in1[0]) + 2 * toint (in1[1]) + 4 * toint (in1[2]) + 8 * toint
    (in1[3]);
    op2 := toint (in2[0]) + 2 * toint (in2[1]) + 4 * toint (in2[2]) + 8 * toint
    (in2[3]);
    sum := toint (a.sum0) + 2 * toint (a.sum1) + 4 * toint (a.sum2) + 8 * toint
    (a.sum3) + 16 * toint (a.overflow);

    LTLSPEC F op1 + op2 = sum

It is when I add the row a : adder (in1, in2); that the number of states increases from 2^8 to 2^16. So it is something with the model checker and the main module.


texts: Understanding \$ j \omega \$ axis in transfer function

texts:
I understand the transfer function up to the point of \$ H(\omega) = \lvert H(\omega) \rvert \angle H(\omega) \$ where the magnitude and phase are decoupled into two separate functions, equivalent of saying \$ H(\omega) = { Y_0 \over X_0} \cdot e^{j(\angle y- \angle x \; \text {in radian})}  \$.  I can understand this in polar equation on the complex plan.
Then all of a sudden the transfer function jumps into \$ H(j\omega) = \lvert H(j\omega) \rvert \angle H(j\omega) \$ swapping every \$ \omega \$ with \$ j\omega \$. I'm lost. I searched here and there but I found no explanation on how and why \$ j \$ axis is transformed into \$ j\omega \$ axis, or why \$ j\omega \$ axis is added to the complex plane as a third axis if it's a different axis.

Does \$ j\omega \$ axis mean \$ j \$ axis multiplied by a frequency magnitude of \$ \omega  \$? If so what does it mean and why an axis has a magnitude? That make no sense to me whatsoever to give magnitude to an axis as axis should only be directional (imagine if someone ask me to graph a line on the x-2y axis instead of a x-y axis)
Or, is \$ j\omega \$ an entirely different axis from \$ j \$ axis - meaning a number on \$ j\omega \$ axis has no relation to a number on \$ j \$ axis? If that's the case could someone help explain what are their difference and when should I use which?
Since \$ \omega \$ is the angular velocity, could \$ j \omega \$ represent the rotational axis, a third axis that is orthogonal to \$ j \$ axis and the real axis like a cross product sort of thing?

[EDIT]
Just to clarify my thought process here. If I have 2D plane with two axis, x and y, I can define a value \$ z = ax + by \$, where a is a position on the x-axis and b is a position on the y-axis. We can call the value z on the x,y plane. We are not going to call it x,by or x,\$ \omega y\$ plane.
Same logic goes here where the complex frequency s is a value on \$ \sigma \$ or real axis and on \$ j \$ imaginary axis. So a value of s is \$ s = a\sigma + bj\$, where a and b are positions on the real and imaginary axis. So s is on \$ \sigma,j \$ plane, not \$ \sigma,\omega j \$ plane. What is \$ j \omega \$ axis?


texts: What is the current carrying capacity of a single stripboard track?

texts:
A stripboard track's current carrying capacity  can be increased by using tracks in parallel, tinning it with solder or soldering tinned copper wire onto it, etc. but what is the current carrying capacity of a one track as it comes and for how long, without causing unwanted change in the circuits reliability?

There is some info about temperature rise with current in a pdf at Printed Circuit Board Track or Trace Current Carrying Capacity per mil std 275 and an image at Extract from VEROBOARD MANUAL 1960 which implies maybe 0.5 to 1.0 A max but they're not very specific.


texts:
I have to offer a "FG" connection for the product  I am designing.

The product is isolated in many parts, so, which part of the circuit should i connect the "FG" to?

Below is rough scatch of the block diagram of each isolated parts of the product


texts: Is it possible to read/pair ESC (2.4Gz?) signal

texts:
I'm new to ESC, sorry if this is a noob question, is it possible to somehow pair or read the battery level from an ESC?

What I'm looking for is to read the battery level from an ESC electric skateboard so I can show that on an App.

This is the board:
https://cdn.shopify.com/s/files/1/2096/3333/products/MR30_to_bullet_adaptor_for_ESC_V2_to_Motors_V1_e4017283-957d-44cc-82e5-536dcbfda249_1800x1800.jpg?v=1527698368

used with this sort of RC:
https://www.aliexpress.com/item/2-4Ghz-Remote-Controller-With-Receiver-Universal-for-All-ESC-Electric-Skateboard-Longboard-Skate-Board-Scooter/32817830821.html


texts: Understanding input voltage noise of AD8232

texts:
AD8232 has a built-in instrumentation amplifier with a fixed gain of 100. I am interested in using this device for amplifying EEG signals. Page 3 of the linked datasheet describes input voltage noise of the in-amp:

I'm not sure how to interpret these figures. Does Vpp-noise correspond to the actual input noise at gain=100, or should I multiply these values by a factor of 100?


texts: Low component count isolated contact closure without power on the remote side

texts:
Other answers here show a common way to allow a microcontroller to cause a contact closure (button press) within another device in an isolated fashion: use an optoisolator.

I have the reverse problem. I've got a distant unpowered button, and I want to know when it is pressed. I want to know this without risk of damaging my µC due to badness \$\gg V_{DD}\$ on the long wires running back to that button. If you want a mental model of the application, think of it as an electronic doorbell.

I already know how to sense the remote button press in an unprotected fashion:

I also know about the standard method of microcontroller input protection. (Zeners, GDTs, TVSes, MOVs, current-limiting resistors...) I was just hoping to be able to buy a 2- or 3- terminal blob with some combination of those components arranged, qualified, and quantified. I even dared hope that I could find a gang of N of them in a "firewall IC" for under $10. (4 ≤ N ≤ 10) I want the effect of going to the littelfuse.com homepage and saying, "Yes, I'll take all of that, and can you tie it up and put a bow on it for me, please?" Littelfuse seems to prefer that I buy a pile of discrete parts instead.

An optoisolator won't work here because it requires that I either power the remote end with a separate isolated power supply or give up some isolation by powering the LED side of the isolator from the microcontroller's supply.

I want it to work with just a raw contact closure. If there's any voltage coming from the button, it's either an application error that I wish to protect against (e.g. active sender rather than a dumb button) or badness per above.

The Infineon ISO1I813T is the closest thing I've found so far:

The problem is how many external components it requires. With the same number of components, I think I can probably come close to its effect with the standard method. The only thing I lose is isolation, and I'm not sure I really need that. All I'm certain I need is protection.

As a provisional goal, let's try to make it withstand at least an indirectly-coupled lightning strike. Somewhere between that and EMP-proof would be nice. :)


texts: How to use arduino control an ESC and flash?

texts:
Basically, I want to use PWM wave or something alike from Arduino to directly control the speed of a brushless motor through an ESC.

I saw an example on the Arduino Brushless Motor Control Tutorial | ESC | BLDC by Dejan . However, I saw some other people mention about flash ESC such as  Flash ESCs with ANY Arduino!

But I was confused about why they needed to flash the ESC?
Can I just control the speed of the motor by sending PWM wave to ESC directly from arduino? I wanted to use BLHeli ESC.


texts:
I just got a 3s Lipo battery. Lipo battery has a 4 pin connector to plug it into charger or voltage checker. But I don't want to buy a lipo voltage checker, I want to make it. But I have a problem.

Let's say a=GND b=1st cell c=2nd cell d=3rd cell
so if I read voltage from b it's b, But if I read the voltage from c it is c=b+c , If i read voltage from d it's d=c+d.

I have lm339 IC , and I need b , c-b and d-c.

How to substract voltage?

Thank you for ANSWERS!


texts: Conceptual understanding of semiconductors - definition of holes

texts:
I am studying semiconductors and I have a very basic question on the definition of a hole. Why do we add up the contributions of holes and electrons when calculating the current density ( J = (n.q.un + p.q.up).E )? Aren't they equivalent?  I mean, if the hole is the absence of an electron, what is the reason this equation holds? Wouldn't we be calculating a value of J that is above its real value?

Thank you


texts: Trying to damp transformer output ringing of Flyback Converter when primary FET turns on

texts:
I have a flyback regulator with some output ringing spike problems. It is a 70-130V input with 6V regulated output and 75V unregulated output based on the LM5021 flyback IC.
When going from no load to 3W load on the regulated 6V output, the transformer output pin on the 75V output (basically the voltage across the output rectifier) has a huge negative spike. The load transient momentarily causes the duty cycle to jump to about 70%. This negative spike only happens during transient load on the 6V. I haven't been able to test high load on both outputs yet so maybe it will happen there as well. Right now the spike is getting dangerously close to the limit of my 600V output rectifier.
The yellow trace is the voltage across the output rectifier and the blue trace is the gate drive of the switching FET. The transformer doesn't like being put back into charging state while in continuous mode it seems. I have since added 500pF with 200Ω across the output rectifier and it helped a little bit by getting rid of higher frequency ringing but not the main negative going spike.

Here is the output stage. The 6V feeds back to an opto feedback network. The 18V is used to self power the power supply. I measured about 16μH of leakage inductance in the transformer. It is meant to operate in continuous mode when up to 70W is drawn from the 75V output. When there is little to no load it will run DCM and do pulse skipping.
I would really love to figure out how to knock down that negative voltage transient. Maybe I should just go to a 1kV output diode. With 80V on the primary side (afraid to go to full 130V input yet) and 75V on the output I don't understand how I get 400V spikes across the output diode. Transformer step-down is 36:25 for the 75V output and 36:2 on the regulated 6V output.
Thanks for your help!

Here is a more complete representative schematic of this supply from my simulation file:


texts: Open Neutral Service Detector/Disconnector

texts:
Who has built an open neutral service detector that can disable the 120v circuits when the neutral opens accidentally (in the USA 120/240v split ac system)?

Remember these words by Mike Holt: https://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/DangerofOpenServiceNeutral~20020816.htm

"If the grounded (neutral) service conductor is opened or not provided at all, objectionable neutral current will flow on metal parts of the electrical system and dangerous voltage will be present on the metal parts providing the potential for electric shock."

I read that this has been developed in Africa where the neutral wires were often stolen. Also someone at Thailand proposed this design.

https://www.thaivisa.com/forum/topic/457002-the-hazard-of-an-open-circuit-neutral/

"How it works.
Consider normal operation (top diagram), the neutral is at or near ground potential so no current flows down the ground stake and the RCD remains in balance. Open the neutral (second diagram), now there is no current in the neutral leg of the RCD and it opens protecting your supply. Reverse phase and neutral (third diagram) and we have a similar effect, again the RCD is imbalanced and trips."

How do you implement it in the USA 120/240v split power ac system? By which if the service neutral is open or disconnected, the circuit would be disconnected as well.


texts:
I have a group of sensors the nominally output 2.5V but if they come in contact with a magnet they'll increase slightly or decrease slightly based on the polarity (north/south pole).

These sensors have a decent range but they're pretty narrow in scope, so as a result I've aligned a number of them side by side.

My issue now is that I have 6 of them, and I don't want to spend 6 analogue in pins if I can help it. Ideally I'd like to build a circuit that ultimately reports the greatest difference from the nominal 2.5V between all 6 of the sensors.

For example, let's say we begin in a neutral environment -- no magnets are present. All sensors will read 2.5V and none of them really "win" the output pin. However, as I bring a magnet closer to the line of sensors, the one closest will read let's say 2.9V, and it's neighbour will read 2.7V. Between these two the 2.9V will "win" the output pin because it has the greatest difference from the nominal 2.5V. So I'd like to see either 2.9V on the output pin of this circuit, or 0.4V (the difference). Doesn't really matter which since the rest can be handled by software.

I'm thinking a summer op-amp might be the right answer here but I was wondering if you guys have any other suggestions. Thanks!

EDIT: To clarify, I don't care which sensor "wins" I just want to know if ANY sensors change from 2.5V, what's the greatest change?

EDIT2: There's only one magnet being sensed here so if one sensor reads negative then they all will. No need to account for some being +0.4V while another is -0.4v.


texts: Proof that Delta and Y transformer have the same power?

texts:
I'm trying to proove that a Delta and Y transformer both have the same power. Somewhere I must get wrong in my process...

I have a reading in voltage and current in a Star transformer: 600 V line-line (347 line-ground) and 5 A going through each  resistances.

I obtain my power for 1 phase like this:

P1=U*I/square(3)

U=600V
I=5A

So P1 (for one phase) is 1734 W, approximatively 5 kw for all 3 phases.

Now I want to switch this transformer to a delta configuration. I calculate resistance: V/I = R -> 347V/5A = 69.4 ohms

Ok now I switch to the Delta configuration and find the current in one phase:
600V/69.4ohm=8.64A in each resistance (line-line current)

So I need to multiply by square(3) to obtain current line-ground. Let's call this current I

I= 8.646*sqrt(3) = 14.95A

So now the power in one phase is

P2 = I*U/square(3) = 14.95*600/square(3)

So P2 is 3*P1

Which means I have 3 times the power in the Delta configuration vs what I had with star configuration...

I've been banging my head on this for hours, checking with friends, I do not see where I go wrong...

So here I'm lost: Is my calculation incorrect OR am I wrong and Delta configuration power is 3 times the power from Star?

Here is a picture of my calculation, it shows that the Delta has triple power...


texts:
I need a 120 to 24 volt transformer.  The one I bought says 24 Vac secondary
Just below that it say 40VA output.

Is this a 24 volt transformer or a 40 volt output


texts: Audio Potentiometer with external way to know position

texts:
At the moment I am trying to create an audio circuit, in which I need to reduce an audio signal from 2 V into a variable output of 0,030 V to 0,350 V. For that I think a Logarithmic Pot will do the trick, but I don't know how to get it to 0,350 V first.

But here another thing. I plan to enclosed the circuit in a box and I don't want to have potentiometer inside of it which I can precisely control, i.e. let's say the box has a hole so you can reach the potentiometer inside a rotate accordingly with a screwdriver, there's no real way to say: "ok I move it a quarter to the right or to the left. Therefore I would like to have a switch, digital, a hex switch I don't know I have no idea, that I can externally select let's say letter B and that means that the voltage will be decrease 20 dB, or when I select letter G the voltage will decrease 40 dB.

I hope I have explained myself, I'm a little new to this so sorry if I am mistaken or misunderstood something.

Thanks in advance for your help.

=)


texts:
I currently have a 1Mb Parallel SRAM chip in a DIP-32 package. Putting that on a board is causing me all kinds of routing and space headaches. I know that there are nice 8 pin spi or i2c chips that have that capacity, but it seems that they are all eeproms or flash memory. I plan to overwrite data quite frequently and I know that most persistent storage has write limits and (I would assume) slightly slower speeds than vanilla SRAM. If I had an eeprom or something I would be performing a chip erase on each startup, and don't want a part that will wear out too soon. My attempts to find a suitable part on mouser or digikey has turned up nothing, but I am not sure what I am looking for.

Is there any kind of volatile storage that can be accessed quickly over some serial protocol? My MCU is running at 5v supply and logic, but I am willing to shift voltage down if necessary.


texts: Common Mode Voltage Range with Negative Feedback

texts: In section 3.1 of AN21 from Apex Microtechnology it mentions to make sure to accomodate the common mode voltage requirements. But does the common mode voltage range mean anything if one of the inputs is grounded and there is negative feedback? Negative feedback guarantees that now both my positive and negative input will always be at ground. This means I could have an input voltage greater than the supply voltages - since no matter what the input voltage is, the negative and positive inputs are always 0V (which is less than the positive supply voltage). Does this mean for example in the case shown below, I could apply an input voltage of greater than 430V since negative feedback ensures the input terminals of the op-amp will always be 0?


texts: Should routing traces be wider than top layer soldering pad?

texts: In one of my PCB design, the microprocessor soldering leg pad size are .254mm x 1.4mm while the ground(GND) routing trace is .4mm thick. I'm trying to figure out is it safe to route the .4mm thick trace to the .254mm soldering leg pad of the microprocessor?


texts: Problems with understanding memory map STM32F446RE

texts:
I have a problem with the understanding of the memory map of the STM32F446RE.

In the Datasheet is the system memory (0x1FFF0000 - 0x1FFF7A0F) 30,51kb big.

But in the AN2606  the system memory is only 29kb big.                            But why?

I calculated this way: (kibibyte refers to the answer from Elliot Anderson)
                                                                                Datasheet:

AN2606:

Difference:

So if my calculation is correct, what is in the other 1,51kbyte or 2,247 kbyte?

Update:
For those who are interested, I got an answer from ST.

The whole caluclation is in kB --> 1024Byte

The flash memory has an information block, which contains the option bytes, so the calculation doesn't add up.


texts: Threaded alternative to MMCX connectors which mates to RG-316/U

texts:
I'm currently in the process of redesigning the RF section of a communications system for a cube satellite. There are two PCBs in this system: one containing the down/up converters and modem, and another with the spring loaded dipole antennas, antenna deployment system, LNA, and PA.

The original design used MMCX connectors and two short (~2 inch) runs of RG-316/U (like RG-147/U but made of Teflon and slightly thinner) to connect the TX and RX paths to the LNA and PA, respectively.

My only concern is that MMCX is a push-on connector, which I'm worried might pop out during launch from vibration. Typical pogo oscillations range between 5 and 100 Hz and can be around 1 G both longitudinally and laterally.

I'm probably just being paranoid, but I thought I'd ask in case there's a better alternative. Is there a standard coaxial connector that's similar in size to MCX or MMCX but threaded? My google search isn't turning up anything.


texts: activity led in an ir transmitter circuit

texts:
Using a raspberry pi. I have an ir led transmitter. The attached diagram shows the circuit. I would like to add a low power coloured activity led that shows the circuit is transmitting.

Where should the "activity" led be in the circuit? To support its power consumption which resistor do I change?


texts: Actual life expectancy of COTS power supplies

texts: Can anyone shed some light on what the actual expected lifetime of a commercial off-the-shelf power supply would be?  I've seen the unbelievable MTBF numbers given in power supply datasheets, and found out fairly quickly that they're a bit of a scam; they don't refer to the actual “mean time between failures” of the power supplies, but are only the inverse of the failure rate early in the life of the power supplies (at the bottom of the bath-tub curve).  What would be more useful to know is the time at which the failure rate starts to rise significantly (and hence “MTBF” has fallen to something meaningful), or maybe the time at which 50% of the power supplies could be expected to have failed.


texts: How can we increase the passband gain in a Sallen-Key type low pass / high pass filter, preferably without using additional op-amps.


texts: Finding SNR and SNDR/SINAD from FFT of ADC

texts:
I have a question about the FFT spectrum of an ADC output

I understand SFDR you can measure the difference between the fundamental and the next biggest spur/harmonic.

But how do you find SNDR from the plot? Can I simply just measure the fundamental to noise-floor differene?
Similarly, how do I find SNR?


texts: With an extra flimsy cable length, the pump works...?

texts:
I have a 12V mattress pump that plugs into the car lighter socket.
One day I had the need to use it in the house, so the first time, in the urge, I grab an old 12V adapter, strip the cables of the pump, use some crocodile connectors to hook it to the adapter and here we go, mattress inflated
A little later I replaced the temporary crocodile connections with a clean pair of male/female jack connectors.
When pluging the circuit, the pump goes into intermittent bursts. As if the current was discontinued
So to recap:
12V TO flimsy crocodile cable TO pump => The pump works perfectly

12V DIRECTLY TO pump => The pump goes into intermittent bursts / disfunctional

I even made a video to showcase the issue - https://youtu.be/s5DjFHVJ2PU
I need help to understand and hopefully fix it!
I've been asking around, few handy mates, and even the electrical shop, 3 dudes there, no-one has been able to give me a lead...
They tried to replace the cable with resistances and capacitors but in vain.
Myself I tried different amperage of adapters, 1.5A, 2A & 3.5A. The result is a less powerful bursting mode with faster frequency of bursts on a lower aperage (see video).
In the despair, I've embedded the crocodile cable in the montage (shameless!), but at next use it did melt at the base of the crocodile jaw.

Idea ideas?
Happy to try multiple montage or measure anything to help figure it out.
I want to understand.
EDIT: On a demand, I tried to connect the small section of cable without the connectors (crocs) and the small copper thread are burning live, but the engine run perfectly! - https://youtu.be/WqIXVPMBFFg


texts:
I am a beginning hobbyist when it comes to electronics. I have read lots of theory but I only have a little bit of hands on experience.  I would like to build an 8x8x8 LED cube and I came up with this circuit, which I designed myself, to control all of the LEDS.

Can I get feedback on if there are any potential problems in the circuit? Will it sufficiently be able to handle the power that it is expected to draw. I expect to be able to control the input pins via an arduino. At first I had resistors in the circuit, but removed them because I believe the darlington's can handle the current without resistors.


texts: Just as a resistor is denoted by symbol R, an inductor with L, are there any representations for ICs, transistors?


texts:
I'm not generally confused by Electronic Engineering, but Nor and Xor are the Gate expressions that like to break that Rule.
I can't find proper answers to this question, as they are either:
Too Complex. Or too Uninformative.

No and Yes, I and O are quite simple, but i stumbled across the two extra expressions I've never heard of, Nor and Xor.
I'm quite new to this kind of stuff, so Nor and Xor are also new, and quite confusing.
Some clarification on the uses of Nor and Xor would be appreciated.


texts:
I want to program some PIC micro simultaneously using single same port. There is no problem in programming but when process is finished, feedback command that say "done! its programmed" cause conflict in receiver. In the other words, I want to able check each micro separately and this is my challenge.

with diodes I can separate send/receive path and check that finish programming command. but I don't know what is the type and value of this feedback command.

can you help me in this case or give better suggestion?
Thank you all,


texts:
I have two theoretical question about my circuit (that I have tested with a breadboard and it works, but I want to understand better some design choices):

1) As far the flyback diode is concerned, I have at my disposal 1N4007 high voltage diodes, that can be good because a 10x reverse voltage is suggested in these applications, or 1N5819 shottky diodes, that can be also good for the short reverse recovery time. The motor work at 12V, absorbing 5A. Between these two, what should be the best choice?

2) I have to determine the maximum frequency that I can use to drive my circuit, allowing the MOSFET to turn on and off completely without producing additional heat. The PWM circuit first goes into an ULN2803 darlington array, and then into an IRF9540 power mosfet.
Considering the delay related to the two components, how to determine such a frequency? (I'm interested in how to compute the theoretical value, but working with a 25Khz PWM I shouldn't have problems, right?)


texts: Charging my cellphone with a 18V DC source

texts:
I have received a 18V 2.5W photovoltaic panel and want to use it to either charge a cellphone (or even two at the same time) or power some Arduino projects. In both cases I need a 5V source, but mine is said 18V.

If I understand charging a device well, it is important that the source's voltage doesn't exceed the device charging recommendations, which are usually 5V, but the opposite is no problem.

How can I best make sure I get 5 Volts ?

Under the ideas I have in order to achieve that there are :

Using a diode in order to subtract a constant amount of voltage util there are only 5V left, but it seems to me that's a very bad idea since if a cloud covers the sun, I would get less than the initial 5V, which is not dangerous, but unfortunate.
Using some resistors (able to withstand 2.5W), but that would mean that I also need to know the resistance of my cellphone/Arduino project etc. in order to make a voltage divider... And on holiday I'm not very likely to have a multimeter in range... And it may be unfortunate to dissipate so much energy though a resistance.
Using a charger bought on the market, but I assume they won't do the job since they are usually designed to be used in a range from 110V to 220V. (Secondary question : how do chargers actually convert voltage ?)
Look for another solar panel :)

Thank you very much in advance for your answers.


texts:
So my problem is that I need to wire up a 5 pin LED switch to a motor and a car battery. Seems easy enough... But I need the LED to be on at all times. That is the bit I'm getting stuck with.

Now if you look at the picture I have wired 2 & 4 together, then 1 to the negative on the battery and 5 to the positive on the battery. (I have not done anything to 3) Now this makes the light constantly on. But how do I connect the motor to this so when I press the button the light is still on and the motor works? Is it even possible? also can you dumb it down with any technical terms as I am not an expert.


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I am working on a small project where I need to convert 220v AC to 5v DC with at least 100mA current. I am currently using Hi-Link's converter to achieve the goal and it's working great.

I am looking to use something that's much smaller than this. I found that there are some rectification ICs like MB10F which are able to achieve a similar goal and are substantially smaller. However, their voltage/current output don't seem to match mine.

I wanted to know if anyone is aware of an IC that matches this requirement. It would be great if you could point me in the right direction, or to websites where I can run queries such as these. I tried Mouser but I couldn't use their interface to achieve my goal. How do you generally find ICs like these?


texts: Short the circuit of a voltage controlled voltage source when finding out the v(t) for \$t>0\$

texts:
Question

Find v(t) for t<0 and t>0 in the circuit below.

Solution

My Question

Why we can see the voltage controlled voltage source as a shorted circuit when finding the v(t) for \$t>0\$? [Circuit (b)]

Thank you for your attention.


texts: Attempting to switch on and off a 4.5v solenoid with a transistor. using push button to control input

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I have a very simple setup powered by a 9v battery.

The lock solenoid when connected directly to the battery works great.

I have built a test circuit using a push button and a transistor in an attempt to make it so that when I press the button down the lock solenoid will power up. This circuit works fine with an LED, but does nothing at all when I swap the led for the lock solenoid. I have tested this with a dc motor and lock solenoid. Both the motor and solenoid are 4.5v and work when directly connected to the battery, but not when replacing the led in the circuit. I will attach some photos of the circuit. I have been messing with this for days with no progress. My ultimate goal is to control this solenoid with an Arduino nano, but I could not get that working so I am trying to get it working with the push button acting as the nano i/o signal before I move further with the micro controller.

Any advise at all would be appreciated, I am still very new to all this.

Circuit Photos Attached Below


texts: what would be the most suitable components to replace some relays?

texts: I'm working on an electronic product based on a microcontroller that must be able to control a series of actuators: 230V AC motors ON/OFF, 24V DC motors ON/OFF, 80V/20A heating element ON/OFF. The obvious way would be to use relays (in combination with optocouplers perhaps), but they have the downside of having a short life cycle. My product must have a +10 years lifetime, so what the best way to replace the relays in this design and still have galvanic isolation?


texts: diodes blow with no load on full wave bridge rectifier

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I have built what I thought is a simple first stage for a power supply consisting of only the full wave bridge rectifier (made up of individual 3A SMD diodes) and bulk capacitance.

The moment I apply power through the transformer my diodes blow. I've checked that I haven't installed any diodes back to front. The transformer can output a maximum of 4.81A but I apply power to the circuit with no load. I'm not planning to exceed the 3A limit in my final solution.

The basic schematic for the circuit is as follows.

What on earth could be the problem? Is this caused by the initial charging of the capacitors? I've checked that the board also has no short circuits between the positive and the ground rails.

Update
two circuits with same results:
Circuit 1 - total capacitance: 6580µF (made up of 14 470µF electrolytic through hole capacitors in parallel)
Circuit 2 - total capacitance: 2820µF (made up of 6 470µF electrolytic through hole capacitors in parallel)
8 diodes making up two full wave bridge rectifiers are B340LA SMD 3A diodes each (http://www.farnell.com/datasheets/639175.pdf)
All of the above fed with a single toroidal transformer with two secondary windings of 18V/80VA each. Single secondary winding tested in each case with both having the same result (fire coming out of the diodes which are then failed short circuit).


texts: Using a terminal GND or VCC for multiple boards

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If I have a screw terminal block like in the picture below, is it normal practice to use one of the six connections for GND towards multiple external boards?

E.g. I wrap three wires into the rightmost connection and each of the three wires go to a separate board?
(and likewise for VCC)?

Are there disadvantages to such method? It saves a lot of terminal blocks in my case.


texts: I'd like to make a Led that lights up by solar panel

texts: I'd like to make a solar panel that lights up an LED, not by charging a battery to power the LED, just live energy it is getting from the sun. I'm a real noob and need some advice. What panels should I pick, what specifications? I would like to make this work quite long but be easy to make. It's a normal single 2-3v (red,...,white) 5mm led that I'm thinking about


texts: What happens at hardware level when we feed a code?

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I wanted to know what hardware is installed in 8051 such that whenever i write a program it accepts it and execute it.
My query is what happens at the hardware level whenever i feed a program to 8051.


texts: What is the largest electrical connector in the world?

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I know there are some pretty big ones for undersea cables (as seen below and described here), but what else is out there?
The MacArtney 11kV, 400A wet mate connector:


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I would like to know why I can not match Littlefuse chart with general rule of picking fuse which is  125% of peak current of the system. (I know there is more about fuse such as voltage, temp, AWG.)
When I look at the Littlefuse Average Time Current Curves chart the fuse I need is around Nom Current.
Lets take an example: VNom= 12V DC Vmax =  13V DC  INom= 2.5A  Irush = 3A. Fuse should blow on any current over 3.25A (20AWG cable used).
As you can see in below image Red line is close 3A ir 3.5A. But the 125% *3A = 3.75A ~ 4A.

Littlefuse datasheet.